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STL Science Center
18 April 2017
From Reisz 1977
Some days, as we all know here, the reading list for older discoveries is very small indeed. This is of course thanks to the fact that not everything ever written has been scanned or re-typed and posted online. This is not just an ancient writings problem either; I have had difficulty getting articles from as recent as 1999 online without contacting authors directly. This is important because there are numerous articles on Petrolacosaurus and some of them are slightly older articles. Remember that the small reptile was discovered in Kansas in 1932 but was not described until 1945. There were no field notes associated with the find other than the general locality of Garnett, Kansas; approximately 50 miles south of Lawrence and the University of Kansas. Having worked on a specimen from the University of Kansas Vertebrate Paleontology collections I can attest to the mountain of field records and their sometimes cryptic nature (the specimen I looked at was given the location "locality #12" but no other information) but I have not seen any completely lost field notes in my experience. Regardless of the completeness of field notes, Petrolacosaurus has been described and assigned and somewhat fawned over for decades now as the oldest known diapsid showing transitional characters. Reisz's 1977 article re-describing this old reptile and first diapsid possesses a very iconic, though general appearing, line drawing of the skull of this reptile which could easily stand in for any and all early diapsids and might be confused by some to represent a modern lizard of some kind. Petrolacosaurus has been used to describe the evolution of not only reptiles as a whole, but also in describing the origin of one of the bones making up the ankle joint, the astragalus (known as the talus in humans). This Peabody paper from 1951 is not only interesting, but important in understanding the evolutionary origins of a bone that was important for reptiles, crocodiles, pterosaurs, and dinosaurs and birds. Petrolacosaurus is a very important animal in the history of evolution despite its small size and these papers make that quite evident. Enjoy reading them and discovering more about the origin of reptiles!