Pronunciation: AHL-shah-SOR-us
Meaning: Alxa desert lizard
Author/s: Russell and Dong (1993)
Synonyms: None known
First Discovery: Nei Mongol, China
Discovery Chart Position: #386
Alxasaurus elesitaiensis
Shorter tails aside, therizinosauroids—with their bipedal gait, robust pelves, long "S"-shaped necks, small heads, and four-toed feet—aren't a million miles away from moderately sized non-sauropod sauropodomorphs, features-wise. But a backwards-pointing hip reminiscent of ornithischians and curved hand claws more massive than those of the largest theropods meant they managed to dodge all attempts to find them a comfortable home on the dinosaurian family tree, and a lack of well-represented specimens didn't help. But that all changed in 1988.
The discovery of five Alxasaurus individuals in China's Bayin-Gobi Formation shed some much-needed light on these obscure critters, as a small bone called a "semi-lunate carpal"—which allowed its hands to be folded backwards at the wrist and held against the body, just like modern birds—is found only in maniraptoran theropods. Maniraptora includes the most advanced carnivorous theropods, such as oviraptorosaurs, dromaeosaurs, troodontids, and even birds. But the angle and width of hips to facilitate and support a huge foliage-fermenting gut, and the design of its jaws and teeth, showed that Alxasaurus was a maniraptoran theropod with a twist: it was a vegetarian!
All therizinosaurs—or segnosaurs, as they were once known—have this unique wrist bone, but the earlier ones, like Falcarius and Beipiaosaurus, have more theropod features, suggesting they were carnivores or omnivores that had set the ball in motion for later-living relatives to kick meat altogether. Funnily enough, as therizinosaurs evolved and lost their lust for flesh, their already impressive hand claws became even bigger, culminating in those of Therizinosaurus that measured around a metre long. Given the flexibility of their arms, though, the likes of Alxasaurus probably used their claws for nothing more sinister than snagging branches and shearing leaves in a manner similar to prehistoric ground sloths, and for self-defence against idiotic would-be predators.
The discovery of five Alxasaurus individuals in China's Bayin-Gobi Formation shed some much-needed light on these obscure critters, as a small bone called a "semi-lunate carpal"—which allowed its hands to be folded backwards at the wrist and held against the body, just like modern birds—is found only in maniraptoran theropods. Maniraptora includes the most advanced carnivorous theropods, such as oviraptorosaurs, dromaeosaurs, troodontids, and even birds. But the angle and width of hips to facilitate and support a huge foliage-fermenting gut, and the design of its jaws and teeth, showed that Alxasaurus was a maniraptoran theropod with a twist: it was a vegetarian!
All therizinosaurs—or segnosaurs, as they were once known—have this unique wrist bone, but the earlier ones, like Falcarius and Beipiaosaurus, have more theropod features, suggesting they were carnivores or omnivores that had set the ball in motion for later-living relatives to kick meat altogether. Funnily enough, as therizinosaurs evolved and lost their lust for flesh, their already impressive hand claws became even bigger, culminating in those of Therizinosaurus that measured around a metre long. Given the flexibility of their arms, though, the likes of Alxasaurus probably used their claws for nothing more sinister than snagging branches and shearing leaves in a manner similar to prehistoric ground sloths, and for self-defence against idiotic would-be predators.
[Alxa lizard from Elestai]Etymology
Alxasaurus is derived from "Alxa" (also known as "Alashan", the desert where it was discovered) and the Greek "sauros" (lizard).
The species epithet, elesitaiensis, combines "Elestai" (a village close to the dig site) with the Latin "ensis" (from).
Discovery
The remains of Alxasaurus were discovered in the Bayin-Gobi Formation near Elesitai, Nei Mongol (Inner Mongolia), China, by joint Sino-Canadian expeditions in 1988.
The holotype (IVPP 88402) is the largest of five individuals which were discovered together and consists of a mandible (lower jaw), some teeth, limb bones, ribs, all five sacral (hip) vertebrae and the first nineteen tail vertebrae. The other four specimens (IVPP 88301, IVPP 88402b, IVPP 88501 and IVPP 88510) account for most of the parts missing from the holotype, but none of them added to the meagre skull material.
