Tratayenia rosalesi was named by Porfiri et al. (2018) [Megaraptoran theropod diagnosed by the following autapomorphies and a unique combination of characters. Autapomorphies: middle and posterior dorsal vertebrae with slender, parallel prezygodiapophyseal and paradiapophyseal laminae, both of which persist throughout the series; ventral margin of prezygapophysis of middle and posterior dorsal vertebrae subhorizontal in lateral view, meeting anterior margin of prezygapophysis at a nearly right angle; middle dorsal vertebrae with paired, ventrally diverging laminae extending from the ventrolateral base of the anterior edge of the neural spine to the base of the prezygapophysis, having the form of an inverted ‘Y’ in anterior view; neural spines of posteriormost three sacral vertebrae nearly twice as long anteroposteriorly as that of the first sacral vertebra. Unique combination of characters: pleurocoels of dorsal and sacral vertebrae large and subequal in size; dorsal and sacral vertebrae with camellate internal tissue structure; neural spines of middle and posterior dorsal vertebrae laterally compressed throughout their lengths; posterior dorsal vertebral centra taller than long; posterior dorsal vertebrae with subtle lateral process of postzygapophysis; posterior dorsal vertebrae with transversely narrow, blade-like hyposphene; sacral centra with elliptical pleurocoels; posterior sacral neural spines curved posteriorly; summit of posteriormost sacral neural spine twice as anteroposteriorly broad as its base; ilium extensively pneumatized; ilium with pneumatic foramina on lateral surface of preacetabular process; dorsal margin of ilium straight in lateral view.]. Its type specimen is MUCPv 1162, a partial skeleton (an associated partial postcranial skeleton comprised by the following elements: an articulated series of five middle and posterior dorsal vertebrae (identified ), and it is a 3D body fossil. Its type locality is Los Pilares-Tratayén fossil site, which is in a Santonian terrestrial siliciclastic in the Bajo de la Carpa Formation of Argentina.