Therizinosaurus is a genus of very large therizinosaurid that lived in Asia during the Late Cretaceous period in what is now the Nemegt Formation around 72.1 million years ago to 66 million years ago. It contains a single species, Therizinosaurus cheloniformis. The first remains of Therizinosaurus were found in 1948 by a Mongolian field expedition at the Gobi Desert and later described by Evgeny Maleev in 1954. The genus is only known from a few bones, including gigantic manual unguals, from which it gets its name, and additional findings comprising fore and hindlimb elements that were discovered from the 1960s through the 1980s.
Therizinosaurus
Holotype unguals PIN 551–483 at the Moscow Paleontological Museum; note left ungual cast
Arms of specimen MPC-D 100/15 with unguals 100/16 and 100/17 at CosmoCaixa Barcelona
Composite skeletal of the known remains of Therizinosaurus
Therizinosauridae is an extinct family of derived (advanced) therizinosauroid dinosaurs whose fossil remains have been found in mostly Late Cretaceous boundary. Even though representative fossils have only been found throughout Asia and North America, the range of Therizinosauridae is believed to have spanned much of the supercontinent of Laurasia based on several footprints and isolated remains in Europe and Africa. Currently, Therizinosauridae comprises eight described and named taxa.
Therizinosauridae
Holotype claw cast of Therizinosaurus (PIN 551–483)
Frontal view of the arms in Therizinosaurus IGM 100/15
Skeletal composite of two specimens of Alxasaurus