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Topics - DaveGodfrey

1
Science / New fossil caecilians!
Just in time for Bili's birthday, although I should have posted it yesterday.

So maybe Lissamphibia is polyphyletic after all. Or at least crown Lissamphibia has to include a whole bunch of other stuff if you want to keep it monophyletic. Maybe. I'd be interested in any criticisms anyone has on that.

Stem caecilian from the Triassic of Colorado sheds light on the origins of Lissamphibia Jason D. Pardo, Bryan J. Small,and Adam K. Huttenlocker (2017) PNAS, doi:10.1073/pnas.1706752114

Quote
The origin of the limbless caecilians remains a lasting question in vertebrate evolution. Molecular phylogenies and morphology support that caecilians are the sister taxon of batrachians (frogs and salamanders), from which they diverged no later than the early Permian. Although recent efforts have discovered new, early members of the batrachian lineage, the record of pre-Cretaceous caecilians is limited to a single species, Eocaecilia micropodia. The position of Eocaecilia within tetrapod phylogeny is controversial, as it already acquired the specialized morphology that characterizes modern caecilians by the Jurassic. Here, we report on a small amphibian from the Upper Triassic of Colorado, United States, with a mélange of caecilian synapomorphies and general lissamphibian plesiomorphies. We evaluated its relationships by designing an inclusive phylogenetic analysis that broadly incorporates definitive members of the modern lissamphibian orders and a diversity of extinct temnospondyl amphibians, including stereospondyls. Our results place the taxon confidently within lissamphibians but demonstrate that the diversity of Permian and Triassic stereospondyls also falls within this group. This hypothesis of caecilian origins closes a substantial morphologic and temporal gap and explains the appeal of morphology-based polyphyly hypotheses for the origins of Lissamphibia while reconciling molecular support for the group's monophyly. Stem caecilian morphology reveals a previously unrecognized stepwise acquisition of typical caecilian cranial apomorphies during the Triassic. A major implication is that many Paleozoic total group lissamphibians (i.e., higher temnospondyls, including the stereospondyl subclade) fall within crown Lissamphibia, which must have originated before 315 million years ago.
2
 :stareicide: I've had to update to windows 10 on my phone as messenger stopped working with the new changes to the Facebook app. And now TR looks like this and I can't work out why. It doesn't seem to be the text size settings in "Edge" and it doesn't seem to be the settings for the whole phone either.

I are confused.
3
Quote
The biggest family tree of dinosaurs mapped out so far suggests that the origin of dinosaurs may have been 20 million years earlier than previously thought - and could have meant they survived the mass extinction widely thought to have wiped them out.

]They can't even English properly.

Uh? So dinosaurs were thought to have died out before they evolved? You wot?

Anyway, for those of you who are interested in what the Mail put through the chipper the actual paper is here.
4
Not sure how long they'll be available for, but David Attenborough's got another 2-part Aquatic Ape Hypothesis radio show as a follow-up to the one he did 12 years ago.
5
Science / Rotting penis worms in buckets.
Sansom, R., 2016, Preservation and phylogeny of Cambrian ecdysozoans tested by experimental decay of Priapulus  Scientific Reports 6, Article number: 32817.

Quote
The exceptionally preserved Cambrian fossil record provides unique insight into the early evolutionary history of animals. Understanding of the mechanisms of exceptional soft tissue preservation frames all interpretations of the fauna and its evolutionary significance. This is especially true for recent interpretations of preserved nervous tissues in fossil ecdysozoans. However, models of soft tissue preservation lack empirical support from actualistic studies. Here experimental decay of the priapulid Priapulus reveal consistent bias towards rapid loss of internal non-cuticular anatomy compared with recalcitrant cuticular anatomy. This is consistent with models of Burgess Shale-type preservation and indicates that internal tissues are unlikely to be preserved with fidelity if organically preserved. This pattern, along with extreme body margin distortion, is consistent with onychophoran decay, and is therefore resolved as general for early ecdysozoans. Application of these patterns to phylogenetic data finds scalidophoran taxa to be very sensitive to taphonomically informed character coding, but not panarthropodan taxa. Priapulid decay also have unexpected relevance for interpretation of myomeres in fossil chordates. The decay data presented serve not only as a test of models of preservation but also a framework with which to interpret ecdysozoan fossil anatomies, and the subsequent evolutionary inferences drawn from them.

6
Science / Palaeocast on the Blue Beach tetrapod fauna.
Palaeocast have an interview with someone or other talking about a locality in Nova Scotia that helps fill in the hole in the vertebrate record called Romer's Gap.

(Background reading can be found here).