Notes on the external morphology, ecology, and origin ofMegalomys desmarestii(Sigmodontinae, Cricetidae, Rodentia), the extinct giant rat of Martinique Island, Lesser Antilles

Abstract

The giant rat of Martinique Island, Megalomys desmarestii (Fischer, 1829) became extinct at the end of the 19th or the very beginning of the 20th century. Little is known about its habits. The goal of this research was to reconstruct its ecology using the external and craniodental morphological characters of available museum specimens. On the basis of ecomorphological analysis some suggestions are made about the locomotor abilities, ecological strategies, adaptive evolution, and origin of this rodent. It is proposed that M. desmarestii foraged mostly on the ground and sheltered in burrows. Its main food was seeds and fruits, including nuts. It was crepuscular rather than strictly nocturnal or diurnal. The general trends of its adaptive evolution were: (1) increasing body size, (2) transition from an arboreal to a terrestrial/subterranean way of life, and (3) adaptation to eating hard-covered fruits. Thus, the ancestor of M. desmarestii was probably smaller and had arboreal or semiarboreal habits. The granulated structure of the soles of M. desmarestii's feet supports a close relationship with Nectomys.

Isotopic ecology and extirpation chronology of the extinct Lesser Antillean native rodent Antillomys rayi Brace et al. (2015)

“…Taken together, isotopic values reveal A. rayi to have had a rather high ecological valence, inhabiting diverse environments of Guadeloupe from the semi-deciduous dry forest to the more humid contexts or rain forests. This species did not permanently and exclusively occupy the swamp forest, which is inconsistent with hypotheses concerning a potential semi-aquatic adaptation of Lesser Antillean native rodents (e.g., Miljutin, 2010). Nonetheless, this hypothesised semi-aquatic adaptation of Lesser Antillean native rodents would be shared by species from the genera Megalomys and Pennatomys (Clade D of Weksler et al (2006) and Turvey et al (2010)) whereas A. rayi represents a distinct monophyletic clade (Brace et al, 2015).…”

A new species of Mindomys (Rodentia, Cricetidae) with remarks on external traits as indicators of arboreality in sigmodontine rodents

“…Probably the manus is one of the less explored complex anatomical systems in sigmodontines, in which arboreality is decidedly expressed (Camargo et al 2012;Nations et al 2019). Among the scarce assessments of sigmodontine manus are the description provided by Luna and Patterson (2003) for the arboreal Rhagomys longilingua and the approach of Miljutin (2010) on Megalomys desmarestii, favoring a cursorial life-mode for this giant oryzomyine (contra Hershkovitz 1969:42). M. kutuku has a broad manus with thick digits.…”

“…If the morphology of the manus is assessed directly on dry skins, without moistening (contrary to what P. Hershkovitz regularly did), almost nothing can be surmised from the palmar anatomy beyond sole condition. Even when working with fluid-preserved specimens, or more rarely with recently dead animals, manus received little attention, and few reports recorded their main features (e.g., Hershkovitz 1966Hershkovitz , 1994Hershkovitz , 1998Hinojosa et al 1987;Miljutin 2010;Pardiñas et al 2016).…”

Archaeobiogeography of extinct rice rats (Oryzomyini) in the Lesser Antilles during the Ceramic Age (500 BCE–1500 CE)

“…Kadmon and Allouche, 2007), the current systematic and taxonomy of the group is still not fully established. Three genera are currently recognized in the Lesser Antilles archipelago (Brace et al, 2015; Machado et al, 2014) (Figure 1): Pennatomys has been described in the North of the archipelago (Saint-Eustatius, Saint-Kitts, and Nevis) (Turvey et al, 2010), Megalomys (Trouessart, 1885) in the South (Martinique, Saint-Lucia, and Barbados) (Forsyth Major, 1901; Friant, 1941; Miljutin, 2010), and Antillomys (Brace et al, 2015) in the center (Guadeloupe, Antigua, and Barbuda) (Barbotin, 1970; Brace et al, 2015; Hopwood, 1926; Pregill et al, 1994). These three genera are supported by high genetic divergence (560 bp of the Cytochrome b gene) and according to ancient genetic data Megalomys and Pennatomys are sister clades, only distantly related to the genus Antillomys (Brace et al, 2015).…”