Therizinosaurus, meaning ‘scythe lizard’, is one of the most unusual dinosaurs known to science. This massive, two-legged theropod, which lived during the Late Cretaceous period, possessed long claws on each of its three-fingered hands, reaching lengths over 50 centimeters. Despite its intimidating appearance, this dinosaur was a herbivore, using its elongated claws to pull vegetation within reach for consumption.
The Primary Discovery Site
The initial discovery of Therizinosaurus remains occurred in 1948 during a Mongolian field expedition led by the USSR Academy of Sciences in the Gobi Desert region of Southwestern Mongolia. The fragmentary fossils primarily consisted of gigantic claw bones, which were unlike anything previously encountered, presenting a puzzle to early paleontologists.
In 1954, Russian paleontologist Evgeny Maleev formally described these peculiar fossils. Maleev initially misinterpreted them, suggesting they belonged to a large, turtle-like reptile that might have used its massive claws to harvest seaweed in an aquatic environment. The specific name “cheloniformis,” derived from “cheloni” meaning turtle, reflects this original, albeit incorrect, interpretation.
Unearthing the Nemegt Formation
The Nemegt Formation in the Gobi Desert became the primary geological source for Therizinosaurus remains, yielding the most significant fossil finds. This formation dates to the Late Cretaceous period, specifically the Maastrichtian stage, approximately 70 million years ago. Its sedimentary layers, composed of mudstones and sandstones, reveal an ancient environment characterized by river channels, extensive floodplains, and ancient lakes. This landscape likely supported woodlands and riparian areas with dense forest cover, as indicated by petrified tree trunks.
The successive Soviet-Mongolian paleontological expeditions, conducted from the late 1940s through the 1980s, systematically explored the Nemegt Formation. These expeditions uncovered more complete skeletal elements beyond just the claws. Discoveries of forelimb and hindlimb components helped scientists piece together a more accurate picture of this enigmatic dinosaur. These later finds allowed for the reclassification of Therizinosaurus as a theropod dinosaur, despite its plant-eating diet, confirming its unique evolutionary path.
Why This Location Matters
The Nemegt Formation’s geological characteristics contribute to its paleontological importance, extending beyond merely being the discovery site. The depositional environment, rich in fine-grained sediments from ancient river systems and lakes, created ideal conditions for exceptional fossil preservation. This geological setting often led to the burial of articulated skeletons, providing more complete and informative specimens than isolated bones. Such preservation quality aids in reconstructing the anatomy and lifestyle of extinct creatures.
Fossil evidence from the Nemegt Formation offers a detailed window into the Late Cretaceous ecosystem that Therizinosaurus inhabited. The presence of diverse flora, including araucarian conifers, ginkgos, and various angiosperms, indicates a productive environment capable of sustaining large herbivores. This rich habitat also supported a wide array of co-existing fauna, including fish, turtles, crocodilians, and other dinosaurs, such as the large predatory Tarbosaurus. Studying this location allows paleontologists to understand the complex interactions within this ancient world and Therizinosaurus’s role within it.