New 'holy-grail' pterosaur paper by Jean-Michel Mazin and Joane Pouech announcing a new ichnotaxon, Rhamphichnus. That's right: we finally have non-pterodactyloid pterosaur tracks, and textbooks need rewriting. Yes. (My #paleoart of it below). sciencedirect.com/science/articl…
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(I'm about to share several diagrams from Jean-Michel and Joane's paper, so credit, unless stated, for non-palaeoart images goes to them).
This is a big deal because, in > 200 years of research, we've never had any hints about how non-pterodactyloids walked. All trackways known to date belong to pterodactyloids: short-tailed, long-armed pterosaurs of Late Jurassic and Cretaceous age. (Walking azhdarchids pictured)
Without tracks to guide us, the terrestrial capabilities of non-pterodactyloids have been controversial. A prevailing view is that they were sluggish sprawlers, but others saw them as bird-like bipeds. (Summary image from my 2015 review of these ideas: peerj.com/articles/1018/)
The absence of non-ptero tracks was often argued as reflecting their genuine lack of terrestrial capability. Absence of evidence, in this case, was evidence of absence. Notions that hindlimb membranes shackled the legs were also popular (despite this not bothering bats at all).
I've had a long-held interest in the terrestrial locomotion of these animals, and wrote a lengthy paper critiquing existing ideas in 2015. I concluded that at least some non-pterodactyloids were likely competent terrestrial animals, with pterodactyloid-like upright limbs...
...while others showed evidence of having sprawled forelimbs, but that sprawling, in itself, does not equate to sluggishness. Of course, without tracks, these ideas were hard to verify. My paper is open access, and can be found here: peerj.com/articles/1018/
The new tracks, Rhamphichnus, confirm that non-pteros were not sluggish, slow animals shackled by their membranes. Three Rhamphichnus ichnospecies are named in the new paper, but they don't necessarily reflect three distinct trackmakers - more likely different gaits/speeds.
In all Rhamphichnus, the hand and footprints are no further apart than those of pterodactyloids, so the legs were held directly beneath the body and the arms, if sprawled (as shoulder anat. implies), still tucked the hands beneath the body. (Image shows R. crayssacensis)
What makes Rhamphichnus different, however, are details of the hand and foot prints. For one, the walking fingers face forward, not sideways, as in pterodactyloids. This seems weird, but it turns out that non-ptero wing fingers fold roughly perpendicular to the walking digits.
We've known about this hand config from bony anatomy for a while, but most of us artists - including myself - missed it. We've restored the hand walking pose as in pterodactyloids but, nuh uh, wrong. So that's a butt-tonne of early pterosaur palaeoart which needs revising. D'oh.
Further weirdness comes from the long fifth toe. In pterodactyloids the fifth toe is vestigial and leaves no impression, but non-pteros have v. long fifth toes that support the uropatagium (= leg membrane). How did that work on the ground? Folded up? Wrapped around the leg?
Turns out we've been over-thinking it: it just lays flat on the ground during walking, like a regular toe. I can't tell you how many headaches this stupid toe has given as an artist, and all this time it actually _functioned as a freakin' toe_, as well as a membrane spar. Sheesh.
Jean-Michel and Joane have some ideas about the trackmaker, too. As the name implies, Rhamphichnus is thought to have been made by rhamphorhynchids: long-winged, short-legged Jurassic pterosaurs of perhaps gull-like ecology.
I reviewed this paper so had a heads up about the tracks. Jean-Michel and Joane did not have a life recon of their trackmaker in the MS, and I was so excited about their work that I volunteered: the first pterosaur recon informed by Rhamphichnus. I'm still stoked about it.
Being a sucker for vintage palaeoart, I suggested that we echo the first-ever artistic attempt to put a pterosaur with a trackway, the famous Rhamphorhynchus drawn by Auguste Faguet in 1863. (This image is often mistakenly attributed to Édouard Riou.)
Of course, Faguet's Rhamphorhynchus is atop horseshoe crab tracks, not genuine pterosaur tracks. It would be almost another 100 years before pterosaur tracks were identified, and another 150 before Rhamphichnus came along. These data have really been a long time coming!
Faguet's pterosaur is replete with anatomical errors, so we had to correct and adjust it not only to fit the new tracks, but also to make it look like Rhamphorhynchus. But I did my best to include lots of nods to Faguet's work: the pose, basic composition, skin details etc.
Tipping our hat to Faguet is kind of a way of saying that things are coming full circle. From knowing nothing about pterosaur tracks in the 1800s we can, 150 years on, finally say something about the terrestrial locomotion of pterosaurs in general, not just pterodactyloids.
This is not to say there are not a hundred questions to now answer, though. Do all non-ptero tracks look like this? How exactly did rhamphorhynchids stand and walk? How quickly could they move? Why are non-ptero tracks still so rare compared to pterodactyloid tracks?
So there's still a lot to do. Nevertheless, this is really exciting and something that all pterosaur fans should be really interested in: one of our 'holy grail' specimens has finally been found, and we can start answering a major outstanding question.
And that's where I'll end. Be sure to check out Jean-Michel and Joane's paper (if you can, not OA, sorry), and congratulations to them both on this important find!
