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Dos restos aislados de aves fororracoideas fueron recientemente exhumados de los sedimentos de la Formación Sarmiento de edad Mustersense (Eoceno Superior) en la localidad fosilífera de Gran Hondonada en la provincia de Chubut, Argentina. Ambos restos, una falange ungueal del segundo dígito izquierdo (MEF PV-1721) y un tarsometatarso derecho sin su extremo distal (MEF PV-1722) son asignados a Phorusrhacidae Psilopterinae. Corresponden a aves depredadoras de mediano porte y escasa capacidad de vuelo, que habrían ocupado los niveles superiores de las cadenas tróficas y que sugieren la presencia de biomas abiertos con escasas áreas boscosas.

We analyze the connectivity patterns and fusion events among bones leading to the adult skeletal organization during the development of the superaltricial monk parakeet (Myiopsitta monachus, Psittaciformes), providing insights about the functional and evolutionary significance in the avian structural design. By using whole mount specimens stained for cartilage and bone, we apply anatomical network analysis (AnNA) to study the ontogenetic trajectory of the entire skeleton from embryonic stage 34 to adult. As bones condense, connect, and fuse to each other, we follow skeletal assemblages forming networks that change dynamically as the monk parakeet grows. Our results show that the pelvic girdle connects with the vertebral column prior to the pectoral girdle and that the pelvic girdle and hindlimbs connection begins and ends before that of the pectoral girdle and the forelimbs. We hypothesize that connections of the girdles and limbs could be linked to the altriciality of the species due to requirements for active movement in the use of the hindlimbs inside the nest, but not the need to use forelimbs to fly until much later. Further, as bones of the skull and pelvis fuse during development they form the largest and more connected assemblages, acting as attractors to connect to other bones, showing congruence between the connectivity pattern at each ontogenetic stage and the characteristic avian body plan., Facultad de Ciencias Veterinarias

Waterfowl (Aves, Anseriformes) constitute an ancient global radiation, and understanding the pattern and timing of their evolution requires a well-corroborated phylogeny including extant species and fossils. Following the molecular advances in avian systematics, however, morphology has often been held as misleading, yet congruence with molecular data has been shown to vary considerably among different skeletal parts. Here, we explore phylogenetic signal in discrete characters of the lacrimal/ectethmoid region of waterfowl, which is highly variable among species and constitutes a rich source of data. We do so by combining cladistic and multivariate approaches, and using phylogenetic comparative methods. We quantitatively recognize three major morphological types among lacrimal bones, and discuss homoplasy and potential synapomorphies of major clades using a molecular backbone tree. Our results clearly indicate that the lacrimal bone carries substantial phylogenetic signal and could be of systematic value at different levels of the phylogeny of waterfowl, feeding the exploration of other regions of the skull with this combined approach.

A new Anseriformes, Conflicto antarcticus gen. et sp. nov., represented by associated bones of a single individual, from the early Palaeocene of Antarctica is described. The new taxon is unlike any other known member of the order. Conflicto antarcticus is a medium-sized (2 kg) stem anseriform. The forelimb and pectoral girdle bones suggest that it was a flying bird, and the bones of the hindlimb show that it had elongated legs. The os quadratum represents a unique combination of features; some are similar to the features of the ancestral quadrate for galloanserines and some are similar to Anseriformes, but features such as the presence of three foramina are exclusive among Neornithes. The incisura or foramen nervi suracoracoidei is absent in C. antarcticus, as in most anatids and all Galliformes. Phylogenetic analysis shows that C. antarcticus + Anatalavis oxfordi is the most basal stem Anseriformes clade. This implies that the duck-type beak must have developed at an early stage of anseriform evolution. Conflicto antarcticus represents one (and possibly the most) substantial record of a non-marine Palaeocene bird from the Southern Hemisphere and supports the hypothesis that Neognathae had already diversified in the earliest Palaeocene. Fil: Tambussi, Claudia Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina Fil: Degrange, Federico Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina Fil: de Mendoza, Ricardo Santiago. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Departamento Científico de Paleontología de Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Sferco, Marta Emilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina Fil: Santillana, Sergio Nestor. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina

We used three-dimensional digital models to investigate the brain and endosseous labyrinth morphology of selected Neotropical Piciformes (Picidae, Ramphastidae, Galbulidae and Bucconidae). Remarkably, the brain morphology of Galbulidae clearly separates from species of other families. The eminentiae sagittales of Galbulidae and Bucconidae (insectivorous with high aerial maneuverability abilities) are smaller than those of the toucans (scansorial frugivores). Galbula showed the proportionally largest cerebellum, and Ramphastidae showed the least foliated one. Optic lobes ratio relative to the telencephalic hemispheres showed a strong phylogenetic signal. Three hypotheses were tested: (a) insectivorous taxa that need precise and fast movements to catch their prey, have well developed eminentiae sagittales compared to fruit eaters, (b) species that require high beak control would show larger cerebellum compared to other brain regions and higher number of visible folia and (c) there are marked differences between the brain shape of the four families studied here that bring valuable information of this interesting bird group. Hypotheses H1 and H2 are rejected, meanwhile H3 is accepted.

We describe new avian remains from the lower levels of the Toro Negro Formation (~7-6 Ma, U–Pb), exposed in Quebrada de la Troya between Vinchina and Jagüé towns in La Rioja Province, Argentina. The Toro Negro Formation is composed of a thick continental sequence (~2.4 km) of sandstones, conglomerates and mudstones deposited in both fluvial and lacustrine systems at the base of the unit. The avifauna of Toro Negro is low in diversity, and the majority of the remains are fragmentary and isolated. However, it is interesting in that it includes carnivorous birds such as a new species of a large eagle (Vinchinavis paka gen. et sp. nov.), scavengers (condors) and large herbivores (rheas). On the whole, the occurrences documented within the Toro Negro Formation confirm the presence of taxa with strong temperate warm preferences that typically inhabits open areas with arboreal patches within an arid-semiarid zone. The palaeoenvironmental characteristics of the fauna are confirmed as fully compatible with the evidence previously obtained through sedimentology and facies analysis. Fil: Tambussi, Claudia Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina Fil: Degrange, Federico Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina Fil: Ciccioli, Patricia Lucia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; Argentina Fil: Prevosti, Francisco Juan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Universidad Nacional de La Rioja. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Universidad Nacional de Catamarca. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Secretaría de Industria y Minería. Servicio Geológico Minero Argentino. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Provincia de La Rioja. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja; Argentina

The tarsometatarsus conformation and foot types in birds are unique traits within vertebrates. We investigate how the tarsometatarsus and the zygodactyl foot are formed during development in the monk parakeet (Myiopsitta monachus). Using bones, whole mount specimens stained for cartilage and bone, and histological sections, we focus on the osteology and morphogenesis of the tarsometatarsus. We also compare the tarsometatarsus development between the altricial monk parakeet with the precocial chicken. The results and conclusions we reached are: (1) the hypotarsus, a character of phylogenetic significance, is monocanaliculate in the adult; (2) digit I retroversion is consequence of the displacement of the articulation site of the metatarsal 1 and its torsion; (3) digit IV retroversion is linked to the development of the trochlea accesoria; (4) in ovo, the ossification and fusion of the metatarsals 2-4 begin in their mid-diaphysis and extends cylindrically to both proximal and distal directions; and (5) the differences in the development of the tarsometatarsus between the monk parakeet and the chicken evidence heterochronies, probably related with their different types of development.

Globuli ossei are subspherical structures of endochondral origin that are inserted in the hypertrophic cartilage of long bones, and are related to paedomorphic phenomena. These structures are here ...

El objetivo de esta tesis es conocer cómo se desarrollan los músculos y los huesos de los miembros posteriores durante la vida postnatal de Rhea americana y la relación que presentan con respecto a la masa corporal para ulteriormente conocer las posibles implicancias que estos rasgos pudieran tener en el estilo cursorial de locomoción. Se estudiaron un total de 22 ejemplares: 15 juveniles (de uno, tres, cinco y ocho meses de edad) y siete adultos de Rhea americana. En cada animal se tomó la masa corporal y la masa individual de 21 músculos del miembro posterior. Asimismo se analizó la variación métrica del fémur, tibiotarso y tarsometatarso. Se estudió macroscópicamente la maduración de las piezas óseas así como también la relación entre los accidentes óseos y el grado de desarrollo y extensión de los músculos para evaluar las implicancias que pudieran tener estos resultados en el campo de la paleobiología. La relación entre la masa corporal con la masa muscular (isometría o alometría) y con las diferentes medidas óseas fueron analizadas mediante regresión lineal., Facultad de Ciencias Naturales y Museo

Here we address the morphology of the cranial musculoskeletal in the South American Band-winged nightjar (Systellura longirostris, Caprimulgiformes, Aves) with the focus upon in how the mouth closure and opening mechanism is. Bony characters such as the thinness of the interorbital septum and the reduction of the postorbital process co-assist the location of large eyes, although correlations between eye size brain mass and body mass revealed that the Band-winged nightjar´s eye is bigger than expected. The reduction of the processus orbitalis of the os quadratum would allow the great mouth opening given by a large maxillary protraction. Systellura longirostris shows a zona flexoria intramandibularis with marked reduction in bone ossification that helps to the lateral opening of the jaws. In Systellura longirostris, the m. pseudotemporalis profundus, m. adductor mandibulae externus superficialis, and m. adductor mandibulae externus medialis are absent. The adductor muscles represent 66.614% of the total mandibular muscle mass. Physiological Cross Sectional Area (PCSA) values of the adductor muscles are high and the fibers are relatively long compared to other zoophagous birds, another condition that favors adduction. The m. adductor mandibulae externus profundus is the largest jaw muscle regarding its mass but its osteological correlate on the neurocranium, the fossa temporalis, is absent. In the absence of some muscles in charge of the bill closing, an elastic instability model for jaw closing is proposed. Fil: Demmel Ferreira, María Manuela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina Fil: Tambussi, Claudia Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina Fil: Degrange, Federico Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina Fil: Pestoni, Sofía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina Fil: Tirao, German Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina

Dos restos de pingüinos (Spheniscidae) procedentes de la Formación Coquimbo (Mioceno Medio- Plioceno Tardío) expuesta en “La Cantera” (cercanías de la ciudad de Coquimbo), en el sector sur-oriente (IV Región de Chile) son descriptos en este trabajo. Éstos se suman a los escasos vertebrados ya exhumados en el área y constituyen las primeras aves registradas para esta localidad. Corresponden a formas exclusivas de las costas de América del Sur y aparentemente más relacionadas con los pingüinos modernos que a las formas de altas latitudes. Los hábitos de vida y los requerimientos ambientales de los pingüinos vivientes (asociados a corrientes templadas frías) permiten inferir que en el momento de la sedimentación de la Formación Coquimbo, ya habría existido la influencia de la corriente fría de Humboldt. Coincidentemente, se reconoce un prolongado episodio frío hacia los ca. 15-12 Ma, en las aguas de la costa pacífica, momento en el cual se habría depositado la Unidad 2 (una de las 13 unidades previamente reconocidas) de la Formación Coquimbo.

The ossification sequence of Myiopsitta monachus was determined. Myiopsitta has a similar sequence to other altricial birds, with delayed skeletons compared to precocial species. The hindlimbs ossify before the forelimbs, a condition that could be linked to altriciality. To determine the stability of the sequences of ossification across birds, we selected species of different groups of Aves and used event-pairing method and character mapping on a phylogeny. Our results show that the homogeneity in the development of birds was supported by 56.77% of the character states. Event-pair cracking phylogenetic method was applied to identify sequence heterochronies. Results reveal a high number of heterochronies and show that the long bones in limbs may behave as modules. In Myiopsitta, the ossa ectethmoidale and mesethmoidale ossify early. These bones provide the origin site of the Psittaciformes' novel adductor m. ethmomandibularis, associated with strong bite forces, and its acceleration in the sequence may correspond to the functional hypothesis. Also, the early appearance of some hyoid apparatus elements occurs, and could be related to the development of tongue in Psittaciformes and its role in handling food, and is in concordance with the functional and size hypothesis.

The cranio‐mandibular complex is an important structure involved in food capture and processing. Its morphology is related to the nature of the food item. Jaw muscles enable the motion of this complex and their study is essential for functional and evolutionary analysis. The present study compares available behavioral and dietary data obtained from the literature with novel results from functional morphological analyses of the cranio‐mandibular complex of the Guira cuckoo (Guira guira) to understand its relationship with the zoophagous trophic habit of this species. The bite force was estimated based on muscle dissections, measurements of the physiological cross‐sectional area, and biomechanical modeling of the skull. The results were compared with the available functional morphological data for other birds. The standardized bite force of G. guira is higher than predicted for exclusively zoophagous birds, but lower than for granivorous and/or omnivorous birds. Guira guira possesses the generalized jaw muscular system of neognathous birds, but some features can be related to its trophic habit. The external adductor muscles act mainly during food item processing and multiple aspects of this muscle group are interpreted to increase bite force, that is, their high values of muscle mass, their mechanical advantage (MA), and their perpendicular orientation when the beak is closed. The m. depressor mandibulae and the m. pterygoideus dorsalis et ventralis are interpreted to prioritize speed of action (low MA values), being most important during prey capture. The supposed ecological significance of these traits is the potential to widen the range of prey size that can be processed and the possibility of rapidly capturing agile prey through changes in the leverage of the muscles involved in opening and closing of the bill. This contributes to the trophic versatility of the species and its ability to thrive in different habitats, including urban areas. Fil: Pestoni, Sofía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina Fil: Degrange, Federico Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina Fil: Tambussi, Claudia Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina Fil: Demmel Ferreira, María Manuela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina Fil: Tirao, German Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina

Knowledge about the embryonic stages of birds is important in answering many questions about development and evolution. We give the first description of 41 embryological stages of the monk parakeet (Myiopsitta monachus) on the basis of external morphology and comparison with the chicken. We also provide measurements of some external morphological characters (i.e. body mass, crown-rump, beak, forelimb, and third toe lengths) and perform comparisons with other precocial and altricial birds with the aim of identifying heterochronous developmental features. The following differences in the development of characters in the monk parakeet when compared with other birds were found: (1) delay of the feathers primordia, (2) wing buds initially greater than leg buds, (3) forelimbs and hindlimbs with similar relative size, (4) retroversion of the toe IV, (5) ventral curvature of the upper jaw, (6) positive regressions between stages and beak length with acceleration and higher values and III toe lengths with deceleration and lower values in the monk parakeet compared to the chicken. The growth pattern of the monk paraket Myiopsitta monachus could be influenced by some heterochronic processes like post-displacement, acceleration and/or deceleration. Results of this research allow the standard identification of stages in different species of parrots, recognize similarities and differences between precocial (the chicken) and altricial species (Myiopsitta), and provide planning data for future studies.

Psittaciformes are a very diverse group of non-passerine birds, with advanced cognitive abilities and highly developed locomotor and feeding behaviours. Using computed tomography and three-dimensional (3D) visualization software, the endocasts of 14 extant Neotropical parrots were reconstructed, with the aim of analysing, comparing and exploring the morphology of the brain within the clade. A 3D geomorphometric analysis was performed, and the encephalization quotient (EQ) was calculated. Brain morphology character states were traced onto a Psittaciformes tree in order to facilitate interpretation of morphological traits in a phylogenetic context. Our results indicate that: (i) there are two conspicuously distinct brain morphologies, one considered walnut type (quadrangular and wider than long) and the other rounded (narrower and rostrally tapered); (ii) Psittaciformes possess a noticeable notch between hemisphaeria that divides the bulbus olfactorius; (iii) the plesiomorphic and most frequently observed characteristics of Neotropical parrots are a rostrally tapered telencephalon in dorsal view, distinctly enlarged dorsal expansion of the eminentia sagittalis and conspicuous fissura mediana; (iv) there is a positive correlation between body mass and brain volume; (v) psittacids are characterized by high EQ values that suggest high brain volumes in relation to their body masses; and (vi) the endocranial morphology of the Psittaciformes as a whole is distinctive relative to other birds. This new knowledge of brain morphology offers much potential for further insight in paleoneurological, phylogenetic and evolutionary studies., Facultad de Ciencias Naturales y Museo

Psittaciform birds exhibit novelties in jaw bone structure and musculature that are associated with strong bite forces. These features include an ossified arcus suborbitalis and the muscles ethmomandibularis and pseudomasseter. We analyse the jaw musculature of the monk parakeet (Myiopsitta monachus) to enable future studies aimed at understanding craniofacial development, morphology, function and evolution. We estimate bite force based on muscle dissections, physiological cross-sectional area and skull biomechanical modelling. We also compare our results with available data for other birds and traced the evolutionary origin of the three novel diagnostic traits. Our results indicate that, in Myiopsitta, (i) the arcus suborbitalis is absent and the orbit is ventrally closed by an elongate processus orbitalis and a short ligamentum suborbitale; (ii) the ethmomandibularis muscle is a conspicuous muscle with two bellies, with its origin on the anterior portion of the septum interorbitale and insertion on the medial aspect of the mandible; (iii) the pseudomasseter muscle consists of some fibers arising from the m. adductor mandibulae externus superficialis, covering the lateral surface of the arcus jugalis and attaches by an aponeurotic sheet on the processus orbitalis; (iv) a well-developed adductor mandibulae complex is present; (v) the bite force estimation relative to body mass is higher than that calculated for other non-psittaciform species; and (vi) character evolution analysis revealed that the absence of the arcus suborbitalis and the presence of the m. pseudomassseter are the ancestral conditions, and mapping is inconclusive about presence of one or two bellies of the m. ethmomandibularis., Facultad de Ciencias Naturales y Museo

The microanatomical and histological structure of Eocene Antarctic stem penguin tarsometatarsi is examined in order to characterise the bone microstructure. Eight adult tarsometatarsi belonging to eight fossil species (Palaeeudyptes gunnari, Palaeeudyptes klekowskii, Anthropornis grandis, Anthropornis nordenskjoeldi, Archaeospheniscus wimani, Marambiornis exilis, Delphinornis arctowskii and Delphinornis larseni) collected from the Antarctic A. nordenskjoeldi Biozone (La Meseta Formation, ,34.2 Ma) were examined. The thin sections revealed a distinctive microanatomical variation among taxa. Whereas Anthropornis spp., A. wimani and P. gunnari possess massive, clearly osteosclerotic bones (medullary cavities absent or strongly reduced), the bones of Delphinornis spp., P. klekowski and M. exilis exhibit well-developed medullary cavities. The cortical bone in all the specimens consists of primary, well-vascularised fibro-lamellar bone and variable amounts of secondary bone. Medullary cavities are coated by a thick layer of lamellar bone tissue and coarse compacted cancellous bone. Although several causes can explain the striking microanatomical variation (e.g. ontogeny), we interpret that such variation is related to differential adaptations to the aquatic life, for which taxa with more massive bones were possibly adapted to deeper and more prolonged diving excursions. Fil: Cerda, Ignacio Alejandro. Universidad Nacional de Río Negro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación en Paleobiología y Geología; Argentina Fil: Tambussi, Claudia Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina Fil: Degrange, Federico Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina

We studied the hindlimb myology of the monk parakeet (Myiopsitta monachus). Like all parrots, it has zygodactyl feet enabling perching, climbing, hanging, moving easily among trees, and handling food. Muscles were described and weighed, and physio- logical cross-sectional area (PCSA) of four flexors and one extensor was calculated. In comparison to other muscles, the M. tibialis cranialis and the M. fibularis brevis show increased development and high PCSA val- ues, and therefore, large potential force production. Also, a large proportion of muscle mass was involved in flexing the digits. We hypothesize that these muscle traits are associated with the arboreal locomotion and food manipulation habits. In the monk parakeet, the M. extensor digitorum longus sends a branch to the hallux, and the connection between the M. flexor digito- rum longus and the M. flexor hallucis longus is type I (Gadow's classification). We reaffirm the presence of the M. ambiens as a plesiomorphic condition that dis- appears in most members of the order. Among Psittaci- formes, the M. fibularis brevis is stronger and the M. fibularis weaker in arboreal species than in basal terrestrial ones (e.g., Strigops). J. Morphol. 000:000- 000, 2014. V C 2014 Wiley Periodicals, Inc.

We restudy the holotype specimen and all the alleged fossil material assigned to Cayaoa bruneti Tonni from the Early Miocene marine deposits of the Gaiman Formation, Patagonia, Argentina. Cayaoa bruneti is phylogenetically placed close to the Erismaturinae (= ”Oxyurinae”) that contains the diving birds. It was considered a flightless foot-propelled diving duck and represents the earliest example of flight loss in Anatidae. We carried out a comparative and morphometric descriptive study of different species of anseriforms with special attention to divers, to evaluate which is the expected intraspecific size variation within anatids to make an assignment of materials with a greater degree of certainty. Our results allow us to state that one coracoid, five humeri, two carpometacarpi, 12 femora, eight tibiotarsi, and eight tarsometatarsi can be assigned to the species. Consequently, it was possible to make a more detailed description and amend the original diagnosis. http://dx.doi.org/10.5710/AMGH.24.05.2019.3199

Psittaciformes have apomorphies in the muscles of the jaw that include both the adductors m. ethmomandibularis (EM) and m. pseudomasseter (PM) which are equally responsible for the generation of strong bite forces. While the EM is present in all Psittaciformes, the PM can be absent or present, and even under-developed or well-developed. The aim of this study is to identify developmental reprogramming processes by comparing the myogenesis of the jaw of the monk parakeet Myiopsitta monachus with the information available about other species of Psittaciformes. Seventeen specimens including embryos at different developmental stages, and nestlings of different ages were studied through the analysis of serial histological sections. At embryonic stage 24 (S24) the muscle precursor was observed in the first pharyngeal arch. At S27 the muscle precursor was found to be divided into lateral, intermediate and medial portions. At S31 the independent development of the EM as a rostro-dorsal projection of the mm. pterygoidei could be observed. At S36 the individualization of all muscles was complete. Finally, the PM was detected two days after hatching as an aponeurotic dorsal projection of the m. adductor mandibulae externus superficialis, located lateral to the arcus jugalis. Our results suggest that in M. monachus the muscles EM and PM emerge as a result of a process of heterotipy, and variations in the degree of development of the PM are associated to a heterochronic process of post-displacement, with M. monachus having an underdeveloped PM with respect to basal Psittaciformes. Fil: Carril, Julieta. Universidad Nacional de la Plata. Facultad de Ciencias Naturales y Museo. Cátedra de Histología y Embriología Animal; Argentina Fil: Ronderos, Jorge Rafael. Universidad Nacional de la Plata. Facultad de Ciencias Naturales y Museo. Cátedra de Histología y Embriología Animal; Argentina Fil: Tambussi, Claudia Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina Fil: Chiale, Maria Cecilia. Universidad Nacional de la Plata. Facultad de Ciencias Naturales y Museo. División Zoología de Vertebrados. Sección Ornitología; Argentina

Sauropoda is one of the most diverse and geographically widespread clades of herbivorous dinosaurs, and until now, their remains have now been recovered from all continental landmasses except Antarctica. We report the first record of a sauropod dinosaur from Antarctica, represented by an incomplete caudal vertebra from the Late Cretaceous of James Ross Island. The size and morphology of the specimen allows its identification as a lithostrotian titanosaur. Our finding indicates that advanced titanosaurs achieved a global distribution at least by the Late Cretaceous. © 2011 Springer-Verlag. Fil: Cerda, Ignacio Alejandro. Universidad Nacional de Río Negro. Sede Alto Valle. Instituto de Investigaciones en Paleobiología y Geología; Argentina Fil: Carabajal, A. Paulina. Provincia del Neuquén. Municipalidad de Plaza Huincul. Museo "Carmen Funes"; Argentina Fil: Salgado, Leonardo. Universidad Nacional de Río Negro. Sede Alto Valle. Instituto de Investigaciones en Paleobiología y Geología; Argentina Fil: Coria, Rodolfo Anibal. Universidad Nacional de Río Negro. Sede Alto Valle. Instituto de Investigaciones en Paleobiología y Geología; Argentina Fil: Reguero, Marcelo Alfred. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Departamento Científico de Paleontología de Vertebrados; Argentina Fil: Tambussi, Claudia Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina Fil: Moly, Juan J.. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; Argentina

Psilopterus lemoinei, the largest species in this genus, was a small terror bird weighing 8–9 kg, and was a ground bird with functionally tridactyl feet. New remains of this phorusrhacid, including an exceptionally preserved anterior part of a skull recovered from the Patagonian Killik Aike Norte locality (Santa Cruz Formation, late early Miocene), is now available for study. The main purpose of this paper is to provide a detailed morphological description of Psilopterus lemoinei. The new fossils show for the first time that the internal structure of the beak is hollow and reinforced with thin-walled trabeculae. The absence of zona flexoria palatina and zona flexoria arcus jugalis are key features related to the evolution of cranial akinesis. Homologies of the narial and fenestra antorbitalis boundaries have been clarified. Our re-examination allows the establishment of primary osteological homologies useful in comparative anatomy, functional morphology, and phylogenetic studies.

A new vertebrate faunal assemblage was recently discovered from the uppermost part of the late Miocene Puerto Madryn Formation. These deposits crop out along the southwestern coast of the Peninsula Valdes area near Punta Delgada (Chubut Province, Argentina). The exhumed vertebrate fauna includes a range of fish, bird and mammal taxa, of which the latter are most varied and abundant. The new findings represent the first record of continental fossil vertebrates in the Puerto Madryn Formation and this is the first assemblage of late Miocene continental vertebrates recorded to the south of Rio Negro Province. It also includes the southernmost record of Hydrochoeridae rodents, Dendrocygninae birds and Loricariidae fishes. The mammals suggest that the fossil-bearing sediments are Huayquerian in age. The climate during the accumulation of late Miocene deposits in this region is inferred to have been warmer and seasonally drier than that of today.

Madrynornis mirandus, one of the few fossil penguins known from a nearly complete articulated skeleton, represents a key taxon for understanding the stem-crown transition in penguins. Despite the w...

We examined the external anatomy of the endocast of the Greater Rhea (Rhea americana, Palaeognathae), during 3 main stages of its postnatal life, and compared it with information available on other palaeognathous birds. Series of scans with spiral computed tomographies were obtained from 3 skulls of different ages (chick, juvenile and adult) of R. americana; digital 3-dimensional reconstruction was performed and brain volumes were calculated from the models obtained. Qualitative assessment of the brain anatomy of R. americana indicates a conical and ventrally located bulbus olfactorius, laterally expanded hemispherium telencephali, well-developed eminentia sagittalis, and conspicuous cerebellum and tectum mesencephali. Anatomy of the chick brain was markedly different: less lateral expansion of the hemispherium telencephali, and lesser development of the eminentia sagittalis and auricula cerebelli. Little change between chicks and adults was observed in some brain regions such as the tectum mesencephali, while the eminentia sagittalis showed great increase in size. The large size of the eminentia sagittalis coupled with its increasing development during ontogeny could reflect its importance for visual processing functions and the way these improve during growth. Finally, the brain of R. americana is similar to that of Struthio and Dromaius, but differs from that of the Tinamidae and of Apteryx, allowing recognition of 3 distinct brain morphologies among the Palaeognathae.

The neurocranial fragment from the Late Miocene (Huayquerian SALMA, 9,0 to 6,8 Ma) of Estancia La Pastosa new locality, Puerto Madryn Formation, Patagonia, Argentina, is described. This is the first available fossil skull of Accipitridae in South America. Features as the elongated-triangular shape of the cranial roof, vast separation between the processus postorbitalis and between both fossae temporalis, and narrow and acuminate outline of the fossa temporalis allow to assign the fossil to Accipitridae Vieilloit, 1816. The well-preserved cavum cranii allowed construction of an endocast that partially reflects brain anatomy. The latter is very similar to those of extant and fossil species of Accipitridae. This fossil eagle is the only predator recorded at this new Miocene locality thus far. © 2009 by the Society of Vertebrate Paleontology. Fil: Picasso, Mariana Beatriz Julieta. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Departamento Científico de Paleontología de Vertebrados; Argentina Fil: Tambussi, Claudia Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina Fil: Dozo, Maria Teresa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentina

Cayaoa bruneti TONNI, 1979 is an early Neogene anseriform exhumed from marine sediments of the lower levels of the Gaiman Formation ("Patagoniano", Leonian Marine Stage, Chubut, Argentina). It was originally based on a partial tarsometatarsus that was not assigned to subfamily or tribe. We re-examine the holotype and study new tarsometatarsi, and previously undescribed skeletal elements including partial femora, tibiotarsi, partial humeri and carpometacarpi. Cayaoa bruneti was a strictly foot-propelled diving bird that exhibited an extreme reduction of the fore-limb, being probably the earliest recorded flightless duck. Similarly reduced wings are found in the distantly related anseriform Cnemiornis OWEN, 1866 of subrecent deposits of New Zealand, Chendytes MILLER, 1925 of the Pleistocene of California, and the moa-nalos of the Late Quaternary of Hawaii. Fil: Noriega, Jorge Ignacio. Provincia de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Universidad Autónoma de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción; Argentina Fil: Tambussi, Claudia Patricia. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Cozzuol, Mario Alberto. Pontificia Universidad Católica de Río Grande del Sur; Brasil

A bioclimatic analysis of the crested tinamous was conducted to explore climatic factors underpinning the distribution of both Eudromia elegans and E. formosa and to evaluate its potential application in paleontological studies. The study utilized records throughout the entire known range of Eudromia spp. in southern South America. Relationships between 20 environmental parameters and the presence of Eudromia species were established, mapping and characterizing their spatial distribution in a geographic information system using BIOCLIM and MAXENT algorithms. The MAXENT prediction map shows a more homogeneous pattern while BIOCLIM showed a patchier pattern. The models applied here generated maps that adjust to the well-known previous distributions of both species. Nevertheless, for Eudromia elegans, the distribution predicted by MAXENT includes areas where it is actually considered absent, and the BIOCLIM prediction does not include some areas where it is presumed present. Eudromia formosa were found in warmer and wetter sites than E. elegans. Low precipitation areas were identified as suitable for Eudromia elegans. Strong differences between the climatic profiles for both Eudromia spp distributions occurred, with the precipitation the most important influence. E. formosa tolerates the highest maximum temperatures, whereas E. elegans supports the lowest temperatures.

The penguin skeleton studied here constitutes the fourth partial skeleton found in Patagonia, and the third one with an associated humerus and tarsometatarsus. The finding of this partial skeleton identified with certainty asPalaeospheniscus patagonicusMoreno and Mercerat, 1891 (Aves, Sphenisciformes) allows the first description of elements other than the tarsometatarsus. The material comes from the basal sector of the Gaiman Formation (Early Miocene), located along the Atlantic coast of Chubut Province, south of Rawson city. This unit comprises a succession of shales, fine tuffs, sandstones, tuffaceous sandstones, and coquinas deposited in a shallow marine environment. These beds contain abundant marine vertebrates (sharks, dolphins, rays, birds), mollusk casts, and oyster beds. The skeleton includes: rostrum, two thoracic vertebrae, right coracoid without the distal end, left humerus, right femur, right tarsometatarsus, left fragmentary scapula, left coracoid, left radius without the distal end, proximal portion of left ulna, proximal end of left femur, and preacetabular part of the synsacrum.P. patagonicuswould have been a medium-sized penguin weighing about 5 kg that inhabited the breeding colonies established in the nearby Bryn Gwyn area during the early Miocene. Despite the abundance of penguin remains known for Argentina, and the fact that they are among the birds with a better fossil record, this skeleton is an exceptional case. This finding allows a readjustment of the taxonomic criteria applicable to fossil and living species.

The anatomy of a new, enormous phorusrhacid (Aves: Cariamae) from the Middle Miocene Collon Cura Formation of northwestern Patagonia (Rio Negro province, Argentina) is described. The new phorusrhacid is known by a single specimen that consists of a nearly complete skull associated with a tarsometatarsus and a pedal phalanx. The new fossil is the largest known phorusrhacid and its morphology resembles more that of taxa traditionally grouped within phorusrhacines. Its skull—by far the best preserved among large phorusrhacids—provides a great deal of previously unknown anatomical information and indicates that reconstructions of the skull of gigantic phorusrhacids based on their smaller relatives are unwarranted.

Many studies on avian microanatomy have established a relationship between high bone compactness (i.e., higher degree of osteosclerosis) and diving behavior. Greatest degrees of compactness have been observed in the femora and humeri of penguins, femur of Hesperornis Marsh, 1872, and of Polarornis gregorii Chatterjee, 2002, and to a somewhat lesser degree, in the humeri of flightless Pan-Alcidae. Within Anatidae, humeral and femoral compactness among diving species is greater than among non-diving species, whereas flightless diving species have a greater degree of compactness than their flying close relatives. In Cayaoa bruneti Tonni, 1979, an extinct flightless foot-propelled, diving anatid with extreme forelimb reduction, osteosclerosis is as great as that of penguins. Although osteosclerosis in the humerus of wing-propelled divers could be part of adaptations to flightlessness, osteosclerosis in the femur of both foot- and wing-propelled divers could be part of the consequences of flightlessness and which is a result of selection to counter buoyancy. Múltiples estudios en microanatomía aviana han establecido una relación entre una alta compactación ósea (es decir, un grado considerable de osteosclerosis) y el comportamiento buceador. Los mayores grados de compactación han sido observados en fémures y húmeros de pingüinos actuales y fósiles, fémures de Hesperornis Marsh, y de Polarornis gregorii Chaterjee, y en un grado algo menor, en húmeros de Pan-Alcidae no voladores. Dentro de los Anatidae, la compactación humeral y femoral es mayor entre las especies buceadoras que entre las no buceadoras, mientras que las especies buceadoras no-voladoras presentan un grado de compactación mayor que sus parientes cercanos voladores. En Cayaoa bruneti Tonni, un anatido extinto no volador, buceador propulsado por las patas, con una reducción extrema de los miembros anteriores, la osteosclerosis en el fémur es tan alta como la de pingüinos. La osteosclerosis en el fémur de los buceadores propulsados por las patas y los propulsados por las alas puede ser parte de las consecuencias de la pérdida de vuelo, seleccionada positivamente para contrarrestar la flotabilidad. Fil: de Mendoza, Ricardo Santiago. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Departamento Científico de Paleontología de Vertebrados; Argentina Fil: Tambussi, Claudia Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina

Terror birds constitute the most outstanding group of the South American Cenozoic avifauna. Considered as apex predators, their hunting skills have recently been examined, but their diversity is still unresolved. Here we report a new terror bird from the late Pliocene of Argentina, represented by the most complete articulated skeleton of one yet found. Our phylogenetic analysis places this taxon among derived phorusrhacids (Mesembriornithinae). One of the most striking cranial features of the new species is the suppression of intracranial kinesis due to the presence of an independent ossified bone that increases the structural link between the lacrimal and jugal bars, and the absence of both palatal hinges. The new species possesses ossified tracheal rings and a tracheobronchial syrinx, as well as sclerotic ossicles to adjust the shape of the cornea during its diurnal vision, and reveals a mean hearing sensitivity (~2300 Hz) below the average for living species. The discovery of this new species provides new insights for studying the anatomy and phylogeny of phorusrhacids and a better understanding of this group's diversification. Fil: Degrange, Federico Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina Fil: Tambussi, Claudia Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina Fil: Taglioretti, Matias Luciano. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Geología de Costas y del Cuaternario. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto de Geología de Costas y del Cuaternario; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Dondas, Alejandro. Provincia de Buenos Aires. Municipalidad de General Pueyrredon. Secretaría de Cultura. Museo Municipal de Ciencias Naturales Lorenzo Scaglia; Argentina Fil: Scaglia, Fernando. Provincia de Buenos Aires. Municipalidad de General Pueyrredon. Secretaría de Cultura. Museo Municipal de Ciencias Naturales Lorenzo Scaglia; Argentina

Morphological diversity of 47 pygoscelid skulls was tested empirically through geometric morphometrics approach. Using 14 landmarks, shape is analyzed independently of other aspects of the body form. The shape disparity within and between the three living species of Pygoscelis is explored as well as how the structure of the skull is related to food preferences. Comparison of the three mean configurations of the species suggests that differences among groups are small relative to the variability within each group. However, some differences at the posterior portion of the braincase are indicated. Sexual dimorphism within each species is not noticeable. Comparison with a piscivorous species (Spheniscus humboldti) shows two cranial patterns: pygoscelid type with wide nasal gland depression limited by well-marked edges, shallow temporal fossae, and a poorly developed temporal nuchal crest; the second type represented by Spheniscus humboldti with laterally open nasal gland depression, deep temporal fossae, and a well-developed temporal nuchal crest.

Modern penguins are typically small to medium-sized birds, and nearly all known modern specimens are smaller than the most archaic Paleogene relatives. Here we report an incomplete humerus, associated femur and tibiatarsus of a new spheniscid, Crossvallia unienwillia nov. gen. and sp., from the Late Paleocene (~55 million years, Myr) of Antarctica, extending the record of spheniscids by about 15 Myr. Its large size (length ~140 cm) supports the idea that large body size in penguins was acquired independently at different times (Late Paleocene and Late Eocene) under dramatically different environmental conditions. Comparison of its osteological anatomy suggests that the new taxon is closely related to the extinct Anthropornithinae rather than to other penguin lineages.

The aim of this contribution is to verify the presence of the suborbital arch and the ethmomandibularis and pseudomasseter muscles in the holotype of Nandayus vorohuensis (Tonni and Noriega, 1996) in order to gain a better understanding of the capabilities of its cranio-mandibular complex and provide new tools for the discussion on the evolution of these unique structures. These apomorphies enables Psittaciformes to exert strong bite forces. Muscle reconstruction was performed based on the presence of muscle attachment scars and on the basis of the jaw-muscle descriptions of the extant Myiopsitta. Our results indicate that the suborbital arch is absent and the ethmomandibularis and the pseudomasseter muscles were present. This condition is shared with the extant Neotropical Pionites and Myiopsitta, so we assume that their trophic habits are similar. The heterogeneous distribution of these characters reaffirms the idea that the direction of the evolutionary changes may have varied independently in the crown group Psittaciformes more than once. Fil: Carril, Julieta. Universidad Nacional de la Plata. Facultad de Ciencias Naturales y Museo. Cátedra de Histología y Embriología Animal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Degrange, Federico Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina Fil: Tambussi, Claudia Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina

Middle Cenozolc marine fossil-bearing beds crop out in the Cerro Plataforma (western Chubut Province. Argentina) at about 1,400 m a.s.l. They are located 500 km far from the modern Atlantic coast and only 50 km from the Pacific Ocean. Well preserved penguin bones and a shark tooth were found therein. Invertebrates include corals, bryozoans, abundant mollusks, echinoids, and crabs. Morphogeometric analysis and comparative description confirmed that the penguin humerus is referable to Palaeospheniscus bergi Moreno and Mercerat, 1891. Most of the fossils indicate a Miocene age. However, there is a debate about if the bearing beds are of Pacific or Atlantic origin. Fossil invertebrates identifiable at species level reveal Pacific affinity, the shark species is cosmopolitan, and Palaeospheniscus bergi is known from early Miocene Atlantic units of southern South America. Yet, Palaeospheniscus Moreno and Mercerat, 1891 is also known from Miocene Pacific beds but it has not been identified at specific level yet. This is the highest site in topographic terms in which penguin fossils occur. This indicates a remarkable uplift for the area, probably from the middle Miocene. Capas portadoras de fósiles marinos del Cenozoico medio afloran en cerro Plataforma (oeste de la Provincia del Chubut, Argentina) a unos 1.400 m s.n.m. Están localizadas a 500 km de la costa pacífica actual y a solo 50 km de la pacífica. Fueron hallados restos de pingüinos y un diente de tiburón bien preservados. Entre los fósiles de invertebrados se incluyen corales, briozoos, abundantes moluscos, equinoideos y cangrejos. Los análisis morfogeométricos y la descripción comparada confirmaron la asignación del húmero de pingüino a Palaeospheniscus bergi Moreno y Mercerat, 1891. La mayoría de los fósiles indican una edad Miocena. Sin embargo, existe un debate sobre si estas capas poseen un origen pacífico o atlántico. Los fósiles de invertebrados identificables a nivel de especie presentan afinidades pacíficas, la especie de tiburón es cosmopolita, y Palaeospheniscus bergi es conocido en unidades atlánticas del Mioceno temprano de América del Sur. A pesar de esto, el género Palaeospheniscus Moreno y Mercerat, 1891 es también conocido en capas miocenas del Pacífico, aunque la especie no ha sido aún identificada. En términos topográficos, este es el sitio más elevado en el que se han hallado restos de pingüinos. Esto indica un notable levantamiento del área, probablemente durante el Mioceno medio.

Pseudoseisuropsis wintu sp. nov. is described from cranial material that had formerly been designated as a paratype of the extinct Pseudoseisuropsis nehuen. Thorough comparisons were made between the cranial specimens ascribed to Pseudoseisuropsis and many extant furnariid species. This new species is lower Pleistocene in age and increases the known diversity of Pseudoseisuropsis to three species. Cladistic analyses were performed using 43 cranial characters and a backbone constraint based on a well-supported phylogeny from a recent molecular analysis. In the most parsimonious tree, Pseudoseisuropsis was retrieved as a sister group of woodcreepers (Dendrocolaptinae) with low support. However, slightly suboptimal hypotheses, which could not be completely ruled out, suggest that this genus may be more closely related to other clades of Furnariidae. Hence, we agree with previous authors in regarding Pseudoseisuropsis as Furnariidae Incertae sedis. In addition, two fragmentary fossils ascribed to Pseudoseisuropsis were included in taxonomic comparisons: P. cuelloi, in order to assess the possibility that P. wintu sp.nov. belongs to that species, and another paratype of P. nehuen, to reassess its taxonomic identity. Fil: Stefanini, Manuel Ignacio. Universidad de Buenos Aires. Facultad de Cs.exactas y Naturales. Departamento de Geología. Laboratorio de Paleontología Evolutiva de Vertebrados; Argentina Fil: Gomez, Raul Orencio. Universidad de Buenos Aires. Facultad de Cs.exactas y Naturales. Departamento de Geología. Laboratorio de Paleontología Evolutiva de Vertebrados; Argentina Fil: Tambussi, Claudia Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina

Several advances have been made on the understanding of the biotic and environmental history of South America and Antarctica including the discovery of additional fossil sites coupled with progress from multidisciplinary analyses encompassing tectonic, isotopic, and radiochemical dating and molecular studies in modern forms. This also changed the knowledge about birds. Characters of the South American (SAn) avian fossil record are: (1) presence of taxa with uncertain affinities and the absence of Passeriformes during the Paleogene; (2) progressive and accelerated increase of species starting at the Neogene (Miocene); (3) dispersal of important extinct lineages (e.g. Phorusrhacidae, Teratornithidae) to North America after the connection between both Americas; (4) scarce endemic species that are members of clades with major diversification during the Neogene (e.g., Cariamiformes) or that inhabits mainly in the southern hemisphere (e.g., Anhingidae); (5) highly diverse living groups with limited (e.g., Passeriformes) or none (e.g., Apodiformes) fossil record whose stem-groups are registered in Europe; (6) Absence of the most extant SAn bird lineages; (7) predominate of the zoophagous birds (>60 %) in all the associations (13) under scrutiny. Changes in diversity of the SAn birds during the Cenozoic could have been the result of the action of different processes (dispersal, vicariance, extirpations or extinctions) that affect groups in different ways.