When I first read the news article on the Titanosaur/Sauropod egg and the embryo inside, I was completely fascinated. When I read further about the findings from the study of the egg, I was amazed both at the methods of investigation and in what the authors of the study presented about the embryo.
The egg is believed to have been a Titanosaur, several types of Sauropod which that lived in the area where the egg was discovered in what is now Argentina. A cast/fossil of one of these Sauropods, Maximo the Titanosaur, is now on display in the Field Museum in Chicago. It has taken the place on the main floor of where Sue, the largest and most complete Tyrannosaurus Rex (T-Rex) skeleton ever found use to stand. Sue is now in the second-floor dinosaur exhibit of the Field Museum.
A comparison of the completeness of the two fossils, Maximo and Sue, is interesting. The bones comprising Sue’s fossil (it is named for the discoverer of the fossil; the sex of the dinosaur is unknown) compromise approximately 90% of the mass of a complete T-Rex skeleton. By contrast, the skeleton of Maximo the Titanosaur is made from casts of fossilized bone found at several sites, and of some sculpted bones where no reference bone is available. There were about 130 fossilized bones found, not just from one Titanosaur but from six different individuals.
The initial scientific article in Current Biology on the egg and its investigation, examines several interesting aspects of the dinosaur’s life. The embryo was approximately 80% of its in ovo, inside the egg, development before it was ready to hatch out. The examination of the embryonic fossil indicates that the tiny dinosaur had what is commonly known as an “egg-tooth.” An egg-tooth is used by a young bird as it hatches to break open the shell of the egg in which it is enclosed and protected. The egg tooth later falls off once the young bird is out of its eggshell.
Another finding of the study can be understood by picturing a rabbit. A rabbit’s skull is quite narrow, and its eyes are situated well back on the sides of its skull. The rabbit is preyed on by many other animals including mammals, large birds, and snakes. The position of the rabbit’s eyes gives it the ability to have a field of vision well beyond the field of vision of a human. While our human peripheral vision from the side of our eyes allows us to see approximately to the line of our shoulder, the placement of a rabbit’s eyes allow it a field of vision well past its shoulder. The rabbit’s field of vision reaches beyond 45 degrees past its shoulders on each side. This allows them to see a predator sneaking up on them from the sides and from their rear. This is similar to what is known about the placement of eyes sockets on adult Sauropod skeletons. They also had predators that they had to watch out for.
In the study it was found that the embryo’s eye placement was more forward giving it more of a three-dimensional vision to the front. It’s not that these tiny creatures did not have predators. I imagine the predation of the new hatchlings was very high. But when they first emerged from their egg, their eyes were forward looking. Perhaps this helped them to be better able to learn to stand and walk in a straight line and to see food such as a blade of grass or a seedling tree right in front of them. But as time went on and as their body and their skull expanded, their eyes moved to the side of their skull which created a field of vision more like that of a rabbit.
The growth of the Titanosaurs was amazing. In the art at the beginning of this article, I have tried to capture a size comparison of the adult Titanosaurs to a modern human and to the fossilized egg shown as the round ball next to the human figure.
In this study the fossilized egg was approximately 10 inches in diameter. I postulate that an embryo was likely about twelve inches long when it emerged from its egg. When compared, a modern ostrich egg is more egg-shaped, the dinosaur egg being studied was more spherical. A modern Ostrich egg is approximately 10 inches long and 5 to 7 inches in diameter. The hatchling Ostrich is generally the size of a chicken. It will grow to be upwards of 8 feet tall.
The hatchling Titanosaur by contrast is assumed to be 10 to 12 inches tall at the shoulder. It would have grown to be 20 times that high at the shoulder. It will also grow to be over 120 feet long and weigh 140,000 pounds (70 tons).
The last bit of the story also speaks to the truth of modern science. At one time fossils were stolen in the field from one team of paleontologists by another team representing a different museum or university. Fossils were sometimes destroyed in the field to keep rival museums from retrieving them. Today museums and landowners and discoverers often work together to improve our knowledge of these ancient beasts and the world they lived in. There may be court cases to determine ownership or partial rights of ownership to a fossil. This allows the courts to decide the question of ownership and the fossil can be recovered and displayed and studied and enjoyed. In the case of the fossilized egg and its embryo, the fossil had been removed from Argentina illegally. When this became known to the research team, the fossil was returned to Argentina. The fossil is now housed at the museum, Museo Municipal “Carmen Funes,” in Plaza Huincul, Neuquén Province, Argentina.
Fascinating.
The picture of the herd of titanosaur sauropod Argentinosaurus is by artist Miguel Angel Amorin Fernandez. It is copied from a page in “palenontologyworld_com”, it may be found at https://www.instagram.com/p/B00DxYblpOd/?igshid=dbe23rmt94sf .
The picture of the embryo of the Titanosaur sauropod inside its egg is copied from the article, “Specialized Craniofacial Anatomy of a Titanosaurian Embryo from Argentina”, Martin Kundrat et al, published August 27, 2020 in the journal Current Biology.
The pictured size comparison of the human (at 5 feet 6inches) and the sauropod Argentinosaurus (shoulder height 20 feet) is based on the scale presented in the article “Titanosaur” that may be found at https://www.britannica.com/animal/titanosaur.
The initial news article I read on this fascinating subject was an online article in CNN. It may be found at https://www.cnn.com/2020/08/27/world/sauropod-dinosaur-embryonic-skull-scn-trnd/index.html . The pictured comparison of the size of a titanosaur egg (approximately 8 inches in diameter) is based on the comparison to an Ostrich egg in that article.
The article about Sue the T-Rex may be found on the website of the Field Museum of Chicago at https://www.fieldmuseum.org/blog/sue-t-rex .
The difference between the complete skeleton of Sue, and the mostly Cast skeleton of Maximo the Titanosaur is discussed in an article on the website of the Field Museum of Chicago may be found at https://www.fieldmuseum.org/blog/which-dinosaur-bones-are-real .
The website for the museum Museo Municipal “Carmen Funes,” Plaza Huincul, Neuquén Province, Argentina may be found at https://www.interpatagonia.com/cutralco-huincul/carmen-funes-municipal-museum.html .