Dicranurus monstrosus by usageology on Flickr.

Locality: Maider, Morocco.
Age: Lower Devonian, Laatchana Formation (419.2 million–393.3 million years ago).
Size: Trilobite is 2.7 inches long.

Dicranurus  (“Twin head-tail”) was a genus of Lower Devonian lichid trilobites that lived in a shallow sea (Order Lichida, Family Odontopleuridae). 

The Twin head-tail, Dicranurus (1977)

Phylum : Arthropoda
Class : Trilobita
Order : Lichida
Family : Odontopleuridae
Genus : Dicranurus
Species : D. hamatus, D. elegans, D. monstrosus

  • Devonian
  • 2 cm long
  • Morocco and Oklahoma

Dicranurus was a genus of Lower Devonian lichid trilobites that lived in a shallow sea that lay between Euramerica and Gondwana, corresponding to modern-day Oklahoma and Morocco, respectively. As such, their fossils are found in Oklahoma and Morocco.

Their bodies averaged about 1-inch or so, in length, though their large spines made them at least 2 inches in length. It is speculated that such tremendous spines hampered the ability of predators, such as arthrodire placoderms, to attack them, as well as to help prevent them from sinking into the soft mud of their environment. Dicranurus trilobites are distinguished from other lichids by the pair of large, curled, horn-like spines that emanate from behind the glabellum. The genus name refers to these distinctive horns, in fact.