A rare egg fossil with an unbroken dinosaur suggests that baby sauropods were not miniature versions of the four-legged, long-necked hats that we all know and love, exhibit a unique set of physical characteristics that are a bit uplifting rhino-like horn.
Baby titanosaurs – the largest group of sauropods – contained a prominent horn and a pair of forward-facing eyes that enabled stereoscopic vision, according to new research published today in Current Biology. These facial features eventually disappeared when the babies were grown into adults, but not before they served a valuable purpose, the authors speculate, led by Martin Kundrat of Pavol Jozef Šafárik University in Slovakia.
“Titanosaur dolls were on their own right after coming out,” Kundrat explained in an email. “They had to search for their food and defend themselves – two of the most important survival activities.”
Indeed, life in the late Cretaceous could not have been easy for these hatcheries. Therefore, it would have been wise for them to hide in a forest-like environment until they were large enough to live in the open, said Kundrat. The baby titans, with their stereoscopic vision, were better able to get food and recognize danger. But its most striking feature – its beak-like preformed horn – could be used to search for food and possibly even for defense.“At least for the period when they were most vulnerable,” Kundrat said.
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These findings were made possible by analyzing a rare egg fossil found in Patagonia, Argentina. Or at least that’s where Kundrat and his colleagues are believe the fossil came out. They can not really be sure, because the fossil was illegally exported from the country.
In 2001, an Argentine dealer brought the egg to Terry Manning, a freelance paleontologist and co-author of the new study. During a follow-up meeting in 2015 with study author John Nudds of the University of Manchester, the dealer said the fossil came from the Allen formation of Bajo de Santa Rosa in the province of Rio Negro, Patagonia. The 80-million-year-old egg fossil has since been returned to a museum in Argentina, but its geographical origins are still unclear.
The first fossil sauropod eggs were found 25 years ago at Auca Mahuevo in Patagonia, the page of a previous titanosaur nest soil. Fossil eggs with embryonic remains are extremely rare, and there are many that we do not know about the developmental stages of these animals. The newly analyzed fossil is unique in that it is the best three-dimensionally preserved embryonic skull belonging to a sauropod dinosaur, according to the paper. Unfortunately, other parts of the dinosaur were not recovered, and the exact species to which it belonged could not be determined.
To study the fossil, the researchers took it to the European Synchrotron Radiation Facility in France.
“The synchrotron is a particle accelerator that generates powerful X-ray images called synchrotron light,” Kundrat explained. “This synchronous light can penetrate high-density objects, such as rocks and dinosaur eggs. Synchrotron microtomography is currently the leading imaging technology for working with fossils that are outside the scanning capacity of industrial micro-CT systems. ”
These scans reveal previously hidden features, such as the internal structure of the bones, teeth and even soft tissue of the embryo. These data were subsequently used to reconstruct the skull, which is 1.2 inches (3 centimeters) long, and revealed the unexpected facial features.
“Part of the head of these embryonic sauropods was expanded into an elongated snout or horn so that they had a peculiarly shaped face,” Nudds said in a press release from the University of Manchester.
Remarkably, this rhinoceros horn could be a kind of “egg-tooth” that helped the baby by breaking his egg when it broke out.
A fascinating study, no doubt, but there are some important limitations to note.
As already mentioned, the researchers are not completely sure about where the fossil comes from. This is more of an annoyance than a warning, but it makes the dating of the fossil a bit precarious.
More serious limitations include the complete absence of the animal’s body en of supporting fossils, including extended baby titanosaurs. Indeed, given the fact that we do not know how long these sauropod embryos have developed in their eggs, it is difficult to assess how much these prenatal [characteristics] remained expressed in cranial morphology at discharge, ‘the authors wrote in the study. It is possible that this embryo was still subject to major evolutionary changes prior to hatching, so it may not be representative of baby titanosaurs in general.
Kundrat said more evidence is needed to find out if the unusual face of this specimen also applies to other titanosaurus embryos and clicks. Fortunately, more fossil eggs of sauropods have been found in Argentina, which may contain traces of embryos. Kundrat and his colleagues have made a very cool discovery, which has led to some very interesting, albeit speculative, conclusions. The good news is that these are all very testable things – we just need some more fossils.
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