December 19th

Box #19 in our count down is Castorocauda…

Days 1-5 of the count down.
Days 6-10 in the count down
Days 11-15 of the count down
Days 16-20 of the count down
Days 21-25 of the count down
Castorocauda, the platypus beaver from Jurassic China

Castorocauda: the “Beaver Tail”

Castorocauda lived in middle to late Jurassic China, and is another example of how early mammals ranged into many different body plans and places in their environment. Many mammals and almost-mammals looked very different from the stereotypical mouse or opossum one usually thinks of when imagining the timid, furry creatures that scurried in the shadows of giant dinosaurs.

Fossils of Castorocauda preserve dense fur like an otter, and scales on its tail like a beaver, but it may have been just a little bit more like a platypus than the other two, because it is was from a group of animals called docodonts. Docodonts were about as close a relative to true mammals as a critter can be without actually being what scientists call a “crown mammal”.

In life, Castorocauda would have looked and behaved very much like a platypus (aside from the duckbill). It had teeth well suited for catching slippery fish, whiskers that could seek out shrimp and crawdads from the murky water, and webbed feet for swimming. It’s arms were relatively short and stout, with strong fingers and claws well suited for digging burrows. Even its ribs and spine show that it was a strong swimmer and good at digging, and would have waddled like a platypus. On the back legs, there is a spur just like male platypus.

It is possible that Castorocauda laid eggs like modern platypus. What makes a platypus a true mammal is not only parts of the skeleton that are invisible on the surface, but also the fact that mothers give milk to their young. What we don’t know, and possibly will never know, is if Castorocauda also produced milk.

5 thoughts on “December 19th

  1. Okay, so this is the one creature you’ve previously drawn before. I think it’s perfect due to how unique it is and that it will be February’s COTM. Another to point out is that the first instance of “Castorocauda lived in middle to” is unnecessary since the second instance is there and part of an actual article.
    I plan on doing something Paleozoic for today, but I need you to reply to my comment on your Ostafrikasaurus post to continue (plus those from the Guanlong, Dysalotosaurus, and Mamenchisaurus posts before it). Then I can go back to showcasing a prehistoric creature daily.


      1. That’s nice to hear, anyways, the critter that I’ll briefly talk about is Haikouitchys, a primitive chordate from the Cambrian of China. Its defined skull, plus some other characteristics have led to possibilities that it could be a basal craniate or basal chordate. It has a distinctive head and tail, with head having somewhere around 6-9 gills and the tail having a number of segments. A dorsal fin is located, starting from the middle of the back and surrounding the tail end. Haikouichthys is significant for being a possible ancestor to vertebrates, and close relatives include Myllokunmingia, Yunnanozoon, and Zhongjianichthys.


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