Titanosaur Embryo - New Discovery in Eye Position

A dinosaur egg fossil, smuggled from Argentina to the US about 20 years ago, contained an amazing specimen. Inside an egg, believed to be from a sauropod titanosaur, was a near-hatching embryo with a three-dimensionally preserved head.

This embryo surprised researchers in two ways:

• The eye sockets (orbits) were directed towards the front of the head.
  In adult sauropods, they should be facing sideways.
• A small horn was present on the tip of its snout.

Adult herbivorous titanosaurs, like modern herbivores (such as horses and elephants), have eyes on the sides of their faces. Eyes on the sides of the head provide a wide field of vision, allowing them to be aware of their surroundings and watch for predators.
The titanosaur embryo discovered, however, had both eyes on the front of its face. This is a characteristic of modern carnivores (like lions and bears). It is suitable for stereoscopic vision, which is excellent for judging distances to prey, at the expense of a wider field of view. This discovery has raised a significant mystery: why the titanosaur embryo (and likely the hatchling) prioritized stereoscopic vision over a wider field of view, and how the eye position changed as it grew into an adult.

The purpose of the other feature—the horn—is also not well understood, as no other sauropod species has been found with such a horn. Both the forward-facing eyes and the horn are not seen in adult titanosaurs. Future research is needed to determine if there is a connection between the eye position and the role of the horn.