Big news from the world of paleontology on Thursday, as the oldest intact dinosaur embryos ever found have been described, and by a Canadian scientist.
The embryos are those of Massospondylus, a prosauropod that lived about 190 million years ago in the lower Jurassic period in what is now South Africa. The eggs were apparently dug up decades ago, but it was only recently that they were handed over to the University of Toronto and Dr. Robert Reisz to crack open.
There are plenty of pictures of the open egg around the internet, including one here, at the Chicago Herald's website.
Now, even if there was nothing special about these little guys, this find would be neat. It's not just the oldest dinosaur embryo ever found, it's the oldest find ever of any vertebrate embryo. But there is something special about the critters. They have big heads, short necks, no teeth and they seem to have walked on all fours. Adult Massospondylus definitely had teeth (nicely shaped for cropping tough Jurassic ferns and other vegetation) and probably walked on two legs.
This means we can infer a parental relationship between parent and offspring. From the Chicago Herald and Dr. Reisz: Some of the embryos were clearly ready to hatch, he said, but they have no teeth, “and that suggests to us that some form of parental care was required … not just protecting but active feeding.”
How the adults fed the infants, and how long, we may not know until the skeletons of infant Massospondylus in a variety of developmental stages are found. That will likely be never, given the paucity of the fossil record. But we can make some guesses, based on other dinosaur finds and the behaviour of living animals. And the speculation is almost as much fun.
Did the adults disgorge half-digested plant slurry for their offspring to lap up? Or did they create "crop milk," a kind of protein-rich goop that some modern birds use to feed their chicks? Did the young stay in nesting colonies, within the confines of a dirt bowl, or did they follow the adults like modern hoofed mammals?
It also has massive implications for the way we view sauropods. There have already been discoveries that indicated that ornithopods (Maiasaura) and theropods (Oviraptor) brooded their nests and took care of their young. But sauropods have been seen as more primitive. We know they didn't have feathers, because skin impressions of sauropod embryos have been found in Argentina.
But if prosauropods cared for their young, then sauropods certainly could have. But how? They grew larger than any other land animal, and their young hatched from eggs no larger than soccer balls. How did a massive Argentinosaurus, the largest land animal we know of, take care of something considerably smaller than its own head? Something it could crush, by accident, and not even notice?
I love science. So many fun questions yet to answer.
Here are some more Massospondylus images at DinoData.net.