Tanaocrossus

Tanaocrossus
Temporal range: Carnian–Rhaetian
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: †Scanilepiformes
Genus: †Tanaocrossus
Schaeffer, 1967
Species:
†T. kalliokoskii
Binomial name
†Tanaocrossus kalliokoskii
Schaeffer, 1967

Tanaocrossus (Ancient Greek for "outstretched fringe", referring to its distinctive dorsal fin) is an extinct genus of primitive freshwater ray-finned fish that inhabited southwestern and eastern North America during the Late Triassic period. It contains a single known species, T. kalliokoskii, known from the United States, with indeterminate species also known.[1][2]

It is primarily known from the Norian to Rhaetian of the Chinle Formation of Colorado and Utah.[3][4][5] Indeterminate remains are known from the Dockum Group of Texas and New Mexico (Bull Canyon Formation).[3][6] A single fragmentary but distinctive fossilized fin from the earlier Carnian-aged Doswell Formation of Virginia, which shares the genus's distinctive fin rays, was long the only record from the eastern United States, but a partial specimen was also later identified from the Manassas Sandstone.[4][6][7]

Morphologically, it can be easily distinguished from other co-occurring fishes by its highly elongated dorsal fin that stretches across its body. Its taxonomic affiliations have long been enigmatic since its description due to its unusual morphology.[2][7][4] More recent studies have found it to be a scanilepiform, an enigmatic order of fish which were later found to most likely be basal cladistians, which would make it a distant relative of modern bichirs.[8][9] A 2008 study questioned this assignment and instead reclassified it to the Perleidiformes, but this has been disputed by later studies.[10][8][11]

It was likely a slow-moving fish that inhabited quiet waters, with its dorsal fin allowing for undulation while swimming.[2]

References

  1. ^ "PBDB Taxon". paleobiodb.org. Retrieved 2024-09-19.
  2. ^ a b c Schaeffer, Bobb (1967). "Late Triassic fishes from the western United States". Bulletin of the AMNH. 135 (6).
  3. ^ a b Heckert, Andrew B.; Lucas, Spencer G. (2005). Vertebrate Paleontology in Arizona: Bulletin 29. New Mexico Museum of Natural History and Science.
  4. ^ a b c Schaeffer, Bobb; McDonald, Nicholas G. (1978). "Redfieldiid fishes from the Triassic-Liassic Newark Supergroup of eastern North America. Bulletin of the AMNH ; v. 159, article 4". Bulletin of the American Museum of Natural History. 159 (4): 131–173.
  5. ^ Gibson, Sarah Z. (2016-09-22). Schubert, Michael (ed.). "Redescription and Phylogenetic Placement of †Hemicalypterus weiri Schaeffer, 1967 (Actinopterygii, Neopterygii) from the Triassic Chinle Formation, Southwestern United States: New Insights into Morphology, Ecological Niche, and Phylogeny". PLOS ONE. 11 (9): e0163657. doi:10.1371/journal.pone.0163657. ISSN 1932-6203. PMC 5033578. PMID 27657923.
  6. ^ a b Romano, Carlo; Koot, Martha B.; Kogan, Ilja; Brayard, Arnaud; Minikh, Alla V.; Brinkmann, Winand; Bucher, Hugo; Kriwet, Jürgen (2016). "Permian-Triassic Osteichthyes (bony fishes): diversity dynamics and body size evolution (supplementary material)". Biological Reviews of the Cambridge Philosophical Society. 91 (1): 106–147. doi:10.1111/brv.12161. ISSN 1469-185X. PMID 25431138.
  7. ^ a b Weems, Robert E. (2018). "A SYNOPSIS OF THE VERTEBRATE FAUNA FROM THE CULPEPER BASIN (UPPER TRIASSIC-LOWER JURASSIC, MARYLAND AND VIRGINIA)". New Mexico Museum of Natural History and Science Bulletin. 79.
  8. ^ a b Xu, Guang-Hui; Gao, Ke-Qin (2011). "A new scanilepiform from the Lower Triassic of northern Gansu Province, China, and phylogenetic relationships of non-teleostean Actinopterygii: EARLY TRIASSIC SCANILEPIFORM FROM CHINA". Zoological Journal of the Linnean Society. 161 (3): 595–612. doi:10.1111/j.1096-3642.2010.00645.x.
  9. ^ Giles, Sam; Xu, Guang-Hui; Near, Thomas J.; Friedman, Matt (2017). "Early members of 'living fossil' lineage imply later origin of modern ray-finned fishes". Nature. 549 (7671): 265–268. doi:10.1038/nature23654. ISSN 1476-4687. PMID 28854173.
  10. ^ Milner, Andrew; Spears, Sarah; Olsen, Paul (2008). "NEW SPECIMENS OF TANAOCROSSUS (ACTINOPTERYGII, PERLEIDIFORMES) FROM THE LATE TRIASSIC CHINLE FORMATION OF THE WESTERN UNITED STATES" (PDF). Society of Vertebrate Paleontology.
  11. ^ Xu, Guang-Hui; Gao, Ke-Qin; Finarelli, John A. (2014-06-07). "A revision of the Middle Triassic scanilepiform fish Fukangichthys longidorsalis from Xinjiang, China, with comments on the phylogeny of the Actinopteri". Journal of Vertebrate Paleontology. 34 (4): 747–759. doi:10.1080/02724634.2014.837053. ISSN 0272-4634.