Mosasaurs, every bit as prolific, fascinating and nearly as big as some dinosaurs, are becoming more popular for paleontologists to study. Mosasaurs lived and became extinct alongside dinosaurs, but few paleontologists specialize in them. Later mosasaurs grew as large as their dinosaur brethren, reaching up to 45 feet in length. Until the discovery of Dallasaurus, however, only five primitive forms with land-capable limbs were known, all of them found in the Middle East and the eastern Adriatic.
"Lizards had nearly 150 million-year-long history on land; then in the Late Cretaceous, the final stage of the age of dinosaurs, one group moved into the sea and rose to the very top of the food chain," explains Polcyn, director of SMU's Visualization Laboratory, part of the university's geological sciences department. "Starting out as small animals like Dallasaurus, they mastered their new marine environment and rose to become the top predator in their ecosystem, the T. Rex of the ocean."
The Late Cretaceous period was a time of hot house temperatures and rising sea levels.
"As the earth warmed and the seas rose, small land-dwelling lizards took to the oceans and developed increasing levels of seagoing capabilities, and over 30 million years, eventually evolving into the top predator of their domain before becoming extinct some 65 million years ago," says Polcyn.
The advanced fin-bearing mosasaurs have been grouped into three major lineages. Although a small number of primitive mosasaur have been known to retain land-capable limbs, they were thought to be an ancestral group separate from the later fin-bearing forms. Dallasaurus represents a clear link to one lineage of the later forms and the first time researchers can clearly show mosasaurs evolved fins from limbs within the different lineages of mosasaurs.
With the aid of computer science and SMU's visualization laboratory, Polcyn has been ab
Source:Southern Methodist University