Saguinus ursulus is a species of neotropical primate that was recently reclassified from the former Saguinus niger. Their IUCN conservation status is Vulnerable (VU), since they are located in Amazonian areas considered to have high human settlement rates and advanced environmental degradation. 1,2 Recent studies indicate the existence of this new taxon; however, little is known about the particular anatomy and physiology of these animals. 2,3,4 Among Neotropical primates, there is a great diversity in the phenotype, mainly in weight and size. Examining the anatomy contributes to understanding the particular morphophysiology each species, aiming toward its conservation and captive care. The complementary imaging examination helps evaluate internal structures and organs, making it possible to describe attributes of each species studied. 5 Ultrasonography is a non-invasive, non-ionizing, and painless imaging resource that facilitates efficient analysis of abdominal and pelvic organs. Outcomes include reproductive analysis, an important parameter in research involving vulnerable species. 6 Studies on the pelvic-abdominal organ morphometry and reproductive physiology of S. ursulus are scarce. Reproduction of this species in captivity has not been reported yet. This study aimed to determine the appearance of these structures and organs, through ultrasonography, thereby contributing to the morphophysiological knowledge of the genus.