Gorg gokge datings

Using RAG1 sequence data from 76 extant taxa and the new fossil specimens two of several calibrations, we estimate that the most recent common ancestor of Lepidosauria lived at least 242 Mya (238–249.5), and crown-group Squamata originated around 193 Mya (176–213).

A Early/Middle Triassic date for the origin of Lepidosauria disagrees with previous estimates deep within the Permian and suggests the group evolved as part of the faunal recovery after the end-Permain mass extinction as the climate became more humid.

However, we chose the less complex model GTR G, because although GTR G I would improve the model’s fit to the data it also seems to cause convergence difficulties rather than improving the phylogenetic reconstruction and dating.

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However, molecular age estimates for Lepidosauria have been problematic; dates for the most recent common ancestor of all lepidosaurs range between approximately 226 and 289 Mya whereas estimates for crown-group Squamata (lizards and snakes) vary more dramatically: 179 to 294 Mya.

This uncertainty restricts inferences regarding the patterns of diversification and evolution of Lepidosauria as a whole.

All characters were equally weighted and unordered.

In the few cases where taxa exhibited multiple states for the same character, the state was treated as uncertain (by default, PAUP* treats uncertain multistate characters as polymorphism, whilst Mr Bayes treats them as total uncertainty, which could potentially lead to larger differences in inferred trees if the matrix contains many multiple state characters). Bootstrap support for clades found by PAUP* were calculated from 1000 replicates of heuristic search using TBR and random addition.

The Vellberg fossil locality is expected to become an important resource for providing a more balanced picture of the Triassic and for bridging gaps in the fossil record of several other major vertebrate groups. An accurate estimate for when this clade originated is crucial for appreciating the ecological context in which it first evolved in addition to its subsequent diversification.

Currently, the oldest fossil records of Lepidosauria are rhynchocephalian and Late Triassic in age (228–235 Mya, Carnian): ].Our origin time for crown-group Squamata coincides with shifts towards warmer climates and dramatic changes in fauna and flora.Most major subclades within Squamata originated in the Cretaceous postdating major continental fragmentation.The new fossil material described here comprises two partial dentaries: a right bone exposed in lateral view bearing six teeth (SMNS 91060) and a left bone exposed in lingual view bearing two large teeth posteriorly and at least seven distinctly smaller teeth anteriorly (SMNS 91061).The locality preserves deposits from a freshwater lake a few kilometers in diameter.Despite the number of characters used in previous analyses, this matrix should be treated as new because several characters have been modified to accommodate both rhynchocephalians and stem group lepidosauromorphs.

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