Interesting approach and personally timely as I just happen to really be into Triassic biogeography at the moment; however, I think this study suffers somewhat from the usual culprits, lack of taxon sampling and unresolved taxonomic issues (weak primary data). For example, basal phytosaurs are completely left out which have an early and widespread appearance in the Late Triassic. These are extremely important as they are found in Europe, North America, North Africa, and interestingly in India. Including these would have changed several of the paper's conclusions. Likewise, the aetosaur Calyptosuchus (Stagonolepis) wellesi is purposefully left out as is Coahomasuchus, which are two important datapoints for aetosaurs in the Ischigualastian of North America. I wish I had been contacted regarding this study as I would have gladly suggested some less "key" aetosaur taxa to leave out if better resolution was needed for the basal aetosaurines. It is also not entirely clear if the Ischigulastian and Coloradian are applicable outside of South America. It appears that they are presented as equivalent to the Otischalkian + Adamanian and Revueltian + Apachean of North America. This was first put forth by Max Langer in 2005 and has some support, but needs further testing, especially regarding the relationships of all of the Stagonolepis-like aetosaurs, the lack of good phytosaur material in South America, and lack of good (or any) comparable rhynchosaur, cynodont, and sauropodomorph material in North America.
On a side note, it was nice to see Heliocanthus used in there.
Ezcurra, M. D. 2010. Biogeography of Triassic tetrapods: evidence for provincialism and driven sympatric cladogenesis in the early evolution of modern tetrapod lineages. Proceedings of the Royal Society B, doi:10.1098/rspb.2010.0508 Published online.
Abstract - Triassic tetrapods are of key importance in understanding their evolutionary history, because several tetrapod clades, including most of their modern lineages, first appeared or experienced their initial evolutionary radiation during this Period. In order to test previous palaeobiogeographical hypotheses of Triassic tetrapod faunas, tree reconciliation analyses (TRA) were performed with the aim of recovering biogeographical patterns based on phylogenetic signals provided by a composite tree of Middle and Late Triassic tetrapods. The TRA found significant evidence for the presence of different palaeobiogeographical patterns during the analysed time spans. First, a Pangaean distribution is observed during the Middle Triassic, in which several cosmopolitan tetrapod groups are found. During the early Late Triassic a strongly palaeolatitudinally influenced pattern is recovered, with some tetrapod lineages restricted to palaeolatitudinal belts. During the latest Triassic, Gondwanan territories were more closely related to each other than to Laurasian ones, with a distinct tetrapod fauna at low palaeolatitudes. Finally, more than 75 per cent of the cladogenetic events recorded in the tetrapod phylogeny occurred as sympatric splits or within-area vicariance, indicating that evolutionary processes at the regional level were the main drivers in the radiation of Middle and Late Triassic tetrapods and the early evolution of several modern tetrapod lineages.
Does expression of the toxA operon depend on ToxT as well as ToxA?
2 days ago in RRResearch