‘Skin Bones’ Helped Large Dinosaurs Survive, New Study Says
ScienceDaily (Nov. 29, 2011) — Bones contained entirely within the skin of some of the largest dinosaurs on Earth might have stored vital minerals to help the massive creatures survive and bear their young in tough times, according to new research by a team including a University of Guelph scientist.
Guelph biomedical scientist Matthew Vickaryous co-authored a paper published in Nature Communications about two sauropod dinosaurs — an adult and a juvenile — from Madagascar.
The study suggests that these long-necked plant-eaters used hollow “skin bones” called osteoderms to store minerals needed to maintain their huge skeletons and to lay large egg clutches. Sediments around the fossils show that the dinosaurs’ environment was highly seasonal and semi-arid, with periodic droughts causing massive die-offs.
“Our findings suggest that osteoderms provided an internal source of calcium and phosphorus when environmental and physiological conditions were stressful,” he said. As a researcher in the Department of Biomedical Sciences in Guelph’s Ontario Veterinary College, Vickaryous studies how skeletons develop, regenerate and evolve.
He worked with paleontologist Kristina Curry Rogers and geologist Raymond Rogers at Macalaster College in Minnesota, and paleontologist Michael D’Emic, now at Georgia Southern University on the study. Vickaryous helped to interpret the results of CT scans and fossilized tissue cores taken from the dinosaurs.
Shaped like footballs sliced lengthwise and about the size of a gym bag in the adult, these bones are the largest osteoderms ever identified. The adult specimen’s bone was hollow, likely caused by extensive bone remodelling, said Vickaryous.
Osteoderms were common among armoured dinosaurs. Stegosaurs had bony back plates and tail spikes, and ankylosaurs sported heavily armoured bodies and bony tail clubs. Today these “skin bones” appear in such animals as alligators and armadillos.
Such bones were rare among sauropod dinosaurs and have appeared only in titanosaurs. These massive plant-eaters included the largest-ever land animals. “This is the only group of long-necked sauropods with osteoderms,” he said.
Other studies have shown that female titanosaurs laid dozens of volleyball-sized eggs. Modern crocodiles and alligators also lay clutches of dozens of eggs and are known to reabsorb minerals from their osteoderms.
The researchers found the new osteoderms along with two skeletons of the titanosaur Rapetosaurus. Unlike the hollow adult specimen, the juvenile specimen was solid and showed little evidence of remodelling. That suggests that osteoderms became more important mineral stores as the animals grew, Vickaryous said.
LARGE NEST OF JUVENILE DINOSAURS, FIRST OF THEIR GENUS EVER FOUND
The findings were reported in the most recent issue of the Journal of Paleontology.
David Fastovsky, URI professor of geosciences, said the bowl-shaped nest measuring 2.3 feet in diameter was found in the Djadochta Formation at Tugrikinshire, Mongolia.
“Finding juveniles at a nest is a relatively uncommon occurrence, and I cannot think of another dinosaur specimen that preserves 15 juveniles at its nest in this way,” he said.
The analysis of the 70-million-year-old nest by Fastovsky and his colleagues found that all 15 dinosaurs — at least 10 of which are complete specimens — were about
the same size and had achieved the same state of growth and development, suggesting they represent a single clutch from a single mother. The discovery also indicates that the young dinosaurs remained in the nest through the early stages of postnatal development and were cared for by their parents.
Protoceratops grew to about 6 feet long and may have taken as long as 10 years to reach full size. Those Fastovsky found in the nest were likely less than one year old when they died.
“I suspect that the preserved animals were rapidly buried by the shifting, accumulating sands that must have constituted the bulk of sedimentation in this setting,” he said. “Death likely occurred during a desert sandstorm. My guess is that the initial and present-day dryness contributed significantly to the superb preservation, not just of Protoceratops, but of all the fossils from this unit.”
Fastovsky calls Protoceratops “a fascinating and unexpected mass of contradictions.” It is an herbivore that lived in a sand sea much like the Sahara Desert and likely bestowed significant parental care on a relatively large number of offspring, perhaps because it lived where mortality was quite high.
A wide variety of theropod dinosaurs lived in Mongolia at the time, some of which, including the notorious Velociraptor, probably ate young Protoceratops‘.
“Juvenile Protoceratops mortality may have been rather high, not only from predation but from a potentially stressful environment, and large clutches may have been a way of ensuring survival of the animals in that setting,” he said. “Nonetheless, if preservation is any indicator of abundance in life, then during the time represented by the Djadochta Formation, Protoceratops were a very common feature of Mongolian Late Cretaceous desert landscapes.”
Fossils of dinosaur-era crocodiles found in Sahara
Five exotic crocodiles that lived alongside the dinosaurs 100 million years ago, including one sporting boar-like tusks and another with a duckbill snout, have been discovered in the Sahara.
Dinosaur Era Crocodile Fossil
Unlike their modern cousins, the ancient crocodilians were as agile on land as they were in the water.
They were reptiles like the dinosaurs, but belonged to a completely separate lineage that continues to this day.
The crocodiles once ran and swam across present-day Niger and Morocco, when the region was covered by lush plains and broad rivers.
Scientists found the newly-identified fossils at a number of sites in the Sahara desert. Many were uncovered at one location, lying on the surface of a remote and windswept stretch of rock and dunes.
Expedition leader Professor Paul Sereno, from the University of Chicago, has previously described the largest find, Sarcosuchus imperator, which measured 40 feet and weighed eight tons.
Popularly known as ”SuperCroc”, the giant carnivore was the biggest but not the strangest of the extinct creatures.
They were given nicknames by the scientists, based on their unusual physical features.
”BoarCroc” (Kaprosuchus saharicus): A 20 feet upright meat-eater with an armoured snout and three sets of dagger-shaped fangs.
”RatCroc” (Araripesuchus rattoides): Discovered in Morocco, this was a three-foot-long upright plant and grub-eater. It had a pair of lower jaw buckteeth which were used to dig for food.
”PancakeCroc” (Laganosuchus thaumastos): This animal’s fossils were found in Niger and Morocco. It was a 20-foot-long squat fish-eater with a three-foot-long pancake-flat head and spiky teeth on slender jaws.
”DuckCroc” (Anatosuchus minor): A three-foot upright species that ate fish, frogs and grubs. It had a broad, overhanging snout and a long nose. Sensory areas on the snout helped it root around shallow waters for prey.
”DogCroc” (Araripesuchus wegeneri): Fossils found in Niger included five skeletons next to each other on a single block of rock. DogCroc was a three-foot-long upright plant and grub eater with a soft, doglike forward-pointing nose.
Describing the finds in National Geographic Magazine, Prof Sereno wrote: ”My African crocs appeared to have had both upright, agile legs for bounding overland and a versatile tail for paddling in water.
”Their amphibious talents in the past may be the key to understanding how they flourished in, and ultimately survived, the dinosaur era.”
Colleague Dr Hans Larsson, from McGill University in Montreal, Canada, who discovered the bones of BoarCroc and PancakeCroc, said: ”We were surprised to find so many species from the same time in the same place.
”Each of the crocs apparently had different diets, different behaviours. It appears they had divided up the ecosystem, each species taking advantage of it in its own way.”
The scientists studied the animals’ brains by creating digital and physical casts from CT-scans, 3D X-rays.
Both DogCroc and DuckCroc had broad, spade-shaped forebrains that looked different from those of living crocodiles.
”They may have had slightly more sophisticated brain function than living crocs, because active hunting on land usually requires more brain power than merely waiting for prey to show up,” said Dr Larsson.
A paper on the finds is to appear in the journal ZooKeys. The creatures will also star in a documentary, ”When Crocs Ate Dinosaurs”, to be shown on the National Geographic Channel.
Source: telegraph.co.uk