Atractosteus atrox

Atractosteus atrox Temporal range: Early Eocene PreꞒ Ꞓ O S D C P T J K Pg N ↓
The largest known A. atrox specimen, University of Wyoming
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Clade:	Ginglymodi
Order:	Lepisosteiformes
Family:	Lepisosteidae
Genus:	Atractosteus
Species:	†A. atrox
Binomial name
†Atractosteus atrox (Leidy, 1873)
Synonyms
Lepisosteus atroxLeidy, 1873

Atractosteus atrox (from atrox, Latin for 'savage'), the Green River atrox gar, ^[1] is an extinct species of gar from the Early Eocene of western North America. It is known from many well-preserved specimens found in the famous Fossil Butte deposits of the Green River Formation in Wyoming, US, in addition to a possible vertebra from the Bridger Formation. ^[2]

A close relative of the modern alligator gar (A. spatula), it is the largest fish known from the Green River deposits, with two specimens known to reach at least 7 feet (2.1 m) in length, making A. atrox the largest known prehistoric gar taxon. ^{[3] [4]} It is one of two Atractosteus species known from Fossil Butte alongside A. simplex , from which it can be differed by the characteristic ornamentation on its skull bones, in addition to its larger size. ^[3] There is still significant variation within this species, and it is thus possible that it may represent multiple cryptic species. ^[1]

Close-up of A. atrox teeth

The original type specimen is a single vertebra recovered from the Bridger Formation, which Leidy (1873) named A. atrox, a name he also used for the well-preserved Green River Formation gars. However, this vertebra cannot be confidently assigned to A. atrox and may belong to A. simplex instead; for this reason, Eastman (1900) fixed the name to a more complete Green River specimen instead, which was treated as the "effective type" specimen. ^{[1] [2]}

References

1. Grande, Lance (2010). "An Empirical Synthetic Pattern Study of Gars (lepisosteiformes) and Closely Related Species, Based Mostly on Skeletal Anatomy. the Resurrection of Holostei". Copeia. 2010 (2A): iii–871. ISSN   0045-8511. JSTOR   20787269.
2. "PBDB Taxon". paleobiodb.org. Retrieved 2025-01-23.
3. Grande, Lance (2001), Gunnell, Gregg F. (ed.), "An Updated Review of the Fish Faunas From the Green River Formation, the World's Most Productive Freshwater Lagerstätten" , Eocene Biodiversity: Unusual Occurrences and Rarely Sampled Habitats, Topics in Geobiology, vol. 18, Boston, MA: Springer US, pp. 1–38, doi:10.1007/978-1-4615-1271-4_1, ISBN   978-1-4615-1271-4 , retrieved 2025-01-23
4. Brownstein, Chase Doran; Lyson, Tyler R. (2022-06-15). "Giant gar from directly above the Cretaceous–Palaeogene boundary suggests healthy freshwater ecosystems existed within thousands of years of the asteroid impact". Biology Letters. 18 (6): 20220118. doi:10.1098/rsbl.2022.0118. PMC   9198771 . PMID   35702983.