Janjucetus
| Janjucetus | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Skull of Janjucetus hunderi at an exhibition in Melbourne |
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| Temporal occurrence | ||||||||||||
| Chattian (Oligocene) | ||||||||||||
| 28.1 to 23.03 million years | ||||||||||||
| Locations | ||||||||||||
| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Janjucetus | ||||||||||||
| Fitzgerald , 2006 | ||||||||||||
Janjucetus is a fossil genus of the baleen whales (Mysticeti). The so far only remains of the only species, Janjucetus hunderi , were discovered in approximately 25 million year old sedimentary rocks of the Upper Oligocene of Australia .
In contrast to other baleen whales, Janjucetus had teeth that were suitable for grasping and crushing prey, but only small or no whales. As an active predator, Janjucetus ate fish , possibly including small sharks and other comparatively large prey.
description
Janjucetus was small compared to other baleen whales - its body length is estimated at 3.5 m and thus roughly corresponds to that of the bottlenose dolphin . Apart from the pointed serrated teeth over 3 cm long, the morphology of the skull is similar to that of other baleen whales. Due to the apparently very large eyes, Janjucetus may have had extraordinary visual abilities; for echolocation , however, he was not capable. Janjucetus had a short, wide snout, with the teeth of the upper jaw overlapping the lower jaw ( prognathy ). The relatively large, robust jaws are likely to have been well suited for catching and killing the prey.
It is believed that Janjucetus was a close relative of various fossil baleen whales, including Mammalodon with whom he forms the family Mammalodontidae ( Syn .: Janjucetidae). However, some of its characteristics are unique within the Mysticeti group.
History of discovery and exploration
The only known fossils of Janjucetus were found in the late 1990s by a surfer named Staumn Hunder near the town of Jan Juc on the coast of the Australian state of Victoria . In 2003, Erich Fitzgerald began to research the finds, who described them in 2006 and assigned them to a new genus and species, which he named after the location or the finder.
The well-preserved skeletal remains of the holotype represent the most complete fossil record of a whale from the Old Tertiary (Paleogene) of Australia to date . They include the almost complete skull, lower jaw, teeth, vertebrae , ribs , shoulder blades and a forearm bone. The fossils are currently kept in the Paleontological Collection of the Museum of Victoria in Melbourne .
Paleobiology
Janjucetus ate much larger prey than its baleen whale relatives and it is assumed that it ate similar to the recent leopard seal or sea reptiles of the Mesozoic Era ( pliosaurs , mosasaurs ), which hunted down their prey in a quick attack. Since Janjucetus lacks some of the skull features of the whales capable of echolocation, he may not have been able to send out appropriate ultrasound signals . It is also unknown whether he was able to receive such signals.
literature
- Erich MG Fitzgerald: A bizarre new toothed mysticete (Cetacea) from Australia and the early evolution of baleen whales. In: Proceedings of the Royal Society . B 273, December 2006, ISSN 0962-8452 , pp. 2955-2963, doi : 10.1098 / rspb.2006.3664 .
- Erich MG Fitzgerald: The morphology and systematics of Mammalodon colliveri (Cetacea: Mysticeti), a toothed mysticete from the Oligocene of Australia. In: Zoological Journal of the Linnean Society. 158, No. 2, 2010, pp. 367-476. doi : 10.1111 / j.1096-3642.2009.00572.x .
