Wyniki wyszukiwania - Biblioteka Nauki

Nowa wersja platformy, zawierająca wyłącznie zasoby pełnotekstowe, jest już dostępna.
Przejdź na https://bibliotekanauki.pl

Ograniczanie wyników

4 Acta Palaeontologica Polonica

Znaleziono wyników: 4

Liczba wyników na stronie

Wyniki wyszukiwania

Sortuj według:

Ogranicz wyniki do:

Gastroliths in an ornithopod dinosaur

100%

Cerda I. A.

Acta Palaeontologica Polonica

2008

tom 53

nr 2

Gastroliths (stomach stones) are known from many extant and extinct vertebrates, including dinosaurs. Reported here is the first unambiguous record of gastroliths in an ornithopod dinosaur. Clusters of small stones found in the abdominal region of three articulated skeletons of Gasparinisaura cincosaltensis were identified as gastroliths on the basis of taphonomic and sedimentologic evidence. The large number of stones found in each individual, their size, and the fact that Gasparinisaura cincosaltensis was herbivorous, all suggest that they were ingested as a result of lithophagy rather than accidental swallowing.

Dermal armor histology of Saltasaurus loricatus, an Upper Cretaceous sauropod dinosaur from Northwest Argentina

63%

Cerda I. A. , Powell J. E.

Acta Palaeontologica Polonica

2010

tom 55

nr 3

389-398

The first unambiguous evidence of the presence of osteoderms in sauropod dinosaurs came from the discovery of Saltasaurus loricatus, a titanosaur from the Upper Cretaceous of Argentina. The dermal armor of Saltasaurus is composed of bony plates and small dermal ossicles. Here, we analyze the bone microstructure of these elements and provide information regarding its origin and development. The bony plates are composed almost entirely of reconstructed cancellous bone. Remains of primary bone consist of coarse bundles of mineralized collagenous fibers towards the external surface. Also, woven fibered bone tissue appears in the basal and lateral regions. Dermal ossicles lack secondary remodeling, and their matrix is formed by three orthogonal systems of collagenous fiber bundles. Growth lines are present in both bony plates and ossicles. Bone histology reveals that osteoderms mainly originated through direct mineralization (metaplasia) of the dermis, although other mechanisms are also involved (at least in the origin of dermal plates). The common features of development and integumental location of the osteoderms of Saltasaurus and other non−related vertebrates (e.g., lepidosaurs, crocodylomorphs) are linked to the intrinsic skeletogenic properties of the dermis.

Growth dynamics and body size evolution of South American long-necked chelid turtles: A bone histology approach

38%

Pereyra M. E. , Bona P. , Cerda I. A. , Jannello J. M. , De La Fuente M. S. , Desantolo B.

Acta Palaeontologica Polonica

2020

tom 65

nr 3

Distinguishing Quaternary glyptodontine cingulates in South America: How informative are juvenile specimens?

38%

Luna C. A. , Cerda I. A. , Zurita A. E. , Gonzalez R. , Prieto M. C. , Mothe D. , Avila L. S.

Acta Palaeontologica Polonica

2018

tom 63

nr 1

The subfamily Glyptodontinae (Xenarthra, Cingulata) comprises one of the most frequently recorded glyptodontids in South America. Recently, the North American genus Glyptotherium was recorded in South America, in addition to the genus Glyptodon. It has been shown that both genera shared the same geographic distribution in central-north and eastern areas of South America (Venezuela and Brazil, respectively). Although some characters allow differentiation between adult specimens of both genera, the morphological distinction between these two genera is rather difficult in juvenile specimens. In this contribution, a detailed morphological, morphometric and histological survey of a juvenile specimen of Glyptodontinae recovered from the Late Pleistocene of northern Brazil is performed. The relative lower osteoderms thickness, the particular morphology of the annular and radial sulci and the distal osseous projections of the caudal osteoderms suggest that the specimen belongs to the genus Glyptotherium. In addition, the validity of some statistical tools to distinguish between different ontogenetic stages and in some cases between genera is verified. The osteoderm microstructure of this juvenile individual is characterized by being composed of a cancellous internal core surrounded by a compact bone cortex. Primary bone tissue mostly consists of highly vascularized, woven-fibered bone tissue. Unlike that observed in adult Glyptodontinae, both the Sharpey fibers and the fibrous and laminar parallel bone tissue as secondary bone are absent. This study enhances our knowledge about those morphological and histological changes that occur through the ontogeny in glyptodonts.