Basiloterus
Basiloterus | |
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Mammalia |
Order: | Artiodactyla |
Infraorder: | Cetacea |
Family: | †Basilosauridae |
Genus: | †Basiloterus Gingerich et al., 1997 |
Species: | †B. husseini
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Binomial name | |
†Basiloterus husseini Gingerich et al., 1997
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Basiloterus is an extinct genus of late-
History and naming
The fossil remains of Basiloterus were discovered in 1996 in the green shales that compose the middle parts of the Drazinda Formation in Pakistan. The genus was described in 1997 by Gingerich et al. alongside the species Basilosaurus drazindai on the basis of two lumbar vertebrae thought to represent a single individual. Gingerich and colleagues tentatively refer a vertebral centrum from the Barton Group of England to this genus as well on the basis of its age, size and general morphology.[1]
The scientific name derives from the
Description
Basiloterus differs from species of Basilosaurus in that the
The transverse processes, which project from the sides of the centrum, are described as being oriented anteroventrally. This downturned state is thought to allow for an increased arc of movement of the
The laminae at the base of the
According to Gingerich and colleagues, Basiloterus was smaller than Basilosaurus, and Gol'din & Zvonok state that the vertebrae are of similar size to those of Basilotritus.[2] The size of the vertebrae has also been compared to Pachycetus robustus, with Gingerich determining that those of Basiloterus were around 25% larger.[1]
Phylogeny
Gingerich and colleagues considered Basiloterus to be a close relative of Basilosaurus based on the size and shape of the lumbar vertebrae as well as the fact that the two genera were contemporary.[1] Later, Mark D. Uhen argued that this first identification may not be as certain as initially believed. Although Uhen agrees that elongated vertebrae are a distinguishing feature of basilosaurines within the family Basilosauridae, he also points out that other groups evolved this trait independently. According to Uhen, this means that Basiloterus and Basilosaurus drazindai could also be protocetids similar to Eocetus, which also developed elongated vertebrae.[3] While few papers examined or even acknowledge Basiloterus following the type description, those that do feature it continue to regard it as a basilosaurid.[3][4][5][6]
The phylogenetic tree provided by Uhen in 2009's Encyclopedia of Marine Mammals suggests a paraphyletic Basilosauridae leading up to modern cetaceans,[3] although some more recent studies have proposed monophyletic solutions for Basilosauridae as well.[4] Despite his reservations towards the identity of Basiloterus as a basilosaurine, the tree still depicts it as the immediate sister taxon to Basilosaurus as proposed by Gingerich and colleagues.[3]
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The elongation of the vertebrae as a convergent trait is again noted by Gol'din and Zvonok, who propose that it had been independently gained by Basiloterus, Basilotritus and Basilosaurus. They argue that this independent acquisition of elongated lumbars renders it an unreliable character to separate the subfamilies Basilosaurinae and Dorudontinae, further supported by the close relationship they recover between Basilosaurus and Dorudon. In their results, Dorudon is the closest relative of Basilosaurus in place of Basiloterus, which is not included in their results.[2] Similar results also appear in later papers such as the description of the small-bodied basilosaurid Tutcetus, which also argues against the concept of a distinct Basilosaurinae and Dorudontinae and does not discuss Basiloterus.[7] The description of Cynthiacetus peruvianus also fails to recover two distinct subfamilies and simply refers to Basiloterus as a basilosaurid of uncertain relation to the other taxa within the family.[4]
Paleobiology
Although not found in the same area, Basiloterus likely coexisted with Basilosaurus drazindai as they both come from the same green shales of the Drazinda Formation,
See also
References
- ^ a b c d e f g h Gingerich, Philip D.; Arif, M.; Bhatti, M. Akram; Anwar, M.; Sanders, William J. (1997). "Basilosaurus drazindai and Basiloterus hussaini, New Archaeoceti (Mammalia, Cetacea) from the Middle Eocene Drazinda Formation, with a Revised Interpretation of Ages of Whale-Bearing Strata in the Kirthar Group of the Sulaiman Range, Punjab (Pakistan)" (PDF). Contributions from the Museum of Paleontology, University of Michigan. 30 (2): 55–81.
- ^ .
- ^ ISBN 978-0-12-373553-9.
- ^ S2CID 90142285.
- PMID 33062412.
- S2CID 86600469.
- PMID 37563270.
- ^ Head, J.J.; Raza, S.M.; Gingerich, P.D. (1999). "DRAZINDERETES TETHYENSIS, A NEW LARGE TRIONYCHID (REPTILIA: TESTUDINES) FROM THE MARINE EOCENE DRAZINDA FORMATION OF THE SULAIMAN RANGE, PUNJAB (PAKISTAN)". Contributions from the Museum of Paleontology University of Michigan. 30 (7): 199–214.