When Producer Steven Spielberg’s movie Jurassic Park was released in 1993, it gave viewers a look at dinosaurs in a way they had never seen before.
Spielberg’s depiction of Tyrannosaurus rex (T rex) is often the first thing that comes to mind when we think of dinosaurs, but University of Toronto Palaeontologist Robert Reisz says we don’t have enough information on the complete life cycle of T rex, and many other prehistoric beasts, to determine their actual behaviour and appearance.
“There is all kinds of talk about Tyrannosaurus, but in fact we don’t have fossils of baby Tyrannosaurus,” Reisz said.
There is, however, one exception; when it comes to a dinosaur known as Massospondylus — what Reisz fondly refers to as ‘Big Mamma’ — the discovery of intact fossilised eggs from the Lower Jurassic Period has given palaeontologists a complete picture of the reptile, estimated to be about four to six meters in length.
Last Tuesday night, Reisz shared his research findings about Massospondylus with U of T alumni and friends during a talk at the Brampton Golf Club on Kennedy Road.
The talk highlights some of the innovative research that is ongoing at the university.
During a multi-year study, working with researchers from Golden Gates Highland National Park in South Africa, Reisz, research associate Dianne Scott and his team extracted dozens of fossilised eggs and embryos from prehistoric nesting sites.
“Altogether seven eggs were immediately recognized”, said Reisz. “We had to actually remove the egg shell.
“These are actually the oldest eggs ever found so we didn’t want to destroy the shell, we just wanted to go in and see as much as we could inside,” Reisz said.
As they probed further into the eggs, they were able to discern the embryos inside, still intact.
They found more eggs and were able to examine them to determine the history of the events that lead to the formation of the nests.
This discovery has allowed them to contribute pertinent changes to the ongoing knowledge of current dinosaur evolution.
“First we found complete nests, which were located right next to each other which tells us that they were communal. They came in as a group, and lay down their eggs,” he said.
They also discovered articulated skeletons which suggest that Massospondylus hatched walking on four limbs but as it grew it walked upright on two legs.
“As it grows from an embryo, the fore limbs become shorter and shorter…,” he said. “We could tell that as an embryo the animal walked on all fours, but as an adult, it must have been bipedal.”
Having the compete fossil history, from embryo to adult, also raises new insights into what Massospondylus ate.
“We didn’t find any teeth in the embryos which also suggests they must have been fed by the parents,” said Reisz, stressing that this interpretation, like knowledge of the dinosaurs, is still evolving.
Reisz findings are on permanent display at the ROM.