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Oryzomys nelsoni

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Oryzomys nelsoni
Skull with the number 89200 written on it.
Skull ofOryzomys nelsoni,seen from above.[1]
Scientific classificationEdit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Rodentia
Family: Cricetidae
Subfamily: Sigmodontinae
Genus: Oryzomys
Species:
†O. nelson
Binomial name
†Oryzomys nelson
Merriam,1898
Map of western Mexico with a green mark on the southern tip of the Baja California peninsula, an orange mark off the coast of Nayarit, a pink area inland in the southwest, and a red area along the Pacific coast north to Sonora.
Distribution ofOryzomys nelsoni(orange) and other western MexicanOryzomys.
Synonyms[5]
  • Oryzomys nelsoniMerriam, 1898[3]
  • [Oryzomys palustris] nelsoni:Hershkovitz, 1971[4]

Oryzomys nelsoni,also known asNelson’s Rice Rat,is anextinctrodentofMaría Madre Island,Nayarit,Mexico.Within the genusOryzomysof the familyCricetidae,it may have been most closely related to the mainland speciesO. albiventer.Since its first description in 1898, most authors have regarded it as a distinct species, but it has also been classified as a meresubspeciesof themarsh rice rat(O. palustris).

After its discovery in 1897, it has never been recorded again and it is now considered extinct; the presence ofintroducedblack ratson María Madre may have contributed to its extinction.Oryzomys nelsoniwas a large species, distinguished in particular by its long tail, robust skull, and largeincisors.It was reddish to yellowish above and mostly white below. Its diet may have included plant material and small animals.

Taxonomy

[edit]

Oryzomys nelsoniwas collected byEdward William NelsonandEdward Goldmanin May 1897 and never found again.[6]Their visit for the Biological Survey of theUnited States Department of Agriculturewas one of the first scientific exploration of the islands.[7]Clinton Hart Merriamidentified the mammals they obtained, including four specimens ofOryzomys nelsoni,which were deposited in theUnited States National Museumand remain there.[8]He named it as a species of the genusOryzomys,Oryzomys nelsoni;thespecific namehonors Nelson.[9]Investigators have generally retained it as a species distinct from otherOryzomys,[10]but in 1971Hershkovitzlisted it as one of many subspecies ofOryzomys palustris,[4]which he envisaged as a wide-ranging species encompassing what is now themarsh rice rat(O. palustris) of the southern and eastern United States,O. couesiof Central America, and several other species with more limited distributions.[11]

In his 1918 revision of North AmericanOryzomys,Goldman consideredO. nelsonito be most closely related to the nearest mainlandsubspeciesofO. couesi,O. couesi mexicanus.In 2009, Michael Carleton and Joaquin Arroyo-Cabrales revised theOryzomysof western Mexico and confirmed thatO. nelsoniis a very distinct species. Theirmorphometricalanalysis found some resemblance between the species andOryzomys albiventerof interior mainland Mexico, and they suggested that althoughO. nelsonilikely represents an old, distinctive lineage, it may have derived from a common ancestor withO. albiventer.[12]

Oryzomys nelsoniis one of about eight species in the genusOryzomys,which occurs from the easternUnited States(O. palustris) into northwesternSouth America(O. gorgasi).[13]O. nelsoniis further part of theO. couesisection, which is centered on the widespread Central AmericanO. couesiand also includes various other species with more limited and peripheral distributions.[14]Many aspects of thesystematicsof theO. couesisection remain unclear and it is likely that the current classification underestimates the true diversity of the group.[15]Oryzomyspreviously included many other species, which were progressively removed in various studies culminating in a contribution by Marcelo Weksler and coworkers in 2006 that removed more than forty species from the genus.[16]All are classified in the tribeOryzomyini( "rice rats" ), a diverse assemblage of American rodents of over a hundred species,[17]and on higher taxonomic levels in the subfamilySigmodontinaeof familyCricetidae,along with hundreds of other species of mainly small rodents.[18]

Common namesproposed for this species include Nelson rice rat,[19]Nelson's rice rat,[10]Nelson's oryzomys,[20]and Tres Marias Island rice rat.[2]

Description

[edit]
See caption.
Skull ofOryzomys nelsoni,seen from below.[21]

Oryzomys nelsoniwas a large and long-tailedOryzomys;[10]its tail was longer than that of any other western MexicanOryzomys.[5]The upperparts wereochraceoustobuff,most richly so on the rump, and paler further to the front and low on the flanks. On the head and the back, blackish hairs somewhat darkened the overall color. The underparts were white, with lead-colored underfur that was visible in some places. The ears were covered on both sides with scanty grayish hairs.[10]The large hindfeet[5]were sparsely covered with pale hairs. The tail was largely dark, but the underside of the basal one third to one half was light yellow.[10]

Oryzomys nelsoniwas distinctive in its large skull with broad, well-developedincisorsand a strong front part (rostrum) that is strongly curved downwards.[22]InO. albiventer,the rostrum and incisors were not as massive, but the molars are larger.[5]Theinterparietalbone, part of the roof of thebraincase,was broad and theincisive foramina,which perforated thepalatebetween the incisors and themolars,were relatively short.[10]

Total length in the four known specimens is 282 to 344 mm (11.1 to 13.5 in), averaging 322 mm (12.7 in); head and body length is 122 to 153 mm (4.8 to 6.0 in), averaging 140.5 mm (5.53 in); tail length is 160 to 191 mm (6.3 to 7.5 in), averaging 181.5 mm (7.15 in); and hindfoot length is 35 to 39 mm (1.4 to 1.5 in), averaging 37.3 mm (1.47 in).[23]

Ecology and extinction

[edit]

Nelson and Goldman found the species only in a damp, herbaceous site now known as the "Sacatal" near a spring high onMaría Madre Island,the largest of theIslas Maríasoff the coast ofNayarit,western Mexico,[24]and Nelson wrote that it was rare. He gave the elevation of this place as 1800 ft,[25]which Álvarez-Castañeda and Méndez converted to 550 m,[10]but in his 1918 paper, Goldman gave 800 ft instead,[19]which Carleton and Arroyo-Cabrales in 2009 converted to 245 m.[26]The next survey of small mammals on the island took place in March 1976 by a team led byDon E. Wilson.They failed to collectO. nelsoniand instead found only theintroducedblack rat(Rattus rattus) at the locality where Nelson and Goldman had collectedO. nelsoni;this species may have contributed to the decline of the indigenous rodent.[27]

The species is now considered extinct,[28]although as late as 2002 the Mexican government listed it as "threatened".[29]Another Islas Maríasendemic,thedeermousePeromyscus madrensis,still occurred on María Madre in 1976.[30]Oryzomys nelsoniis thought to have fed on plant material such as weeds, fruit, and seeds, and more rarely on animals such as fish and invertebrates.[10]

References

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  1. ^Goldman, 1918, plate II, fig. 1
  2. ^abTimm, R., Álvarez-Castañeda, S.T. & Lacher, T. 2017. Oryzomys nelsoni. The IUCN Red List of Threatened Species 2017: e.T15583A22388135.https://dx.doi.org/10.2305/IUCN.UK.2017-3.RLTS.T15583A22388135.en.Downloaded on 11 March 2021.
  3. ^Merriam, 1898, p. 15
  4. ^abHershkovitz, 1971, p. 704
  5. ^abcdCarleton and Arroyo-Cabrales, 2009, p. 122
  6. ^Carleton and Arroyo-Cabrales, 2009, p. 114; Nelson, 1899a, pp. 7–8
  7. ^Nelson, 1899a, pp. 7–8; Merriam, 1899, p. 13
  8. ^Merriam, 1898, p. 13; Nelson, 1899a, p. 15; Carleton and Arroyo-Cabrales, 2009, p. 122
  9. ^Merriam, 1898, p. 15; Álvarez-Castañeda and Méndez, 2003, p. 2
  10. ^abcdefghÁlvarez-Castañeda and Méndez, 2003, p. 1
  11. ^Musser and Carleton, 2005, pp. 1147, 1152–1153; Carleton and Arroyo-Cabrales, 2009, p. 116
  12. ^Carleton and Arroyo-Cabrales, 2009, p. 110
  13. ^Carleton and Arroyo-Cabrales, 2009, p. 106
  14. ^Carleton and Arroyo-Cabrales, 2009, p. 117
  15. ^Carleton and Arroyo-Cabrales, 2009, p. 107
  16. ^Weksler et al., 2006, table 1
  17. ^Weksler, 2006, p. 3
  18. ^Musser and Carleton, 2005
  19. ^abGoldman, 1918, p. 46
  20. ^Musser and Carleton, 2005, p. 1152
  21. ^Goldman, 1918, plate II, fig. 1a
  22. ^Carleton and Arroyo-Cabrales, 2009, p. 121
  23. ^Carleton and Arroyo-Cabrales, 2009, table 2
  24. ^Álvarez-Castañeda and Méndez, 2003, p. 1; Carleton and Arroyo-Cabrales, 2009, p. 114
  25. ^Nelson, 1899b, p. 16
  26. ^Carleton and Arroyo-Cabrales, 2009, p. 114
  27. ^Wilson, 1991, p. 239; Carleton and Arroyo-Cabrales, 2009, p. 114
  28. ^Álvarez-Castañeda and Méndez, 2003, p. 1; Musser and Carleton, 2005, p. 1152; Timm et al., 2008; Carleton and Arroyo-Cabrales, 2009, p. 114
  29. ^Álvarez-Castañeda and Méndez, 2003, p. 2
  30. ^Musser and Carleton, 2005, p. 1071; Carleton and Arroyo-Cabrales, 2009, p. 114

Literature cited

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  • Álvarez-Castañeda, S.T. and Méndez, L. 2003.Oryzomys nelsoni.Mammalian Species735:1–2.
  • Carleton, M.D. and Arroyo-Cabrales, J. 2009.Review of theOryzomys couesicomplex (Rodentia: Cricetidae: Sigmodontinae) in western Mexico.Bulletin of the American Museum of Natural History331:94–127.
  • Goldman, E.A. 1918.The rice rats of North America.North American Fauna43:1–100.
  • Merriam, C.H. 1898.Mammals from the Tres Marias Islands, off western Mexico.Proceedings of the Biological Society of Washington12:13–19.
  • Musser, G.G. and Carleton, M.D. 2005. Superfamily Muroidea. Pp. 894–1531 in Wilson, D.E. and Reeder, D.M. (eds.).Mammal Species of the World: a taxonomic and geographic reference.3rd ed.Baltimore: The Johns Hopkins University Press, 2 vols., 2142 pp.ISBN978-0-8018-8221-0
  • Nelson, E.W. 1899a.General description of the Tres Marias Islands, Mexico.North American Fauna14:7–14.
  • Nelson, E.W. 1899b.Mammals of the Tres Marias Islands.North American Fauna14:15–20.
  • Weksler, M. 2006.Phylogenetic relationships of oryzomyine rodents (Muroidea: Sigmodontinae): separate and combined analyses of morphological and molecular data.Bulletin of the American Museum of Natural History296:1–149.
  • Weksler, M., Percequillo, A.R. and Voss, R.S. 2006.Ten new genera of oryzomyine rodents (Cricetidae: Sigmodontinae).American Museum Novitates3537:1–29.
  • Wilson, D.E. 1991.Mammals of the Tres Marías Islands.Bulletin of the American Museum of Natural History206:214–250.

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