An article published in the journal “Current Biology” describes the study of a new species belonging to the pliosaurid group called Luskhan itilensis discovered in present-day Russia about 130 million years ago. A team of scientists including Gleb N. Uspensky of Ulyanovsk State University, who discovered this marine reptile, examined the fossils concluding that there were evolutionary convergences between different species after an extinction that happened at the end of the Jurassic period.
The pliosaurid (Pliosauridae) group is part of the plesiosaur (Plesiosauria) order, a highly diversified marine reptiles that lived during the Mesozoic era. The most iconic representatives of this order had long necks but pliosaurids were characterized by shorter necks while their heads were elongated. Plesiosaurs lived in the same era as dinosaurs but were reptiles, turtles’ distant cousins.
In 2002, Dr. Gleb N. Uspensky discovered an almost complete skull of a pliosaurid about 1.5 meter (5 feet) long, a size that suggests that it was a big animal that maybe could be 8 meters (26 feet) long. Its characteristics recall those of fish-eating animals such as some species of river dolphins. This suggests that pliosaurs had a greater diversification than expected with the occupation of more ecological niches than those in which these reptiles were discovered before.
This possibility was hypothesized because paleontologists tended to think that pliosaurids were apex predators while plesiosaurs belonging to the polycotylid (Polycotylidae) genus, pliodonts’ distant cousins, were known as fish eaters. The discovery of Luskhan itilensis suggests that the situation was more complex with regard to the diversification of pliosaurs and the evolutionary convergences with polycotylids.
Evolutionary convergence has already been studied in various researches and includes cases of reptiles and dinosaurs separated by 100 million years that showed similar adaptations. In short, it’s nothing new and in this case we’re talking about different species of plesiosaurs, what is interesting to paleontologists is the discovery of an ecological niche so far unknown occupied by pliosaurs.
At the end of the Jurassic period, about 145 million years ago, there was an extinction that struck plesiosaurs too but the discovery of Luskhan itilensis shows that at least pliosaurs recovered and went on to occupy ecological niches where they were perhaps not present before. Pliosaurs got extinct some tens of millions of years later, before the dinosaurs, and only now paleontologists are reconstructing their history.
