The San Angelo Formation is a geologic formation in Texas . It preserves fossils dating back to the Permian period . Along with the Chickasha Formation is one of the two geologically youngest formations in North America to preserve fossils of caseids , and it is the youngest one to preserve remains of undoubted sphenacodontids , namely, Dimetrodon angelensis .
6-691: Some studies argued that the San Angelo Formation belongs to the Kungurian stage of the Cisuralian series because it underlies the Blaine Formation , which is, according to the same studies, either upper Kungurian or lower Guadalupian . However, a recent study concluded that Olson was correct in regarding the San Angelo Formation as belonging to the Roadian , and that the Blaine Formation also dates from
12-576: Is named after the Russian city of Kungur in Perm Krai . The stage was introduced into scientific literature by Russian geologist Alexandr Antonovich Stukenberg (Alexander Stuckenberg) in 1890. The base of the Kungurian Stage is defined as the place in the stratigraphic record where fossils of conodont species Neostreptognathodus pnevi and Neostreptognathodus exculptus first appear. As of 2009, there
18-587: The Permian period is a stub . You can help Misplaced Pages by expanding it . Kungurian In the geologic timescale , the Kungurian is an age or stage of the Permian . It is the latest or upper of four subdivisions of the Cisuralian Epoch or Series . The Kungurian lasted between 283.5 and 273.01 million years ago (Ma) . It was preceded by the Artinskian and followed by the Roadian . The Kungurian
24-479: The Roadian . Everett C. Olson regarded the San Angelo Formation as preserving some of the oldest known therapsids , several of which he classified in a taxon he called Eotheriodonta. These taxa are now interpreted as caseids and sphenacodontids , not therapsids. This article about a specific stratigraphic formation in Texas is a stub . You can help Misplaced Pages by expanding it . This article related to
30-480: The fossil record, and the end of this stage whitnessed one of the greatest faunal turnovers of the Permian . Early studies placed Olson’s Extinction just after the Kungurian, but more recent studies only indicate that this possible extinction event is located around Kungurian/ Roadian boundary. Howerver, higher-resolution stratigraphic data suggest that this even is actually a slow decline over 20 Ma that started in
36-615: Was no agreement yet on a global reference profile (a GSSP ) for the base of the Kungurian. The top of the Kungurian (the base of the Roadian and the Guadalupian series) is defined as the place in the stratigraphic record where fossils of conodont species Jinogondolella nanginkensis first appear. The Kungurian contains three conodont biozones : The Kungurian is the last stage in which many Permo-Carboniferous clades of vertebrates ( Seymouria , ophiacodontids , edaphosaurids , etc.) occur in
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