Saturday 11 November 2017

PrehiScotInktoberfest Day 11: The Marvelous Creatures of the Rhynie Chert


Beware, there's a beastie in PrehiScotInktoberfest 11! Well, technically not a spider... Let me explain.

Back at the turn of the 20th Century, while mapping near the wee village of Rhynie, incredibly rich and detailed fossil remains from the Devonian period were uncovered: such finds are called Lagerstätte. This Lagerstätte was called the Rhynie Chert for the village, and it's an extraordinary chunk of rock.

Normally, small animals are rarely fossilised on account of their size: microscopic fossils even more so. Yet the Rhynie Chert ensconced a plethora of absolutely tiny creatures, and for decades, was the only such example of such a find in the world.

So what were these beasties?

Well, that wee "spider" resting on a stem is a trigonotarbid called Palaeocharinus rhyniensis ("ancient Charinus Rhynie dweller"), a beastie unique to Scotland. It was only 4mm long, but it is very special, for trigonotarbids are among the earliest known land predators. I use "spider" in inverted commas, because they are far more primitive arachnids from before the time of spiders - though arachnophobes might find it a minor distinction! Palaeocharinus is notable for its eyes: not only those two beady ones in the middle, but two big lumps beside them with multiple lenses - theorised to be a link between compound eyes, and the many eyes of later arachnids.

As a landlubber, Palae-boy can only observe the shapes beneath the water's surface: furthest left is another Scotland original, Heterocrania rhyniensis is a euthycarcinoid, a weird arthropod thingy that's believed to be the ancestor of mandibulates (the group that includes myriapods like centipedes, crustaceans, and modern insects); furthest right is Castracollis wilsonae, a particularly advanced brachiopod, which are almost as common as trilobites in Scotland; lurking ominously in the background is Lepidocaris rhyniensis, the most common animal of the Rhynie Chert, which occupies its own family among the crustaceans.

They may not be as spectacular as the dinosaurs, but the Rhynie Chert fossils are amazing for the glimpse they offer into a world 400 million years passed, and if Water Bears have taught me anything, it's that the microscopic can be just as remarkable as the macroscopic.

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