Atractosteus simplex

{{Short description|Extinct species of fish}}

{{Speciesbox

| fossil_range = {{fossil range|51|49|Early Eocene}}

| image = Atractosteus simplex eldarimg1.jpg

| image_caption = Fossil specimen, University of Wyoming

| extinct = yes

| taxon = Atractosteus simplex

| authority = (Leidy, 1873)

| synonyms = * Lepisosteus simplex Leidy, 1873

}}

Atractosteus simplex (from simplex, Latin for "simple", likely referring to the smooth scales), the simplex gar{{Cite journal |last=Grande |first=Lance |date=2010 |title=An Empirical Synthetic Pattern Study of Gars (lepisosteiformes) and Closely Related Species, Based Mostly on Skeletal Anatomy. the Resurrection of Holostei |url=https://www.jstor.org/stable/20787269 |journal=Copeia |volume=2010 |issue=2A |pages=iii–871 |issn=0045-8511}}, 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.{{Cite web |title=PBDB Taxon |url=https://paleobiodb.org/classic/basicTaxonInfo?taxon_no=501819 |access-date=2025-01-23 |website=paleobiodb.org}}

It was a close relative of the modern alligator gar (A. spatula), and one of two Atractosteus species known from Fossil Butte alongside the even larger A. atrox. It can be differentiated from the sympatric A. atrox by its lower number of lateral line scales and vertebrae, and reaching only {{Convert|1|m|ft}} in length.{{Citation |last=Grande |first=Lance |title=An Updated Review of the Fish Faunas From the Green River Formation, the World’s Most Productive Freshwater Lagerstätten |date=2001 |work=Eocene Biodiversity: Unusual Occurrences and Rarely Sampled Habitats |pages=1–38 |editor-last=Gunnell |editor-first=Gregg F. |url=https://link.springer.com/chapter/10.1007/978-1-4615-1271-4_1 |access-date=2025-01-23 |place=Boston, MA |publisher=Springer US |language=en |doi=10.1007/978-1-4615-1271-4_1 |isbn=978-1-4615-1271-4|url-access=subscription }} It is the most abundant of the six gar species known from the Green River Formation, although even the 100-200 excavated specimens of this species are a minute percentage of the over 500,000 fossil fish specimens recovered from the formation.

A. simplex was a highly predatory fish, with one fossil specimen preserving a young Diplomystus in its jaws. Another specimen preserves coprolites in its mouth, representing the first instance of coprolites being found within a fossilized vertebrate's mouth. As gars are not known to engage in coprophagy, this is thought to likely represent an accidental ingestion or a consequence of taphonomy.{{Cite journal |last=Frandsen |first=George |last2=Godfrey |first2=Stephen J. |date=2019 |title=A gar-bitten coprolite from the Eocene Green River Formation near Kemmerer, Wyoming, U.S.A |url=https://www.researchgate.net/profile/Stephen-Godfrey-2/publication/359716994_Frandsen_and_Godfrey_2019_Green_River_Coprolites_in_Gar/links/624aef6a57084c718b867043/Frandsen-and-Godfrey-2019-Green-River-Coprolites-in-Gar.pdf |journal=The Ecphora |volume=34 |issue=1 |pages=3-4}}

The original type specimen is a skull fragment and some vertebrae recovered from the Bridger Formation, which Leidy (1873) named A. simplex, a name he also used for the well-preserved Green River Formation gars. However, this vertebra cannot be confidently assigned to A. simplex and may belong to A. atrox or Lepisosteus bemisi 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.