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Conodonts of the Meramecian Stage in Kansas

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Meramecian Conodont Fauna

The conodont fauna recovered comprises over 1,500 identifiable specimens (Appendix). They were obtained from over 500 samples processed from cores of 15 wells, and from two outcrops (Table 1). From this fauna 40 named species representing 14 genera are identified; nine additional forms of doubtful specific identity are referred to seven genera; two possible new species of two genera are included; one specimen representing a possible new genus and species is described. A complete list of specimens recovered, including stratigraphic ranges, is shown in Table 2.

Table 2--Stratigraphic distribution of conodonts from the Meramecian Stage in Kansas.

  Meramecian Stage
St. Louis
Ste. Genevieve
Apatognathus? gemina     X  
A.? porcata     X  
A.? n. sp. A X X X  
Cavusgnathus alta     X  
C. characta     X X
C. convexa     X X
C. regularis     X X
C. unicornis     X X
C. sp.     X  
Gnathodus commutatus     X  
G. girtyi? X   X  
G. texanus X X X  
Hibbardella abnormis X   X  
H. fragilis X X X  
H. ortha X X X  
Hindeodelloides bicristatus     X  
Lambdagnathus fragilidens     X  
Ligonodina levis X X X X
L. roundyi X   X  
L. sp. A     X  
L. n. sp.     X  
Lonchodina paraclarki X      
L. paraclaviger X      
Magnilaterella robusta X   X  
Neoprioniodus acampylus X      
N. camurus X   X  
N. sp. cf. N. cassilaris X      
N. ligo   X X  
N. loxus X X X X
N. roundyi     X  
N. tulensis X X X  
N. varians     X  
N.? concavus     X  
N.? inclinatus X      
N.? sp.     X  
Ozarkodina compressa X   X  
O. curvata X   X  
O. sp. cf. O. laevipostica X   X  
O. recta X   X  
O. roundyi X      
Spathognathodus campbelli     X  
S. cristula X X X  
S. penescitulus X X X  
S. sp. cf. S. pulcher X   X  
S. scitulus     X X
S. spiculus     X  
S. n. sp.     X  
S. n. sp.?     X  
Synprioniodina laxilabrum X      
Taphrognathus varians X X X  
T. sp.     X  
New genus? sp.     X  

Gnathodus texanus Roundy comprises over half of the specimens, and nearly half of the remaining forms are Taphrognathus varians Branson and Mehl. Listing the other species in numerical order would be misleading, for frequency is largely a function of the number of samples processed from each zone. Numerically insignificant species are useful in identification of some zones that are not well represented in the material processed. The following discussion of the zones established by Collinson, et al. (1962) includes these less numerous species where they are valuable in the identification of a zone.

The Meramecian Stage, comprising the upper part of the Valmeyeran Series in the type section in the Mississippi River Valley, is composed of two complete concurrent-range zones and the lower portion of a third. These zones are described below in ascending order.

Taphrognathus varians-Apatognathus? Zone

The base of this zone is defined (Collinson, et al., 1962, p. 24) by the lowest occurrence of species of questionable generic reference to "Apatognathus?", and by the lowest occurrence of numerous Taphrognathus varians. The upper limit is established where Cavusgnathus replaces Taphrognathus as the dominant form, and by the lower limit of occurrence of Apatognathus? gemina (Hinde) and A.? porcata (Hinde). The range of this zone corresponds to the Warsaw, Salem, and lower portion of the St. Louis formations in the Mississippi River Valley, from early to early late Meramecian age. The zone is characterized by Apatognathus? n. sp. A Rexroad and Collinson, Gnathodus texanus Roundy, Neoprioniodus acampylus Rexroad and Collinson, N. sp. cf. N. cassilaris (Branson and Mehl), and T. varians Branson and Mehl.

The lower portion of this zone, the Warsaw Formation in the type section, is characterized by abundant Gnathodus texanus and by common, but less numerous, Taphrognathus varians. Apatognathus? n. sp. A also appears more frequently in the Warsaw strata than in younger beds. The upper portion, the Salem Formation and lower part of the St. Louis Formation, is conspicuous in the nearly total absence of G. texanus and by common but less plentiful T. varians (see Rexroad and Collinson, 1965, p. 4).

Apatognathus? gemina-Cavusgnathus Zone

The lower limit of this zone is based on the last appearance of Taphrognathus and the first abundant appearance of Cavusgnathus, and by the lowest common occurrence of Apatognathus?. The upper limit corresponds to the last occurrence of Apatognathus?. This zone spans the range of Apatognathus? gemina (Hinde) and A. porcata (Hinde) and is contained within the upper portion of the St. Louis Limestone (early late Meramecian in age) in the type locality. Characteristic species include A.? gemina, A.? porcata, Cavusgnathus convexa Rexroad, C. regularis Youngquist and Miller, C. unicornis Youngquist and Miller, Neoprioniodus varians (Branson and Mehl), Spathognathodus scitulus (Hinde), and Taphrognathus sp.

The transition from Taphrognathus to Cavusgnathus (Rexroad, 1958b) occurs at the base of this zone. Taphrognathus sp., the transitional form, is relatively common in this zone, mixed with species of Cavusgnathus and Taphrognathus.

Gnathodus bilineatus-Cavusgnathus characta Zone

The lower limit of this zone is marked by the highest appearance of Apatognathus?. The upper limit is in the middle portion of the Chesteran Stage and is marked by the lowest appearance of Roundya barnettana Hass. The original description of this zone (Collinson, et al., 1962, p. 25) also places the upper limit at the lowest occurrence of Gnathodus girtyi Hass, Lonchodina paraclarki Hass, and Cavusgnathus alta Harris and Hollingsworth. From the present study, these forms can possibly now be extended to the base of this zone, and L. paraclarki may range at least as far down as the Warsaw (Table 2). However, this apparent extension of ranges may be the result of reworking.

The portion of this zone within the limits of the present study is the lower part, the Ste. Genevieve Limestone of late Meramecian age. Characteristic species in this lower portion include Cavusgnathus regularis Youngquist and Miller, C. unicornis Youngquist and Miller, Gnathodus commutatus Branson and Mehl, G. girtyi? Hass, Neoprioniodus varians (Branson and Mehl), and Spathognathodus scitulus (Hinde). Other forms described in the present study, but not included in the above discussion, appear at this time to add little information to the age or significance of the fauna.

There appears to be an appreciable difference between the faunas recovered from the Meramecian section in Kansas and the Meramecian rocks in the Mississippi River Valley (Collinson, et al., 1962; Rexroad and Collinson, 1963, 1965; Rexroad and Furnish, 1964; Thompson, 1966). Thirty-one species are common to Meramecian rocks of both the Mississippi River Valley and the Kansas section. Fourteen species were reported from Meramecian rocks of the Mississippi River Valley that were not recovered in the present study; eight of these are from the Pella Beds of late Meramecian age (Ste. Genevieve), in Iowa (Rexroad and Furnish, 1964). Ste. Genevieve material in the present study was not covered as completely as was older Meramecian material. Fifteen species were recovered from Meramecian rocks in Kansas that are unknown from equivalent strata in the Mississippi River Valley. These are Cavusgnathus alta, Gnathodus girtyi?, Hibbardella fragilis, Hindeodelloides bicristatus, Ligonodina roundyi, Lonchodina paraclarki, L. paraclaviger, Neoprioniodus ligo, N. roundyi, N.? concavus, N.? inclinatus, Ozarkodina roundyi, Spathognathodus n. sp.?, and a new genus, as yet unnamed.

Most of the above species were previously restricted to strata of Chesteran age (Hass, 1953; Elias, 1956, 1959; Rexroad, 1957, 1958a), but are found in Meramecian rocks in Kansas. Of these species, only Spathognathodus n. sp.? and the new genus are unknown from Chesteran strata. This difference may be one of regional variations in sedimentary history, or mixing of faunas by early Chesteran erosion. It is for this reason that the platform conodonts, Cavusgnathus, Gnathodus, Spathognathodus, and Taphrognathus, are given the greatest weight when correlating between regions.

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Kansas Geological Survey, Geology
Placed on web June 24, 2010; originally published Dec. 1968.
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