During the Mesozoic, also called the “Age of Reptiles,” a number of reptile lineages secondarily adapted to life in the sea. Over the past twenty years, I have pursued a global revision of Triassic stem-group Sauropterygia, marine reptiles that later gave rise to the more widely known plesiosaurs, pliosaurs and elasmosaurs of the Jurassic and Cretaceous. This work provided the basis for the ongoing collaborative research program with faculty and students of the Institute of Vertebrate Paleontology and Paleoanthropology, and of the Peking University in Beijing, focusing on new collections of Triassic marine reptiles from southwestern China. These new collections require taxonomic work not only on sauropteryians, but also on other marine reptiles such as protorosaurs and thalattosaurs. Most recently, the early Upper Triassic of Guizhou Province has yielded ancestral turtles. The Triassic record of marine reptiles is rich and diverse, and allows the study of broad evolutionary patterns as originally terrestrial reptile lineages adapted to marine habitats.
I'm also involved in research on the origin of snakes. This collaborative research program seeks to integrate paleontology, comparative morphology and molecular systematics. The origin of snakes is a longstanding problem in the evolution of reptiles that still awaits a satisfactory resolution. It is now embedded in a broad-scale investigation of the evolutionary history and relationships of squamate reptiles (snakes, worm lizards, and other lizards) as part of the Tree of Life program sponsored by the US National Science Foundation.
Finally, I take an active interest in the history and philosophy of comparative biology. This involves research on the history of evolutionary thought, on the ontology of evolving entities, and on the history and philosophy of biological systematics from Ernst Haeckel to Willi Hennig.
Rieppel O. Sauropterygia I: Placodontia, Pachypleurosauria, Nothosauroidea, Pistosauroidea. Encyclopedia of Paleoherpetology, 12A. Munich: Pfeil, 2000.
Rieppel O, Zaher H, Tchernov E, Polcyn MJ. The anatomy and relationships of Haasiophis terrasanctus, a fossil snake with well-developed hind limbs from the mid-Cretaceous of the Middle East. J Paleont, 2003, 77:336-358.
Rieppel O. The metaphysics of Hennig’s phylogenetic systematics: substance, events and laws of nature. Syst Biodivers, 2007, 5:345-360.
Rieppel O, Li C, Fraser NC. The skeletal anatomy of the Triassic protorosaur Dinocephalosaurus orientalisLi, from the Middle Triassic of Guizhou Province, southern China. J Vert Paleont, 2008, 28:95-110.
Rieppel O. Total evidence in phylogenetic systematics. Bio Philos, 2008, 24:607-622.