Big Mama was brooding her eggs (Image: Mick Ellison/American Museum of Natural History)
She was sitting on her nest keeping her eggs warm, just like modern birds do, when disaster struck
Discovered: Gobi Desert, Mongolia, 1994
Age: 83 to 66 million years
Location: Mongolian Dinosaur Museum
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The first oviraptor was discovered in Mongolia in 1922. It was given its name, which means 鈥渆gg thief鈥�, because it was found near a nest of what appeared to be Protoceratops eggs.
In 1993, however, Mark Norell of the American Museum of Natural History found a fossilised embryo in an identical egg. He recognised it as a kind of oviraptor, suggesting the original thief was in fact a parent.
The next year, Norell was back in Mongolia when he spotted bones and claws protruding from the sand. But Norell had limited space in his trucks. The bulky fossil might have stayed where it was had team member Luis Chiappe not injured his foot. He wanted to collect a specimen rather than walk around searching for more. A day or two later, Chiappe drove up to Norell and another team member, Jim Clark. 鈥淲e found something you won鈥檛 believe,鈥� Chiappe told them.
The skull of the dinosaur was missing. But much of the rest of the skeleton was present 鈥� and under it there was a nest of eggs. 鈥淚t鈥檚 clear it was sitting on the nest,鈥� says Clark, now at George Washington University in Washington DC. What鈥檚 more, it was sitting in exactly the same position birds adopt when incubating their eggs. There had been hints before that some dinosaurs brooded their eggs, but the discovery of Big Mama was conclusive proof ().
Big Mama was apparently brooding her eggs when a sand dune collapsed after heavy rains and buried her alive, Clark says. The 1994 expedition also found other oviraptors on their nests, but none as well preserved as Big Mama (see diagram).FIG-mg30090901.jpg
The eggs were laid in pairs, a sign that these dinosaurs had paired oviducts, unlike birds, which have only one. Preparation of the fossil , and Clark estimates about as many more are not exposed. They might not all belong to Big Mama: modern ostriches brood communally, with many birds contributing eggs to the same nest.
In fact, it is not even clear Big Mama is a she, but in birds females usually brood the eggs. (And technically Big Mama is an oviraptorid since she may belong to the genus Citipati rather than Oviraptor. But without the skull we cannot be sure, Clark says.)
Many questions remain about the extent of parental care in dinosaurs. How widespread was brooding, for instance? Evidence is sparse but in 2013 it was reported that Troodons might have been brooders too 鈥� , whereas eggs that get buried have lots.
And what about the largest Oviraptors, which weighed as much as 3000 kilograms? Wouldn鈥檛 they have crushed any eggs they sat on? Kohei Tanaka of the University of Calgary in Canada thinks they with a gap for their tail, and sitting on the bare ground in the middle of the circle.
Then there鈥檚 the question of whether hatchlings were cared for by their parents or had to fend for themselves from the start. The duck-billed dinosaur Maiasaura appears to have fed its hatchlings, as did Psittacosaurus, a distant relative of Triceratops. And it appears parental care may have evolved very early on: at the oldest known dinosaur nesting site, in South Africa, some footprints of young Massospondylus are twice the size of those of new hatchlings, suggesting . This nesting site is 190 million years old, from near the beginning of the age of the dinosaurs.
Read more: 鈥�Stunning fossils: The seven most amazing ever found鈥�
