UN* RSITY OF ILLIujjs LIBRARY AT URBANA-CHAMPAIGN NATURAL HIST. SURVEY FIELDIANA • GEOLOGY Published by CHICAGO NATURAL HISTORY MUSEUM Volume 10 July 29, 1954 No. 19 FAUNA OF THE VALE AND CHOZA: g CAPTORHINOMORPHA Everett Claire Olson Research Associate, Division of Paleontology Professor of Vertebrate Paleontology, University of Chicago The presence of captorhinomorph reptiles in the Vale and Choza formations has been noted in my earlier papers (Olson, 1948, 1951a, and 1951b). One new genus and species, Captor hinoides valensis, was described previously (Olson, 1951b). Additions to the collec- tions made during the last several years and preparation of specimens collected earlier now provide a basis for a more adequate analysis of the suborder in post-Arroyo Clear Fork beds of Texas. The specimens unfortunately are largely fragmentary, the best being only partial skeletons, but most skeletal parts now can be assigned to recognized species. The descriptions and discussion that follow touch upon all genera and species of Vale and Choza captorhino- morphs now known, including both new materials and those men- tioned in earlier papers. CLASS REPTILIA Subclass Eureptilia Infraclass Captorhina Order Captorhina Family Captorhinidae Captorhinus aguti Cope This species of Captorhinus has been known heretofore from the Admiral and Belle Plains formations of the Wichita group and the Clyde and Arroyo formations of the Clear Fork group, all of the early Permian of Texas. It is relatively abundant in the Belle Plains and Arroyo formations. In addition, a great many specimens have been obtained by various parties from fissure fills at Richard's Spur, Oklahoma. The Oklahoma deposits appear to be Arroyo in age. No. 737 211 212 FIELDIANA: GEOLOGY, VOLUME 10 Specimens that appear to be referable to this species have come from the following localities in the Vale: BX, KI, KA and KC.1 The first listed locality contains beds of lowest Vale age. KI in- cludes beds of the lower part of the upper Vale and KA and KC beds of the upper Vale. The best-preserved specimen is C.N.H.M. U.R. 118, from KC. It consists of lower jaws, part of the skull, 13 pre- FlG. 85. Labidosaurikos barkeri. A, B, D, E, type, C.N.H.M. U.R. 110. A, inter-clavicle and lower end of clavicle; B, head of right femur; D, part of lower jaw showing tooth pattern as preserved in matrix with tops of crowns showing; E, dorsal vertebra in dorsal view. Lower Choza in age. C, lateral view of fragment of skull showing part of orbit; C.N.H.M. U.R. 116, lower Vale in age. F, part of maxillary in ventral view; C.N.H.M. U.R. 113, middle Vale in age. All X 1/2. sacral vertebrae, the head of a humerus, and miscellaneous fragments. Specific assignment can be made with considerable certainty. Other materials are more fragmentary and are of somewhat less certain specific affinities, but nothing known of them suggests that they are not Captorhinus aguti. The discoveries in the Vale show that Captorhinus aguti ranged at least from the Admiral Formation through the Vale and is thus one of the longest-lived species known from the Texas Permian. A fragmentary specimen of Captorhinus, identifiable from poorly preserved vertebrae and skull fragments, has been found in the middle Choza. Although it is impossible to determine whether or 1 See Olson (1948) for index system and specific locations of KC and KA and other localities cited in this paper. See Olson (1951b, p. 104) for the location of KI. BX is located on aerial photographs as follows: CUM 6B, 35, 7.1-3.0 along north and east margins of breaks to 8.6-3.9, west to 7.1-3.0. The beds of this locality appear to be of lowest Vale age and immediately overlie the even red shale beds of the upper Arroyo. Dimetrodon gigashomogenes, Gnathorhiza dikeloda, Captorhinus aguti, and Xenacanthus sp. have been identified from this locality. BX is one of the several localities in the lower Vale of western Baylor County, Texas, studied during the field seasons of 1951 and 1952. OLSON: FAUNA OF VALE AND CHOZA 213 not this is Captorhinus aguti, the specimen is important in extending the range of Captorhinus into the middle Choza. Captorhinoides valensis Olson This species was described by me in the second article of this series (Olson, 1951b). The only known specimen consists of a skull and lower jaws. Principal differences from Captorhinus lie in the structure of the stapes and the nature of the cranio-palatal joint. The locality from which it came, KF, was assigned to the upper Vale in an earlier paper. More recent field work has shown that it comprises beds that must be assigned to the middle rather than the upper part of the Vale. Labidosaurikos barkeri sp. nov.1 Figure 85. Type. — C.N.H.M. U.R. 110. Partial skeleton including upper jaw and skull fragments, parts of lower jaws, 10 vertebrae, part of clavicle, inter-clavicle, symphysial parts of the pubes, head of a femur, proximal and distal ends of humerus and fibula, plus miscella- neous fragments. Horizon and locality. — Lower part of the Choza Formation, Clear Fork group, early Permian; Loc. FA, pipe site, Foard County, Texas. Referred specimens. — C.N.H.M. U.R. 114, tooth bearing maxil- lary, Crooked Creek, lower part of Vale Formation, Baylor County, Texas; C.N.H.M. U.R. 116, part of side wall of skull, including par- tial jugal; lacrimal, and maxillary with teeth, Crooked Creek, lower part of Vale Formation, Baylor County, Texas; C.N.H.M. U.R. 115, partial maxillary tooth plate, Fish Creek, lower part of Vale Forma- tion, Baylor County, Texas; M.C.Z. 1352, tooth plate, presumably maxillary, locality somewhat uncertain, but apparently from the lower part of the Vale on the basis of field notes of the collector, C. Sternberg; C.N.H.M. U.R. 113, maxillary with dentition, middle part of Vale Formation, Loc. KH (east end), Knox County, Texas; C.N.H.M. U.R. 109, partial large maxillary with dentition, Loc. KI, base of upper part of Vale Formation, Knox County, Texas; C.N.H.M. U.R. 120, two partial maxillary tooth plates, apparently from same individual, Loc. FA, pipe site, lower part of Choza Forma- tion, Foard County, Texas; C.N.H.M. U.R. Ill, two partial lower 1 This species is named for Mr. Wade Barker of Knox County, Texas, in recognition of the untiring aid that he has given me and my assistants in the course of our field work in Texas. 214 FIELDIANA: GEOLOGY, VOLUME 10 jaws with post-canine dentition partly present, apparently from same individual, Loc. FA, pipe site, lower part of Choza Formation, Foard County, Texas; C.N.H.M. U.R. 112, lower jaw with denti- tion, Loc. FA, pipe site, lower part of Choza Formation, Foard County, Texas. Diagnosis. — Lower jaw with four even rows of bulbous, semi- conical teeth. Maxillary dentition consisting of five regular rows of evenly spaced teeth and forming attenuated, roughly triangular plate with the apex anterior. Discussion. — This species differs from Labidosaurikos meachami Stovall, the type of the genus (Stovall, 1950), in the number of rows of teeth, four below and five above in Labidosaurikos barkeri as com- pared with five (possibly six) below and six above in Labidosaurikos meachami. The available materials suggest that Labidosaurikos barkeri was a somewhat smaller species than Labidosaurikos mea- chami, but this must remain uncertain until larger samples become available for comparison. The stratigraphic range of Labidosaurikos barkeri, as known at present, is from the base of the Vale Formation to the lower part of the Choza. Labidosaurikos meachami is from the Hennessey of Oklahoma, probably in part a Choza equivalent. It would appear, on the basis of the number of rows of dentition and size, that Labidosaurikos meachami was the more advanced species of the two now known. The phylogenetic position of the genus with respect to other captorhinids is considered in the discussion at the end of the paper. Captorhinikos gen. nov. Diagnosis. — Lower jaw with four regular rows of bulbous, sub- conical post-canine teeth. Outer and inner rows not extending full length of post-canine series and not overlapping so that there are but three effective rows at any level. Enlarged "canine" tooth above and below. Maxillary dentition with five rows of bulbous, sub- conical teeth, forming a crescentic tooth plate; teeth increasing in size from anterior and posterior ends of plate to center and rows most widely spaced at center. Skull heart-shaped in outline. Neural spines of vertebrae tending to be better developed than those of Captorhinus. Neural arches broad and flat. Dimensions of various skeletal elements of adults consistently greater than comparable dimensions of large specimens of Captorhinus. Type species. — Captorhinikos valensis sp. nov. OLSON: FAUNA OF VALE AND CHOZA 215 Captorhinikos valensis sp. nov. Figure 86, F-H. Type. — C.N.H.M. U.R. 101. Anterior part of lower jaw and maxillary tooth plate. Horizon and locality. — Upper part of Vale Formation, Clear Fork group, early Permian, Loc. KA, Knox County, Texas. Fig. 86. Captorhinikos. A, B, Captorhinikos chozaensis; type, C.N.H.M. U.R. 97. Ventral and dorsal view of lower jaws. C-E, humerus, tibia and radius of Captorhinikos chozaensis; referred specimen, C.N.H.M. U.R. 100. F- H, Captorhinikos valensis; type, C.N.H.M. U.R. 101. F, G, lower jaw in lateral and dorsal view. H, maxillary in ventral view. A-E, X 1/2; F-H, X 1. Referred specimens. — C.N.H.M. U.R. 107, 7 pre-sacral vertebrae, Loc. KF, middle part of Vale Formation; C.N.H.M. U.R. 108, 6 vertebrae associated with ribs and fragments of dental plates, Loc. KI, base of upper part of Vale Formation; C.N.H.M. U.R. 105, part of lower jaw with teeth, Loc. KH (west end), base of upper part of Vale Formation; C.N.H.M. U.R. 106, 6 vertebrae with ribs and poorly preserved impression of 5 more anterior vertebrae leading toward what appears to be fragments of posterior part of skull, Loc. KB, upper part of Vale Formation; C.N.H.M. U.R. 103, frag- 216 FIELDIANA: GEOLOGY, VOLUME 10 ment of upper tooth plate, Loc. KA, upper part of Vale Formation; C.N.H.M. U.R. 104, part of palate, specific assignment not entirely certain, based on morphology and proximity to jaw of this species, Loc. KA, upper part of Vale Formation; C.N.H.M. U.R. 102, partial lower jaw, Loc. KA, upper part of Vale Formation. Diagnosis. — Lower jaw slender for full length of tooth-bearing portion. Vertebral spines short to moderate in length in pre-sacral part of column. Captorhinikos chozaensis sp. nov. Figure 86, A-E. Type. — C.N.H.M. U.R. 97, lower jaws with fragments of skull including maxillary tooth plates. Horizon and locality. — Middle of lower part of Choza Formation, Clear Fork group, early Permian, Loc. FA, green nodule site, Foard County, Texas. Referred specimens. — C.N.H.M. U.R. 99, part of skeleton includ- ing 6 thoracic vertebrae, part of pelvis, femur, and indeterminate fragments, Loc. FA, pipe site, middle of lower part of Choza Forma- tion; C.N.H.M. U.R. 100, part of skull and skeleton including portion of skull roof, impression of scapula, vertebrae (largely molds), hu- merus, radius, fibula, and various unprepared parts, Loc. FA, Diplocaulus site, top of lower part of Choza Formation. Diagnosis. — Lower jaw expanded dorso-ventrally below region of multiple rows of dentition. Outer rows of teeth in lower jaw set in from lateral margin of lower jaw. Neural spines of thoracic verte- brae high as compared with those of Captorhinikos valensis. Discussion. — The genus Captorhinikos is typically captorhinid in all skeletal features that are known, as shown in the illustrations (figs. 85 and 86). Its closest affinities are with Captorhinus on the one hand and Labidosaurikos on the other. Adults are consistently larger in their various osteological dimensions than the largest speci- mens of Captorhinus, but are markedly smaller than adult specimens of Labidosaurikos. The principal known differences from Captor- hinus have been noted in the generic and specific diagnoses. The regular rows of teeth contrast with the irregular rows in Captorhinus as do the number of rows of teeth above and below, five and four respectively in Captorhinikos, and, roughly, three above and below in Captorhinus. The presence of a single "canine" tooth contrasts with the condition in Captorhinus in which only the first tooth in the pre-maxillary series tends to be markedly larger than adjacent teeth. OLSON: FAUNA OF VALE AND CHOZA 217 Post-cranial differences, excepting those of size, are less pronounced. The most striking is the difference in degree of development of the neural spines, a feature probably associated with the differences in size. Resemblances to Labidosaurikos are evident in the jaws and dentition. Notable are the regularity of the tooth rows, the pres- ence of more than three rows above and below, and the existence of a single, large "canine" tooth, in both Captorhinikos and Labido- saurikos. The bulbous character of the cheek teeth of Captorhinikos is repeated in Labidosaurikos and contrasts with the somewhat flattened crowns of the teeth of Captorhinus. Post-cranial elements in the three genera are similar in most respects so far as is known. Until more adequate materials of Captorhinikos and Labidosaurikos are obtained, detailed comparisons cannot be made. Morphologically, Captorhinikos is nearly intermediate between Captorhinus and Labidosaurikos. Labidosaurikos, however, is known from somewhat earlier deposits than Captorhinikos, for it occurs in the lowest Vale whereas Captorhinikos has not yet been found below the middle Vale. This may be due merely to accidents of preserva- tion and collection. It would seem that Labidosaurikos might have arisen from Captorhinus through Captorhinikos as an intermediate stage, or, perhaps, that the two genera arose independently from Captorhinus and followed somewhat similar evolutionary courses. The first alternative seems somewhat more plausible, inasmuch as the two genera occur in the same geographic area and Labidosaurikos must have passed through a Captorhinikos-\ike stage. It is inter- esting to note, in this regard, that the Choza species of Captorhinikos resembles Labidosaurikos more closely in some features, particularly those of the lower jaw and upper and lower dentition, than does the Vale species. After the origin of the two genera, regardless of the precise derivation of each, parallelism seems to have been important in their continued evolution. The greatest contrasts between the evolutionary development of the two lies in the retention of a Captor- hinus-\ike skull shape by Captorhinikos, the tendency for elongation in the skull of Labidosaurikos, and the tendency toward attainment of greater size exhibited by Labidosaurikos. REFERENCES Olson, E. C. 1948. A preliminary report on vertebrates from the Permian Vale Formation of Texas. Jour. Geol., 56, pp. 186-198, 2 pis., 2 figs. 218 FIELDIANA: GEOLOGY, VOLUME 10 1951a. Vertebrates from the Choza Formation, Permian of Texas. Jour. Geol., 59, pp. 178-181, 1 fig. 1951b. Fauna of upper Vale and Choza: 1-5. Fieldiana, Geology, 10, pp. 89-128, 15 figs. Stovall, J. W. 1950. A new cotylosaur from north central Oklahoma. Amer. Jour. Sci., 248, pp. 46-54, 1 pi. ; —