Editing Pygmy mammoth

{{Short description|Species of mammoth}}
{{Speciesbox
| name = Pygmy mammoth
| fossil_range = [[Late Pleistocene]] {{fossil range|0.08|0.013}}
| image = Mammuthus exilis.jpg
| image_caption = Skeleton at the [[Santa Barbara Museum of Natural History]]
| image2 = Pygmy mammoth model - Cleveland Museum of Natural History - 2014-12-26 (20426146573).jpg
| image2_caption = Model of a pygmy mammoth (front) at the [[Cleveland Museum of Natural History]]
| genus = Mammuthus
| species = exilis
| authority = (Stock & Furlong, 1928)<ref>{{cite journal |author=Chester Stock and E. L. Furlong |year=1928 |title=The Pleistocene elephants of Santa Rosa Island, California |journal=Science |volume=68 |issue=1754 |pages=140–141 |doi=10.1126/science.68.1754.140 |bibcode = 1928Sci....68..140S |pmid=17772244 |url=https://core.ac.uk/download/pdf/232284955.pdf }}</ref>
}}

The '''pygmy mammoth''' or '''Channel Islands mammoth''' ('''''Mammuthus exilis''''') is an [[extinct]] [[species]] of [[dwarf elephant|dwarf mammoth]] native to the northern [[Channel Islands (California)|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 {{convert|1.72|-|2.02|m|ft|abbr=on}} 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==
[[File:Pygmy mammoth.JPG|thumb|left|Excavation in 1994, Santa Rosa]]
Mammoth remains have been known on the northern [[Channel Islands (California)|Channel Islands]] of [[California]] since 1856. They were first reported in scientific literature in 1873.<ref>{{cite journal|last1=Agenbroad|first1=L.D.|title=New absolute dates and comparisons for California's Mammuthus exilis|journal=Deinsea |volume=9 |pages=1–16  |date=2003}}</ref>

In 1994 the [[National Park Service]] called in scientists to inspect an uncovered, unidentified skeleton found on the northeast coast of [[Santa Rosa Island, California|Santa Rosa Island]].<ref name=Johnson>{{cite journal | last = Agenbroad | first = L.D. |author2=Johnson J. |author3=Morris D. |author4=Stafford T.W. | title = Mammoths and Humans as Late Pleistocene Contemporaries on Santa Rosa Island | journal =Proceedings of the American Geophysical Union  | volume = Spring Meeting 2007 | url = http://www.iws.org/CISProceedings/6th_CIS_Proceedings/Agenbroad.pdf }}</ref> 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.<ref name = Agenbroad/> The mammoth was about 50 years old when it died.<ref name=Johnson/> 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]].<ref name=Agenbroad>{{cite journal | last = Agenbroad | first = Larry D. | author2 = Don P. Morris | title = Giant Island/Pygmy Mammoths:The Late Pleistocene Prehistory of Channel Islands National Park | journal = National Park Service Paleontological Research | volume = 4 | pages = 35–39 | url = http://doc.rero.ch/record/31563/files/PAL_E647.pdf#page=35 | format = PDF | access-date = 2013-10-23 | archive-url = https://web.archive.org/web/20140219071055/http://doc.rero.ch/record/31563/files/PAL_E647.pdf#page=35 | archive-date = 2014-02-19 | url-status = dead }}</ref>
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.<ref name=Johnson/> 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.<ref name= anonymous>{{cite journal | last=anonymous | first= anonymous | journal= Discover | volume= 16 | pages= 1 | title= Stranded on Santa Monica| id= {{ProQuest|206020333}} }}</ref>

== Distribution ==
[[File:Californian Channel Islands map en.png|left|thumb|Northern Channel Islands which ''M. exilis'' inhabited shown in dark green, with maximum extent of Santa Rosae shown in light blue surrounding the islands]]
Remains of ''M. exilis'' have been discovered on three of the northern Channel Islands of California: [[Santa Cruz Island|Santa Cruz]], [[Santa Rosa Island, California|Santa Rosa]], and [[San Miguel Island|San Miguel]], which together with [[Anacapa Island|Anacapa]] were the highest portions of the now mostly submerged superisland of [[Santa Rosae]] which existed during times of lowered sea level.<ref name=":0">{{Cite journal |last1=Muhs |first1=Daniel R. |last2=Simmons |first2=Kathleen R. |last3=Groves |first3=Lindsey T. |last4=McGeehin |first4=John P. |last5=Randall Schumann |first5=R. |last6=Agenbroad |first6=Larry D. |date=May 2015 |title=Late Quaternary sea-level history and the antiquity of mammoths ( Mammuthus exilis and Mammuthus columbi ), Channel Islands National Park, California, USA |url=https://www.cambridge.org/core/product/identifier/S003358940000096X/type/journal_article |journal=Quaternary Research |language=en |volume=83 |issue=3 |pages=502–521 |bibcode=2015QuRes..83..502M |doi=10.1016/j.yqres.2015.03.001 |issn=0033-5894|url-access=subscription }}</ref> The area of the combined island has been estimated at {{Convert|2200|km2}},<ref name=":3" /> though the area of the island fluctuated as a result of glacial cycles.<ref name=":0" />

==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.<ref name=":0" /> During these times, the distance to the mainland was reduced to a minimum of {{convert|7|km}},<ref name="sciencedirect.com">{{Cite journal |last1=Kennett |first1=D.J. |last2=Kennett |first2=J.P. |last3=West |first3=G.J. |last4=Erlandson |first4=J.M. |date=2008 |title=Wildfire and abrupt ecosystem disruption on California's Northern Channel Islands at the Ållerød–Younger Dryas boundary (13.0–12.9 ka) |url=https://digitalcommons.calpoly.edu/ssci_fac/24 |journal=Proceedings of the National Academy of Sciences |volume=104 |issue=27–28 |pages=2530–2545 |bibcode=2008QSRv...27.2530K |doi=10.1016/j.quascirev.2008.09.006|url-access=subscription }}</ref> 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.<ref name=":0" /> 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 elephant]]s known from islands in the Mediterranean.<ref name=":1">{{Cite journal |last1=Semprebon |first1=Gina M. |last2=Rivals |first2=Florent |last3=Fahlke |first3=Julia M. |last4=Sanders |first4=William J. |last5=Lister |first5=Adrian M. |last6=Göhlich |first6=Ursula B. |date=June 2016 |title=Dietary reconstruction of pygmy mammoths from Santa Rosa Island of California |url=https://linkinghub.elsevier.com/retrieve/pii/S1040618215014020 |journal=Quaternary International |language=en |volume=406 |pages=123–136 |doi=10.1016/j.quaint.2015.10.120|bibcode=2016QuInt.406..123S |url-access=subscription }}</ref>

== Description ==
[[File:M. exilis skeletal.png|thumb|Size of the mostly complete Santa Rosa specimen discovered in 1994 compared to a human]]
''M. exilis'' was on average, {{convert|1.72|-|2.02|m|ft|abbr=on}} tall at the shoulders and {{convert|760|-|1350|kg|lb|abbr=on}} in weight,<ref>{{cite web |last=Agenbroad |first=L. D. |year=2010 |title=Mammuthus exilis from the California Channel Islands: Height, Mass and Geologic Age |url=http://iws.org/CISProceedings/7th_CIS_Proceedings/Agenbroad.pdf |url-status=dead |archive-url=https://web.archive.org/web/20120608211048/https://www.iws.org/CISProceedings/7th_CIS_Proceedings/Agenbroad.pdf |archive-date=8 June 2012 |access-date=13 June 2012 |work=Proceedings of the 7th California Islands Symposium |page=17}}</ref><ref name="probos_mass">{{Cite journal |last1=Larramendi |first1=A. |year=2016 |title=Shoulder height, body mass and shape of proboscideans |url=https://www.app.pan.pl/archive/published/app61/app001362014.pdf |journal=Acta Palaeontologica Polonica |volume=61 |doi=10.4202/app.00136.2014 |access-date=November 21, 2015 |doi-access=free}}</ref> making it around 17% of the body size of its {{convert|3.72|-|4.2|m|ft|abbr=on}} tall, {{convert|9.2|-|12.5|t|LT ST|abbr=on}} ancestor.<ref name="probos_mass" /><ref name=":3">{{Cite journal |last1=van der Geer |first1=Alexandra A. E. |last2=van den Bergh |first2=Gerrit D. |last3=Lyras |first3=George A. |last4=Prasetyo |first4=Unggul W. |last5=Due |first5=Rokus Awe |last6=Setiyabudi |first6=Erick |last7=Drinia |first7=Hara |date=August 2016 |title=The effect of area and isolation on insular dwarf proboscideans |url=https://onlinelibrary.wiley.com/doi/10.1111/jbi.12743 |journal=Journal of Biogeography |language=en |volume=43 |issue=8 |pages=1656–1666 |doi=10.1111/jbi.12743 |bibcode=2016JBiog..43.1656V |issn=0305-0270}}</ref> Like other mammoths, the species exhibited sexual dimorphism, with males being larger than females.<ref name=":4">L.D. Agenbroad. (2003). [https://natuurtijdschriften.nl/pub/538667/DEIN2003009001002.pdf New absolute dates and comparisons for California’s ''Mammuthus exilis'']. ''Deinsea'', ''9''(1), 1–16.</ref> The limb bones of the species show [[Allometry#Isometric scaling and geometric similarity|isometric growth]] (preserving length-width ratio) from juveniles to adults, similar to those of living [[African elephant]]s.<ref>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</ref> 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.<ref name=":4" />

== 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 (herbivory)|browsing]] based diet on leaves and twigs, as opposed to the more grazing focused diet of its Columbian mammoth ancestors.<ref name=":1" /> In comparison to its larger ancestor, it likely had the ability to ascend somewhat steeper slopes.<ref name=":4" /> The island exhibited a depauperate fauna that lacked large predators.<ref name="sciencedirect.com" /> 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.<ref>{{Cite journal |last1=Hofman |first1=Courtney A. |last2=Rick |first2=Torben C. |last3=Maldonado |first3=Jesús E. |last4=Collins |first4=Paul W. |last5=Erlandson |first5=Jon M. |last6=Fleischer |first6=Robert C. |last7=Smith |first7=Chelsea |last8=Sillett |first8=T. Scott |last9=Ralls |first9=Katherine |last10=Teeter |first10=Wendy |last11=Vellanoweth |first11=René L. |last12=Newsome |first12=Seth D. |date=August 2016 |title=Tracking the origins and diet of an endemic island canid (Urocyon littoralis) across 7300 years of human cultural and environmental change |url=https://linkinghub.elsevier.com/retrieve/pii/S0277379116302104 |journal=Quaternary Science Reviews |language=en |volume=146 |pages=147–160 |doi=10.1016/j.quascirev.2016.06.010|bibcode=2016QSRv..146..147H }}</ref>

==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 [[wildfire]]s. It is therefore difficult to disentangle the precise causes of its extinction,<ref name=":1" /><ref name=":2">{{Cite journal |last1=Hardiman |first1=Mark |last2=Scott |first2=Andrew C. |last3=Pinter |first3=Nicholas |last4=Anderson |first4=R. Scott |last5=Ejarque |first5=Ana |last6=Carter-Champion |first6=Alice |last7=Staff |first7=Richard A. |date=2016-06-05 |title=Fire history on the California Channel Islands spanning human arrival in the Americas |journal=Philosophical Transactions of the Royal Society B: Biological Sciences |language=en |volume=371 |issue=1696 |pages=20150167 |doi=10.1098/rstb.2015.0167 |issn=0962-8436 |pmc=4874405 |pmid=27216524}}</ref> though the pygmy mammoths had likely survived a greater reduction in island area during the preceding [[Last Interglacial]]/[[Sangamonian]].<ref name=":0" />

==See also==
{{Portal|Paleontology}}
*''[[Mammuthus lamarmorai]]'', a dwarf mammoth species known from the Middle-Late Pleistocene of Sardinia
*''[[Mammuthus creticus]]'', a dwarf mammoth species known from the Early Pleistocene of Crete.

== References ==
{{reflist}}
{{Wikispecies|Mammuthus exilis}}
{{Elephants}}
{{Taxonbar|from=Q244237}}

[[Category:Mammoths]]
[[Category:Pleistocene proboscideans]]
[[Category:Fauna of the Channel Islands of California]]
[[Category:Pleistocene California]]
[[Category:Pleistocene first appearances|Mammoth Pygmy]]
[[Category:Holocene extinctions]]
[[Category:Extinct animals of the United States|Mammoth Pygmy]]
[[Category:Fossil taxa described in 1928]]
[[Category:Pleistocene mammals of North America]]