page_title: Megalomys audreyae
section_title: Description
hierarchical_section_title: Megalomys audreyae / Description
caption_attribution_description: English: Jaw of the holotype of Megalomys audreyae (British Museum, Geology Department, nr. 7406a). Occlusal view of molar row.
context_page_description: Megalomys audreyae, known as the Barbudan muskrat or the Barbuda giant rice rat, is an extinct oryzomyine rodent from Barbuda in the Lesser Antilles. Described on the basis of a single mandible with the first molar missing and an isolated upper incisor, both of uncertain but Quaternary age, it is one of the smaller members of the genus Megalomys. Little is known about the animal, and its provenance and distinction from "Ekbletomys hypenemus", an even larger extinct oryzomyine that also occurred on Barbuda, have been called into question. The toothrow in the lower jaw has a length of 8.7 mm at the alveoli. The third molar is relatively narrow and both the second and third molars have a wide valley between their outer cusps.
context_section_description: The only remains of Megalomys audreyae that have been described in the literature are the original two specimens Gregory found, a left upper incisor and a left mandible (lower jaw). The upper incisor is not grooved and its diameter has a length of 2.6 mm and width of 1.5 mm, but exhibits no other significant characters.
  The mandible, which is severely damaged and lacks the condyloid, coronoid, and angular processes at the back of the bone, contains the second and third molar and part of the lower incisor, but the first molar is missing. The capsular process of the lower incisor, a slight raising of the mandibular bone at the back end of the incisor, is small. The preserved alveoli, the impressions left by the roots, show that the first molar was supported by large roots at the front and back and a smaller root in between these. The second molar is about square and shows the four main cusps commonly present in rodents: the protoconid, metaconid, hypoconid, and entoconid. A strongly developed mesolophid (a crest) is also present, as in most oryzomyines. The main valley between the cusps, the hypoflexid, is broad and V-shaped. The third molar is as long as the second, but it is narrower and the entoconid is poorly developed. Again, the hypoflexid is broad and V-shaped. The length of the toothrow at the alveoli is 8.7 mm. The length of the second molar is 2.5 mm and the width is 2.2 mm. The third molar has a length of 2.5 mm and width of 1.8 mm.
  When Clayton Ray described "Ekbletomys hypenemus" on the basis of abundant skeletal remains from both Barbuda and Antigua, he carefully distinguished it from M. audreyae, the only other native rodent recorded from those islands. M. audreyae is much smaller than "Ekbletomys"; for example, 72 specimens of the latter had the alveolar length of the lower molars ranging from 10.3 to 12.6 mm (mean 11.6 mm, standard deviation 0.49 mm; compare 8.7 mm for M. audreyae). In addition, the V-shaped hypoflexids and narrow third molar of M. audreyae contrast with the narrow, parallel-sided hypoflexids and broad third molar of "Ekbletomys". These characters, and others observable in species of Megalomys represented by more complete material, convinced Ray that M. audreyae and "Ekbletomys" are not only distinct species, but indeed share no close relationship. Instead, he proposed that the combination of large size, occurrence in the Lesser Antilles, and similarity in molar morphology indicated a relationship between M. audreyae and other species of Megalomys, and he suggested that the similarly sized M. curazensis from Curaçao, off Venezuela, may be most closely related to M. audreyae.
caption: Lower toothrow in the mandible: second and third molar, with the first molar missing[1]
exif: {}