Paleontologists recently found well-preserved dinosaur eggs in an enormous nesting ground of titanosaurian sauropod dinosaurs that lived about 80 million years ago (Cretaceous period) in what is now Patagonia, Argentina. In a paper in the journal Current Biology, they now describe an almost intact embryonic skull from one of these eggs, which shows that titanosaurian dinosaurs had stereoscopic vision and an unusual elongated horn on the front of the face which was then lost in adulthood.

Magnified perspective of the titanosaurian embryonic skull with the preorbital and orbital region in left lateral view. Image credit: Kundrat et al, doi: 10.1016/j.cub.2020.07.091.

“The specimen represents the first 3D preserved embryonic skull of a sauropod sauropodomorph,” said lead author Dr. Martin Kundrat, a researcher at Pavol Jozef Šafárik University.

“The most striking feature is head appearance, which implies that hatchlings of giant dinosaurs may differ in where and how they lived in their earliest stages of life.”

“But because it differs in facial anatomy and size from the sauropod embryos of Auca Mahuevo, Patagonia, we cannot rule out that it may represent a new titanosaurian dinosaur.”

“The preservation of embryonic dinosaurs preserved inside their eggs is extremely rare,” said co-author Dr. John Nudds, a researcher at the University of Manchester.

“Imagine the huge sauropods from Jurassic Park and consider that the tiny skulls of their babies, still inside their eggs, are just a couple of centimeters long.”

Dr. Kundrat, Dr. Nudds and their colleagues used an imaging technology called synchrotron microtomography to study the inner structure of bones, teeth, and soft tissues of the embryonic dinosaur.

The scans allowed the scientists to find hidden details, including tiny teeth preserved deeply in tiny jaw sockets.

They also found partly calcified elements of the embryonic braincase and what appear to be the remains of temporal muscles.

They also reconstructed the most plausible appearance of the skull in titanosaurian sauropods before hatching.

Their findings suggest that the baby sauropods may have hatched out of the egg with the help of a thickened prominence rather than a boney egg-tooth.

Kundrat et al describe an almost intact embryonic skull, which indicates the early development of stereoscopic vision, and an unusual monocerotic face for a sauropod dinosaur. The fossil also reveals a neurovascular sensory system in the premaxilla and a partly calcified braincase, which potentially refines estimates of its prenatal stage. The embryo was found in an egg with thicker eggshell and a partly different geochemical signature than those from the egg-bearing layers described in Auca Mahuevo, Patagonia, Argentina. Image credit: Kundrat et al, doi: 10.1016/j.cub.2020.07.091.

The study authors also uncovered evidence that the embryonic dinosaurs used calcium derived from the eggshell long before they were ready to hatch.

They found that the titanosaurian hatchlings emerged with a temporary moncerotid (single-horned) face, retracted openings on the nose (nares) and early binocular vision.

“We suggest an alternative head appearance for babies of these Patagonian giants,” Dr. Kundrat said.

“We were able to reconstruct the embryonic skull prior to hatching,” Dr. Nudds said.

“The embryos possessed a specialized craniofacial anatomy that precedes the post-natal transformation of the skull in adult sauropods.”

“Part of the skull of these embryonic sauropods was extended into an elongated snout or horn, so that they possessed a peculiarly shaped face.”

Source: sci.news