A new specimen of Velocisaurus unicus from Río Negro Province, Argentina

0 comentarios Publicado por Leonardo Filippi en 14:05


Federico Brissón Egli, Federico L. Agnolín, And Fernando Novas

Abelisauroids are the most abundant theropods in the Cretaceous beds of Patagonia. They are traditionally subdivided into large-sized Abelisauridae and smaller Noasauridae. Here, we describe a new specimen of the small enigmatic abelisauroid Velocisaurus unicus Bonaparte, 1991, which was previously known from a single incomplete specimen from Neuquén City, Neuquén Province, Patagonia. The new material comes from the Santonian Bajo de la Carpa Formation (Late Cretaceous) at the Paso Córdoba locality, Río Negro Province. It comprises an almost complete left hind limb and offers novel information about the anatomy of this poorly known abelisauroid. The new material shows that Velocisaurus is remarkable in having a very short, stout, and anteriorly bowed femur, which has a notably subtriangular cross-section at its proximal end. The tibia is long and slender, and the anterior surface of the distal end is anteroposteriorly flat and transversely expanded, with an enlarged surface for the ascending process of the astragalus. The pes has a stout third metatarsal, rod-like metatarsals II and IV, and highly modified phalanges of digit IV. The unique combination of characters of Velocisaurus indicates that this taxon belongs to a still poorly understood radiation of gracile-limbed abelisauroids. The inclusion of Velocisaurus in a comprehensive phylogenetic analysis recovers a monophyletic Noasauridae, but with only very weak support. Detailed analysis of features supporting the inclusion of Velocisaurus within Noasauridae is discussed, and their implications for abelisauroid phylogeny are revisited.
Federico Brissón Egli, Federico L. Agnolín & Fernando Novas 2016. A new specimen of Velocisaurus unicus (Theropoda, Abelisauroidea) from the Paso Córdoba locality (Santonian), Río Negro, Argentina, Journal of Vertebrate Paleontology, DOI: 10.1080/02724634.2016.111915

 

Presentan un nuevo dinosaurio en el MAU: Viavenator exxoni

0 comentarios Publicado por Leonardo Filippi en 20:26


En el día de ayer, se llevó adelante la presentación formal del nuevo dinosaurio del MAU, Museo Municipal Argentino Urquiza, Rincón de los Sauces, Neuquén: Viavenator exxoni, un nuevo género y especie de abelisaurio que aporta información relevante que permite avanzar en el conocimiento de este grupo de terópodos.
Este ejemplar, corresponde al primer dinosaurio carnívoro de la colección del MAU, por lo que todo el equipo del trabajo del museo y los colegas que han participado de su estudio, se encuentran muy satisfechos. Si bien el potencial del área La Invernada, en el cual se viene trabajando desde hace un poco más de tres años, es inmenso, la publicación de este dinosaurio, representa el primero de una serie de otros ejemplares que han sido recuperados allí, entre los que se mencionan, varios dinosaurios titanosaurios, una descena de ejemplares de tortugas y peces.
Los huesos orginales de Viavenator se encontrarán temporalmente exhibidos al público en el laboratorio del Museo hasta fines de Marzo.

 

A new Upper Cretaceous Titanosaur nesting site from La Rioja, Argentina

0 comentarios Publicado por Leonardo Filippi en 13:24


E. Martin Hechenleitner, Lucas E. Fiorelli, Gerald Grellettinner,  Léa Leuzinger, Giorgio Basilici, Jeremías R. A. Taborda, Sergio R. De La Vega And Carlos A. Bustamante

            Cretaceous titanosaur nesting sites are currently known only from Europe, Asia and South America. In the latter, only the Auca Mahuevo and Sanagasta nesting sites have been confidently assigned to this clade of sauropod dinosaurs. Here we report the discovery of the first eggs and egg clutches found at Tama, a new Upper Cretaceous fossiliferous locality in the Los Llanos Formation, Sierra de Los Llanos (La Rioja, NW Argentina). At least five egg clutches, several partially preserved, isolated eggs and many eggshell fragments were discovered in a single outcrop of a sandstone horizon which represents a cumulative palaeosol profile. Although the mechanical and digital preparation of eggs did not reveal any embryonic remains in ovo, the morphology of the eggs and eggshells closely matches that of titanosaur eggs and eggshells found worldwide. The morphology and spatial grouping of the titanosaur eggs from Tama, along with geological observations support a burrow-nesting strategy for these dinosaurs. Although the Sanagasta and Tama eggs were found in the same stratigraphical unit and share several morphological characters, they clearly differ in shell thickness and egg size. This, coupled with the interpretation of different sedimentary contexts for these nesting sites, strongly suggests that at least two different titanosaur species nested in La Rioja during the Late Cretaceous, using different nesting strategies. The occurrence of this new titanosaur nesting site in a semiarid palaeoenvironment represents an interesting case study for the reproductive biology of the titanosaur dinosaurs, particularly their labile nesting behaviour.

Hechenleitner, EM, Fiorelli, LE, Grellettinner, G,  Leuzinger, L, Basilici, G, Taborda, JRA,  De La Vega, SR And Bustamante, CA. 2016. A new Upper Cretaceous Titanosaur nesting site from La Rioja (Nw Argentina), with implications for Titanosaur nesting strategies. Palaeontology, pp. 1–14.

 

Shell bone histology of the long-necked chelid Yaminuechelys (Testudines: Pleurodira) from the late Cretaceous-early Palaeocene of Patagonia

0 comentarios Publicado por Leonardo Filippi en 6:56

 
 

Juan Marcos Jannello, Ignacio A. Cerda, Marcelo S. de la Fuente

            Yaminuechelys is a long-necked chelid turtle whose remains have been recovered from outcrops of the Santonian- Maastrichtian and Danian of SouthAmerica.With the purpose of providing data about shell sculpturing origin and palaeoecology, the bone histology of several shell elements (including neural, costal, peripheral and plastral plates) of Yaminuechelys is described herein. Histological analysis reveals that Yaminuechelys shares with Chelidae the presence of interwoven structural fibre bundles in the external cortex, and parallel-fibred bone of the internal cortex. The presence of resorption lines in several samples indicates that the particular ornamentation of the external surfaces originated, at least in part, by focalized resorption and new bone deposition. This mechanism for ornamentation origin and maintenance is here described for the first time in a turtle. Compactness of the shell bones is consistent with an aquatic habitat, which supports previous hypothesis based on palaeoenvironmental and morphological data.

Janello, JM, Cerda, IA & de la Fuente, MS. 2016. Shell bone histology of the long-necked chelid Yaminuechelys (Testudines: Pleurodira) from the late Cretaceous—early Palaeocene of Patagonia with comments on the histogenesis of bone ornamentation. Sci Nat. 103:26.DOI 10.1007/s00114-016-1346-3.

 

New Peirosaurid from Cerro Lisandro Formation, Neuquén Group, Patagonia Argentina

0 comentarios Publicado por Leonardo Filippi en 6:36


Francisco Barrios, Ariana Paulina-Carabajal y Paula Bona

Peirosaurids are a group of Cretaceous continental crocodyliforms from Gondwana. Two species are known from the Neuquén Group in Argentina: Lomasuchus palpebrosus (Portezuelo Formation, late Turonian–early Coniacian) and Gasparinisuchus peirosauroides (Bajo de la Carpa and Anacleto formations, Santonian and early Campanian, respectively). Here, we describe the first peirosaurid from the Cerro Lisandro Formation, Bayomesasuchus hernandezi gen. et sp. nov. The material corresponds to a fragmentary skull and mandible. Although fragmentary, this is the most complete crocodyliform specimen recorded for the Cerro Lisandro Formation. In a phylogenetic analysis Bayomesasuchus is depicted in a polytomy together with South American peirosaurids and the African form Hamadasuchus rebouli.

Barrios, F. Paulina-Carabajal, A, y Bona Paula. 2016. A new Peirosaurid (Crocodyliformes, Mesoeucrocodylia) from the Upper Cretaceous of Patagonia, Argentina. Ameghiniana 53 (1):14-25.

 

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