Dr. Mark Witton is fantastic artist and devotee of pterosaurs. He has a new book called Pterosaurs (with an Amazon.com preview). I’ve ordered the book and will make an in depth report after it arrives. The following is based on the online preview of chapter 1. Witton’s writing style is entertaining and engaging. The book should have popular appeal on that level.
The cover portrays a magnificent crested Nyctosaurus at sunrise or sunset. Gorgeous!
Then things tumble.
Witton’s Table of Contents shows an embryo Pterodaustro with a very short rostrum, unlike any Pterodaustro I’ve ever seen. And I’ve seen the embryo. The rostrum extends nearly the entire length of the egg. An agreement with Laura Codorniú prohibits me from publishing the image until she does, but the reconstruction of the long-beaked embryo Pterodaustro is based on that tracing. As we learned earlier, pterosaurs grew isometrically, resembling their parents on hatching.
Witton’s Rhamphorhynchus image on page 2 portrays the infamous cruro/uropatagium, a membrane spanning the hind limbs and not including the tail. The image also includes the infamous deep chord wing membrane, for which there is no evidence whatsoever as the Sordes situation was falsified. Witton’s two Rhamphs also have much shorter wings than any Rhamphorhynchus I’ve ever seen. One of Witton’s wonders has brought its wrists (carpals) in close to the base of the neck, which is novel, at least, but kills the tension on the extensor tendon that keeps the wing membrane aerodynamic. As in birds, when the elbow flexes, the wing folds. Having the wings fold in flight isn’t bad. Birds do it all the time for a brief low drag rest. At least the feet are properly positioned in Wittons’ illustration.
Page 3 portrays several dozen pterosaurs doing the forelimb leap that is such a travesty and fantasy that I slap my head every time I see it again and again. It has become firmly entrenched. Gadzooks@!# what is the ptero-world coming to?
Page 4 has a fine picture of Pterodactylus antiquus, the first pterosaur known to science, with a big round head crest. Not quite ready to buy into that one quite yet. Some Pterodactylus did have a crest, but not that one.
Page 12 portrays a hypothetic pterosaur ancestor. It looks like Peteinosaurus with a short digit 4 leaping from a branch (using muscular hind limbs). The caption reads, “The fossil record has yet to reveal an “intermediate” between fully formed pterosaurs and possible ancestors, meaning we can only speculate on their anatomy and appearance.” And once again, pterosaur professors are casting a blind eye toward the hard evidence presented in the large reptile tree where dozens of ancestors are lined up. As you’ll recall, ludicrous as it sounds, we can even put turtles up as the closest known sisters to pterosaurs if we delete all the other sisters and candidates from the new Lepidosauromorpha, as demonstrated here. This just proves that pterosaur workers are actively avoiding the issue and the answer. But, I have to say, it’s a beautiful and evocative image that Witton has created, wrong though it may be.
Page 16 portrays three purported pterosaur ancestor/sisters, Sharovipteryx, Euparkeria and Scleromochlus. Witton calls Sharovipteryx an archosauromorph protorosaur, when it is neither. It is a fenestrasaur tritosaur lepidosaur, as we learned earlier. Euparkeria is closest to erythrosuchids, about as far from pterosaurs as one could imagine. Scleromochlus, shown hopping in Witton’s illustration with a dino quadrate leaning the wrong way, is a basal crocodylomorph. Witton strongly leans toward the “pterosaurs are ornithodires” direction despite the tiny hands and lack of pedal digit 5 in Scleromochlus.
Witton takes aim at my placing pterosaurs within the Squamata as the most unlikely hypothesis currently under consideration. See a recent post on this here. Witton writes, “There seems little similarity between the skulls of pterosaurs and the highly modified, mobile skulls of squamates or any similarity between the trunk and limb skeletons of each group.” Well, frequent readers will know that pterosaurs are tritosaur lepidosaurs, an outgroup clade to the two that make up the Squamata, the Iguania and the Scleroglossa. Pterosaurs are neither of these. Tritosaurs do not have the mobile skulls found in some squamates. They also don’t have the fused tarsals of squamates. They are distinct. Witton has whitewashed the tritosaur fenestrasaur hypothesis with this “red herring,” while virtually ignoring the fenestrasaurs, following in the less than noble footsteps of our colleague Dr. David Hone, whose exploits you can read about here. In chapter one, at least, Witton avoids any discussion of the pteroid and prepubis in Cosesaurus and other fenestrasaurs. Why should he ignore these key and readily observable traits? Dr. Pierre Ellenberger saw them first without recognizing their significance.
Page 17 Witton then discusses the possible protorosaur origins of pterosaurs, pointing to the shared trait of an elongated neck and forgetting the not-so-elongated neck of the basalmost pterosaur, MPUM6009. Witton points up the “fact” that protorosaurs lack an antorbital fenestra, but recent finds show that two protorosaurs had such a fenestra by virtue of convergence (really a side issue of little consequence). Witton finishes with protorosaurs by noting the body shapes are not at all pterosaurian, which is true.
Witton invites a closer look at Sharovipteryx and notices similarities to pterosaurs in the hind limbs and their membranes, but notes, “It’s hard to find other features that reliably link this animals with pterosaurs.” He may not have looked at the actual specimen as I have. Evidently he did not notice the ilium was anteriorly elongated, prepubes were present, more than five sacrals were present, the tail was attenuated with parallel chevrons, the bones were hollow, the feet have the same morphology as pterosaurs with a short metatarsal 5 and an elongated and robust p5.1 as obvious and compelling similarities. Once again, the blind eye rules. Witton reports that the Sharovipteryx skull lacks an antorbital fenestra and the foot is unlike that of any pterosaur. Where does he get his information? Certainly not from any sort of direct observation or adherence to the literature. Of course he doesn’t back up any of this with evidence. Witton concludes by noting that gliding with hind limbs is unique, failing to find parallels in Microraptor and the uropatagia of fenestrasaurs including pterosaurs. Sharovipteryx had fore limbs. Witton just doesn’t know or doesn’t show what they look like. But you can see them here.
Page 18 Witton prefers the archosauriform ancestry hypothesis due to the shared features of an antorbital fenestra and reduced bone counts in the fifth pedal digit, perforated lower jaws, and “many other anatomical similarities.” Really? Witton equates an evaporating pedal digit 5 in archosauriforms with the robust element in pterosaurs (and, of course he doesn’t count the ungual on the pterosaur digit). A robust pedal digit 5 is also found in Huehuecuetzpalli and all the tritosaur lepidosaurs that followed (except Macrocnemus and the drepanosaurs). Why doesn’t Witton consider these and put some study into them? The antorbital fenstra of archosauriforms is always (except for proterosuchians) surrounded by a fossa, a trait lacking in any pterosaurs.
Witton also prefers archosaurs as pterosaur sisters, and, in particular, Scleromochlus, despite the tiny hands that were, ironically, used to rule out Sharovipteryx. Evidently Witton prefers to have it both ways, so long as he stays within tradition. Witton lists fusion of the two proximal ankle bones to the shin (which does not occur in pterosaurs), reduction of the fibula (also in tritosaurs), the structure of the foot (actually more like that of tritosaur lizards like Cosesaurus, which retain an elongated pedal digit 5, which archosaurs lack), “several limb and hip proportions” (can Witton get even more vague here?) and the lack of bony scales along the back (then why is he ignoring those on Scleromochlus and Scutellosaurus).
Witton notes the shield-like pelves were different than in dinosaurs, but defends that by saying, “This may not be surprising, however, given, that pterosaur hindlinmbs were, uniquely among ornithodirans, used to support the wing in flight.” Utter rubbish!!! on the face of it and not pertinent to any phylogenetic discussion. You take the traits as they are and you let the computer decide where the taxa belong most parsimoniously. The “why” question or reason is never in play. By the way, similar pelves to pterosaurs can be found in fenestrasaurs, but these are ignored by Witton.
Witton writes, “arguments that basal pterosaurs were bipedal and digitigrade may be flawed” because basal ornithodires (aka: Asilisaurus, which bears no resemblance whatsoever to pterosaurs) were quadrupeds. This is far-reaching and totally bogus. I would be ashamed and would expect heavy chastisement having made such a comparison, especially after promoting bipedal Scleromochlus as a potential ancestor. But then Witton tops that bungle of reasoning by saying that Scleromochlus is “suspected of hopping about on plantigrade feet.” More fantasy! Few creatures, other than deer and horses, have feet more obviously digitigrade than Scleromochlus. Witton also ignores the known bipedal pterosaur footprints (more here, here and more info here).
Page 21 Witton prefers an imagined hypothetical ancestor to a real one, and it glides from trees. Of course, this does nothing to explain the origin of flapping (because no gliders flap, unless they started off as flappers). Witton ascribes the mobility and length of the fifth toe to its use as a stabilizing tool, ignoring the fact that most tritosaurs from Tanystropheus to Sharovipteryx, have such a fifth toe, thus it cannot be developed for flight. Witton reports that the fifth toe, which is lateral, elongates to frame the medial membrane, which should strike you as odd and implausible. In reality the fifth toe is not connected to a membrane, except in Sharovipteryx, and each membrane trails each hind limb. They don’t cross to connect with each other.
Page 22 Witton reports that the hind limbs rotate out sideways to create efficient airfoils, but even that is fraught with error. One: Archosaurs can’t do this with their erect femurs. Two: Basal pterosaurs can’t do this either with their erect femurs. Raising the hind limbs to the horizon happens in later, more derived pterosaurs with a more sprawling femur.
Witton reports that during the evolution of pterosaurs that the fourth finger became so enlarged and unwieldy that it needed to be stowed away when grounded. We can all stow away our fingers by pressing them against our palms, but Witton ignores this. He also ignores the axial rotation of metacarpal 4 so that digit flexion puts digit 4 along the posterior rim of the hand, not the palmar side any longer. Witton reports ungual 4 was missing, since it was no longer necessary. We’ve seen so many several cases of ungual 4 present on pterosaurs that it needs to be considered universal.
Witton adds fibers to wing membranes as they need to be more sophisticated in their unsupported regions, ignoring that Cosesaurus had trailing fibers before it had wing membranes (Ellenberger 1993, Peters 2009).
With regard to flapping, our expert Dr. Witton reports, “At some point, manipulation of these wings in the vertical plane produced flapping, and self-propelled flight was achieved.” Gee, he makes it sound almost as if it was that easy. At ReptileEvolution.com and the PterosaurHeresies blog you learned the exact steps the exact taxa took to achieve flapping prior to the development of wings in pterosaurs, paralleling that same development in birds. So if Witton’s book leaves you unsatisfied and yearning for real answers, come see these websites and blogs.
Witton ascribes the development of flight muscles and bones to the ability of quadrupedal pterosaur ancestors to chiefly employ the forelimbs during leaps. He sort of leaves the larger hips and thighs out of the equation, evidently incapable of creating all the power necessary for a leap and leaving the unused arms in this bipedal model to do something else, like flap as a secondary sexual trait.
Dr. Witton does take the brave leap of including my published works in his reference list, something Dr. Unwin did not do in his less recent pterosaur book.
Let’s face it
If Dr. Witton does not even know what pterosaurs are (which he has acknowledged in his book), he has no business acting as an expert on pterosaurs and writing books about them. Unfortunately this is an acceptable trend continued by Dr. Unwin from Dr. Peter Wellnhofer. In chapter one Witton has already published too many errors. It’s too late in the game to fold ones’ hands and politely tell your readers, “Good question… we really don’t know. It’s one of the mysteries of paleontology.” There’s something called phylogenetic analysis that is guaranteed to give you an answer when you’re looking for an ancestor. However, you’ll have to include at least a few of the right taxa (among the tritosaurs in this case), to get close to the right answer. If you’re looking for the ancestors of pterosaurs, they’re right here in one place.
We’ll look at other Witton chapters in the future. But this one on pterosaur origins really irks me. It’s rather embarrassing that this sort of crap (a complete avoidance of certain data) is still being circulated. But I _do_ love the artwork.
Ellenberger P 1993. Cosesaurus aviceps . Vertébré aviforme du Trias Moyen de Catalogne. Étude descriptive et comparative. Mémoire Avec le concours de l’École Pratique des Hautes Etudes. Laboratorie de Paléontologie des Vertébrés. Univ. Sci. Tech. Languedoc, Montpellier (France). Pp. 1-664.
Peters D 2009. A reinterpretation of pteroid articulation in pterosaurs. Journal of Vertebrate Paleontology 29: 1327-1330.
Witton M. 2013. Pterosaurs. Princeton University Press. 291 pages.