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Camelops

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Camelops
Temporal range: Late Pliocene to late Pleistocene, 3.2–0.013 Ma
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Mounted skeleton of Camelops hesternus in the George C. Page Museum, Los Angeles
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Family: Camelidae
Subfamily: Camelinae
Tribe: Camelini
Genus: †Camelops
Leidy, 1854
Species

†Camelops kansanus Leidy, 1854 †Camelops hesternus Leidy, 1873 (type)
†Camelops minidokae Hay, 1927

Camelops[Note 1] is an extinct genus of camels that lived in North and Central America, ranging from Alaska to Honduras,[1] from the middle Pliocene to the end of the Pleistocene. It is more closely related to the Old World dromedary and bactrian and wild bactrian camels than to the New World guanaco, vicuña, alpaca and llama; making it a true camel of the Camelini tribe.[1][2] Its name is derived from the Ancient Greek κάμηλος (cámēlos, "camel")[3] and ὄψ (óps, "face"),[4] i.e. "camel-face".

Taxonomy and evolution

Camelops vertebra

The genus Camelops first appeared during the middle Pliocene (about 4.0–3.2 million years ago (Mya) in southern North America and last being known around the latest Pleistocene (around 13,000 years ago). Despite the fact that camels are popularly associated with the deserts of Asia and Africa, the family Camelidae, which comprises camels and llamas, originated in North America during the middle Eocene period, at least 44 Mya.[5] Both the camel and horse families originated in North America and migrated into Eurasia via the Bering Strait.[6] Modern camels are descended from the extinct genus Paracamelus, which crossed the Bering land bridge into Asia approximately 7.5 to 6.5 million years ago. The divergence between Paracamelus and Camelops occurred about 11–10 Million years ago. Paracamelus would continue to live in North America as the High Arctic camel until the middle Pleistocene.

During Pleistocene warm periods, a smaller morph of Camelops inhabited Alaska and northern Yukon. These specimens date to around 50–45 thousand years ago, and seem to have been extirpated from the area after this time, similar to the contemporaneous mastodon, the ground sloth Megalonyx, and the giant beaver Castoroides. The skull of a Camelops specimen was found above the Glenns Ferry Formation in present-day Idaho in a thick layer of coarse gravel known as the Tauna Gravels. Above this layer of gravel is another layer of fine river channel sands, where the skull was found. The age of this fossil is as young as 2 million years old and perhaps even younger, which can be inferred because it is younger than the other fossils found at the Hagerman Fossil Beds National Monument.[7]

During the late Oligocene and early Miocene periods, camels apparently underwent swift evolutionary change, resulting in several genera with different anatomical structures, ranging from those with short limbs, those with gazelle-like bodies, and giraffe-like camels with long legs and long necks. This rich diversity decreased until only a few species, such as Camelops hesternus, remained in North America, before going extinct entirely around 11,000 years ago.[5] By the end of the Pleistocene, with the extinction of Paracamelus and Titanotylopus, Camelops was the only true camel remaining in North America and possibly both Americas. Camelops's extinction was part of a larger North American extinction in which native horses, mastodons, and other camelids also died out. Possible causal factors for this megafaunal extinction include global climate change and hunting pressure from human beings. The mass extinction coincided roughly with the appearance of people belonging to the big game-hunting Clovis culture, who were prolific hunters with distinct fluted stone tools, which allowed for a spear shaft to be attached to the stone tool.[5][6] Biochemical analyses have shown that Clovis tools were used in butchering camels.[8]

Description

Reconstruction of C. hesternus

Because soft tissues are generally not preserved in the fossil record, it is not certain if Camelops possessed hump(s), like modern camels, or lacked ones, like modern camelids of South America (guanacos and vicuñas). One-humped camels are now known to have evolved from two-humped camels, but two-humps, as an evolutionary outcome, likely associated with arctic climates and two-humped camels presumably evolved into one-humped camels in warmer regions in Eurasia,[9] while Camelops first appeared in southern North America and lived among both warmer and colder regions of the continent until early Holocene.

C. hesternus had legs 20% longer than that of the dromedary, and was about 2.3 m (7 ft 7 in) tall at the shoulder and weighed about 1,000 kg (2,200 lb).[10]

Palaeobiology

The species ranged widely from Alaska in the north to Oregon and California in the west, southernmost Baja California Peninsula and Mexico and Guatemala in the south, and Tennessee in the east, and a notable number of fossils have been excavated among central North America such as at Colorado and California.[1][11]

Plant remains found in the teeth of the Rancho La Brea C. hesternus fossils further reveal that rather than being limited to grazing, this species likely ate mixed species of plants, including coarse shrubs growing in coastal southern California. Camelops probably could travel long distances, similar to modern camel species. Whether or not Camelops could survive for long periods without water, as with extant camels, is still unknown; this may have been an adaptation that occurred much later, after camelids migrated to Asia and Africa.[12]

The creosote bush from the US-Mexican border has been speculated to be part of Camelops's diet. Although no living ungulate in the area consumes it, it was readily consumed by the Arabian camels of the experimental United States Camel Corps in the mid-19th century.[13]

Extinction

A 68,000-year-old C. hesternus skeleton at the Waco Mammoth National Monument

The last species of Camelops are hypothesized to have disappeared as a result of the Blitzkrieg model. This model presents the hypothesis that Camelops, along with other North American megafauna, disappeared as new cultures of experienced and efficient hunters moved southeastward across the continent. The result of this migration and expansion of human populations was a significant reduction in range for the megafauna.[14] Of the many Camelops specimens recovered in North America, only a small number demonstrate modification through human actions.[15] Some specimens have been interpreted as having been killed by humans based on the presence of spirally fractured bone fragments. None of the reported Camelops sites has been associated with stone tools, however, which would be an indicator of possible human use.[15]

At many of these Camelops sites, no fossils have been found of carcasses that were evidently processed, but rather small fragments and pieces of remains. Researchers originally thought that Camelops species were in fact hunted and butchered by early humans in North America because of these reasons: the fragmenting of bones into shapes that look like tools, damage or weathering of the “working” edge of said tools, having attributes that were similar to the making of chopping tools, and scarred fragments from possible chopping tools.[15] Further examination showed, though, that these assumptions were misguided, and that while humans did coexist and associate with Camelops, human use has yet to be completely proven as the sole cause of extinction.[15]

See also

References

  1. ^ Being occasionally called Western Camel or Yesterday's Camel.
  1. ^ a b c Heintzman, Peter D.; Zazula, Grant D.; Cahill, James A.; Reyes, Alberto V.; MacPhee, Ross D.E.; Shapiro, Beth (2 June 2015). "Genomic Data from Extinct North American Camelops Revise Camel Evolutionary History". Molecular Biology and Evolution. 32 (9): 2433–2440. doi:10.1093/molbev/msv128. PMID 26037535.
  2. ^ Saitou, Naruya; Shokat, Shayire (2017). "DNA Analyses of Camels". Journal of Arid Land Studies. 26 (4): 223–226.
  3. ^ κάμηλος. Liddell, Henry George; Scott, Robert; A Greek–English Lexicon at the Perseus Project
  4. ^ ὄψ. Liddell, Henry George; Scott, Robert; A Greek–English Lexicon at the Perseus Project
  5. ^ a b c "Camelops". Anza-Borrego Desert State Park Paleontology Society. Archived from the original on 2011-09-04.
  6. ^ a b Hutchinson, Jon (2012-08-14). "Camel Country: Where have all our camelops gone?". Verde Independent.
  7. ^ National Park Service. "Camelops". Hagerman Fossil Beds. U.S. Department of the Interior.
  8. ^ Scott, J. (2009-02-26). "Camel-butchering in Boulder, 13,000 years ago". Colorado Arts and Sciences Magazine. University of Colorado at Boulder. Archived from the original on 2010-06-10. Retrieved 2009-05-01.
  9. ^ "Evolutionary History | Camels". blogs.lt.vt.edu. Retrieved 2018-05-29.
  10. ^ Anthony J. Stuart, 2021, Vanished Giants: The Lost World of the Ice Age, "6.17 Yesterday's Camel: Camelops Hesternus", p.99, University of Chicago Press
  11. ^ Murray, Marian (1974). Hunting for Fossils: A Guide to Finding and Collecting Fossils in All 50 States. Collier Books. p. 262. ISBN 9780020935506.
  12. ^ Museum, San Diego Natural History. "San Diego Natural History Museum Fossil Mysteries Field Guide: Extinct Camel". Sdnhm.org. Retrieved 10 November 2017.
  13. ^ THE US ARMY'S CAMEL CORPS by C. F. Eckhardt
  14. ^ Beck, Michael W. (10 November 1996). "On Discerning the Cause of Late Pleistocene Megafaunal Extinctions". Paleobiology. 22 (1): 91–103. Bibcode:1996Pbio...22...91B. doi:10.1017/s0094837300016043. JSTOR 2401044. S2CID 85102271.
  15. ^ a b c d Haynes, Gary; Stanford, Dennis (September 1984). "On the possible utilization of Camelops by early man in North America" (PDF). Quaternary Research. 22 (2): 216–230. Bibcode:1984QuRes..22..216H. doi:10.1016/0033-5894(84)90041-3. S2CID 129762421. Archived from the original (PDF) on 2014-03-09. Retrieved 2012-10-26.
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