Alxasaurus

MEANING: Alxa lizard

PERIOD: Early Cretaceous

CONTINENT: Asia

Alxasaurus is among the earliest known Therizinosauroids, but it already possessed the body shape, including the long neck, short tail, and relatively large claws. Like other members of this group, Alxasaurus was a bipedal herbivore with a large gut to process plant material. Its maximum adult length is estimated up to 4 m and mass up to 400 kg.

Alxasaurus is from the Early Cretaceous. The Cretaceous is the third and final geological period of the Mesozoic Era, with the Early Cretaceous making up roughly the first half, lasting from about 143 to 100 million years ago. The poles were ice-free, due to the relatively warm climate, and forests extended into high latitudes. The continued breakup of the continents created new coastlines and isolated landmasses, influencing the evolution of distinct dinosaur faunas.

It was a time of transition, as many groups of animals and plants began to take on more modern forms while others declined or disappeared. Pterosaurs continued to thrive, though early birds were becoming more diverse and widespread. Mammals remained small but adapted to a variety of ecological niches. In the oceans, ichthyosaurs and plesiosaurs were common, and early mosasaurs began to appear.

Dinosaurs remained the dominant land animals, with groups like iguanodontians, spinosaurids, and carcharodontosaurids rising to prominence. While sauropods declined in some regions, they remained abundant in the Southern Hemisphere. The first true ceratopsians appeared, and ankylosaurs replaced stegosaurs in their niche. Dromaeosaurs and other small theropods diversified. During this time, the first flowering plants evolved, gradually changing global ecosystems by providing new food sources for herbivores.

Alxasaurus is a therizinosaur. Therizinosauria is an unusual group of theropod dinosaurs. Though descended from classic carnivorous ancestors, therizinosaurs underwent a dramatic evolutionary shift toward herbivory. Derived members are known for their bizarre and distinctive body plan: large, bulky bodies, small skulls with beaks, long necks, and some of the longest claws known in any land animal. These claws, while intimidating, were likely used for pulling down branches or defense rather than hunting. Their teeth were small and leaf-shaped, adapted for processing plant material, and some members even show evidence of a partially feathered or fully feathered coat, a trait inherited from their maniraptoran lineage.

Therizinosaurs lived during the Cretaceous Period and have been found primarily in Asia and North America. Their fossils are often discovered in floodplain or coastal environments, suggesting they may have browsed on a variety of vegetation. Despite their odd appearance, therizinosaurs are a clear example of how flexible theropods could be, evolving to fill ecological roles far beyond their predatory origins.