Monday, December 17, 2012

Field Guide Rejects: Zapsalis

My new book A Field Guide to Mesozoic Birds and Other Winged Dinosaurs is now available! The book can be purchased via Amazon or CreateSpace. A PDF version is available 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!).

The problem with writing and illustrating a book covering hundreds of feathered dinosaur species is that it's easy to get on a roll, then get lazy. Specifically, there were one or two instances during the making of the book where I got cocky and finished the bulk of an illustration off the top of my head, only checking it against research later. In all of these instances, I ended up having to modify or flat-out cut the illustration while writing the explanatory text. So much for the info sitting at the top of my head!

Luckily, in many cases I was able to salvage my work by tweaking the paintings in Photoshop to fit a different species, especially where the original was highly speculative to begin with. For example, I was really happy with my initial restoration of the tooth taxon Troodon asiamericanus, and with a few adjustments it now features proudly in the finished book as Linheraptor tani. I was so pleased with my restoration of the possible gigantic velociraptorine (err... itemirine) Itemirus that I chucked out my already-completed restoration of Achillobator (previously featured here), broadened the Itemirus snout, shortened the legs, and used that painting instead. However, there's one restoration I kinda liked a lot that didn't make it into the final book in any form.

Speculative restoration of Zapsalis abradens by Matt Martyniuk
My original plan was to include some of the Lancian-age aviremigian taxa known from very fragmentary remains in the Lance and Hell Creek Formations. I have sitting on my HD right now restorations of Pectinodon bakkeri, the unnamed Scollard formation avimimid, and every named species of Cimolopteryx. I hope one day to complete a field guide style book about the Lance formation, so I probably won't share these just yet (though one of the Cimolopteryx made it into a figure in the finished book along with a few other rejected avians). What I will share is a restoration of a bird I mistakenly thought was a member of this fauna when I painted it. Above is my illustration of Zapsalis abradens, a small (juvenile?) morph of eudromaeosaurs known only from a distinctive kind of tooth (inset). In my mind, I'd always associated this species with the Lance, and Zapsalis-like teeth have been reported from that formation. However, after finishing my painting (which I personally thought came out pretty adorable-looking), I went to do the writeup for it. Tooth taxa do require a bare minimum in the way of research before illustration after all, which is part of the reason why all of them ended up getting cut from the book as too speculative. Lo and behold, the holotype specimen, and indeed most specimens, of Z. abradens aren't from the Lance at all--they're from the Judith River/Dinosaur Park Formation!

So, Zapsalis had two reasons to be cut. One, it was obviously far too speculative to include in a book focusing on comparing externally visible traits. Two, I had to admit that even the name itself is a bit dubious if it's from the DPK. Unlike the Lancian fauna, where no eudromaeosaurs have ever been named and so nothing competes for priority, there are several eudromaesaurs from the DPK. Is Zapsalis a distinct species? Maybe, but if not, it could represent a different morph of either Saurornitholestes or Dromaeosaurus. It would take priority over either name, but without any way to currently tell which (if any) it is, it's kind of a "nomen dubium".


6 comments:

  1. I'm happy to report a colleague studying theropod teeth was prompted by my discussion of Zapsalis to study it himself and reached the same conclusions I did regarding its validity. The paper should be appearing soon, and he was even nice enough to acknowledge me in it. :)

    http://home.comcast.net/~eoraptor/Dromaeosaurs.htm#Zapsalisabradens

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    1. @Mickey Great to hear! Without scooping the paper, is there reason to think the differences between Z. and Saurornitholestes and Dromaeosaurus aren't ontogenetic?

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    2. Well I can't scoop the paper since I only know it agrees with my conclusion that Zapsalis is a valid taxon ("?Dromaeosaurus morphotype A") and thus not Paronychodon, but I'd say the fact Zapsalis and Dromaeosaurus teeth are the same size (~10-15 mm) shows they aren't ontogenetic stages of one taxon. Zapsalis isn't very similar to Saurornitholestes and overlaps it in size too, though on average it's larger than that genus.

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  2. "My original plan was to include some of the Lancian-age aviremigian taxa known from very fragmentary remains in the Lance and Hell Creek Formations. I have sitting on my HD right now restorations of Pectinodon bakkeri, the unnamed Scollard formation avimimid, and every named species of Cimolopteryx. I hope one day to complete a field guide style book about the Lance formation, so I probably won't share these just yet."

    Damn, you're a tease XD

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  3. A field guide style book about the Lance Formation may be possible, but the problem is that complete deinonychosaurian skeletons have not yet been found in the Lance Formation, so it may be best to wait for a complete dromaeosaur skeleton. So far, all paravian species from the Lance Formation are based on isolated remains and looking for complete paravian specimens will be a tall task that requires visual ground-penetrating technology (like that used in the discovery of Animantarx).

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