Geometric morphometric analysis as a proxy to evaluate age-related change in molar shape variation of low-crowned Notoungulata (Mammalia)

Shape and age variation in dentition of Paleogene extinct native South American ungulates (Notoungulata) has been traditionally described using qualitative and quantitative approaches, and has played a controversial role in the systematics of several groups. Such is the case of the Notopithecidae, a group of notoungulates with low‐crowned teeth, known from the middle Eocene of Patagonia (Argentina). In this group, as well as in other contemporary families, extreme morphological changes associated to increasing dental wear were originally assumed to represent taxonomic differences; thus, dozens of species were erected, clearly reflecting the difficulty of defining discrete characters. In this contribution, a total of 89 upper molars and 91 lower molars were analyzed distributed in two factors, wear and species; three species of notopithecids were considered as study case, Notopithecus adapinus, Antepithecus brachystephanus, and Transpithecus obtentus, based on the large and well‐identified sample of upper and lower molars for each species. We have coupled geometric morphometric analyses with traditional comparative methods to get a better understanding and interpretation of both the changes in tooth shape contour and the link between shape and ontogeny. In addition, we evaluate the utility of this approach to identify which changes are strictly wear‐related and also test the qualitative characteristics used for diagnosing and differentiating notopithecid species. Our study yielded consistent results when applying independent geometric morphometric analyses on complex structures such as brachydont molar teeth. The landmark data is highly congruent with alternative sources of evidence, such as morphological studies using discrete characters. In notopithecid species, wear is the main factor affecting molar shape, followed by species (in lower molars) and allometry; in addition, lower teeth morphology is more definitive in separating species than upper molars, a fact that entails a key point for systematic studies of Paleogene brachydont notoungulates.Facultad de Ciencias Naturales y Muse

Caracterización ambiental del Arroyo Sarandí: una interpolación espacial

El arroyo Sarandí atraviesa a lo largo de su trayecto zonas de densos asentamientos poblacionales e industriales. Durante su recorrido recibe numerosos vertidos industriales, que previo a su vuelco poseen escaso o nulo tratamiento. Debido a estas continuas descargas de efluentes provenientes de diversas industrias ubicadas en zonas aledañas, posee en su lecho diversos metales pesados tales como cromo, zinc, cobre, plomo y níquel. Dependiendo de su concentración, estos metales poseen efectos nocivos sobre la salud y el ecosistema. Dentro de este contexto, para determinar su estado actual ambiental se tomaron 17 muestras de sedimentos en tres sitios y de vegetación en la zona de Sargento Ponce, durante un lapso de ocho meses. Los sitios de muestreo se ubicaron de forma equidistante en la intersección del arroyo con las calles Heredia, La Blanqueada y Sargento Ponce. Las muestras se analizaron mediante absorción atómica de llama acetileno para la detección de cromo, zinc, cobre, plomo y níquel en el laboratorio Ambiental de la Municipalidad de Avellaneda. Se analizaron los valores en un entorno GIS para evaluar su distribución espacial, interpolando los valores obtenidos mediante IDW (Inverse Distance Weighted). A través de esta técnica se realizaron mapas temáticos con la distribución de los metales pesados en el tramo de arroyo analizado, incluyendo predicciones de concentraciones de estos metales en zonas donde el arroyo se encuentra entubado. Los resultados indican que, en general, las mayores concentraciones de metales se encuentran en el tramo comprendido entre las calles Heredia y La Blanqueada, variando el patrón de distribución de concentraciones según el metal entre La Blanqueada y la desembocadura del arroyo. El cromo es el metal que posee mayor promedio de concentración en los sedimentos. También se obtuvieron altos valores de concentración de zinc en todo el trayecto del arroyo, y en menor concentración los metales cobre, níquel y plomo.The Sarandi stream traverses along areas of dense population and industrial settlements. During his path receives numerous industrial discharges, that have little or no treatment. Because of these continuous discharges of effluents from industries in surrounding areas, the Sarandi stream has various heavy metals such as chromium, zinc, copper, lead and nickel. Depending on its concentration, these metals have harmful effects on health and the ecosystem. In this context, to determine the current environmental status of Sarandi stream, 17 sediment samples were taken at three sites over a period of 8 months. The sampling sites were located equidistantly at the intersection of the stream with Heredia, La Blanqueada and Sargento Ponce streets. The samples were analyzed by atomic absorption for detection of chromium, zinc, copper, lead and nickel in the Environmental Laboratory of the Municipality of Avellaneda. Obtained values were analyzed in a GIS environment to assess their spatial distribution, interpolating the obtained values by IDW (Inverse Distance Weighted). Through this technique, thematic maps were rendered with the distribution of heavy metals in the section of stream analyzed, including predictions of concentrations of these metals in areas where the stream is tubed. The results indicate that the highest concentrations of metals are in the section between Heredia and La Blanqueada streets, varying the pattern of distribution of concentrations between La Blanqueada and the stream mouth. Chromium is the metal that has higher average concentration in sediments. Also high zinc concentration values were obtained throughout the course of the stream, but copper, nickel and lead has a lower concentrations.O fluxo de Sarandi atravessa áreas de densa população e assentamentos industriais. Durante sua turnê recebe inúmeras descargas industriais, que, antes da descarga têm pouco ou nenhum tratamento. Devido a estas descargas contínuas de efluentes de diversas indústrias em áreas circunvizinhas, o córrego Sarandi tem em seu leito diversos metais pesados como cromo, zinco, cobre, chumbo e níquel. Dependendo da concentração, estes metais têm efeitos nocivos para a saúde e para o ecosistema. Dentro deste contexto, para determinar o estado ambiental actual das Sarandi fluxo foram tomadas 17 amostras de sedimentos em três locais, e vegetação na área de Sgt. Ponce, ao longo de um período de 8 meses. Os sítios de amostragem foram localizados de forma equidistante na interseção do fluxo com as ruas Heredia, La Blanqueada e Sargento Ponce. As amostras foram analisadas por absorção atômica do chama acetileno para a detecção de cromo, zinco, cobre, chumbo e níquel no Laboratório Ambiental do Município de Avellaneda. Os valores foram analisados em um ambiente GIS para avaliar a sua distribuição espacial , interpolando os valores obtidos pela IDW (Distância Inverse ponderada). Através desta técnica foram feitos mapas temáticos com a distribuição de metais pesados, incluindo previsões de concentrações destes metais em áreas onde o fluxo é entubado. Os resultados indicam que, em geral, as maiores concentrações de metais estão incluídas na seção de rio entre as ruas Heredia e La caiadas, variando o padrão de distribuição de acordo com as concentrações de metais entre La Blanqueada ea foz do riacho. O cromo é um metal que tem concentração média mais elevada nos sedimentos. Os valores de concentração elevada de zinco também foram obtidos ao longo do curso da corrente, e em concentrações mais baixas de metais de cobre, níquel e chumbo.Facultad de Ciencias Naturales y Muse

Chaetophractus tarijensis (Xenarthra, Dasypodidae). An endemism from the Tarija Valley (Bolivia)? Paleobiogeographical implications

Chaetophractus tarijensis (Ameghino) is a dasypodid restricted to the Pleistocene of the Tarija Valley (Bolivia). In this contribution we study the type specimen of C. tarijensis and referred specimens to this species, and establish comparisons with extant Dasypodidae Euphractinae. The analysis of the present study reveal that the characters used by Florentino Ameghino (e.g. the underdevelopment of the angular portion of the ramus of the mandible and the cylindrical shape of the last molariform) do not allow the differentiation with Chaetopractus (Desmarest). Also, a principal components analysis was performed with cranial measurements. All these evidence support the hypothesis that C. tarijensis is a synonym of C. villosus. From a paleobiogeographic point of view, these results are important because it indicates that C. tarijensis is not one of the few supposedly endemic species of the of the Tarija Valley.Chaetophractus tarijensis (Ameghino) é um dasipodídeo restrito ao Pleistoceno do Vale de Tarija (Bolívia). A partir do estudo do exemplar tipo de C. tarijensis, dos materiais referidos a esta espécie e da comparação com outros Dasypodidae Euphractinae atuais, se conclui que os caracteres utilizados por Florentino Ameghino (e.g. o parco desenvolvimento da porção angular do ramo ascendente da mandíbula e a forma cilíndrica do último molariforme) não permitem diferenciá-la de Chaetopractus (Desmarest). Estas diferenças são também consistentes com os resultados obtidos por meio de uma análise de componentes principais, na qual C. tarijensis seria um sinônimo de C. villosus. Tais resultados são importantes do ponto de vista paleobiogeográfi co, dado que seria outro caso de espécie originalmente proposta como endêmica do Vale de Tarija, porém que, segundo nossos recentes estudos, não seria válida.Facultad de Ciencias Naturales y Muse

Chaetophractus tarijensis (Xenarthra, Dasypodidae). An endemism from the Tarija Valley (Bolivia)? Paleobiogeographical implications

Chaetophractus tarijensis (Ameghino) is a dasypodid restricted to the Pleistocene of the Tarija Valley (Bolivia). In this contribution we study the type specimen of C. tarijensis and referred specimens to this species, and establish comparisons with extant Dasypodidae Euphractinae. The analysis of the present study reveal that the characters used by Florentino Ameghino (e.g. the underdevelopment of the angular portion of the ramus of the mandible and the cylindrical shape of the last molariform) do not allow the differentiation with Chaetopractus (Desmarest). Also, a principal components analysis was performed with cranial measurements. All these evidence support the hypothesis that C. tarijensis is a synonym of C. villosus. From a paleobiogeographic point of view, these results are important because it indicates that C. tarijensis is not one of the few supposedly endemic species of the of the Tarija Valley.Chaetophractus tarijensis (Ameghino) é um dasipodídeo restrito ao Pleistoceno do Vale de Tarija (Bolívia). A partir do estudo do exemplar tipo de C. tarijensis, dos materiais referidos a esta espécie e da comparação com outros Dasypodidae Euphractinae atuais, se conclui que os caracteres utilizados por Florentino Ameghino (e.g. o parco desenvolvimento da porção angular do ramo ascendente da mandíbula e a forma cilíndrica do último molariforme) não permitem diferenciá-la de Chaetopractus (Desmarest). Estas diferenças são também consistentes com os resultados obtidos por meio de uma análise de componentes principais, na qual C. tarijensis seria um sinônimo de C. villosus. Tais resultados são importantes do ponto de vista paleobiogeográfi co, dado que seria outro caso de espécie originalmente proposta como endêmica do Vale de Tarija, porém que, segundo nossos recentes estudos, não seria válida.Facultad de Ciencias Naturales y Muse

Chaetophractus tarijensis (Xenarthra, Dasypodidae). An endemism from the Tarija Valley (Bolivia)? Paleobiogeographical implications

Chaetophractus tarijensis (Ameghino) is a dasypodid restricted to the Pleistocene of the Tarija Valley (Bolivia). In this contribution we study the type specimen of C. tarijensis and referred specimens to this species, and establish comparisons with extant Dasypodidae Euphractinae. The analysis of the present study reveal that the characters used by Florentino Ameghino (e.g. the underdevelopment of the angular portion of the ramus of the mandible and the cylindrical shape of the last molariform) do not allow the differentiation with Chaetopractus (Desmarest). Also, a principal components analysis was performed with cranial measurements. All these evidence support the hypothesis that C. tarijensis is a synonym of C. villosus. From a paleobiogeographic point of view, these results are important because it indicates that C. tarijensis is not one of the few supposedly endemic species of the of the Tarija Valley.Chaetophractus tarijensis (Ameghino) é um dasipodídeo restrito ao Pleistoceno do Vale de Tarija (Bolívia). A partir do estudo do exemplar tipo de C. tarijensis, dos materiais referidos a esta espécie e da comparação com outros Dasypodidae Euphractinae atuais, se conclui que os caracteres utilizados por Florentino Ameghino (e.g. o parco desenvolvimento da porção angular do ramo ascendente da mandíbula e a forma cilíndrica do último molariforme) não permitem diferenciá-la de Chaetopractus (Desmarest). Estas diferenças são também consistentes com os resultados obtidos por meio de uma análise de componentes principais, na qual C. tarijensis seria um sinônimo de C. villosus. Tais resultados são importantes do ponto de vista paleobiogeográfi co, dado que seria outro caso de espécie originalmente proposta como endêmica do Vale de Tarija, porém que, segundo nossos recentes estudos, não seria válida.Facultad de Ciencias Naturales y Muse

Internal Morphology of Osteoderms of Extinct Armadillos and Its Relationship with Environmental Conditions

The most complete and continuous fossil record of armadillos is composed mostly by isolated osteoderms, frequently found in paleontological and archaeological sites that bear continental South American mammals. Their external morphology has been used to define several species. In the last decade, many authors have focused on the internal structure of vertebrate osteoderms using histological and paleohistological studies. These studies allowed identification of useful features in systematic and phylogenetic contexts. In armadillos, osteoderms are constituted by compact bone tissue (primary and secondary osteons, and concentric layers or lamellae) that delimits cavities, which could contain different soft tissues (adipose tissue, hair follicles, bone marrow, and sweat and sebaceous glands). Traditional paleohistological techniques have allowed the recognition of homologous cavities to those found in osteoderms of current species and from comparison deduce which kind of tissue could had occupied them.We have recently utilized 3D reconstructions in osteoderms of extant species of armadillos to analyze the micromorphology, disposition, and the relationship of different cavities and understand them in depth. Here, we present the results of the application of paleohistology and microtomography in osteoderms of representatives of diferent taxa of extinct Dasypodidae (Astegotheriini, Stegotheriini, "Utaetini", Euphractini, Eutatini), which allowed us to compare homologous structures based on their three-dimensional reconstruction. The results, added to the previous external morphology studies, have allowed us to define morphological patterns (consistent within each linage). The variation of the volume and extension of cavities associated with different tissues could be strongly associated with changes in the climate and environmental conditions of the species distribution areas.Facultad de Ciencias Naturales y Muse

Comparative histology and ontogenetic change in the carapace of armadillos (Mammalia: Dasypodidae)

Among extant mammals, the presence of osteoderms is limited to armadillos (Xenarthra, Dasypodidae), being one of its distinctive features. The osteoderms are articulated to form a carapace that covers their body dorsally. In this paper we study the integumentary structures of the armadillos Chaetophractus vellerosus, Chaetophractus villosus, Euphractus sexcinctus, and Zaedyus pichiy (Euphractinae), Dasypus hybridus, and Dasypus novemcinctus (Dasypodinae) within a comparative framework, aiming to identify patterns common to the family and to the subfamilies Dasypodinae and Euphractinae, as well as peculiarities of each species. Differences between the two subfamilies were observed in the dorsal integument, related to the production of blood cells and the mobility of the carapace. The Euphractinae present more numerous and larger cavities filled with adipose tissue in the osteoderms, as well as more marginal follicles than the Dasypodinae. These provide thermal insulation that could be related to their distribution in cooler climates. The sebaceous glands associated with surface follicles are also more developed in the Euphractinae and could be related to preventing the desiccation of the cornified scales in arid climates.Fil: Krmpotic, Cecilia Mariana. 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. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Ciancio, Martin Ricardo. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Laboratorio de Anatomía Comparada; ArgentinaFil: Carlini, Alfredo Armando. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Laboratorio de Anatomía Comparada; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Castro, Mariela C.. Universidade de Sao Paulo; BrasilFil: Scarano, Alejo Carlos. 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. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de Avellaneda; ArgentinaFil: Barbeito, Claudio Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias. Departamento de Ciencias Básicas. Cátedra de Histología y Embriología; Argentin

Morphology of the tympanic-basicranial region in <i>Mirounga leonina</i> (Phocidae, Carnivora), postnatal ontogeny and sexual dimorphism

The auditory region of pinnipeds has seldom been described. Here we describe and analyze the ontogenetic trajectory of the tympanic bulla of the southern elephant seal, Mirounga leonina (Phocidae, Mammalia). This species is extremely sexually dimorphic and highly polygynous (organized in harems). We examined 118 specimens, arranged in three age classes (CI, CII, and CIII), ranging from newborn to adults (males and females). To analyze the overall size and shape of the tympanic bulla we performed a geometric morphometric analysis including 87 skulls. Females reach definitive shape and size of the bulla at earlier ontogenetic stages than males, in agreement with their earlier involvement in reproductive activities. The internal anatomy of the tympanic region (e.g. form and extension of the paries) does not show remarkable differences between sexes or age classes. The greatest differences between age classes are related to bone thickness, resulting from the apposition of new annual layers. An examination of possible sex-related external differences among age classes shows significant shape differences between males and females in CIII. The morphology observed in neonates is conserved across all individuals from CI, which included specimens up to 1 year old. Clear morphological differences were observed between CI individuals, on one hand, and CII individuals plus CIII females on the other. During cranial development of both male and females, the glenoid cavity expands and compresses the bulla; this condition reaches its maximum expression in CIII males. CIII males showed the greatest morphological differences, with respect to both CI and CII individuals, and CIII females.Facultad de Ciencias Naturales y Muse

The tympanic region of <i>Otaria byronia</i> (Otariidae, Carnivora) – morphology, ontogeny, age classes and dimorphism

Here we describe and explore for the first time the ontogeny and sexual dimorphism of the auditory region of Otaria byronia. We studied the tympanic region of skulls of 237 specimens of different ages and sexes. Geometric morphometric methods were used to analyze the tympanic bulla. In addition, 3D reconstructions of the tympanic bulla were performed using computed tomography analysis scans and a serial wearing technique. We provide a description of the external and internal morphology of the tympanic bulla in both sexes and across different stages (bioclasses). The average shape of the bulla in O. byronia has a subtriangular contour, with variations between sexes and ages. Each stage (bioclasses I, II, and III) is characterized by the respective mean shape of the tympanic bulla and designated as a morphoclass (1, 2, and 3). In all cases, the ectotympanic shows greater surface area than the endotympanic, as in other otariids, in contrast to Phocidae. During ontogeny, the relative size of the ectotympanic increases, growing in all directions and covering the endotympanic. This pattern is seen to the greatest extent in adult males, in which the ectotympanic forms an extremely well-developed apophysis jugulare. No differences in internal morphology of the tympanic cavity were recorded between ages and sexes. The bulla does not increase in thickness in successive age classes; in fact, the walls are extremely thin in the adult stages, despite the extensive development of its processes. This pattern is opposite that observed in Phocidae. In morphoclass 3, adult males older than 7 years undergo hypermorphic change that results in a peramorphic condition when compared to adult females. These changes probably follow the same pattern shown by the rest of the skull and contribute to the marked sexual dimorphism of the species.Facultad de Ciencias Naturales y Muse

Adaptations to a semiaquatic lifestyle in the external ear of southern pinnipeds (Otariidae and Phocidae, Carnivora): Morphological evidences

Pinnipeds are semiaquatic carnivorans that spend most of their lives in water and use coastal terrestrial, or ice pack, environments to breed, molt and rest. Certain characteristics of the ear have been linked to ecological aspects. In our contribution we focus on the study of the macroscopic and microscopic morphology of the external ear (with the exception of the osseous outer ear canal) of six species of Southern pinnipeds. In order to recognize the different components of tissues, sections were stained following several routine protocols. In addition, double-staining and enzymatic clearing (Alcian blue-alizarin red) was performed to assess the arrangement of skeletal elements in the OEC. The basic structure of the pinna in the southern otariids studied match those previously analyzed for Northern Hemisphere species. The cartilage macro anatomy of the OEC of Mirounga leonina and Arctocephallus gazella is different from that of the Northern Hemisphere species, with only one plate of cartilage, but markedly different between them. The histology of the otariids OEC is homogeneous along the entire extension, but phocids has three different regions (distal, middle, and proximal). The cartilage histology of most phocids is also different from that of analyzed otariids, with an elastic cartilage that resembles a myxoid-like tissue, but is not present in M. leonina, were the tissue around the OEC is very rich in adipocytes. The southern elephant seal M. leonina OEC has a combination of features similar to both the rest of the phocids and to the otariids. An auditory organ that is functional both over and under water could be essential for social behavior in these species.Fil: Loza, Cleopatra Mara. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de la Plata. Facultad de Cs.naturales y Museo. Laboratorio de Morfologia Evolutiva y Desarrollo.; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; ArgentinaFil: Krmpotic, Cecilia Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Universidad Nacional de la Plata. Facultad de Cs.naturales y Museo. Laboratorio de Morfologia Evolutiva y Desarrollo.; ArgentinaFil: Galliari, Fernando Carlos. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de la Plata. Facultad de Cs.naturales y Museo. Laboratorio de Morfologia Evolutiva y Desarrollo.; ArgentinaFil: Andrés Laube, Pedro F.. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias; ArgentinaFil: Negrete, Javier. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; ArgentinaFil: Scarano, Alejo Carlos. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Universidad Nacional de la Plata. Facultad de Cs.naturales y Museo. Laboratorio de Morfologia Evolutiva y Desarrollo.; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Avellaneda; ArgentinaFil: Loureiro, Julio. No especifíca;Fil: Carlini, Alfredo Armando. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de la Plata. Facultad de Cs.naturales y Museo. Laboratorio de Morfologia Evolutiva y Desarrollo.; ArgentinaFil: Barbeito, Claudio Gustavo. Universidad Nacional de La Plata; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin