Woohoo! What's better than a new #alvarezsaur
? TWO new alvarezsaurs!
People of the internet, it is my great privilege to introduce you to Xiunykus (2nd from left) and Bannykus (3rd from left).
In a paper published today by Xu et al, two new alvarezsaurs are described that fill in a 90 million year gap - a ghost lineage - between basal things like Haplocheirus (far left) and specialised, derived things like Shuvuuia (far right).
Alvarezsaurs are a truly wacky clade of theropods with their more emblematic members possessing a single robust claw (Digit I) at the end of a tiny but beefy arm.
These two new specimens show a near-perfect and step-wise way how the very unique hand was acquired.
Haplocheirus, the basalmost member of this clade, has long arms and long hands. Xiunykus retains these long arms but is beginning to reduce the size of the hand. Bannykus reduces the arm even further, simultaneously shortening digits II & III but hypertrophying (beefing-up) digit I.
And to paraphrase Jim Clark; 'this is the theropod version of digit reduction in horses'
Bannykus: Ban-ny-kus (NOT: banny-kus)
Link to (beautifully written) paper:
Gouache on A3 watercolour paper.
Fiineliner for outlines.
"Chinese marker" and superfine white sharpie for sheens and shimmers.
Please credit: Viktor Radermacher