Long ago, carnivorous dinosaurs grew serrations on the back of their teeth called denticles, all the better to eat prey with.
From these abrasions — the microwear — and the shape of dino dentition, paleontologists say they can tell not only what these predators ate but how, said a report in the journal Current Biology. Researchers in Spain and Canada have examined the denticles in 57 fossil teeth from three groups of similarly sized dinosaurs, Troodon, Dromaeosaurus and Saurornitholestes, which were about the size of a large swan, as well as a much larger, 9-foot-tall tyrannosaur called a Gorgosaurus.
“We have been able to infer that, even if these different dinosaurs had different types of denticles in their teeth, they were biting in the same way, through a ‘puncture and pull’ system,” said Angélica Torices, a paleontologist at the University of La Roja in Spain.
The maneuver involved a clampdown with the teeth, then a tug backward with the head. This eating method has not gone extinct with the dinosaurs. Komodo dragons, the largest living lizards, use it.
Humpback baby boom near Antarctica
In a rare piece of good news for whales, humpbacks who live and breed in the southern oceans near Antarctica appear to be making a comeback, with females in recent years having a high pregnancy rate and giving birth to more calves.
Humpback whales were nearly hunted out of existence in the late 19th and most of the 20th centuries until treaties were signed to stop killing them. The end of hunting has fostered the recovery of the school-bus-sized animals whose life spans are roughly comparable to ours, said Ari Friedlaender, an associate researcher at the University of California, Santa Cruz.
Slightly more than 60 percent of the females had high progesterone levels in their blubber, indicating they were pregnant, said the study in the journal Royal Society Open Science. It may have been easier for the humpbacks to recover than the bigger fin and blue whales because the humpbacks mature faster, have a short period between pregnancies, and have centralized breeding grounds.