Pygmy mammoth

Pygmy mammoth; Temporal range: Late Pleistocene 0.08–0.013 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
	Skeleton at the Santa Barbara Museum of Natural History
	Model of a pygmy mammoth (front) at the Cleveland Museum of Natural History
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Proboscidea
Family:	Elephantidae
Genus:	† Mammuthus
Species:	†M. exilis
Binomial name
	†Mammuthus exilis; (Stock & Furlong, 1928)

Last updated August 22, 2024

The pygmy mammoth or Channel Islands mammoth (Mammuthus exilis) is an extinct species of dwarf mammoth native to the northern Channel Islands off the coast of southern California during the Late Pleistocene. It was descended from the Columbian mammoth (M. columbi) of mainland North America, which are suggested to have colonised the islands around 250–150,000 years ago. At only 1.72–2.02 m (5.6–6.6 ft) tall at the shoulder, it was around 17% the size of its mainland ancestor. The species became extinct around 13,000 years ago, co-inciding with major environmental change and the arrival of humans in the Channel islands.

Discovery

Mammoth remains have been known on the northern Channel Islands of California since 1856. They were first reported in scientific literature in 1873.^[2]

In 1994 the National Park Service called in scientists to inspect an uncovered, unidentified skeleton found on the northeast coast of Santa Rosa Island.^[3] They found bones of the axial skeleton of a large land vertebrate and decided to excavate and dig up the skeleton. They recovered 90% of a mature male pygmy mammoth's skeleton.^[4] The mammoth was about 50 years old when it died.^[3] The small bones were preserved in life position, which represented that it had died where it was found rather than being scattered around the island. The bones were returned to the Santa Barbara Museum of Natural History.^[4] After the discovery of the skeleton, a pedestrian survey of the island began. This resulted in the discovery of 160 new locations of mammoth remains, the vast majority being found on Santa Rosa Island.^[3] This was the first discovery of a nearly complete specimen of the pygmy mammoth. Fortunately, the skeleton was only missing a foot, a tusk, and a couple of vertebrae. The remains were covered by a sand dune, which prevented the bones from scattering and kept them intact.^[5]

Distribution

Remains of M. exilis have been discovered on three of the northern Channel Islands of California: Santa Cruz, Santa Rosa, and San Miguel, which together with Anacapa were the highest portions of the now mostly submerged superisland of Santa Rosae which existed during times of lowered sea level.^[6] The area of the combined island has been estimated at 2,200 square kilometres (850 sq mi),^[7] though the area of the island fluctuated as a result of glacial cycles.^[6]

Evolution

The oldest fossil of mammoths on the Channel Islands is a tusk found on a marine terrace on Santa Rosa Island, which has been dated based on surrounding corals as 83,800 ± 600 – 78,600 ± 500 years old. It is suggested that their Columbian mammoth ancestors colonised the islands either around 250,000 or 150,000 years ago, when sea levels were considerably lower than they are today.^[6] During these times, the distance to the mainland was reduced to a minimum of 7 kilometres (4.3 mi),^[8] though there was never a land bridge as has often historically been suggested. Mammoths like living elephants, were probably good swimmers and able to swim this distance.^[6] The reduction in body size was the result of insular dwarfism as a result of the smaller land area of the Channel Islands relative to the mainland, which is observed in other island animal species, such as dwarf elephants known from islands in the Mediterranean.^[9]

Description

M. exilis was on average, 1.72–2.02 m (5.6–6.6 ft) tall at the shoulders and 760–1,350 kg (1,680–2,980 lb) in weight,^[10]^[11] making it around 17% of the body size of its 3.72–4.2 m (12.2–13.8 ft) tall, 9.2–12.5 t (9.1–12.3 long tons; 10.1–13.8 short tons) ancestor.^[11]^[7] Like other mammoths, the species exhibited sexual dimorphism, with males being larger than females.^[12] The limb bones of the species show isometric growth (preserving length-width ratio) from juveniles to adults, similar to those of living African elephants.^[13] In comparison to Columbian mammoths, the femur has a rounded rather than elliptical cross-section, and lacks a lateral tuberosity. The tusks are relatively straight and are around 50% the length and diameter of those of Columbian mammoths.^[12]

Habitat and ecology

During the Last Glacial Period, the mega-island of Santa Rosae is thought to have been forested with coniferous trees of cypress, douglas fir and pine. Dental microwear analysis suggests that species had a primarily browsing based diet on leaves and twigs, as opposed to the more grazing focused diet of its Columbian mammoth ancestors.^[9] In comparison to its larger ancestor, it likely had the ability to ascend somewhat steeper slopes.^[12] The island exhibited a depauperate fauna that lacked large predators.^[8] The Channel Islands fox was not present on the islands during the time of the pygmy mammoth, having only arrived on the islands around 7,300 years ago.^[14]

Extinction

The youngest records of the species date to around 13,000 years ago. This time coincides with the reduction of the area of Santa Rosae as a result of rising sea level, the arrival of humans in the Channel Islands (as evidenced by Arlington Springs Man) and climatic change resulting in the decline of the previously dominant conifer forest ecosystems and expansion of scrub and grassland, possibly induced by wildfires. It is therefore difficult to disentangle the precise causes of its extinction,^[9]^[15] though the pygmy mammoths had likely survived a greater reduction in island area during the preceding Last Interglacial/Sangamonian.^[6]

Related Research Articles

A mammoth is any species of the extinct elephantid genus Mammuthus. They lived from the late Miocene epoch into the Holocene about 4,000 years ago, and various species existed in Africa, Europe, Asia, and North America. Mammoths are distinguished from living elephants by their spirally twisted tusks and in at least some later species, the development of numerous adaptions to living in cold environments, including a thick layer of fur.

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. Three species of elephant are currently recognised: the African bush elephant, the African forest elephant, and the Asian elephant.

A mastodon is a member of the genus Mammut, which, strictly defined, was endemic to North America and lived from the late Miocene to the early Holocene. Mastodons belong to the order Proboscidea, the same order as elephants and mammoths. Mammut is the type genus of the extinct family Mammutidae, which diverged from the ancestors of modern elephants at least 27–25 million years ago, during the Oligocene.

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.

Channel Islands National Park consists of five of the eight Channel Islands off the Pacific coast of the U.S. state of California. Although the islands are close to the shore of the densely populated state, they have been relatively undeveloped. The park covers 249,561 acres (100,994 ha), of which 79,019 acres (31,978 ha) are federal land.

Santa Rosae was, before the end of the last ice age, an ancient landmass off the coast of present-day southern California, near Santa Barbara County and Ventura County, of which the northern Channel Islands of California are remnants. At its largest, Santa Rosae was roughly 3-4 times bigger than the northern Channel Islands of today, nearly 125 km long from east to west. Between about 20,000 and 5,000 years ago, Santa Rosae lost about 70% of its land mass to post-glacial rising sea level, leaving behind a vast submerged landscape currently being explored by scientists. San Miguel, Santa Rosa, Santa Cruz, and Anacapa Island comprise the unsubmerged portions of Santa Rosae today. This island was about 5 miles offshore. It broke up between about 11,000 and 9,000 years ago, and the present northern Channel Islands took their shape after the continental ice sheets melted and sea levels rose by about 100 meters.

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 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.

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. Fossils of the genus are known from Africa and across much of Asia, as far southeast as Timor. 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 persisted in South, Southeast and Eastern Asia into the Late 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.

The Columbian mammoth is an extinct species of mammoth that inhabited North America from southern Canada to Costa Rica during the Pleistocene epoch. The Columbian mammoth descended from Eurasian steppe mammoths that colonised North America during the Early Pleistocene around 1.5–1.3 million years ago, and later experienced hybridisation with the woolly mammoth lineage. The Columbian mammoth was among the last mammoth species, and the pygmy mammoths evolved from them on the Channel Islands of California. The closest extant relative of the Columbian and other mammoths is the Asian elephant.

The straight-tusked elephant is an extinct species of elephant that inhabited Europe and Western Asia during the Middle and Late Pleistocene. One of the largest known elephant species, mature fully grown bulls on average had a shoulder height of 4 metres (13 ft) and a weight of 13 tonnes (29,000 lb). Straight-tusked elephants likely lived very similarly to modern elephants, with herds of adult females and juveniles and solitary adult males. The species was primarily associated with temperate and Mediterranean woodland and forest habitats, flourishing during interglacial periods, when its range would extend across Europe as far north as Great Britain and eastwards into Russia. Skeletons found in association with stone tools and wooden spears suggest they were scavenged and hunted by early humans, including Neanderthals. It is the ancestor of most dwarf elephants that inhabited islands in the Mediterranean.

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Mammuthus trogontherii, sometimes called the steppe mammoth, is an extinct species of mammoth that ranged over most of northern Eurasia during the Early and Middle Pleistocene, approximately 1.7 million to 200,000 years ago. One of the largest mammoth species, it evolved in East Asia during the Early Pleistocene, around 1.8 million years ago, before migrating into North America around 1.5 million years ago, and into Europe during the Early/Middle Pleistocene transition, around 1 to 0.7 million years ago. It was the ancestor of the woolly mammoth and Columbian mammoth of the later Pleistocene.

Mammuthus lamarmorai is a species of dwarf mammoth which lived during the late Middle and Late Pleistocene on the island of Sardinia in the Mediterranean. It has been estimated to have had a shoulder height of around 1.4 metres (4.6 ft). Remains have been found across the western part of the island.

<span class="mw-page-title-main">Cypriot pygmy hippopotamus</span> Species of mammal (fossil)

The Cypriot pygmy hippopotamus is an extinct species of dwarf hippopotamus that inhabited the island of Cyprus from the Pleistocene until the early Holocene.

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<i>Mammuthus creticus</i> Extinct species of mammal

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References

↑ Chester Stock and E. L. Furlong (1928). "The Pleistocene elephants of Santa Rosa Island, California" (PDF). Science. 68 (1754): 140–141. Bibcode:1928Sci....68..140S. doi:10.1126/science.68.1754.140. PMID 17772244.
↑ Agenbroad, L.D. (2003). "New absolute dates and comparisons for California's Mammuthus exilis". Deinsea. 9: 1–16.
1 2 3 Agenbroad, L.D.; Johnson J.; Morris D.; Stafford T.W. "Mammoths and Humans as Late Pleistocene Contemporaries on Santa Rosa Island" (PDF). Proceedings of the American Geophysical Union. Spring Meeting 2007.
1 2 Agenbroad, Larry D.; Don P. Morris. "Giant Island/Pygmy Mammoths:The Late Pleistocene Prehistory of Channel Islands National Park" (PDF). National Park Service Paleontological Research. 4: 35–39. Archived from the original (PDF) on 2014-02-19. Retrieved 2013-10-23.
↑ anonymous, anonymous. "Stranded on Santa Monica". Discover. 16: 1. ProQuest 206020333.
1 2 3 4 5 Muhs, Daniel R.; Simmons, Kathleen R.; Groves, Lindsey T.; McGeehin, John P.; Randall Schumann, R.; Agenbroad, Larry D. (May 2015). "Late Quaternary sea-level history and the antiquity of mammoths ( Mammuthus exilis and Mammuthus columbi ), Channel Islands National Park, California, USA". Quaternary Research. 83 (3): 502–521. Bibcode:2015QuRes..83..502M. doi:10.1016/j.yqres.2015.03.001. ISSN 0033-5894.
1 2 van der Geer, Alexandra A. E.; van den Bergh, Gerrit D.; Lyras, George A.; Prasetyo, Unggul W.; Due, Rokus Awe; Setiyabudi, Erick; Drinia, Hara (August 2016). "The effect of area and isolation on insular dwarf proboscideans". Journal of Biogeography. 43 (8): 1656–1666. Bibcode:2016JBiog..43.1656V. doi:10.1111/jbi.12743. ISSN 0305-0270.
1 2 Kennett, D.J.; Kennett, J.P.; West, G.J.; Erlandson, J.M. (2008). "Wildfire and abrupt ecosystem disruption on California's Northern Channel Islands at the Ållerød–Younger Dryas boundary (13.0–12.9 ka)". Proceedings of the National Academy of Sciences. 104 (27–28): 2530–2545. Bibcode:2008QSRv...27.2530K. doi:10.1016/j.quascirev.2008.09.006.
1 2 3 Semprebon, Gina M.; Rivals, Florent; Fahlke, Julia M.; Sanders, William J.; Lister, Adrian M.; Göhlich, Ursula B. (June 2016). "Dietary reconstruction of pygmy mammoths from Santa Rosa Island of California". Quaternary International. 406: 123–136. Bibcode:2016QuInt.406..123S. doi:10.1016/j.quaint.2015.10.120.
↑ Agenbroad, L. D. (2010). "Mammuthus exilis from the California Channel Islands: Height, Mass and Geologic Age" (PDF). Proceedings of the 7th California Islands Symposium. p. 17. Archived from the original (PDF) on 8 June 2012. Retrieved 13 June 2012.
1 2 Larramendi, A. (2016). "Shoulder height, body mass and shape of proboscideans" (PDF). Acta Palaeontologica Polonica. 61. doi: 10.4202/app.00136.2014 . Retrieved November 21, 2015.
1 2 3 L.D. Agenbroad. (2003). New absolute dates and comparisons for California’s Mammuthus exilis. Deinsea, 9(1), 1–16.
↑ T. Htun, D.R. Prothero, J.M. Hoffman, S.M. Lukowski, V. Syverson Allometric trends in dwarfing in the extinct Pleistocene Channel Islands pigmy mammoth, Mammuthus exilis Fossil Record, 6 (1) (2018) 79
↑ Hofman, Courtney A.; Rick, Torben C.; Maldonado, Jesús E.; Collins, Paul W.; Erlandson, Jon M.; Fleischer, Robert C.; Smith, Chelsea; Sillett, T. Scott; Ralls, Katherine; Teeter, Wendy; Vellanoweth, René L.; Newsome, Seth D. (August 2016). "Tracking the origins and diet of an endemic island canid (Urocyon littoralis) across 7300 years of human cultural and environmental change". Quaternary Science Reviews. 146: 147–160. Bibcode:2016QSRv..146..147H. doi:10.1016/j.quascirev.2016.06.010.
↑ Hardiman, Mark; Scott, Andrew C.; Pinter, Nicholas; Anderson, R. Scott; Ejarque, Ana; Carter-Champion, Alice; Staff, Richard A. (2016-06-05). "Fire history on the California Channel Islands spanning human arrival in the Americas". Philosophical Transactions of the Royal Society B: Biological Sciences. 371 (1696): 20150167. doi:10.1098/rstb.2015.0167. ISSN 0962-8436. PMC 4874405 . PMID 27216524.

[1] Chester Stock and E. L. Furlong (1928). "The Pleistocene elephants of Santa Rosa Island, California" (PDF). Science. 68 (1754): 140–141. Bibcode:1928Sci....68..140S. doi:10.1126/science.68.1754.140. PMID 17772244.

[2] Agenbroad, L.D. (2003). "New absolute dates and comparisons for California's Mammuthus exilis". Deinsea. 9: 1–16.

[Johnson-3] 1 2 3 Agenbroad, L.D.; Johnson J.; Morris D.; Stafford T.W. "Mammoths and Humans as Late Pleistocene Contemporaries on Santa Rosa Island" (PDF). Proceedings of the American Geophysical Union. Spring Meeting 2007.

[Agenbroad-4] 1 2 Agenbroad, Larry D.; Don P. Morris. "Giant Island/Pygmy Mammoths:The Late Pleistocene Prehistory of Channel Islands National Park" (PDF). National Park Service Paleontological Research. 4: 35–39. Archived from the original (PDF) on 2014-02-19. Retrieved 2013-10-23.

[anonymous-5] ymous, anonymous. "Stranded on Santa Monica". Discover. 16: 1. ProQuest 206020333.

[:0-6] 1 2 3 4 5 Muhs, Daniel R.; Simmons, Kathleen R.; Groves, Lindsey T.; McGeehin, John P.; Randall Schumann, R.; Agenbroad, Larry D. (May 2015). "Late Quaternary sea-level history and the antiquity of mammoths ( Mammuthus exilis and Mammuthus columbi ), Channel Islands National Park, California, USA". Quaternary Research. 83 (3): 502–521. Bibcode:2015QuRes..83..502M. doi:10.1016/j.yqres.2015.03.001. ISSN 0033-5894.

[:3-7] 1 2 van der Geer, Alexandra A. E.; van den Bergh, Gerrit D.; Lyras, George A.; Prasetyo, Unggul W.; Due, Rokus Awe; Setiyabudi, Erick; Drinia, Hara (August 2016). "The effect of area and isolation on insular dwarf proboscideans". Journal of Biogeography. 43 (8): 1656–1666. Bibcode:2016JBiog..43.1656V. doi:10.1111/jbi.12743. ISSN 0305-0270.

[sciencedirect.com-8] 1 2 Kennett, D.J.; Kennett, J.P.; West, G.J.; Erlandson, J.M. (2008). "Wildfire and abrupt ecosystem disruption on California's Northern Channel Islands at the Ållerød–Younger Dryas boundary (13.0–12.9 ka)". Proceedings of the National Academy of Sciences. 104 (27–28): 2530–2545. Bibcode:2008QSRv...27.2530K. doi:10.1016/j.quascirev.2008.09.006.

[:1-9] 1 2 3 Semprebon, Gina M.; Rivals, Florent; Fahlke, Julia M.; Sanders, William J.; Lister, Adrian M.; Göhlich, Ursula B. (June 2016). "Dietary reconstruction of pygmy mammoths from Santa Rosa Island of California". Quaternary International. 406: 123–136. Bibcode:2016QuInt.406..123S. doi:10.1016/j.quaint.2015.10.120.

[10] Agenbroad, L. D. (2010). "Mammuthus exilis from the California Channel Islands: Height, Mass and Geologic Age" (PDF). Proceedings of the 7th California Islands Symposium. p. 17. Archived from the original (PDF) on 8 June 2012. Retrieved 13 June 2012.

[probos_mass-11] 1 2 Larramendi, A. (2016). "Shoulder height, body mass and shape of proboscideans" (PDF). Acta Palaeontologica Polonica. 61. doi: 10.4202/app.00136.2014 . Retrieved November 21, 2015.

[:4-12] 1 2 3 L.D. Agenbroad. (2003). New absolute dates and comparisons for California’s Mammuthus exilis. Deinsea, 9(1), 1–16.

[13] T. Htun, D.R. Prothero, J.M. Hoffman, S.M. Lukowski, V. Syverson Allometric trends in dwarfing in the extinct Pleistocene Channel Islands pigmy mammoth, Mammuthus exilis Fossil Record, 6 (1) (2018) 79

[14] Hofman, Courtney A.; Rick, Torben C.; Maldonado, Jesús E.; Collins, Paul W.; Erlandson, Jon M.; Fleischer, Robert C.; Smith, Chelsea; Sillett, T. Scott; Ralls, Katherine; Teeter, Wendy; Vellanoweth, René L.; Newsome, Seth D. (August 2016). "Tracking the origins and diet of an endemic island canid (Urocyon littoralis) across 7300 years of human cultural and environmental change". Quaternary Science Reviews. 146: 147–160. Bibcode:2016QSRv..146..147H. doi:10.1016/j.quascirev.2016.06.010.

[:2-15] Hardiman, Mark; Scott, Andrew C.; Pinter, Nicholas; Anderson, R. Scott; Ejarque, Ana; Carter-Champion, Alice; Staff, Richard A. (2016-06-05). "Fire history on the California Channel Islands spanning human arrival in the Americas". Philosophical Transactions of the Royal Society B: Biological Sciences. 371 (1696): 20150167. doi:10.1098/rstb.2015.0167. ISSN 0962-8436. PMC 4874405 . PMID 27216524.

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