A nest of 15 baby Protoceratops andrewsi, sheep-sized herbivorous horned dinosaurs related to Triceratops, fossils has been discovered in Mongolia’s Gobi Desert. Mongolian paleontologist Pagmin Narmandakh found the 2.3-foot-wide nest, the first Protoceratops nest ever discovered. Nests of fossilized eggs thought to be Protoceratops were found in Mongolia in the 1920s by naturalist Roy Chapman Andrews, but when the eggs were opened they turned out to be Oviraptors (dinosaurs that fed on other dinosaurs’ eggs).

The babies are not newborns. They are 4 to 6 inches long and were probably about a year old when they met their sad fate about 75 million years ago.

“The evidence suggests they may have been overrun by migrating dunes during a sandstorm,” researcher David Fastovsky, a vertebrate paleontologist at the University of Rhode Island, told LiveScience.

The searing hot locale in the heart of the Gobi Desert where this nest was discovered, Tugrikin Shire, has proven rich in fossils in the past, including the “fighting dinosaurs,” an entombed Velociraptor and Protoceratops seemingly locked in mortal combat. The site was harsh back when these dinosaurs were alive, too — the sandstones they were buried in suggest the region was an erg, a windblown dune field a bit like parts of the modern Sahara. The dunes here might once have reached as tall as 80 feet (24 meters).

The relatively advanced age of the babies suggests that Protoceratops cared for their young. For them all to be still living together in the nest beyond the first few days they had to have an adult feeding and protecting them, especially considering how harsh the desert environment was even during the Late Cretaceous. Fastovsky notes that 15 is a large number of babies for one nest, which suggests that mortality may have been high so they hatched as many eggs as they could to increase the chances of a next generation surviving.

Also, since protoceratopsidae were early members of the ceratopsian group of dinosaurs, evidence of parental care in Protoceratops implies that this may have been a feature of the wider group as it continued to develop larger and more formidable neck-frilled, horn-beaked beasts like Triceratops.