Baby Giants

Patagonia, Argentina

80,000,100 BC

Early Campanian stage of the Late Cretaceous period

In what is now the Neuquen basin in northwestern Argentina lies a wide river floodplain, cut off from the Pacific Ocean by the growing Andean mountain chain with numerous active volcanoes to the west due to subduction activity. The climate veered sharply between semi-arid and subhumid conditions. Rapid weathering and erosion of the rising Andes resulted in huge volumes of sediment being carried east by rivers flowing in the region. Combined with climate change, this caused periodic floods of silt-laden material across the region, laying down layers of clay that buried and "sealed" the landscape. 

But in this floodplain, the circle of life occurs. A herd of sauropod dinosaurs called titanosaurs congregate together to lay their eggs in this region a square mile. They habitually migrate to favor the region as a kind of rookery. Each year, they became pregnant and lay their eggs in the same time and region. Most of them lay clutches of between 20 and 40 football-sized eggs, apparently laid in piles in shallow pits, some in 3-foot hollows, with plants for incubation. Once they're done, the mother dinosaurs leave their young to fend for themselves (40 feet from snout to tail and weighing around 7 tons, a full-grown titanosaur would be too large and dangerous to do any parental care to the young).  

Over time, the embryos inside the eggs begin to grow, and once they're developed it was time to hatch. With a tiny structure known as an egg tooth, the baby titanosaurs begin to break out of the eggs and have their first glimpse into their inhospitable world. With well-developed teeth for feeding and long legs for walking, the little dinosaurs will wonder off and forage on their own. In a just a few decades, they will grow as big and massive as their parents that reproduce them and they may even one day reproduce their own babies in the same site where they're born.

But the chances of survival varies for these little dinosaurs. At 10-inches long, a baby titanosaur would often be easy prey to predators that stalk the floodplains. But if predation isn't enough, then mother nature will take charge of their future of both the young and the eggs. The periodic floods of silt-laden material, due to rapid weathering, the erosion of the rising Andes, and climate change, lay down  layers of clay and bury the eggs and drowning the embryos within them. Sealing them for the next 80 million years. 

Today, these sedimentary strata have been re-exposed at the surface and reveal their secrets that reveal rare evidence about the social behavior of dinosaurs.

The discovery of the site began in 1997 when a team from the American Museum of Natural History in New York City, led by paleontologists Luis Chiappe and Lowell Dingus, arrived there in search of ancient fossilized birds. However they soon realized that the 'rock' fragments scattered across the desert site were tiny eggshells, complete eggs, and nests within a fossilized hatchery, laid bare by modern weathering. They did not come from birds, they come from sauropod dinosaurs. 

Since then, thousands of clutches of sauropod eggs have been found mapped, revealing a site that covers several square miles of the Anacleto Formation. The nesting site can be traced down to depths of some 280 feet below the surface of sand, silt, and mud, containing four distinct fossil egg-bearing layers beneath the silt and mud.

The nesting site is dubbed Auca Mahuevo, meaning "more eggs".

This site is important, because it gives us a unique glimpse into the social and nesting behavior of sauropod dinosaurs.

The distribution of fossils show that large sauropod dinosaurs congregate together to lay their eggs in the same area. One location has more than 500 eggs within 700 square feet and another had an average of 11 eggs roughly one per square foot. The average density of one clutch per 160-250 square feet suggests that, on each occasion, the female dinosaurs all became pregnant and laid their eggs at about the same time, presumably for favorable conditions for hatching and early development of the young. The presence of dense associations of egg mounds and clutches shows that the dinosaurs were in rookeries in a similar behavior seen in modern-day birds, turtles, and crocodiles. But due to their large size and the proximity of the clutches show that little or no parental care would take place and the lack of trampling show that the mother dinosaurs leave their babies to fend for themselves.

Amazingly, in 2001, a study of just a few surviving intact eggs found that they even contained fossil embryos, whose skul characteristics allowed them to be identified as titanosaur sauropods. A few skin impressions have been preserved and these show nodule-like patterns of non-overlapping scales similar to those found generally in dinosaurs. Their articulated jaws, peg-like teeth, and tiny nostrils were also preserved.

The discovery of Auca Mahuevo gives us a unique view of the nursing of some of the largest animals that ever lived.

Note: This is made during my mom's birthday.

The egg-tooth in titanosaurs was from Gregory S. Paul's book, "The Princeton Field Guide to Dinosaurs"