Few days back, we wrote about the genome paper of western painted turtle. We were also surprised, because -
We also noticed that the authors did very comprehensive work on genome analysis, and were surprised that the paper got published in Genome Biology unlike many other comparable genome papers published over the last few months.
Our question to the authors went unanswered, but maybe now we have one. Turtle is one lucky animal to have so many genomes published within a month.
The unique anatomical features of turtles have raised unanswered questions about the origin of their unique body plan. We generated and analyzed draft genomes of the soft-shell turtle (Pelodiscus sinensis) and the green sea turtle (Chelonia mydas); our results indicated the close relationship of the turtles to the bird-crocodilian lineage, from which they split ~267.9248.3 million years ago (Upper Permian to Triassic). We also found extensive expansion of olfactory receptor genes in these turtles. Embryonic gene expression analysis identified an hourglass-like divergence of turtle and chicken embryogenesis, with maximal conservation around the vertebrate phylotypic period, rather than at later stages that show the amniote-common pattern. Wnt5a expression was found in the growth zone of the dorsal shell, supporting the possible co-option of limb-associated Wnt signaling in the acquisition of this turtle-specific novelty. Our results suggest that turtle evolution was accompanied by an unexpectedly conservative vertebrate phylotypic period, followed by turtle-specific repatterning of development to yield the novel structure of the shell.
If we get time, we will do a comparison of two genome papers and write a separate blog post for our readers.