Tremacyllus incipiens Rovereto, 1914 (Fig. 15) Tremacyllus incipiens Rovereto, 1914: 46 (original description). Tremacyllus latifrons Rovereto, 1914: 47 (n. syn.). Tremacyllus impressus – Sostillo et al. 2018: 411 (in part). MATERIAL. — Holotype: MACN-Pv 8163. Articulated skull from Santa María valley (Catamarca Province; Rovereto 1914). REVISED DIAGNOSIS. — Excavated palate; P2 elliptical with its major axis almost mesiodistally oriented, markedly proportionally smaller than P3 and P4, and the P2 of Tremacyllus impressus; P3 elliptical with its major axis obliquely oriented (distolingual-mesiolabially); P4 with almost rectangular distolingual face with rounded edges, ectoloph slightly concave in the distal section and convex near the parastyle region, straight distal face oriented perpendicular to the mesiodistal axis of the tooth and mesial face obliquely oriented (distolingual-mesiolabially) well-differentiated from lingual one, both forming an obtuse angle; upper premolars clearly less imbricated than in Tremacyllus impressus (modified from Rovereto 1914; Cerdeño & Bond 1998). OCCURRENCE. — Chiquimil Formation (El Jarillal Member, Late Miocene, Tortonian; Latorre et al. 1997), Villavil locality (Catamarca Province, Argentina). Andalhuala Formation (Late Miocene-Early Pliocene, Messinina-Zanclean; Georgieff et al. 2017), Entre Ríos, Loma Rica, Corral Quemado, Río Yaspis, western slopes of Cerro Pampa (Catamarca Province, Argentina), and Encalilla (Tucumán Province, Argentina) localities.

Published as part of Armella, Matías A., Ercoli, Marcos D., Bonini, Ricardo A. & García-López, Daniel A., 2022, Detecting morphological gaps in tooth outlines of a Pachyrukhinae (Hegetotheriidae, Notoungulata) lineage: systematic and palaeobiogeographical significance of the records from Northwestern Argentina, pp. 323-348 in Comptes Rendus Palevol 21 (16) on page 344, DOI: 10.5852/cr-palevol2022v21a16, http://zenodo.org/record/20746332