NUEVA ESPECIE DEL GÉNERO COLAPTES (AVES, PICIFORMES) PARA EL PLEISTOCENO DE LA REGIÓN PAMPEANA, ARGENTINA

Resumen ∙ En el presente artículo se describe un esqueleto relativamente completo de una nueva especie de Picidae (pájaros carpinteros) procedente de los alrededores de la localidad de Merlo, en la provincia de Buenos Aires, Argen‐ tina. El holotipo proviene del Miembro Jáuregui, de edad Pleistoceno Tardío temprano (75.000–30.000 años AP). Material adicional referido a este taxón procede del Pleistoceno Inferior‐Medio (1.200.000–400.000 AP) del sur de la provincia de Buenos Aires, y del Pleistoceno Tardío (126.000–11.000 AP) de Uruguay. Estos ejemplares indican que la especie poseía una amplia distribución geográfica y temporal. El material esqueletario disponible fue comparado con otros Picidae, resultando en el reconocimiento de una nueva especie del género viviente Colaptes. El nuevo taxón, aquí denominado Colaptes naroskyi sp. nov. Es de tamaño corporal notable, comparable a la especie de Picidae sudamericano de mayor tamaño: el Carpintero Magallánico (Campephilus magellanicus). Difiere de otras especies conocidas de Colaptes por tener el tibiotarso y tarsometatarso notablemente elongados, y el húmero proporcionalmente corto y delgado. Sobre la base de la morfología del miembro posterior, se infiere que el nuevo taxón habría poseído hábitos más caminadores que las especies vivientes que hoy en día frecuentan la Región Pampeana. Colaptes naroskyi sp. nov. constituye la primera paleospecie de la familia Picidae descripta para el continente sudamericano.Abstract ∙ A new species of the genus Colaptes (Aves, Piciformes) from the Pleistocene of the Pampean Region, Argentina The present paper describes a nearly complete skeleton of a new species of Picidae (woodpeckers) found near Merlo, Buenos Aires province, Argentina. The holotype was found in Early‐Late Pleistocene (75.000–30.000 years BP) beds of the Jáuregui Member. Additional reference material, which can be attributed to this species, coming from Early‐Mid Pleistocene (1.200.000–400.000 BP) beds of southern Buenos Aires province, and from Late Pleistocene (126.000–11.000 BP) beds from Uruguay indicates that this species had a large temporal and geographical distribution. The available skeletal material was compared with other species of woodpeckers. Based on these comparisons we conclude that the material corresponds to a new species of the living genus Colaptes. The new taxon, Colaptes naroskyi sp. nov., is notably large, comparable in size with the largest South American woodpecker, the Magellanic Woodpecker (Campephilus magellanicus). It differs from other known Colaptes in the very elongate tibiotarsus and tarsometatarsus, and in a proportionally short and slender humerus. On the basis of the posterior limb morphology, the new taxon may have possessed more terrestrial habits than the living species currently inhabiting the region. Colaptes naroskyi sp. nov. constitutes the first paleospecies of woodpecker described for the entire South American continent.

Flexibility along the Neck of the Neogene Terror Bird Andalgalornis steulleti (Aves Phorusrhacidae)

BACKGROUND: Andalgalornis steulleti from the upper Miocene-lower Pliocene (≈6 million years ago) of Argentina is a medium-sized patagornithine phorusrhacid. It was a member of the predominantly South American radiation of 'terror birds' (Phorusrhacidae) that were apex predators throughout much of the Cenozoic. A previous biomechanical study suggests that the skull would be prepared to make sudden movements in the sagittal plane to subdue prey. METHODOLOGY/PRINCIPAL FINDINGS: We analyze the flexion patterns of the neck of Andalgalornis based on the neck vertebrae morphology and biometrics. The transitional cervical vertebrae 5th and 9th clearly separate regions 1-2 and 2-3 respectively. Bifurcate neural spines are developed in the cervical vertebrae 7th to 12th suggesting the presence of a very intricate ligamentary system and of a very well developed epaxial musculature. The presence of the lig. elasticum interespinale is inferred. High neural spines of R3 suggest that this region concentrates the major stresses during downstrokes. CONCLUSIONS/SIGNIFICANCE: The musculoskeletal system of Andalgalornis seems to be prepared (1) to support a particularly big head during normal stance, and (2) to help the neck (and the head) rising after the maximum ventroflexion during a strike. The study herein is the first interpretation of the potential performance of the neck of Andalgalornis in its entirety and we considered this an important starting point to understand and reconstruct the flexion pattern of other phorusrhacids from which the neck is unknown