was larger than the ischium and pubis, having very deflected and pronounced iliac blades. The prominent extension of the ilium shows that therizinosaurids had massive thighs. On the bottom of the ischium, a large obturator process (ridge-like expansion) was present, most notably in Segnosaurus and Nothronychus. The pubis was larger than the ischium and had a large pubic boot (wide expansion at the end). Unlike any other theropod group, the pubis and ischium were attached together forming a solid structure with a square end. Both femur and tibia were robust in constitution. The former was relatively straight with well-developed articulations and femoral head. The tibia was slightly shorter than the femur and had a wide lower end, forming a prominent ankle. The fibula was pinched to the bottom and very stiffened. Both astragalus and calcaneum were generally robust and elongated bones but the astragalar body was apparently reduced in this group. The astragalus has an elongated lateral condyle but the medial one is narrower. The lateral projection of the astragalus is thickened and extends to the midline of the whole element from the inner side to the rear, leading space for the lower end of the tibia; this exposes the lateral surface of the tibia in a frontal view. The calcaneum was larger and robust than most theropods. It has a rounded shape with concave articular surfaces and had a mobile articulation with the adjacent elements such as the astragalus or distal tarsals. Another highly modified element was the tetradactyl pes: the metatarsus was composed by four shortened, fully functionally metatarsals. Metatarsals III and IV were almost equal in size, the second was slightly narrow and the first one was the shortest. There are, however, traces of metatarsal V but it is highly reduced and has no functional significance−as seen on Segnosaurus. The phalangeal formula was as in other maniraptorans, IV-4, III-3, II-2 and I-1 (excluding the unguals). The pedal unguals were sharply pointed, side to side flattened and smaller than the manual unguals. In Erlikosaurus however, they are massive, combining a stiff and recurved shape with robust tubercles. Classification The family Therizinosauridae was coined by Evgeny Maleev in 1954 to contain the enigmatic Therizinosaurus, who interpreted this taxon as representing giant marine turtles. Relatives of Therizinosaurus were later found but not recognized as such for some time. With the description of Segnosaurus in 1979, the paleontologist Altangerel Perle coined