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  While researching my natural history books, I learned what was known about hundreds of prehistoric animals. Of course, many mysteries remain. The mysteries of paleontology, especially those surrounding the flying reptiles, the pterosaurs, became a big interest. I started making contributions to the academic literature in 2000 and several published papers followed. Besides those listed below, several papers are currently in review or in press.

Peters, D. 2000a

Description and Interpretation of Interphalangeal Lines in Tetrapods
Ichnos, 7: 11-41

Parallel interphalangeal lines (PILs) are sets of straight and more or less parallel lines that intersect interphalangeal joints in all tetrapods, whether 9-fingered or three-toed. They mark where the hinge lines are in the manus (hand) or pes (foot) so that the joints work in unison whether flexing or extending. They shift with evolution, but they even remain in flippered limbs. No one ever noticed these before. They help determine whether fossil feet were digitigrade or plantigrade by their continuity or discontinuity in one configuration or the other. Using PILs I discovered that basal pterosaurs and several derived taxa were digitigrade. The beachcombing pterosaurs, the ones making all the footprints, were plantigrade. Most paleontologist don't bother matching feet or tracks to specific pterosaurs, so they think all pterosaurs were plantigrade. They're not sure what to do with the elongated fifth toe of basal pterosaurs. I showed in digitigrade Rotodactylus tracks that matched the foot of Cosesaurus the big fifth toe impressed far behind the others, making a circular impression.The proximal phalanges were elevated because the metatarsophalangeal joint was stiff and inflexible. All in all it was similar to a human with its fifth finger curled under the palm while extending the other four.


Peters, D. 2000b

A redescription of four prolacertiform genera
and implications for pterosaur phylogenesis
Rivista Italiana di Paleontologia e Stratigrafia 106: 293-336

Cosesaurus, Sharovipteryx, Longisquama and Langobardisaurus are the four so-called "prolacteriforms." Now we know that none are related to Prolacerta, but this paper showed that all four were related to one another and to pterosaurs, which had been traditionally nested with dinosaurs. This default nesting was only in the absence of the others. This paper was my first experience with cladograms. It includes many beginner mistakes. One of the matrices has a data shift that was not caught in proofing. Nevertheless, it also solved several problems in pterosaur systematics by simply suggesting inclusion of these taxa. It demonstrated that the palatal shelf was not the palatine bone, but the maxilla itself expanding lingually. The palatine and ectopterygoid in pterosaurs fuse to form an L-shaped to V-shaped bone, the ectopalatine. The two distal tarsals were actually the centralia and the 4th distal tarsal. Hone and Benton in 2007 and 2009 tried to attack it, but likewise made several mistakes. Few paleontologists reference it, preferring traditional models. New discoveries, in press, further cement the relationships of pterosaurs to cosesaurs.


Peters, D. 2002

A New Model for the Evolution of the Pterosaur Wing - with a twist
Historical Biology 15: 277-301

Using Cosesaurus, Sharovipteryx and Longisquama I showed that nearly every aspect of pterosaur anatomy, from foot to pelvis to skull, was present in these cladistic predecessors of pterosaurs. Contrary to the traditional model which proposed a crawling lizard with long fingers, I showed the wings came last, as in birds and bats. I proposed that the wings developed distally, rather than close to the body, as in flying lemurs. Subsequent discoveries (in press) have confirmed this hypothesis. Along with a distal wing origin, this paper also proposed a very narrow wing membrane, not attached to the ankles or shins, but stretched principally between the elbow and wing finger, with a fuselage fillet extending back from the elbow to the thigh. A narrower wing would fold almost invisibly, as demonstrated by fossils, something the deep wing cannot do. No one has published evidence for a deep chord wing membrane, but it remains the traditional choice for paleontologists.


Peters, D. 2003

The Chinese vampire and other overlooked pterosaur ptreasures
Journal of Vertebrate Paleontology, 23(3):87

After the 2002 publication of Jeholopterus, I found a good image of the specimen and placed it on my scanner for enlargement on my computer screen. The original authors, Wang, Zhou, Zhang and Xu, were unable to discern many if any details in the skull. The bones were extremely thin. The skull, built like a bubble, was crushed and smeared. After several weeks of seeking borders and bones, I arrived at a colored tracing that appeared to make sense in terms of similarity to other pterosaurs. The first clue was the clawed finger on top of the skull, which the authors had missed. Reconstructing the skull I noticed that only two teeth were elongated, like a rattlesnake. The others were like plier teeth, useless for penetration. The jawline was highly curved and the quadrate leaned forward, different than most pterosaurs. This enabled an extremely wide gape, again like a rattlesnake. The key was the palate. Unlike most pterosaurs, the palate bones of Jeholopterus were built to withstand and transmit forces from the hammerblows delivered by the two long teeth to the sides and rear of the jaws. Wang, X., Zhou, Z., Zhang, 2002. Chinese Science Bulletin 47(3), 226-232.

Previously considered indecipherable, the crushed skull elements of the newly discovered Chinese anurognathid pterosaur, Jeholopterus ningchengensis, yield new information on the unusual feeding strategy of this extinct flying prolacertiform. Vampirism is indicated by a suite of characters. Two hypertrophied maxillary fangs are buttressed posteriorly by a hyperrobust palate arranged to transfer stabbing shocks laterally and posteriorly. The gape is greatly increased by a quadrate that not only leans anteriorly, like that of a rattlesnake, but the articular surface bends posteriorly. Plus the jaw line is curved 90 degrees; from premaxilla to quadrate. After fang insertion, such a curve permitted the blunt rostrum to roll forward, locking the fangs beneath the victim?s epidermis for unshakable adhesion. The dentary teeth are small and closely spaced for gripping without penetrating a pinched mound of dermis oozing blood. Presumably blood was ingested via tongue lapping. Unlike other pterosaurs, the hyper-extendable and flexible manual claws were capable of parallel insertion into a wall-like substrate, in this case, dinosaur skin. Pedal digit V was longer than in any other pterosaur, apparently to increase puncture leverage for anterior claw penetration, like a church key can opener. The sharp terminal phalanx of pedal digit V could be injected posteriorly for unshakable pedal adhesion. The atypically flexible tail was tipped by a bundle of hairs. A slender plume-like parietal crest extended as far as the pelvis. Both could have been used to distract flies while Jeholopterus was otherwise immobilized during feeding. A sister taxon, Anurognathus, has primitive versions of these characters. Another sister taxon, Batrachognathus, shares robust limbs, a small sternum and large eyes, but does not have large claws, or fangs. It appears to have been a more benign feeder than the nightmarish Jeholopterus.


Peters, D. et al. 2005
David Peters;, Brigitte Demes, David W. Krause;, Michael LaBarbera, and Olivier Rieppel

Suction Feeding in Triassic Protorosaur?
Science 308:1112-1113
DOI: 10.1126/science.308.5725.1112c

I argued and demonstrated with an illustration that Dinocephalosaurus could not and did not expand its esophagus with its elongated neck vertebrae, but instead was a bottom-dweller that raised its head to swallow a bubble of air every so often and struck at fish that swam overhead within range of its hyper-elongated neck and wicked protruding teeth and within sight of its dorsal eyes.


Peters, D. 2007

The origin and radiation of the Pterosauria.
Flugsaurier. The Wellnhofer Pterosaur Meeting, Munich 27

The interrelationships of taxa within and preceding the Pterosauria are revised here. Previous attempts at reconstructing cladistic relationships within the Pterosauria mistakenly used various archosauriforms as outgroups, used too few taxa, used too few characters and employed supra-generic terminal taxa that were not monophyletic. A number of previously considered synapomorphies now test as homoplasies. Many tiny pterosaurs (skull height < 2cm) previously ignored because they were considered juveniles were found to bridge important phylogenetic gaps. These pterosaurs are no smaller than the smallest adult birds and bats. Furthermore, tracings of embryo pterosaurs in their egg shells demonstrate that great morphological change does not occur during ontogeny, so the inclusion of tiny pterosaurs in cladistic analysis does not introduce spurious data. The present study generated a matrix of 182 characters against 126 pterosaurs and 16 outgroup taxa. PAUP produced a single robust tree establishing the following interrelationships within the Pterosauria, which is within the Squamata, as shown by a concurrent study. The basal lizard, Huehuecuetzpalli is the most primitive taxon in this newly revealed third squamate clade between Iguania and Scleroglossa. Two branches arise from it. Jesairosaurus is basal to the Drepanosauridae. Three distinct specimens of Macrocnemus give rise to the Tanystropheidae,the Langobardisaurinae and to the Fenestrasauria respectively. Within the Fenestrasauria Cosesaurusis basal to Sharovipteryx, Longisquama, Austriadactylus is a sister taxon. One of two major clades, the Dimorphodontoidea, includes the Dimorphodontidae and the Anurognathidae. The other major clade includes all other pterosaurs with Eudimorphodon + (Campylognathoides + Rhamphorhynchus) at its base. Higher dorygnathoids divide into the Dorygnathidae and a clade with Sordes at its base. In the former two distinct Dorygnathus specimens are basal to Ctenochasma and kin on one branch and to Quetzalcoatlus and kin (formerlyconsidered azhdarchids) on the other. Within the Sordes-based clade, Pterorhynchus and Scaphognathus crassirostris are basal. Subsequently two distinct smaller Scaphognathus specimens are basal to two major clades. The first is comprised of a series of tiny pterosaurs, Cycnorhamphus and the Ornithocheiridae. The second includes some tiny pterosaurs, the Pterodactylidae and the Germanodactylidae. From the latter arise the Dsungaripteria (Dsungaripteridae + Tapejaridae) and a clade comprised of (Azhdarcho + Eopteranodon) + (Pteranodon + Nyctosaurus). Thus the former monophyletic "Pterodactyloidea" is revealed to be four distinct clades demonstrating some convergence. Major clades typically have a spectral series of tiny pterosaurs at their base suggesting that paedomorphosis was a major factor in pterosaur evolution.


Peters, D. 2009

A Reinterpretation of Pteroid Articulation in Pterosaurs - Short Communication
Journal of Vertebrate Paleontology 29(4):1327–1330, December 2009

Below is an unpublished abstract. The earlier report mentioned therein is Bennett (2007). This report marked the first identification of a pteroid outside of the Pterosauria and further cemented the relationship of Cosesaurus to pterosaurs.

The pteroid is a carpal bone traditionally considered unique to pterosaurs. It supported the propatagium, the anterior flight membrane spanning the radius and humerus. Another small bone, the preaxial carpal, likewise appeared anterior to the main portion of the carpus. An earlier report corrected a long-standing hypothesis that the pteroid articulated in the fovea of the preaxial carpal by demonstrating that sesamoid A was located in the fovea. Thus the pteroid articulated elsewhere. That previous report articulated the pteroid against the medial surface of the preaxial carpal, essentially ventral to the fovea. Here in situ data demonstrate that the base of the pteroid actually articulated with the proximal syncarpal in all pterosaurs. The distal pteroid weakly contacted the proximal portion of the preaxial carpal. The origin of the pteroid remains a mystery, but a pteroid, a preaxial carpal and sesamoid A appear in Cosesaurus, a nonvolant sister taxon to pterosaurs.


Peters, D. 2010

In defence of parallel interphalangeal lines
Historical Biology iFirst article, 2010, 1–6 DOI: 10.1080/08912961003663500

Virtually parallel lines can be drawn through the interphalangeal joints and across the ungual tips of every tetrapod manus or pes, including wings and flippers. Their presence indicates that phalanges operate in sets sharing common hinges, whether for walking (extension) or climbing (flexion). A recent paper has attempted to dismantle both the observation and utility of parallel interphalangeal lines. Here, I rebut those spurious arguments and report additional evidence.


Peters, D. 2011

A Catalog of Pterosaur Pedes for Trackmaker Identification
Ichnos 18(2):114-141.

The matching of ichnites to extinct trackmakers has been done successfully with a variety of taxa, from basal hominids to basal tetrapods. Traces attributed to pterosaurs have been studied for more than 50 years, but little interest has been shown in the pedes themselves. While ichnites can vary greatly in their correspondence to their trackmaker, most pterosaur tracks appear to preserve sufficient detail to assess their origins. This report presents a catalog of pterosaur pedal skeletons that can be matched to a wider spectrum of ichnites, including digitigrade and bipedal ichnites previously not associated with pterosaurs. A variety of pedal characters separate several putative genera into distinct clades, some only distantly related to one another. Distinct pedal characters indicate certain tiny pterosaurs were not juveniles of dissimilar adults, but were separate taxa and likely adults themselves. A squamate and fenestrasaur origin for pterosaurs is supported. These new insights overturn long-standing paradigms. The pterosaur pes contains a wealth of data that should not be ignored. Application of this data enables a more precise identification of both skeletal taxa and ichnotaxa.

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