Sunday 12 November 2017

PrehiScotInktoberfest Day 12: Pterichthyodes milleri

The next three days may see a dearth of PrehiScotInktoberfest, for I'll be away deep in the Mountains of Argyll on a quest of self-discovery. (Yes, really. That's what I'm doing this weekend. Every Scottish person does it.)

But before I embark on this journey, here's PrehiScotInktoberfest 12!

Most Scottish prehistoric discoveries have been marine life forms, and Pterichthyodes milleri ("Miller's wing-fish form") was one of the first - as well as one of the first great mysteries. Back when these beasties were first found, Darwin's work on evolution had not yet been published, so people wondered what on earth these things were: they were unlike any fish living today, and they didn't seem to fit in with the established scientific consensus.

Nowadays, Pterichthyodes is classed as a placoderm, a very weird, and very old, order of fishies: they were some of the first to develop distinctive jaws, and displayed very distinctive armour-plated heads. As a paraphyletic organism, Pterichthyodes and other placoderms can be considered an ancestral relative to all jawed vertebrates. So, now you know who to blame!

Pterichthyodes was particularly remarkable for its powerful fins, from which it derives its name ("wing fish"): early reconstructions supposed that it, like the more famous lobe-finned fish, could crawl about on the land. More recent thinking suggests it used those powerful limbs to scuttle around the deep sea bed, or to bury into the sand like modern soles, as I illustrate here.

"I can see you, but you cannae see me, I am hidden!"

"Naw ah kin still see ye, Ptery."

"Kin ye naw caw me tha'?"

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