Rapetosaurus’ shape at hatching indicates that unlike duckbills, the hatchlings of titanosaurs needed very little parental care. They were precocial babies like those of a modern ostrich, able to run around, play and feed themselves straight after hatching. Named for a mischievous mythical giant in local lore, Rapetosaurus is one of the most completely known titanosaurs. It is known from very well preserved remains, including the skull, which is a rare find for any titanosaurs. It was named and described by Rogers herself in 2001, who estimates the adult at 15 meters long, with its head roughly 8 meters in the air. It was easily the biggest creature in its environment, the seasonal and drought-prone island of Madagascar. For now, it is our best look at how these creatures grew up.
Titanosaurs are the last and among the biggest of the sauropods, the famous long-necked and large-bodied herbivorous dinosaurs. They populated every continent and lived until the end of the dinosaur age, around 66 million years ago. The titanosaurs were very robust and often armored with bony plates and spikes. They were also the biggest animals to ever live on land. The largest of these already gargantuan creatures weighed an excess of 70 tons. Yet all this size came from very small eggs, mostly no larger than a soccer ball. Any larger than this, and the hard shells would have been too thick for the babies to break out of, or even breathe through.
Thanks to several hundred fossilized titanosaur eggs, paleontologists are fairly confident about how titanosaurs bred. The most famous titanosaur nesting site is the Argentinian nesting ground of Auca Mahuevo. This site was uncovered in the Mid to Late Cretaceous Neuquen Group, a long-running series of rock beds that cover a large area of the country’s Patagonia region. Auca Mahuevo was first discovered by paleontologist Luis Chiappe and colleagues in 1998.
The eggs were found in four rock layers, and were spherical structures laid in clutches between 15 and 40. It was thought that the eggs had been laid next to a stream or freshwater channel. In reality though, the eggs had been swamped by episodes of flood, thus leaking in through pores in the shells and suffocating the babies inside.
Other sites in Argentina include one recently discovered in Sanagasta. Here, paleontologists have found a species of titanosaur using a very different nesting strategy from those at Auca Mahuevo, which are essentially group nesters laying in scooped-out nests. It had been depositing its eggs a geothermal area, similar to the places in which geysers are found. Another species in Spain had been actively building nests or nest-like structures out of surrounding vegetation, just like megapodes today. Megapode birds are a family of Australasian gamebirds, known not just for laying in burrows but also for building massive nests of rotting vegetation over their eggs. The vegetation slowly turned to compost through the actions of microorganisms, thus generating heat that the eggshells can absorb.
Thus it is clear that while they did not invest much care in their offspring’s development, titanosaur mothers were certainly doing something right. These selective nesting behaviors certainly varied among species, and many more might yet be discovered. Despite these protective measures, female titanosaurs still had other issues to contend with: Nest predation. In 2010, an astonishing new find from India’s Lameta Formation revealed one such predator. It was not a predatory dinosaur but a primitive snake known as Sanajeh indicus. The snake resembled a modern-day boa constrictor and at 3.5 meters long, was similar in size and lacked venom. Its gape however, was somewhat less than that of present boas and pythons and it could not unhitch its jaws to swallow massive prey.
Sanajeh’s bones were found in the remains of a titanosaur nest containing three crushed eggs, with the fossil of a 50-centimeter hatchling preserved alongside it. It is uncertain as to what genus the titanosaur represents. What is clear though is that the snake had died while in the act of preying on the eggs and possibly the babies of these huge dinosaurs. And there was not just one nest with snake fossils in it. Instead, there are three titanosaur nests, each associated with Sanajeh remains in this one locality. This suggests that not only were these snakes preying on baby titanosaurs, they may also have been specialized raiders that lived in the nesting sites and nests themselves.
References
Hechenleitner et al. (2015) What do giant titanosaur dinosaurs and modern Australasian megapodes have in common?
Curry Rogers et al. (2016) Precocity in a tiny titanosaur from the Cretaceous of Madagascar
Wilson et al. (2010) Predation upon Hatchling Dinosaurs by a New Snake from the Late Cretaceous of India
Vasika
Udurawane
Writer
