Stegoloxodon

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Stegoloxodon
Temporal range: Early Pleistocene
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Elephas celebensis.png
Tusk of Stegoloxodon celebensis from Sangihe, North Sulawesi, on display in the Bandung Geological Museum
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Proboscidea
Family: Elephantidae
Genus: Stegoloxodon
Kretzoi, 1950
Species
  • S. celebensis (Hooijer, 1949)
  • S. indonesicus Kretzoi, 1590

Stegoloxodon is an extinct genus of dwarf elephant known from the Early Pleistocene of Indonesia. It contains two species, S. indonesicus from Java, and S. celebensis from Sulawesi. Its relationship with other elephants is uncertain.

Contents

Taxonomy

S. celebensis was originally described as Archidiskodoncelebensis in 1949 by Dirk Albert Hooijer. [1] S. indonesicus was originally described by Miklós Kretzoi based on a molar found near Bumiayu, originally attributed to Elephas planifrons, who coined the genus Stegoloxodon to contain the species. [2] A 1973 paper argued for the synonymy of the two species, [3] which was later rejected, though they are usually considered closely related. [2] Some later papers referred the species to Elephas. [4] A paper by Paul Yves Sondaar in 1984 started a trend of referring to the two species to the genus "Elephas" with quotation remarks, reflecting uncertainty about their placement in the genus. A 2008 review by Markov and Saegusa resurrected the genus Stegoloxodon to house the two species. [2]

The relationship with other elephants has been considered uncertain, which has been suggested to be the result of dwarfism-caused changes to its morphology. [2] [5] Some authors have suggested a close relationship to Loxodonta (which is not known outside of Africa) or to Elephas planifrons (which is known from the Late Pliocene-Early Pleistocene of South Asia). [5]

Description

Both S. indonesicus and S. celebensis were dwarf elephants substantially smaller than mainland elephant species [5] as a result of insular dwarfism, [6] with S. celebensis estimated to have been around 150 cm (4.9 ft) tall. [7] The molar plates of both species are low-crowned with thick enamel, with the lamellae frequency being notably higher in S. celebensis than in S. indonesicus. [2] Both species retained permanent premolars. [5] Lower tusks are present in some adult individuals of S. celebensis, unlike modern elephants, which is either suggested to have been a retained ancestral trait lost in modern elephants, [8] or the result of paedomorphosis as a consequence of dwarfism, [3] with the mandibular symphysis of S. celebensis being downwardly turned. The skull of S. celebensis is short and tall, with fronto-parietal crests, and slightly curved upper tusks. [8]

Ecology

Isotope analysis suggests that S. celebensis was a flexible feeder, [9] while S. indonesicus is suggested to have been a dedicated browser on C3 vegetation in forested habitats. [10] S. celebensis inhabited the island alongside the similarly sized dwarf Stegodon species Stegodon sompoensis, and a larger unnamed Stegodon species [8] [11] while Stegoxolodon indonesicus co-existed alongside the gomphothere Sinomastodon bumiajuensis, and an unnamed dwarf species of Stegodon. [10]

Related Research Articles

<span class="mw-page-title-main">Proboscidea</span> Order of elephant-like mammals

Proboscidea is a taxonomic order of afrotherian mammals containing one living family (Elephantidae) and several extinct families. First described by J. Illiger in 1811, it encompasses the elephants and their close relatives. Proboscideans include some of the largest known land mammals. The largest land mammal of all time may have been a proboscidean; the elephant Palaeoloxodon namadicus has been estimated to be up to 5.2 m (17.1 ft) at the shoulder and may have weighed up to 22 t, surpassing the paraceratheres, the otherwise largest known land mammals, though this estimate was made based on a single fragmentary femur and is speculative. The largest extant proboscidean is the African bush elephant, with a record of size of 4 m (13.1 ft) at the shoulder and 10.4 t. In addition to their enormous size, later proboscideans are distinguished by tusks and long, muscular trunks, which were less developed or absent in early proboscideans.

<span class="mw-page-title-main">Sulawesi</span> One of the Greater Sunda Islands of Indonesia

Sulawesi, also known as Celebes, is an island in Indonesia. One of the four Greater Sunda Islands, and the world's 11th-largest island, it is situated east of Borneo, west of the Maluku Islands, and south of Mindanao and the Sulu Archipelago. Within Indonesia, only Sumatra, Borneo, and Papua are larger in territory, and only Java and Sumatra have larger populations.

<span class="mw-page-title-main">Elephantidae</span> Family of mammals

Elephantidae is a family of large, herbivorous proboscidean mammals collectively called elephants and mammoths. These are large terrestrial mammals with a snout modified into a trunk and teeth modified into tusks. Most genera and species in the family are extinct. Only two genera, Loxodonta and Elephas, are living.

<i>Elephas</i> Genus of mammals

Elephas is one of two surviving genera in the family of elephants, Elephantidae, with one surviving species, the Asian elephant, Elephas maximus. Several extinct species have been identified as belonging to the genus, extending back to the Pliocene era.

<i>Palaeoloxodon</i> Genus of extinct elephants

Palaeoloxodon is an extinct genus of elephant. The genus originated in Africa during the Early Pleistocene, and expanded into Eurasia at the beginning of the Middle Pleistocene. The genus contains some of the largest known species of elephants, over 4 metres (13 ft) tall at the shoulders, including the African Palaeoloxodon recki, the European straight-tusked elephant and the South Asian Palaeoloxodon namadicus. P. namadicus has been suggested to be the largest known land mammal by some authors based on extrapolation from fragmentary remains, though these estimates are highly speculative. In contrast, the genus also contains many species of dwarf elephants that evolved via insular dwarfism on islands in the Mediterranean, some only 1 metre (3.3 ft) in height, making them the smallest elephants known. The genus has a long and complex taxonomic history, and at various times, it has been considered to belong to Loxodonta or Elephas, but today is usually considered a valid and separate genus in its own right.

<i>Stegodon</i> Genus of extinct proboscidean

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.

<span class="mw-page-title-main">Dwarf elephant</span> Prehistoric elephant species

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.

<span class="mw-page-title-main">Insular dwarfism</span> Form of phyletic dwarfism occurring on islands

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.

<i>Palaeoloxodon falconeri</i> Extinct species of elephant

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 only 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.

<i>Sinomastodon</i> Extinct genus of gomphothere proboscidean

Sinomastodon is an extinct gomphothere genus known from the Late Miocene to Early Pleistocene of Asia, including China, Japan, Thailand, Myanmar, Indonesia and probably Kashmir.

<i>Palaeoloxodon namadicus</i> Extinct species of elephant

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.

<i>Elephas hysudricus</i> Extinct species of mammal

Elephas hysudricus is an extinct elephant species known from the Pleistocene of Asia. It is thought to be ancestral to the living Asian elephant, from which it is distinguished by the molar teeth having a lower crown height and a lower lamellae number. Remains of the species are primarily known from the Indian subcontinent, with the most important remains coming from the Siwalik Hills. The oldest remains of the species in the Siwaliks are placed at around 2.6 million year ago at the beginning of the Early Pleistocene, with the youngest dates in the Siwaliks during the Middle Pleistocene around 0.6 million years ago, though it likely persisted on the subcontinent later than this based on remains found elsewhere. Remains likely attributable to the species are also known from the Levant in Israel and Jordan, dating to the late Middle Pleistocene, likely sometime between 500-100,000 years ago. Isotopic analysis of specimens from the Indian subcontinent suggests that early members of the species were likely primarily grazers, but shifted towards mixed feeding after the arrival of the substantially larger elephant species Palaeoloxodon namadicus to the region. It is suggested to be closely related and possibly ancestral to the extinct Elephas hysudrindicus from the Pleistocene of Java in Indonesia.

<span class="mw-page-title-main">Stegodontidae</span> Family of extinct elephant-like mammals

Stegodontidae is an extinct family of proboscideans from Africa and Asia from the Early Miocene to the Late Pleistocene. It contains two genera, the earlier Stegolophodon, known from the Miocene of Asia and the later Stegodon, from the Late Miocene to Late Pleistocene of Africa and Asia which is thought to have evolved from the former. The group is noted for their plate-like lophs on their teeth, which are similar to elephants and different from those of other extinct proboscideans like gomphotheres and mammutids, with both groups having a proal jaw movement utilizing forward strokes of the lower jaw. These similarities with modern elephants were probably convergently evolved. Like elephantids, stegodontids are thought to have evolved from gomphothere ancestors.

<i>Palaeoloxodon naumanni</i> Extinct species of elephant

Palaeoloxodon naumanni, occasionally called Naumann's elephant, is an extinct species belonging to the genus Palaeoloxodon found in the Japanese archipelago during the Middle to Late Pleistocene around 330,000 to 24,000 years ago. It is named after Heinrich Edmund Naumann who discovered the first fossils at Yokosuka, Kanagawa, Japan. Fossils attributed to P. naumanni are also known from China and Korea, though the status of these specimens is unresolved, and some authors regard them as belonging to separate species.

<i>Elephas hysudrindicus</i> Extinct species of mammal

Elephas hysudrindicus, commonly known also as the Blora elephant in Indonesia, is a species of extinct elephant from the Pleistocene of Java. It is anatomically distinct from the Asian elephant, the last remaining species of elephant under the genus Elephas. The species existed from around the end of the Early Pleistocene until the end of the Middle Pleistocene, when it was replaced by the modern Asian elephant, coexisting alongside fellow proboscidean Stegodon trigonocephalus, as well archaic humans belonging to the species Homo erectus.

<i>Stegodon aurorae</i> Species of fossil elephantoid

Stegodon aurorae, also known as the Akebono elephant, is a species of fossil elephantoid known from Early Pleistocene Japan and Taiwan.

<i>Megalochelys</i> Extinct genus of tortoises

Megalochelys is an extinct genus of tortoises that lived from the Miocene to Pleistocene. They are noted for their giant size, which is among the largest of any known testudine, with a maximum carapace length over 2 m (6.5 ft) in M. atlas. During the dry glacial periods it ranged from western India and Pakistan to as far east as Sulawesi and Timor in Indonesia, though the island specimens likely represent distinct species.

<i>Elephas planifrons</i> Extinct species of mammal

Elephas planifrons is an extinct species of elephant, known from the Late Pliocene-Early Pleistocene of the Indian subcontinent.

Mata Menge is an early Middle Pleistocene paleoanthropological site located in the Ola Bula Formation in the So'a Basin on the island of Flores, Indonesia. Lithic artefacts and hominin remains have been discovered at the site. The level of sophistication of the Mata Menge lithic artefacts is described as being 'simple'.

Varanus hooijeri is an extinct species of medium-sized monitor lizard found in Liang Bua on Flores and possibly also Sumba, dating to the Late Pleistocene and Holocene.

References

  1. Hooijer, D.A .(1949). Pleistocene Vertebrates from Celebes. IV. - Archidiskodon celebensis nov spec. Zoologische Mededelingen, Museum Leiden 30: 205–226.
  2. 1 2 3 4 5 Markov, Georgi N.; Saegusa, Haruo (2008-09-01). "On the validity of Stegoloxodon Kretzoi, 1950 (Mammalia: Proboscidea)". Zootaxa. 1861 (1): 55. doi:10.11646/zootaxa.1861.1.5. ISSN   1175-5334.
  3. 1 2 Maglio, V.J. (1973). Origin and evolution of the Elephantidae. Transactions of the American Philosophical Society Philadelphia Volume 63. American Philosophical Society, Philadelphia. Pp. 149
  4. Hooijer, D.A. (1974). Elephas celebensis (Hooijer) from the Pleistocene of Java. Zoologische Mededelingen, Museum Leiden, 48: 85–93.
  5. 1 2 3 4 Sanders, William J. (2018-02-17). "Horizontal tooth displacement and premolar occurrence in elephants and other elephantiform proboscideans". Historical Biology. 30 (1–2): 137–156. doi:10.1080/08912963.2017.1297436. ISSN   0891-2963.
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  7. Alink, Gerrit; Adhityatama, Shinatria; Simanjuntak, Truman (2017-12-29). "The Descriptive Analysis of Palaeolithic Stone Tools from Sulawesi, Collected by the Indonesian-Dutch Expedition in 1970". AMERTA. 35 (2): 75. doi: 10.24832/amt.v35i2.252 .
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  9. Puspaningrum, Mika Rizki; Chivas, Allan R.; Kurniawan, Iwan; Wibowo, Unggul P.; Zaim, Yahdi; Van den Bergh, Gerrit D. (2021-12-28). "Isotopic reconstruction of Proboscidean habitats and diets on enigmatic island of Sulawesi". Berita Sedimentologi. 47 (3): 79–80. doi: 10.51835/bsed.2021.47.3.364 . ISSN   0853-9413.
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