Lucky Thirteen (Arms) – #365papers – 2017 – 13

#365papers for January 13, 2017 (A Friday, naturally)

Herringshaw, Smith, and Thomas, 2007, Evolutionary and ecological significance of Lepidaster grayi, the earliest multiradiate starfish: Zooliogical Jounal of the Linnean Society, v. 150, p. 743-754.

What’s it about?

This paper discusses a Silurian-aged sea star that had 13 arms, rather than the typical 5 of other sea stars. This is the earliest record of sea stars with more than 5 arms.

Why does it matter?

Though we think of sea stars as having five-fold symmetry, they’re really bilaterally symmetrical, like we are with right and left sides. This paper explores how an organism such as this can get extra arms. In this case, it was adding arms four at a time in four out of five gaps between the arms of a typical five-armed sea star, and then doing it again for a total of 13 arms.

Why did I read this?

It was Friday the 13th, and fellow tweep Liam Herringshaw tweeted about a 13-armed sea star he had written about ten years ago. I could not resist (and it’ll make an appearance in my course later this semester).


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