Hemisyntrachelus
| Hemisyntrachelus | |
|---|---|
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| Hemisyntrachelus cortesii skull | |
Scientific classification 
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| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Artiodactyla |
| Infraorder: | Cetacea |
| Family: | Delphinidae |
| Subfamily: | Orcininae |
| Genus: | †Hemisyntrachelus Brandt 1873 |
| Species | |
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| Synonyms | |
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Delphinus cortesii | |
Hemisyntrachelus is an extinct genus of cetacean.[1][2][3] This genus is known in the fossil record from the latest Miocene to the Quaternary (age range: from 5.332 to 1.806 million years ago). Fossils are found in the marine strata of Italy, the Netherlands, the Bahía Inglesa Formation of the Caldera Basin, Chile and in the fossiliferous Pisco Formation of Peru.[2][3]
Description
The body length of about Hemisyntrachelus was 3.5–5.5 m (11–18 ft). Its large body size suggests that Hemisyntrachelus was a major predator in the ecosystem of that era. Its large body and awl-shaped teeth covered in thin enamel are similar in structure to modern macroraptorial dolphins.[3]It is similar to modern orca in that its teeth are fewer items and large.[4]
Species
Currently, the genus Hemisyntrachelus contains three species.[2][3] H. cortesii lived about three million years ago (from 3.6 to 2.588 mya).[3] Its fossil skeleton reaches a length of about 3.5 metres (11 ft) and it has been found only in La Torrazza, Italy. Its length during its lifetime is thought to be 4 m (13 ft). This species shows intermediate characters between the bottlenose dolphin and the killer whale. It fed on large fishes and squids. H. oligodon lived from 7.246 to 5.332 million years ago. Fossils have been found only in the Pisco Formation of Peru. This species body length reached 4–4.5 m (13–15 ft), and was one of the macroraptorial at the time.[3] H. pisanus could reach a length of about 5.5 metres (18 ft) and was widespread in the Mediterranean Sea during the Miocene. Fossils have been found only in Orciano, which is in a Piacenzian coastal claystone in Italy.
Paleobiology
Hemisyntrachelus occupied an ecological niche similar to that of modern false killer whale and bottlenose dolphin.[5] Hemisyntrachelus likely consumed a diverse diet ranging from medium to large bony fish and squid to small marine mammals. It is thought to have had a diet similar to that of modern false killer whales and to have engaged in opportunistic hunting.[5][6][7] Fossil evidence suggests that Hemisyntrachelus was preyed upon by sharks such as the great white shark (Carcharodon carcharias) and the related Carcharodon plicatilis. It is possible that they formed groups similar to modern dolphins to defend against these predators.[8]
Paleoecology
Contemporary predators included Orcinus citoniensis and the giant shark Otodus megalodon. Coinciding with the occurrence of Hemisyntrachelus in Italy, large Lamniformes such as Carcharodon and Parotodus benedenii have also been found. It is possible that these sharks would have predated on the local species H. cortesii and H. pisanus.[2][3][5]
References
- ^ Bianucci, G.; Vaiani, S. C.; Casati, S. (2009). "A new delphinid record (Odontoceti, Cetacea) from the Early Pliocene of Tuscany (Central Italy): Systematics and biostratigraphic considerations". Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen. 254 (3): 275. doi:10.1127/0077-7749/2009/0018.
- ^ a b c d Global Biodiversity Information Facility article on Hemisyntrachelus, accessed 11/10/13
- ^ a b c d e f g Hemisyntrachelus at Fossilworks.org
- ^ " Galatius A, Racicot R, McGowen M ... Evolution and Diversification of Delphinid Skull Shapes iScience, 2020; 23 https://www.cell.com/action/showCitFormats?doi=10.1016%2Fj.isci.2020.101543&pii=S2589-0042%2820%2930735-5#:~:text=Galatius%20A%2C%20Racicot,Cancel
- ^ a b c Dominici, S.; Danise, S.; Benvenuti, M. (2018). "Pliocene Stratigraphic Paleobiology in Tuscany and the Fossil Record of Marine Megafauna". Earth-Science Reviews. 176: 23–24. Bibcode:2018ESRv..176..277D. doi:10.1016/j.earscirev.2017.09.018. hdl:2158/1139176.
- ^ Citron, Sara (2019). A reappraisal of Orcinus citoniensis, the earliest killer whale: osteoanatomy, phylogeny and palaeoecology (MSc). Università di Pisa.
- ^ Garassino, A.; Pasini, G.; de Angeli, A.; Charbonnier, S.; Famiani, F.; Baldanza, A.; Bizzari, R. (2012). "The decapod community from the Early Pliocene (Zanclean) of "La Serra" quarry (San Miniato, Pisa, Toscana, central Italy): sedimentology, systematics, and palaeoenvironmental implications" (PDF). Annales de Paléontologie. 98 (1): 1–62. Bibcode:2012AnPal..98....1G. doi:10.1016/j.annpal.2012.02.001. ISSN 0753-3969.
- ^ Collareta A, Casati S, Di Cencio A, Bianucci G. The Deep Past of the White Shark, Carcharodon carcharias, in the Mediterranean Sea: A Synthesis of Its Palaeobiology and Palaeoecology. Life (Basel). 2023 Oct 20;13(10):2085. doi: 10.3390/life13102085. PMID: 37895466; PMCID: PMC10608139.
Further reading
- G. Bianucci, S. Sorbi, M. E. Suarez and W. Landini. 2006. The southernmost sirenian record in the eastern Pacific Ocean, from the Late Miocene of Chile. Systematic Palaeontology 5:945-952