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Mar del Plata, Argentina

Kramarz A.G.,Museo Argentino de Ciencias Naturales Bernardino Rivadavia | Vieytes E.C.,Seccion Mastozoologia
Journal of Vertebrate Paleontology | Year: 2014

A new caviomorph rodent, Dudumus ruigomezi, gen. et sp. nov., is described from the Sarmiento Formation, Trelew Member (early Miocene), of the Argentinian Patagonia. This new taxon is represented by upper and lower cheek teeth, mandible, and maxillary remains. It is characterized by retention of deciduous premolar, and low-crowned and terraced lower and upper cheek teeth with well-differentiated cusps, as in Caviocricetus lucasi; upper molariforms with the mesolophule and metacone fused with the posterior-most crest, as in C. lucasi; lower molars with lingual cusp enlarged and metalophulid II longer in m2 than in m1and m3, as in Prospaniomys priscus; and dp4 with metalophulid I separated from the metaconid and a spur projecting posterolingually from the posterior wall of metalophulid I, between the protoconid and anteroconid. The incisor enamel microstructure is derived, with the interprismatic matrix perpendicular (at a right angle) to the prisms, as in other octodontoids. A cladistic analysis corroborates that D. ruigomezi represents an octodontoid rodent with unusual tooth morphology. This analysis demonstrates that the early evolutionary history of Octodontoidea was characterized by the differentiation of successive lineages that survived until the early or middle Miocene, with no direct relationships with modern Octodontidae and Echimyidae. This analysis also suggests that fossil taxa previously classified as octodontoids are instead more closely related to the other caviomorph rodents. © 2014 Copyright Taylor & Francis Group, LLC.

Fernandez Blanco M.V.,Museo de La Plata | Fernandez Blanco M.V.,CONICET | Bona P.,Museo de La Plata | Bona P.,CONICET | And 4 more authors.
Herpetological Journal | Year: 2015

Caiman is one of the five extant genera of alligatorid crocodylians. While several quantitative and qualitative studies exist on morphological variation in the genus, little is known about ontogenetic effects. Here, we quantify ontogenetic variation in morphology for Caiman yacare and C. latirostris in a phylogenetic context. A linear regression analysis on twelve skull measurements of C. yacare and C. latirostris against a measure of size (the first axis of a PCA of all variables) showed high correlation coefficients (r2=0.89–0.99) and negative allometry. Eight allometric trajectories showed common slopes at different intercepts, reflecting a common ontogenetic pattern of morphological growth fixed early in ontogeny. The anterior width of the snout and the posterior width of the skull table are suitable to discriminate between the two species. The relationship between snout width and snout length is isometric in C. latirostris while it is negatively allometric in C. yacare. These results confirm that the snout shape is a distinctive feature between species established early in ontogeny. The narrowing and lengthening of the snout in C. yacare during ontogeny results in adult forms widely represented in other extant taxa within the genus. The broader and shorter snout in C. latirostris is probably an autapomorphic feature of this species within Caimaninae. © 2015, British Herpetological Society. All rights reserved.

Soibelzon L.H.,Museo de La Plata | Soibelzon L.H.,East Tennessee State University | Zurita A.E.,Northeast National University | Morgan C.C.,Seccion Mastozoologia | And 5 more authors.
Revista Mexicana de Ciencias Geologicas | Year: 2010

We present the first fossil record of Procyon cancrivorus (Cuvier, 1798) for Argentina. Specimen PVE-F 44 (first lower molar) was exhumed from levels assignable to the Late Pleistocene (Lujanian) in the coastal cliffs of the Bermejo river in the vicinity of Villa Escolar, Formosa (26°36'S, 58°40 W). This is also the first South American record of Procyon with accurate stratigraphic provenance, since previous records from Brazil lack stratigraphic context. Procyonids are represented in South America by five living genera (Bassaricyon Allen, Nasuella Hollister, Potos Geoffroy Saint-Hilaire and Cuvier, Procyon Storr and Nasua Storr). Of these, only Procyon and Nasua have paleontological records (Late Pleistocene-Holocene) in Brazil, Uruguay and Bolivia. The results of geometric and traditional morphometric analyses comparing specimen PVE-F 44 with the two known Procyon species (P. cancrivorus and P. lotor) indicates the specimen belongs to the South American species P. cancrivorus. In addition, the associated palaeofauna is composed by intertropical (e.g., Holmesina paulacoutoi) and pampean-patagonian elements (e.g., Megatherium, Toxodon, Glyptodon, Pampatherium typum).

Ercoli M.D.,Museo Argentino de Ciencias Naturales Bernardino Rivadavia | Prevosti F.J.,Museo Argentino de Ciencias Naturales Bernardino Rivadavia | Alvarez A.,Seccion Mastozoologia
Zoological Journal of the Linnean Society | Year: 2012

In this study, we analysed locomotory habits in extant predators and Sparassodonta species through geometric morphometric techniques and discriminant analyses of the distal humerus in anterior view, proximal ulna in lateral view, and tibia in proximal view. We included a wide sample of extant predators, and considered the phylogenetic and allometric structure in the data sets. We also included some Sparassodonta, a group of carnivorous metatherians that inhabited South America during the Cenozoic, and inferred their locomotory habits. Results suggest the presence of a close relationship between shape and locomotory habits, even after removing the shape component explained by phylogeny in the three postcranial elements. Terrestrial habits were inferred for Arctodictis sinclairi, Borhyaena tuberata, 'Lycopsis' longirostrus, and Thylacosmilus atrox. Some degree of cursoriality was highlighted in B. tuberata and T. atrox, and climbing abilities in 'L.' longirostrus, and to a lesser degree in B. tuberata. Scansorial habits were inferred for Cladosictis patagonica, Sipalocyon gracilis, Prothylacynus patagonicus, and Pseudonotictis pusillus, and in the case of C. patagonica, some digging ability was also tentatively inferred. © 2012 The Linnean Society of London.

Verzi D.H.,Seccion Mastozoologia | Alvarez A.,Seccion Mastozoologia | Olivares A.I.,Seccion Mastozoologia | Morgan C.C.,Seccion Mastozoologia | Vassallo A.I.,University of the Sea
Journal of Mammalogy | Year: 2010

Ontogenetic allometries of craniomandibular and dental features linked to digging were analyzed in 5 species of the South American subterranean rodent Ctenomys (tuco-tucos). With the exception of upper incisor procumbency, variables showed high correlation with overall skull size. In particular, craniomandibular variables related to the production of bite forces at the incisors showed near-geometric similarity during postnatal growth and interspecific changes in early developmental stages resulting in different starting forms (lateral transposition). Such an interspecific pattern of change is similar to one previously reported to occur among living and extinct ctenomyid genera. These results suggest more evolutionary flexibility for changes in early ontogenetic stages and allow rejection of the hypothesis that interspecific shape differences in the skull of Ctenomys would be associated with differences in size alone. © 2010 American Society of Mammalogists.

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