The Ypresian Cambay Formation at Vastan Mine in Gujarat, western India, has yielded a rich herpetological fauna including snakes, lizards and amphibians, but strangely, lizards are only represented by Acrodonta. Here we describe the acrodontan assemblage based on numerous, diverse and well-preserved dentaries, premaxillae, and maxillae. Among the five taxa described one new genus and species characterised by a short splenial represents the youngest occurrence of the extinct family Priscagamidae. The other four taxa belong to the extant family Agamidae. Two of them previously known, Vastanagama susanae and Tinosaurus indicus, are here revised. The two other taxa are new. The first one, Suratagama neeraae gen. and sp. nov., is characterised by the presence of six small pleurodont teeth with a nearly cylindrical shaft and an obtusely pointed apex. The second one, Indiagama gujarata gen. and sp. nov., has rectangular teeth in lateral view, unicuspid crowns forming a nearly horizontal cutting edge, and wear facets on both the lingual and labial sides of the dentary. Our results confirm that Acrodonta is the only lizard group present in Vastan, whereas many other groups are already present from the beginning of the Early Eocene on the other continents. The diversity of the agamids in Vastan and the absence of non-acrodontan lizard in India tentatively support the Out-of-India hypothesis for agamids.
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Background Hyperdiverse mtDNA with more than 5% of variable synonymous nucleotide sites can lead to erroneous interpretations of population genetic differentiation patterns and parameters (φST, DEST). We illustrate this by using hyperdiverse mtDNA markers to infer population genetic differentiation and connectivity in Melarhaphe neritoides, a NE Atlantic (NEA) gastropod with a high dispersal potential. We also provide a recent literature example of how mtDNA hyperdiversity may have misguided the interpretation of genetic connectivity in the crab Opecarcinus hypostegus. Results mtDNA variation surveyed throughout the NEA showed that nearly all M. neritoides specimens had haplotypes private to populations, suggesting at first glance a lack of gene flow and thus a strong population genetic differentiation. Yet, the bush-like haplotype network, though visually misleading, showed no signs of phylogeographic or other haplotype structuring. Coalescent-based gene flow estimates were high throughout the NEA, irrespective of whether or not mtDNA hyperdiversity was reduced by removing hypervariable sites. Conclusions Melarhaphe neritoides seems to be panmictic over the entire NEA, which is consistent with its long-lived pelagic larval stage. With hyperdiverse mtDNA, the apparent lack of shared haplotypes among populations does not necessarily reflect a lack of gene flow and/or population genetic differentiation by fixation of alternative haplotypes (DEST ≈ 1 does not a fortiori imply φST ≈ 1), but may be due to (1) a too low sampling effort to detect shared haplotypes and/or (2) a very high mutation rate that may conceal the signal of gene flow. Hyperdiverse mtDNA can be used to assess connectivity by coalescent-based methods. Yet, the combined use of φST and DEST can provide a reasonable inference of connectivity patterns from hyperdiverse mtDNA, too.
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RBINS Staff Publications 2019
