Pachycormiformes Explained

Pachycormiformes is an extinct order of marine ray-finned fish known from the Early Jurassic to the end of the Cretaceous. It only includes a single family, Pachycormidae. They were characterized by having serrated pectoral fins (though more recent studies demonstrated that fin shape diversity in this group was high[1]), reduced pelvic fins and a bony rostrum. Pachycormiformes are morphologically diverse, containing both tuna and swordfish-like carnivorous forms, as well as edentulous suspension-feeding forms.

Description

Pachycormiformes are united by "a compound bone (rostrodermethmoid) forming the anterodorsal border of the mouth; a reduced coronoid process of the mandible; absence of supraorbitals associated with a dermosphenotic defining the dorsal margin of the orbit; two large, plate-like suborbital bones posterior to the infraorbitals; long, slender pectoral fins; asymmetrical branching of pectoral fin lepidotrichia; considerable overlap of the hypurals by caudal fin rays (hypurostegy); and the presence of distinctive uroneural-like ossifications of the caudal fin endoskeleton".[2] Pachycormiformes varied substantially in size, from medium-sized fishes around NaNcm (-2,147,483,648inches) in length like the macropredator Pachycormus,[3] to the largest known ray-finned fish, the suspension feeding Leedsichthys, which is estimated to have reached a maximum length of around 16m (52feet).[4]

Relationships

Pachycormiformes are generally interpreted as basal members of Teleosteomorpha, the group that includes all fish more closely related to modern teleosts than to Holostei (the group containing bowfin and gars), often they have been considered to be the sister group of the Aspidorhynchiformes.[5] [6]

Taxonomy

Taxonomy according to Cooper et al. (2022):[7]

Cladistics according to Friedman et al. (2010).[9]

Notes and References

  1. Liston. Jeff J.. Maltese. Anthony E.. Lambers. Paul H.. Delsate. Dominique. Harcourt-Smith. William E. H.. Heteren. Anneke H. van. 2019-11-07. Scythes, sickles and other blades: defining the diversity of pectoral fin morphotypes in Pachycormiformes. PeerJ. en. 7. e7675. 10.7717/peerj.7675. 31720097. 6842561. 2167-8359 . free .
  2. Dobson. Claire. Giles. Sam. Johanson. Zerina. Liston. Jeff. Friedman. Matt. 2019-09-03. Cranial osteology of the Middle Jurassic (Callovian) Martillichthys renwickae (Neopterygii, Pachycormiformes) with comments on the evolution and ecology of edentulous pachycormiforms. Papers in Palaeontology. 7. 111–136. 10.1002/spp2.1276. 2027.42/167090 . 202919395. 2056-2802. free.
  3. Gouiric-Cavalli . Soledad . Cione . Alberto Luis . 2015-07-04 . Notodectes is the first endemic pachycormiform genus (Osteichthyes, Actinopterygii, Pachycormiformes) in the Southern Hemisphere . Journal of Vertebrate Paleontology . en . 35 . 4 . e933738 . 10.1080/02724634.2014.933738 . 0272-4634. 11336/13733 . free .
  4. Book: Liston, J., Newbrey, M., Challands, T., and Adams, C., 2013 . Mesozoic Fishes 5 – Global Diversity and Evolution . Verlag Dr. Friedrich Pfeil . 9783899371598 . Arratia, G., Schultze, H. and Wilson, M. . München, Germany . 145–175 . Growth, age and size of the Jurassic pachycormid Leedsichthys problematicus (Osteichthyes: Actinopterygii) . 2013 . https://eprints.gla.ac.uk/81797/1/81797.pdf.
  5. Peskin. Brianna. Henke. Katrin. Cumplido. Nicolás. Treaster. Stephen. Harris. Matthew P.. Bagnat. Michel. Arratia. Gloria. 2020-07-20. Notochordal Signals Establish Phylogenetic Identity of the Teleost Spine. Current Biology. en. 30. 14. 2805–2814.e3. 10.1016/j.cub.2020.05.037. 32559448. 8159021 . 0960-9822.
  6. Arratia . Gloria . 2017-03-04 . New Triassic teleosts (Actinopterygii, Teleosteomorpha) from northern Italy and their phylogenetic relationships among the most basal teleosts . Journal of Vertebrate Paleontology . en . 37 . 2 . e1312690 . 10.1080/02724634.2017.1312690 . 0272-4634.
  7. Cooper . S. L. A. . Giles . S. . Young . H. . Maxwell . E. E. . A New Large †Pachycormiform (Teleosteomorpha: †Pachycormiformes) from the Lower Jurassic of Germany, with Affinities to the Suspension-Feeding Clade, and Comments on the Gastrointestinal Anatomy of Pachycormid Fishes . Diversity . 2022 . 14 . 12 . 1026 . 10.3390/d14121026. free .
  8. Gouiric-Cavalli . S. . Arratia . G. . A new †Pachycormiformes (Actinopterygii) from the Upper Jurassic of Gondwana sheds light on the evolutionary history of the group . Journal of Systematic Palaeontology . 2022 . 19 . 21 . 1517–1550 . 10.1080/14772019.2022.2049382. 248454343 .
  9. Matt Friedman. Kenshu Shimada. Larry D. Martin. Michael J. Everhart. Jeff Liston. Anthony Maltese. Michael Triebold. 2010. 100-million-year dynasty of giant planktivorous bony fishes in the Mesozoic seas.. Science. 327. 5968. 990–993. 10.1126/science.1184743. 20167784. 2010Sci...327..990F . 206524637.

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