Animals

Tyrannosaurs Were Violent Cannibals, Victim Shows

Combat and cannibalism were no strangers to tyrannosaurs, suggest the remains of a tortured dino victim. Continue reading →

Remains of a mutilated dino victim provide strong evidence for what has long been suspected: T. rex and his kin were violent animals that also practiced cannibalism.

The remains, described in the latest issue of the journal PeerJ, are of the large carnivorous tyrannosaur Daspletosaurus, which suffered numerous injuries during its lifetime and was partially eaten after it died.

The clincher is that paleontologists believe that members of Daspletosaurus' own species inflicted all of the damage.

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"This animal clearly had a tough life suffering numerous injuries across the head including some that must have been quite nasty," lead author David Hone from Queen Mary, University of London, said in a press release.

He added, "The most likely candidate to have done this is another member of the same species, suggesting some serious fights between these animals during their lives."

Daspletosaurus lived around 77 million years ago in North America. The victim studied by the researchers hailed from what is now Alberta, Canada. It was an older teenager when it bit the dust, so it hadn't grown to full size yet. Still, this was a large animal. At death it measured about 20 feet long and weighed approximately 1,102 pounds.

Analysis of this dinosaur's skull uncovered numerous injuries that had previously healed.

T. rex Had a Small, Cute Cousin

Hone explained that, although not all of the injuries can be attributed to bites, several are close in shape to the teeth of tyrannosaurs. One bite to the back of the head had broken off part of the skull and left a circular tooth-shaped puncture though the bone.

According to the researchers, the fact that alterations to the bone's surface indicate healing means that the injuries were not fatal and the animal lived for some time after they were inflicted.

The poor dinosaur's life took a turn for the worse later, though. The preservation of the skull and other bones, as well as damage to the jaw bones show that the dinosaur died young and began to decay. Shortly thereafter, a large tyrannosaur - probably from the same species - chomped into the dead teen dino and presumably ate at least part of it.

The remains are unique in that they provide evidence for both combat between dinosaurs of the same species and cannibalism.

T. rex was closely related to Daspletosaurus. They essentially were cousins and grew to nearly the same sizes as adults. It's therefore likely that T. rex and other large carnivorous tyrannosaurs engaged in similar behavior.

Image: An artist's reconstruction of one Daspletosaurus feeding on another. Credit: Tuomas Koivurinne

Jurassic Dino Nesting Site

Jan. 23, 2012

-- The oldest known dinosaur nesting site, dating to 190 million years ago, has been unearthed in Golden Gate Highlands National Park, South Africa. The extraordinary site, described in the latest Proceedings of the National Academy of Sciences, includes multiple dinosaur nests, eggs, hatchlings and the remains of adults for this species, Massospondylus. Project leader Robert Reisz, a professor of biology at the University of Toronto Mississauga, told Discovery News that the dinosaur was herbivorous. Like its sauropod relatives, it had a very small head and an extremely long neck. The hatchlings walked on all fours, but adults were bipedal. "The transition from four legs to two during an individual's lifetime is a very unusual growth pattern that we rarely see in animals, but we do see it in humans," Reisz said. "The largest articulated skeleton of this animal was about 6 meters (19.7 feet) in length, but they probably grew even larger."

Dinosaur Nest The discovery provides evidence for "nesting site fidelity," according to Reisz, "as it looks like these dinosaurs liked this place and returned to it repeatedly to lay their eggs." It's also the oldest evidence in the fossil record for a highly organized nest, with eggs carefully laid in a single layer. Reisz and co-author David Evans, an associate curator of vertebrate paleontology at the Royal Ontario Museum, are shown here standing next to a nest in plaster at the site. Plaster protects the excavated nest, just like the broken bone in a human. The plaster cover is later removed in the lab for research. Reisz said clues about the nest are difficult to interpret, but what's known so far is that "the nests seem to be fairly shallow because all the eggs are in one layer," he said. "We do not know if the nests were covered by vegetation or if they were buried because the nature of the sediments preclude the preservation of plant fossil remains. It is quite possible that the mother guarded the nests." Nest guarding today is fairly common among living reptiles, such as crocodiles. It's also now known "that the hatchlings stayed around the nesting area long enough to at least grow to double in size."

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Adult Massospondylus Skull, Complete Embryo This photo compares the size of the skull of an adult next to the skeleton of an entire tiny embryo. The researchers believe each Massospondylus mother laid a lot of small eggs, at least 35, which was a probable survival strategy. "There were large and small meat-eating theropod dinosaurs around at the time Massospondylus lived,” Evans told Discovery News. "The smaller, more agile predator called Coelophysis, was much smaller than adult Massospondylus, but would have been a threat to the hatchlings and juveniles." So far, the researchers have found 10 dinosaur nests at the site, but they suspect many more are still embedded within the South African cliff. They predict many other nests will be eroded out in time, as the natural weathering process continues.

Dinosaur Embryo Close-Up This close-up of a Massospondylus embryonic skeleton reveals that the head was pushed out of the egg after death. The scientists suspect gases produced by decay caused this to happen. They also think the site was so well preserved because the dinosaur moms chose to lay their eggs in what was then, back in the Early Jurassic Period, a wet spot at the edge of a river. Reisz explained, "Periodically there was an unusually wet season and this area was flooded, drowning the unhatched eggs and embryos, and covering the nests with very fine sediment. Yet this turned out not to be such a horrible disaster for paleontologists." South Africa appears to have been a hotspot for Massospondylus, with other possible nesting sites for this dinosaur probably in existence. So far, however, the one at Golden Gate Highlands National Park is the only nursery to yield complete clutches, with eggs containing embryos, Evans said. He added that similar evidence for large-scale nesting among dinosaurs exists, for dinos such as duck bills and sauropods, but that evidence is about 100 million years younger than this South African site.

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Baby Dinosaur Handprint The discovery provides the world's oldest clear evidence for baby dinosaur footprints at a nesting site. The handprint seen here, as well as the other excavated baby prints, indicates that the infants stayed near the nest site after hatching and walked on all four limbs at first. Reisz said, "The overall body shape of the hatchlings with a large, toothless head, relatively long neck, and general look of helplessness suggests that parental care was very likely in Massospondylus. We think that the mother may have guarded the nest and the hatchlings, but may have also fed the babies with plant material." The paleontologists are now in the process of testing this hypothesis by preparing more embryos from different nests, to see if any of them have teeth. This ongoing research would be the first study of different embryological stages in a dinosaur.

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