Abstract
Today, Diploglossine lizards (Anguidae) are common on the Greater Antillean Islands (West Indies), where they are represented by many endemic species. However these lizards are very rare on the Lesser Antillean Islands, where they are only represented by a single species, the Montserrat galliwasp (Diploglossus montisserrati). Here, we show that diploglossine lizards were present in the past on other Lesser Antillean islands, by reporting the discovery of Anguidae fossil remains in two Amerindian archaeological deposits and in a modern deposit. These remains are compared to skeletons of extant diploglossine lizards, including D. montisserrati, using X-ray microtomography of the type specimen of this critically endangered lizard. We also conducted a histological study of the osteoderms in order to estimate the putative age of the specimen. Our results show that the fossil specimens correspond to a member of the Diploglossus genus presenting strong similarities, but also minor morphological differences with D. montisserrati, although we postulate that these differences are not sufficient to warrant the description of a new species. These specimens, identified as Diploglossus sp., provide a new comparison point for the study of fossil diploglossine lizards and reflect the historical 17th century mentions of anguid lizards, which had not been observed since.
Highlights
Problems raise the question of the possible past occurrence of extinct diploglossine lizards elsewhere on the Lesser Antillean Islands, other than Montserrat, and the question of the chronology and the reasons for the extinction of these lizards
The presence of a member of the Diploglossus genus in Guadeloupe raises the number of Lesser Antillean Islands presenting evidence of present or past occurrences of Diploglossus to three (Montserrat, Basse-Terre and Grande-Terre)
On account of their morphological similarity, the Guadeloupe Island and Montserrat galliwasps may derive from the same colonization event by over-water dispersal, which would be younger than the beginning of the geological formation of Basse-Terre 2.79 My ago[31]
Summary
A 2 mm mesh screen was used to collect osteological remains from the archaeological sediments during the excavations. The 174 remains collected from the Saint-Rose la Ramée site come from four different stratigraphic units (US 1956; US 2043; US 2058 and US 1530), located in four different loci of the site. Three of these units were radiocarbon dated at the Beta Analytic Radiocarbon Dating Laboratory (Miami, U.S.A.): 1090 +/−40 BP (Cal. 880 to 1020 AD) for US 1956 and 2043 In addition to the examination of the external morphology, two fossil osteoderms corresponding to the two different morphotypes highlighted by our morphological observations were prepared in order to observe their histological organization They were embedded in polyester resin, sectioned along their transverse axes, mounted on a glass slide, and polished to obtain thin sections with a thickness of about 100 μm. Measurements were taken on bones using a digital dial caliper [IP 67 (Mitutoyo Corporation, Japan)] and using the AVIZO 6.1 3D measurement tool on the X-ray microtomography
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