OPISTHIAS (SPHENODONTIA) FROM THE AARON SCOTT QUARRY (MORRISON FORMATION, JURASSIC PERIOD) OF CENTRAL UTAH

The Aaron Scott Quarry in central Utah (Jurassic Period) is unusual in that microfossils and macrofossils are found together. In the quarry several specimens of Opisthias sp. have been recovered. These specimens represent at least four individuals. Specimens include two maxilla, one pterygoid, and four dentaries. The four dentaries exhibit variations that suggest they are from different individuals and possibly different species. A.S.Q. 840 is a dentary with long narrow teeth and almost no gap between the back tooth and the ascending ramus. CMC VP 7797 has broader teeth and a significant gap between the back tooth and the ascending ramus. CMC VP 8550 is a complete dentary with a long and narrow jaw and a significant gap between the incisoform tooth and the back teeth and the teeth overlap. The ascending ramus is missing. CMC VP 7796 is a complete dentary that is unique in that it is short but tall with no gap between the incisoform tooth and the back teeth and no gap between the back tooth and the ascending ramus. CMC VP 8627 is the back half of a maxilla with teeth comparable to CMC VP 7797 and may be the same individual. CMC 8586 is the front half of a maxilla with teeth comparable to CMC VP 7797. A.S.Q. is a palate with small, narrow teeth. The variability in these specimens suggest at least two different species of Opisthias from this site.