Stokes (1957) published on the first reported pterosaur tracks, quadrupedal ichnites he called Pteraichnus. These traces showed a four-toed plantigrade pes and a three-fingered digitigrade manus with the fingers rotated so far laterally that the third finger pointed posteriorly. The wing finger did not make an impression. For the next twenty years or so, these were accepted as extremely rare specimens of pterosaur tracks.
Casamiquela (1962) discovered an unusual track he called, ‘Sauria aberrante” or unusual lizard. Though pterosaurian, no one considered it one. You can see it and other digitigrade pterosaurs tracks here.
Dr. Kevin Padian was a student of the late Dr. John Ostrom (1969, 1976), the professor who rewrote the origin of birds with his discovery and analysis of the lithe and agile dinosaur, Deinonychus, as a close relative of Archaeopteryx. In like fashion, Padian (1983a, b) rocked the paleontological world when he redescribed the Dimorphodon as a digitigrade biped and linking it to dinosaurs in the precladistic age. Padian and Olsen (1984) refuted the attribution that Stokes (1957) had made, using experimental evidence with living crocodilians to show that the quadrupedal tracks must have been make by Late Jurassic crocs. For the next ten years, Padian’s hypotheses remained in force.
The discovery of “Dimorphodon” weintraubi (Clark et al. 1998), later revealed to be a North American anurognathid (Peters 2011), showed the metatarsophalangeal joints of basal pterosaurs were butt joints, incapable of flexion and extension. This, according to the authors, made them permanent flatfoots. (Never mind what to do with that unusual pedal digit 5!) Most workers followed this line of reasoning leaving Padian alone in his digitigrade pterosaur hypothesis.
This watershed year produced two separate worldview-changing papers re-identifying Pteraichnus tracks as pterosaurian. Lockley et al. (1995) and Mazin et al. (1995). These papers overturned Padian’s rule and reestablished the validity of Pteraichnus.
Introducing PILs (parallel interphalangeal lines), Peters (2000) applied them to several tracks and pterosaur feet and found certain matches among taxa widely considered to be beach-combing forms. The PILs also determined that some pterosaurs must have remained bipedal and digitigrade, especially so among basal taxa and the lineage of Pteranodon, save the most derived forms, which became plantigrade. Rotodactylus ichnites, though not pterosaurian, but cosesaurian, were proof of this configuration in Triassic forbearers.
Padian (2003) again argued against the pterosaurian origin of nearly all Pteraichnus tracks, including the originals by Stokes (1957), but this time championed the pterosaur trackmakers of the famous Crayssac location in France. Padian (2003) reported that “trackways considered for attribution to pterosaurs should show (1) manus prints up to three interpedal widths from midline of body, and always lateral to pes prints, (2) pes prints four times longer than wide at the metatarsophalangeal joint, and (3) penultimate phalanges longest among those of the pes.” Strangely, requirement number one forbids bipedalism in pterosaurs, a configuration that Padian (1983a, b) had earlier championed. Requirement number two forbids a digitigrade configuration in pterosaurs, another configuration that Padian (1983a, b) had championed. Requirement number three forbids most of the pterosaurs employed in Peters (2011) from making tracks as only a minority of pterosaurs have elongated penultimate phalanges on every digit (Figs. 1–6).
Kubo (2008) repeated the experiments of Padian and Olsen (1984) and concluded crocs could not have been the Pteraichnus trackmaker, no matter what the condition of the substrate.
Peters (2011) illustrated several dozen pterosaur pedes and matched many to previously unidentified ichnites, including several that were digitigrade with an impression of pedal digit 5 far behind.
More to Come?
I’m sure we haven’t heard the last of Dr. Padian’s battle with Pteraichnus. With respect, I can’t support his position because, as Kubo (2008) pointed out, crocs cannot be the trackmaker of Pteraichnus traces and Peters (2011) reported on several tracks that cannot be made by anything else other than fenestrasaurs and pterosaurs. Padian’s “rules” about pterosaurs in general indicate he has not done the necessary studies with a wide variety of pterosaur feet.
Sometimes bad hypotheses just will not die, no matter the evidence.
As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.
Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.
Casamiquela RM 1962. Sobre la pisada de un presunto sauria aberrante en el Liassico del Neuquen (Patagonia). Ameghiniana, 2(10): 183–186.
Clark J, Montellano M, Hopson J and Fastovsky D. 1994. In: Fraser, N. & H.-D Sues, Eds. 1994. In the Shadows of Dinosaurs. New York, Cambridge: 295-302.
Clark J, Hopson J, Hernandez R, Fastovsk D and Montellano M. 1998. Foot posture in a primitive pterosaur. Nature 391:886-889.
Kubo, T 2008. In quest of the Pteraichnustrackmaker: Comparisons to modern crocodilians. Acta Palaeontologica Polonica 53 (3): 405–412.
Lockley MG, Logue TJ, Moratalla JJ, Hunt AP, Schultz RJ and Robinson AP 1995. The fossil trackway Pteraichnus is pterosaurian, not crocodilian: implications for the global distribution of pterosaur tracks. Ichnos, 4, 7-20.
Mazin JM, Hantzpergue P, Lafaurie G and Vignaud P 1995. Des pistes de ptérosaures dans le Tithonien de Crayssac (Quercy, France). Comptes Rendus de l’Acadé- mie des Sciences, 321, 417-424.
Ostrom JH 1969. Osteology of Deinonychus antirrhopus, an unusual theropod from the Lower Cretaceous of Montana. Peabody Museum of Natural History Bulletin 30: 1–165.
Ostrom JH1976. Archaeopteryx and the origin of birds. Biological Journal of the Linnean Society 8 (2): 91–182.
Padian K 1983a. Osteology and functional morphology of Dimorphodon macronyx (Buckland) (Pterosauria: Rhamphorhynchoidea) based on new material in the Yale Peabody Museum, Postilla, 189: 1-44.
Padian K 1983b. A functional analysis of flying and walking in pterosaurs. Paleobiology, 9:218–239.
Padian Kand Olsen PE 1984. The fossil trackway Pteraichnus: not pterosaurian, but crocodilian. Journal of Paleontology, 58:178–184.
Peters D 2000a. Description and Interpretation of Interphalangeal Lines in Tetrapods. Ichnos, 7: 11-41
Peters D 2011. A Catalog of Pterosaur Pedes for Trackmaker Identification
Ichnos 18(2):114-141. http://dx.doi.org/10.1080/10420940.2011.573605