Shell Crushing Pterosaurs and Bad Posture

Small post here. This one is going to seem incomplete, the title a tease. It’s a premise for more things. But you’ll see where I’m going with this. This concerns the issues of how we look at pterosaurs when they’re walking around on all fours. Continue reading

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Orpheus Rex

He doesn't look like he just lost his wife...Last time I talked about Erlikosaurus andrewsi, it was Stephan Lautenschlager’s paper with Larry Witmer, Perle Altangerel, and Emily Rayfield discussing the biomechanical aspects of toothloss and beak formation in Erlikosaurus andrewsi. That work indicated a far likelier restoration of this almost-most-famous therizinosaur as having a beak at the tip of its jaws (a proposition that isn’t exactly perfectly obvious, nor has it been subject to much testing). This week, a new paper by the authors of that paper discusses the second of Erlikosaurus‘s cranial osteology papers, a follow-up to the older Perle et al. paper which examined the skull at hand. Lautenschlager et al. have CT scanned the holotype skull and thus have been able to look far deeper into regions of the skull than any previous worker (Lautenschlager et al., 2012; Lautenschlager, 2013) , examined the neural endocranial vault and cranial nerve pathways, and looked in detail at the distribution of cranial airsacs that invade the bones of the skull, previously only examined through breaks in the specimen. The influence of cranial pneumaticity and toothloss on the evolution of the therizinosaur cranium is, sadly, only approachable in limited scope: A complete skull is known only for one two taxa (Beipiaosaurus inexpectatus, Erlikosaurus andrewsi, while in the former the skull is preserved in 2.4D and hasn’t been examined in high detail), and partial skulls known for two additional taxa (Falcarius utahensis, Nothronychus mckinleyi), both of which were subjected to CT examination but are otherwise far less complete and prevent tracking the more extensive cranial evolution of therizinosauroids.

But knowing the detailed pneumatic expansions into the skull, and the deeper underlying anatomy that so fascinates with the peculiar skulls of therizinosaurs, tells us a lot about the mechanical stresses that may have permitted pneumatic invasion, limited it, and the conflicting or covariant mechanisms that affected bite performance. These things require more work like this, and deeper understanding of cranial anatomy without preconceptions about evolutionary relationships. This work precedes arguments of evolution, but at the same time influences and is influenced by it. Groundwork anatomical understanding helps provide the basis for phylogenetic information, but context of that anatomy requires a phylogenetic framework; and the use of the phylogenetic bracket, a tool of logical inference for muscle reconstruction and anatomical interpretation, informs both.

Lautenschlager, S. 2013. Cranial myology and bite force performance of Erlikosaurus andrewsi: a novel approach for digital muscle reconstructions. Journal of Anatomy 222: 260-272.
Lautenschlager, S., Rayfield, E. J., Perle A., Zanno, L. E. & Witmer, L. M. 2012. The endocranial anatomy of Therizinosauria and its implications for sensory and cognitive function. PLoS ONE 7: e52289.
Lautenschlager, S., Witmer, L. M., Perle A. & Rayfield, E. J. 2013. Edentulism, beaks, and biomechanical innovations in the evolution of theropod dinosaurs. Proceedings of the National Academy of Sciences, Philadelphia 110 (51): 20657-20662.
Lautenschlager, S., Witmer, L. M., Perle A., Zanno, L. E. & Rayfield, E. J. 2014. Cranial anatomy of Erlikosaurus andrewsi (Dinosauria, Therizinosauria): New insights based on digital reconstruction. Journal of Vertebrate Paleontology 34 (6): 1263-1291.


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Toothed Birds

It soars over the tossing waves on enormous, outspread wings. With nary a flap, the bird is soaring dynamically high above the ocean, its eyes scanning the sky around it and sea below. It may seem unremarkable to us today: the feet are webbed and extend behind it, the tail is short and blunt, the body rounded and muscular, but encased in a bullet-like shell of feathers, dark above and light below. The wings are mostly arm, the hand bones short. The feathers are short, and the arms make up most of the wing length. It looks like an albatross, but is several times larger than any living albatross; but it is otherwise unremarkable in its appearance from any other great seabird. That is, until you examine its head.

There are many types of ocean-going flyers, pelagic birds of one type or another. Those that hug the shores or feed in the shallows such as cormorants and auks, and those that make vast searches of the ocean such as boobies, and albatrosses. Examining their wings will tell you much about how they get around; and examining their jaws will tell you how they might catch their prey — together, these tell you what they might feed on, what they prefer. Continue reading

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What Else Happened? II – More Tails of Pterosaurs

Continuing a story of the low-key, not-Spinosaurus paleontological papers recently published, discussing our bizarre Mesozoic macrofauna, this installment covers a few pterosaur tidbits.

The first of these is an amazing assemblage of scattered bones of numerous different-sized individuals that are all almost certainly a single species of pterosaur. What is remarkable about this assemblage is that there are several extremely well-preserved remains of individuals, including skulls, with further support for sexual-dimorphism of the cranial crest in some pterosaurs. The second of these is a paper on the tail of an heretofore otherwise un-tailed group of pterosaurs, Anurognathidae, and the implications of this tail relating to their phylogenetics.

Continue reading

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Toothed Birds, A Preview

A piece I’ve been mulling around for about a year, but my laziness interfered. No more.

Toothed Birds silhouettes

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What Else Happened? I – The Dawn Dryosaur

Ignoring Spinosaurus for now, paleontology came up with a few other announcements in the last few weeks. Some pterosaurs (gotta love them) but also non-theropod dinosaurs! They do exist, they are interesting, but they receive much less press. Over the next few days I will present small posts on each of these and get away from what does tend to be an overly theropod-driven blog and the hype around #SpinoGate. Continue reading

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The Outlaw Spino Saurus

There’s been a lot of news now about Thursday’s (Sep. 11, 2014) publication on a new specimen attributed to Spinosaurus aegyptiacus. A lot of hype rose up months back about the release of  a photo of a mount of some unusual bones, and what that entailed. As with every fossil discovery, caution had to be carefully tended in regards this mount because we had no idea what it was based on. This mystery was spoiled, and it seems the culprit was wilier than we all thought.

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