Have you ever looked at the face of a dinosaur embryo? Well, now’s your shot.
A new study has described the first near-intact embryonic skull of a dinosaur. The stunning research provides invaluable insight into the development of sauropods, a clade of plant-eating dinosaurs known for their extremely long necks, long tails, small heads, and thick legs. The researchers say the dinosaur embryo was most likely a titanosaurian, a group of colossal sauropods named after the Titans – the supersized deities in Greek mythology that preceded the Olympian Gods – that include some of the biggest vertebrates to walk the planet.
"This small embryo shows how one of the largest dinosaur groups, titanosaurians, looked like before they hatched," Martin Kundrat, lead study author and associate professor at the PaleoBioImaging Lab at Pavol Jozef Šafárik University in the Slovak Republic, told IFLScience.
"There is no doubt that the most interesting part was to assemble the 'puzzle pieces' to understand the message coming from the past, over 80 million years ago. We used to get excited about the skeleton of giant dinosaurs, but it's always different when you look inside the egg of these giants," Kundrat adds.
The 80-million-year-old fossilized eggs were first discovered some 25 years ago in Patagonia on the southern tip of Argentina, a place that’s no stranger to giant dinosaurs. The story of the fossil actually remains fairly hazy as they were initially illegally exported from the country before being sold in the US to one of the study co-authors, Terry Manning. After realizing the significance of the specimen, he later agreed to send this unique fossil back to Argentina "as it is the part of their paleontological heritage," Kundrat explains.
Using a new imaging technology called synchrotron microtomography, researchers from Pavol Jozef Šafárik University in Slovakia and Uppsala University in Sweden have managed to closely study the inner structure of bones, teeth, and soft tissues. This was then used to create a reconstruction of how the sauropods might have looked like before hatching. The findings of the research are reported in the journal Current Biology.
The scans were able to find tiny teeth nestled deeply in the embryo jaw sockets. They also found partly calcified elements of the braincase and what appear to be the remains of temporal muscles on the side of the skull.
The scans also revealed a number of unexpected features too. First up, the team were not anticipating the embryo to have binocular vision, as in eyes that are capable of facing the same direction. They were also surprised when it came to their teeth. Many modern egg-laying vertebrate animals, such as birds and crocodiles, hatch out of their egg with the aid of an “egg tooth” that’s used to peck away at the shell. However, it appears this species of dinosaur might have used a slightly different “tool”, opting for a thickened knobbly point found around its nose instead.
"The face appearance was most striking to me," Kundrat adds.
"Previous findings of titanosaurian skulls have shaped our imagination of their facial appearance, but looking at the egg is different. The eyes facing forward and a horn projecting from the snout make this overall head appearance bizarre to what we may expect," he said.