Musacaris is an extinct genus of Cambrian arthropod from the Orsten Lagerstätte, formerly synonymous with Martinssonia.

Musacaris is a small (roughly 0.8 mm long), unsegmented arthropod, with four pairs of appendages.

[1] It also has an unusual projection on its head, possibly the future position of the mouth.

The unsegmented body suggests all current specimens of Musacaris may be so-called "head larvae".

Currently, Musacaris is thought to be a basal mandibulate or stem-crustacean, possibly sister to labrophorans (Crustacea and Phosphatocopina).