Topography of the medullar cone in nutria (Myocastor coypus Molina, 1782 – Rodentia: Mammalia)

Aiming to investigate the topography of the medullar cone, ten adult nutria (Myocastor coypus), eight male and two female, were previously fixed in 10% aqueous formalin solution, maintained in similar solution and dissected. After the dissection the following data were noted: a) the medullar cone apex was close to the fifth lumbar vertebra (L5) in five animals (50.0%), between L5 and L6 in three animals (30.0%), between L4 and L5 in one animal (10.0%), and just above L6 in one animal (10.0%); b) the medullar cone base was observed between L3 and L5 in nine animals (90.0%), and in one animal alone (10.0%) it was found between the L4 and L5 vertebrae. This Myocastor coypus presented six lumbar vertebrae.