Coronodon(meaning "crown tooth" ) is a genus of toothed (transitional)baleen whalesfrom the EarlyOligoceneAshleyandChandler Bridgeformations ofSouth Carolina.The genus contains three species: thetype speciesC. havensteini,and additional speciesC. newtonorumandC. planifrons.
| Coronodon | |
|---|---|
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| Coronodon anterolateral atMace Brown Museum of Natural History | |
Scientific classification
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Artiodactyla |
| Infraorder: | Cetacea |
| Parvorder: | Mysticeti |
| Genus: | †Coronodon Geisleret al.,2017 |
| Type species | |
| Coronodon havensteini Geisleret al.,2017
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| Other species | |
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Description
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It was about the same size asDorudon,measuring 4.9 m (16 ft) long and weighing 1,150 kg (2,540 lb). The rostrum ofCoronodonis wide, judging by its straight sides and short mandibular symphysis. Despite being similar to some archaeocetes in having a rostrum that is twisted counterclockwise in anterior view, it differs in having posterior teeth with subequal cusps and an upturned anterior process of the maxilla.Coronodondiffers from other toothed mysticetes in having anterior lower molars labially overlapping posterior lower molars.[1][2]
Classification
editCoronodonfalls basally within Mysticeti, being closely related to the unnamed taxon ChM PV 5720 and more primitive than"Metasqualodon"symmetricus,Aetiocetidae,MammalodontidaeandLlanocetus.[1][2]
Paleoecology
editCoronodonis very unusual among archaic toothed mysticetes due to its dentition. The incisors are caniniform, and the wear patterns on both the incisors and the P2 (second premolar on the right side of the mandible) indicate that this whale was well suited to capturing larger prey items and piercing flesh. This sort of dentition is common inbasilosauridwhales, who fed utilizing exclusivelypursuit predation.However,Coronodondiffers from its ancestors in that the molars possess more cusps and are more tightly packed together. The molars also have reduced support from thealveolarbone, and the apices of the three main cusps on the molars and premolars meet one another at a 155° angle in the upper and lower jaws, opposed to an 82° and a 98° angle inCynthiacetusandDorudonrespectively.[1]This would have diminished the shearing capabilities of the molars. The lack of oral processing occurring in the molar region is further evident by wear patterns on the labial side of the teeth, but little to no wear close to the cutting surfaces.[1]This is unlike the molar teeth of basilosaurids, which possess wear patterns indicative of shearing flesh at the back of the mouth.
In its initial description,Coronodonwas implied to have used its unusual postcanine teeth to facilitate dental filtration. Apart from the unusual shape and orientation of the teeth, evidence of dental filtration can be found in its skull. The rostrum inCoronodonis much wider than those ofarchaeocetesand primitiveodontocetes,and the mandibular symphysis is shorter. Additionally, the rostrum has very loose sutures, which would have allowedCoronodonto expand the size of its oral cavity in a manner similar to extant mysticetes.[1]
Together, these features suggest thatCoronodonemployed a mixed feeding strategy, swapping from pursuit predation toram feedingwhen necessary, and using its enlarged molar teeth as a sieve to capture prey whenfilter feeding.
Paleoenvironment
editC. havensteiniis found in the Ashley Formation, whereasC. planifronsandC. newtonorumare found in the Chandler Bridge Formation. The genus has a fossil range from 30 to 23.5 million years ago, from the Early to Late Oligocene. These formations would have been underwater at this time, and a wide assemblage of marine vertebrates have been discovered there. Many primitive odontocetes, such asAnkylorhiza,Xenorophus,andAlbertocetushave been found in both formations in Oligocene aged deposits. Other fossil organisms that have been found in these formations include varioussea turtles,sirenians,primitive mysticetes, the giant birdPelagornisand bony and cartilaginous fishes of many sorts, including the megatoothed shark genusOtodus.
References
edit- ^abcdeGeisler, Jonathan H; Boessenecker, Robert W; Brown, Mace; Beatty, Brian L (2017)."The Origin of Filter Feeding in Whales".Current Biology.27(13): 2036–2042.e2.doi:10.1016/j.cub.2017.06.003.PMID28669761.
- ^abBoessenecker, R. W.; Beatty, B. L.; Geisler, J. H. (2023)."New specimens and species of the Oligocene toothed baleen whale Coronodon from South Carolina and the origin of Neoceti".PeerJ.11:e14795.doi:10.7717/peerj.14795.
External links
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