21 January, 2020

Fossil of oldest scorpion known to science discovered

Scorpions have been around for a long time and researchers think they were among the first animals to become terrestrial. There is a debate going on whether these old scorpion ancestors were living in water or developed on land. Some think the latter, and that the water living species found developed later.

Andrew J. Wendruff and co-workers have discovered a 430 million years old preserved fossil scorpion from the Waukesha Biota (early Silurian, ca. 437.5–436.5 Ma) of Wisconsin, USA. This is the oldest scorpion fossil ever found. In their interesting article the authors discuss whether Parioscorpio venator, which is the name of grand, grand, grand .........father of today's scorpions, lived on land or in water. Their conclusion is that it probably could live in both environments, similar to today's horseshoe crabs.

Scorpions are among the first animals to have become fully terrestrialised. Their early fossil record is limited, and fundamental questions, including how and when they adapted to life on land, have been difficult to answer. Here we describe a new exceptionally preserved fossil scorpion from the Waukesha Biota (early Silurian, ca. 437.5–436.5 Ma) of Wisconsin, USA. This is the earliest scorpion yet reported, and it shows a combination of primitive marine chelicerate and derived arachnid characteristics. Elements of the circulatory, respiratory, and digestive systems are preserved, and they are essentially indistinguishable from those of present-day scorpions but share similarities with marine relatives. At this early point in arachnid evolution, physiological changes concomitant with the marine-to-terrestrial transition must have occurred but, remarkably, structural change in the circulatory or respiratory systems appear negligible. Whereas there is no unambiguous evidence that this early scorpion was terrestrial, this evidence suggests that ancestral scorpions were likely capable of forays onto land, a behavior similar to that of extant horseshoe crabs.

Wendruff AJ, Babcock LE, Wirkner CS, Kluessendorf J, Mikulic DG. A Silurian ancestral scorpion with fossilised internal anatomy illustrating a pathway to arachnid terrestrialisation. Sci Rep. 2020;10(1):14.  [Open Access]

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