Hoazinavis lacustris was named by Mayr et al. (2011) [Hoazinavis is very similar to the extant hoatzin in the morphology of the preserved bones and can be confidently identified as an opisthocomiform bird by the following derived features: (1) coracoid with pneumatic opening at the base of the procoracoid process (this feature otherwise only occurs in Tinamidae, Otididae, and a few species of Cuculidae), (2) humerus with a marked brachial fossa, and (3) the deltopectoral crest situated far distally on the shaft of the bone. The new taxon differs from Opisthocomus in that coracoid and furcula are not fused, and in that the scapula has a proportionally shorter acromion and smaller humeral articular facet, and lacks a pneumatic foramen at the base of the acromion. It is distinguished from Namibiavis in the derived presence of a marked brachial fossa on the humerus and a pneumatic opening at the base of the procoracoid process of the coracoid. H. lacustris, gen. et sp. nov. is significantly smaller than H. magdalenae from the Middle Miocene of Colombia, whose skull is slightly larger than that of O. hoazin, but owing to the lack of overlapping skeletal elements, the two species can otherwise not be compared.]. Its type specimen is MHNT-VT 5332, a set of postcrania (complete right humerus, omal end of right coracoid, and cranial extremity of right scapula of a single individual), and it is a 3D body fossil. Its type locality is Hoazinavis type locality, which is in a Deseadan terrestrial horizon in the Tremembé Formation of Brazil.