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Ichnology of a Pennsylvanian Equatorial Tidal Flat

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Systematic Ichnology, continued

Ichnogenus Nereites MacLeay in Murchison, 1839

Discussion--Nereites has been the subject of a continuous controversy regarding its relationship with other forms, particularly Neonereites Seilacher, 1960, and Scalarituba Weller, 1899. Some authors have argued that these three ichnotaxa represent preservational variants of the same form (e.g., Seilacher and Meischner, 1965; Chamberlain, 1971; D'Alessandro and Bromley, 1987; Rindsberg, 1994; Uchman, 1995), while others retained them as separate ichnogenera (e.g., Hakes, 1976; Fillion and Pickerill, 1990; Pickerill, 1991; Crimes and McCall, 1995). Chamberlain (1971) demonstrated that a single specimen is preserved as hypichnial biserially arranged lobes or pustules (Neonereites biserialis-like) and an epichnial median furrow with lobes on both sides (Scalarituba missouriensis, Nereites isp., and Neonereites uniserialis-like). Recently, Uchman (1995) discussed this problem in detail, stressing the importance of a central tunnel surrounded by a zone of reworked lithology as a diagnostic feature. He concluded that the type of preservation cannot be regarded as an ichnotaxobase at the ichnogeneric level, and he suggested that Neonereites and Scalarituba should be considered as junior synonyms of Nereites. Other ichnogenera synonymized with Nereites are Myrianites, Nereograpsus, Phyllodicites, Maldanidopsis, Delesserites, and Paleohelminthoida (Hantzschel, 1975; D'Alessandro and Bromley, 1987; Uchman, 1995). The ichnotaxonomic status of Radionereites Gregory, 1969, is somewhat problematic. According to Gregory (1969), Radionereites differs from Nereites by occurring in radiating clusters. Because the internal structure of Radionereites is identical to that of Nereites, it probably should be included in this ichnogenus, perhaps as a distinctive ichnospecies. Until a comprehensive review of all the ichnospecies of Nereites and similar forms is undertaken, this problem will remain unsolved.

Partial reviews and descriptions of some ichnospecies of Nereites were presented by Benton (1982), Crimes and McCall (1995), and Orr and Pickerill (1995). Uchman (1995) provided an extensive synonymy of Nereites, suggesting that accessory preservational features can be used to distinguish among different ichnospecies. Additionally, he proposed that ichnospecies formerly included in Neonereites (N. uniserialis, N. biserialis, and N. multiserialis) are better considered as ichnosubspecies of Nereites missouriensis. Uchman (1995) also placed Helminthoida irregularis Schafhäutl, 1851, in Nereites as a separate ichnospecies (N. irregularis). Orr and Pickerill (1995) analyzed the type specimens of some ichnospecies of Nereites originally described by Emmons (1844), as well as additional specimens. These authors considered N. macleayi (Murchison, 1839), N. cambrensis (Murchison, 1839), N. jacksoni Emmons, 1844, and N. pugnus Emmons, 1844 as distinctive ichnospecies. Mángano et al. (2000) noted that Nereites jacki Pek et al., 1978, though properly placed in Nereites, is most likely a nomen dubium, because the type material does not warrant creation of a new ichnospecies. Nereites murotoensis Katto, 1960 and N. tosaensis Katto, 1960 probably represent Protovirgularia-like structures, most likely P. longespicata (Mángano et al., 2000).

Nereites represents combined locomotion and feeding activities, and therefore it is considered to be a grazing trace (pascichnion) (Seilacher, 1983, 1986; Orr, 1995). Seilacher (1986) suggested that Nereites is produced by a wormlike sediment-feeder, probably an enteropneust that separates the coarse sediment with its protosoma and stows it in backfill lobes around the median tunnel.

Although the namesake of the deep-marine Nereites ichnofacies (Seilacher, 1967), this ichnogenus actually is a facies-crossing form that commonly is recorded in shallow-marine deposits, particularly in the Paleozoic (e.g., Conkin and Conkin, 1968; Hakes, 1976; Seilacher, 1983; Chaplin, 1985; Fillion and Pickerill, 1990; Rindsberg, 1994). Examples of Nereites in tidal-flat facies were recorded by Hakes (1976, 1977, 1985), Miller and Knox (1985), and Rindsberg (1994), among others. Nereites ranges in age from Late Precambrian/Early Cambrian to Miocene (Aceñolaza and Durand, 1973; Gregory, 1969). Lacustrine specimens recorded as Nereites from Jurassic lacustrine deposits of the Anyao Formation, central China, by Bin et al. (1998) do not display the diagnostic features of this ichnogenus. The constricted aspect of their specimens suggests placement in Vagorichnus anyao, which is the most abundant component of the Anyao ichnofauna (Buatois et al., 1995, 1996).

Nereites cambrensis Murchison, 1839

Fig. 38A-C

Figure 38--Nereites cambrensis and Nereites jacksoni. A. Nereites cambrensis. Large slab with a meandering specimen. Positive hyporelief. KUMIP 288562. x 0.2. B. Nereites cambrensis. Close-up view of specimen in A. Positive hyporelief. KUMIP 288562. x 0.34. C. Nereites cambrensis (upper left) intergrading with Nereites jacksoni (lower right). Positive hyporelief. KUMIP 288552. x 0.48. D. Nereites jacksoni. Note circular shape of the lobes. Positive hyporelief. KUMIP 288557. x 0.4. E. Nereites jacksoni preserved at the top of a sandstone bed. KUMIP 288521. x 0.34. F. Nereites jacksoni. Close-up of some specimens shown in E. KUMIP 288521. x 0.6.

Specimens--Seven slabs (KUMIP 288521, KUMIP 288524, KUMIP 288527, KUMIP 288549, KUMIP 288551, KUMIP 288552, KUMIP 288562) containing nine specimens. One of these specimens intergrades with N. jacksoni.

Description--Horizontal, meandering traces with ovate to lanceolate, lateral lobes. Adjacent lobes touch each other or partially overlap. Lobes of different rows are arranged alternately or slightly offset. Where visible, internal structure is a median back-filled tunnel. Trace width is 13.2-28.7 mm. Axial tunnel width is 3.8-7.8 mm. Lobes are 5.3-6.5 mm wide and 8.0-15.5 mm long. Preserved as positive hyporelief.

Associated Ichnofauna--Nereites cambrensis is commonly associated with Lockeia ornata, Protovirgularia bidirectionalis, and Cruziana problematica, although other ichnotaxa also may be present (e.g., Asteriacites lumbricalis, Palaeophycus tubularis).

Remarks--Nereites saltensis Aceñolaza and Durand, 1973, has lateral lobes similar to those of N. cambrensis, but those in N. saltensis are commonly less well developed than those in N. cambrensis. Mángano et al. (2000) tentatively suggested that the following ichnospecies, proposed by Delgado (1910), are junior synonyms of N. cambrensis: Nereites barroisi, N. marcoui, N. roemeri, N. liebei, N. barrandei, N. lorioili, and N. castroi. Nereites fengxianensis Cui, Yu, Mei, and Meng, 1996, also is a probable junior synonym of N. cambrensis.

Nereites imbricata Mángano, Buatois, West, and Maples, 2000

Figs. 39A-F, 40A-F

Figure 39--Nereites imbricata. All specimens preserved as positive hyporelief. A. General view of sandstone sole with several specimens of N. imbricata. KUMIP 288535. x 0.28. B. Detailed view of the specimen illustrated in the lower left of A. Note imbrication of subspherical sediment pads. KUMIP 288535. x 0.86. C. Internal structure of the specimen of N. imbricata illustrated in the center of A, showing a thin axial tunnel, flanked by transversally arranged backfill menisci. KUMIP 288535. x 0.86. Holotype. D. Two specimens of N. imbricata. Note associated Asteriacites lumbricalis and Cruziana problematica. KUMIP 288503. x 0.65. E. Detailed view of the specimen illustrated in the lower right of A. KUMIP 288535. x 0.91. F. Detailed view of the weathered specimen, illustrated in the lower right of A, with the axial channel lacking and a longitudinal furrow present. KUMIP 288535. x 0.85.

Figure 40--Nereites imbricata. All specimens preserved as positive hyporelief. A. General view of a sandstone base, preserving short specimens with tightly packed pads. KUMIP 288538. x 0.71, B. Detailed view of the specimen illustrated in the lower left of A. Note short trace composed of annulated pads re-emerging into a subspherical pad. KUMIP 288538. x 1.6. C. Specimen displaying change in pad morphology from annulated to sub spherical, coincident with a change in orientation of trace. KUMIP 288536. x 1.6. D. Detailed view of the specimen illustrated on the upper right of A. Note highly convex specimens formed by tightly packed pads, resulting in an annulated appearance. KUMIP 288538. x 1.46. E. Highly convex and very short specimen. KUMIP 288538. x 1.2. F. Specimen having a spiralled course. KUMIP 288537. x 0.92.

Specimens--Six slabs (KUMIP 288503, KUMIP 288517, KUMIP 288535, KUMIP 288536, KUMIP 288537, KUMIP 288538) with 11 specimens of different preservational variants.

Description--Predominantly horizontal, curved to slightly sinuous traces commonly preserved as imbricated subspherical pads arranged in uniserial rows. Shape and length (measured parallel to the trace axis) of pads are highly variable among specimens and reflect the degree of packing. Individual pads aligned in a row are commonly subequal in size. Pads are 12.8-17.2 mm wide and 3.6-14.9 mm long. Nested pads in some specimens do not display the characteristic subspherical shape. These traces commonly are relatively short, 27.8-37.8 mm, highly convex, and formed by tightly packed pads, resulting in an annulated appearance. Trace length is up to 119.6 mm. In a few specimens, the internal structure is clearly visible. A thin median tunnel, 1.2-2.9 mm wide, is flanked by transverse backfill menisci, 0.5-1.2 mm wide. In weathered specimens, the axial channel is lacking and a median depression can be observed. Trace walls are distinctive, but no visible lining is observed. Preserved as positive hyporelief or full relief.

Associated Ichnofauna--Nereites imbricata is commonly associated with Asteriacites lumbricalis and Cruziana problematica, but other forms (e.g., Palaeophycus tubularis) also may be present.

Remarks--Nereites imbricata differs from other Nereites ichnospecies by the characteristic external morphology of uniserial imbricate sediment pads and the poorly specialized nonmeandering pattern. Nereites imbricata winds in horizontal planes and undulates in vertical planes, resulting in tightly packed overlapping pads, producing an annulated appearance. Internally, this ichnospecies is characterized by an overlapped, obliquely arranged lamination that envelops the axial tunnel. Additionally, the enveloping-sediment-width / axial-tunnel-width ratio is remarkably larger than in the other Nereites ichnospecies (Mángano et al., 2000).

Nereites jacksoni Emmons, 1844

Fig. 38C-E

Specimens--Three slabs (KUMIP 288545, KUMIP 288552, KUMIP 288557) with three specimens, one of which intergrades with N. cambrensis.

Description--Horizontal, curved to sinuous traces with circular to subcircular, alternately arranged, lateral lobes. Lobes are smooth and envelop an axial tunnel. Trace is 17.4-24.8 mm wide. Individual lobes are 8.1-10.3 mm wide. Axial tunnel is 3.5-11.7 mm wide. Adjacent lobes touching each other or separated by up to 6.7 mm. Preserved as positive epirelief and hyporelief.

Associated Ichnofauna--Cruziana problematica, Palaeophycus tubularis, and Lockeia ornata.

Remarks--Nereites jacksoni is characterized by its circular to subcircular lobes (Orr and Pickerill, 1995). Specimens from Waverly are very similar to that figured as Nereites isp. by Hakes (1976, pl. 9, fig. 2d) from the Virgilian Tecumseh Shale in eastern Kansas.

Nereites missouriensis (Weller, 1899)

Fig. 41A-E

Figure 41--Nereites missouriensis. All specimens preserved at the top of a sandstone bed. A. Dense association of meandering specimens. KUMIP 288561. x 0.6. B. Close-up showing scalariform ridges. KUMIP 288558. x 1.4. C. Specimen with well developed lateral lobes. KUMIP 288573. x 0.87. D. Specimens with sharply defined scalariform ridges. KUMIP 28864. x 1.05. E. Close-up of a specimen having a single row of spherical pustules. KUMIP 288561. x 1.4.

Specimens--Ten slabs (KUMIP 288531, KUMIP 288535, KUMIP 288540, KUMIP 288548, KUMIP 288557, KUMIP 288558, KUMIP 288561, KUMIP 288562, KUMIP 288564, KUMIP 288573) containing at least 32 specimens.

Description--Horizontal to rarely oblique, winding, meandering to exceptionally coiled traces composed of transverse scalariform ridges along entire length of trace. Envelope zone consisting of sand lobes commonly present on both sides of the tunnel. In one specimen, trace-fill locally preserved as a single row of gray clay pustules, displaying the external sculpture of Neonereites uniserialis. Trace diameter highly variable within a single specimen. Traces are 3.2-10.3 mm wide. Envelope zone up to 6.7 mm wide. Scalariform ridges 0.4-1.6 mm wide and separated from each other by 0.6-4.1 mm. Preserved as negative epireliefs.

Associated Ichnofauna--Nereites missouriensis commonly occurs in monospecific assemblages. In other cases, it is associated with Phycosiphon incertum, Curvolithus simplex, and Protovirgularia bidirectionalis.

Remarks--Originally described as Scalarituba missouriensis, this ichnospecies is included herein under Nereites following the suggestions of Seilacher and Meischner (1965), Chamberlain (1971), D' Alessandro and Bromley (1987), Rindsberg (1994), and Uchman (1995). Seilacher and Meischner (1965) noted that the lateral lobes are hardly visible. Weller (1899) did not describe lateral lobes, but his figured specimens (Weller, 1899, pl. VI, fig. 1) have sediment lobes locally along the margins of the trace. Uchman (1995, Text-fig. 8B) illustrated different preservational variations of N. missouriensis, and specimens from Waverly compare favorably with the thick-meniscate form of Uchman (1995). Nereites missouriensis is typified by its scalariform ridges (Conkin and Conkin, 1968). A synonym for N. missouriensis was provided by Uchman (1995). We agree with Conkin and Conkin (1968), who regarded Scalarituba? atoka Branson, 1966, as a junior synonym of Nereites missouriensis. Akinereites kannouraensis Katto, 1965 and Notaculites toyomensis Kobayashi, 1945 also are junior synonyms of Nereites missouriensis. Scalarituba welleri Branson, 1938, does not exhibit the scalariform ridges of Nereites missouriensis and it should be removed from this ichnogenus, as originally suggested by Conkin and Conkin (1968). Scalarituba indica Chiplonkar and Tapaswi, 1972, is a back-filled trace that should be removed from the Nereites group and be included in Taenidium. As noted by Uchman (1995), Scalarituba darvaseana Vialov, 1979, also is a junior synonym of N. missouriensis, as is Maldanidopsis meandriformis (Müller, 1966), which was redescribed by Plicka (1973). Scalarituba lungmaxiensis Yang, 1984, should be removed from the Nereites group because it represents a form similar to Protovirgularia. Scalarituba michlensis Mikuláš, 1992, does not display the diagnostic features of N. missouriensis and is of uncertain taxonomic affinities. Conkin and Conkin (1968) reviewed occurrences of N. missouriensis in Paleozoic strata of North America and concluded that this form occurs in prolific numbers in tidal-flat settings. Nereites missouriensis also has been recorded in slope to deep-marine environments (e.g., Buatois and Mángano, 1992; Uchman, 1995).

Ichnogenus Palaeophycus Hall, 1847

Discussion--The taxonomy of Palaeophycus has been discussed by Pemberton and Frey (1982) and by Keighley and Pickerill (1995). Palaeophycus is distinguished from Planolites by the presence of wall linings and by a burrow-fill identical to the host rock (Pemberton and Frey, 1982), and from Macaronichnus by the active burrow-fill of the latter (Clifton and Thompson, 1978; Curran, 1985). Jensen (1997) noted the problems of differentiating Palaeophycus from Planolites in the case of concealed bed-junction preservation.

Pemberton and Frey (1982) regarded five ichnospecies of Palaeophycus as valid: P. tubularis Hall, 1847, P. striatus Hall, 1852, P. heberti (de Saporta, 1872), P. sulcatus (Miller and Dyer, 1878a), and P. alternatus Pemberton and Frey, 1982. Subsequent to that review, seven additional ichnospecies have been proposed: P. ferrovittatus Hofmann, 1983, P. subornatus Ghare and Kulkarny, 1986, P. annulatus Badve, 1987, P. anulatus McCann and Pickerill, 1988, P. canalis Walter et al., 1989, P. serratus McCann, 1993, and P. crenulatus Buckman, 1995. Additionally, Jensen placed Halopoa imbricata Torell, 1870, in Palaeophycus as P. imbricatus. Recently, Buckman (1995) discussed the taxonomy of annulate ichnospecies of Palaeophycus, and considered P. annulatus, P. anulatus, P. canalis, and P. serratus as nomina dubia. P. subornatus is characterized by a thick wall and transverse markings. However, ornamentation is not displayed clearly in the illustrated holotype, so Mángano et al. (1996) considered this ichnospecies a nomen dubium. Rituichnus Yang, Song, and Liang, 1982, has been regarded as a junior synonym of Palaeophycus striatus by Fillion and Pickerill (1990).

Palaeophycus is a passively filled open burrow that is interpreted as the dwelling structure (domichnion) of predaceous or suspension-feeding animals (Pemberton and Frey, 1982). Osgood (1970) suggested the predaceous polychaete Glycera as a modern analog for the Palaeophycus tracemaker.

The ichnogenus Palaeophycus has been recorded in nonmarine (e.g., Buatois and Mángano, 1993a), marginal-marine (e.g., Wightman et al., 1987), shallow-marine (e.g., Maples and Suttner, 1990), and deep-marine (e.g., Miller, 1993) settings. Occurrences of Palaeophycus in tidal-flat settings has been recorded by several authors (e.g., Narbonne, 1984; Mángano et al., 1996; Stanley and Feldmann, 1998). It ranges in age from Precambrian to Pleistocene (Narbonne and Hofmann, 1987; D' Alessandro and Bromley, 1986).

Palaeophycus tubularis Hall, 1847

Fig. 42A-D

Figure 42--Palaeophycus tubularis. All are base of bed views. A. Curved specimen of P. tubularis. KUMIP 288543. x 0.99. B. Specimens with secondary successive branching. KUMIP 288514. x 1.4. C. Specimen showing elliptical cross section. KUMIP 288552. x 1.28. D. Slightly sinuous specimen. KUMIP 288504. x 0.9.

Specimens--Ten slabs (KUMIP 288500, KUMIP 288514, KUMIP 288521, KUMIP 288538, KUMIP 288543, KUMIP 288544, KUMIP 288545, KUMIP 288555, KUMIP 288561, KUMIP 288574) with 20 specimens.

Description--Straight to sinuous, horizontal, commonly unbranched, thinly lined to unlined, smooth-walled cylindrical, endichnial burrow. Some specimens display primary or secondary successive branching. Burrow diameter is 5.1-11.3 mm. Maximum length observed is 91.0 mm. Burrow-fill is similar to the host rock and massive. No evidence of burrow collapse has been detected. Preserved as both positive hyporelief and epirelief.

Associated Ichnofauna--Palaeophycus tubularis commonly is associated with Protovirgularia bidirectionalis, Curvolithus simplex, Lockeia siliquaria, and Parahaentzschelinia ardelia, but other forms also may be present.

Remarks--Palaeophycus tubularis is typified by its thin, smooth walls (Pemberton and Frey, 1982).

Ichnogenus Parahaentzschelinia Chamberlain, 1971

Discussion--Parahaentzschelinia was created by Chamberlain (1971) to include shafts radiating from a vertical central tunnel. Parahaentzschelinia differs from Arborichnus Ekdale and Lewis, 1991, in having all shafts radiating from a central tunnel; however, in the latter the shaft splits at irregular intervals into multiple branches.

Altichnus Bromley and Hanken, 1991, is similar but the shafts in this ichnogenus expand upward (Bromley and Hanken, 1991). Two ichnospecies have been recognized: P. ardelia Chamberlain, 1971 and P. surlyki Dam, 1990b.

Chamberlain (1971) regarded Parahaentzschelinia as a feeding trace (fodinichnion). Dam (1990b) interpreted the main tunnel in his specimens as an escape structure (fugichnion) on the basis of its association with hummocky cross stratified beds. However, he considered the whole biogenic structure as a dwelling trace (domichnion), an interpretation supported by the thick lining of the tunnel walls. Uchman (1995) recognized three different types, informally named "A, B, and C," but he suggested that form B may represent part of a graphoglyptid system (agrichnion), which therefore could be included in some other ichnogenus. Specimens from Waverly ethologically resemble those described by Chamberlain (1971). Absence of thick linings and presence of systematic branching support a fodinichnia interpretation. According to Chamberlain (1971), the structure is produced by a worm that repeatedly extends up and outward from a fixed central point in search of food. Polychaete annelids are the potential tracemakers.

Parahaentzschelinia is known from both deep-marine (e.g., Chamberlain, 1971; Uchman, 1995; Tunis and Uchman, 1996) and shallow-marine facies (e.g., Dam, 1990a). The Waverly occurrence is the first report of this ichnotaxon in tidal-flat facies. Parahaentzschelinia ranges in age from Carboniferous to Miocene (Chamberlain, 1971; Uchman, 1995).

Parahaentzschelinia ardelia Chamberlain, 1971

Fig. 43A-D

Figure 43--Parahaentzschelinia ardelia. All are base of bed views. A. Specimens protruding from the base of a sandstone bed. Note radial arrangement suggesting the presence of a central shaft. KUMIP 288524. x 0.97. B. Specimens of P. ardelia cross cutting Protovirgularia bidirectionalis (arrow). KUMIP 288555. x 1.27. C. Parahaentzschelinia ardelia crosscutting poorly preserved Cruziana problematica. KUMIP 288514. x 1.8. D. Specimens having a linear arrangement. KUMIP 288514. x 1.27.

Specimens--Four specimens on three slabs (KUMIP 288514, KUMIP 288524, KUMIP 288555).

Description--Structures consisting of numerous oblique to rarely vertical, very thinly lined tubes of sandstone. Tunnel fill is structureless. Poorly preserved annulations are present in some trace walls. Individual tubes are 3.0-8.5 mm in diameter and up to 12.2 mm long. System consists of up to 25 tunnels and is 12.8-22.7 mm wide. In one specimen, tubes form an elongated cluster 8.3 mm wide and 36.5 mm long. Preserved as positive epirelief, positive hyporelief, or full relief.

Associated Ichnofauna--Parahaentzschelinia ardelia commonly is associated with Protovirgularia bidirectionalis, Curvolithus simplex, and Cruziana problematica.

Remarks--Specimens from Waverly closely resemble the types described by Chamberlain (1971) in overall pattern, branching style, and absence of thick wall linings, and are therefore ascribed to P. ardelia. However, the Waverly specimens are larger than those from Oklahoma and lack a lateral gallery. P. ardelia differs from P. surlyki in the absence of thick wall linings. Additionally, the type specimens of P. surlyki are deeper and wider.

Ichnogenus Pentichnus Maerz, Kaesler, and Hakes, 1976

Discussion--Pentichnus was created by Maerz et al. (1976) for subcylindrical to subconical, vertical structures having pentameral symmetry. Rindsberg (1990) and Mángano et al. (1999) noted similarities between this ichnotaxon and Asteriacites gugelhupf Seilacher, 1983. Deep, permanent to semi-permanent burrows, such as A. gugelhupf, are remarkably different from the shallow, temporary resting traces that are typically included in Asteriacites. Accordingly, Mángano et al. (1999) removed A. gugelhupf from Asteriacites and placed it in Pentichnus as a separate ichnospecies (P. gugelhupf) characterized by lateral grooves.

Maerz et al. (1976) interpreted Pentichnus as a dwelling trace (domichnion) or a resting trace (cubichnion). Overall burrow morphology and penetration depth of the structures favor a domichnia interpretation. Maerz et al. (1976) noted that the pentameral symmetry indicates an echinoderm trace maker, most likely an ophiuroid. Based on the presence of lateral grooves, Seilacher (1983) favored an asteroid origin for P. gugelhupf Rindsberg (1994) even proposed stalkless crinoids as potential tracemakers.

Pentichnus has been recorded only from Carboniferous shallow-marine environments (Maerz et al., 1976; Seilacher, 1983, 1990b; Rindsberg, 1990).

Pentichnus pratti Maerz, Kaesler, and Hakes, 1976

Fig. 44A-B

Figure 44--Pentichnus pratti. Both are base of bed views. A. Specimen with apical end having a poorly developed protuberance. KUMIP 288535. x 0.83. B. Specimen with well developed pentameral symmetry. KUMIP 288540. x 1.59.

Specimens--Two slabs (KUMIP 288535, KUMIP 288540) with two specimens.

Description--Subconical structures vertically oriented, projecting from the sole of sandstone beds, characterized by pentameral symmetry. Apical end may have a poorly developed protuberance. Diameter is 16.3-31.5 mm. Facet width is 10.5-19.0 mm. Preserved as positive hyporeliefs.

Associated Ichnofauna--Pentichnus pratti is associated with Cruziana problematica, Nereites imbricata, Rhizocorallium irregulare, Palaeophycus tubularis, Lockeia siliquaria, and Protovirgularia bidirectionalis.

Remarks--Absence of lateral grooves distinguishes the Waverly specimens from P. gugelhupf. Specimens of Pentichnus from the Stull Shale Member show the basic morphology of Pentichnus pratti Maerz, Kaesler, and Hakes, 1976, the type ichnospecies.

Ichnogenus Phycodes Richter, 1850

Discussion--Seilacher (1955) regarded Arthrophycus Hall, 1852, as a junior synonym of Phycodes. However, most authors recognize them as separate ichnogenera (e.g., Hantzschel, 1975; Han and Pickerill, 1994b). Phycodes was reviewed by Han and Pickerill (1994b) and Pickerill et al. (1995), who recognized the following valid ichnospecies: P. palmatus (Hall, 1852); P. circinatus Richter, 1853; P. pedum Seilacher, 1955; P. reniforme Hofmann, 1979; P. curvipalmatum Pollard, 1981; P. yichangensis Yang, 1984; P. coronatum Crimes and Anderson, 1985; P. wabanensis Fillion and Pickerill, 1990; P. ungulatus Fillion and Pickerill, 1990; P. auduni Dam, 1990; P. bromleyi Dam, 1990b; and P. templus Han and Pickerill, 1994b. The taxonomic position of Phycodes pedum remains controversial. Geyer and Uchman (1995) considered P. pedum as an ichnospecies of Trichophycus. However, Jensen (1997) placed P. pedum in Treptichnus, and he suggested affinities with Treptichnus for P. yichangensis and P. templus.

Phycodes is interpreted as a feeding trace (fodinichnion) (Seilacher, 1955; Osgood, 1970). The most likely tracemakers are annelids (Seilacher, 1955), although pennatulaceans (Bradley, 1980) and anthoptiloids (Bradley, 1981) also have been suggested. Specimens figured as Phycodes by Bradley (1980, figs. 3 and 4), however, should be assigned to Chondrites.

Although more typical of shallow-marine facies (e.g., Crimes and Anderson, 1985; Paczesna, 1996; Jensen, 1997), Phycodes is also known from nonmarine (e.g., Pollard, 1985), marginal-marine (e.g., Hakes, 1985), and deep-marine environments (e.g., Crimes et al., 1981; Buatois et al., 2001). Phycodes has been mentioned in tidal-flat environments by Martino (1996). It ranges in age from Cambrian to Miocene (Crimes and Anderson, 1985; Bradley, 1981).

Phycodes palmatus Hall, 1852

Fig. 45A

Specimens--One slab (KUMIP 288555) with a single specimen.

Description--Horizontal branching system, consisting of a few branches developed from a single proximal tunnel and arranged in a digitate pattern. Branches taper laterally. Diameter of individual branches is highly variable. Tunnel fill similar to host rock. Trace diameter 5.3-8.1 mm. Length of the structure 66.4 mm. Preserved as positive hyporelief.

Associated Ichnofauna--Halopoa isp., Parahaentzschelinia ardelia, Protovirgularia bidirectionalis, Palaeophycus tubularis, and small horizontal cylindrical burrows.

Remarks--Phycodes palmatus is characterized by having only a few branches arranged in a palmate or digitate form (Fillion and Pickerill, 1990). These diagnostic features are clearly observed in the Waverly specimen.

Phycodes isp.

Fig. 45B

Figure 45--Ichnospecies of Phycodes. A. Phycodes palmatus. Note associated Protovirgularia bidirectionalis (arrow). Positive hyporelief. KUMIP 288555. x 0.6. B. Phycodes isp. preserved on a ripple top. Discontinuous specimen extending below the flat ripple crest. Positive epirelief. KUMIP 288500. x 0.85.

Specimen--One slab (KUMIP 288500) containing a single specimen.

Description--Horizontal branching system of a few branches developed from a single proximal tunnel and arranged in a fasciculate pattern. Proximal parts of the main tunnels are unbranched, but the distal parts branch at acute angles into recurved segments. Diameter of individual branches remains relatively constant. Tunnel fill is similar to host rock, Trace diameter 0.4-2.7 mm. Length of the structure 90.7 mm. Preserved as positive epirelief.

Associated Ichnofauna--Teichichnus rectus, Protovirgularia bidirectionalis, Curvolithus simplex, and Palaeophycus tubularis.

Remarks--Partial preservation precludes a confident designation of the ichnospecies.

Ichnogenus Phycosiphon Fischer-Ooster, 1858

Discussion--Controversy exists regarding the relationship among Phycosiphon Fischer-Ooster, 1858, Helminthopsis Heer, 1877, and Anconichnus Kern, 1978. The names Phycosiphon incertum, Anconichnus horizontalis, and Helminthopsis horizontalis have been used to designate essentially the same type of biogenic structure (e.g., Kern, 1978; Bromley, 1990; Goldring et al., 1991; Wetzel and Bromley, 1994). This taxonomic problem has been analyzed by Wetzel and Bromley (1994), who regarded Anconichnus as a junior synonym of Phycosiphon. Wetzel and Bromley (1994) emphasized the presence of a dark core and a pale mantle as a diagnostic feature of Phycosiphon, with poorly developed spreiten also present. Helminthopsis is best retained for irregularly meandering traces lacking spreiten and mantle (Han and Pickerill, 1995; Wetzel and Bromley, 1996).

Phycosiphon has been interpreted either as a grazing trail (pascichnion) or a feeding trace (fodinichnion) produced by a deposit feeder (Ekdale and Mason, 1988; Goldring et al., 1991; Fu, 1991; Wetzel and Bromley, 1994). Presence of a spreite supports a fodinichnial interpretation, though a spreite is typically not discernible. Goldring et al. (1991) suggested that Phycosiphon is produced by polychaetes that employ defecation of digested mud to create the central core and sorting of the sediment by parapodia to form the trace halo. Phycosiphon typically occupies shallow tiers and probably is produced by an opportunistic animal (Goldring et al., 1991; Wetzel and Bromley, 1994).

Phycosiphon is known only from marine environments, ranging from deep marine (e.g., Wetzel and Uchman, 1997) to shallow marine (e.g., Goldring et al., 1991) and marginal marine (e.g., Bradley and Pemberton, 1992). It ranges in age from Ordovician to Holocene (e.g., Hantzschel, 1975; Wetzel and Wijayananda, 1990).

Phycosiphon incertum Fischer-Ooster, 1858

Fig. 46A-B

Figure 46--Phycosiphon incertum. Top of bed view. KUMIP 288564. A. General view of several, poorly preserved specimens. x 0.71. B. Close-up of some specimens on the slab illustrated in A. x 1.28.

Specimens--Two slabs (KUMIP 288503, KUMIP 288564) with several specimens, the exact number of which is impossible to assess.

Description--Horizontal traces comprising recurving U-shaped lobes. Core of curved segments surrounded by a sediment mantle. Core is 0.9-1.4 mm wide. Mantle is 0.5-1.0 mm wide. Spreiten were not observed. Traces in high densities cover top of a very fine grained sandstone. Preserved as negative epirelief.

Associated Ichnofauna--Nereites missouriensis.

Remarks--Spreiten are not apparent in the Waverly specimens. However, the traces show the typical recurving shape and the halo of P. incertum, and therefore they are assigned to this ichnospecies.

Ichnogenus Planolites Nicholson, 1873

Discussion--Planolites differs from Palaeophycus by having an unlined wall and a fill different from the host rock (Pemberton and Frey, 1982), and it differs from Macaronichnus by the presence of a lined wall in the latter (Curran, 1985). Keighley and Pickerill (1995) regarded the absence of wall linings as the diagnostic feature of Planolites. Five ichnospecies of Planolites have been recognized: P. beverleyensis (Billings, 1862), P. annularius (Walcott, 1890), P. montanus Richter, 1937, P. terraenovae Fillion and Pickerill, 1990, and P. constriannulatus Stanley and Pickerill, 1994. Planolites ballandus Webby, 1970, regarded as a junior synonym of P. montanus by Pemberton and Frey (1982), subsequently was considered a valid ichnospecies by Walter et al. (1989). However, Mángano et al. (1996) placed it again in P. montanus. Planolites nematus Kowalski, 1987, also was regarded as a junior synonym of P. montanus by Orlowski and Zylinska (1996).

Planolites is interpreted as feeding structures (fodinichnia) of deposit-feeders, most likely polychaetes (Pemberton and Frey, 1982). However, other phyla also may be responsible (Fillion and Pickerill, 1990).

Planolites is a facies-crossing ichnotaxon that has been recorded in deep-marine (e.g., Buatois and Lopez Angriman, 1992), shallow-marine (e.g., Orlowski and Zylinska, 1996), marginal-marine (e.g., Archer and Maples, 1984), and continental facies (e.g., Pickerill, 1992). It is a common component of tidal-flat ichnofaunas (e.g., Ireland et al., 1978). Planolites ranges in age from Precambrian to Pleistocene (Gibson, 1989; Wetzel, 1981).

Planolites beverleyensis (Billings, 1862)

Fig. 47A-B

Figure 47--Planolites beverleyensis. Top of bed view. KUMIP 288539. A. General view of a strongly weathered rippled top with a specimen of P. beverleyensis. x 0.27. B. Close-up view of the specimen in A. x 0.45.

Specimen--A single specimen on slab KUMIP 288539.

Description--Horizontal, subcylindrical, unlined, slightly curved trace. Trace fill different in color and grain size from the host rock. Trace surface typically smooth. Diameter fairly constant within the specimen. Maximum length observed is 87.12 mm. Diameter is 13.7-21.6 mm. Preserved as full relief.

Associated Ichnofauna--Planolites beverleyensis is associated with Diplocraterion isp. B.

Remarks--Planolites beverleyensis differs from P. montanus by the smaller size and contorted to curved course of the latter (Pemberton and Frey, 1982). Absence of ornamentation and/or annulations distinguishes P. beverleyensis from P. terraenovae, P. annularius, and P. constriannulatus.

Ichnogenus Protovirgularia McCoy, 1850

Discussion--Protovirgularia has received considerable attention in recent years (e.g., Han and Pickerill, 1994c; Rindsberg, 1994; Seilacher and Seilacher, 1994; Uchman, 1998). McCoy (1850) established Protovirgularia for structures composed of a median line and lateral chevron-like markings. Han and Pickerill (1994c) revised this ichnogenus and concluded that P. dichotoma McCoy, 1850, the type species, was the only valid name. Protovirgularia harknessi Lapworth, 1870, P. nereitarum Richter, 1871, and P. mongraensis Chiplonkar and Badve, 1970, do not differ significantly from Protovirgularia dichotoma, their senior synonym (Han and Pickerill, 1994c). Han and Pickerill (1994c) also provided an interesting historical overview about the multiple and dissimilar origins ascribed to Protovirgularia. Originally interpreted as a body fossil, either an octocoral (McCoy, 1850; Alloiteau, 1952) or a graptolite (Richter, 1853), Protovirgularia was first recognized as a trace fossil by Hantzschel (1958). Rindsberg (1994) included subhorizontal traces with imbricated chevrons terminating in an oval- or almond-shaped structure in the ichnogenus Walcottia Miller and Dyer, 1878b.

Rindsberg (1994) reduced the number of available names for describing essentially similar structures by synonymizing the ichnogenera Biformites Linck, 1949, Imbrichnus Hallam, 1970, and Chevronichnus Hakes, 1976, with Walcottia. However, Rindsberg (1994) did not comment on the similarities between Walcottia and Protovirgularia. Based on the association with Lockeia, Rindsberg (1994) also noted that bivalves were the most probable trace makers of Walcottia, as well as Sustergichnus Chamberlain, 1971, which he did not include in Walcottia. However, because the mode of construction of Protovirgularia and Walcottia was not clearly understood, these ichnogenera remained somewhat enigmatic.

In an actuopaleontologic approach, Seilacher and Seilacher (1994) compared traces produced by the cleft-foot bivalve Acila with chevron structures known from the fossil record. Based on the unique basic pattern of behavior involved in the locomotion of cleft-foot bivalves, these authors revived the ichnogenus Protovirgularia as the senior synonym of Walcottia, Pennatulites de Stefani, 1885, Paleosceptrom de Stefani, 1885, Biformites, Uchirites Macsotay, 1967, Imbrichnus, and Sustergichnus. Following the same line of reasoning, Chevronichnus and Polypodichnus Ghare and Kulkarni, 1986, also should be considered junior synonyms of Protovirgularia. We generally agree with the Seilacher and Seilacher (1994) taxonomic scheme for Protovirgularia, although some adjustments and additions are needed. Seilacher and Seilacher (1994) recognized five ichnospecies of Protovirgularia: P. dichotoma McCoy, 1850, P. triangularis (Macsotay, 1967), P. tuberculata (Williamson, 1887), P. rugosa (Miller and Dyer, 1878b), and P. longespicata (deStefani, 1885), More recently, Uchrnan (1998) revised the Marian Ksiazkiewicz collection and recognized three additional ichnospecies: P. obliterata (Ksiazkiewicz , 1977), P. vagans (Ksiazkiewicz, 1977), and P. dzulynskii (Ksiazkiewicz , 1977).

Protovirgularia dichotoma, the type species, is a shallow Protovirgularia that is somewhat reminiscent of an arthropod trackway, but it is clearly symmetrical about the median axis. We had the opportunity to inspect casts of P. dichotoma, originally described by Richter (1941) as Ichnia spicea from the Devonian Hunsrück Shale. These specimens record the morphological variability of this form according to pore fluid content. In highly fluid substrate, chevrons of P. dichotoma display petaloid appearance. In slightly stiffer sediment P. dichotoma exhibits its classical symmetrical, delicate, V-shaped marks tangential to the median mark. Protovirgularia dichotoma is a straight, horizontal locomotion trace. None of the Hunsrück specimens is connected to Lockeia-like structures. Our observations on the type material of P. triangularis show that it is a mostly smooth, deeply impressed, tubular carinate structure with distinct triangular cross section. Chevrons are faint, closely spaced, but only very locally present. Material from Paleogene flysch deposits of Venezuela, referred to by Macsotay (1967) as Nereites (pl. 5, Fig. 11, 13 and 14) and Gyrochorte (pl. 5, Fig. 12), is herein included in Protovirgularia. The specimens from Venezuela display large, open chevrons, resulting in a vertebrae-like appearance, somewhat reminiscent of P. longespicata. However, this form does not display the morphological complexity of P. longespicata (cf. Seilacher and Seilacher, 1994, pl. 2) and most likely represents a new ichnospecies. Notably, this material shows close similarities with specimens from the Tertiary of Trinidad, labelled as Virgularia presbytes and housed at the British Museum of Natural History (BMNH). Protovirgularia tuberculata is a deeply impressed bilobated hypichnial structure with distinct chevrons that superficially resembles Cruziana. In their diagnosis of P. tuberculata, Seilacher and Seilacher (1994, p. 10) do not mention the presence of small tubercles on chevrons. Examination of Williamson's type material at the BMNH suggests that Protovirgularia tuberculata exhibits conspicuous, regularly spaced tubercles (see also Williamson 1887, p. 22 and Fig.2). Seilacher and Seilacher (1994) included Sustergichnus lenadumbratus in Protovirgularia triangularis. However, our observations on the type specimens of S. lenadumbratus indicate that this form shows affinities with P. tuberculata rather than with P. triangularis. Sustergichnus lenadumbratus displays small tubercles on chevrons, and its general morphology (i.e. bilobated structure with well-impressed, regular chevrons) is similar to P. tuberculata. Reexamination of the type specimens of Imbrichnus wattonensis Hallam, 1970, at the Oxford University Museum, allows placement of this ichnospecies in P. rugosa. Protovirgularia rugosa is a relatively short Protovirgularia connected to a smooth cylindrical to almond-shaped resting structure (Seilacher and Seilacher, 1994; Uchman, 1998). "Relatively short," in this context, is understood as subordinately horizontal, predominantly inclined structures that cross bedding planes. Some specimens of P. rugosa, however, can display significant horizontal locomotion; good examples are P. rugosa var. Imbrichnus and P. rugosa var. Chevronichnus. Chevrons are sharp, commonly tightly packed resulting in a wrinkled appearance. The Waverly material shows that the distinction between P. dichotoma and P. rugosa on strict morphological bases can be difficult in practice. Specimens exceedingly long (i.e. with significant horizontal displacement) can be, if partially preserved, within the expected morphological variability of P. dichotoma. The common gregarious occurrence of P. rugosa and invariable association with Lockeia, however, help to provide an appropriate assignment. This calls for identification based on a representative sample rather than a few, fragmentary specimens. Based on Miller and Dyer type specimens of Walcottia rugosa, Seilacher and Seilacher (1994) considered escape traces leading away from smooth resting structures as P. rugosa. Uchman (1998) also included short locomotion traces ending at Lockeia-like structures (Uchman, 1998, Fig. 67C). Seilacher and Seilacher (1994) interpreted P. rugosa as escape structures responding to episodic storm sedimentation; Uchman (1998) added also turbiditic sedimentation. Waverly specimens indicate that P. rugosa also can be related to rapid tidal sedimentation. Protovirgularia longespicata is a complex Protovirgularia characterized by strong papillate chevrons, the overall form of which may be palmate with spreiten-like structure (Seilacher and Seilacher, 1994, Pl. 2).

Uchman (1998) revised the Marian Ksiazkiewicz collection and placed in Protovirgularia several specimens included by Ksiazkiewicz (1977) under various ichnogenera, such as Rhabdoglyphus Vassoevich, 1951, Gyrochorte Heer, 1865, Tuberculichnus Ksiazkiewicz , 1977, Arthrophycus Hall, 1852, and Keckia Glocker, 1841. This author considered P. triangularis similar to P. pennatus (Eichwald, 1860), which has priority, and therefore regarded P. triangularis as a junior synonym of P. pennatus. Although the general morphology of P. pennatus resembles P. triangularis-type material, chevrons are more conspicuous and deeply impressed in the former. Additionally, Uchman (1998) placed the following ichnospecies in Protovirgularia: Gyrochorte obliterata Ksiazkiewicz , 1977, as P. obliterata; Tuberculichnus vagans Ksiazkiewicz , 1977, and Tuberculichnus meandrinus Ksiazkiewicz, 1977, as P. vagans; and Arthrophycus (?) dzulynskii Ksiazkiewicz , 1977, as P. dzulynskii. Protovirgularia obliterata and P. dzulynskii are known from very fragmentary material. We agree with Uchman that Gyrochorte obliterata should actually be included in Protovirgularia (cf. Uchman 1998, Fig. 68C). The ichnospecies P. obliterata, however, is not very distinctive and is best considered a nomen dubium. Protovirgularia dzulynskii is a distinct form with strong, papillated, riblike chevrons. It is a complex structure reminiscent of P. longespicata, but the material is too fragmentary. Protovirgularia vagans was defined by Uchman (1998) as a smooth Protovirgularia having a strong carinate profile, undulating in the vertical plane and resulting in discontinuous ridges. This form lacks the distinctive chevronate pattern of Protovirgularia and is best considered as an ichnospecies of Lockeia. Seilacher and Seilacher (1994) created Lockeia serialis to include serial alignments of Lockeia-like structures. Linck's original material consists of a straight, continuous alignment of Lockeia (Linck, 1949, pl. VIII, Fig. 1, 2). The Polish flysch specimens, however, record an undulating movement in the vertical plane and an open meandering pattern, warranting ichnospecific assignment as Lockeia vagans.

Bandel (1967a) described a wide variety of forms under Crossopodia dichotoma. As discussed by Mángano et al. (in press), Crossopodia is a problematic ichnotaxon and its abandonment is recommended. Han and Pickerill (1994) reassigned Bandel's material to Protovirgularia dichotoma. Although we agree with inclusion of these specimens within Protovirgularia, the wide variety of morphologies and size ranges exhibited by Bandel's material does not warrant inclusion within P. dichotoma. Our observations of Bandel's collection suggest that several distinct ichnospecies are present and that further detailed studies are needed. As outlined by Mángano et al. (1998), substrate conditions, particularly substrate consistency, playa major role in the morphology of Protovirgularia. Substrate character per se, however, is not considered a valid ichnotaxobase. Variability of Bandel's Protovirgularia collection cannot be explained in terms of a preservational bias. For example, the specimen of P. dichotoma KUMIP 25104 exhibits a peculiar chevron pattern resulting in apparent bifurcated chevrons (Bandel 1967, pl. 3, Fig. 7).

Protovirgularia has been interpreted as a locomotion structure (repichnion). This ichnogenus, however, embraces many combined behavioral forms. For instance, P. rugosa can be interpreted as an escape structure (fugichnion), and P. tuberculata and P. longispicata are locomotion/feeding structures (pascichnia). Different possible tracemakers have been proposed for Protovirgularia, including arthropods (Gümbel, 1879; Richter, 1941; Volk, 1961), annelids (Richter, 1941; Claus, 1965), and bivalves (Bandel, 1967a; Hallam, 1970; Hakes, 1977, Maples and West, 1990; Han and Pickerill, 1994c; Rindsberg, 1994; Seilacher and Seilacher, 1994). A better understanding of the constructional techniques and functional limitations of these different types of organisms supports cleft-foot bivalves as the most likely tracemakers (Seilacher and Seilacher, 1994; Mángano et al., 1998). Seilacher and Seilacher (1994) also mentioned the possibility of scaphopods as producers, particularly if the chevroned locomotion traces are not associated with Lockeia-like resting structures.

Although originally described from deep-marine facies (e.g., McCoy, 1851a; Volk, 1961; Macsotay, 1967; Chamberlain, 1971; Benton, 1982b; Han and Pickerill, 1994c; Uchman, 1998), Protovirgularia also is well-represented in shallow open-marine and marginal-marine facies (e.g., Bandel, 1967a; Osgood, 1970; Hallam, 1970). Examples of this ichnogenus in tidal-flat facies have been documented by Bandel (1967a), Hakes (1976), and Mángano and Buatois (1997), among many others. Protovirgularia ranges from Ordovician to Holocene (e.g., Osgood, 1970; Seilacher and Seilacher, 1994).

Protovirgularia bidirectionalis n. isp.

Figs. 48A-C, 49A-G, 50

Figure 48--Protovirgularia bidirectionalis. General views. A. Several specimens with very thickly lined walls and U-shaped geometry, oriented oblique to ripple trend. Top of bed view. KUMIP 288514. x 0.41. B. Dense assemblage of shafts of P. bidirectionalis with very thick walls, preserved on the top of a rippled sandstone bed. Note exhumed burrows crosscutting each other on the left. KUMIP 288544. x 0.34. C. Base of a sandstone slab with a dense assemblage of P. bidirectionalis. Note subparallel orientation. Most burrows oriented approximately 35° relative to ripple train. KUMIP 288534. x 0.17.

Figure 49--Protovirgularia bidirectionalis. Close-up views of base of burrows. A. Small burrow showing V-shaped markings with opposite directions meeting at a central point. Note that the direction of movement is from the center to the ends. KUMIP 288500. x 0.97. B. Burrow showing V-shaped markings with opposite directions at different levels. Note that at the lowermost level the direction of movement is toward the center of the structure (opposite of A). KUMIP 288559. x 0.97. C. Low-angle secondary successive branching without significant widening of the resulting structure. Burrow on the right seems to enter the structure on the left. KUMIP 288544. x 0.69. D. Burrow showing V-shaped markings with opposite directions connected by a smooth central segment. KUMIP 288531. x 0.69. E. Y-shaped secondary successive branching with significant widening of the resulting structure. Burrow on the left seems to deviate from the main structure on the right. KUMIP 288552. x 0.69. F. Crosscutting of two specimens showing one predominant direction ofV-shaped markings. KUMIP 288544. x 0.69. G. Complex crosscutting relationships between specimens. Note bilobate internal structure (lower left specimen) and superimposed chevrons oriented in the opposite direction (upper specimen). KUMIP 288531. x 0.44.

Figure 50--Behavioral reconstruction of Protovirgularia bidirectionalis. The bivalve constructed a U-shaped burrow in which it grazed organic debris transported by the tidal flood. It apparently turned around, perhaps during the slack-water period, and grazing was re-established during the ebb flow. Repetition of this activity led to the formation of a vertical spreiten structure.

Specimens--Thirty-seven slabs (KUMIP 288500, KUMIP 288501, KUMIP 288504, KUMIP 288509, KUMIP 288514, KUMIP 288519, KUMIP 288520, KUMIP 288522, KUMIP 288523, KUMIP 288524, KUMIP 288527, KUMIP 288530, KUMIP 288531, KUMIP 288532, KUMIP 288533, KUMIP 288534, KUMIP 288538, KUMIP 288540, KUMIP 288541, KUMIP 288542, KUMIP 288543, KUMIP 288544, KUMIP 288548, KUMIP 288549, KUMIP 288550, KUMIP 288551, KUMIP 288552, KUMIP 288554, KUMIP 288555, KUMIP 288556, KUMIP 288558, KUMIP 288559, KUMIP 288560, KUMIP 288561, KUMIP 288562, KUMIP 288569, KUMIP 288570) containing 231 specimens and several others recorded in the field.

Type Specimens--Specimen illustrated in fig. 49B (KUMIP 288559) is designated as the holotype; all the other specimens are considered paratypes.

Diagnosis--Relatively shallow, U-shaped traces with basal V-shaped markings oriented in opposite directions. Tunnels display oval cross section and thick, mucus-lined wall. Cross sectional views or exhumed tunnels may show a laminar spreiten structure. Preserved as full reliefs.

Description--Shallow, U-shaped endichnial structures. Tunnels with oval cross section and distinctive wall, 0.6-1.6 mm thick. The wall is particularly evident in some collapsed, or exhumed structures (fig. 48A-B). Fill is similar to that of the host rock. Width of tunnel is 4.7-11.3 mm. Some exhumed shafts, protruding from the upper surface of sandstone beds, exhibit a cross sectional view with spreiten. Closely spaced, V-shaped markings cover the basal part of the structure. Some tunnels display a bilobed internal structure. Length of basal structures is 5.8-21.7 mm, but typically between 7.8 and 16.0 mm. Locally, chevrons appear grouped (fig. 49E-F). Many tunnels display chevron markings in one predominant orientation (fig. 49C, E, F), but careful examination commonly reveals V-shaped markings in opposite directions. Some structures exhibit two segments with chevrons oriented in opposite directions meeting at a central point (fig. 49A-B). In other specimens, V-shaped markings are superimposed at slightly different levels (fig. 49G), or a smooth segment connects oppositely directed chevrons (fig. 49D). Some tunnels merge into another specimen, resulting in successive branching (fig. 49C, E). The width of the joined tunnel may remain unaffected (fig. 49C) or may be increased considerably (fig. 49E). Crosscutting of traces on sandstone soles is common (fig. 49F-G). Traces occur in densely packed assemblages with tunnel orientations forming an angle of 20° to 45° relative to ripple crests (fig. 48A-C). When two orientations occur, they commonly are in relation to interference ripples on the upper surface.

Remarks--Mángano et al. (1998) discussed the role of the substrate in Protovirgularia morphology and assigned a wide range of chevroned structures to P. dichotoma. Further taxonomic analysis, however, suggests that two other ichnospecies are actually involved. We reassigned the studied material to P. rugosa and P. bidirectionalis. Protovirgularia bidirectionalis is a new ichnospecies that exhibits complex affinities with two different groups of bivalve structures, Protovirgularia and Solemyatuba. Although it originally was compared with Uchirites (Protovirgularia) triangularis by Maples and West (1990), Protovirgularia bidirectionalis is more closely related in constructional terms to P. longespicata, which was described by Seilacher and Seilacher (1994). Both forms have sharp, distinct chevrons, spreiten-like structure, and full-relief preservation. The chevrons of P. bidirectionalis, however, do not show the diagnostic papillar impressions that characterize P. longespicata, and they display opposite directions coexisting in the same structure. On the other hand, the shallow U-shaped form of the burrow and the oval cross section relate Protovirgularia bidirectionalis to Solemyatuba, which Seilacher (1990a) interpreted as a chemosymbiotic bivalve structure. The thick wall and apparent passive infill of Protovirgularia bidirectionalis indicate a mucus lining and that the structures were kept open by their occupants. Successive branching also suggests unfilled tunnels.

The oval cross section and V-shaped imprints of Protovirgularia bidirectionalis are the fingerprints of a protobranch bivalve tracemaker (Seilacher, 1990a; Seilacher and Seilacher, 1994). Protobranch bivalves are well known detritus and deposit feeders that exploit the uppermost tiers of the substrate (Stanley, 1970). No representative is known to be a suspension feeder or a chemosymbiont.

The preferred orientation of the structures relative to ripple crests may be related to a feeding strategy. As tidal currents flow in and out the shallow U-shaped burrows, they transport organic debris that is trapped in the mucus lining, to be subsequently grazed by the animal. The spreiten structure and chevrons facing opposite directions within a single structure indicate that the animal re-entered the tunnel successively. Considering the hazards of the intertidal area, the turnaround at the surface had to be performed during the slack-water period. During flood and ebb, the animal was protected within the structure. The angular orientation of burrows relative to current axis may have prevented scouring and may have increased the smooth inflow of detritus into the structure. This complex, bipolar pascichnial strategy may have resulted in a Teichichnus-like pattern (fig. 50).

Protoviguiaria rugosa (Miller and Dyer, 1878)

Fig. 51A-D

Figure 51--Protovirgularia rugosa. A. Dense assemblage of P. rugosa and associated resting traces on the upper surface of a sandstone bed. Note preservation as negative epireliefs in Chevronichnus-like fashion. KUMIP 288566. x 0.25. B. Close-up of some specimens in KUMIP 288566 showing sharp, V-shaped grooves and faint chevron impressions. x 0.5. C. Base of bed view of one specimen in KUMIP 288566, showing hypichnial preservation of P. rugosa and small Lockeia siliquaria. Chevron markings seem to lead toward the resting structure. x 1.16. D. Specimen with sharp chevrons. Direction of movement toward the upper left. Base of bed view. KUMIP 288569. x 1.16.

Specimens--Eight slabs (KUMIP 288523, KUMIP 288525, KUMIP 288526, KUMIP 288527, KUMIP 288543, KUMIP 288552, KUMIP 288566, KUMIP 288568) with 65 specimens.

Description--Horizontal to inclined structures crossing bedding planes. Morphological features are best recorded on bedding surfaces. Traces are straight to curved epichnial grooves or hypichnial ridges with chevron markings. Length is highly variable, some structures are only a couple of centimeters in length but others are considerably long, up to 194.7 mm (fig. 51A). Width is 1.7-12.8 mm, but typically 2.8-7.3 mm. In hypichnial preservation, the trace may be composed of a median ridge with well-developed, chevron-like lateral ridges (fig. 51D) or may display a more tubiform morphology with closely spaced, wrinkle-like chevrons (fig. 51C). Epichnial preservations have a prominent median groove and V-shaped imbricated sheets of sediment (fig. 51A-B). Distance between successive chevrons is 0.4-5.3 mm. V-angle is 60° to nearly 180°. Some structures are asymmetrical, with oblique to perpendicular markings only present on one side. Most specimens of Protovirgularia rugosa, including those with Chevronichnus-type preservation, begin or end in small specimens of Lockeia isp. or L. ornata.

Remarks--Hakes (1976) created Chevronichnus to describe chevron epichnial trails, which should be included in Protovirgularia and are described herein as epichnial occurrences of P. rugosa. Material herein assigned to P. rugosa is almost invariably associated to Lockeia-like structures. Some specimens of P. rugosa connected to L. ornata (Mángano et al., 1998, Fig. 4) are relatively short and represent classic examples of P. rugosa. Other specimens, however, can be interpreted at first approach as within the morphologic variability of P. dichotoma (fig. 66A, see also Mángano et al., 1998, Fig. 13C, D). Nonetheless, the association with Lockeia-like structures and the mode of occurrence indicate that they most likely represent escape traces and are better included in P. rugosa.

In many cases the producer of P. rugosa moved across bedding planes resulting in short structures that can be interpreted as escape traces. The great length of some specimens, however, indicates significant horizontal locomotion along bedding planes. A detailed observation suggests slow upward migration related to high rates of tidal current tractive sedimentation, rather than rapid escape movements after episodic deposition (i.e. storms). Although these structures are not easily interpreted as efficient fugichnia, they most likely represent structures keeping pace with tidal sedimentation. Interestingly, individuals of P. rugosa associated with tempestites, such as the type specimens from the Ordovician of Cincinnati, are shorter and mostly oblique to the bedding plane. It has been noted that vertical movements in bivalves require more energy than oblique movements (Brown and Trueman, 1991). Accordingly, vertical movements are most likely to be avoided by bivalves in the absence of episodic sedimentation.

At Waverly, nuculoid bivalves are the most likely trace makers of P. rugosa. Specimens of Protovirgularia rugosa var. Chevronichnus are particularly small in size and commonly display a gregarious mode of occurrence (fig. 51A) similar to that observed in the L. ornata / P. rugosa assemblage. Epichnial preservation of Lockeia prevents ichnospecific assignment of Lockeia. Nevertheless, the size of the structures is out of the typical range recorded for L. ornata (Mángano et al., 1998) and shape is more oval than the almond-like shaped L. ornata. None of these morphologic observations, however, completely eliminates the possibility of a population of juvenile tracemakers of Lockeia ornata. These specimens of Lockeia isp., however, may have been produced by an alternative tracemaker of smaller size (e.g., Nuculopsis, Mángano et al., 1998).

Ichnogenus Psammichnites Torell, 1870

Discussion--The taxonomy and internal structure of Psammichnites were clarified by Hofmann and Patel (1989), Seilacher and Gamez-Vintaned (1995, 1996), and McIlroy and Heys (1997), who documented its complex morphology. This ichnogenus typically consists of predominantly horizontal traces with transverse or arcuate internal structure and a distinct median dorsal structure. This dorsal structure commonly is represented by a sinusoidal or straight ridge/groove or regularly spaced circular mounds/holes (Mángano et al., in press).

A related form is Plagiogmus Roedel 1929. Plagiogmus is a complex endichnial structure, with different toponomic expressions (cf. McIlroy and Heys, 1997, fig. 7). Well-preserved specimens of Plagiogmus arcuatus exhibit four components: the basal "ladder trail," the internal backfill, the upper bedding surface "ribbon trail," and the lower surface arcuate structure (Walter et al., 1989; McIlroy and Heys, 1997). The internal structure of Plagiogmus arcuatus and Psammichnites gigas is strikingly similar (cf. Hofmann and Patel, 1989, fig. 5; McIlroy and Heys, 1997, fig. 7; Seilacher-Drexler and Seilacher, 1999, Fig. 8). The upper surface view of Plagiogmus arcuatus is hardly distinguishable from the upper surface of Psammichnites gigas (cf. Hofmann and Patel, 1989, fig. 3c; Walter et al., 1989, fig. 11c, d; McIlroy and Heys, 1997, fig. 5a-b). Mángano et al. (in press) noted that the "ladder trail" basal morphology, though commonly considered a diagnostic character of Plagiogmus, is a toponomic expression that may not be available in some preservational variants. Therefore, it should not be considered ethologically significant at the ichnogeneric level. Plagiogmus arcuatus is most likely a junior synomym of Psammichnites gigas (Mángano et al., in press).

Confusion persists regarding the taxonomic status of the ichnogenus Olivellites. Some authors retain Olivellites as a valid ichnotaxon (Miller and Knox, 1985; Fillion and Pickerill, 1990; Brownfield et al., 1998), but others place it in synonymy with Psammichnites (Chamberlain, 1971; Maples and Suttner, 1990; Seilacher-Drexler and Seilacher, 1999; Mángano et al., in press). Chamberlain (1971) was the first to place Olivellites in synonymy with Psammichnites, regarding its type ichnospecies as Psammichnites plummeri, but without discussing his reasons. Subsequently, Yochelson and Schindel (1978) reexamined the type specimens of P. plummeri, described additional topotypes, and analyzed specimens from a new locality in Texas. However, they apparently were unaware of Chamberlain's study, and therefore they did not address the taxonomic status of Olivellites. Mángano et al. (in press) concluded that Olivellites represents a variant of the Psammichnites-Plagiogmus behavioral pattern (cf. Seilacher, 1986, 1997, p. 38-39). The ichnogenus Psammichnites has nomenclatural priority over Olivellites and Plagiogmus and therefore Psammichnites is considered their senior synonym.

Meandering trails identical to traces subsequently referred to as Olivellites in the United States have been recorded in United Kingdom since the 19th century (e.g., Wood, 1851a, b; Binney, 1852; Dixon, 1852; Hancock, 1858; Tate, 1859). Eagar et al. (1985) and Pollard (1986) noted that the name "Crossopodia" has been traditionally used by geologists from the British Geological Survey (e.g., Bromehead et al., 1933; Stephens et al., 1953) to describe traces similar to P. plummeri. Mángano et al. (in press) reexamined the type specimens of Crossopodia McCoy (1851a,b) and concluded that this ichnogenus does not show the characteristic morphology of Psammichnites. McCoy (1851a,b) erected two ichnospecies: C. lata and C. scotica; the latter subsequently designated as the type species by Hantzschel (1962, p. W189). Benton and Trewin (1980) later reassigned McCoy type material of Crossopodia scotica to Dictyodora scotica, and suggested Crossopodia lata as the type of the ichnogenus Crossopodia. Reexamination of the type material of Crossopodia lata reveals that this ichnotaxon is a trilobate structure, displaying well-developed, subequallobes crossed locally by subtle transversal ridges (Mángano et al., in press). It is unclear whether the structure is preserved on the top or the sole of the bed. Crossopodia lata lacks the characteristic features of what was subsequently called "Crossopodia" in Great Britain. As summarized by Mángano et al. (in press), the confusing history of the different uses related to Crossopodia makes its abandonment the best alternative. The taxonomy of Carboniferous ichnospecies of Psammichnites was analyzed by Mángano et al. (2001b). These authors discussed three ichnospecies: P. plummeri (Fenton and Fenton, 1937), P. grumula (Romano and Melendez, 1979), and P. implexus (Rindsberg, 1994).

Psammichnites is interpreted as a grazing trace (pascichnion) that records the feeding activities of a subsurface vagile animal using a siphon-like device (Mángano et al., in press). Seilacher (1997, p. 38) stated that "the animal moved through the sediment like a submarine, being connected to the sediment surface only by a narrow snorkeL" Different tentative biological affinities have been proposed for Cambrian Psammichnites, including worms (Torell, 1868; Matthew 1888, 1890), annelids (McIlroy and Heys, 1997), echiurans (Runnegar, 1982), crustaceans (Torell, 1870), mollusks (Torell, 1870; Glaessner, 1969; McIlroy and Heys, 1997), and gastropods (Hantzschel, 1975). Recently, Seilacher-Drexler and Seilacher (1999) speculated that the producer of Psammichnites was probably related to halkieriids. Mángano et al. (in press) noted that evidence of a siphonlike device in Carboniferous Psammichnites restablishes the possibility of a molluscan trace maker.

Psammichnites is a common form in Lower Cambrian strata (e.g., Glaessner, 1969; Vortisch and Lindstrom, 1972; Hofmann and Patel, 1989; Walter et al., 1989; Pickerill and Peel, 1990; Goldring and Jensen, 1996; Seilacher, 1997; Alvaro and Vizcaino, 1999), then it reappears in the Silurian (A. Seilacher, written communication, 1999; Mángano and Buatois, unpublished data), having another prolific record in the Carboniferous, probably reaching the Permian (e.g., Yochelson and Schindel, 1978; Eagar et al., 1985; Devera, 1989; Martino, 1989; Buckman, 1992; Greb and Chesnut, 1994; Brownfield et al., 1998; Eyles et al., 1998). It has been invariably recorded in shallow-water deposits; Carboniferous ichnospecies are common in intertidal settings (Mángano et al., in press).

Psammichnites grumula (Romano and Melendez, 1979)

Fig. 52A

Figure 52--Ichnospecies of Psammichnites. A. Psammichnites grumula with well-developed holes along a median line and prominent levees on both sides of the trace. Base of bed view. KUMIP 288506. B. Psammichnites plummeri. Note central ridge and crenulated transverse ridges. Top of bed view. Field photo. C. Psammichnites implexus preserved on the top of a rippled sandstone bed. KUMIP 288507. x 0.27. D. Psammichnites implexus. Close-up of one of the specimens in C showing guided meanders. KUMIP 288507. Bar = 1 cm. E. Psammichnites? isp. with transverse ridges. Note associated, very small wrinkle marks. Top of bed view. KUMIP 288504. x 0.41. F. Psammichnites? isp. with poorly developed transverse ridges. Top of bed view. KUMIP 288522. x 0.48.

Specimen--One specimen on slab KUMIP 288506.

Description--Predominantly horizontal, meandering trace bearing a series of holes or mounds in median line. Holes are subcircular in cross section and conical in three dimensions. Median ridge is visible only locally. Transverse fine ridges or arcuate marks, recording meniscate backfill, are present. Prominent levees are formed on both sides of the trace, and these are particularly evident in the hypichnial preservation. Trail width is 16.0-17.2 mm. Marginal levees are 2.1-5.2 mm wide. Holes or mounds are 2.0-2.8 mm wide, up to 2.7 mm deep and 5.5-9.2 mm apart. Transverse ridges are 1.7-2.3 mm wide. Maximum length observed is 331.9 mm. Preserved as negative hyporelief.

Associated Ichnofauna--Cruziana problematica.

Remarks--Romano and Melendez (1979), who created the ichnospecies Olivellites grumula for two specimens from the Carboniferous of northwest Spain, followed Hantzschel (1975) and included Olivellites within the Scolicia group. The specimen from Kansas shares with the Spanish specimens the presence of holes or mounds along the axis of the trace, which is diagnostic of this ichnospecies. Additionally, like one of the traces from Spain, the specimen studied is preserved as a negative hyporelief. Only the specimen preserved in positive epirelief displays a distinct median ridge (Romano and Melendez, 1979, fig. 2.2). However, the ridge is hardly visible in the trace preserved as a negative hyporelief (Romano and Melendez, 1979, fig. 2.3). Similarly, the median ridge in a specimen of P. grumula from the Stull Shale Member is present only locally. Although Romano and Melendez (1979) stated that the specimens from Spain were meandering, illustrations show that the course of the traces is sinuous rather than meandering. In contrast, the specimen from Waverly clearly meanders. This difference, however, is not regarded as taxonomically significant. Romano and Melendez (1979) also described two hyporeliefs with flat trilobate morphology and faint oblique striations as Scolicia type A. This morphology suggests that observed in rare specimens of P. grumula and P. plummeri exhibiting the ventral surface. Buckman (1992, p. 230) included in Olivellites plummeri one specimen with "1 mm pimples along its midline, spaced approximately every 10 mm along the axis," which fits the diagnosis of Psammichnites grumula. Another specimen of P. grumula was recorded from the Coal Measures by Atkinson (1839). Additional recordings of this ichnospecies were documented by Mángano et al. (in press).

Psammichnites grumula differs from other Psammichnites ichnospecies by the presence of holes or protruding mounds. Additionally, the presence of well-developed, fine transverse ridges or arcuate marks distinguishes P. grumula from the nearly smooth P. implexus. In the midcontinent, morphologically transitional forms indicate the biological affiliation of P. plummeri and P. grumula. The presence of mounds and holes in P. grumula confirms the presence of a siphon. Psammichnites grumula is interpreted as produced by a deposit feeder using the siphon for respiration, aspiration, or for chemosymbiotic purposes (Mángano et al., in press).

Psammichnites implexus (Rindsberg, 1994)

Fig. 52C-D

Specimens--Four slabs (KUMIP 288507, KUMIP 288523, KUMIP 288531, KUMIP 288565) with nine specimens and several others examined in the field.

Description--Horizontal to subhorizontal traces with with a very faint meniscate structure and a sharp median ridge. Trace fill is similar to the host rock; meniscate internal structure is poorly preserved. The cross section is subtriangular to elliptical. Trace width remains relatively constant within specimens, but tends to broaden at turns. Tear-shaped resting structures are connected to some traces. Some specimens display a meandering tendency with phobotaxis and almost guided meanders. Other specimens show numerous self-crosscutting backturns and a strong tendency to scribble. Crosscutting instances are relatively common. Trace width is 3.8 to 5.9 mm. Ridge width is 0.7 to 0.8 mm. Preserved as full reliefs at the top of sandstones.

Associated Ichnofauna--Cruziana problematica typically is preserved on the soles of sandstones having P. implexus on the upper surfaces. Psammichnites implexus commonly occurs alone on upper surfaces of sandstone beds. In only one slab (KUMIP 288531), is P. implexus associated with Nereites missouriensis, Curvolithus simplex, Rosselia isp., and shafts of Lockeia siliquaria and Protovirgularia bidirectionalis.

Remarks--Rindsberg (1994) proposed Uchirites implexus for epichnial traces having a median ridge from the Mississippian of Alabama. He noted that this ichnospecies differs from the type species U. triangularis in having a scribbling tendency. However, re-examination of the type specimens of U. triangularis originally described by Macsotay (1967) from the Paleogene of Venezuela confirms preservation in positive hyporelief on turbidite soles. Restudy of type specimens by Mángano et al. (in press) suggests that preservation at the top of beds, presence of a median ridge, and the meandering tendency favor assignment of U. implexus to Psammichnites as a separate and distinctive ichnospecies, P. implexus. Specimens described by Binney (1852) as "trail of a mollusc" and "trail of a bivalve shell" were tentatively assigned to P. implexus by Mángano et al. (in press). Greb and Chesnut (1994) have recorded identical forms as Olivellites from the Pennsylvanian of Kentucky. Scolicia virgamontis Chamberlain, 1971, resembles P. implexus, but further analysis of the type specimens is needed (Mángano et al., in press).

Psammichnites implexus is similar to some specimens of Dictyodora, especially the ichnospecies Dictyodora scotica (McCoy, 1851a). The ichnogenus Dictyodora Weiss, 1884, consists of highly complex three-dimensional structures composed of a basal trace and a dorsal vertical wall (Hantzschel, 1975; Benton and Trewin, 1980; Benton, 1982a). Ichnospecies of Dictyodora, however, have walls that range in height from 10 to 180 mm (Benton and Trewin, 1980), display vertical to oblique striation, and are much higher than the median ridge of P. implexus (Mángano et al., in press). The dorsal cord of P. implexus represents a simpler structure than that present in Dictyodora. Moreover, the path of P. implexus commonly is more irregular than that of Dictyodora. Dictyodora commonly is preserved as an endichnial trace fossil, with contrasting sediment infill and elliptical cross sections. Sectioning of P. implexus shows a diffuse lower surface and a sandy sediment infill almost indistinguishable from the host rock in cross sectional view. Mángano et al. (in press) suggested that P. implexus is not a preservational variant of Dictyodora scotica. However, when preserved on a bedding plane, distinction between the two ichnotaxa may be difficult. Psammichnites implexus is regarded as a shallow-tier structure that records a less specialized strategy than Dictyodora (Mángano et al., in press).

Horizontal traces described by Han and Pickerill (1994a) as U. implexus in Devonian turbidites in eastern Canada are preserved as positive hyporeliefs and closely resemble the types of U. triangularis. Specimens from Venezuela do not meander as do some of the traces from eastern Canada, and locally they display faint lateral striae. As suggested by Han and Pickerill (1994a), the absence of striae in the Devonian traces may be preservational. Consequently, the specimens from Canada should be regarded as conspecific with U. triangularis. Nonetheless, the taxonomic status of Uchirites remains problematic, as exemplified by Seilacher and Seilacher (1994), who synonymized it with Protovirgularia. Psammichnites implexus is distinguished from the other two Psammichnites ichnospecies by its less well developed meniscate structure, its consistently smaller size, and its tendency to scribble. Additionally, it differs from P. grumula by the absence of holes or protruding mounds in the latter.

Rindsberg (1994, p. 10) considered several possible explanations for the scribbling tendency of P. implexus, including superficial siphon detritus feeding, turns to face shifting currents, and disturbance caused by parasitic infection. Swennen (1969) documented winding paths produced by the modern bivalve Macoma baltica that apparently were caused by trematode infestation. Biologicalor environmental stress (e.g., high temperatures) may better explain the departures from the typical meandering pattern.

Psammichnites plummeri (Fenton and Fenton, 1937)

Fig. 52B

Specimens--Two specimens recorded in the field.

Description--Predominantly horizontal, sinuous to meandering trails bearing a distinct median ridge, and fine, crenulated transverse ridges. Meniscate structure is not apparent in weathered parts of specimens. Cross sectional view subcircular to elliptical. Trace width is 140.5 to 180.5 mm. Median ridge is 1.7-1.9 mm wide. Transverse ridges are 0.9 to 1.6 mm wide. Preserved as full reliefs at the top of sandstones.

Associated Ichnofauna--No other traces were recorded.

Remarks--In a pioneering paper, Tate (1848) proposed the ichnospecies Crassopodia embletonia and Crassopodia media (error for Crossopodia McCoy) to name what he believed were body fossils of annelids. Tate type material is lost (J. Pollard, written communication, 2000), but reexamination of topotypes of Crossopodia embletonia indicates that this ichnotaxon displays all the diagnostic features of Psammichnites plummeri (Mángano et al., in press). Although the ichnospecies Psammichnites embletonia and P. media have priority over P. plummeri, Mángano et al. (in press) retained the more widely used P. plummeri to promote nomenclatorial stability. These authors regarded the second ichnospecies, C. media, as a nomen dubium.

Yochelson and Schindel (1978) analyzed the Psammichnites plummeri type specimen, as well as topotypes from the Wayland Shale Member of the Graham Formation (Pennsylvanian) and new specimens from another locality in Texas (Colony Creek Shale Member, Caddo Creek Formation). Their study provided details about the internal backfill structure and behavioral strategy. Although the internal structure of the Kansas specimens is less apparent, it closely resembles that of the type specimens from Texas.

Psammichnites plummeri is the most commonly encountered of the three Psammichnites ichnospecies (Mángano et al., in press). The presence of well-developed transverse ridges distinguishes P. plummeri from P. implexus. Psammichnites plummeri differs from P. grumula by the presence of holes or protruding mounds in the latter.

Psammichnites? isp.

Fig. 52E-F

Specimens--Four slabs (KUMIP 288504, KUMIP 288515, KUMIP 288517, KUMIP 288522) containing four specimens.

Description--Horizontal, sinuous to meandering trails with transverse ridges. Cross sectional view elliptical. Trace width is 18.8-40.4 mm. Maximum length observed is 295.0 mm. Transverse ridges are 2.0-4.0 mm wide. Preserved as full reliefs at the top of sandstones or, more rarely, as negative hyporelief.

Associated Ichnofauna--Specimens of Psammichnites? isp. preserved on the top of sandstone beds are associated with Palaeophycus tubularis, Lockeia siliquaria, and Protovirgularia bidirectionalis. The single specimen preserved on the base of a bed is associated with Cruziana problematica and Rusophycus isp.

Remarks--These specimens resemble Psammichnites in the presence of transverse ridges and their preservation as full reliefs at the top of sandstones or, more rarely, negative hyporelief. However, the absence of a median ridge precludes definitive placement of these specimens in Psammichnites.

Ichnogenus Rhizocorallium Zenker, 1836

Discussion--Rhizocorallium is distinguished from other U-shaped traces, such as Diplocraterion and Arenicolites, by its horizontal to oblique orientation. Sellwood (1970) suggested that the Rhizocorallium animal could be a deposit-feeder during trace construction and a suspension-feeder afterwards. Fürsich (1974c) pointed out differences between the various ichnospecies, regarding R. jenense as a dwelling trace of suspension feeders, and R. irregulare and R. uliarense as feeding traces of deposit feeders. Specimens studied by Basan and Scott (1979) did not show characteristics suggestive of a suspension-feeding habit for the Rhizocorallium animal, so they suggested a deposit-feeding habit. Horizontal orientation of the spreiten in specimens from Waverly points to a deposit-feeding strategy. Rhizocorallium is probably produced by crustaceans (Fürsich, 1974c).

Although more common in shallow-marine settings (e.g., Fraaye and Werver, 1990), Rhizocorallium is a facies-crossing trace, and it has been reported from deep-marine (e.g., Uchman, 1991), marginal-marine (e.g., Hakes, 1976), and, more rarely, nonmarine environments (e.g., Fürsich and Mayr, 1981). Examples of Rhizocorallium in tidal-flat facies have been recorded by Farrow (1966) and EI-Asa'ad (1987). It ranges in age from Cambrian to Miocene (Seilacher, 1955; Fürsich and Mayr, 1981).

Rhizocorallium irregulare Mayer, 1954

Fig. 53A-C

Figure 53--Rhizocorallium irregulare. A. Specimen with poorly preserved U trace. Top of bed view. Field photo. Pen is 150 mm long. B. Specimen oblique to the bedding plane. Poorly developed striations present in the tunnel arms. Base of bed view. KUMIP 288535. x 0.66. C. Specimen with well-developed spreiten. Note vertical Skolithos isp. cutting other structures. Base of bed view. KUMIP 288530. x 0.83.

Specimens--Two slabs (KUMIP 288530, KUMIP 288535) with two specimens and an additional one studied in the field.

Description--Endichnial, U-shaped trace parallel to slightly oblique to bedding plane. U-arms are nearly parallel and connected by spreiten. Thin striations perpendicular to arm axis are present locally. Arm width is 7.1-15.0 mm; maximum length observed is 120 mm. Spreiten are 9.5-27.0 mm wide.

Associated Ichnofauna--Cruziana problematica and Nereites imbricata.

Remarks--According to Fürsich (1974c), R. irregulare is distinguished from R. jenense and R. uliarense by its predominant horizontal orientation. Rhizocorallium mongraensis Chiplonkar and Ghare, 1975, R. karaiensis Chiplonkar and Ghare, 1979, R. kutchensis Ghare and Kulkarni, 1986, and R. lixianensis Zhang and Wang, 1996, are probably junior synonyms of R. irregulare.

Ichnogenus Rosselia Dahmer, 1937

Discussion--Rosselia includes concentrically filled, funnel- to cone-shaped traces (Frey and Howard, 1985). Monocraterion is morphologically similar, but it lacks the characteristic concentric fill. Cylindrichnus has a concentric fill, but does not exhibit a funnel-shaped morphology (Frey and Howard, 1981, 1985). Three ichnospecies currently are ascribed to Rosselia: R. socialis Dahmer, 1937, R. rotatus McCarthy, 1979, and R. chonoides Howard and Frey, 1984.

Nara (1995) recently completed a detailed analysis of Pleistocene Rosselia, and he interpreted it as dwelling structures (domichnia) of deposit-feeding terebellid polychaetes.

Rosselia is particularly abundant in shallow-marine environments (e.g., Howard and Frey, 1984; Frey and Howard, 1985; Fillion and Pickerill, 1990; Nara, 1995; Jensen, 1997). However, it also has been recorded in brackish-water (Rindsberg and Gastaldo, 1990) and deepmarine environments (Ksiazkiewicz, 1977). Rosselia ranges in age from Cambrian to Holocene (Jensen, 1997; Rindsberg and Gastaldo, 1990).

Rosselia socialis Dahmer, 1937

Fig. 54A-B

Figure 54--Rosselia socialis. KUMIP 288531. All illustrations are x 1.2. A. Top view of trace. B. Cross section view of the same specimen. C. Line drawing of trace as seen in cross section.

Specimens--Two slabs (KUMIP 288531, KUMIP 288552) each with one specimen.

Description--Irregularly conical to funnel-shaped, very thinly lined, vertical trace with flat to slightly convex top. A vertical to inclined, central to sub-central tube is present within the trace. Tunnel fill consists of poorly developed concentric layers. Diameter is 24.9-37.9 mm. Height is 32.5-40.1 mm. Preserved as endichnia.

Associated Ichnofauna--Arenicolites isp., Protovirgularia bidirectionalis, Lockeia siliquaria, and Curvolithus simplex.

Remarks--Rosselia socialis is distinguished from R. chonoides by the absence of helicoid swirls of sediment (Howard and Frey, 1984) and from R. rotatus by the absence of rotary twists of the trace (McCarthy, 1979).

Ichnogenus Rusophycus Hall, 1852

Discussion--We follow the majority of authors (e.g., Osgood, 1970; Crimes, 1975; Aceñolaza, 1978; Webby, 1983; Fillion and Pickerill, 1990; Pickerill, 1994, 1995; Bromley, 1990, 1996; Jensen, 1997) in considering Rusophycus as separate from Cruziana, contrary to Seilacher (1970). Isopodichnus, an ichnogenus commonly used for arthropod resting traces in continental facies, is considered a junior synonym of Rusophycus (see Bromley, 1990, 1996, for discussion).

Rusophycus historically has been interpreted as the resting trace (cubichnion) of trilobites, although it also is common in continental facies, where it is produced by other arthropods such as notostracans or amphipods (Bromley and Asgaard, 1972; Pollard, 1985). Osgood (1970) found the trilobite Flexicalymene meeki situated directly on Rusophycus pudicum from the Upper Ordovician of the Cincinnati area.

Rusophycus is a common component of shallow-marine assemblages (e.g., Osgood, 1970; Webby, 1983; Rindsberg, 1994; Benton and Hiscock, 1996; Jensen, 1997), but also has been recorded from continental (e.g., Bromley and Asgaard, 1972, 1979; Pollard, 1985; Aceñolaza and Buatois, 1993) and deep-marine environments (e.g., Pickerill, 1995). Examples of Rusophycus in tidal-flat deposits have been recorded by Narbonne (1984), Legg (1985), Durand (1985), Fillion and Pickerill (1990), Mángano et al. (1996), and Mángano and Buatois (2000). Rusophycus ranges in age from Cambrian to Miocene (Jensen, 1997; Gamez Vintaned et al., 1998).

Rusophycus isp.

Fig. 55A-B

Figure 55--Rusophycus isp. (arrow). Preserved at the base of beds. A. Bilobate specimen with poorly developed scratch marks. Note associated Cruziana problematica. KUMIP 288515. x 1.8. B. Specimen with clusters of endopodial scratches. Field photo. x 1.8.

Specimens--Two slabs (KUMIP 288505, KUMIP 288515) containing two specimens.

Description--Small hypichnial bilobed ridges, 14.8- 15.8 mm long and 5.8-6.8 mm width. The traces are divided in two segments approximately equal in length. The anterior (?) part shows conspicuous, almost transversal clusters of endopodial scratches. Individual scratches are indistinct, but the clusters are well differentiated. They are about 0.8-0.9 mm in length. The posterior (?) part of the trace is smooth with a thin external lobe about 0.9 mm in width.

Associated Ichnofauna--Cruziana problematica.

Remarks--Although the trace is slightly elongated, it shows the typical morphologic details of a resting structure, The poor preservation of scratches, however, makes it difficult to distinguish the front and the rear. The most distinctive features, transverse endopodal marks and pleural ridges, suggest affinities with Rusophycus pudicum Hall, 1852. Additionally, Rusophycus pudicum may exhibit an almost annulate appearance, generated by uneven concentration of scratches that closely resemble those observed in Rusophycus isp. Seilacher (1970) erected the Cruziana pudica group, characterized by strong, almost transversal endopodal scratches that are poorly individualized, and frequent genal or pleural marks. Seilacher (1970) noted that the Cruziana pudica group extends from the Lower Ordovician to the Carboniferous, and it includes several affiliated ichnospecies: C. pudica, C. balsa, C. retroplana, C. rhenana, and C. carbonaria. Rusophycus isp. differs from C. balsa and C. retroplana in general form and the presence of external lobes. Cruziana rhenana shows strong pleural ridges, but the endopodal scratches are separated by a wide axial groove, which is absent in Rusophycus isp. Although Rusophycus isp. resembles Rusophycus carbonarius in its elongated shape and scratch pattern, the latter does not display pleural lobes. Specimens morphologically very similar to Rusophycus isp. are widespread in Pennsylvanian deposits along Kansas Highway 166 in Chautauqua County, Kansas, where excellent preservation may allow identification to ichnospecies (Mángano and Buatois, unpublished observations).

Ichnogenus Skolithos Haldeman, 1840

Discussion--Skolithos consists of simple, unbranched, vertical burrows, and it is distinguished from Monocraterion by the funnel-shaped upper portion of the latter. A detailed discussion of the relationship between both ichnogenera was provided recently by Jensen (1997). Eight ichnospecies of Skolithos currently are accepted: S. linearis Haldeman, 1840; S. verticalis (Hall, 1843); S. serratus (Salter, 1864); S. magnus Howell, 1944; S. ingens Howell, 1945; S. annulatus (Howell, 1957b); S. bulbus Alpert, 1975; and S. gyratus Hofmann, 1979.

Skolithos is interpreted as dwelling structures (domichnia), with phoronids and annelids the most likely tracemakers in marine environments (Alpert, 1974).

Skolithos is known from several depositional environments, including continental (e.g., Fitzgerald and Barrett, 1986), marginal-marine (Ranger and Pemberton, 1988), shallow-marine (Rindsberg, 1994), and deep-marine settings (Crimes, 1977). Skolithos is common in high-energy zones of intertidal areas (e.g., Mángano et al., 1996). It ranges in age from Precambrian to Holocene (Fedonkin, 1985; Howard and Frey, 1975).

Skolithos isp.

Fig. 56A-B

Figure 56--Skolithos isp. (arrow). Preserved at the top of beds. A. Top of Skolithos burrows associated with shafts of Protovirgularia bidirectionalis. KUMIP 288530. x 0.42. B. Top of Skolithos isp. associated with wrinkle marks on ripple crest. KUMIP 288571. x 0.83.

Specimens--Four slabs (KUMIP 288530, KUMIP 288542, KUMIP 288558, KUMIP 288571) containing six specimens and several others recorded in the field.

Description--Vertical, unbranched, cylindrical, endichnial burrows preserved as protruding elements at the tops of beds. Diameter is 4.6-9.9 mm. Burrow walls are thinly lined and may exhibit corrugations. Burrow-fill typically is massive.

Associated Ichnofauna--Protovirgularia bidirectionalis, Curvolithus simplex, Lockeia siliquaria, and Nereites missouriensis.

Remarks--Absence of cross sectional views precludes a confident identification of the ichnospecies.

Ichnogenus Teichichnus Seilacher, 1955

Discussion--Teichichnus is similar to Diplocraterion in cross sectional view (Corner and Fjalstad, 1993). Although presence of a simple causative burrow is typically a diagnostic feature of Teichichnus that separates it from the U-shaped Diplocraterion, certain forms of Teichichnus display flattish U-shaped geometries that may be considered transitional with Diplocraterion (e.g., Corner and Fjalstad, 1993). Phycodes, a related icbnogenus, typically has a more complexly branched structure (Hantzschel and Reineck, 1968).

Teichichnus is a feeding structure (fodinichnion) of deposit feeders with the spreiten resulting from sediment mining (Seilacher, 1955; Hantzschel, 1975; Martino, 1989). Corner and Fjalstad (1993) favored an equilibrichnial origin for their specimens from the Holocene of Norway, in which the spreiten are produced to keep pace with an aggrading substrate. However, these Norwegian specimens seem to be more closely related to Diplocraterion than to Teichichnus. In all probability, many different animals produce Teichichnus, including annelids and arthropods (Hantzschel, 1975; Fillion and Pickerill, 1990). In modern environments, similar structures are produced by the polychaete Hedista (Nereis) diversicolor (Seilacher, 1957). Corner and Fjalstad (1993) suggested polychaete or sipunculan worms as trace makers for their Holocene specimens.

Teichichnus is a facies-crossing ichnotaxon, which has been recorded in marginal-marine (e.g., Clifton and Gingras, 1997), shallow-marine (e.g., Pemberton and Risk, 1982), and deep-marine environments (e.g., Ekdale and Berger, 1978). Teichichnus is relatively common in tidal-flat environments (e.g., Hakes, 1976; Chamberlain, 1980; Martino, 1989, 1996; Fillion and Pickerill, 1990; Mángano and Buatois, 1997; Stanley and Feldmann, 1998). It ranges in age from Cambrian to Holocene (Jensen, 1997; Wetzel, 1981).

Teichichnus rectus Seilacher, 1955

Fig. 57A-B

Figure 57--Teichichnus rectus. Both photos KUMIP 288500. A. Specimen preserved on top of a rippled bed. x 0.59. B. Cross sectional view of the same specimen showing retrusive spreiten and causative burrow. x 0.77.

Specimen--One specimen on a single slab (288500).

Description--Simple to flat U-shaped, horizontal, straight, unbranched, locally thickly lined trace having retrusive spreiten composed of vertically to subvertically stacked laminae. Causative burrow length is 88.9 rum. Causative burrow diameter is 5.4-6.5 rum. Spreite diameter is 7.6-8.9. Preserved as positive epirelief.

Associated Ichnofauna--Curvolithus simplex.

Remarks--Teichichnus is a candidate for taxonomic review, because its ichnospecies remain poorly understood (Frey and Howard, 1985; Jensen, 1997). The specimen from Waverly clearly belongs to T. rectus, an ichnospecies characterized by a vertical to subvertical, unbranched, retrusive spreite composed of a pile of gutter-shaped laminae (Fillion and Pickerill, 1990). Teichichnus pescaderoensis Stanton and Dodd, 1984, which differs from T. rectus only in its larger size, was regarded as a junior synonym by Fillion and Pickerill (1990). Teichichnus repandus Chamberlain, 1977 was placed in Rhizocorallium by Buckman (1994). Buckman (1992, 1996) and Schlirf (2000) considered T. ovillus Legg, 1985, as a junior synonym of T. rectus.

Ichnogenus Trichophycus Miller and Dyer, 1878a

Discussion--Originally described as a plant fossil by Miller and Dyer (1878a), Trichophycus subsequently was analyzed by Seilacher and Meischner (1965), Osgood (1970), Frey and Chowns (1972), Seilacher (1983), FiIlion and Pickerill (1990), Geyer and Uchman (1995), and Jensen (1997). Trichophycus is made up of a series of U-shaped trace segments having Teichichnus-like spreiten. Five ichnospecies have been defined: T. lanosus Miller and Dyer, 1878a, T. sulcatus Miller and Dyer, 1878b, T. venosus Miller, 1879, T. thuringicum Yolk, 1968, T. tripleurum Geyer and Uchman, 1995. Trichophycus sulcatus was considered an ichnospecies of Palaeophycus by Pemberton and Frey (1982) and synonymized with Halopoa imbricata by Uchman (1998). Osgood (1970) and Fillion and Pickerill (1990) considered T. lanosus to be an aberrant form of T. venosus. Although T. lanosus has priority, these authors retained T. venosus to maintain nomenclatural stability. Finally, Geyer and Uchman (1995) placed Phycodes pedum in Trichophycus, although Jensen (1997) considered P. pedum as an ichnospecies of Treptichnus. Trichophycus is in need of an extensive review and its relation with Halopoa should be evaluated.

Trichophycus is interpreted as a feeding trace (fodinichnia). Seilacher and Meischner (1965) and Seilacher (1983) considered trilobites the most likely tracemakers. Fillion and Pickerill (1990) suggested that worms also may produce similar structures, using their setae to produce the striae. Jensen (1997) noted that the scratch pattern of specimens from the Cambrian of Sweden suggests the digging apparatus of a priapulid worm.

Trichophycus is known from shallow-marine environments (e.g., Osgood, 1970; Seilacher, 1983; Fillion and Pickerill, 1990; Geyer and Uchman, 1995; Jensen, 1997). In particular, occurrences in tidal-flat facies have been recorded by Fillion and Pickerill (1990) and Geyer and Uchman (1995). It reportedly ranges in age from Cambrian to Carboniferous (e.g., Geyer and Uchman, 1995; Seilacher, 1983).

Trichophycus isp.

Fig. 58A-B

Figure 58--Trichophycus isp. Preserved at the base of beds. A. Specimen showing striations and Teichichnus-like spreite. KUMIP 288550. x 0.91. B. Specimen crosscutting a bivalve locomotion trace. KUMIP 288544. x 1.19.

Specimens--Three slabs (KUMIP 288544, KUMIP 288550, KUMIP 288561) containing three specimens.

Description--Sinuous or straight, predominantly horizontal, cylindrical systems consisting of short segments that deviate laterally from the main course of the tunnel. Longitudinal, parallel, fine striae are visible locally, particularly at the sides of the structure. Trace segments are partially preserved, but they tend to curve slightly upwards distally. Some incipient retrusive spreiten, formed by a few, flattened U-shaped laminae, were observed. Total length is 7.6-14.4 mm. Up to four segments have been recognized forming one structure. Segments are 28.9 to 40.7 mm in length. Tunnel diameter is 5.6-12.4 mm; the widest segments are strongly flattened. Tunnel fill is similar to host rock. Preserved as full reliefs on soles of sandstone beds.

Associated Ichnofauna--Protovirgularia bidirectionalis, Palaeophycus tubularis, and Halopoa isp. are the most common traces associated with Trichophycus isp.

Remarks--Partial preservation of the striae precludes ichnospecific assessment.

Chip-shaped Burrows

Fig. 59A-D

Figure 59--Chip-shaped burrows. A. Cluster of specimens (arrow) associated with Cruziana problematica. Base of bed view. KUMIP 288510. x 1.6. B. Specimens associated with Cruziana problematica. Note chip-shaped burrows preserved on the base of bed (arrow). KUMIP 288567. x 0.85. C. Cluster of chip-shaped burrows on the sole of a sandstone bed. KUMIP 288567. x 0.86. D. Specimens preserved as negative epirelief at the top of a sandstone bed (arrow). KUMIP 288567. x 0.85.

Specimens--Five slabs (KUMIP 288505, KUMIP 288510, KUMIP 288511, KUMIP 288546, KUMIP 288567) containing 74 specimens.

Description--Small, vertical, funnel-shaped burrows. Burrow fill structureless and similar to host rock. Upper section subcircular to oval, 2.6-7.5 mm in diameter. The lower tip of the structure is pointed, occasionally slightly flattened and folded toward one side (fig. 59A, C). The walls may be completely smooth or may display shallow, longitudinal, triangular grooves. Height is up to 8 mm on the bedding surface. Structures may cross more than one bed (fig. 59B). These burrows commonly occur in clusters of a few individuals (fig. 59A). Preserved as positive hyporeliefs (fig. 59A-C) or, more rarely, as negative epireliefs (fig. 59D).

Associated Ichnofauna--Chip-shaped burrows commonly are associated with Asteriacites lumbricalis and Cruziana problematica.

Remarks--These structures resemble very small plug-shaped burrows, but they are difficult to include in any established ichnogenus. Although they do not display a duodecimal symmetry, the presence of a well-developed apical structure allies them with Conostichus, particularly C. broadheadi Lesquereaux, 1880. The prominent longitudinal fluting of C. broadheadi, however, contrasts with the almost smooth surface of the Waverly specimens. Presence of relatively smooth walls suggests some affinities with Bergaueria. However, Bergaueria typically exhibits a shallow depression instead of a distinctive apical structure (Pemberton et al., 1988). Like many other Waverly ichnofossils, these tiny funnel-shaped structures have a wide range of preservational morphologies owing to substrate deformation related to fluidization.

Plug-shaped burrows currently are interpreted as resting or dwelling traces of sea anemones (Chamberlain, 1971; Pemberton et al., 1988). The small size of the Waverly burrows may indicate juvenile anemones.

Pelletoidal Chains

Fig. 60A-B

Figure 60--Pelletoidal chains. Preserved at the top of a rippled bed in KUMIP 288547. A. General view. x 0.47. B. Close-up showing internal pelletoidal structure. x 1.03.

Specimens--A single slab (KUMIP 288547) preserving tens of specimens.

Description--Small straight chains of pellets that cover the upcurrent side of ripple marks. The chains are more or less perpendicular to ripple crests, originating close to the top of the ripple and descend towards the trough. Chains are unbranched and subparallel, although they may crosscut each other. Chain length is up to 47.4 mm, and width is 0.7 to 1.0 mm. Very fine grained sandstone pellets are cylindrical in shape and about 1 mm in diameter. A fine-grained, darker-colored envelope surrounds the pellets.

Associated Ichnofauna--No other trace is associated with the pelletoidal chains.

Remarks--Pelletoidal chains show slight similarities with Microspherichnus linearis Hakes, 1976.

Small Horizontal Cylindrical Burrows

Fig. 61A-C

Figure 61--Small cylindrical horizontal burrows. Preserved at the base of beds. A. General view of specimens associated with Protovirgularia bidirectionalis. KUMIP 288531. x 0.65. B. Specimens associated with small vertical burrows. KUMIP 288500. x 2.5. C. Specimens showing branching at right angles. KUMIP 288500. x 2.5.

Specimens--Twenty slabs (KUMIP 288500, KUMIP 288511, KUMIP 288518, KUMIP 288523, KUMIP 288524, KUMIP 288527, KUMIP 288531, KUMIP 288532, KUMIP 288533, KUMIP 288534, KUMIP 288535, KUMIP 288538, KUMIP 288540, KUMIP 288544, KUMIP 288551, KUMIP 288555, KUMIP 288558, KUMIP 288565, KUMIP 288570, KUMIP 288571) containing several specimens, the actual number of which is impossible to assess.

Description--Predominantly horizontal, small, cylindrical burrows. Width is 0.6-1.7 mm. Cross section is subcircular. They typically occur as straight, short segments, less than 25.0 mm in length. The fill is essentially similar to the host rock, although carbonate cement may be more abundant within the burrow. Overcrossing of several individuals forming small isolated bunches is common. True branching in T's and Y's is rare. A few specimens curve. Preserved as full reliefs commonly on soles of sandstone beds.

Associated Ichnofauna-- These burrows commonly are associated with Asteriacites lumbricalis, Cruziana problematica, Protovirgularia bidirectionalis, Curvolithus multiplex, among many other forms.

Remarks--These small horizontal cylindrical burrows are abundant in several stratigraphic levels. In many cases, their presence seems to depend on preservation rather than ecologic causes. Small horizontal cylindrical burrows are easily differentiated from desiccation structures by their circular cross section and their hypichnial full relief preservation. Preferential concentration of carbonate cement within the tubes suggests the existence of a burrow microenvironment different from the surrounding conditions.

Although these traces may be roughly compared with Chondrites, they lack the regular branching and complex pattern of this ichnogenus (cf. Fu, 1991). Similar forms are Dendrotichnium llarenai Farres, 1967, and Dendrotichnium hantzscheli Farres, 1967. However, in both these ichnospecies, side branches diverge from a main stem.

Small horizontal burrows are most likely the work of worms, probably polychaetes. Polychaete worms are significant components of many recent and fossil tidal flats, where they construct a wide variety of simple and branching structures (e.g., Frey and Howard, 1975; Craig, 1977). Newell (1979) noticed the presence of small horizontal burrows produced by juvenile polychaetes in sand-flat deposits. Interestingly, the adults of these organisms produce mostly vertical structures in the mixed and the mud flat.

Small Vertical Burrows

Fig. 62A-C

Figure 62--Small vertical burrows. Preserved at the base of beds. A. Cluster of small vertical burrows. KUMIP 288552. x 1.4. B. Base showing several clusters of vertical burrows. KUMIP 288552. x 1.3. C. Vertical burrows crosscutting Lockeia ornata (arrow). KUMIP 288552. x 1.5.

Specimens--Ten slabs (KUMIP 288500, KUMIP 288510, KUMIP 288511, KUMIP 288516, KUMIP 288522, KUMIP 288533, KUMIP 288542, KUMIP 288552, KUMIP 288558, KUMIP 288574) with numerous specimens, the actual number of which cannot be determined.

Description--Small, vertical, unbranched, thinly lined burrows. Width is 0.8-2.2 mm. Cross section is subcircular. Fill is similar to the host rock. Several burrows occur together forming dense clusters. These small burrows often show an irregular distribution, being concentrated adjacent to or cutting other biogenic structures. Preserved as full relief or as positive or negative hyporeliefs.

Associated Ichnofauna--Small vertical burrows commonly are associated with Protovirgularia bidirectionalis, P. rugosa, Lockeia siliquaria, and Lockeia ornata. However, other ichnotaxa (e.g., Asteriacites lumbricalis, Cruziana problematica) also may be present.

Remarks--Small vertical burrows are very similar to the ichnogenus Pustulichnus Ekdale and Picard, 1985, described from Jurassic eolianites. However, Pustulichnus gregarius, its single ichnospecies, is larger than the Waverly specimens and does not form clusters.

These burrows are probably produced by polychaetes. Vertical polychaete structures are very common in modern tidal-flat environments (e.g., Howard and Dörjes, 1972; Frey and Howard, 1975; Craig, 1977; Newell, 1979).

Undetermined Tracks

Fig. 63

Figure 63--Undetermined tracks. Irregularly distributed tracks on the top of a rippled-sandstone bed. KUMIP 288533. x 0.56.

Specimens--Nine slabs (KUMIP 288519, KUMIP 288527, KUMIP 288533, KUMIP 288543, KUMIP 288549, KUMIP 288551, KUMIP 288555, KUMIP 288559, KUMIP 288568) with numerous specimens, the actual number of which cannot be determined.

Description--Isolated tracks consisting of elongate, scratch, or bifid imprints. Push-up mounds are present in some imprints. Imprint length is 1.5-5.6 mm. An internal continuous mark is observed locally. No clear trackway pattern is observed. Preserved as negative epireliefs on the tops of rippled sandstone beds.

Associated Ichnofauna--Curvolithus simplex, Protovirgularia bidirectionalis, and Chondrites? isp. are the most common structures associated with these tracks.

Remarks--The internal mark could record the dragging of a telson. Poor preservation and presence of isolated tracks rather than continuous trackways prevent ichnotaxonomic classification. Local presence of a telson trace and bifid imprints suggests similarities with the ichnogenus Kouphichnium Nopcsa, 1923, a xiphosurid trackway (Caster, 1938; Goldring and Seilacher, 1971).

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Kansas Geological Survey, Geology
Placed on web May 21, 2015; originally published 2002.
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