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Systematic Descriptions
All specimens recovered in this study are deposited with The University of Kansas Museum of Invertebrate Paleontology (KUMIP), Department of Geology, Lawrence, Kansas. Cores and outcrop localities are referred to by letter designations (see Fig. 1). Locations are given in Table 1, and distribution of conodonts in each core in the Appendix. OD=original designation; SD=subsequent designation.
[Conodont genera ending in -gnathus require that species names used in combination with it have terminations ending in -us, not -a. [Note: According to the International Code of Zoological Nomenclature, Article 30 (a),(3): "If a genus-group name is a Greek word latinized with a change of termination, it takes the gender appropriate to that termination." (Internatl. Comm. Zool. Nomencl., 1964).] Since copy had already been set in type, it was not feasible at this time to make the numerous appropriate corrections.]
Genus APATOGNATHUS Branson and Mehl, 1934
Apatognathus Branson & Mehl, 1934, p. 201.
Type species--Apatognathus varians Branson & Mehl, OD (1934, p. 201, pl. 17, fig. 1, 2, 3).
Diagnosis--Unit consisting of two sharply arched, parallel or slightly divergent denticulate limbs joined at apex by thin lamella on outer side; large, inward-curved apical denticle at point of arching breaks symmetry of arch. Denticles of limbs directed upward; limbs twisted slightly at their juncture.
Remarks--Species of Apatognathus are restricted to rocks of late Devonian and early Mississippian (Kinderhookian) age, except for three species found in late Mississippian (Meramecian) rocks. The gap in time of their occurrence has indicated possible homeomorphy with late Devonian-early Mississippian forms (Rexroad and Collinson, 1963). Therefore, the three Meramecian species described in the present study are placed within this genus with reservation.
Speciation of Mississippian forms is based on variations in denticulation of the limbs.
Distribution--Apatognathus has been identified from rocks ranging in age from late Devonian to early Mississippian and in rocks of early late Mississippian age.
APATOGNATHUS? GEMINA (Hinde)
Prioniodus geminus Hinde, 1900, p. 344, pl. 10, fig. 25.
Prioniodina? gemina (Hinde). Holmes, 1928, p. 19, pl. 5, fig. 10.
Apatognathus geminus (Hinde). Clarke, 1960, p. 4, pl. 1, fig. 1, 2; Thompson & Goebel, 1963, p. 12, fig. 3.
Apatognathus? gemina (Hinde). Rexroad & Collinson, 1963, p. 7, pl. 1, fig. 12-17.
Diagnosis--Apatognathid with one large denticle near mid-point of posterior limb approaching length of apical denticle; remaining denticles of both limbs of nearly uniform length, about half that of prominent denticle.
Remarks--The large denticle on the posterior limb distinguishes Apatognathus? gemina (Hinde) from A.? porcata (Hinde), which has denticles of nearly uniform length on both limbs.
Distribution--Apatognathus? gemina has previously been recovered from rocks of early late Meramecian age. In the present study four specimens were recovered from the St. Louis Limestone in Cores A and C.
Repository--KUMIP 1,800,076; KUMIP 1,800,136 (figured specimens).
APATOGNATHUS? PORCATA (Hinde)
Pl. 2, fig. 1; Pl. 4, fig. 23.
Prioniodus porcatus Hinde, 1900, p. 344, pt. 10, fig. 26; Holmes, 1928, p. 221, pl. 3, fig. 26.
Apatognathus porcatus (Hinde). Clarke, 1960, p. 5, pl. 1, fig. 3, 4.
Apatognathus porcata (Hinde). Rexroad & Collinson, 1963, p. 8, 1)1. 1, fig. 7-11.
Diagnosis--Apatognathid distinguished by denticles of nearly uniform length on both limbs. At maturity distinguished by increase in size of denticles toward apical denticle on one limb.
Remarks--Clarke (1960) distinguished Apatognathus? porcata (Hinde) by more lateral tumidity of the inner limb than found on A.? gemina (Hinde). The single large apical denticle and shorter uniform denticles on the posterior limb also characterize A.? porcata.
Distribution--Apatognathus? porcata has previously been recovered from rocks of early late Meramecian age. In the present study 29 specimens were recovered from the St. Louis Limestone in Cores A, B, C, D, and I.
Repository--KUMIP 1,800,104; KUMIP 1,800,336 (figured specimens).
APATOGNATHUS? n. sp. A Rexroad and Collinson
Apatognathus? n. sp. A Rexroad & Collinson, 1965, p. 5, pl. 1, fig. 1, 2.
Diagnosis--Sharply arched apatognathid?, denticles of limbs partly fused, long and needlelike, joined at top of arch by slightly longer apical denticle. Apical denticle often nearly indistinguishable from adjacent denticles of limb.
Remarks--No complete specimens of Apatognathus? n. sp. A Rexroad and Collinson have been recovered, and thus, the relative lengths of the two limbs are unknown. The denticles of this form are longer and more slender than those of A.? gemina (Hinde) or A.? porcata (Hinde), and are partially fused, whereas those of the latter two species are unfused throughout their lengths. The apical denticle of A.? n. sp. A is less distinct than in other species, and the symmetry of this form appears to be less than that of more typical Mississippian species. Rexroad and Collinson (1965) suggest that this species may be intermediate between forms of Synprioniodina and Apatognathus? gemina and A.? porcata, substantiating homeomorphy of late Mississippian forms with late Devonian-early Mississippian apatognathids. The lack of complete specimens, however, leaves this question open.
Distribution--Apatognathus? n. sp. A has been reported previously from rocks of early to early late Meramecian age. In the present study nine specimens were recovered from the Warsaw Limestone (Core K), Salem Limestone (Core C, D), and St. Louis Limestone (Core A).
Repository--KUMIP 1,800,133 (figured specimen).
Genus CAVUSGNATHUS Harris and Hollingsworth, 1933
Cavusgnathus Harris & Hollingsworth, 1933, p. 201.
Type species--Cavusgnathus alta Harris & Hollingsworth, OD (1933, p. 201, pl. 1, fig. 10a, b).
Diagnosis--Elongate platform with median longitudinal trough between high lateral parapet-like sides. Blade laterally located in plane of outer parapet and connected to anterior end of this parapet. Inner parapet terminating anteriorly approximately mid-length of inner surface of blade, separated from blade by median trough. Basal cavity generally, but not invariably, asymmetric, curved outward toward anterior end beneath posterior end of blade.
Remarks--The lateral position of the blade in Cavusgnathus distinguishes this genus from the form with a centrally located blade, Taphrognathus, from which the cavusgnathids were derived in late Meramecian time (Rexroad, 1958b). The cavusgnathids, in turn, gave rise in late Chesteran time to the adetognathodids (Lane, 1967), formerly identified as streptognathodids (Rexroad and Burton, 1961).
Speciation is based largely on the oral outline of the blade as determined by the size and arrangement of the blade denticles.
Distribution--Cavusgnathus has been identified from rocks ranging from late Meramecian to late Chesteran in age. Those forms previously identified as Cavusgnathus in the Pennsylvanian have been referred to Adetognathus by Lane (1967).
CAVUSGNATHUS ALTA Harris and Hollingsworth
Cavusgnathus alta Harris & Hollingsworth, 1933, p. 201, pl. 1, fig. 10a, b; Rexroad & Lane, 1966, p. 1391, text-fig. 1a, b.
Cavusgnathus cristata Branson & Mehl, 1941a, p. 177, pl. 5, fig. 26-31; Hass, 1953, p. 77, pl. 14, fig. 12-14; Elias, 1956, p. 115, pl. 2, fig. 1-6; Rexroad, 1958b, p. 16, pl. 1, fig. 15-17; Rexroad & Burton, 1961, p. 1151, pl. 138, fig. 16. (not) Cavusgnathus cristata Branson & Mehl. Cooper, 1947, p. 91, pl. 20, fig. 4-10; Bischoff, 1957, p. 19, pl. 2, fig. 7a, b.
Cavusgnathus cristata var. grandis Elias, 1956, p. 115,
1)]. 2, fig. 12-14.
Diagnosis--Cavusgnathid distinguished by irregular oral outline of blade, second posterior denticle commonly less than half length of first and third posterior denticles, and by bilateral symmetry of basal cavity.
Remarks--The illustrations by Cooper (1947) indicate that his specimens referred to Cavusgnathus cristata Branson and Mehl should be placed in C. navicula (Hinde). Ontogenetic stages studied by Rexroad (1958a) invalidate the establishment of C. cristata var. grandis Elias.
Rexroad and Lane (1966) demonstrated that C. cristata is a junior synonym of C. alta Harris and Hollingsworth and thus, all forms previously placed under C. cristata now belong to C. alta, the type species of the genus.
Distribution--Cavusgnathus alta has been recovered previously from rocks of early to late Chesteran age. In the present study six specimens were recovered from the St. Louis Limestone in Core B.
Repository--KUMIP 1,800,114 (figured specimen).
CAVUSGNATHUS CHARACTA Rexroad
Cavusgnathus characta Rexroad, 1957, p. 15, pl. 1, fig. 1; Rexroad & Collinson, 1963, p. 8, pl. 1, fig. 29.
Diagnosis--Cavusgnathid with distinctive notch located in outer parapet immediately posterior to juncture of blade to outer parapet.
Remarks--The characteristic notch in the outer parapet is considered by Rexroad and Collinson (1963) to be a primitive feature reflecting the transition from Taphrognathus to Cavusgnathus, the notch representing incomplete juncture of the blade to the anterior end of the parapet.
Distribution--Cavusgnathus characta has been recovered previously from rocks ranging in age from early late Meramecian to early Chesteran. In the present study six specimens were recovered from the St. Louis Limestone (Cores A, I) and the Ste. Genevieve Limestone (Core D).
Repository--KUMIP 1,800,222 (figured specimen).
CAVUSGNATHUS CONVEXA Rexroad
Cavusgnathus convexa Rexroad, 1957, p. 17, pl. 1, fig. 3-6; Rexroad, 1958b, p. 16, pl. 1, fig. 12-14; Rexroad & Burton, 1961, p. 1151, pl. 138, fig. 4a, b; Rexroad & Furnish, 1964, p. 670, pl. 111, fig. 1; Rexroad & Nicoll, 1965, p. 17, pl. 1, fig. 14, 15.
Diagnosis--Cavusgnathid with convex oral outline of blade, denticles longest approximately mid-point, shortening both anterior and posterior to mid-point of blade.
Remarks--The usual blade outlines found in cavusgnathids are either highest toward the posterior end, longest denticles at the posterior end of the blade as in C. unicornis Youngquist and Miller and C. navicula (Hinde), or the blade denticles are of nearly uniform length as in C. regularis Youngquist and Miller, C. characta Rexroad, and C. cristata Branson and Mehl. C. convexa Rexroad differs from the above configurations in that the longest denticles of the blade are located several denticles anterior to the posterior end of the blade. This oral outline closely resembles the blade outline of some specimens of Taphrognathus varians Branson and Mehl and may be a primitive character in cavusgnathids.
Distribution--Cavusgnathus convexa has been recovered previously from rocks ranging from early late Meramecian to late Chesteran in age. In this study 15 specimens were recovered from the St. Louis Limestone (Cores A, B, C, D, I, M, and N) and Ste. Genevieve Limestone (Core D).
Repository--KUMIP 1,800,105; KUMIP 1,800,266 (figured specimens).
CAVUSGNATHUS REGULARIS Youngquist and Miller
Cavusgnathus regularis Youngquist & Miller, 1949, p. 619, pl. 101, fig. 24, 25; Rexroad & Burton, 1961, p. 1152, pl. 138, fig. 13, 15; Rexroad & Collinson, 1963, p. 9, pl. 1, fig. 28; Rexroad & Furnish, 1964, p. 670, pl. 111, fig. 2; Rexroad & Nicoll, 1965, p. 18, pl. 1, fig. 16, 17.
Diagnosis--Cavusgnathid with short, stout shape, high platform, deep median trough, and short blade composed of denticles of either uniform length or gradually increasing length toward posterior end.
Remarks--The denticles of the blade of Cavusgnathus regularis Youngquist and Miller show a regular increase in length posteriorly, or form a nearly straight oral outline. Other species of Cavusgnathus have either an irregular oral outline of the blade as in C. cristata Branson and Mehl, a convex outline as in C. convexa Rexroad, or possess one or two denticles of much greater length than those adjacent as in C. unicornis Youngquist and Miller. C. characta Rexroad has a similar oral outline of the blade, but possesses a notch between the outer parapet and the blade.
Distribution--Cavusgnathus regularis has been recovered previously from rocks ranging in age from early late Meramecian to late Chesteran. In the present study 40 specimens were recovered from the St. Louis Limestone (Cores A, B, C, D, I, L, M, N, O) and the Ste. Genevieve Limestone (Core D).
Repository--KUMIP 1,800,080; KUMIP 1,800,115 (figured specimens).
CAVUSGNATHUS UNICORNIS Youngquist and Miller
Cavusgnathus unicornis Youngquist & Miller, 1949, p. 619, pl. 101, fig. 18-23; Rexroad, 1957, p. 17, pl. 1, fig. 7; Lys & Serre, 1957, p. 1042, pl. 2, fig. 3a, b; Rexroad, 1958b, p. 17, pl. 1, fig. 6-11; Rexroad & Burton, 1961, p. 1152, pl. 138, fig. 10-12; Rexroad & Collinson, 1963, p. 9, pl. 1, fig. 26, 27; Thompson & Goebel, 1963, p. 12, fig. 3; Rexroad & Furnish, 1964, p. 670, pl. 111, fig. 6; Rexroad & Nicoll, 1965, p. 18, pl. 1, fig. 18-20. (not) Cavusgnathus unicornis Youngquist & Miller. Higgins, 1961, pl. 10, fig. 3.
Diagnosis--Cavusgnathid distinguished by hornlike appearance of posterior denticle of blade, inclined strongly toward posterior, and by short, high platform.
Remarks--The posterior hornlike denticle on the blade of Cavusgnathus unicornis Youngquist and Miller is isolated from the long anterior blade denticles by a sequence of two or three short denticles of uniform length, and is distinctly inclined toward the posterior. The posterior denticle of the blade of C. navicula (Hinde) is the largest denticle of the blade, but is not inclined toward the posterior, and is succeeded anteriorly by a gradual decrease in denticle length. Rexroad and Burton (1961) suggested that C. unicornis is the ancestral form of Streptognathodus unicornis Rexroad and Burton. This form was later identified as Adetognathus unicornis (Rexroad and Burton) by Lane (1967).
Distribution--Cavusgnathus unicornis has been recovered previously from rocks ranging in age from early late Meramecian to late Chesteran. In this study 64 specimens were recovered from the St. Louis Limestone (Cores A, B, C, I, J, L, N) and the Ste. Genevieve Limestone (Core D).
Repository--KUMIP 1,800,116; KUMIP 1,800,332 (figured specimens).
CAVUSGNATHUS sp.
Description--In oral view, outer parapet slightly convex outward and slightly curved inward where joining straight blade; blade less than one-fourth free. Inner parapet straight, paralleling blade and outer parapet until just before posterior end, where it abruptly curves toward outer parapet. Both parapets weakly grooved transversely. Median trough deep and narrow toward anterior, disappearing short of posterior end of specimen, where inner parapet bends outward.
In lateral view, platform short, blade comprising over half total length of specimen on outer side. Upper margin of outer parapet slightly convex, that of inner parapet straight anterior half, slightly convex to posterior end. Blade with low, slightly convex to nearly straight oral margin bearing six compressed denticles, anterior two broadest antero-posteriorly. Denticles of blade of nearly uniform length.
In aboral view, posteriorly located, nearly symmetrical basal cavity just one-third total length of specimen. Inner lip flared laterally, extends slightly farther antero-posteriorly than outer lip. Cavity deepest near anterior end.
Remarks--The blade of this specimen is too long for Cavusgnathus regularis Youngquist and Miller and too straight orally for C. alta Harris and Hollingsworth. C. sp. may represent either a new species or a variation in the form of C. regularis
Distribution--One specimen of Cavusgnathus sp. was recovered from the St. Louis Limestone in Core C.
Repository--KUMIP 1,800,141 (figured specimen).
Genus GNATHODUS Pander, 1856
Gnathodus Pander, 1856, p. 33 (not Fieber, 1866).
Dryphenotus Cooper, 1939, p. 386.
Type species--Gnathodus mosquensis Pander. Monotype (1856, p. 33, pl. 2A, fig. 10a, b, c).
Diagnosis--Compound unit with deep, broad basal cavity at posterior end beneath platform. Oral surface of platform smooth to highly ornamented by nodes or ridges, divided longitudinally by denticulate carina extending to or near posterior end. Blade usually long and thin, extending anterior from platform.
Remarks--The posterior position of the basal cavity distinguishes Gnathodus from Spathognathodus, which has a sub-centrally located basal cavity.
Speciation is based on the size, shape, and ornamentation of the platform, all of which can be extremely variable.
Distribution--Gnathodus has been identified from rocks ranging from late Devonian to mid-Triassic in age.
GNATHODUS COMMUTATUS (Branson and Mehl)
Spathognathodus commutatus Branson & Mehl, 1941c, p. 98, pl. 19, fig. 1-4.
Gnathodus commutatus (Branson & Mehl). Bischoff, 1957, p. 22, pl. 14, fig. 2-15; Rexroad & Furnish, 1964, p. 671, pl. 111, fig. 3.
Gnathodus pellaensis Youngquist & Miller, 1949, p. 622, pl. 101, fig. 5.
Gnathodus inornatus Hass, 1953, p. 80, pl. 14, fig. 9-11.
Diagnosis--Gnathodid with unornamented circular platform at posterior end of long straight carinate blade. Basal cavity deep and circular in lateral outline. Carina terminates just short of posterior end of platform. Platform symmetrical, oral surface bisected by high narrow carina.
Remarks--The circular, symmetrical, unornamented platform distinguishes Gnathodus commutatus (Branson and Mehl) from other species of this genus.
Distribution--Gnathodus commutatus has been reported previously from rocks of late Meramecian and Chesteran age. In the present study, five specimens were recovered from the St. Louis Limestone in Cores A and B.
Repository--KUMIP 1,800,084; KUMIP 1,800,335 (figured specimens).
GNATHODUS GIRTYI? Hass
Gnathodus girtyi Hass, 1953, p. 80, pl. 14, fig. 22-24; Elias, 1956, p. 118, pl. 2, fig. 30, 31; Bischoff, 1957, p. 24, pl. 4, fig. 16-23; Higgins, 1961, p. 224, pl. 10, fig. 4; Dunn, 1965, p. 1148, pl. 140, fig. 2, 3, 12.
Diagnosis--Small gnathodid characterized by low, broad platform containing one row of nodes on either side of low carina, forming parapets. Parapets and carina extend nearly to posterior end of platform, where they merge.
Remarks--Several species are similar to Gnathodus girtyi Hass, and the ranges of these forms are imperfectly known. Therefore, this form is placed in G. girtyi with reservation. G. girtyi differs from G. antetexanus Rexroad and Scott in having two parapets, one on either side of the central carina. G. antetexanus has only one parapet, on the inner side. G. girtyi is a homeomorph of G. cuneiformis Mehl and Thomas, an Osagian form, and G. bassleri (Harris and Hollingsworth), an early Pennsylvanian form.
Distribution--Gnathodus girtyi has been recovered previously from rocks of early Chesteran age. In this study 12 specimens of G. girtyi? were recovered from the Warsaw Limestone (Core E) and the St. Louis Limestone (Cores A, B).
Repository--KUMIP 1,800,119; KUMIP 1,800,085 (figured specimens).
GNATHODUS TEXANUS Roundy
Gnathodus texanus Roundy, 1926, p. 12, pl. 2, fig. 7a, b, 8a, b; Branson & Mehl, 1941a, p. 173, pl. 5, fig. 23-25; Hass, 1953, p. 80, pl. 14, fig. 15-21; Elias, 1956, p. 110, pl. 3, fig. 32-36; Bischoff (part), 1957, p. 25, pl. 3, fig. 24, 25 only; Thompson & Goebel, 1963, p. 12, fig. 3; Burton, 1964, Chart [Burton, R.C., 1964, A preliminary range chart of Lake Valley Formation (Osage) conodonts in the southern Sacramento Mountains, New Mexico: New Mexico Geol. Soc., Guidebook 15th Field Conf., p. 73-75.]; Rexroad & Scott, 1964, p. 30, pl. 2, fig. 11-14; Rexroad & Collinson, 1965, p. 8, pl. 1, fig. 33-38.
Gnathodus texanus var. bicuspidus Roundy, 1926, p. 12, pl. 2, fig. 9a, b.
Gnathodus linguiformis Branson & Mehl, 1941b, p. 183, pl. 6, fig. 18-26.
Gnathodus pretexanus Elias, 1956, p. 115, pl. 3, fig. 9-11.
Diagnosis--Gnathodid distinguished by small, narrow platform ending short of posterior end on inner side. Only ornamentation is single prominent pillar-like parapet on inner side of platform, composed of one to three fused denticles.
Remarks--Rexroad and Scott (1964) identified Gnathodus antetexanus Rexroad and Scott as the direct ancestor of G. texanus Roundy, the latter arising through the reduction of the platform with subsequent enlargement and shortening of the inner parapet to the prominent pillar-like projection, and lengthening and compression of the anterior blade. Rexroad and Scott (1964) and Rexroad and Collinson (1965) regarded Spathognathodus deflexus Branson and Mehl to be like G. texanus in lacking the pillar-like parapet.
Distribution--Gnathodus texanus has been recovered previously from rocks ranging in age from late early Osagian to late early Meramecian. In the present study over 500 specimens were recovered from the Warsaw Limestone (Cores C, E, F, G, J, K, M, O), the Salem Limestone (Core H), the St. Louis Limestone (Cores D, I, L, N, O), and the Keokuk Limestone (Localities P and Q).
Repository---KUMIP 1,800,202; KUMIP 1,800,240 (figured specimens).
Genus HIBBARDELLA Ulrich and Bassler, 1926
Hibbardella Ulrich & Bassler, 1926, p. 37.
Type species--Prioniodus angulatus Hinde (1879, p. 360, pl. 15, fig. 17). SD Ulrich & Bassler (1926, p. 37).
Diagnosis--Unit consisting of prominent terminal denticle with straight, short, undenticulate posterior bar and two denticulate lateral processes, one inner and one outer. Whole unit roughly symmetrical through plane of terminal denticle and posterior bar.
Remarks--Hibbardella is similar to Ligonodina, with the addition of an outer-lateral process attached to the terminal denticle. The posterior bar is shorter and straighter in Hibbardella, and usually lacks denticles.
Speciation is based on the degree of downward and posterior projection of the lateral processes and on the size and length of the denticles on the lateral processes.
Distribution--Hibbardella has been identified from rocks ranging in age from Devonian to Pennsylvanian.
HIBBARDELLA ABNORMIS Branson and Mehl
Hibbardella abnormis Branson & Mehl, 1941b, p. 184, pl. 6, fig. 14; Rexroad & Collinson, 1963, p. 10, pl. 2, fig. 15, 18, 20, 21 ; Rexroad & Collinson, 1965, p. 9, pl. 1, fig. 8, 9.
Diagnosis--Hibbardellid characterized by steep downward arch of lateral processes (about 45 degrees), long discrete denticles of lateral processes, and broad aboral surface of posterior bar with shallow median groove to anterior end.
Remarks--Both lateral processes were broken off in the specimens described by Branson and Mehl (1941b). Their description of Hibbardella abnormis Branson and Mehl indicates that the lateral processes are greatly reduced. This description was emended by Rexroad and Collinson (1963) to include specimens with long, steeply inclined processes.
Distribution--Hibbardella abnormis has been recovered previously from rocks ranging from late Osagian to early late Meramecian age. In the present study 13 specimens were recovered from the St. Louis Limestone and Warsaw Limestone in Core O.
Repository--KUMIP 1,800,306 (figured specimen).
HIBBARDELLA FRAGILIS (Rexroad)
Trichonodella fragilis Rexroad, 1957, p. 40, pl. 4, fig. 6, 7.
Hibbardella fragilis (Rexroad). Rexroad & Burton, 1961, p. 1153, pl. 140, fig. 7. (not) Hibbardella fragilis Higgins, 1961, p. 213, pl. 12, fiq. 4, text-fig. 2.
Diagnosis--Hibbardellid characterized by long slender posterior bar and slender denticulate lateral processes bearing three slender denticles which become larger distally; downward angle of juncture of lateral processes about 120 degrees.
Remarks--At the present time, two conodont forms carry the name Hibbardella fragilis, one named by Rexroad (1957), and one by Higgins (1961). By the rule of priority, the second, that of Higgins, will have to be changed by the author who next publishes a description of that form.
Distribution--Hibbardella fragilis has been recovered previously from rocks of Chesteran age. In the present study six specimens were recovered from the Warsaw Limestone (Core M), Salem Limestone (Core I), and St. Louis Limestone (Core A).
Repository--KUMIP 1,800,213 (figured specimen).
HIBBARDELLA ORTHA Rexroad
Hibbardella ortha Rexroad, 1958b, p. 18, pl. 2, fig. 9-12; Clarke, 1960, p. 6, pl. 1, fig. 7; Rexroad & Burton, 1961, p. 1153, pl. 140, fig. 5, 6; Rexroad & Collinson, 1963, p. 10, pl. 2, fig. 12, 16; Rexroad & Furnish, 1964, p. 671, pl. 111, fig. 16; Rexroad & Collinson, 1965, p. 10, pl. 1, fig. 10; Rexroad & Nicoll, 1965, p. 19, pl. 1, fig. 12.
Prioniodus angulatus Hinde. Hinde (part), 1900, p. 343, pl. 10, fig. 18 only.
Hibbardella angulata (Hinde). Holmes (part), 1928, p. 11, pl. 5, fig. 32 only.
Diagnosis--Hibbardellid with thin, compressed lateral processes forming angle of about 140 degrees at basal juncture. Denticles of processes long, thin, and fused nearly to apices.
Remarks--The fragility of the lateral processes distinguishes Hibbardella ortha Rexroad from other hibbardellid species, which usually have more robust lateral processes. The fused denticles of the lateral processes also facilitate identification of this species.
Distribution--Hibbardella ortha has previously been recovered from rocks ranging in age from early Meramecian to late Chesteran. In this study 10 specimens were recovered from the Warsaw Limestone (Cores F, K, O), the Salem Limestone (Core D), and the St. Louis Limestone (Cores A, I).
Repository--KUMIP 1,800,286 (figured specimen).
Genus HINDEODELLA Ulrich and Bassler, 1926
Hindeodella Ulrich & Bassler, 1926, p. 38.
Type species--Hindeodella subtilis Ulrich & Bassler, OD (1926, p. 38, pl. 8, fig. 17-19).
Diagnosis--Unit consisting of long, straight bar containing small, straight, slender denticles often alternating in size, with larger terminal denticle at or near anterior end, and often with short aboral projection beneath terminal denticle.
Remarks--Specimens of Hindeodella are commonly found extremely fragmented and specific identification is usually impossible.
Distribution--Hindeodella has been identified from rocks ranging in age from Devonian to Triassic.
HINDEODELLA sp. indet.
Distribution--In this study over 25 specimens were recovered from the Warsaw, Salem, St. Louis, and Ste. Genevieve limestones in 12 cores and at both outcrop localities.
Genus HINDEODELLOIDES Huddle, 1934
Hindeodelloides Huddle, 1934, p. 48.
Type species--Hindeodelloides bicristatus Huddle, OD (1934, p. 48, pl. 7, fig. 2, 3, pl. 12, fig. 6).
Diagnosis--Unit consisting of thin, straight to gently curved denticulate posterior bar with major terminal denticle and sharply pointed aboral projection; overall form roughtly T-shaped. Denticles also found anterior to major denticle, extending part way down anterior edge of terminal denticle-aboral projection unit.
Remarks--The sharply pointed aboral projection distinguishes Hindeodelloides from Hindeodella. The anterior denticles on the aboral projection distinguish it from Neoprioniodus.
Speciation is based on the coarseness and general nature of the denticles on the posterior bar and aboral projection.
Distribution--Hindeodelloides has been identified from rocks of Kinderhookian, early Osagian, and late Meramecian age.
HINDEODELLOIDES BICRISTATUS Huddle
Hindeodelloides bicristatus Huddle, 1934, p. 48, pl. 7, fig. 2, 3, pl. 12, fig. 6; Elias, 1959, p. 157, pl. 2, fig. 28-30.
Diagnosis--Hindeodelloidid characterized by sharp aboral projection with approximately six closely spaced minute denticles on anterior edge, and by extremely small and closely spaced needlelike denticles on posterior bar.
Remarks--This species has been reported previously from rocks considerably older than those of the present study. Little significance can be drawn from this specimen at this time.
Distribution--Hindeodelloides bicristatus has been reported previously from rocks of Kinderhookian age. In the present study one specimen was recovered from the St. Louis Limestone in Core B.
Repository--KU 1,800,108 (figured specimen lost).
Genus LAMBDAGNATHUS Rexroad, 1958
New genus? Rexroad, 1957, p. 41.
Lambdagnathus Rexroad, 1958b, p. 19.
Type species--Lambdagnathus fragilidens Rexroad, OD (1958b, p. 20, pl. 6, fig. 10-16).
Diagnosis--Complex unit consisting of denticulate posterior bar and bladelike anterior and inner-lateral denticulate processes, with apical denticle at juncture of three processes. Triangular basal cavity located beneath apical denticle at aboral juncture of three processes.
Remarks--The triangular basal cavity of Lambdagnathus distinguishes it from Centrognathus, a similar form with a circular basal cavity.
This genus is presently monospecific.
Distribution--Lambdagnathus has been identified from rocks ranging in age from late Meramecian to late Chesteran.
LAMBDAGNATHUS FRAGILIDENS Rexroad
New genus, Rexroad (part), 1957, p. 41, pl. 4, fig. 10 only.
Lambdagnathus fragilidens Rexroad, 1958b, p. 19, pl. 6, fig. 10-16; Rexroad & Burton, 1961, p. 1154, pl. 141, fig. 18; Rexroad & Furnish, 1964, p. 672, pl. 111, fig. 35; Rexroad & Nicoll, 1965, p. 21, pl. 2, fig. 9.
Diagnosis--Lambdagnathid with triangular intersection of three processes, two in one plane, the third one inclined downward. Basal cavity triangular in outline, lying directly beneath terminal denticle at juncture of the three processes.
Remarks--Lambdagnathus fragilidens Rexroad is the only species assigned to this genus.
Distribution--Lambdagnathus fragilidens has been previously recovered from rocks ranging from early late Meramecian to late Chesteran age. In this study four specimens were recovered from the St. Louis Limestone in Core 1.
Repository--KUMIP 1,800,229 (figured specimen lost).
Genus LIGONODINA Ulrich and Bassler, 1926
Ligonodina Ulrich & Bassler, 1926, p. 12.
Type species--Ligonodina pectinata Ulrich & Bassler, OD (1926, p. 13, pl. 2, fig. 9, 10).
Diagnosis--Unit consisting of major terminal denticle at point of juncture of long, thin, straight denticulate posterior bar and downward and posteriorly curved denticulate inner-lateral process.
Remarks--Ligonodina is similar to Hibbardella, except that it possesses only one lateral process instead of two.
Speciation is based on the size, direction, and degree of curvature of the inner-lateral process.
Distribution--Ligonodina has been identified from rocks ranging from Devonian to Pennsylvanian in age.
LIGONODINA LEVIS Branson and Mehl
Ligonodina levis Branson & Mehl, 1941b, p. 185, pl. 6, fig. 10; Bischoff, 1957, p. 30, pl. 5, fig. 8, 9, pl. 6, fig. 25: Rexroad & Burton, 1961, p. 1154, pl. 141, fig. 7, 8; Rexroad & Collinson, 1963, p. 11, pl. 2, fig. 24, 25; Thompson & Goebel, 1963, p. 12, fig. 3-1 Rexroad & Furnish, 1964, p. 672, pl. 111, fig. 38; Rexroad & Collinson, 1965, p. 10, pl. 1, fig. 23, 24; Rexroad & Nicoll, 1965, p. 21, pl. 2, fig. 24.
Ligonodina obunca Rexroad, 1957, p. 32, pl. 1, fig. 22, 23; Rexroad, 1958b, p. 21, pl. 3, fig. 7, 8. (not) Ligonodina obunca Rexroad. Higgins, 1961, p. 225, pl. 11, fig. 9.
Ligonodina sp. Youngquist & Miller (part), 1949, p. 620, pl. 101, fig. 12, 13 only.
Diagnosis--Ligonodinid characterized by curved delicate inner-lateral process forming approximately 45-degree angle to direction of posterior bar as seen from inner side. From anterior, lateral process forms angle of 120 degrees with terminal denticle. Terminal denticle slender and long, moderately arched toward posterior.
Remarks--The posterior curvature of the lateral process distinguishes Ligonodina levis Branson and Mehl from L. roundyi Hass, in which the lateral process curves strongly aborally, but curves only slightly toward the posterior, and from L. sp. A, in which the lateral process nearly parallels the posterior bar.
Distribution--Ligonodina levis has been recovered previously from rocks ranging in age from late Osagian to late Chesteran. In the present study over 40 specimens were recovered from the Warsaw Limestone (Cores F, K, M), the Salem Limestone (Cores C, D, I), the St. Louis Limestone (Cores (A, B, C, D, M, N, O), the Ste. Genevieve Limestone (Cores B, D), and the Keokuk Limestone (Locality P).
Repository--KUMIP 1,800,143; KUMIP 1,800,109 (figured specimens).
LIGONODINA ROUNDYI Hass
Ligonodina roundyi Hass, 1953, p. 82, pl. 15, fig. 5-9; Elias, 1956, p. 126, pl. 5, fig. 10-14; Rexroad, 1958b, p. 21, pl. 3, fig. 1-4; Stanley, 1958, p. 468, pl. 68, fig. 3, 4.
Diagnosis--Ligonodinid distinguished by lateral process directed sharply downward approximately 90 degrees from posterior bar with little or no posterior curvature. Denticles of lateral process straight and long.
Remarks--The lateral process of Ligonodina roundyi Hass is larger than that of L. levis Branson and Mehl, and curves aborally with a greater angle. L. roundyi closely resembles L. tenuis Branson and Mehl, but the lateral process of the former is heavier and curves to the posterior with a greater angle. L. roundyi also has larger denticles on the lateral process than does L. tenuis.Distribution--Ligonodina roundyi has been recovered previously from rocks of early Chesteran age. In the present study 15 specimens were recovered from the Warsaw Limestone (Cores E, F), and the St. Louis Limestone (Cores A, B, I, N, O).
Repository--KUMIP 1,800,231; KUMIP 1,800,110 (figured specimens).
LIGONODINA sp. A
Description--Short, laterally compressed apical denticle curved sharply posteriorly, upper half nearly paralleling small posterior bar beneath it. Posterior bar broken near terminal denticle, but is small in diameter and length. Lateral process relatively large, directed outward and downward, curving slightly toward anterior near terminus. Lateral process with only one large curved denticle directed slightly toward posterior, process sharply pointed at distal end. Aboral surface of unit triangular in outline beneath apical denticle; basal pit small and indistinct.
Remarks--This form is small. The extreme posterior curvature of the apical denticle and relatively large size of the lateral process distinguishes Ligonodina sp. A from L. levis Branson and Mehl, which has a nearly straight apical denticle, and from L. roundyi Hass, which has a large downward-curving lateral process.
Distribution--Two specimens of Ligonodina sp. A were recovered from the St. Louis Limestone in Cores A and B.
Repository--KUMIP 1,800,121 (figured specimen).
LIGONODINA n. sp.
Description--Unit with straight, narrow posterior bar possessing several minute discrete denticles. Terminal denticle long and slender, bowed slightly toward posterior. Inner-lateral process extends first directly anterior of terminal denticle, then bends 90 degrees inward beneath first slightly curved denticle of inner-lateral process. Lateral process possesses several slightly curved discrete denticles, and has little or no aboral deflection, lying nearly in plane of posterior bar. Small basal cavity located beneath terminal denticle at juncture of this denticle with posterior bar.
Remarks--Ligonodina n. sp. differs from previously described species of this genus in the initial anterior direction of the inner-lateral process, and in the near horizontality of this process as seen in lateral view. This form has been recovered from the St. Louis Limestone in St. Louis County, Missouri (Thompson, 1966).
Distribution--Three specimens of Ligonodina n. sp. were recovered in the present study from the St. Louis Limestone in Cores A and B.
Repository--KUMIP 1,800,117; KUMIP 1,800,083 (figured specimens).
Genus LONCHODINA Ulrich and Bassler, 1926
Lonchodina Ulrich & Bassler, 1926, p. 30.
Type species--Lonchodina typicalis Ulrich & Bassler, OD (1926, p. 31, pl. 5, fig. 1, 2).
Diagnosis--Unit consisting of denticulate bar arched at position of subcentral circular basal cavity. Denticles discrete and irregular in length; apical denticle above basal cavity not always distinguishable from other denticles.
Remarks--The two limbs anterior and posterior of the apical denticle are distinctly barlike showing little lateral compression. This distinguishes Lonchodina from Elictognathus and Ozarkodina, which have highly compressed bladelike limbs. The basal cavity of Bactrognathus is much broader, and bactrognathids do not contain an apical denticle.
Speciation is based on the degree of arching of the two limbs, the lateral angle between the limbs, the relative size of the apical denticle, and the shape of the basal cavity.
Distribution--Lonchodina has been identified from rocks ranging in age from Devonian to Pennsylvanian.
LONCHODINA PARACLARKI Hass
Lonchodina paraclarki Hass, 1953, P. 83, pl. 16, fig. 15, 16; Elias, 1956, p. 122, pl. 5, fig. 6, 7; Stanley, 1958, p. 468, pl. 67, fig. 1.
Diagnosis--Lonchodinid with long, curved, heavy apical denticle, small anterior and posterior bars meeting with small lateral angle and slight downward arch. Large, deep triangular basal cavity, beneath apical denticle, has highly flared outer lip and only slightly flared inner lip.
Remarks--The majority of specimens of Lonchodina paraclarki Hass recovered in the present study retain only the stumps of the anterior and posterior processes, with one or two denticles near the apical denticle remaining. These specimens are identified by the lateral angle at the juncture of the two processes and by the large outward flaring, triangular basal cavity. L. furnishi Rexroad has no appreciable lateral angle between the two limbs, and is more highly arched downward. The anterior and posterior limbs are smaller than those of L. paraclaviger Rexroad.
Distribution--Lonchodina paraclarki has been recovered previously from rocks of early Chesteran age. In the present study 20 specimens were recovered from the Warsaw Limestone (Cores J, K, M, O) and the Keokuk Limestone (Localities P and Q).
Repository--KUMIP 1,800,244 (figured specimen).
LONCHODINA PARACLAVIGER Rexroad
Lonchodina paraclaviger REXROAD, 1958b, p. 22, pl. 4, fig. 7-10.
Diagnosis--Lonchodinid with large anterior limb inclined outward from line of smaller posterior limb. Denticles of anterior limb large, those of shorter posterior limb smaller. Basal cavity located directly beneath large apical denticle; triangular in outline, with straight outer margin and sharply flared inner lip.
Remarks--The anterior limb is larger than the posterior limb in Lonchodina paraclaviger Rexroad, and the denticles of the anterior limb are large relative to the large apical denticle. The anterior denticles of L. furnishi Rexroad and L. paraclarki Hass are smaller, and do not as closely approximate the apical denticle in size.Distribution--Lonchodina paraclaviger has been recovered previously from rocks of early Chesteran age. In the present study two specimens were recovered from the Warsaw Limestone in Core K.
Repository--KUMIP 1,800,245 (figured specimen).
Genus MAGNILATERELLA Rexroad and Collinson, 1963
Lonchodina? Ulrich & Bassler. Branson & Mehl, 1941a, p. 171; Youngquist & Miller, 1949, p. 620; Bischoff (part), 1957, p. 34.
Ligonodina? Ulrich & Bassler. Branson & Mehl, 1941a, p. 171.
Genus indeterminate Rexroad, 1957, p. 42; Rexroad, 1958b, p. 26.
Genus Novum? clarke, 1960, p. 15.
New Genus? Rexroad & Jarrell, 1961, p. 2014.
Magnilaterella Rexroad & Collinson, 1963, p. 11.
Type species--Magnilaterella robusta Rexroad & Collinson, OD (1963, p. 14, pl. 1, fig. 4, 5, 9; Text-fig. 3A, B, C, 4A, B, C, D, E, F).
Diagnosis--Unit consisting of small denticulate posterior bar and large denticulate inner-lateral bar. Lateral bar contains largest denticle, near midlength. Basal cavity near anterior end of posterior bar, at juncture with lateral bar, and extends as grooves along lower surface of either bar.
Remarks--The basal cavity is at the point of juncture of the two bars in Magnilaterella, beneath the terminal denticle in Ligonodina. Cladognathodus possesses anterior, posterior, and lateral bars, and specimens missing the anterior bar closely resemble Magnilaterella, except that the posterior bar usually contains only one denticle, while Magnilaterella has two or more on the posterior bar. Lambdagnathus with a missing anterior bar can easily be mistaken for a magnilaterellid.
Speciation is based on the size of the lateral bar and the number of major denticles on that bar.
Distribution--Magnilaterella has been identified from rocks of Meramecian and Chesteran age.
MAGNILATERELLA ROBUSTA Rexroad and Collinson
Lonchodina sp. Branson & Mehl (part), 1941a, p. 171, pl. 5, fig. 10 only.
Metalonchodina? sp. Elias, 1956, p. 124, pl. 4, fig. 3.
Genus indeterminate Rexroad (part), 1957, p. 42, pl. 4, fig. 19-21 only; Rexroad, 1956b, p. 26, pl. 5, fig. 1, 2.
New genus? sp. Rexroad & Liebe. (part), 1962, p. 511.
Magnilaterella robusta Rexroad & Collinson, 1963, p. 14, pl. 1, fig. 4, 5, 9, text-fig. 3A, B, C, 4A, B, C, D, E, F; Rexroad & Furnish, 1964, p. 673, pl. 111, fig. 27-31; Rexroad & Nicoll., 1965, p. 22, pl. 1, fig. 10, 11.
Diagnosis--Magnilaterellid characterized by relatively short and thick arched inner-lateral process bearing two or three major denticles with small, straight posterior bar bearing one or more minor denticles. Largest denticle on lateral bar near midpoint of bar. Grooved basal surface broad, extending half way up posterior surface of inner-lateral process.
Remarks--Many fragments of conodonts were recovered that could belong to Magnilaterella, but identification was usually impossible with any surety. M. robusta Rexroad and Collinson has two or more major denticles on the lateral bar, while M. complectens (Clarke) possesses only one, with two minor denticles. M. recurvata (Bischoff) has a thinner and longer inner-lateral bar than M. robusta.
Distribution--Magnilaterella robusta has been recovered previously from rocks ranging from early Meramecian to late Chesteran age. In the present study six specimens were recovered from the Warsaw Limestone (Core F) and the St. Louis Limestone (Cores A, B, D).
Repository--KUMIP 1,800,122; KUMIP 1,800,092 (figured specimens).
Genus NEOPRIONIODUS Rhodes and Müller, 1956
Prioniodus Pander (part), 1856, p. 30. Neoprioniodus Rhodes & Müller, 1956, p. 698.
Type species--Prioniodus conjunctus Gunnell, SD (1931, p. 247, pl. 29, fig. 7) Rhodes & Müller (1956, p. 698).
Diagnosis--Unit consisting of large, straight to curved terminal denticle with distinct aboral projection and denticulate, straight to downward-curving posterior bar. Oval basal cavity located at aboral juncture of aboral process and posterior bar.
Remarks--Neoprioniodus lacks a lateral bar, has only one posterior bar, and thus differs from Ligonodina. The aboral projection is not denticulated, thus distinguishing Neoprioniodus from Hindeodelloides and Synprioniodina.
Speciation is based on the shape and prominence of the terminal denticle, length and width of the aboral projection, length, curvature, and denticulation of the posterior bar, and size and degree of lateral flaring of the basal cavity.
Distribution--Neoprioniodus has been identified from rocks ranging in age from Devonian to Pennsylvanian.
NEOPRIONIODUS ACAMPYLUS Rexroad and Collinson
Neoprioniodus acampylus Rexroad & Collinson, 1965, p. 11, pl. 1, fig. 25-27.
Diagnosis--Small neoprioniodid laterally unbowed except for terminal fang. Aboral projection long; posterior bar forms angle of about 55 degrees with aboral projection. Denticles of posterior bar small and deeply inserted.
Remarks--Neoprioniodus acampylus Rexroad and Collinson is similar to N. camurus Rexroad. However, the former is laterally unbowed, while the latter is very strongly bowed immediately posterior to the terminal denticle. The denticles of N. camurus are not deeply inserted as in N. acampylus.
Distribution--Neoprioniodus acampylus has previously been recovered from rocks of early Meramecian age. In the present study one specimen was recovered from the Warsaw Limestone in Core F.
Repository--KUMIP 1,800,190 (figured specimen).
NEOPRIONIODUS CAMURUS Rexroad
Neoprioniodus camurus Rexroad, 1957, p. 34, pl. 2, fig. 8, 9, 14; Rexroad, 1958b, p. 23, pl. 5, fig. 5, 6; Rexroad & Burton, 1961, p. 1155, pl. 140, fig. 11; Rexroad & Furnish, 1964, p. 674, pl. 111, fig. 32; Rexroad & Nicoll, 1965, p. 23, pl. 2, fig. 19, 20.
Diagnosis--Neoprioniodid characterized by short, slender terminal denticle with straight, long and narrow aboral projection. Posterior bar very long, laterally bowed, compressed, and straight, with numerous small subequal denticles. Angle between aboral projection and posterior bar sharp, nearly 45 degrees.
Remarks--The posterior bar of Neoprioniodus camurus Rexroad is more highly curved aborally, contains more equal-sized denticles, and has a larger aboral projection than N. loxus Rexroad. It is generally smaller and has a smaller basal cavity than N. tulensis (Pander) and N. varians (Branson and Mehl), and has a smaller basal cavity than N. cassilaris (Branson and Mehl).
Distribution--Neoprioniodus camurus has previously been recovered from rocks of late Meramecian and late Chesteran age. In this study four specimens were recovered from the Warsaw Limestone (Cores F, G), and the St. Louis Limestone (Core A).
Repository--KUMIP 1,800,191; KUMIP 11800,093 (figured specimens).
NEOPRIONIODUS sp. cf. N. CASSILARIS (Branson and Mehl)
Prioniodus cassilaris Branson & Mehl, 1941b, p. 186, pl. 6, fig. 11, 12, 15, 17; Youngquist, Müller, & Downs, 1950, p. 528, pl. 67, fig. 23, 24.
Prioniodina cassilaris (Branson and Mehl). Bischoff, 1957, p. 47, pl. 5, fig. 38, 39.
Neoprioniodus cassilaris (Branson & Mehl). Elias, 1959, p. 153, pl. 2, fig. 17-21.
Description--Unit of small size with wide lateral flare to large basal cavity. Basal cavity located in broad aboral projection of terminal denticle. Posterior bar short, slightly arched aborally, with small number of large denticles.
Remarks--Rexroad and Collinson (1963) consider Neoprioniodus cassilaris (Branson and Mehl) to be a synonym of N. tulensis (Pander), because of the variability in the former illustrated by Branson and Mehl (1941b). The specimens recovered in the present study are similar to N. tulensis except for their small size, which appears to be a consistent feature, and not one of immaturity. For this reason, these specimens are here referred to N. cassilaris.
Distribution--In the present study five specimens of Neoprioniodus sp. cf. N. cassilaris were recovered from the Warsaw Limestone in Core K.
Repository--KUMIP 1,800,246(figured specimen).
NEOPRIONIODUS LIGO (Hass)
Prioniodus peracutus Roundy, 1926 (part), p. 10, pl. 4, fig. 7, 8 only.
Prioniodus ligo Hass, 1953, p. 87, pl. 16, fig. 1-3; Elias, 1956, p. 109, pl. 2, fig. 16-18; Elias, 1959, p. 150, pl. 2, fig. 12-14.
Diagnosis--Neoprioniodid with short, narrow, terminal denticle, broader at base than aboral projection is at top. Aboral projection long, nearly as long as terminal denticle, and sharply pointed, with small indistinct basal cavity. Posterior bar long, thin, projecting from terminal denticle-al)oral projection at a right angle.
Remarks--The very long, narrow aboral projection and straight, small posterior bar projecting approximately 90 degrees from the terminal denticle-aboral projection distinguishes Neoprioniodus ligo (Hass) from other species of Neoprioniodus reported in the present study. The illustrations of Hass (1953) and Elias (1956, 1959) indicate some variability in the aboral projection, from straight with parallel anterior and posterior edges to long, wedge-shaped, terminating in a point at the anterior edge.
Distribution--Neoprioniodus ligo has previously been recovered from rocks of late Chesteran age. In the present study two specimens were recovered from the Salem Limestone (Core I) and the St. Louis Limestone (Core N).
Repository--KUMIP 1,800,290 (figured specimen).
NEOPRIONIODUS LOXUS Rexroad
Neoprioniodus loxus Rexroad, 1957, p. 34, pl. 2, fig. 8, 9, 14; Rexroad, 1958b, p. 23, pl. 5, fig. 7, 9; Rexroad & Burton, 1961, p. 1155, pl. 140, fig. 12; Rexroad & Collinson, 1963, p. 18, pl. 2, fig. 28; Thompson & Goebel, 1963, p. 12, fig. 3; Rexroad & Furnish 1964, p. 674, pl. 111, fig. 26; Rexroad & Collinson, 1965, p. 12, pl. 1, fig. 11, 19; Rexroad & Nicoll, 1965, p. 23, pl. 2, fig. 23.
Neoprioniodus tenuis Rexroad, 1957, p. 35, pl. 2, fig. 13, 16.
Diagnosis--Neoprioniodid with long, compressed, slightly arched posterior bar bearing short denticles of unequal length in random sorting. Aboral projection short with sharp near 90-degree angle with aboral margin of posterior bar. Deep and small basal cavity located at juncture of aboral projection and posterior bar, with slight lateral flaring of inner and outer lips.
Remarks--Some representatives of Neoprioniodus loxus Rexroad recovered in the present study show considerable lateral flexure of the posterior bar as seen from oral view. The unequal and random sorting of the denticles of the posterior bar distinguish N. loxus from N. camurus Rexroad. The latter also has a more acute angle between the posterior bar and aboral projection. The lateral flexure of the posterior bar distinguishes N. loxus from N. acampylus Rexroad and Collinson and N. varians (Branson and Mehl).
Distribution--Neoprioniodus loxus has previously been recovered from rocks ranging in age from late Osagian to late Chesteran. In the present study 29 specimens were recovered from the Warsaw Limestone (Cores E, F, G, K), the Salem Limestone (Core I), the St. Louis Limestone (Cores A, C, N), the Ste. Genevieve Limestone (Core D), and the Keokuk Limestone (Locality P).
Repository--KUMIP 1,800,192; KUMIP 1,800,217 (figured specimens).
NEOPRIONIODUS ROUNDYI (Hass)
Prioniodus sp. B Roundy, 1926, p. 11, pl. 4, fig. 10.
Prioniodus roundyi Hass, 1953, p. 88, pl. 15, fig. 2, 3; Elias, 1956, p. 109, pl. 11, fig. 19-21.
Diagnosis--Neoprioniodid with slender, downward-arched slightly laterally flexed posterior bar, bearing discrete unfused denticles of uniform length. Terminal denticle long and narrow. Aboral projection pointed distally, broad and compressed at juncture with posterior bar. Aboral projection curved convexly inward, concave on outer side along posterior edge. Pit small and indistinct.
Remarks--The marked inward curve and outer concavity of the aboral projection distinguishes Neoprioniodus roundyi (Hass) from N. acampylus Rexroad & Collinson, N. loxus Rexroad, and N. varians (Branson & Mehl), each of which has a small outward and inward flare to the posterior edge of the aboral projection.
Distribution--Neoprioniodus roundyi has previously been reported from rocks of late Chesteran age. In the present study two specimens were recovered from the St. Louis Limestone in Core A.
Repository--KUMIP 1,800,095 (figured specimen).
NEOPRIONIODUS TULENSIS (Pander)
Pl. 3, fig. 7, 18; Pl. 4, fig. 20.
Prioniodus tulensis Pander (part), 1856, p. 30, pl. 2A, fig. 1 only; Holmes (part), 1928, p. 22, pl. 3, fig. 18 only.
Neoprioniodus tulensis (Pander). Rexroad & Collinson, 1963, p. 18, pl. 2, fig. 17, 22, 23; Rexroad & Collinson, 1965, p. 12, pl. 1, fig. 28, 29.
Neoprioniodus scitulus (Branson & Mehl). Thompson & Goebel, 1963, p. 12, fig. 3.
Diagnosis--Large neoprioniodid distinguished by long aboral projection with large laterally flared basal cavity, and short coarsely denticulate aborally curved posterior bar meeting terminal denticle at a nearly 90-degree angle.
Remarks--Considerable confusion exists about the differences between Neoprioniodus tulensis (Pander) and N. scitulus (Branson and Mehl). It appears that they are the same form, and that N. tulensis is a junior synonym of N. scitulus. This confusion is expressed by Rexroad and Collinson (1963), and both names have been used by various authors for seemingly the same morphologic form. There is little difference between N. tulensis and N. cassilaris (Branson and Mehl), except for the generally smaller size of the latter.
Distribution--Neoprioniodus tulensis has previously been recovered from rocks ranging in age from late Osagian to late Meramecian. In the present study 77 specimens were recovered from the Warsaw Limestone (Cores E, F, G, K, M, N, O), the Salem Limestone (Cores H, I), the St. Louis Limestone (Cores A, B, C, D, I, L, M, N, O), and the Keokuk Limestone (Locality P).
Repository--KUMIP 1,800,206; KUMIP 1,800,232; KUMIP 1,800,166 (figured specimens).
NEOPRIONIODUS VARIANS (Branson and Mehl)
Prioniodus varians Branson & Mehl, 1941a, p. 174, pl. 5, fig. 7, 8; Elias, 1956, p. 110, pl. 2, fig. 7, 8.
Prioniodina varians (Branson & Mehl). Bischoff, 1957,
p. 49, pl. 5, fig. 35; Flügel & Ziegler, 1957, p. 50.
Neoprioniodus varians (Branson & Mehl). Rexroad, 1957, p. 35, pl. 2, fig. 10; Rexroad, 1958b, p. 24, 1)1. 5, fig. 3, 4; Higgins, 1961, p. 226, pl. 11, fig. 1; Rexroad & Burton, 1961, p. 1155, pl. 140, fig. 9, 10; Rexroad & Collinson, 1963, p. 19, pl. 2, fig. 26; Rexroad & Nicoll, 1965, p. 24, pl. 2, fig. 18.
Prioniodus barbatus Branson & Mehl, Ellison & Graves (part), 1941, p. 19, pl. 1, fig. 27 only.
Diagnosis--Neoprioniodid with laterally compressed posterior bar forming a nearly 90-degree angle with terminal denticle at aboral juncture. Inner lip flared on small basal cavity in large aboral projection.
Remarks--Neoprioniodus varians (Branson and Mehl) is similar to N. loxus Rexroad, but has a smaller angle between the terminal denticle and posterior bar and a larger basal cavity. The denticles of the posterior bar are an alternation of one large and several very small fused units.
Distribution--Neoprioniodus varians has previously been recovered from rocks ranging in age from early late Meramecian to early Pennsylvanian. In the present study five specimens were recovered from the St. Louis Limestone in Cores B, C, M, and N.
Repository--KUMIP 1,800,272 (figured specimen).
NEOPRIONIODUS? CONCAVUS (Ulrich and Bassler)
Prioniodus concavus Ulrich & Bassler, 1926, p. 10, pl. 9, fig. 11.
Diagnosis--Short unit with strong, straight apical denticle and highly arched posterior bar containing several large denticles paralleling direction of apical denticle. Aboral projection very short and highly arched.
Remarks--This form may be placed in Neoprioniodus, but is unlike any typical representative of this genus in the extremely short aboral projection of the terminal denticle and the flat, highly curved aboral surface of the posterior bar.
Distribution--Neoprioniodus? concavus has been previously recovered from rocks of early Kinderhookian age. In this study one specimen was recovered from the St. Louis Limestone in Core N.
Repository--KUMIP 1,800,294 (figured specimen).
NEOPRIONIODUS? INCLINATUS (Hass)
Prioniodus sp. 1) Roundy (part), 1926, p. 11, pl. 4, fig. 12 only.
Prioniodus inclinatus Hass, 1953, p. 87, pl. 16, fig. 10-14.
Prioniodus? inclinatus Hass. Elias, 1956, p. 112, pl. 4, fig. 4-7.
Neoprioniodus inclinatus (Hass). Stanley, 1958, p. 462; 1961, p. 226, pl. 11, fig. 3.
Diagnosis--Unit with short, stout, terminal denticle with thick base and short posterior bar containing several discrete, relatively large denticles, well separated at their bases. Posterior bar makes a nearly 90-degree angle with base of aboral projection. Basal cavity broad, shallow, and oval.
Remarks--Some of the illustrations of Prioniodus inclinatus Hass by Hass (1953) appear to show a broken denticle stump anterior to the terminal denticle. Because of the anterior denticle, coupled with the gross size of the basal cavity, this form closely resembles those of Lonchodina, and places this form in doubtful taxonomic position. The specimens recovered in the present study do not show a broken surface on the anterior surface of the terminal denticle. These specimens are, therefore, placed in Neoprioniodus with reservation.
Distribution--Neoprioniodus? inclinatus has been previously recovered from rocks of early Chesteran age. In the present study two specimens were recovered from the Warsaw Limestone in Cores K and O.
Repository--KUMIP 1,800,303; KUMIP 1,800,249 (figured specimens).
NEOPRIONIODUS? sp.
Description--Unit highly arched and sharply bowed. Posterior limb long, slightly curved, containing short, sharply pointed unfused denticles of equal length along entire length. Terminal denticle very long and slender, curved slightly posteriorly and strongly inward. Aboral projection long and slender, highly compressed laterally, reflecting aboral extension of terminal denticle; no posterior extension beneath posterior bar. Basal cavity indistinct. Angle of aboral projection and posterior bar less than 30 degrees.
Remarks--This specimen closely resembles Apatognathus? porcata (Hinde), but differs in that the anterior bar contains no denticles, and this anterior bar is actually an aboral projection of the terminal denticle. The actual affinities of this form are unknown, and it is placed in Neoprioniodus with reservation.
Distribution--In the present study, one specimen of Neoprioniodus? sp. was recovered from the St. Louis Limestone in Core B.
Repository--KUMIP 1,800,112 (figured specimen).
Genus OZARKODINA Branson and Mehl, 1933
Ozarkodina Branson & Mehl, 1933, p. 51.
Type species--Ozarkodina typica Branson & Mehl, OD (1933, p. 51, pl. 3, fig. 43-45).
Diagnosis--Unit consisting of thin, denticulate arched blade with large major denticle near midpoint of blade; approximately equal number of subequal denticles on either side. Small, deep basal cavity found directly beneath ma)or denticle, at point of arch in blade.
Remarks--Ozarkodina is similar to Elictognathus, but does not possess lateral ridges near the basal margin that characterize the latter genus.
Speciation is based on the degree of arch in the blade and on the oral outline of the denticles.
Distribution--Ozarkodina has been identified from rocks ranging in age from Devonian to Pennsylvanian.
OZARKODINA COMPRESSA Rexroad
Ozarkodina compressa Rexroad, 1957, p. 36, pl. 2, fig. 1, 2; Rexroad, 1958b, p. 24, pl. 6, fig. 1, 2; Rexroad & Burton, 1961, p. 1156, pl. 141, fig. 16, 17; Rexroad & Furnish, 1964, p. 674, pl. 111, fig. 9; Rexroad & Nicoll, 1965, p. 24, pl. 2, fig. 3, 4.
Diagnosis--Ozarkodinid with thin, bladelike, slightly laterally curved unit containing fused denticles, large apical denticle, and small basal cavity with weakly flared lips.
Remarks--The forms recovered in this study are placed in Ozarkodina compressa Rexroad, but possess a small basal cavity with less lateral flare than specimens previously reported.
Distribution--Ozarkodina compressa has previously been recovered from rocks ranging in age from late Meramecian to late Chesteran. In the present study three specimens were recovered from the Warsaw Limestone (Core F) and the St. Louis Limestone (Cores A, B).
Repository--KUMIP 1,800,113; KUMIP 1,800,194 (figured specimens).
OZARKODINA CURVATA Rexroad
Ozarkodina curvata Rexroad, 1958b, p. 24, pl. 4, fig. 1-3; Rexroad & Burton, 1961, p. 1156, pl. 141, fig. 13, 14; Rexroad & Collinson, 1963, p. 18, pl. 2, fig. 11; Rexroad & Furnish, 1964, p. 674, pl. 111, fig. 10, 11; Rexroad & Nicoll, 1965, p. 25, pl. 2, fig. 1, 2.
Diagnosis--Ozarkodinid distinguished by strongly arched anterior limb with large compressed denticles. Posterior limb smaller than anterior limb; nearly straight, with small denticles. Basal cavity small and deep, with flared outer lip and nearly straight inner lip.
Remarks--The arching of Ozarkodina curvata Rexroad is greatest anterior to the position of the basal cavity, and the arching of this species is greater than in O. recta Rexroad, which has almost no arching in the aboral margin.
Distribution--Ozarkodina curvata has previously been recovered from rocks of late Meramecian and late Chesteran age. In this study three specimens were recovered from the Warsaw Limestone (Core F) and the St. Louis Limestone (Core A).
Repository--KUMIP 1,800,195 (figured specimen).
OZARKODINA sp. cf. O. LAEVIPOSTICA Rexroad and Collinson
Ozarkodina cf. O. laevipostica Rexroad & Collinson. Rexroad & Collinson, 1965, p. 13, pl. 1, fig. 12.
Diagnosis--Ozarkodinid with large basal cavity, denticulate posterior limb, and unfused denticles on anterior limb. Unit highly arched beneath curved apical denticle.
Remarks--These specimens resemble Ozarkodina laevipostica Rexroad and Collinson, but differ in the larger basal cavity, denticulate posterior limb, and unfused denticles of the anterior limb. Rexroad and Collinson (1965) consider this form to represent members of a lineage from Subbryantodus radians Branson and Mehl to O. laevipostica. Immature specimens of the latter form do have a denticulate posterior limb, and this reflects the phylogeny.
Distribution--Ozarkodina sp. cf. O. laevipostica has been previously recovered from rocks of early Meramecian age. In the present study eight specimens were recovered from the Warsaw Limestone (Core F) and the St. Louis Limestone (Cores A, D).
Repository--KUMIP 1,800,196;KUMIP 1,800,334 (figured specimens).
OZARKODINA RECTA Rexroad
Ozarkodina recta Rexroad, 1957, p. 36, pl. 2, fig. 5, 6; Rexroad & Furnish, 1964, p. 674, pl. 111, fig. 8.
Diagnosis--Ozarkodinid distinguished by thin, long, slightly curved blade with straight anterior limb containing straight, nearly vertical, closely spaced denticles and shorter, slightly arched posterior limb with wide, compressed denticles inclined posteriorly; this inclination increasing toward posterior end. Small, deep basal cavity with little lateral flare lies beneath apical denticle.
Remarks--Ozarkodina recta Rexroad has less arching than O. curvata Rexroad, and has a straighter apical denticle than O. compressa Rexroad.
Distribution--Ozarkodina recta has previously been recovered from rocks ranging in age from late Meramecian to early Chesteran. In the present study six specimens were recovered from the Warsaw Limestone (Core K) and the St. Louis Limestone (Cores B, C).
Repository--KUMIP 1,800,125 (figured specimen).
OZARKODINA ROUNDYI (Hass)
Subbryantodus roundyi Hass, 1953, p. 89, pl. 14, fig. 3-6.
Ozarkodina roundyi (Hass). Rexroad, 1957, p. 37, pl. 2, fig. 7; Bischoff, 1957, p. 66, pl. 1, fig. 29-32, p. 68, pl. 2, fig. 1-3; Müller, 1962, p. 1390, text-fig. 3; Dunn, 1965, p. 1149, pl. 140, fig. 19, 20.
Diagnosis--Long, thin, arched ozarkodinid with long, broad, sharply pointed denticles, largest on anterior limb. Lowest point of oral outline just posterior to apical denticle, above point of greatest arch. Basal cavity small, with little or no lateral flare.
Remarks--The broad denticles on the anterior limb and the increasing height of the blade toward the anterior distinguishes Ozarkodina roundyi (Hass) from other ozarkodinids in this study.
Distribution--Ozarkodina roundyi has previously been recovered from rocks of Kinderhookian and early Chesteran age. In the present study two specimens were recovered from the Warsaw Limestone in Core G.
Repository--KUMIP 1,800,207 (figured specimen).
Genus SPATHOGNATHODUS Branson and Mehl, 1941
Ctenognathus Pander, 1856, p. 32 (not Fairmair, 1843).
Spathodus Branson & Mehl, 1933, p. 46 (not Boulenger, 1900).
Spathognathodus Branson & Mehl, 1941c, p. 98.
Mehlina Youngquist, 1945, p. 363.
Branmehla Hass, 1959, p. 381.
Ctenognathodus Fay, 1959, p. 195.
Spathognathodus (Bispathodus) Müller, 1962, p. 114.
Type species--Spathodus primus Branson & Mehl, OD (1933, p. 46, pl. 3, fig. 25-30). See Klapper, 1966.
Diagnosis--Unit bladelike, axis straight or flexed inward; aboral edge straight to arched. Basal cavity in middle one-third of unit, but extending in some forms to posterior tip.
Remarks--Spathognathodus is presently considered to be a valid generic name (Rexroad and Scott, 1964, p. 46), and is ancestral to several platform genera, including Pseudopolygnathus and Taphrognathus.
Speciation is based on the oral outline of the blade and on the shape and location of the basal cavity.
Distribution--Spathognathodus has been identified from rocks ranging in age from Devonian to Pennsylvanian.
SPATHOGNATHODUS CAMPBELLI Rexroad
Spathognathodus campbelli Rexroad, 1957, p. 37, pl. 3, fig. 13-15; Rexroad, 1958b, p. 25, pl. 6, fig. 9; Rexroad & Burton, 1961, p. 1156, pl. 141, fig. 15; Rexroad & Furnish, 1964, p. 674, pl. 111, fig. 23, 24; Rexroad & Nicoll, 1965, p. 26, pl. 1, fig. 6.
Diagnosis--Spathognathodid distinguished by delicate blade composed of many small compressed denticles forming straight oral outline, and by small, narrow basal cavity.
Remarks--The forms referred to Spathognathodus campbelli Rexroad recovered in the present study are quite small, with thin blades and denticles. The oral outline tends to be irregular, due to several of the denticles being broken.Distribution--Spathognathodus campbelli has been previously recovered from rocks ranging in age from late Meramecian to late Chesteran. In the present study two specimens were recovered from the St. Louis Limestone in Core B.
Repository--KUMIP 1,800,127 (figured specimen).
SPATHOGNATHODUS CRISTULA Youngquist and Miller
Spathognathodus cristula Youngquist & Miller, 1949, p. 621, pl. 101, fig. 1-3; Rexroad, 1957, p. 38, pl. 3, fig. 16, 17; Rexroad, 1958b, p. 25, pl. 6, fig. 3, 4; Rexroad & Burton, 1961, p. 1156, pl. 141, fig. 9; Rexroad & Furnish, 1964, p. 674, pl. 111, fig. 15; Rexroad & Nicoll, 1965, p. 26, pl. 1, fig. 1, 2.
Diagnosis--Spathognathodid characterized by short, slightly arched blade with subequal denticles fused nearly to apices; posterior-most two to three denticles small, anterior-most denticles longer and wider; anterior-most denticle very large and broad at base. Oral margin convex toward posterior end, straight anteriorly. Broadly flared basal cavity bilaterally symmetrical, deepening near anterior end into anteriorly inclined pit; cavity extends to posterior end of blade and two-thirds to three-fourths total length of blade.
Remarks--The bilateral symmetry of the basal cavity distinguishes Spathognathodus cristula Youngquist and Miller from S. scitulus (Hinde), a species with a strongly asymmetric cavity. The large anterior denticle of the blade distinguishes S. cristula from S. campbelli Rexroad, which does not have a prominent anterior denticle. The posterior denticles of S. penescitulus Rexroad and Collinson are unfused and much broader than the denticles just posterior to the anterior denticle, whereas the denticles of S. cristula become gradually smaller toward the posterior end of the blade.
Distribution--Spathognathodus cristula has been previously recovered from rocks ranging in age from late Meramecian to early Pennsylvanian. In the present study 36 specimens were recovered from the Warsaw Limestone (Cores F, K), the Salem Limestone (Core I), the St. Louis Limestone (Cores A, B, C, D, I, M, N), and the Keokuk Limestone (Locality Q).
Repository--KUMIP 1,800,233; KUMIP 1,800,128 (figured specimens).
SPATHOGNATHODUS PENESCITULUS Rexroad and Collinson
Spathognathodus regularis Branson & Mehl. Branson & Mehl, 1941b, p. 187, pl. 6, fig. 7.
Spathognathodus penescitulus Rexroad & Collinson, 1965, p. 22, pl. 1, fig. 13-15.
Diagnosis--Spathognathodid characterized by short blade with large basal cavity extending three-fourths length of blade. Prominent anterior denticle followed posteriorly by eight denticles, three small and deeply inserted, three large and broad, two small and unfused.
Remarks--The shape of Spathognathodus penescitulus Rexroad and Collinson is like that of S. scitulus (Hinde), but the basal cavity is more symmetrical, and extends to the posterior tip of the specimen. In S. penescitulus, the denticles of the blade increase in width on the posterior portion, while those of S. cristula Youngquist and Miller gradually decrease in size posteriorly from the anterior denticle.
Distribution--Spathognathodus penescitulus has been previously recovered from rocks of early Meramecian age. In the present study three specimens were recovered from the Warsaw Limestone (Core F), the Salem Limestone (Core H), and the St. Louis Limestone (Core C).
Repository--KUMIP 1,800,149 (figured specimen).
SPATHOGNATHODUS sp. cf. S. PULCHER (Branson & Mehl)
Spathognathodus cf. S. pulcher (Branson & Mehl). Rexroad & Collinson, 1965, p. 23, pl. 1, fig. 16.
Spathoduiis pulcher Branson & Mehl, 1938, p. 139, pl. 34, fig. 7, 8.
Description--Spathognathodid with two denticles at anterior end, either one small denticle at anterior end and one larger denticle posterior to small one, or two large anterior denticles of uniform length. Posterior eight or nine denticles uniform in length, which broaden posteriorly. Posterior-most four denticles decrease in length to posterior end of unit. Cavity symmetrical, broadest at midpoint of unit, tapering to gradual point posteriorly, tapering more abruptly to anterior. Aboral margin straight beneath anterior two denticles, slightly arched downward beneath basal cavity.
Remarks--The oral outline posterior to the major anterior denticles of these specimens is like that of Spathognathodus cf. S. pulcher as illustrated by Rexroad & Collinson (1965). The anterior denticles are the same in number, but different in relative sizes. This feature appears to be quite variable in S. pulcher.
Distribution--Two specimens of Spathognathodus sp. cf. S. pulcher (Branson & Mehl) were recovered in the present study from the Warsaw Limestone (Core F) and the St. Louis Limestone (Core C).
Repository--KUMIP 1,800,150; KUMIP 1,800,199 (figured specimens).
SPATHOGNATHODUS SCITULUS (Hinde)
Polygnathus scitulus Hinde, (part), 1900, p. 343, pl. 9, fig. 9, 11 only.
Panderodella scitulus (Hinde). Holmes (part), 1928, p. 16, pl. 6, fig. 26, 28 only.
Spathognathodus scitulus (Hinde). Clarke, 1960, p. 21, pl. 3, fig. 12, 13; Rexroad & Collinson, 1963, p. 20, pl. 2, fig. 14, 19, 29-31.
Diagnosis--Spathognathodid distinguished by short, high blade with sharply pointed major anterior denticle and 10 to 12 posterior denticles forming straight anterior oral outline. Aboral outline straight; nearly 120-degree angle formed between aboral and oral surface juncture at posterior end. Short, deep basal cavity sharply asymmetric, outer lip widely flared laterally, inner lip weakly flared.
Remarks--The strong asymmetry of the basal cavity distinguishes Spathognathodus scitulus (Hinde) from S. campbelli Rexroad, S. cristula Branson and Mehl, and S. penescitulus Rexroad and Collinson, which have symmetrical basal cavities.
Distribution--Spathognathodus scitulus has previously been recovered from rocks of late Meramecian age. In the present study 11 specimens were recovered from the St. Louis Limestone (Cores A, B, C), and the Ste. Genevieve Limestone (Core D).
Repository--KUMIP 1,800,151 (figured specimen).
SPATHOGNATHODUS SPICULUS Youngquist & Miller
Spathognathodus spiculus Youngquist & Miller, 1949, p. 622, pl. 101, fig. 4; Rexroad, 1957, p. 38, pl. 3, fig. 18-21; Rexroad, 1958b, p. 25, pl. 6, fig. 5-7; Rexroad & Furnish, 1964, p. 674, pl. 111, fig. 20-22; Rexroad & Nicoll, 1965, p. 26, pl. 1, fig. 3-5. Spathognathodus bidens Youngquist & Miller, 1949, p. 621, pl. 101, fig. 5.
Diagnosis--Spathognathodid with three to four prominent anterior denticles followed to posterior by uniform discrete denticles gradually tapering in length to posterior end. Oral outline nearly straight to convex upward, aboral outline straight to convex upward.
Remarks--The prominent anterior denticles of Spathognathodus spiculus Youngquist & Miller show considerable variation in number, from two to five. The oral outline of these denticles also varies considerably in shape, from straight to convex, becoming more convex as the number of denticles increases.
Distribution--Spathognathodus spiculus has previously been reported from rocks of late Meramecian and Chesteran age. In the present study, one specimen was recovered from the St. Louis Limestone in Core A.
Repository--KUMIP 1,800,102 (figured specimen).
SPATHOGNATHODUS n. sp.
Cavusgnathus muricata Dunn, 1965, p. 1147, pl. 140, fig. 1, 4.
Description--Viewed orally, curved blade has four to six inner-lateral denticles forming parapet parallel to blade; parapet merging with blade near posterior end of specimen. Free anterior portion of blade short; broken in specimens from present study.
Laterally, oral outline straight, highest at anterior end. Denticles short and broad on free blade and parapet except for three or four denticles at posterior end of free blade that are narrow.
Aborally, basal cavity elongate and narrow, tapering rapidly to sharp point at posterior end of specimen; lateral flare restricted to anterior half of cavity.
Remarks--Dunn (1965) described and illustrated as Cavusgnathus muricata Dunn, n. sp., specimens like those herein referred to Spathognathodus n. sp. Several homeomorphic cases of spathognathodids with lateral denticles exist, widely separated in time (late Devonian to Pennsylvanian) (personal communication, Gilbert Klapper with Thompson, 1967). The basal cavity tapers to the posterior more rapidly than does that typical of cavusgnathids, and the long, free blade (broken from specimens in the present study) illustrated by Dunn (pl. 140, fig. 1) is quite unlike the short, free blade of Cavusgnathus.
Distribution--In the present study, five specimens of Spathognathodus n. sp. were recovered from the St. Louis Limestone in Core A.
Repository--KUMIP 1,800,082; KUMIP 1,800,333 (figured specimens).
SPATHOGNATHODUS n. sp.?
Description--Unit large, consisting of extremely large anterior denticle and eight subequal posterior denticles that become broader toward posterior. Oral outline nearly straight immediately posterior to anterior denticle, highly convex toward posterior end. Aboral outline arched slightly anterior to midpoint. Basal cavity shallow and narrow, deepest at point of greatest width, and extends from posterior tip to directly beneath posterior edge of anterior denticle. Widest point of cavity at midpoint of blade, and cavity decreases to sharp point at posterior end. Groove extends entire length of cavity.
Remarks--This form bears closest similarity to Spathognathodus cristula Youngquist & Miller, but differs in the extremely large anterior denticle and the narrow and shallow basal cavity.
Distribution--In the present study one specimen of Spathognathodus n. sp.? was recovered from the St. Louis Limestone in Core D.
Repository--KUMIP 1,800,169 (figured specimen).
Genus SYNPRIONIODINA Ulrich and Bassler, 1926
Synprioniodina Ulrich & Bassler, 1926, p. 42.
Type species--Synprioniodina alternata Ulrich & Bassler, OD (1926, p. 42, text-fig. 4, no. 22, p. 16).
Diagnosis--Unit consisting of sharply arched bar with prominent apical denticle above point of arch. Posterior limb long and denticulate; anterior limb short, containing several small denticles. Basal cavity small and deep.
Remarks--Ulrich and Bassler (1926 named and described several new genera of conodonts similar to Synprioniodina. Euprioniodina has coarser and unfused denticles and a flat aboral surface beneath the limbs, Prioniodina is gently curved aborally, not arched, Lonchodina possesses a large, widely flared basal cavity, and Palmatodella has large numerous denticles on the posterior limb and a strongly curved apical denticle.
Speciation is based on the degree of arching of the unit, the size and shape of the basal cavity, and the denticulation of the anterior limb.
Distribution--Synprioniodina has been identified from rocks ranging in age from Devonian to Pennsylvanian.
SYNPRIONIODINA LAXILABRUM Rexroad and Collinson
Synprioniodina laxilabrum Rexroad & Collinson, 1965, p. 23, pl. 1, fig. 3-5.
Diagnosis--Small synprioniodinid characterized at juncture of posterior and anterior limbs by small basal cavity with widely flaring inner lip. Angle of arch nearly 45 degrees. Terminal denticle small and bowed.
Remarks--Rexroad and Collinson (1965) discussed several species described by Cooper(1939) that are possibly related forms of Synprioniodina laxilabrum Rexroad & Collinson. The number of specimens recovered is small, and knowledge of forms such as this is meager concerning species of Mississippian age.
Distribution--Synprioniodina laxilabrum has been previously recovered from rocks of early Meramecian age. In the present study three specimens were recovered from the Warsaw Limestone in Core K.
Repository--KUMIP 1,800,252 (figured specimen).
Genus TAPHROGNATHUS Branson and Mehl, 1941
Taphrognathus Branson & Mehl, 1941b, p. 181.
Type species--Taphrognathus varians Branson & Mehl, OD (1941b, p. 182, pl. 6, fig. 27-33, 35-41).
Diagnosis--Unit consisting of short posterior platform containing two lateral parapets separated by deep median trough. Anterior blade extends short distance onto platform as low carina, located between parapets on anterior end of platform. Basal cavity long, narrow, and shallow.
Remarks--Taphrognathus arose during medial Osagian time, and continued to early late Meramecian time, when it evolved into, and was replaced by, Cavusgnathus.
Speciation is based on the size and shape of the basal cavity and the position of the posterior end of the blade with respect to the two parapets of the platform.
Distribution--Taphrognathus has been identified from rocks ranging in age from early Osagian to late Meramecian.
TAPHROGNATHUS VARIANS Branson and Mehl
Taphrognathus varians Branson & Mehl, 1941b, p. 182, fig. 27-33, 35-40; Rexroad & Collinson, 1963, p. 21, pl. 1, fig. 18-20, 22; Thompson & Goebel, 1963, p. 12, fig. 3; Rexroad & Collinson, 1965, p. 24, pl. 1, fig. 30-32. (not) Taphrognathus varians Branson & Mehl. Cooper, 1947, p. 92, pl. 20, fig. 14-16.
Diagnosis--Taphrognathid with centrally located carina between lateral parapets at anterior end of platform. Basal cavity bilaterally symmetrical, long, narrow to widely flared, shallow, pointed at both ends.
Remarks--Taphrognathus is presently monospecific, and considerable morphologic variation is exhibited in specimens recovered in the present study. The basal cavity varies from very narrow to widely flared; from elongate and narrow to nearly circular in outline. The platform may be short and broad or long and narrow. It is neither practical nor useful to subdivide Taphrognathus into new species at this time. The variations mentioned above do not show affinities to time of occurrence.
Distribution--Taphrognathus varians has previously been recovered from rocks ranging in age from late Osagian to early late Meramecian. In the present study over 300 specimens were recovered from the Warsaw Limestone (Cores E, F, G, H, K, M, N, O), the Salem Limestone (Cores C, D, I, N, O), and the lower part of the St. Louis Limestone (Cores I, M, N, O), and the Keokuk Limestone (Locality P).
Repository--KUMIP 1,800,200; KUMIP 1,800,265; KUMIP 1,800,183; KUMIP 1,800,220; KUMIP 1,800,327 (figured specimens).
TAPHROGNATHUS sp.
Taphrognathus varians Branson & Mehl (part), 1941b, p. 182, pl. 6, fig. 34 only.
Taphrognathus n. sp. Thompson & Goebel, 1963, p. 12, fig. 3.
Taphrognathus-Cavusgnathus transition Rexroad & Collinson, 1963, p. 20, pl. 1, fig. 21, 23-25.
Description--Unit consisting of short posterior platform with inner parapet ending abruptly at anterior end, outer parapet connecting to carina of anterior blade. Blade centrally located at anterior end, curving outward approaching platform to form carina lying in same plane of outer parapet of platform. Long, narrow, asymmetric basal cavity, curved outward beneath lateral carina.
Remarks--Taphrognathus sp. can be distinguished from T. varians Branson & Mehl by the lateral carina and the asymmetric, narrow basal cavity. This form is interpreted to represent the transition from Taphrognathus to Cavusgnathus, achieved through the migration of the position of the carina from one of central to lateral position with respect to the platform. This form is a good index to the short time interval of this transition, and occurs in the middle portion of the St. Louis Limestone.
Distribution--Taphrognathus sp. has been previously recovered from rocks of early late Meramecian age. In the present study nine specimens were recovered from the St. Louis Limestone in Cores C and I.
Repository--KUMIP 1,800,153 (figured specimen).
New genus? sp.
Description--Unit consisting of elongate, laterally bowed bar containing numerous sharply pointed denticles, fused less than halfway to apices. Denticles alternating in length; anterior three small and equal, next posterior three long and wide, next four smaller and more slender. Posterior four denticles gradually increase in length; posterior-most denticles very broad at apices, spatulate in lateral outline, highly compressed. Inner margin of bar contains deep groove, broadening and ending just prior to posterior end, where it bends upward and parallels anterior margin of posterior-most denticle. Outer margin of bar smooth. Posterior denticle contains small, slightly flared pit halfway up posterior margin, and appears to extend aborally as very short, blunt aboral projection. Anterior end of specimen broken off.
Remarks--This specimen is unlike any previously reported from Mississippian strata. The spatulate posterior two denticles are characteristic of this form.
Distribution--In the present study one specimen of New genus? sp. was recovered from the St. Louis Limestone in Core M.
Repository--KUMIP 1,800,275 (figured specimen).
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Kansas Geological Survey, Geology
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