New species of Meiolaniform turtle from Patagonia

0 comentarios Publicado por Leonardo Filippi en 14:46


Juliana Sterli, Marcelo S. De la Fuente e Ignacio A. Cerda
 
 
Una nueva especie de meiolaniforme, Trapalcochelys sulcata gen. nov. sp. nov., de la Formación Allen (Campaniano tardío–Maastrichtiano temprano), Patagonia, Argentina, es presentada en este trabajo. Los restos postcraneanos pertenecientes a esta nueva especie son descriptos macroscópicamente (e.g., morfología externa) y microscópicamente (e.g., cortes histológicos del caparazón). Trapalcochelys sulcata gen. nov. sp. nov. comparte con otros meiolaniformes la presencia de surcos entre los escudos marginales marcadamente curvados anteriormente y la ornamentación de las placas dérmicas del caparazón constituida por pequeños forámenes. Esta nueva especie difiere de la otra especie de meiolaniforme del Cretácico Superior de Patagonia —Patagoniaemys gasparinae— en el tamaño general y en la forma de la neural 1. La histología ósea está caracterizada por una estructura diploe, donde una capa externa e interna de tejido compacto circundan una región de hueso esponjoso. El hueso compacto está compuesto mayormente por paquetes entrelazados de fibras estructurales. La abundancia de fibras estructurales en la corteza interna y la presencia de grandes canales vasculares tubulares son los caracteres histológicos mas distintivos de T. sulcata. Además, una revisión exhaustiva de los restos de Meiolaniformes del Cretácico Superior de Sudamérica es presentada. El registro sudamericano conocido de Meiolaniformes del Cretácico Superior está restringido a Argentina y en esta revisión hasta seis localidades han sido reconocidas. Se corrobora que los Meiolaniformes son un componente de la asociación sudamericana Alleniana de tetrápodos de edad campaniana tardía–maastrichtiana temprana.
 
 
Sterli, J., De la Fuente, M. S. y Cerda, I. A. 2013. New species of Meiolaniform turtle and a revision of the Late Cretaceous Meiolaniformes of South America. Ameghiniana 50 (2): 240-256.

 


 

The dentition of Manidens condorensis (Ornithischia; Heterodontosauridae) from the Jurassic Cañadón Asfalto Formation of Patagonia

0 comentarios Publicado por Leonardo Filippi en 14:26


 
 
Marcos G. Becerraa, Diego Pol, Claudia A. Marsicano and Oliver W.M. Rauhut

The recently described Manidens condorensis is one of the most completely known taxa of the family Heterodontosauridae from the southern landmasses. However, some dental aspects are not well known due to preservational problems in the type material. This contribution reports new isolated teeth found in the Canñadón Asfalto Formation (Early-Middle Jurassic). These teeth are referred to Manidens condorensis based on the presence of autapomorphic characters of the unusual dentition of this taxon, such as the highly asymmetric tooth crowns and small crenulations on each denticles. The isolated crowns are well preserved and reveal the presence of undescribed and new autapomorphical features, including apical and basal wear facets on the occlusal surface of isolated crowns and a wear surface also in the caniniform tooth. We carried out statistical analyses (including morphogeometrical and discriminant analyses), using the holotype crowns as a morphological starting point, for characterising shape variation of the crowns along the toothrow and for identifying the position of isolated crowns. These analyses allow defining morphological regions within the postcaniniform toothrow and produce a metrically based discriminant function to predict the hypothetical position of future discoveries, providing a methodological framework that could be applied to other extinct heterodont dinosaurs.

 
Marcos G. Becerra , Diego Pol , Claudia A. Marsicano & Oliver W.M. Rauhut (2013). The dentition of Manidens condorensis (Ornithischia; Heterodontosauridae) from the Jurassic Cañadón Asfalto Formation of Patagonia: morphology, heterodonty and the use of statistical methods for identifying isolated teeth, Historical Biology: An International Journal of Paleobiology, DOI:10.1080/08912963.2013.794227

 

The titanosaur sauropods from the Allen Formation of Salitral Moreno, Río Negro, Argentina

0 comentarios Publicado por Leonardo Filippi en 14:19


 
Rodolfo García y Leonardo Salgado

The dinosaur record of the Salitral Moreno locality (Río Negro Province, Argentina) is characterized by a high diversity of herbivore taxa, among them hadrosaurs, ankylosaurs, and titanosaur sauropods, but carnivores are rare, consisting of only a few fragmentary bones of small forms. Titanosaurs are represented by Rocasaurus muniozi and Aeolosaurus sp., and at least four other taxa, represented by fragmentary material. The elements preserved include a cervical, dorsal and caudal vertebrae, chevron, humerii, ulnae, radii, metacarpal, femora, tibiae, metatarsal, ischia, pubis, and ilium. The Allen Formation is thought to be correlated with the Marília Formation in Brazil, and their faunas have certain elements in common such as aeolosaurines, but saltasaurines and hadrosaurs, are known exclusively from the Allen Formation. These absences, and particularly that of the saltasaurines, may be because those sauropods originated late in the Cretaceous, probably in southern South America (Northern Patagonia?), and they did not have time to disperse to northern South America.

 
Garcia, R.A. and Salgado, L. 2013. The titanosaur sauropods from the late Campanian–early Maastrichtian Allen Formation of Salitral Moreno, Río Negro, Argentina. Acta Palaeontologica Polonica 58 (2): 269–284.
 
 

 

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