Janjucetus
Encyclopedia
Janjucetus is an extinct genus
of whale
, and a basal
form of the Mysticeti, a clade
which includes the extant baleen whales. The only known species, Janjucetus hunderi, lived during the late Oligocene
, about 25 million years ago in coastal seas off southeast Australia
. Unlike modern mysticetes, it possessed large teeth for gripping and shredding prey, and lacked baleen. Janjucetus was likely to have been a raptorial predator that captured large single prey animals rather than bulk-feeding on small organisms in the manner of living baleen whales.
Janjucetus is estimated to have been about 3.5 metres (11.5 ft) in length, about the size of the modern bottlenose dolphin
and much smaller than any living baleen whale. It is considered to be a mysticete due to key synapomorphies of the skull anatomy, for example in the way rostral bones meet the bones of the braincase. The relatively short snout tapers anteriorly from a broad base and is triangular in dorsal view. The incisors and canines form a terminal rosette of conical stabbing teeth while the premolars and molars are shaped like serrated blades. The orbits are exceptionally large. There is no evidence Janjucetus possessed the ability to echolocate
and probably relied on good eyesight to locate its prey.
Janjucetus is considered to be closely related to Mammalodon
, another genus of toothed mysticete from southeastern Australia. Janjucetus was initially assigned to its own monotypic
family, Janjucetidae, but a subsequent cladistic analysis by Fitzgerald (2010) transferred it to the Mammalodontidae, making Janjucetidae a jr synonym.
township of Jan Juc. The name Janjucetus hunderi, honours both the township and the discoverer. Hunder is said to have seen the brown fossils on a boulder while he surfed. Soon after discovering the site, Hunder and his father removed the boulder and transported it to Monash University
for further research. However, until Erich Fitzgerald started long-term research on the fossils in 2003, little had been established about the whale remains. Fitzgerald first published his findings in the journal, Proceedings of the Royal Society B
.
The well-preserved fossil remains include a nearly complete skull, mandibles, vertebrae, ribs, scapulae and a radius. They are held in the Museum Victoria Palaeontology Collection in Melbourne, Australia
. The holotype
of Janjucetus represents the most complete Paleogene
cetacean fossil from Australia.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of whale
Whale
Whale is the common name for various marine mammals of the order Cetacea. The term whale sometimes refers to all cetaceans, but more often it excludes dolphins and porpoises, which belong to suborder Odontoceti . This suborder also includes the sperm whale, killer whale, pilot whale, and beluga...
, and a basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
form of the Mysticeti, a clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
which includes the extant baleen whales. The only known species, Janjucetus hunderi, lived during the late Oligocene
Oligocene
The Oligocene is a geologic epoch of the Paleogene Period and extends from about 34 million to 23 million years before the present . As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly...
, about 25 million years ago in coastal seas off southeast Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
. Unlike modern mysticetes, it possessed large teeth for gripping and shredding prey, and lacked baleen. Janjucetus was likely to have been a raptorial predator that captured large single prey animals rather than bulk-feeding on small organisms in the manner of living baleen whales.
Description
Bottlenose Dolphin
Bottlenose dolphins, the genus Tursiops, are the most common and well-known members of the family Delphinidae, the family of oceanic dolphins. Recent molecular studies show the genus contains two species, the common bottlenose dolphin and the Indo-Pacific bottlenose dolphin , instead of one...
and much smaller than any living baleen whale. It is considered to be a mysticete due to key synapomorphies of the skull anatomy, for example in the way rostral bones meet the bones of the braincase. The relatively short snout tapers anteriorly from a broad base and is triangular in dorsal view. The incisors and canines form a terminal rosette of conical stabbing teeth while the premolars and molars are shaped like serrated blades. The orbits are exceptionally large. There is no evidence Janjucetus possessed the ability to echolocate
Animal echolocation
Echolocation, also called biosonar, is the biological sonar used by several kinds of animals.Echolocating animals emit calls out to the environment and listen to the echoes of those calls that return from various objects near them. They use these echoes to locate and identify the objects...
and probably relied on good eyesight to locate its prey.
Janjucetus is considered to be closely related to Mammalodon
Mammalodon
Mammalodon is an extinct genus of whale that was discovered in 1932. It is an early baleen whale which still had teeth, as opposed to baleen plates. It is one of two genera in the family Mammalodontidae....
, another genus of toothed mysticete from southeastern Australia. Janjucetus was initially assigned to its own monotypic
Monotypic
In biology, a monotypic taxon is a taxonomic group with only one biological type. The term's usage differs slightly between botany and zoology. The term monotypic has a separate use in conservation biology, monotypic habitat, regarding species habitat conversion eliminating biodiversity and...
family, Janjucetidae, but a subsequent cladistic analysis by Fitzgerald (2010) transferred it to the Mammalodontidae, making Janjucetidae a jr synonym.
History
The only known fossil of Janjucetus was found in the late 1990s by a teenaged surfer named Staumn Hunder, near the VictorianVictoria (Australia)
Victoria is the second most populous state in Australia. Geographically the smallest mainland state, Victoria is bordered by New South Wales, South Australia, and Tasmania on Boundary Islet to the north, west and south respectively....
township of Jan Juc. The name Janjucetus hunderi, honours both the township and the discoverer. Hunder is said to have seen the brown fossils on a boulder while he surfed. Soon after discovering the site, Hunder and his father removed the boulder and transported it to Monash University
Monash University
Monash University is a public university based in Melbourne, Victoria. It was founded in 1958 and is the second oldest university in the state. Monash is a member of Australia's Group of Eight and the ASAIHL....
for further research. However, until Erich Fitzgerald started long-term research on the fossils in 2003, little had been established about the whale remains. Fitzgerald first published his findings in the journal, Proceedings of the Royal Society B
Proceedings of the Royal Society
Proceedings of the Royal Society is the parent title of two scientific journals published by the Royal Society, whereas its initial journal, Philosophical Transactions, is now devoted to special thematic issues...
.
The well-preserved fossil remains include a nearly complete skull, mandibles, vertebrae, ribs, scapulae and a radius. They are held in the Museum Victoria Palaeontology Collection in Melbourne, Australia
Melbourne
Melbourne is the capital and most populous city in the state of Victoria, and the second most populous city in Australia. The Melbourne City Centre is the hub of the greater metropolitan area and the Census statistical division—of which "Melbourne" is the common name. As of June 2009, the greater...
. The holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
of Janjucetus represents the most complete Paleogene
Paleogene
The Paleogene is a geologic period and system that began 65.5 ± 0.3 and ended 23.03 ± 0.05 million years ago and comprises the first part of the Cenozoic Era...
cetacean fossil from Australia.