Cervus astylodon Temporal range: Pleistocene Early - Late | |
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Skeleton of C. astylodon | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Mammalia |
Order: | Artiodactyla |
Family: | Cervidae |
Subfamily: | Cervinae |
Genus: | Cervus |
Species: | †C. astylodon |
Binomial name | |
†Cervus astylodon (Matsumoto, 1926) | |
Synonyms | |
Muntiacus astylodon |
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. [1] It lived throughout the Pleistocene, becoming extinct towards the end of the Late Pleistocene, following the arrival of humans to the Ryukyu Islands. [1] [2]
It was described by Hikoshichiro Matsumoto in 1926 and originally classified as a species of muntjac. [3]
Recently discovered Early Pleistocene remains assigned to C. astylodon show it to be much larger than the Late Pleistocene forms, showing this species went through a gradual dwarfing process. [1] The ancestral C. astylodon may have arrived on the Ryukyu islands from northern China.
The Ryukyu dwarf deer was a very small species, standing only 50 cm (20 in) tall. [4] It exhibits morphological characteristics that are considered typical of insular dwarf cervids, such as small body size, shortened limbs, and hypsodont molars. The antlers were generally very small, flattened and strongly grooved, with brow-tines that branch off from the very base of the antlers. [5]
The Ryukyu dwarf deer shows four distinct morphotypes based on each of the four islands it inhabits. [5] In Kume, the metacarpal bones are more slender than other forms, while those from Ishigaki have a thicker, stouter shaft. The deer from Okinawa and Tokunoshima are intermediate in metacarpal thickness; both those forms show differences with each other in the shape of the proximal metacarpal canal. [1]
The Ryukyu dwarf deer was originally thought to be a browser. Using mesowear analysis, its teeth were shown to have sharp cusps with high profiles, which implied a significant amount of browse in diets; deer with a more abrasive diet tend to have more rounded lower-profile cusps. [6]
However, a 2021 study using dental microwear texture analysis indicated that the Ryukyu dwarf deer was a mixed-feeder or grazer instead. Deer with a higher consumption of graminoids show rougher tooth surfaces than those browsing on trees owing to the high content of abrasive silica in graminoid leaves. A comparison of C. astylodon from two different sites (Hananda-Gama Cave site and the Yamashita-cho Cave I site) show a different amount of wear, indicating a variable diet. [7]
The islands on which Cervus atylodon lived exhibited a depauperate fauna, with the only other large mammal being present on the islands being another indeterminate similarly sized deer belonging to the subfamily Muntiacinae, with large carnivores being absent. [8] Dental wear analysis suggests that the species had a long lifespan, up to 18-25 years, with low levels of juvenile and adolescent mortality. [9]
The Ryukyu dwarf deer went extinct towards the end of the Pleistocene. [6] The timing of extinction for the species has been suggested to be 32,000–24,000 years Before Present. [6] Humans are first believed to have arrived on Okinawa around 30-35,000 years ago. [10] Human hunting may have been a factor in its extinction, [11] possibly in combination with environmental degradation due to the onset of the Last Glacial Maximum, thought the severity of environmental effects of the LGM on the Ryukyu Islands has been questioned. [6]
Candiacervus - dwarf deer from Crete
Praemegaceros cazioti - dwarf deer from Sardinia
Palawan is the largest island of the province of Palawan in the Philippines and fifth-largest by area and tenth-most populous island of the country, with a total population of 994,101 as of 2020 census. The northwest coast of the island is along the Palawan Passage in the eastern South China Sea, while the southeast coast forms part of the northern limit of the Sulu Sea. Much of the island remains traditional and is considered by some as under-developed. Abundant wildlife, jungle mountains, and some white sandy beaches attract many tourists, as well as international companies looking for development opportunities.
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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 various species of dwarf elephants that evolved during the Pleistocene epoch, as well as more ancient examples, such as the dinosaurs Europasaurus and Magyarosaurus. 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.
Palaeoloxodon falconeri is an extinct species of dwarf elephant from the Middle Pleistocene of Sicily and Malta. It is amongst the smallest of all dwarf elephants at under 1 metre (3.3 ft) in height. A member of the genus Palaeoloxodon, it derived from a population of the mainland European straight-tusked elephant.
Eucladoceros is an extinct genus of large deer whose fossils have been discovered across Eurasia, from Europe to China, spanning from the Late Pliocene-Early Pleistocene. It is noted for its unusual comb-like or branching antlers.
Cervus is a genus of deer that primarily are native to Eurasia, although one species occurs in northern Africa and another in North America. In addition to the species presently placed in this genus, it has included a whole range of other species now commonly placed in other genera. Additionally, the species-level taxonomy is in a state of flux.
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.
The Calamian deer, also known as Calamian hog deer, is an endangered species of deer found only in the Calamian Islands of Palawan province in the Philippines. It is one of three species of deer native to the Philippines, the other being the Philippine sambar and the Visayan spotted deer.
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.
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Hypnomys, otherwise known as Balearic giant dormice, is an extinct genus of dormouse (Gliridae) in the subfamily Leithiinae. Its species are considered examples of insular gigantism. They were endemic to the Balearic Islands in the western Mediterranean from the Early Pliocene until their extinction around 4,000 years ago. They first appeared in the fossil record on Mallorca during the Early Pliocene, presumably due to the Messinian salinity crisis causing a connection with mainland Europe. They later spread to Menorca, and a possible molar is also known from Ibiza. Hypnomys became extinct during the Holocene after human arrival on the Balearics. They were one of only three native land mammals to the islands at the time of human arrival, alongside the shrew Nesiotites and goat-antelope Myotragus.
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