Therizinosaurs (or segnosaurs) are theropod dinosaurs belonging to the clade Therizinosauria. Therizinosaur fossils have been found in Early through Late Cretaceous deposits in Mongolia, the People’s Republic of China and Western North America. Various features of the forelimbs, skull and pelvis unite them quite comfortably, both as theropods and, as maniraptorans, close relatives to birds.
The name therizinosaur is derived from the Greek therizo meaning ‘to reap’ or ‘to cut off’ and sauros meaning ‘lizard’. The older name segnosaur is derived from Latin segnis meaning ‘slow’ or ‘sluggish’ and Greek sauros meaning ‘lizard’. Therizinosaurs had a very distinctive, often confusing set of characteristics. Their long necks, wide torsos, and hind feet with four toes used in walking resembled prosauropod dinosaurs. Their unique hip bones, which pointed backwards and were partially fused together, initially reminded paleontologists of the “bird-hipped” ornithischians. Among the most striking characteristics of therizinosaurs are the enormous claws on their hands, which reached lengths of three feet in Therizinosaurus. The unusual range of motion in therizinosaur forelimbs, which allowed them to reach forward to a degree other theropods could not achieve, also supports the idea that they were mainly herbivorous. Therizinosaurs may have used their long reach and strongly curved claws to grasp and shear leafy branches, in a manner similar to the prehistoric ground sloths.
Skin impressions from Beipiaosaurus indicate that therizinosaurs were covered with a coat of primitive, down-like feathers similar to those seen in the compsognathid Sinosauropteryx, as well as longer, simpler, quill-like feathers that may have been used in display.Therizinosaurs spanned a large range of sizes, from the small Beipiaosaurus (which measured 2.2 m, or 7.3 ft in length), to the gigantic Therizinosaurus, which at an approximate 10–12 m (33–40 ft) long and an estimated weight of 6.2 tonnes, was among the largest known theropods.The function of such large claws is still unknown How ever it is speculated that they could have been used for foraging and/or display. Discovered shortly after world war II in Mongolia . With only a few bones to go by the Soviet/Mongolian excavation team thought they uncovered a killer turtle. One of the interasting thaings about the therizinosaurs is that scientist can’t deside were to put them in the dinosaur family. although theropods are certainly the closest fit.it was once thought that these dinosaurs were closely related to prosauropods, the sometimes bipedal, sometimes quadrupedal herbivores that preceded the sauropods of the late Jurassic period. Until the the discovery of the middle Cretaceous Alxasaurus an ancient therizinosaur with some distinctly theropod-like characteristics.The theory know is the evolution put them on a different direction from a primitive branch of the theropod family.
|For biologist’s it’s not what they looked like it’s what they ate. Theirs an interesting cases for these dinosaurs a) used their long front claws to slice and dice vegetable matter (since they would have been too ungainly to slash fellow dinosaurs), and b) harbored an extensive network of intestines in their prominent pot bellies, an adaptation that would only have been needed in order to digest tough vegetable matter. One conclusion is that therizinosaurs (distant relatives of the prototypically carnivorous Tyrannosaurus Rex) were largely herbivorous, in much the same way that prosauropods (distant relatives of the protopically plant-eating Brachiosaurus) supplemented their diets with meat.