At Argentina’s Sanagasta Geological Park, there is a volcanic nursery for giants. It’s a site that is strewn with the fossilised eggs of giant dinosaurs – sauropods. Each of their 80 or so egg clusters sits next to a geyser, a hot vent or other volcanically heated sites. This is no coincidence – eggs need moisture and heat to incubate properly and big eggs are particularly demanding. These dinosaurs were using the planet to keep their babies warm.
Argentina is a haven for any palaeontologist looking for dinosaur eggs. Different provinces have yielded several large nesting sites. Most belonged to the giant sauropods and some even contain eggs with fossilised embryos inside. The sites have told us much about how dinosaurs looked after their young and even what ate baby dinosaurs but until now, scientists have largely ignored the question of why these particular sites were such inviting locations for expectant dinosaurs.
Snakes have been around for nearly 100 million years and scientists have found many fossils of extinct species. But this astonishing specimen is different. This serpent is Sanajeh indicus. It is sitting in a dinosaur nest and its coils surround three eggs and the body of a hatchling.
There are many reasons to think that this prehistoric tableau represented a predator caught in the act of hunting, rather than a mash-up of unconnected players thrown together by chance. The snake is perfectly posed, with its head resting atop a coil and its body encircling a crushed egg. All the pieces are very well preserved and very little of the snake, the dinosaur or the crushed egg have been deformed. All of this suggests that the animals were caught unawares and quickly buried in sediment.
The hatchling in question is a baby sauropod part of the dinosaur lineage that included the largest land animals of all time. It was probably a titanosaur, and being in India, that narrows things down to two known species – Isisaurus and Jainosaurus. The adults were formidable animals, 20-25 metres in length and protected by bony armour running down their backs. But even the largest dinosaurs must have hatched out of a small egg, and at that point, they were vulnerable. The hatchling that Sanajeh was about to dispatch was just 50 centimetres long, while the snake itself was measured 3.5 metres.
Despite this size discrepancy, the hatchling would still have been a substantial mouthful. Most modern snakes wouldn’t have any problem with that. Their lower jaws can unhinge to give them a massive gape and their flexible skulls are made of bones that can move against each other.
Sanajeh was halfway towards developing these specialisations. It didn’t have the fixed skulls and narrow gapes of the most primitive of modern snakes, nor could its maw open quite as wide as today’s record-breakers. Nonetheless, it could certainly swallow a sauropod infant and that ability earned Sanajeh inidcus its name. The words are Sanskrit for “ancient gape from the Indus”.