Wikipedia:Today's featured article/January 21, 2020

O. kokomoensis
O. kokomoensis

Onychopterella was a predatory aquatic arthropod of the order of eurypterids, often called sea scorpions. Fossils of the species O. kokomoensis (pictured) and O. pumilus have been found in the United States, and fossils of O. augusti in South Africa. Onychopterella (from Greek for 'claw wing') lived from the Late Ordovician to the Late Silurian, from 444 to 422 million years ago. The head was almost rectangular, with bean-shaped compound eyes. The limbs were generally long and narrow with a spine on the tip, and the body was ornamented with small, pointed scales. Lengths ranged from 16 cm (6.3 in) for O. kokomoensis to 4 cm (1.6 in) for O. pumilus. Onychopterella was able to swim, and probably able to walk on the seabed with its spines and dig with its head. The best-preserved specimens of O. augusti show similarities to modern scorpions in their alimentary canal, limb musculature and respiratory system. (Full article...)