Montecaris is a genus of extinct phyllocarid crustaceans found in the Upper Devonian of Europe,[1][2][3][4][5] Canada,[6] and Australia.

[7] Montecaris possesses an unornamented, bivalved carapace which terminates in a spiny posterior.

Its caudal tail fin is trifurcated and dagger-like.

[6][7] Due to its streamlined carapace and large tail fin, Montecaris was likely an active nektonic swimmer, which primarily appears in deep water sediments.

Its robust mandibles and powerful musculature suggests a carnivorous lifestyle as an active predator or scavenger.