Dinos, Sharks Were Predators and Prey
Jennifer Viegas, Discovery News
July 12, 2007 — Sharks and dinosaurs in prehistoric Europe had a taste for each other, suggests a new review of vertebrate fossils found in the Galve region of Northeast Spain.
Diverse findings dating from the late Jurassic to the early Cretaceous reveal that bony fish, salamanders, frogs, 39-foot-long crocodilians, small prehistoric mammals, freshwater turtles, several types of pterosaurs, and various other dinosaurs all once thrived at the Spanish site from around 163 to 145 million years ago.
Teeth from hybodont sharks — extinct, primitive shark-like fish — were found in non-marine rocks. This reveals the hybodonts lived in rivers and lakes right in dinosaur territory. At least one group of dinosaurs, the spinosaurines, was equipped to take on the fish species.
The findings were recently published in the journal Palaeogeography, Palaeoclimatology, Palaeoecology.
Co-author Darren Naish, a paleontologist at the University of Portsmouth, explained to Discovery News that these theropod dinos, which originated in Europe, had “long skulls, retracted nostrils, and unusual, semi-conical teeth,” good for grabbing land prey as well as fish, including small sharks.
Naish emphasized “small,” less than 6.5 feet or so long, since hybodonts could defend themselves with their teeth, sharp spines and pointy horns.
For swimming dinos other than spinosaurines, Naish said “hybodonts would presumably have been a hazard that they would have wanted to avoid.”
“Dinosaur carcasses washed down rivers and into the sea were often scavenged by sharks,” he explained.
Another potential “hazard” would have been the enormous crocodilians, aquatic reptiles related to today’s crocodiles and alligators. Teeth, bony plates and bones are all that remain of these creatures, which grew to about the size of a large school bus.
The Galve assemblage resembles that of Wealden, a widely distributed series of rocks over much of Southeast England.
Michael Benton, who worked with Naish and Barbara Sanchez-Hernandez on the study, is a professor of vertebrate paleontology at the University of Bristol.
Benton told Discovery News that Galve is comparable to Wealden because “the climate was probably similar,” the rock formations date to about the same age, and the two sites are only a few hundred miles apart.
Unique to Galve, however, are “holdover dinosaurs,” mostly sauropods that were already extinct or evolved elsewhere. Benton explained that the dino relicts survived in Spain later than anywhere else “possibly because it was more or less an island,” since the Iberian region was then partly surrounded by seas that separated it from England, France and central Europe.
David Martill, a palaeobiologist at the University of Portsmouth, told Discovery News that the new overview on Galve fossils “is an accurate piece of science.”
In terms of sharks, Martill said they were “diversifying greatly” around the time of prehistoric Galve.
He described the primitive shark hybodonts as having “an impressive series of spines in front of the dorsal fins, and males had rather fierce-looking horns on their heads, which were used to attach the male to the female for a rather painful looking mating event.”
For dinosaurs that encountered them, however, they likely just inflicted pain.