What's a Mosasaur ?
When amateur fossil finder Van Turner discovered a small vertebra at a construction site near Dallas 16 years ago, he knew the creature was unlike anything in the fossil record. Scientists now know the significance of Turnerís fossil as the origin of an extinct line of lizards with an evolutionary twist: a land-dwelling species that became fully aquatic.
Turner took the remains to paleontologists at the Dallas Museum of Natural History, but it took several years before scientists from Southern Methodist University and the National Park Service unraveled the mystery of the vertebra's identity and dubbed the find Dallasaurus turneri. Word of Dallasaurus is now reaching the scientific community with a special issue of the Netherlands Journal of Geosciences, featuring an article by SMU paleontologist Michael Polcyn and Gordon Bell Jr. of Guadalupe National Park in Texas.
Polcyn, whose research into Dallasaurus is supported by SMU's Department of Geological Sciences, the Shuler Museum and Institute for the Study of Earth and Man, said Dallasaurus represents a missing link in the evolution of a group of creatures called mosasaurs, prehistoric animals that started out on land but evolved in the seas and dominated the oceans at the same time dinosaurs ruled the land.
Dallasaurus was a three-foot long lizard who lived 92 million years ago in the shallow seas and shores of what was then a stretch of Texas mostly under water, and also used the fossil to better understand the mosasaur family tree. One important aspect of the discovery is that Dallasaurus retained complete limbs, hands and feet suitable for walking on land, whereas later mosasaurs evolved their limbs into flippers.
Polcyn and Bell painstakingly pieced together an understanding of the anatomy and natural history of Dallasaurus from the bones Turner discovered and from some matching skeletal remains in the Texas Memorial Museum at the University of Texas in Austin.
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