Some 20 years ago, someone smuggled dinosaur eggs from Argentina to the United States illegally. The smuggler probably had little clue that inside one of the eggs was one of the best-preserved skulls of a dinosaur embryo ever found, which is now giving us new insights into the facial appearance of one line of our planet’s erstwhile rulers.
“When I had a look at this specimen, I quickly realized how unique this is,” said Martin Kundrát, a paleobiologist at the Center for Interdisciplinary Biosciences at Pavol Jozef Safarik University in Kosice, Slovakia, who’s the lead author of a study published Thursday in Current Biology about the fossil. “It was really amazing to see that such a specimen could really be preserved and still keep a three-dimensional position.”
The skull is about the size of a table grape. Its right side is still entombed in mudstone and siltstone, and its mouth is closed. It isn’t deformed, which is so often the case with bones buried in rock for millions and millions of years, and so it gives a first-of-its-kind glimpse into the start of life of a dinosaur that’s part of a group called the titanosaurs — long-neck dinosaurs that reached weights of 70 tons and lengths of 122 feet. And it has some surprises: It sports a horn on its nose, and its eye sockets face forward, like human eyes.
“I was pretty floored. I thought it was an amazing discovery,” said Michael D’Emic, a vertebrate paleontologist and sauropod expert at Adelphi University in New York who was not involved in the new work, but has studied other sauropod embryos from Patagonia. Many of those skulls are warped and flattened like pancakes — something that can hamper reconstructions of what the dinosaurs looked like in life.
“Just to have that sort of level of detail and preserved in 3-D was just astonishing to me,” he said.
Dr. Kundrát first saw the skull in 2011, and began making detailed 3-D scans of it. The scans let Dr. Kundrát and his team see the skull as a whole without damaging it, and it opened their eyes to something unusual about the embryo’s eyes: The sockets angle toward the front of the skull. This is different from older sauropods, where the eyes face to the sides.
Forward-facing eyes can give animals better depth perception, as with human eyes, Dr. D’Emic said. It’s possible that this feature somehow helped the animals survive after they hatched — especially because there’s no evidence titanosaur parents cared for their hatchlings. But why younger sauropods and not older sauropods needed to be good at gauging the distances between things isn’t at all clear.
“I won’t even venture a guess,” Dr. D’Emic said. “It’s just totally a mystery.”
If the titanosaur could look forward after birth, it might have caught a glimpse of the other structure the team found: a horn on its nose.
“This little embryo is one of the cutest dinosaurs I’ve seen, and at the same time, one of the weirdest looking,” said Stephen Brusatte, a vertebrate paleontologist at the University of Edinburgh who was not involved in the study. “You could call it a unicorn baby dinosaur, because it has a single horn on its head. But unlike the mythical unicorn, where the horn is on the forehead, this dinosaur has a small bumpy horn at the tip of its snout. I’m perplexed by why this horn was there, as we know that adult sauropod dinosaurs don’t have such structures.”
Dr. Kundrát said he suspected that the hatchlings might have the horn for defense against predators, or to help them find food. But nothing is known about what titanosaurs ate, or what their interactions with predators were like, so, like the front-facing eyes, the horn’s exact function will remain a topic for future study.
Today, the skull sits in Los Angeles, in the hands of one of the new study’s authors, Luis Chiappe, a vertebrate paleontologist at the Natural History Museum of Los Angeles County. But as soon as the coronavirus pandemic eases, Dr. Kundrát and his team plan to repatriate the skull back to Argentina.
“This is a part of their national paleontological heritage,” Dr. Kundrát said, “and in my opinion it’s the right thing to do.”