| Orcinus paleorca | |
|---|---|
 | |
| O. paleorca holotype, front view (left) and side view (right). Dotted lines indicate inferred dimensions. | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Artiodactyla |
| Infraorder: | Cetacea |
| Family: | Delphinidae |
| Genus: | Orcinus |
| Species: | †O. paleorca |
| Binomial name | |
| †Orcinus paleorca Matsumoto, 1937 | |
Orcinus paleorca is a fossil species of Orcinus , the genus of killer whales (orca), dated to the Middle Pleistocene.
The holotype specimen, a tooth fragment, was found by G. Natsume in the Sanuki Formation in the Kazusa Province of Honshu, Japan–an area dating back to the Middle Pleistocene–and described in 1937 by Japanese paleontologist Hikoshichiro Matsumoto. Orcinus paleorca could represent the ancestor of the modern killer whale (Orcinus orca). Matsumoto noted that the teeth of O. paleorca are much larger and have more similar dimensions to the modern killer whale than those of the Pliocene O. citoniensis are. [2]
The tooth is conical and belonged to the upper right or lower left jaw of an adult individual. The tooth fragment is 5 cm (2.0 in) in height–though the actual height may have been double that–2.25 cm (0.89 in) longitudinally–from the side facing the tongue to the side facing the lip–and 2.95 cm (1.16 in) transversely–from the left side of the tooth to the right. [2] In comparison, the modern killer whale has teeth around 8 cm (3.1 in) in height and 2.5 cm (0.98 in) in diameter. [3] Like the modern killer whale, the tooth lacks a coat of cementum. However, unlike the modern killer whale, O. paleorca had a circular tooth root as opposed to an oval, and the pulp extended more towards the back than the front. [2]
Orcinus species, like many other predatory marine lineages, may have fished up the food chain, with the apparently more primitive O. citoniensis able to hunt large fish, and the modern killer whale's ability to hunt large whales. [4]
The Middle Pleistocene deposits indicate a warm temperate climate, and temperate forests of land. The marine mammal diversity comprises O. paleorca, an undetermined species of Orcinus, the baleen whale Mizuhoptera , an unidentified oceanic dolphin, the fossil false killer whale Pseudorca yokoyamai , the fossil walrus Odobenus mandanoensis , an undetermined species of Eumetopias sea lion, and the recently extinct Steller's sea cow (Hydrodamalis gigas). [5] [6] Sharks present were the great white shark (Carcharodon carcharias) and the extinct broad-toothed mako (Cosmopolitodus hastalis). [2] [7] [8]
The orca, or killer whale, is a toothed whale that is the largest member of the oceanic dolphin family. It is the only extant species in the genus Orcinus. Orcas are recognizable by their black-and-white patterned body. A cosmopolitan species, orcas are found in diverse marine environments, from Arctic to Antarctic regions to tropical seas.
Dugongidae is a family in the order of Sirenia. The family has one surviving species, the dugong, one recently extinct species, Steller's sea cow, and a number of extinct genera known from fossil records.
Steller's sea cow is an extinct sirenian described by Georg Wilhelm Steller in 1741. At that time, it was found only around the Commander Islands in the Bering Sea between Alaska and Russia; its range extended across the North Pacific during the Pleistocene epoch, and likely contracted to such an extreme degree due to the glacial cycle. It is possible indigenous populations interacted with the animal before Europeans. Steller first encountered it on Vitus Bering's Great Northern Expedition when the crew became shipwrecked on Bering Island. Much of what is known about its behavior comes from Steller's observations on the island, documented in his posthumous publication On the Beasts of the Sea. Within 27 years of its discovery by Europeans, the slow-moving and easily-caught mammal was hunted into extinction for its meat, fat, and hide.
Orcinus is a genus of Delphinidae, the family of carnivorous marine mammals known as dolphins. It includes the largest delphinid species, Orcinus orca, known as the orca or killer whale. Two extinct species are recognised, Orcinus paleorca and O. citoniensis, describing fossilised remains of the genus. The other extinct species O. meyeri is disputed.
Otodus megalodon, commonly known as megalodon, is an extinct species of giant mackerel shark that lived approximately 23 to 3.6 million years ago (Mya), from the Early Miocene to the Pliocene epochs. O. megalodon was formerly thought to be a member of the family Lamnidae and a close relative of the great white shark, but has been reclassified into the extinct family Otodontidae, which diverged from the great white shark during the Early Cretaceous.
Hydrodamalis is a genus of extinct herbivorous sirenian marine mammals, and included the Steller's sea cow, the Cuesta sea cow, and the Takikawa sea cow. The fossil genus Dusisiren is regarded as the sister taxon of Hydrodamalis: together, the two genera form the dugong subfamily Hydrodamalinae. They were the largest member of the order Sirenia, whose only extant members are the dugong and the manatees. They reached up to 9 metres (30 ft) in length, making the Steller's sea cow among the largest mammals other than whales to have existed in the Holocene epoch. Steller's sea cow was first described by Georg Wilhelm Steller,
Zygophyseter varolai is an extinct sperm whale that lived during the Tortonian age of the Late Miocene 11.2 to 7.6 million years ago. It is known from a single specimen from the Pietra Leccese Formation in Italy. It was a member of a stem group of fossil macroraptorial sperm whales also including Brygmophyseter, Acrophyseter, and Livyatan. It probably grew to be around 6.5 to 7 meters in length and shared some characteristics with other raptorials, such as large teeth with tooth enamel that were functional in both the upper and lower jaws which the modern sperm whale lacks. It also had a beak, the ability to echolocate prey, and could have probably swum faster than the modern-day sperm whale which can reach 4 kilometers per hour (2.5 mph). These were probably used in the capture of large prey, such as large fish, seals, and whales. In fact, its common name, the killer sperm whale, refers to its feeding habits that would have had a resemblance to the modern-day killer whale.
Livyatan is an extinct genus of macroraptorial sperm whale containing one known species: L. melvillei. The genus name was inspired by the biblical sea monster Leviathan, and the species name by Herman Melville, the author of the famous novel Moby-Dick about a white bull sperm whale. It is mainly known from the Pisco Formation of Peru during the Tortonian stage of the Miocene epoch, about 9.9–8.9 million years ago (mya); however, finds of isolated teeth from other locations such as Chile, Argentina, United States (California), South Africa and Australia imply that either it or a close relative survived into the Pliocene, around 5 mya, and may have had a global presence. It was a member of a group of macroraptorial sperm whales and was probably an apex predator, preying on whales, seals and so forth. Characteristically of raptorial sperm whales, Livyatan had functional, enamel-coated teeth on the upper and lower jaws, as well as several features suitable for hunting large prey.
Orcinus citoniensis is an extinct species of killer whale identified in the Late Pliocene of Italy and the Early Pleistocene of England. It was smaller than the modern killer whale, 4 m (13 ft) versus 7 to 10 m, and had around 8 more teeth in its jaw. It may have resembled the modern killer whale in appearance, and could represent a transitional species between the modern killer whale and other dolphins. O. citoniensis could have hunted fish and squid in pods, and coexisted with other large predators of the time such as the orcinine Hemisyntrachelus and the extinct shark Otodus megalodon.
Scaldicetus is an extinct genus of highly predatory macroraptorial sperm whale. Although widely used for a number of extinct physeterids with primitive dental morphology consisting of enameled teeth, Scaldicetus as generally recognized appears to be a wastebasket taxon filled with more-or-less unrelated primitive sperm whales.
Stegodon aurorae, also known as the Akebono elephant, is a species of fossil elephantoid known from Early Pleistocene Japan and Taiwan.
The Cuesta sea cow is an extinct herbivorous marine mammal and is the direct ancestor of the Steller's sea cow. They reached up to 9 metres (30 ft) in length, making them among the biggest sirenians to have ever lived. They were first described in 1978 by Daryl Domning when fossils in California were unearthed. Its appearance and behavior are largely based on that of the well-documented Steller's sea cow, which, unlike the Cuesta sea cow, lived into modern times and was well-described.
The Takikawa sea cow is an extinct herbivorous marine mammal of the Late Pliocene which was closely related to the recently extinct Steller's sea cow. In 1988, fossils of sea cows were discovered in Hokkaido and were originally assigned to the Takikawa sea cow, a newly described species, even though this taxon is thought of by some scientists as a synonym of the Cuesta sea cow. It is uncertain whether or not the Takikawa sea cow was simply a local variant of the Cuesta sea cow or a completely separate lineage. However, the Steller's sea cow and Takikawa sea cow share more morphological similarities than the Takikawa sea cow and Cuesta sea cow.
Orcinus meyeri is a fossil species of Orcinus found in the Early Miocene deposits of southern Germany, known from two jaw fragments and 18 isolated teeth. It was originally described as Delphinus acutidens in 1859, but reclassified in 1873. Its validity is disputed, and it may be a synonymous with the ancient sperm whale Physeterula dubusi. It was found in the Alpine town of Stockach in the Molasse basin, which was a coastal area with strong tidal currents.
Macroraptorial sperm whales were highly predatory whales of the sperm whale superfamily (Physeteroidea) of the Miocene epoch that hunted large marine mammals, including other whales, using their large teeth. They consist of five genera: Acrophyseter, Albicetus, Brygmophyseter, Livyatan, and Zygophyseter. All species are known by at least a skull, and are informally grouped without a family designation. They were all likely the apex predator of their habitats, comparable to the modern day killer whale, and achieved great lengths, with one species–Livyatan–measuring about 13.5–17.5 m (44–57 ft).
Pseudorca yokoyamai is an extinct species of oceanic dolphin from the Calabrian stage of the Pleistocene of Japan, an extinct relative of the modern day false killer whale.
Hoplocetus is an extinct genus of raptorial cetacean of the sperm whale superfamily, Physeteroidea. Its remains have been found in the Miocene of Belgium, France, Germany and Malta, the Pliocene of Belgium and France, and the Pleistocene of the United Kingdom and South Carolina.
Ankylorhiza is an extinct genus of toothed whale that lived in what is now the United States during the Oligocene epoch, between 29 and 23.5 million years ago. The type and only known species is A. tiedemani, though two fossil skeletons may represent an additional, second species within the genus. Ankylorhiza was about 4.8 meters (16 ft) long, with a long, robust skull bearing conical teeth that were angled forwards at the tip of the snout.
Orcas or killer whales have a cosmopolitan distribution and several distinct populations or types have been documented or suggested. Three to five types of orcas may be distinct enough to be considered different races, subspecies, or possibly even species. The IUCN reported in 2008, "The taxonomy of this genus is clearly in need of review, and it is likely that O. orca will be split into a number of different species or at least subspecies over the next few years." Although large variation in the ecological distinctiveness of different orca groups complicate simple differentiation into types. Mammal-eating orcas in different regions were long thought likely to be closely related, but genetic testing has refuted this hypothesis.
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