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 atrox Leidy, 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]

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

^ ^a ^b ^c 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.
^ ^a ^b "PBDB Taxon". paleobiodb.org. Retrieved 2025-01-23.
^ ^a ^b 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
^ 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.

[:0-1] 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.

[:1-2] "PBDB Taxon". paleobiodb.org. Retrieved 2025-01-23.

[:2-3] 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.

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