Jaekelopterus rhenaniae

Jaekelopterus is a pterygotid eurypterid merostomate arthropod from the Early Devonian of Germany and the United States of America. It was named in 1914 by Otto Jaekel. It was the biggest eurypterid to exist, surpassing even the Pterygotus, Acutiramus, and Arthropleura.

Physiology
Like its cousin, Pterygotus, Jaekelopterus resembled the generic eurypterid. It was a large chelicerate with a rounded cephalothorax, large eyes, long arms with serrated claws, 4 pairs of walking legs, a pair of paddles for swimming, and a long tail ending in a paddle. Its body would have been covered in a hard, chitinous exoskeleton.

Diet
Jaekelopterus was a predator, preying on fish, trilobites, ammonites and smaller eurypterids. Its serrated claws were used for catching and getting a hold of any struggling prey, as well as crushing them and ripping them apart.

Ecology
Unlike its marine cousin, Pterygotus, Jaekelopterus lived in freshwater rivers and estuaries, lying on the riverbed in order to ambush prey. Its robust, serrated claws were used to grab and rip apart any unsuspecting fish, trilobites, cephalopods, or small chelicerates, allowing access to their innards. As well as this, its paddles, as well as its tail, were used to propel itself through the water. A study on all pterygotid eurypterids had shown that its eyesight was on par with that of modern predatory arthropods, such as dragonflies and mantids.