Episode 142 is all about Alxasaurus, one of the earliest known dinosaurs in the superfamily Therizinosauroidea.

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In this episode, we discuss:

News:

The dinosaur of the day: Alxasaurus

Therizinosauroid alxasaurid theropod that lived in the Early Cretaceous in what is now Inner Mongolia

One of the earliest known dinosaurs in the superfamily Therizinosauroidea

Name means “Alxa Desert lizard”

Named after the Alxa Desert of Inner Mongolia, which is also known as the “Alashan” desert

Found on a joint Canadian-Chinese expedition in 1988

Described and named by Dale Russell and Dong Zhiming in 1994

Type species (and only species) is Alxasaurus elesitaiensis

Species name is for Elesitai, a village in the region, near where Alxasaurus was discovered

Five specimens were found (found lower jaw, some teeth, limb bones, ribs, vertebrae, and tail vertebrae); all form a nearly complete skeleton, minus the skull

Shows transition period between general theropods and more advanced therizinosaurids

Before Alxasaurus, scientists thought therizinosaurs were related to sauropods

Looks similar to other therizinosaurs, but also similar to other types of theropods (which shows that therizinosaurs were weird theropods). One example of this is the semilunate carpal bone of the wrist (which allows wrists to be more flexible), which is also found in maniraptorans such as oviraptorosaurs, dromaeosaurs, and troodontids

Had a long neck, short tail, and long hand claws, like later therizinosauroids

Bipedal

Had no teeth, but a mouth that would have acted like a beak

Because of this, unclear if it was an herbivore (though most likely it was)

Had an agile, lightweight build, like a carnivore

Had a large gut, which may have helped it digest plants

Had large claws, that would have helped it reach tall branches for leaves

If it did eat meat, it would have had to scavenge

Shows that herbivores can evolve from carnivores

Largest known Alxasaurus was over 12 ft (3.8 m) long. Gregory Paul estimated it to be 13 ft (4 m) long and weight 400 kg

Other therizinosaurs had feathers (like Beipiaosaurus), so Alxasaurus may have also had feathers

Fun Fact:

Carnotaurus had significantly shorter arms than T. rex

Carnotaurus didn’t have wrists, its metacarpals connected directly to its tiny forearms. 2 of its metacarpals had no finger bones after them so it effectively also only had 2 fingers, which were likely very stiff.

It’s shoulder blade was about twice as long as its entire forelimb (from shoulder to finger tip)

These tiny arms are similar to a kiwi bird which has forelimbs so short they are hidden under their feathers.

Time to stop making fun of T. rex…

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