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Oryzomys antillarum

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Oryzomys antillarum
See caption.
Holotypeskull, seen from above, below, and the left[1]
Scientific classificationEdit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Rodentia
Family: Cricetidae
Subfamily: Sigmodontinae
Genus: Oryzomys
Species:
†O. antillarum
Binomial name
†Oryzomys antillarum
Thomas,1898
See image description.
Distribution ofOryzomys antillarum(green) and other species ofOryzomys,includingO. couesi(red) and themarsh rice rat(O. palustris;blue)
Synonyms[fn 1][6]
  • Oryzomys antillarumThomas, 1898[3]
  • Oryzomys palustris antillarum:Hershkovitz, 1966[4]
  • [Oryzomys couesi] antillarum:Honacki et al., 1982[5]

Oryzomys antillarum,also known as theJamaican rice rat,[7]is anextinctrodentofJamaica.A member of the genusOryzomyswithin the familyCricetidae,it is similar toO. couesiof mainlandCentral America,from where it may have dispersed to its island during thelast glacial period.O. antillarumis common insubfossilcave faunas and is also known from three specimens collected live in the 19th century. Some historical records of Jamaican rats may pertain to it. The species probably became extinct late in the 19th century, perhaps due to theintroductionof thesmall Indian mongoose,competition with introduced rodents such as thebrown rat,andhabitat destruction.

Oryzomys antillarumwas a medium-sized rat, similar in most respects toOryzomys couesi.The head and body length was 120 to 132 mm (4.7 to 5.2 in) and the skull was about 30 mm (1.2 in) long. The upperparts were reddish and graded into the yellowish underparts. The tail was about as long as the head and body, sparsely haired, and darker above than below. The species differed fromO. couesiin having longernasal bones,shorterincisive foramina(perforations of the front part of thepalate), and more robustzygomatic arches(cheekbones).

Taxonomy

In his 1877monographon North American rodents,Elliott Couesmentioned two specimens ofOryzomysfrom Jamaica in the collections of theUnited States National Museum(USNM). According to Coues, the specimens were similar to themarsh rice rat(Oryzomys palustris) of theUnited States,but different in color. Although he wrote that they probably represented a separate form, he refrained from giving a scientific name to them because of the possibility that the form had already received a name he did not know of.[8]The species was first formally described byOldfield Thomasin 1898 based on a specimen that had been in theBritish Museum of Natural Historysince 1845. He recognized it as a separate species ofOryzomys,Oryzomys antillarum,but wrote that it was related to the mainland Central AmericanO. couesi.Thomas suspected that the species was already extinct on Jamaica, but that it or a similar rice rat could still be found in the unexplored interior ofCubaorHispaniola.[3]

Revising North AmericanOryzomysin 1918,Edward Alphonso GoldmanretainedO. antillarumas a separate species, but conceded that it was so similar to mainlandO. couesithat it may have been introduced on Jamaica.[9]In 1920,Harold Anthonyreported that remains ofO. antillarumwere common in coastal caves, suggesting that the species had previously been an important part of the diet of thebarn owl(Tyto alba).[10]In 1942,Glover Morrill Allendoubted that it was even a distinct species[11]and in his 1962 Ph.D. thesis, Clayton Ray, who examined numerous cave specimens, agreed and retained it as only a "weakly differentiated subspecies" ofOryzomys palustris(which by then includedO. couesiand other Mexican and Central American forms),Oryzomys palustris antillarum.[12]Philip Hershkovitzcame to the same conclusion in a 1966 paper.[4]AfterO. couesiof Mexico and Central America was again classified as a species distinct from the marsh rice rat (O. palustris) of the United States, the Jamaican form came to be regarded as a subspecies of the former,Oryzomys couesi antillarum.[5]

In a 1993 review, Gary Morgan reinstated the animal as a distinct species closely related toO. couesi,citing an unpublished paper by Humphrey, Setzer, and himself.[6]Guy Musserand Michael Carleton, writing for the 2005 third edition ofMammal Species of the World,continued to classify the Jamaican form as part ofO. couesi,but did not reference Morgan.[13]However, in a 2006 review of the contents ofOryzomys,Marcelo Weksler and colleagues listedO. antillarumas a separate species, citing Morgan,[14]and in a 2009 paper on western MexicanOryzomysCarleton and Joaquín Arroyo-Cabrales did the same.[15]

According to the classification by Carleton and Arroyo-Cabrales,Oryzomys antillarumis one of eight species in the genusOryzomys,which occurs from the eastern United States (O. palustris) into northwestern South America (O. gorgasi).[16]O. antillarumis 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.[17]Many aspects of thesystematicsof theO. couesisection remain unclear and it is likely that the current classification underestimates the true diversity of the group.[18]Oryzomyspreviously included many other species, which were progressively removed in various studies culminating in the 2006 paper by Weksler and colleagues, which excluded more than forty species from the genus.[19]All are classified in the tribeOryzomyini( "rice rats" ), a diverse assemblage of American rodents of over a hundred species,[20]and on higher taxonomic levels in the subfamilySigmodontinaeof familyCricetidae,along with hundreds of other species of mainly small rodents.[21]

Description

Oryzomys antillarumwas a medium-sized rodent, about as large asO. couesi.According to Thomas's description, the upperparts were reddish, slightly brighter on the rump and more grayish on the head. The color of the upperparts graded into that of the underparts, which were yellowish. The hairs of the underparts were grayish at the bases. The small ears were black on the outer and yellow on the inner side and the upper surfaces of the hands and feet were whitish. The tail was nearly naked and was light brownish above and lighter below.[3]Goldman wrote that the specimens in the USNM were rather more reddish, but their color may have been altered because they had been preserved in alcohol.[22]Coues had described these as rusty brown above and washed with the same color below.[8]Andrew Arata compared the USNM specimens with examples of the reddish Florida subspecies of the marsh rice rat,Oryzomys palustris natator,for Ray and found that they were more reddish than even the most strongly colored animals from Florida.[23]

Measurements ofOryzomys antillarum(in millimeters)[24]
Specimen Total length Head and body Tail Hindfoot Ear
BMNH 45.10.25.48 260 130[fn 2] 130[fn 3] 28[fn 4] 13
USNM 38299 228 120 108[fn 5] 30[fn 6] –[fn 7]
USNM 38300 253 132 121[fn 5] 30[fn 6] ?12–15[fn 7]

The skull was generally similar to that ofOryzomys couesi,[25]as were the teeth.[26]It was robust and bore well-developedsupraorbital ridges(located above the eyes) on thebraincase.Theinterparietal bone,part of the roof of the braincase, was small and narrow. The bonypalateextended beyond the third molars.[3]Thenasal bonesextended further back than thepremaxillaries,whereas these bones are usually about coterminous inO. couesi.[27]On average, theincisive foramina,which perforate the front part of the palate, were shorter than inO. couesi.[28]Thezygomatic arch(cheekbone) appears to have been better developed inO. antillarum.[26]

In the three modern and numerous cave specimens, condylobasal length (a measure of skull length) varies from 28.9 to 31.2 mm (1.14 to 1.23 in) (one modern and two cave specimens only), length of the bony palate from 13.0 to 17.8 mm (0.51 to 0.70 in), width of theinterorbital region(located between the eyes) from 4.78 to 6.33 mm (0.188 to 0.249 in), length of the incisive foramina from 5.1 to 6.6 mm (0.20 to 0.26 in), crown length of the upper molars from 4.36 to 5.20 mm (0.172 to 0.205 in), and crown length of the lower molars from 4.80 to 5.39 mm (0.189 to 0.212 in).[29]

History

Origin and subfossil records

See caption.
Upper (left) and lower (right) molars of the holotype ofOryzomys antillarum[30]

The oldest well-dated record ofOryzomys antillarumis at Drum Cave in theJacksons Bay Cavessystem, where it was found in a stratumradiocarbon datedto between 10,250 and 11,260years before presentaccording to a 2002 study.[31]It is present in several other undated sites that predate the human colonization of the island, around 1,400 years before present.[6]However, a site (Wallingford Roadside Cave) from the last interglacial, theEemian,contains only thehystricognathrodentsClidomysandGeocapromys browniand lacksOryzomys.[32]The presence of the rice rat on Jamaica before the arrival of humans disproves the hypothesis that it was introduced; instead, it must have reached the island by overwaterdispersalthrough arafting event,probably less than 125,000 years ago. During thelast glacial period,low sea levels would have exposed much land between Jamaica and Central America, substantially decreasing the water distance needed for the ancestor ofO. antillarumto arrive on the island[33]and probably influencing sea currents so that rafts of vegetation from Central America would be more likely to reach Jamaica.[34]Species ofOryzomysaresemiaquaticand closely associated with water, which may help to explain the occurrence of the genus on Jamaica.[35]The rice rat has been found in many superficial, lateHolocenecave deposits, some of which have been radiocarbon dated to within the last 1,100 years. Its remains also occur in someAmerindianarcheological sites.[6]From its common and widespread occurrence in caves, Ray suggested that the rice rat occurred in many different habitats before European contact.[26]O. antillarumwas the onlysigmodontinerodent on any of theGreater Antilles,where the rodent fauna otherwise consists solely of hystricognaths and introduced rodents.[11]

Historical records

Although there are some early historical records of the rats of Jamaica, very little is to be found in them regardingOryzomys antillarum,perhaps because the species declined rapidly following the European colonization of the island and because early authors failed to distinguish it from introduced rodents (theblack rat,Rattus rattus;brown rat,Rattus norvegicus;andhouse mouse,Mus musculus).[36]Patrick Browne,in the 1756Civil and Natural History of Jamaica,described a "House and Cane-Rat", a "Mouse", and a large "Water-Rat", which he said had been introduced to the island and become very common there.[37]

Gray-brown rat standing
Thebrown rat(Rattus norvegicus) may have contributed to the extinction ofOryzomys antillarum.

In hisHistory of Jamaica(1774),Edward Longrecognized four Jamaican rats: Browne's "water-rat", termed the "Charles-price rat", which Long regarded as identical with the Europeanwater vole(Arvicola);[38]the "black house-rat", said to have been brought from England; and two he said were indigenous. The larger of those was a grayish "cane-rat"[39]and the smaller was a reddish "field-rat" as large as the English mole (theEuropean mole,Talpa europaea).[40]Ray considered that the last may simply have been the house mouse, since the size of an English mole would be too small forOryzomys.[41]

InA Naturalist's Sojourn in Jamaica(1851),Philip Henry Gosselisted the black and brown rat and the house mouse,[42]as well as the "cane-piece rat", which he described asMus saccharivorus[43]and regarded as probably identical with Browne's "water-rat" and Long's "Charles-price rat".[44]He also mentioned the two species Long had listed as indigenous.[45]Thomas and Ray both asserted that this "cane-piece rat" was most likely a brown rat, as judged from its measurements.[46]Gosse wrote that an early explorer, Anthony Robinson, had described and pictured this species in an unpublished manuscript, on the basis of a specimen 20 inches (51 cm) long, half of which consisted of the tail.[47]Ray was unable to examine Robinson's manuscript, but suggested that Robinson's rat could not have been the brown rat, because that species did not reach the Americas until about 1800, and may instead have beenO. antillarum.[48]

Gosse had collected the British Museum specimen ofOryzomys antillarumin 1845, but may not have separated it from introduced rats found with it.[36]Coues noted that the two USNM specimens he examined were received after he had written the preceding part of his monograph;[49]later, Thomas and others wrote that these specimens were obtained around 1877,[50]but Ray asserted that they were taken before 1874.[51]No specimens have been collected since.[2]

Extinction

Oryzomys antillarumprobably became extinct about the 1870s[52]and is currently listed as such by theIUCN Red List.[2]Its disappearance is usually attributed to thesmall Indian mongoose(Urva auropunctata), which was introduced to Jamaica in 1872, and also to introducedRattusspecies.[53]Ray, on the other hand, argued that the significance of the mongoose had been overrated. Instead, he suggested thatOryzomys antillarummay have been affected by the massive environmental changes that occurred on the island after theBritish takeoverin 1655. In that period, the bulk of the island came to be used for cultivation, so that the native habitat ofOryzomyswas destroyed. Thus,Oryzomyswas reduced to competition with introduced rats in man-made habitats, to which the latter are well adapted. Perhaps, Ray wrote, the black rat may not have been able to extirpateOryzomys,but the brown rat, a later and more assertive invader, brought it to extinction.[54]Cats and dogs preying onOryzomysmay also have contributed to its demise.[6]

See also

Footnotes

  1. ^In this list of synonyms,new combinations(the first use of a given combination of a genus and species name) are indicated by a colon between the name combination and the authority which first used the combination. No colon is used when the name is entirely new.
  2. ^"Apparently stretched".[3]
  3. ^"Imperfect at tip".[3]
  4. ^Without claws.[3]
  5. ^ab"Tip broken".[24]
  6. ^abWith claws.[24]
  7. ^ab"Wrinkled".[24]

References

  1. ^Ray, 1962, plate V
  2. ^abcTurvey, S. T.; Helgen, K. (2017)."Oryzomys antillarum".IUCN Red List of Threatened Species.2017:e.T136540A22388029.doi:10.2305/IUCN.UK.2017-3.RLTS.T136540A22388029.en.
  3. ^abcdefgThomas, 1898, p. 177
  4. ^abHershkovitz, 1966, p. 736
  5. ^abHonacki et al., 1982, p. 439
  6. ^abcdeMorgan, 1993, p. 439
  7. ^Goldman, 1918, p. 44; Turvey and Helgen, 2017
  8. ^abCoues, 1877, p. 116, footnote; Thomas, 1898, p. 177
  9. ^Goldman, 1918, pp. 44–45
  10. ^Anthony, 1920, p. 166
  11. ^abAllen, 1942, p. 88
  12. ^Ray, 1962, p. 47
  13. ^Musser and Carleton, 2005, p. 1147
  14. ^Weksler et al., 2006, table 1, footnote e
  15. ^Carleton and Arroyo-Cabrales, 2009, p. 116
  16. ^Carleton and Arroyo-Cabrales, 2009, p. 106
  17. ^Carleton and Arroyo-Cabrales, 2009, p. 117
  18. ^Carleton and Arroyo-Cabrales, 2009, p. 107
  19. ^Weksler et al., 2006, table 1
  20. ^Weksler, 2006, p. 3
  21. ^Musser and Carleton, 2005
  22. ^Goldman, 1918, p. 44
  23. ^Ray, 1962, p. 44
  24. ^abcdRay, 1962, table 3
  25. ^Goldman, 1918, p. 44; Ray, 1962, p. 44
  26. ^abcRay, 1962, p. 46
  27. ^Ray, 1962, p. 45
  28. ^Ray, 1962, pp. 45–46
  29. ^Ray, 1962, table 4
  30. ^Ray, 1962, plate VI
  31. ^McFarlane et al., 2002, p. 122
  32. ^Fincham et al., 2000, p. 50
  33. ^Morgan, 1993, p. 439; Fincham et al., 2000, p. 50; McFarlane et al., 2000, p. 122; Ray, 1962, p. 176
  34. ^Ray, 1962, p. 174
  35. ^Carleton and Arroyo-Cabrales, 2009, p. 114
  36. ^abRay, 1962, p. 31
  37. ^Browne, 1756, pp. 484–485
  38. ^Long, 1774, p. 899
  39. ^Long, 1774, p. 900
  40. ^Long, 1774, p. 901
  41. ^Ray, 1962, p. 32
  42. ^Gosse, 1851, p. 443
  43. ^Gosse, 1851, p. 444, footnote
  44. ^Gosse, 1851, p. 449
  45. ^Gosse, 1851, pp. 448–449
  46. ^Thomas, 1898, p. 177; Ray, 1962, p. 32
  47. ^Gosse, 1851, p. 445
  48. ^Ray, 1962, pp. 32–33
  49. ^Coues, 1877, p. 116, footnote
  50. ^Thomas, 1898, p. 177; Goldman, 1918, p. 45; Allen, 1942, p. 88; Morgan, 1993, p. 439; Turvey and Helgen, 2017
  51. ^Ray, 1962, p. 34
  52. ^Ray, 1962, p. 34; Allen, 1942, p. 87
  53. ^Turvey and Helgen, 2017; Allen, 1942, pp. 87–88; Morgan, 1993, p. 439; Ray, 1962, p. 34
  54. ^Ray, 1962, pp. 33–34

Literature cited

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