Artwork by Julius Csotonyi
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."
NEWS: Nest Full of Baby Dinosaurs Found
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.
NEWS: Dino-Era Disaster: Multiple Drowned Toothy Birds
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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A newly discovered early relative of Tyrannosaurus rex was a fearsome predator in what's now southern Utah about 80 million years ago, according to a study.
“King of Gore” (Lythronax argestes) had looks and a lifestyle to match its name. Described in the latest issue of the journal PLoS ONE, it was by far the scariest large predatory dinosaur alive at that time during the Late Cretaceous Period.
“We thought that Lythron, or gore in Greek, exemplified its presumed lifestyle as a predator with its head covered in the blood of a dead animal,” lead author Mark Loewen, a research associate at the Natural History Museum of Utah, told Discovery News. The dino co-existed with the largest alligator that ever lived, 40-foot-long Deinosuchus, which it probably avoided in favor of easier prey.
“(Lythronax's) forward-facing eyes, powerful limbs and large size would have made it an efficient hunter of both duckbilled dinosaurs and horned dinosaurs like Diabloceratops,” added co-author Joseph Sertich, curator of Vertebrate Paleontology at the Denver Museum of Nature and Science.
“A mouthful of knife-edged teeth set in powerful jaws would have made short work of potential prey, carving out huge chunks of flesh and bone to swallow hole,” Sertich continued.
A Bureau of Land Management employee named Scott Richardson first discovered the dinosaur’s fossilized skeleton. For the study, Loewen and his team excavated the remains and analyzed them. They compared 501 skeletal features of Lythronax with those of 54 different other species of known, carnivorous dinos. The paleontologists found that Lythronax is most closely related to T. rex and another dinosaur known as Tarbosaurus bataar.
In terms of size, Sertich said that Lythronax was smaller than T. rex, reaching around 30 feet in length as opposed to 40 plus feet. Lythronax was no lightweight, though, and would have tipped the scales at about nearly 3 tons.
Both “King of Gore” and “Tyrant Lizard King” had about the same number of teeth set in a wide skull. Their snouts were short and narrow, but widened at the eyes to permit binocular vision.
“Binocular vision requires eyes set slightly apart that have overlapping fields of view, meaning the same eye sees the same thing at the same time from a slightly different perspective,” Loewen explained. “This allows the animal to have depth perception.”
Although T. rex emerged some 10 million years after Lythronax, both lived at a place called Laramidia, which existed along the western shores of a great seaway that separated North America. The tyrannosaurid dinosaurs likely evolved in isolation on the island continent, with incursions of the seaway separating small areas of land from each other. This further allowed different species of dinosaurs to evolve on different parts of the landmass.
Sertich explained that rising mountains and fluctuating sea levels made for a very dynamic landscape, which set the stage for the evolution of unique dinosaurs and their ecosystems.
“Laramidia over its history was a paradise of dinosaur evolution,” Loewen said. “Many groups, including ankylosaurs, ceratopsians, hadrosaurs, ornithomimids and tyrannosaurs underwent radiations on this island continent. In some ways, it was the crucible of evolution during the Late Cretaceous.”
The researchers unearthed the remains of a new specimen of Teratophoneus that is the most complete tyrannosaur from southern Laramidia. Together, all of the fossils suggest that the evolution of T. rex and its relatives was much more complex than previously thought.
Co-author Randall Irmis, of the Natural History Museum of Utah and the University of Utah’s Department of Geology and Geophysics, told Discovery News that the recent discoveries reveal ancient ecosystems that were nearly unheard of just a decade ago.
“Nearly every dinosaur species we find is new to science, and the same is true for other animals like crocodiles and turtles,” he said. “Many folks are under the impression that one has to go to exotic locales, such as China, Mongolia, Argentina or Madagascar, but these finds exemplify the fact that we need not look any further than our own backyard to make important new dinosaur discoveries.”
The very toothy skull of Lythronax is now on permanent display at the Natural History Museum of Utah.