research has suggested Tyrannosaurus rex was related to chickens, now
findings hint this giant predator might have acted chicken too.
of picking on dinosaurs its own size, researchers now suggest T. rex
was a baby killer that liked to swallow defenseless prey whole.
evidence of attacks of tyrannosaurs or similar gargantuan "theropods"
on triceratops and duck-billed dinosaurs has been uncovered before,
conjuring images of titanic clashes.
such as Tyrannosaurus are often seen as the perfect killing machines
with extremely powerful bites, which were able to bring down even the
largest possible prey," said researcher Oliver Rauhut, a paleontologist
at Ludwig Maximilian University of Munich in Germany.
although there were a great many such giant carnivores over the course
of the age of the dinosaurs, there are surprisingly few bite marks in
the fossil record when compared to the age of mammals. Indeed, details
of the scratches and punctures from most examples of dinosaur attacks
seem to suggest these collisions between teeth and bone were accidents.
very few fossils that reflect the hunt of predatory dinosaurs on large
herbivores tell a tale of failure — the prey either got away, or both
prey and predator were killed," Rauhut noted.
all hints that while conflicts between T. rexes and prey likely
occurred, these were probably the exception and not the rule.
not saying bloody clashes never happened in dinosaurs," , said
researcher David Hone, a paleontologist at the Institute of Vertebrate
Paleontology and Paleoanthropology of China in Beijing. "I don't want
to detract from the real drama. But we need to look seriously at what
was common, and that probably didn't involve T. rex chasing down an
8-ton Triceratops that had meter-long horns to bite it in half."
Rauhut and Hone suggest large theropods stuck mostly to devouring
youngsters, including their bones, thus explaining why fossils bearing
toothmarks are rare.
adult and well-armed relatives, these young animals hardly posed any
risk to the predators," Rauhut said. "And their tender bones would have
added important minerals to a theropod's diet."
fact that large theropods ate bones is certain. Fossilized dung, or
coprolites, from large theropods often contain scraps of bone,
suggesting these carnivores gulped down fragments of ribs, vertebrae,
and other relatively small bones while feeding. Intriguingly,
crocodiles — among the closest living relatives of dinosaurs — have
extraordinarily strong acids in their stomachs to completely dissolve
the bones of young victims.
evidence for their idea, the researchers point out past finds of
dinosaur nests "indicate that they contained large numbers of eggs
which should have resulted in a high number of offspring," Rauhut said.
"But little of this is reflected in the fossil record. Juvenile
dinosaurs are surprisingly rare, maybe because many of them have been
eaten by predators."
It makes sense that
even a mighty carnivore like T. rex would aim young. The very rare
finds of stomach contents of predatory dinosaurs suggest that small
prey was swallowed whole.
predators prefer old and sick animals or unexperienced young
individuals," Hone said. "These are an easy prey to bring down and the
risk of injury for the predator is much lower. This strategy was
probably the same in dinosaurs."
rather self evident to say something like 'dinosaurs are like all other
predators,' yet it has barely been mentioned," Hone told LiveScience.
paleontologist Thomas Holtz at the University of Maryland, who did not
participate in this study, found it "quite reasonable that baby
dinosaurs were winding up in the guts of theropods. Although placental
mammals tend to have very few offspring, especially when they get big,
with elephants having a baby maybe every two years, dinosaurs kept
popping out babies, which suggests a high mortality rate of the young.
At the same time, it makes sense that predators in general go after
prey that do them the least damage."
confirming or refuting this idea will be hard, since most of the
possible evidence that large theropods preferred youngsters might have
been destroyed "by theropods digesting it completely," Rauhut explained.
number of alternative explanations for the lack of juvenile dinosaur
bones exist as well. "Maybe juvenile bones naturally did not preserve
as well, lived in environments where they wouldn't preserve as well,"
To gather evidence for their
idea, Rauhut suggested "a survey of existing collections and special
care to look for fragmentary and possibly stomach-acid edged bones in
new excavations." Holtz also suggested looking at dinosaur footprints
to see how common tracks of different age ranges were "to get some idea
of mortality rates."
Hone and Rauhut detailed their findings online August 3 in the