| Merriam's dog Temporal range: | |
|---|---|
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Carnivora |
| Family: | Canidae |
| Genus: | † Megacyon von Koenigswald, 1940 |
| Species: | †M. merriami |
| Binomial name | |
| †Megacyon merriami | |
Megacyon merriami, or Merriam's dog, was a prehistoric canid that lived on the island of Java in Indonesia during the Early Pleistocene. Its scientific name means "Merriam's large dog".
Megacyon was relatively larged sized, with an estimated body mass of around 49–54 kilograms (108–119 lb), comparable to a grey wolf. In comparison to its ancestor Xenocyon, the hypocone on the teeth was larger. [1]
Megacyon is thought to have been a hypercarnivore that preyed on large-sized prey such as deer. [1]
Megacyon is thought to have evolved from mainland species of Xenocyon, with Megacyon being even larger than mainland Xenocyon species. Some authors have subsumed Megacyon into Xenocyon. Megacyon is thought to be the ancestor of the much smaller Mececyon known from younger deposits on Java. [1] Megacyon are currently around the 49-54 kilogram size range due to their evolution and niche overlapping with tigers. As tigers and Megacyon had a 100% niche overlap, Megacyon evolved to be smaller in size in order to avoid this niche overlap for the species survival.
The dhole is a canid native to Central, South, East and Southeast Asia. It is genetically close to species within the genus Canis, but distinct in several anatomical aspects: its skull is convex rather than concave in profile, it lacks a third lower molar and the upper molars possess only a single cusp as opposed to between two and four. During the Pleistocene, the dhole ranged throughout Asia, Europe and North America but became restricted to its historical range 12,000–18,000 years ago.
The dire wolf is an extinct canine. The dire wolf lived in the Americas during the Late Pleistocene and Early Holocene epochs. The species was named in 1858, four years after the first specimen had been found. Two subspecies are recognized: Aenocyon dirus guildayi and Aenocyon dirus dirus. The largest collection of its fossils has been obtained from the Rancho La Brea Tar Pits in Los Angeles.
Stegodon is an extinct genus of proboscidean, related to elephants. It was originally assigned to the family Elephantidae along with modern elephants but is now placed in the extinct family Stegodontidae. Like elephants, Stegodon had teeth with plate-like lophs that are different from those of more primitive proboscideans like gomphotheres and mammutids. The oldest fossils of the genus are found in Late Miocene strata in Asia, likely originating from the more archaic Stegolophodon, subsequently migrating into Africa. While the genus became extinct in Africa during the Pliocene, Stegodon remained widespread in South, Southeast and East Asia until the end of the Pleistocene.
Dwarf elephants are prehistoric members of the order Proboscidea which, through the process of allopatric speciation on islands, evolved much smaller body sizes in comparison with their immediate ancestors. Dwarf elephants are an example of insular dwarfism, the phenomenon whereby large terrestrial vertebrates that colonize islands evolve dwarf forms, a phenomenon attributed to adaptation to resource-poor environments and lack of predation and competition.
Insular dwarfism, a form of phyletic dwarfism, is the process and condition of large animals evolving or having a reduced body size when their population's range is limited to a small environment, primarily islands. This natural process is distinct from the intentional creation of dwarf breeds, called dwarfing. This process has occurred many times throughout evolutionary history, with examples including dinosaurs, like Europasaurus and Magyarosaurus dacus, and modern animals such as elephants and their relatives. This process, and other "island genetics" artifacts, can occur not only on islands, but also in other situations where an ecosystem is isolated from external resources and breeding. This can include caves, desert oases, isolated valleys and isolated mountains. Insular dwarfism is one aspect of the more general "island effect" or "Foster's rule", which posits that when mainland animals colonize islands, small species tend to evolve larger bodies, and large species tend to evolve smaller bodies. This is itself one aspect of island syndrome, which describes the differences in morphology, ecology, physiology and behaviour of insular species compared to their continental counterparts.
The Sardinian dhole is an extinct insular canid which was endemic to what is now the Mediterranean islands of Sardinia and Corsica during the Middle-Late Pleistocene. It went extinct at the end of the Pleistocene around the time of human settlement of the islands.
Candiacervus is an extinct genus of deer native to Pleistocene Crete. Due to a lack of other herbivores, the genus underwent an adaptive radiation, filling niches occupied by other taxa on the mainland. Due to the small size of Crete, some species underwent insular dwarfism, the smallest species, C. ropalophorus, stood about 40 centimetres (16 in) at the shoulders when fully grown, while other species were relatively large and comparable in size to mainland deer species. Some species are noted for their peculiar, elongate club-shaped antlers, though other species have more normal antlers.
Palaeoloxodon namadicus is an extinct species of prehistoric elephant known from the early Middle to Late Pleistocene of the Indian subcontinent, and possibly also elsewhere in Asia. The species grew larger than any living elephant, and some authors have suggested it to have been the largest known land mammal based on extrapolation from fragmentary remains, though these estimates are speculative.
The Cyprus dwarf hippopotamus or Cypriot pygmy hippopotamus is an extinct species of hippopotamus that inhabited the island of Cyprus from the Pleistocene until the early Holocene. The 200-kilogram (440 lb) Cyprus dwarf hippo was roughly the same size as the extant pygmy hippopotamus. Unlike the modern pygmy hippo, the Cyprus dwarf became small through the process of insular dwarfism. H. minor is the smallest hippopotamus of all known insular hippopotamuses. It is estimated to have measured 76 cm (2.5 ft) tall and 121 cm (4.0 ft) long.
Hippopotamus pentlandi is an extinct species of hippopotamus from Sicily, known from the late Middle Pleistocene to early Late Pleistocene. It is the largest of the insular dwarf hippos known from the Pleistocene of the Mediterranean, "at most 20% smaller than the mainland forms", with an estimated body mass of approximately 1100 kg. It is suggested that it arrived in Sicily between 250,000 and 150,000 years ago, probably descending from the modern hippopotamus, with an origin from Hippopotamus antiquus being less likely. In comparison to those species, the muzzle was shorter, the occipital and nasal regions were more developed, the mastoid process was enlarged, and the dental row was shortened, and the condyle of the mandible is low. In comparison to H. amphibius, the orbits are also elevated. It was present in Sicily until at least the latest Middle Pleistocene around 120 kya, and was probably extinct by the beginning of Marine Isotope Stage 4. Contemporaneous species include the dwarf elephant Palaeoloxodon mnaidriensis, the aurochs, red deer, steppe bison, fallow deer, wild boar, brown bear, wolves, red foxes, cave hyena and cave lions. Its diet was likely grazing dominated, similar to that of modern H. amphibius. It is probably ancestral to Hippopotamus melitensis from Malta, which is substantially smaller than H. pentlandi.
Xenocyon is an extinct group of canids, either considered a distinct genus or a subgenus of Canis. The group includes Canis (Xenocyon) africanus, Canis (Xenocyon) antonii and Canis (Xenocyon) falconeri that gave rise to Canis (Xenocyon) lycanoides. The hypercarnivorous Xenocyon is thought to be closely related and possibly ancestral to modern dhole and the African wild dog, as well as the insular Sardinian dhole.
Hippopotamus creutzburgi, the Cretan dwarf hippopotamus, is an extinct species of hippopotamus from the island of Crete. It lived on the island from the Early Pleistocene to early Middle Pleistocene, and probably descended from Hippopotamus antiquus. It was considerably smaller than H. antiquus, weighing approximately 400 kilograms (880 lb). It was one of only two large herbivores on the island during its existence, alongside the dwarf mammoth Mammuthus creticus, with large predators being absent, the only other species of mammal present on the island being the giant rat Kritimys. It is known from abundant remains collected from the Katharo basin in the eastern uplands of Crete, approximately 1,100–1,200 metres (3,600–3,900 ft) above sea level, as well as much rarer remains found in coastal caves. Analysis of its limbs suggests that it was more adapted to terrestrial locomotion than living hippopotamus, primarily walking on its hooves rather than its footpads as in living hippopotamus, and capable of traversing the rugged terrain of Crete. Analysis of its teeth suggests that it had a grazing diet, similar to modern Hippopotamus amphibius. The previous suggestion that the species can be divided into two subspecies is not supported by modern research.
Protocyon is an extinct genus of large canid endemic to South and North America during the Late Pleistocene living from 781 to 12 thousand years ago.
Tapirus californicus, the California tapir, is an extinct species of tapir that inhabited North America during the Pleistocene. It became extinct about 13,000 years ago.
Tapirus merriami, commonly called Merriam's tapir, is an extinct species of tapir which inhabited North America during the Pleistocene.
Mammuthus creticus, or the Cretan dwarf mammoth, is an extinct species of dwarf mammoth endemic to Crete.
Hemimachairodus is an extinct genus of machairodontine (sabre-toothed) cat with only one species, Hemimachairodus zwierzyckii, known from fossils from the Pleistocene of Java.
Duboisia santeng or Dubois' antelope is an extinct antelope-like bovid that was endemic to Indonesia during the Pleistocene. It went extinct during the Ionian stage of the Pleistocene, about 750.000 years ago. Duboisia santeng was first described by the Dutch paleoanthropologist and geologist Eugène Dubois in 1891.
Mececyon trinilensis, the Trinil dog, is an extinct canid species that lived on the island of Java in Indonesia during the Pleistocene.
Cervus astylodon, the Ryukyu dwarf deer, is an extinct species of dwarf deer that was endemic to the Ryukyu Islands of Okinawa, Ishigaki, Kume and Tokunoshima. It lived throughout the Pleistocene, becoming extinct towards the end of the Late Pleistocene, following the arrival of humans to the Ryukyu Islands.
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