Research Interests

My primary interests are in the origination and evolution of major vertebrate groups that invaded distinctly different niches or environments (e.g., evolving flight or becoming secondarily aquatic), and in how evolutionary and physical constraints affect their evolution. I work primarily on the Pterosauria, the flying reptiles of the Mesozoic Era, because they are an ideal group for this sort of study [and because John Ostrom told me to!]. Pterosaurs colonized an empty flying-vertebrate niche in the Triassic with a Bauplan that was essentially simply a lightly built archosaur with elongate limbs, a hyperelongate fourth finger, and a membranous wing stretched between the fore and hindlimbs (Fig. 1A). Pterosaurs radiated throughout the Mesozoic, and in the Late Jurassic underwent a major reorganization of Bauplan that produced in a new clade, the Pterodactyloidea, which had larger heads, different wing proportions, and a short tail (Fig. 1B).

Fig. 1. Reconstructions of skeletons and wings in dorsal view and skulls in left lateral view of Rhamphorhynchus (A) and Pterodactylus (B).

Then in the Early Cretaceosous there was a second major reorganization of Bauplan; modifications to the trunk skeleton and pectoral girdle that permitted the evolution of great size (up to 11 m wingspan). I think these new large pterodactyloid pterosaurs formed a monophyeltic group, the Dsungaripteroidea, but some pterosaur workers think these changes occurred as convergent evolution in multiple lineages.

My research has been aimed at understanding pterosaurs first, their phylogeny second, and lastly those bursts of evolution that saw them evolve flight and reinvent themselves twice. For the past ~15 years part of my research effort was directed toward clarifying the anatomy, taxonomy, and relationships of the basal pterodactyloids from the Solnhofen Limestones of southern Germany in order to better understand the origination of the pterodactyloids, funded in part by the Deutscher Akademischer Austauschdienst. Now I am turning my attention toward the pterodactyloids of the Lower Cretaceous to study the evolution of the pectoral girdle and its musculature across the pterodactyloid-dsungaripteroid transition.

I also have minor interests in:

• Trackways—I have published a number of papers on trackways.
• Fluid dynamic and thermodynamic interactions between animals and their environment—My 1996 paper on the dorsal sails of pelycosaurs examined their aerodynamics and thermodynamics.
• Extracting temporal information about animals from the fossil record—My 1995 and 1996 papers on year-classes of Solnhofen pterosaurs looked at temporal information in the fossil record, and I have ideas for a number of other such papers.