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.
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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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The ongoing government shutdown has stalled plans to haul a near-complete T. rex fossil to its new home at the Smithsonian National Museum of Natural History, a federal institution forced to shut its doors last week.
The T. rex was set to leave its current home in Montana on Friday (Oct. 11) for a cross-country road trip. As part of a new loan agreement, the Smithsonian, the world's most visited natural history museum, will be the dinosaur's steward for the next 50 years.
But Smithsonian magazine, the official journal of the institution, reported that the T. rex transfer has now been postponed until April. (See Images of the T. Rex Fossil)
"It's a major specimen, so we're being very prudent about how we handle it," Kirk Johnson, the museum's director, told Smithsonian magazine. "There's a lot of uncertainty with the shutdown, and uncertain availability of federal workers to do the work that we need to do."
The fossil's planned arrival at the Smithsonian on Oct. 16 was meant to coincide with the fourth annual National Fossil Day. The museum typically receives 7.3 million visitors per year, according to its website. It is closed in the wake of the shutdown, and most of its staff has been furloughed.
The dinosaur has been dubbed the Wankel T. rex after Kathy Wankel, a rancher and amateur fossil hunter who discovered its arm bones in Montana's Fort Peck reservoir in 1988. Since it was unearthed on federal lands, the dinosaur belongs to the U.S. Army Corps of Engineers. That agency had loaned the fossil to the Museum of the Rockies at Montana State University in Bozeman, where it was prepared and put on display in its original "death pose" for two decades.
The T. rex, which measures 38 feet (11.5 meters) long and weighs 7 tons (6.3 tonnes), will be the centerpiece of the Smithsonian's new dinosaur hall, scheduled to open in 2019. The new wing will feature other key specimens from the Smithsonian's collection of 46 million fossils.
T. rex lived in North America some 68 million to 66 million years ago. It was one of the largest known carnivorous dinosaurs and one of the last non-avian dinosaurs to roam Earth before to the Cretaceous-Paleogene extinction event. Fossil hunter Barnum Brown discovered the first T. rex bones in Montana in 1902 at the Hell Creek Formation, the same rock formation where the Wankel specimen was found.
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