Seccion Mastozoologia

La Plata, Argentina

Seccion Mastozoologia

La Plata, Argentina
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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.

Alvarez A.,Seccion Mastozoologia | Verzi D.H.,Seccion Mastozoologia
Biological Journal of the Linnean Society | Year: 2011

We analyzed mandible shape variation of 17 genera belonging to three superfamilies (Cavioidea, Chinchilloidea, and Octodontoidea) of South American caviomorph rodents using geometric morphometrics. The relative influence of phylogeny and ecology on this variation was assessed using phylogenetic comparative methods. Most morphological variation was concentrated in condylar, coronoid, and angular processes, as well as the diastema. Features potentially advantageous for digging (i.e. high coronoid and condylar processes, relatively short angular process, and diastema) were present only in octodontoids; cavioids showed opposing trends, which could represent a structural constraint for fossorial habits. Chinchilloids showed intermediate features. Genera were distributed in the morphospace according to their classification into superfamilial clades. The phylogenetic signal for shape components was significant along phylogeny, whereas the relationship between mandibular shape and ecology was nonsignificant when phylogenetic structure was taken into account. An early evolutionary divergence in the mandible shape among major caviomorph clades would explain the observed strong phylogenetic influence on the variation of this structure. © 2011 The Linnean Society of London.

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.

Camacho M.A.,Seccion Mastozoologia | Chavez D.,University of California at Los Angeles | Burneo S.F.,Seccion Mastozoologia
Zootaxa | Year: 2016

The Yasuni Round-eared bat, Lophostoma yasuni, was described in 2004 by morphological analysis of the holotype, the only specimen attributed to this taxon to date. A molecular analysis using cytochrome-b sequences and a new morphological analysis that includes the holotype of L. yasuni and two specimens of L. carrikeri from near the type locality of L. yasuni were carried out. The new molecular and morphological evidence places L. yasuni within the clade of L. carrikeri. We propose that L. yasuni should therefore be considered as a synonym of L. carrikeri. An emended diagnosis for L. carrikeri extending ranges of craniodental measurements for this species is presented. © 2016 Magnolia Press.

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.

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).

Verzi D.H.,Seccion Mastozoologia | Verzi D.H.,CONICET | Olivares A.I.,Seccion Mastozoologia | Olivares A.I.,CONICET | Morgan C.C.,Seccion Mastozoologia
Mammalian Biology | Year: 2010

A new species of Ctenomyidae from the late Pliocene of Uquía Formation (northwestern Argentina) is described. The new remains consist of a fragmentary rostrum, and a left mandible with partial lower dentition. Its phylogenetic affinity and morphological specializations for tooth-digging support its assignation to the South American rodent genus Ctenomys. In this context, we highlight the importance of unique morphological specializations for the delimitation of genera within an intrafamilial clade in which similar adaptive strategies could have evolved more than once. The new materials are the oldest fossils for the genus (ca. 3.5 Ma), and their finding in the central Andes agrees with previous hypotheses about the possible area of origin of Ctenomys. They precede by about one million years the presence of Ctenomys chapalmalensis in the Pliocene of the Pampean region of central Argentina, the oldest record previously known for the genus. Nevertheless, the new species does not contribute key information about ancestral character states for the genus beyond those already known through C. chapalmalensis. The phylogenetic, adaptive and even chronological information supplied by these new materials would be linked to the differentiation of the genus rather than to its origin. © 2009 Deutsche Gesellschaft für Säugetierkunde.

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.

PubMed | Seccion Mastozoologia
Type: Journal Article | Journal: Journal of anatomy | Year: 2011

Among the ecomorphologically diverse Octodontoidea rodents, fossorial habits are prevalent in Ctenomyidae and Octodontidae and occur in some members of Echimyidae. To detect traits linked to scratch-digging, we analyzed morpho-structural variation in the carpus and metacarpus of 27 species of extinct and living octodontoids with epigean, fossorial and subterranean habits. Within a context of relative morphological uniformity, we detected the following specialized traits in the burrowing Clyomys (Echimyidae), Spalacopus (Octodontidae), Ctenomys and Eucelophorus (Ctenomyidae): broad shortened carpus, robust metacarpals, markedly broad and short metacarpal V, and predominance of ray III (mesaxony, incipient in Spalacopus). In addition, the specialized subterranean Ctenomys presented an enlarged scapholunar in extensive contact with the unciform, and with a complex-shaped proximal articular surface. These features are interpreted as responses to mechanical requirements of scratch-digging, providing greater carpal rigidity and resistance to direct forces exerted during the digging stroke. In Ctenomys, the radius-scapholunar joint restricts movement at wrist level. The phylogenetic distribution of traits shows that the most derived carpal and metacarpal morphologies occur among subterranean octodontoids, also possessing important craniodental adaptations, and supports the hypothesis that the acquisition of digging specializations would have been linked to increasing burrowing frequency in some lineages. Nevertheless, octodontoids with less morphological specializations have metacarpal modifications advantageous for digging, suggesting that scratch-digging specialization preceded the acquisition of tooth-digging traits, in agreement with the general claim that scratch-digging is the primary digging strategy in burrowing mammals.

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