Astephus

{{Short description|Extinct genus of fishes}}

{{Automatic taxobox

| fossil_range = {{fossil range|60|33|Late Paleocene to Early Oligocene}}

| image = Astephus antiquus as Ameiurus primaevus holotype USNM V 8122 img1.jpg

| image_caption = Specimen of A. antiquus, National Museum of Natural History

| parent_authority = Grande & Lundberg, 1988

| display_parents = 2

| taxon = Astephus

| authority = Cope, 1873

| type_species = {{extinct}}Pimelodus antiquus

| type_species_authority = Leidy, 1873

| subdivision_ranks = Species

| subdivision = * †A. antiquus (Leidy, 1873)

• †A. resimus Lundberg, 1975

| synonyms =

}}

Astephus is an extinct genus of freshwater catfish known from the Paleogene of western North America. It is the only member of the family Astephidae.{{Cite web |title=PBDB Taxon |url=https://paleobiodb.org/classic/basicTaxonInfo?taxon_no=348172 |access-date=2025-04-06 |website=paleobiodb.org}}{{Cite journal |last=Grande |first=Lance |last2=and Lundberg |first2=John G. |date=1988-06-22 |title=Revision and redescription of the genus Astephus (Siluriformes: Ictaluridae) with a discussion of its phylogenetic relationships |url=https://www.tandfonline.com/doi/abs/10.1080/02724634.1988.10011694 |journal=Journal of Vertebrate Paleontology |volume=8 |issue=2 |pages=139–171 |doi=10.1080/02724634.1988.10011694 |issn=0272-4634|url-access=subscription }}{{Cite journal |last=Laan |first=Richard van der |date=2018-10-11 |title=Family-group names of fossil fishes |url=https://europeanjournaloftaxonomy.eu/index.php/ejt/article/view/597 |journal=European Journal of Taxonomy |language=en |issue=466 |doi=10.5852/ejt.2018.466 |issn=2118-9773}}

Previously, it was considered potentially the oldest representative of the extant family of North American catfishes (Ictaluridae). However, more recent studies have found it to be a basal catfish that is not closely related to the Ictaluridae, and have thus placed it in its own family.{{Cite journal |last=Arce-H. |first=Mariangeles |last2=Lundberg |first2=John G. |last3=O'Leary |first3=Maureen A. |date=2017 |title=Phylogeny of the North American catfish family Ictaluridae (Teleostei: Siluriformes) combining morphology, genes and fossils |url=https://onlinelibrary.wiley.com/doi/10.1111/cla.12175 |journal=Cladistics |language=en |volume=33 |issue=4 |pages=406–428 |doi=10.1111/cla.12175 |issn=1096-0031}}

There are two known species. A. antiquus (Leidy, 1873) is known from many well-preserved specimens the Early Eocene-aged Green River Formation of Colorado, Utah, and Wyoming. It is one of two catfishes known from the formation alongside Hypsidoris. They are especially common in the oil shales of the Laney Member of the formation.{{Cite journal |last=Buchheim |first=H. Paul |last2=Surdam |first2=Ronald C. |date=1977-04-01 |title=Fossil catfish and the depositional environment of the Green River Formation, Wyoming |url=https://pubs.geoscienceworld.org/gsa/geology/article-abstract/5/4/196/195354/Fossil-catfish-and-the-depositional-environment-of |journal=Geology |volume=5 |issue=4 |pages=196–198 |doi=10.1130/0091-7613(1977)5<196:FCATDE>2.0.CO;2 |issn=0091-7613|url-access=subscription }} A. resimus Lundberg, 1975 is known only from a single incomplete neurocranium from the Early Eocene-aged Bridger Formation of Wyoming.{{Cite journal |last=Divay |first=Julien D. |last2=and Murray |first2=Alison M. |date=2016-11-01 |title=The fishes of the Farson Cutoff Fishbed, Bridger Formation (Eocene), greater Green River Basin, Wyoming, U. S. A. |url=https://www.tandfonline.com/doi/full/10.1080/02724634.2016.1212867 |journal=Journal of Vertebrate Paleontology |volume=36 |issue=6 |pages=e1212867 |doi=10.1080/02724634.2016.1212867 |issn=0272-4634|url-access=subscription }} In addition to these described species, an indeterminate Astephus species is known from the Late Paleocene-aged Polecat Bench Formation of Wyoming. Indeterminate remains of Astephus, potentially representing two species, have also been identified from the Late Eocene/Early Oligocene-aged deposits from the Cypress Hills Formation of Saskatchewan.{{Cite journal |last=Divay |first=Julien D. |last2=and Murray |first2=Alison M. |date=2015-07-04 |title=The late Eocene–early Oligocene ichthyofauna from the Eastend area of the Cypress Hills Formation, Saskatchewan, Canada |url=https://www.tandfonline.com/doi/full/10.1080/02724634.2014.956877 |journal=Journal of Vertebrate Paleontology |volume=35 |issue=4 |pages=e956877 |doi=10.1080/02724634.2014.956877 |issn=0272-4634|url-access=subscription }}