Alxasaurus is among the earliest known members of the Therizinosauroidea, but it already possessed the body shape — including the long neck, short tail, and relatively large claws — of later therizinosauroids. Like other members of this group, it was a
bipedal herbivore with a large gut to process plant material.
Mandible and lower dentition The skull of
Alxasaurus is represented solely by a moderately well-preserved right
dentary, belonging to the holotype. The
alveolar margin, the part of the dentary that bore teeth, measured in length. Several teeth, all partly erupted, are preserved, though there was room for around forty teeth (more than the thirty-one of
Erlikosaurus and the twenty-four of
Segnosaurus). The teeth in the
anterior (front) half of the alveolar margin bore between eight and ten
denticles on the anterior
carinae; those
posterior to (rearward of) those teeth had similar denticle shapes and sizes, though their exact number is unclear. Though poorly preserved,
interdental plates appear to have been present. While not preserved in
Alxasaurus, its presence in other therizinosaurs suggests that a beak likely would have been present. The anterior portion of the
ilium is unpreserved, as is the
pubis. Dorsal to the posterodistal end of the ilium was a large crest, probably
homologous to a rugose area found in the same position in
Segnosaurus. Two flattened, strap-like elements are preserved, tentatively interpreted as
ischia. The shaft of
Alxasaurus' femur was slightly bowed laterally, unlike in
Segnosaurus, where it was straight. The
femoral head is inclined dorsomedially. The bones of the
tarsus (ankle) are unknown. Many pedal (foot) elements are known, though identifications are largely dubious. The proximal end of the third
metatarsal was probably broad, as in
Segnosaurus. The metatarsus overall was abbreviated, converging on basal sauropodomorphs. The foot overall was likely quite broad. ==Classification==