Thursday, August 11, 2016


If you're into dinosaurs and paleontology, you'll doubtless already know all about Kulindadromeus zabaikalicus, a recently (2014) described primitive Neornithischian from Siberian fossil sites in the Ukureskaya formation.  I've been trying to narrow down exactly when this formation tracks to, but so far all that I've been able to find is that it's somewhere between the Bajocian and the Tithonian; a period of almost 20 million years that covers 6 ages of the Middle and Late Jurassic; although at least one source states that the find is "probably" from the older portion of that rather large window.  The dating of the formation in general is poorly understood, but as a type comparison, Kulindadromeus comes out cladistically as extremely closely related to other basal Neornithischians such as Othnielosaurus from the late Jurassic Morrison Formation of western USA, or Hexinlusaurus of Middle Jurassic China.  This would place it as a very primitive member of the odds and ends group of what are usually classified as hypsilophodontids; some studies even have these primitive members outside of Ornithopoda altogether, and even outside of Cerapoda.

In any case, it's about as far as can be from the bird-ancestry therapod lineages where most of the feathered dinosaurs have so far been discovered.  When there were suggestive discoveries such as possible feather-like plumes on Tianyulong or Psittacosaurus, I was saying back in 2009 that I'd have bet a "hypsilophodontid" with feathers would be the clincher, assuming one turned up that was well and truly feathery.  Kulindadromeus is that specimen.  The following image carefully crafts what it was discovered with on integument impressions.

Anyway, as I said back in 2009 while describing Tianyulong, the implications of finding feathered Ornithischians that have homologous integument to therapods is, of course, that it means such a feature had to have been ancestral to all dinosaurs.  Boom.  Most specialists also recognize that these type of proto-feathers appear to be homologous with pycnofibers on pterosaurs, meaning that it is actually ancestral to all Ornithodirans.  At least.

Of course, I've also talked about the beta keratin genomic studies of alligator scales that suggest that they may also be homologous as a structure (even if they are not in appearance).  All it would take now is the discovery of a protofeather integument to be found on a small, gracile suchid of some sort, like Hesperosuchus or Terrestrisuchus to push what this tantalizing hint may be pointing at: that the evolution of protofeathers may go back all the way to the base of Archosauria.  At least.  Given other anatomic details that suggest warm-bloodedness may have been common in Suchia prior to the actual crocodiles and co. losing it so they could be better semi-aquatic ambush predators, that's not even very far-fetched really.

But let's not get too far ahead of ourselves quite yet...

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