Talk:San Angelo Formation

Synapsids in the San Angelo

Hello all,

I edited the section that formerly indicated that this formation included some of the last known "pelycosaurs", for two reasons. First, this was factually wrong; there are more recent caseids in Russia, notably Ennatosaurus tecton, which occurs in the Kazanian (a Russian local stage now widely admitted to correspond to the Roadian), most probably later in the Roadian than the San Angelo. The most recent dating I have of this is a personal communication by e-mail by Valeriy Golubev (a Russian specialist of the Kazanian) dating from June 2021, in which he indicated that both localities where E. tecton was found (Moroznitsa and Nisogora) are Roadian. Moroznitsa (middle Early Kazanian, Kamyshlian Beds) is slightly earlier than Nisogora (lower Upper Kazanian). Second, "pelycosaurs" are paraphyletic, and as such, artificial. It is more informative to discuss its component clades, which became extinct at different times, from the late Kungurian to early Roadian (Ophiacodontidae and Edaphosauridae) to later in the Roadian (Sphenacodontidae first, and later, Caseidae), and even Capitanian (Varanopidae). About the latter, see this paper: MODESTO, S. P., SMITH, R. M. H., CAMPIONE, N. S. E., and REISZ, R. R. 2011. The last “pelycosaur”: A varanopid synapsid from the pristerognathus assemblage zone, middle permian of south africa. Naturwissenschaften 98 (12): 1027–1034. Michel Laurin (talk) 07:28, 5 January 2024 (UTC)