| Janjucetus Temporal range: Late Oligocene | |
|---|---|
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| Paleoart of Janjucetus hunderi by Carl Buell | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Tetrapoda |
| Clade: | Synapsida |
| Class: | Mammalia |
| Order: | Artiodactyla |
| Infraorder: | Cetacea |
| Family: | †Mammalodontidae |
| Genus: | †Janjucetus Fitzgerald, 2006 |
| Species | |
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Janjucetus (meaning "Jan Juc whale", derived from the Latin word for whale, or cetus) is an extinct genus of toothed baleen whale (Mysticeti). Being a member of the basal mysticete family, Mammlodontidae, it retained teeth and was a predator, unlike its closest living relatives. It lived during the Chattian stage of the late Oligocene epoch. Two species have been described. The first, Janjucetus hunderi, is known from the most complete paleogene whale fossil in Australia.[1] The other one, J. dullardi, was described from a partial skull. Both were discovered in the Jan Juc Formation of Victoria, Australia.[2]
History of research[]
J. hunderi[]
Bird Rock, part of the Jan Juc Formation. Credit: Australian Photography
In the late 1990s, teenage surfer Staumn Hunder came across a remarkably complete whale fossil at Deadmans Gully in Victoria, near the town of Jan Juc. The stratigraphy in which is was preserved was in the Jan Juc Marl of the Jan Juc Formation, radiometrically dating the the Chattian stage of the Oligocene epoch, about 26.05 to 24.2 million BC. With the help of Staumn's father, the material was extracted and brought to Monash Univerity. Catalogued under NMV P216929, it contained a nearly complete skull and mandible, vertebrae, rib bones, scapulae and a radius. Erich Fitzgerald described a new genus and species in 2006, Janjucetus hunderi, with the specimen as the holotype. The specific epithet honors Staumn Hunder for his contribution.[3]
J. dullardi[]
Known material of J. dullardi, specimen PMV P256471.
Ross Dullard was southwest of Bird Rock, at Half Moon Bay near Jan Juc, when he discovered a partial fossil skull in June of 2019. Later, he donated it to Museums Victoria, where it was catalogued as NMV P256471. This partial skull includes the squamosals, exoccipital, ear ossicles, seven teeth, and a few other pieces. In 2025, it became the holotype of Janjucetus dullardi, a new species described by Ruairidh Duncan and colleagues. As in the other species, the specific epithet references the animal's discoverer.[4][2]
Paleobiology[]
Mammalodonts like Janjucetus were convergent with toothed whales like Odobenocetops and Mesozoic ichthyosaurs, possessing enlarged eye orbits for hunting. The skulls of these animals to not exhibit the unambiguous features associated with the hypertropied melon organ (allowing for echolocation) in Late Cenozoic odontocetes. No evidence shows that the mysticete whale lineage ever possessed echolocation.[3]
Description[]
Holotype skull of J. hunderi in the collection of Museums Victoria as PMVP 216929.
The pattern of tooth wear in J. hunderi suggests that the teeth interlocked when the mouth was closed. Unlike modern mysticetes, whom all possess baleen, extinct basal kinds had teeth.
The holotype skull of J. dullardi likely belonged to a subadult or juvenile individual. This is indicated by absence of fusion in certain skull elements. By using a correlation between occipital condyle breadth and bizygomatic width, a body length of 1.75 to 2.05 m (5.7 - 6.5 ft) was estimated for the immature animal. This makes it the smallest known mammalodont.
Affinities[]
Fitzgerald's 2006 phylogeny of mysticetes, including J. hunderi.
Erich Fitzgerald in 2006 placed Janjucetus in a now invalid family "Janjucetidae". After another cladistic analysis in 2010, the genus was found to share features that warranted placement in Mammalodontidae with another genus, Mammalodon.[5] Eight unique mandibular characters for the family were later identified. Phylogetic analysis recovered J. dullardi as a sister taxon to the former species.
Analysis and comparisons of the two Janjucetus holotypes indicates that features previously believed to be unique in the genus were due to paedomorphosis (juvenile traits are evolutionarily retained in the adult form).[2]
Paleoecology[]
Ruairidh Duncan's reconstruction of a Janjucetus dullardi pair.
In the Chattian stage of the Oligocene epoch, the ecosystem preserved tn the Jan Juc Formation contained at least three mammalodont whale species. Aside from the two Janjucetus species, there was the larger Mammalodon colliveri.[2] Fish, such as the shark Carcharias elegans and pineapplefish Cleidopus carvernosus, were diverse here.[6]
Trivia[]
- In 2021, Janjucetus hunderi was one of eight nominees to be the state fossil emblem of Victoria. Koolasuchus cleetoni won the vote and recieved the title.[7]
Sources[]
- ↑ Noorden, Richard Van (16 August 2006). "Ancient Whale 'Truly Weird'". Nature News. doi:10.1038/news060814-6. S2CID 211730536.
- ↑ 2.0 2.1 2.2 2.3 Ruairidh J Duncan, James P Rule, Travis Park, Alistair R Evans, Justin W Adams, Erich M G Fitzgerald, An immature toothed mysticete from the Oligocene of Australia and insights into mammalodontid (Cetacea: Mysticeti) morphology, systematics, and ontogeny, Zoological Journal of the Linnean Society, Volume 204, Issue 4, August 2025, zlaf090, https://doi.org/10.1093/zoolinnean/zlaf090
- ↑ 3.0 3.1 Fitzgerald, Erich M. G. (2006). "A bizarre new toothed mysticete (Cetacea) from Australia and the early evolution of baleen whales". Proceedings of the Royal Society B. 273 (1604): 2955–2963. doi:10.1098/rspb.2006.3664. PMC 1639514. PMID 17015308.
- ↑ https://www.earth.com/news/ancient-whale-with-razor-sharp-teeth-discovered-in-australia/
- ↑ Fitzgerald, E. M. G. (2010). "The morphology and systematics of Mammalodon colliveri (Cetacea: Mysticeti), a toothed mysticete from the Oligocene of Australia". Zoological Journal of the Linnean Society. 158 (2): 367–476. doi:10.1111/j.1096-3642.2009.00572.x.
- ↑ Fitzgerald, E.M.G., 2004. A review of the Tertiary fossil Cetacea (Mammalia) localities in Australia. Memoirs of Museum Victoria 61: 183-208. http://doi.org/10.24199/j.mmv.2004.61.12
- ↑ Museums Victoria. (n.d.). Janjucetus hunderi. Melbourne Museum. Retrieved from https://museumsvictoria.com.au/melbournemuseum/state-fossil-emblem/janjucetus-hunderi/