Science, Tech, Math › Animals & Nature Therizinosaur Dinosaur Pictures and Profiles Share Flipboard Email Print Animals & Nature Dinosaurs Herbivores Basics Paleontologists Carnivores Dinosaurs & Birds Marine Reptiles Prehistoric Mammals Amphibians Birds Habitat Profiles Mammals Reptiles Wildlife Conservation Insects Marine Life Forestry Evolution View More By Bob Strauss Science Writer B.S., Cornell University Bob Strauss is a science writer and the author of several books, including "The Big Book of What, How and Why" and "A Field Guide to the Dinosaurs of North America." our editorial process Bob Strauss Updated July 02, 2019 Paleontologists are still trying to wrap their minds around therizinosaurs, the family of tall, pot-bellied, long-clawed, and (mostly) plant-eating theropods of late Cretaceous North America and Asia. On the following slides, you'll find pictures and detailed profiles of over a dozen therizinosaurs, ranging from Alxasaurus to Therizinosaurus. 01 of 13 Alxasaurus Wikimedia Commons Name: Alxasaurus (Greek for "Alxa desert lizard"); pronounced ALK-sah-SORE-us Habitat: Woodlands of Central Asia Historical Period: Middle Cretaceous (110-100 million years ago) Size and Weight: About 12 feet long and a few hundred pounds Diet: Plants Distinguishing Characteristics: Big gut; narrow head and neck; large claws on front hands Alxasaurus debuted on the world stage all at once: five specimens of this previously unknown therizinosaur were discovered in Mongolia in 1988 by a joint Chinese-Canadian expedition. This bizarre-looking dinosaur was an early precursor of the even goofier-looking Therizinosaurus, and its swollen gut shows that it was one of the very rare theropods to have enjoyed an entirely herbivorous diet. As fearsome as they looked, the prominent front claws of Alxasaurus were probably used for ripping and shredding plants, rather than other dinosaurs. 02 of 13 Beipiaosaurus Wikimedia Commons Name: Beipiaosaurus (Greek for "Beipiao lizard"); pronounced BAY-pee-ow-SORE-us Habitat: Woodlands of Asia Historical Period: Early Cretaceous (125 million years ago) Size and Weight: About seven feet long and 75 pounds Diet: Plants Distinguishing Characteristics: Feathers; long claws on front hands; sauropod-like feet Beipiaosaurus is yet another of those strange dinosaurs in the therizinosaur family: long-clawed, pot-bellied, two-legged, plant-eating theropods (most of the theropods of the Mesozoic era were devoted carnivores) that seem to have been constructed from bits and pieces of other types of dinosaurs. Beipiaosaurus appears to have been slightly brainier than its cousins (to judge by its slightly larger skull), and it's the only therizinosaur proven to have sported feathers, though it's highly probable that other genera did as well. Its closest relative was the slightly earlier therizinosaur Falcarius. 03 of 13 Enigmosaurus Wikimedia Commons Name: Enigmosaurus (Greek for "puzzle lizard"); pronounced eh-NIHG-moe-SORE-us Habitat: Woodlands of central Asia Historical Period: Late Cretaceous (75-65 million years ago) Size and Weight: About 20 feet long and 1,000 pounds Diet: Probably omnivorous Distinguishing Characteristics: Large claws on hands; strangely shaped pelvis True to its name--Greek for "puzzle lizard"--not much is known about Enigmosaurus, scattered fossils of which have been discovered in the parched deserts of Mongolia. This dinosaur was originally classified as a species of Segnosaurus--a bizarre, large-clawed theropod closely related to Therizinosaurus--then, on closer examination of its anatomy, was "promoted" to its own genus. Like other therizinosaurs, Enigmosaurus was characterized by is large claws, feathers and bizarre, "Big Bird"-like appearance, but much about its lifestyle remains, well, an enigma. 04 of 13 Erliansaurus Wikimedia Commons Name: Erliansaurus (Greek for "Erlian lizard"); pronounced UR-lee-an-SORE-us Habitat: Plains of central Asia Historical Period: Late Cretaceous (75-65 million years ago) Size and Weight: About 12 feet long and half a ton Diet: Plants Distinguishing Characteristics: Moderate size; long arms and neck; feathers The therizinosaurs were some of the ungainliest-looking dinosaurs ever to roam the earth; paleo-illustrators have depicted them as looking like everything from mutant Big Birds to oddly proportioned Snuffleupagi. The importance of the central Asian Erliansaurus is that it's one of the most "basal" therizinosaurs yet identified; it was slightly smaller than Therizinosaurus, with a comparatively shorter neck, though it retained the oversized claws characteristic of the breed (these were used to harvest leaves, another odd adaptation of therizinosaurs, the only theropods known to have pursued herbivorous diets). 05 of 13 Erlikosaurus Sergey Krasovskiy Name: Erlikosaurus (Mongolian/Greek for "lizard king of the dead"); pronounced UR-lick-oh-SORE-us Habitat: Woodlands of Central Asia Historical Period: Late Cretaceous (80 million years ago) Size and Weight: About 20 feet long and 500 pounds Diet: Plants Distinguishing Characteristics: Large size; large claws on front hands A typical therizinosaur--that breed of gangly, long-clawed, pot-bellied theropods that has long baffled paleontologists--the late Cretaceous Erlikosaurus is one of the few of its kind to have yielded a near-complete skull, from which experts have been able to infer its herbivorous lifestyle. This bipedal theropod likely used its long front claws as scythes, mowing down vegetation, stuffing it into its narrow mouth, and digesting it in its large, distended stomach (since herbivorous dinosaurs required copious amounts of intestines to process tough plant matter). 06 of 13 Falcarius Wikimedia Commons Name: Falcarius (Greek for "sickle bearer"); pronounced fal-cah-RYE-us Habitat: Woodlands of North America Historical Period: Early Cretaceous (130-125 million years ago) Size and Weight: About 13 feet long and 500 pounds Diet: Plants Distinguishing Characteristics: Long tail and neck; long claws on hands In 2005, paleontologists unearthed a fossil treasure trove in Utah, the remains of hundreds of previously unknown, medium-sized dinosaurs possessing long necks and long, clawed hands. Analysis of these bones revealed something extraordinary: Falcarius, as the genus was soon named, was a theropod, technically a therizinosaur, that had evolved in the direction of a vegetarian lifestyle. To date, Falcarius is only the second therizinosaur to be discovered in North America, the first being the slightly bigger Nothronychus. Given its extensive fossil remains, Falcarius has a lot to tell us about the evolution of theropods in general, and therizinosaurs in particular. Paleontologists have interpreted this as a transitional species between the plain-vanilla theropods of late Jurassic North America and the bizarre, feathered therizinosaurs that populated North America and Eurasia tens of millions of years later--most notably the giant, long-clawed, pot-bellied Therizinosaurus that inhabited the woodlands of Asia about 80 million years ago. 07 of 13 Jianchangosaurus Wikimedia Commons Name: Jianchangosaurus (Greek for "Jianchang lizard"); pronounced jee-ON-chang-oh-SORE-us Habitat: Woodlands of Asia Historical Period: Early Cretaceous (125 million years ago) Size and Weight: About 6-7 feet long and 150-200 pounds Diet: Unknown; possibly omnivorous Distinguishing Characteristics: Small size; bipedal posture; feathers During the early stages of their evolution, the strange dinosaurs known as therizinosaurs were virtually indistinguishable from the menagerie of small, feathered "dino-birds" that roamed North America and Eurasia during the early Cretaceous period. Jianchangosaurus is unusual in that it's represented by a single, exquisitely preserved, and nearly complete fossil specimen of a sub-adult, which betrays the similarity of this plant-eating theropod to its fellow Asian Beipiaosaurus (which was slightly more advanced) and the North American Falcarius (which was slightly more primitive). 08 of 13 Martharaptor Wikimedia Commons All we know for sure about Martharaptor, named after the Utah Geological Survey's Martha Hayden, is that it was a theropod; the scattered fossils are too incomplete to allow a more conclusive identification, though evidence points to its being a therizinosaur. See an in-depth profile of Martharaptor 09 of 13 Nanshiungosaurus Wikimedia Commons Name: Nanshiungosaurus (Greek for "Nanshiung lizard"); pronounced nan-SHUNG-oh-SORE-us Habitat: Woodlands of Asia Historical Period: Early Cretaceous (125 million years ago) Size and Weight: About 20 feet long and 500-1,000 pounds Diet: Probably omnivorous Distinguishing Characteristics: Long claws; narrow snout; bipedal posture Because it's represented by limited fossil remains, not much is known about Nanshiungosaurus besides the fact that it was a fairly large therizinosaur--the family of bizarre, bipedal, long-clawed theropods that may have pursued an omnivorous (or even strictly herbivorous) diet. If it winds up meriting its own genus, Nanshiungosaurus will prove to be one of the largest therizinosaurs yet discovered, on a par with the genus, Therizinosaurus, that gave its name to this poorly understood group of dinosaurs in the first place. 10 of 13 Neimongosaurus Wikimedia Commons Name: Neimongosaurus (Mongolian/Greek for "inner Mongolian lizard"); pronounced nigh-MONG-oh-SORE-us Habitat: Woodlands of central Asia Historical Period: Middle Cretaceous (90 million years ago) Size and Weight: About seven feet long and 100 pounds Diet: Plants Distinguishing Characteristics: Long neck; long claws on front hands In most respects, Neimongosaurus was a typical therizinosaur, if these bizarre, pot-bellied theropods can be described as "typical." This presumably feathered dinosaur had the big belly, small head, ridged teeth, and oversized front claws common to most therizinosaurs, a collection of traits that points to a herbivorous, or at least an omnivorous, diet (the claws were probably used for ripping and shredding vegetable matter rather than smaller dinosaurs). As with others of its breed, Neimongosaurus was closely related to the most famous therizinosaur of them all, the eponymous Therizinosaurus. 11 of 13 Nothronychus Getty Images Name: Nothronychus (Greek for "sloth claw"); pronounced no-throw-NIKE-us Habitat: Southern North America Historical Period: Middle-Late Cretaceous (90 million years ago) Size and Weight: About 15 feet long and 1 ton Diet: Plants Distinguishing Characteristics: Long arms with long, curved claws; possibly feathers Demonstrating that surprises can lay in store for even the most experienced dinosaur hunters, the type fossil of Nothronychus was discovered in 2001 in the Zuni Basin on the New Mexico/Arizona border. What made this find especially significant is that Nothronychus was the first dinosaur of its kind, a therizinosaur, to be dug up outside Asia, which has prompted some quick thinking on the part of paleontologists. In 2009, an even bigger specimen--which has been assigned its own species under the Nothronychus umbrella--was unearthed in Utah, and later came the discovery of yet another therizinosaur genus, Falcarius. As with other therizinosaurs, paleontologists speculate that Nothronychus used its long, curved claws much like a sloth, to climb trees and gather vegetation (although they're technically classified as theropods, the therizinosaurs seem to have been strict plant-eaters, or at the very least pursued omnivorous diets). However, additional information about this obscure, pot-bellied dinosaur--such as whether it sported primitive feathers--will have to await future fossil discoveries. 12 of 13 Segnosaurus Wikimedia Commons Name: Segnosaurus (Greek for "slow lizard"); pronounced SEG-no-SORE-us Habitat: Woodlands of Central Asia Historical Period: Middle Cretaceous (90 million years ago) Size and Weight: About 15-20 feet long and 1,000 pounds Diet: Probably omnivorous Distinguishing Characteristics: Squat trunk; muscular arms with three-fingered hands Segnosaurus, scattered bones of which were discovered in Mongolia in 1979, has proven an elusive dinosaur to classify. Most paleontologists lump this species in with Therizinosaurus as a (no surprise here) therizinosaur, based on its long claws and backward-facing pubic bones. It's not even certain what Segnosaurus ate; lately, it has been fashionable to portray this dinosaur as a kind of prehistoric anteater, tearing apart insect nests with its long claws, though it may also have gobbled up fish or small reptiles. A third possibility for the Segnosaurian diet--plants--would upend established ideas about dinosaur classification. If Segnosaurus and other therizinosaurs were in fact herbivores--and there's some evidence to this effect based on these dinosaurs' jaw and hip structure--they would be the first such theropods of their kind, which would raise many more questions than it answered! 13 of 13 Suzhousaurus Wikimedia Commons Name: Suzhousaurus (Greek for "Suzhou lizard"); pronounced SOO-zhoo-SORE-us Habitat: Woodlands of Asia Historical Period: Early Cretaceous (125 million years ago) Size and Weight: About 20 feet long and 500 pounds Diet: Probably omnivorous Distinguishing Characteristics: Bipedal posture; long claws on hands Suzhousaurus is the latest in a continuing series of therizinosaur discoveries in Asia (typified by Therizinosaurus, these bizarre dinosaurs were characterized by their long, clawed fingers, bipedal stances, pot bellies, and general Big Bird-like appearance, including feathers). Along with the similarly sized Nanshiungosaurus, Suzhousaurus was one of the earliest members of this strange breed, and there's some tantalizing evidence that it may have been an exclusive herbivore (though it's also possible that it pursued an omnivorous diet, unlike most of its fellow, strictly carnivorous theropods).