By Steven Scarpa, Associate Director of Marketing and Communications
Examining the controversial notion of ‘living fossils.’ Identifying the oldest fossil example of an ancient lizard. Demonstrating how the bite of modern crocodiles evolved from their small ancestors. These findings came from the exceptional work of Yale graduate students.
Those students – Chase Brownstein, Lisa Freisem, and Alexander Ruebenstahl – were awarded the George Gaylord Simpson Prize, an annual award given by the Yale Peabody Museum to published papers on evolution and the fossil record. Simpson was considered one of the most influential paleontologists of the 20th century. He received his doctorate from Yale, studying mammalian evolution using the Peabody’s collection.
“The Simpson Prize recognizes the important work our graduate students are contributing to our understanding of the fossil record,” said museum director David Skelly. “It’s an honor to support these students at the beginnings of their long careers.”
“This is the kind of work that represents the future of paleontology,” said David Heiser, the Peabody’s director of student programs.
Chase Brownstein’s paper, “The Genomic Signatures of Evolutionary Stasis,” demonstrates that several lineages of ‘living fossil’ fishes – gars, sturgeons, and paddlefishes – have exceptionally slow rates of molecular evolution relative to other jawed vertebrates. Species known as ‘living fossils’ often display very little variation in appearance from actual fossils of their ancient relatives.”
“These rates are so slow that sister species of gars that last share common ancestry over 10 million years ago show no differences in over a third of the over 1000 sequences that we examined,” Brownstein said.
Lisa Freisem’s research identified the oldest known articulated sphenodontian skull in Europe and one of the group’s earliest members. Sphenodontians are small lizard-like reptiles currently only represented by the New Zealand tuatara. However, their history ranges back 250 million years. This new genus, Parvosaurus harudensis, is preserved as a skull that includes features of early as well as more derived sphenodontians.
“Parvosaurus thus paints a more complex scenario in the early evolutionary history of sphenodontians and improves their early fossil record in Europe,” Freisem said.
Alexander Ruebenstahl’s paper offered a detailed anatomical description of two exceptionally preserved skulls of Jurassic crocodylomorphs from China, called Junggarsuchus and Dibothrosuchus, and phylogenetic analyses of their relationships.
“Our results show that some of the key modifications of the skull for the powerful bite of living crocodilians evolved very early in their small, fully terrestrial ancestors,” Ruebenstahl said.