Chapter IV. 



DESCRIPTION OF A NEARLY COMPLETE SKELETON OF DIASPARACTUS 



ZENOS CASE. 



By E. C. Case and S. W. Williston. 



The Specimen here described was found by Case in a reddish, clayey sandstone 

 somewhat below the middle of the Permo-Carboniferous strata of El Cobre Canon, 

 in Rio Arriba County, New Mexico. When discovered, only a fragment of a tooth 

 was exposed, but excavation revealed nearly the entire skeleton. As the skull was, 

 unfortunately, near the surface, it is badly injured by weathering, and a portion 

 of the upper surface was destroyed before fossilization, but enough remains to 

 reveal by careful study most of the important characters. The atlantal and axial 

 intercentra are preserved; the atlas is lost; the axis is preserved, but is separated 

 from the rest of the vertebral column. Beginning with the third cervical, there 

 is a series of five vertebras in connection with the scapuls, the clavicles, and the 

 interclavicle. The posterior portion of the scapula of the left side is destroyed, 

 but that of the right side, the clavicles of both sides, and the interclavicle, with 

 the exception of the tip of the distal end, are perfect. Following the break between 

 the sixth and the seventh vertebrae the series is complete to the twenty-third 

 caudal. Though no fit can be found between the sixth and the seventh vertebrse 

 the series was in position when excavated by Case and no reasonable doubt can 

 be entertained that the relations are as described. This is bome out by the 

 close relation which exists between the number of presacral vertebrae in this speci- 

 men and that found in other members of the same family, the Diadectidae. The 

 neural spines of many of the dorsal vertebrae and all but one of the caudals have 

 been destroyed. The pelvis and the limb bones of both sides have been preserved 

 in large part. The right ilium has lost the crest. All of the long bones of the Hmbs 

 are preserved, but the carpus and tarsus and the phalanges of both sides have been 

 more or less disturbed and many of the bones lost. Only a few of the ribs have 

 been preserved, and only the base of a single chevron. No trace of abdominal 

 ribs can be detected. This is in accord with the other specimens of this family 

 recovered, where no trace of such structures has been seen, though they would 

 certainly be expected. 



In 1 9 ID Case * described a short series of posterior dorsal and sacral vertebrae 

 (Am. Mus. Nat. Hist. Cope Coll. No. 4794) from New Mexico and proposed the 

 name Diasaparactus zenos to designate them. The posterior dorsal vertebrae of 

 this specimen agree so closely with the described type that it seems best to retain 

 the name for this specimen. 



The weathered condition of portions of the specimen, the refractory nature of 

 the matrix, in places, and the softer substance of the bones has rendered the prep- 

 aration of the specimen very difficult, and it is to the painstaking care and skill 

 of the preparator, Mr. Paul Miller, of the University of Chicago, that we owe 

 our ability to describe the specimen so completely. 



The skull: Lying close to the surface and being badly broken by weathering, 

 the skull is imperfectly preserved and its study has been exceptionally difficult, 



*Bull. Am. Mus. Nat. Hist., vol. xxvin, art. xvii, p. 174, 1910. 



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