San Angelo Formation

Last updated
San Angelo Formation
Stratigraphic range: Kungurian
Type Formation
Unit of Pease River Group
Underlies Blaine Formation
Overlies Clear Fork Group
Location
Region Texas
Country United States

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. [1] [2]

Contents

Stratigraphy and age

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. [3] [4] 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 the Roadian. [2]

Fossil content

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. [1] These taxa are now interpreted as caseids and sphenacodontids, not therapsids. [5]

Color key
Taxon Reclassified taxonTaxon falsely reported as presentDubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon
Notes
Uncertain or tentative taxa are in small text; crossed out taxa are discredited.

Synapsids

GenusSpeciesLocationMaterialNotesImages
Angelosaurus A. dolaniA caseid
Caseoides C. sanangeloensisA caseid
Caseopsis C. agilisA caseid
Cotylorhynchus C. hancockiA caseid
Dimacrodon D. hottoni
Dimetrodon D. angelensisA sphenacodontid
Driveria D. ponderosa
Eosyodon E. hudsoniA dubious sphenacodontid [6]
Gorgodon G. minutus
Knoxosaurus K. niteckii
Mastersonia M. driverensis
Tappenosaurus T. magnusA possible sphenacodontid [7]

See also

References

  1. 1 2 Olson 1962.
  2. 1 2 Laurin, Michel; Hook, Robert W. (2022). "The age of North America's youngest Paleozoic continental vertebrates: a review of data from the Middle Permian Pease River (Texas) and El Reno (Oklahoma) Groups". BSGF - Earth Sciences Bulletin. 193: 10. doi:10.1051/bsgf/2022007.
  3. DiMichele et al. 2001.
  4. Lucas & Golubev 2019.
  5. Sidor & Hopson 1995.
  6. Kammerer 2011, p. 291.
  7. Laurin, Michel; Hook, Robert W. (2022-08-05). "The age of North America's youngest Paleozoic continental vertebrates: a review of data from the Middle Permian Pease River (Texas) and El Reno (Oklahoma) Groups". Bulletin de la Société Géologique de France. 193 (1): 10. doi:10.1051/bsgf/2022007. ISSN   0037-9409.

Bibliography