Crocodiles are mistakenly referred to as ?living fossils? due to the repeated evolution of similar looking skull and body shapes throughout their history. Thus, they appear not to have changed in millions of years. This repeated evolution of similar features (convergent evolution) confounds scientists? efforts to reconstruct the evolutionary relationships of extinct crocodiles. This project will construct a dataset of physical characteristics from myriad fossil forms, including a new fossil from Oregon. New and previously implemented methods will be utilized to test whether characteristics are the result of shared ancestry or similar ecology (e.g. similar diet). This information will be used to determine the relationships within the group.
Paleontology is among the most publically accessible scientific endeavors and offers a gateway to enhancing overall interest in science. The Oregon fossil will be exhibited in the Condon Collection of Fossils, University of Oregon, incorporating results of this project. Investigators will also present findings of this research to amateur paleontology groups, school groups, and disseminate it to the scientific community through peer-reviewed publications and presentations at scientific meetings. The techniques developed will be applicable for all investigators studying relationships of groups that show convergent evolution. Data produced for this project will be made available for future research through publically accessible formats.
Crocodiles are mistakenly referred to as "living fossils" due to the repeated evolution of similar looking skull and body shapes throughout their history. Thus, they appear not to have changed in millions of years. This repeated evolution of similar features (convergent evolution) sometimes confounds scientists’ efforts to reconstruct the evolutionary relationships of extinct crocodiles. This project constructed a new dataset of physical characteristics from fossil forms from around the world, including a new fossil discovered in Oregon. This information was used to determine the evolutionary relationships within the group. The results demonstrate that many of the physical characteristics previously used to suggest close evolutionary relationships are actually the result of shared ecology (e.g. similar diet) as opposed to shared ancestry. The findings of this project drastically change our interpretation of the evolution of the early evolution of crocodiles. Modern crocodiles possess an extensive bony secondary palate which allows them to breathe while their mouth is open under water. The extensive secondary palate of the group was thought to evolve in a gradual step-wise fashion through time from the earliest land-dwelling members of the group with a weakly developed palate to modern groups with a complete palate. If the Mesozoic group of marine crocodiles (thalattosuchians) is evolutionarily outside of this group, it challenges this long held belief. Thalattosuchians have a well developed secondary palate which is often depicted in text books as the intermediate form between modern crocodiles and ancient fossil relatives. This implies that either the thalattosuchians independently evolved an extensive secondary palate, or that the common ancestor of crocodyliforms had an extensive bony palate and early taxa possessing what looks like a primitive palate underwent an evolutionary reversal (secondary loss). Either scenario is considerably more complicated than previously thought. Continuing work will help determine which of these evolutionary scenarios is true. Results of this study have been presented at numerous scientific meetings and contributed to the partial completion of a doctoral dissertation. Findings have also contributed to three upcoming museum including two foreign institutions (Royal Saskatchewan Museum, Canada; Muséum d’Histoire Naturelle du Havre, France).
