Taxonomy, phylogeny, and diversity of the extinct Lesser Antillean rice rats (Sigmodontinae: Oryzomyini), with description of a new genus and species

Abstract

Rice rats (Sigmodontinae: Oryzomyini) are abundant in the Late Quaternary fossil record and in Holocene pre-Columbian archaeological middens across the Lesser Antilles. All of these rice rats are now extinct, and their regional diversity and systematics remain extremely poorly understood. We redescribe all of the region's rice rat taxa known from adequate diagnostic material (Megalomys desmarestii, Megalomys luciae, and Oligoryzomys victus), and describe a new genus and species, Pennatomys nivalis gen. et sp. nov., from archaeological sites on St. Eustatius, St. Kitts, and Nevis, which formed a single larger island during Quaternary low sea-level stands. Cladistic analysis supports the inclusion of O. victus within Oligoryzomys, and identifies Megalomys as a sister group of the large-bodied genera Sigmodontomys or Sigmodontomys + Nectomys, suggesting that large body size in Megalomys represents phyletic gigantism rather than 'island gigantism'. Megalomys and Pennatomys belong to an oryzomyine clade that has undergone remarkable radiation throughout the oceanic and continental-shelf islands of the Neotropical region, but these genera do not represent a monophyletic group within the Nectomys subclade, indicating multiple over-water colonization events of the Lesser Antillean island chain. Although Lesser Antillean rice rats were heavily exploited by prehistoric Amerindians, it is likely that most or all of these taxa survived until European arrival in the region.

Systematics and distribution of the giant fossil barn owls of the West Indies (Aves: Strigiformes: Tytonidae)

“…In the Lesser Antilles it is known so far only from Barbuda (T. "neddi") where its main prey would have been the extinct giant rice rat Megalomys audreyae Hopwood. Several species of giant rice rats (Sigmodontinae: Orizomyini) are known from fossil and archeological deposits throughout the Lesser Antilles, including Barbados, and they were also known historically from Martinique and St. Lucia, although there is as yet no evidence of rice rats on Dominica (Turvey et al 2010(Turvey et al , 2012. The islands from St. Vincent through Grenada are exceptional as much smaller rice rats (Oligoryzomys Bangs) once occurred there along with the diminutive Lesser Antillean Barn Owl Tyto insularis Pelzeln (Olson & Suárez unpub.…”

Evolutionary studies in South American marsh rats (Rodentia: <em>Holochilus</em>)

“…The relationship among these three genera is also variable in more recent studies TURVEY et al, 2010;PERCEQUILLO;COSTA, 2011;). …”

“…Phylogenetic studies on the tribe Oryzomyini expanded considerably over recent years TURVEY et al, 2010;PERCEQUILLO;COSTA, 2011;. Although its composition, which was originally defined and diagnosed by , is often corroborated by phylogenetic studies (STEPPAN, 1995;D'ELÍA et al, 2007;PERCEQUILLO;COSTA, 2011;, the relationships among the four major Oryzomyini clades, A, B, C and D (see and among the genera within these clades are not clear.…”

“…Although currently allocated unambiguously in the tribe Oryzomyini TURVEY et al, 2010;PERCEQUILLO;COSTA, 2011; in the recent past (REIG, 1986) Another previously constructed phylogenetic hypothesis for the Oryzomyini tribe (CARLETON; OLSON, 1999) shows the genus Noronhomys (now extinct) as sister group of Holochilus, and the genus Lundomys more associated with them than with Pseudoryzomys. In the phylogenetic analysis conducted by based on morphological data, two equally parsimonious trees were obtained, with Pseudoryzomys or Lundomys also appearing as sister group of Holochilus.…”

“…Phylogenetic studies on the tribe Oryzomyini expanded considerably over recent years (Weksler, 2015). Although its composition, which was originally defined and diagnosed by , is often corroborated by more comprehensive phylogenetic studies (Steppan, 1995;D'Elía et al 2007;Turvey et al 2010;Percequillo et al 2011;, the relationships among the four major Oryzomyini clades, A, B, C and D (see and among the genera within these clades are still not clear Percequillo et al 2011;. Additionally, the relationships among taxa of species group were not adequately addressed and are uncertain as well as the time and diversification mechanisms are inconclusive for most genera and species (Steppan, 1995;Parada et al 2015).…”