Beipiaosaurus

Name: Beipiaosaurus ‭(‬Beipiao lizard‭)‬.
Phonetic: Bat-pee-oh-sire-us.
Named By: Xu,‭ ‬tang,‭ ‬Wang‭ ‬-‭ ‬1999.
Classification: Chordata,‭ ‬reptilia,‭ ‬Dinosauria,‭ ‬Saurischia,‭ ‬Theropda,‭ ‬Therizinosauroidea.
Species: B.‭ ‬inexpectus‭ (‬type‭)‬.
Type: Herbivore.
Size: 2.2‭ ‬meters long.
Known locations: China,‭ ‬liaoning province‭ ‬-‭ ‬Yixian Formation.
Time period: Aptian of the Cretaceous.
Fossil representation: 2‭ ‬individuals,‭ ‬one which includes feathers.

       As a basal therizinosaur Beipiaosaurus revealed some surprising characteristics,‭ ‬hence the species name inexpectus.‭ ‬One of these‭ ‬characteristics is the underdeveloped inner toes,‭ ‬something that is very different to later therizinosaurids which have all four toes developed and in contact with the ground.‭ ‬This has been taken as an indication of a three toed ancestor,‭ ‬the fourth being speculated as being a dew claw that would regain contact with the ground in later descendents.‭ ‬This partly fits with the discovery of features that indicate coelurosaurian ancestry,‭ ‬the group that also gave rise to the tyrannosaurs.
       Arguably the most significant discovery related to Beipiaosaurus is not just the presence of primitive feathers,‭ ‬but of two kinds of them.‭ ‬The first is what is thought to have formed a downy covering for the purpose of insulation and is a feature that would become increasingly common in later small active theropods like Troodon.‭ ‬The second kind of feathers are larger and rise up through the downy layer.‭ ‬These feathers are between ten and fifteen centimetres long and about three millimetres wide.‭ ‬These feathers may have served more of a display purpose than a practical function,‭ ‬but it is still not possible to say with certainty.
       Beipiaosaurus was once the largest known feathered dinosaur, a title it held on to until the description of the carnivorous tyrannosaur Yutyrannus in 2012.

Further reading
- A therizinosauroid dinosaur with integumentary structures from China. - Nature 399:350-354. - X. Xu, Z.-L. Tang - X.-L. Wang - 1999.
- Pygostyle-like structure from Beipiaosaurus (Theropoda, Therizinosauroidea) from the Lower Cretaceous Yixian Formation of Liaoning, China - Acta Geologica Sinica 77 (3): 294–298. - X. Xu, Y. Cheng, X. -L.Wang, C. Chang - 2003.



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