An ancient marine reptile graveyard in Nevada has intrigued scientists, leading them to believe it may have served as a birthing ground for ichthyosaurs approximately 230 million years ago. The Berlin-Ichthyosaur State Park (BISP) in the US has revealed the remains of at least 37 ichthyosaurs, large fish-shaped reptiles comparable in size to a school bus.

These creatures, which became extinct around 90 million years ago, appear to have migrated to this site, akin to the behavior of present-day blue and humpback whales.

Ichthyosaurs were a successful group of marine reptiles that thrived during the Triassic, Jurassic, and Cretaceous periods. Contrary to popular belief, they were distinct from dinosaurs and predated them. These reptiles evolved from land-dwelling ancestors that eventually returned to the sea. With speeds reaching up to 22 mph (36 kph) and lengths exceeding 20 meters (65 ft), ichthyosaurs were formidable creatures of the ancient oceans.

Numerous theories have been proposed to explain the mass accumulation of ichthyosaur fossils at the BISP site, including mass stranding events or toxin exposure from algal blooms. In a recent study published in Current Biology, researchers delved into Quarry 2 at BISP to investigate the circumstances surrounding the deaths of these creatures.

Through meticulous bone measurements, 3D modeling, and geochemical analyses, the researchers sought to unravel the mystery. Contrary to previous hypotheses, there was no conclusive evidence of volcanic eruptions or algal bloom toxins as causes of death. Geological evidence indicated that the ichthyosaurs likely sank to the seabed upon dying, dispelling the mass stranding hypothesis.

Interestingly, the site predominantly contained fossilized remains of adult ichthyosaurs, with scarce evidence of other vertebrates or juvenile specimens. Further examination uncovered tiny bones and teeth from embryonic and newborn ichthyosaurs, suggesting that the site may have functioned as a birthing ground rather than a feeding area.

Analogous to modern marine giants like whales, which migrate to warmer waters for breeding and birthing, it is believed that ichthyosaurs also exhibited such migratory behavior. This finding sheds light on the ancient ecological behaviors of marine reptiles, dating back over 200 million years.

Future research endeavors will extend to other ichthyosaur fossil sites across North America in an attempt to identify additional breeding or feeding grounds. This discovery underscores the enduring significance of the BISP site as a critical location in understanding the reproductive behaviors of prehistoric marine reptiles.