histology of that genus, as actually referable to Tarjadia. Additional specimens from various parts of the Chañares Formation were described in 2017, greatly expanding knowledge of the animal. These specimens include: CRILAR ( Centro Regional de Investigaciones y Transferencia Tecnológica de La Rioja, Paleontología de Vertebrados)-Pv 463b: six osteoderm fragments. CRILAR-Pv 477: A partial skeleton, not including the skull. CRILAR-Pv 478: A partial skeleton, including a partial skull. CRILAR-Pv 479: The tip of a dentary, seven vertebrae, two osteoderms, and rib fragments. CRILAR-Pv 495: A nearly complete skull and lower jaws. CRILAR-Pv 564: two vertebrae, two teeth, and other fragments. CRILAR-Pv 565: A partial skeleton including the rear part of a skull. CRILAR-Pv 566: A partial braincase. Description Osteoderms Tarjadia has been diagnosed on the basis of its osteoderms, or bony scutes, the most common material that has been found of the genus. The paramedian osteoderms, which overlie the back to either side of the midline, are thick and rectangular. Their medial edges are serrated, allowing the two rows to suture tightly together. Smaller, more rounded osteoderms are thought to have been placed to the sides of the paramedians, although no articulated remains bearing these lateral osteoderms have been found to prove this. Both the paramedian and lateral osteoderms are deeply pitted. The paramedian osteoderms are thickest at the center and medial edges, with spongy bone between the compact outer layers. Skull The bones of the skull table are very thick. Like the osteoderms, they are covered in coarse pitting. The surfaces of these bones also bear perforations for blood vessels, especially around the edges of the orbits, or eye sockets. The parietal bones, which lie between two openings on the skull table called supratemporal fenestrae, have a distinctive sagittal crest. On the underside of the parietals, there is a depression for the olfactory bulb of the brain, responsible for the perception of smell. An olfactory channel leads up to this depression and can be seen on the underside of the frontal bones. The fragmentary occipital area of the skull (the base of the skull) shows part of the boundary of the foramen magnum (through which the spinal cord enters the skull), channels for the vestibular system (part of the inner ear responsible for balance), and holes for the semicircular canal (also part of the vestibular system). These holes and channels are found on the supraoccipital bone. The exoccipitals and