Early Devonian scorpions also had pectines

 

Pectines are one of the body structures that are unique for scorpions. This comb-like structure is found on the underside of the opisthosoma of scorpions and is a sensory organ for detecting both chemical and mechanical stimuli. 

In a recent short note, Jason Dunlop and co-workers report about a cuticle fragment from a pectinal tooth from a Early Devonian scorpion. This fossil indicates that some scorpions had developed anatomically modern pectinal teeth at least 395 million years ago and that they probably had a similar function as the pectines in today's scorpions.

Abstract:
A cuticle fragment found in an Early Devonian (Emsian) macerate from the Strathpeffer–Struie outlier in the Northern Highlands of Scotland represents the isolated pectinal tooth of a scorpion. This remarkable find includes a distinctive field of small projections in rounded sockets consistent with the peg sensilla of extant scorpions. This is the oldest evidence for the presence of these characteristic sensory organs, which in modern scorpions play an important role in chemo- and mechanoreception. The fossil indicates that some scorpions had developed anatomically modern pectinal teeth at least 395 million years ago, suggesting that the pectines of these early scorpions played a similar role, physiologically and behaviorally, to those of living species.

Reference:
Dunlop JA, Wellman CH, Prendini L, Shear WA. A pectinal tooth with peg sensilla from an Early Devonian scorpion. The Journal of Arachnology. 2023;51(3):255-7, 3. [Subscription required for full text]

Thanks to Matt Simon for informing me about this article!