Saturday, December 15, 2012

The Field Guide Rejects: Yixianosaurus

As announced in a few previous posts, Facebook, Twitter, the face of the moon and Geocities probably, my new book A Field Guide to Mesozoic Birds and Other Winged Dinosaurs is now available! The dead tree version can be had through Amazon or CreateSpace and a PDF version is also available for people who prefer to keep their library online/on disk via Lulu (for those of you reading this via RSS, click through to the Web article for handy links on the right side of the post!).

In the interests of continued, shameless self-promotion, I thought I'd do a few blog posts highlighting a bit of the 'making of' the book; in this case, showcasing something that didn't quite make the cut and why.

The first thing I did when switching gears from a guide to the complete ecology of a specific geologic formation to a broad overview of all known Mesozoic birds was decide which species to draw and which to relegate to the appendix. My original criterion, as suggested by John Conway (of All Yesterdays fame) was to include all "reconstructible" aviremigians. I suspect that by "reconstructible" he probably meant "known from a reasonably complete skeleton" but, stickler for completion that I am, I immediately broadened this to mean "anything that could be reasonably drawn based on phylogenetic bracketing." Perhaps understandably, this quickly got out of hand, forcing me to narrow the list down a bit, but not before I'd already painted (I kid you not) Dromaeosauroides and Troodon asiamericanus (the former complete with a tiny inset showing the single known tooth). While I liked the idea of including such never-before illustrated and highly speculative restorations, I thought that the spirit of the book demanded that I include mainly species that would have externally-visible distinguishing features. While there are still a few exceptions included, that is the criteria that produced the final book.

One interesting situation was the few species which did have some externally visible features but are otherwise so phylogenetically ambiguous that most of the reconstruction would be pure fantasy. An example is shown above: Yixianosaurus longimanus. The fact is, despite have a complete forelimb complete with vaned feathers, we don't really have any idea what kind of aviremigian Yixianosaurus is. It's sort of the Deinocheirus of the 21st century. I had restored it basically as I'd imagine a very primitive oviraptorosaur would look, sort of like a cross between Ornitholestes, Falcarius, and Protarchaeopteryx, and it was originally included among the basal caenagnathiformes for lack of a better spot in the book. I'd probably have kept it in if we had complete wing feathers--that would be useful to diagram, at least for artists. But even their length is a guess. So, despite being possibly the most basal known member of the Aviremigia, I had to give this guy the axe.


  1. Looking forward to more of these making-of posts. I got a hearty chuckle out of reading that you'd originally restored Dromaeosauroides.

  2. What do the arrows indicate on the life restoration?

    1. They remind me of the arrows Roger Tory Peterson used in his illustrations to point out the most distinctive features to look at in modern birds. And as someone who learned how to identify birds with a Peterson field guide, that made me geek out.

    2. @Trish Yup, that's exactly the inspiration for the little arrows. In the case of Yixianosaurus, they're pointing out the large, recurved manual claws and the narrow vaned remiges, which are essentially the only distinguishing characters which would be externally visible given what we have of the skeleton.

  3. Second Alb's notion, more of these would be awesome. Especially if you did some of the other Hell Creek taxa. That'd make me a happy camper :D

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  5. I love the enigmatic maniraptorians like Yixianosaurus. I think that its cladistic position might be between Scansoriopterygidae and Eosinopteryx, but is to say that it's a vey unstable zone in Aviremigia. Personally, I am disappointed that Godefroit et al. (2013) - in the description of Aurornis, not Eosinopteryx - do not include in their phylogenetic analysis also Pedopenna and Yixianosaurus ...