A new paper
claims turtles are closer to archosaurs based on miRNA molecules.
From the abstract:
“Understanding the phylogenetic position of crown turtles (Testudines) among amniotes has been a source of particular contention. Recentmorphological analyses suggest that turtles are sister to all other reptiles, whereas the vast majority of gene sequence analyses support turtles as being inside Diapsida, and usually as sister to crown Archosauria (birds and crocodilians). Previously, a study using miRNAs (miRNAs) placed turtles inside diapsids, but as sister to lepidosaurs (lizards and Sphenodon) rather than archosaurs. Here, we test this hypothesis with an expanded miRNA presence/absence dataset, and employ more rigorous criteria for miRNA annotation. Significantly, we find no support for a turtle + lepidosaur sister-relationship; instead, we recover strong support for turtles sharing a more recent common ancestor with archosaurs. We further test this result by analyzing a super-alignment of precursor miRNA sequences for every miRNA inferred to have been present in the most recent common ancestor of tetrapods. This analysis yields a topology that is fully congruent with our presence/absence analysis; our results are therefore in accordance with most gene sequence studies, providing strong, consilient molecular evidence from diverse independent datasets regarding the phylogenetic position of turtles.”
Turtles are diapsids?
Then take the next step: go find turtles among the diapsids. Show us the morphological sisters. Show us the turtle-like traits in one or more diapsids. If you can’t, then go back to the drawing board. And for that matter, which diapsids? There are two convergent diapsid lineages, because the entire Reptilia is diphyletic.
Turtles are closer to archosaurs?
Then take the next step: go find turtles among the archosaurs. Show us the morphological sisters. Show us the turtle-like traits in one or more archosaurs. If you can’t, then go back to the drawing board.
Something must be off withe the miRNA.
The large reptile tree finds maximum parsimony with millerettids and pareiasaurs, and among them, an ignored taxon, Stephanospondylus. The Field et al. (2014) tree (Fig. 1) was unable to resolve turtles from chickens from alligators. That’s an embarrassing result that tells me there’s a red flag here. Perhaps the secondary losses that are noted in lepidosaurs and mammals also have story to tell. A stronger tree would have had fewer secondary losses. What that tells me is what turtles and archosaurs share may be plesiomorphic genes secondarily lost in lepidosaurs and mammals.
I know nothing about miRNA or cellular biochemistry. But I can read a chart. If I need a lesson here, please provide it. This can be a discussion, not a lecture.
Field DJ, Gauthier JA, King BL, Pisani D, Lyson TR, and Peterson KJ 2014. Toward consilience in reptile phylogeny: miRNAs support an archosaur, not lepidosaur, affinity for turtles. Evolution & Development (advance online publication)
DOI: 10.1111/ede.12081 http://onlinelibrary.wiley.com/doi/10.1111/ede.12081/abstract