First record and a new species of seriema (Aves: Ralliformes: Cariamidae) from santacrucian (Early-middle miocene) beds of Patagonia

Abstract

The extant seriemas are long-legged cursorial birds which represent surviving relicts in South America of an early gruiform radiation within the suborder Cariamae. Phorusrhacids, idiornithids, and bathornithids are also extinct components of this large terrestrial stock of predator or scavenger birds which were abundant during the Tertiary of South and North America,and Europe. The phylogenetic relationships and paleobiogeographic history of these clades are today far from being resolved. However, Tertiary fossils of cariamids Cariaminae are scarce and restricted to the questionable record of Riacama caliginea Ameghino 1899 from the Late Oligocene (Deseadan age) of Santa Cruz Province, and the Early-Middle Pliocene (Montehermosan age) record of Chungai incerta Tonni 1974 from Buenos Aires Province, both in Argentina. Living seriemas comprise only two very closely related,and perhaps congeneric species, Cariama cristata (Linnaeus 1766) and Chunga burmeisteri (Hartlaub 1860), which are endemic of South America. The fossils herein described come from the locality Puesto Estancia La Costa (= Corriguen Aike), situated at the coast of Santa Cruz Province, between Coyle and Gallegos rivers, and were recovered from the middle levels of Estancia La Costa Member, Santa Cruz Formation. The remains include three unassociated specimens: a fragmentary basicranium and two distal fragments of tibiotarsi, one of them slightly larger and more robust than the other. The leg bones are nearly indistinguishable from the homologous elements in living seriemas. A new species is erected: Cariama santacrucensis.