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Variation of the outer circumferential layer in the limb bones of birds

100%

Ponton F., Elzanowski A., Castanet J., Chinsamy A., de Margerie E., de Ricqles A., Cubo J.

Acta Ornithologica

2004

tom 39

nr 2

The core of the limb bone cortex of mammals and birds is made of rapidly deposited, fibro-lamellar bone tissue (also present in non-avian theropods), which is usually surrounded by an avascular outer circumferential layer (OCL) of slowly deposited parallel-fibered bone. We present the first comparative allometric study of the relative OCL thickness (expressed as a fraction of the diaphyseal radius) in modern birds. Body size explains 79% of the OCL variation in thickness, which is inversely correlated with size, that is, shows negative allometry (slope -0.799). This may explain the apparent absence of OCL in the ratites. Since the OCL is deposited at the end of growth, we propose that its relative thickness probably correlates with the amount of slow, residual growth, which our results suggest to be on the average larger in small birds.

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Osteohistology of hyperodapedontine rhynchosaurs from the Upper Triassic of Southern Brazil

100%

Veiga F. H., Soares M. B., Sayao J. M.

Acta Palaeontologica Polonica

2015

tom 60

nr 4

The first osteohistological study focused exclusively on rhynchosaurs (non-archosauriform archosauromorphs), based on the hyperodapedontines Teyumbaita sulcognathus and Hyperodapedon sp., from the Upper Triassic of Southern Brazil, indicates a relatively rapid growth rate in early ontogeny shown by the fibrolamellar complex, with a change to slow intermittent growth during late ontogeny represented by parallel-fibred bone with several growth marks. Contrary to previous studies, which described a typical non-archosaur reptilian bone tissue pattern for rhynchosaurs, with growth marks extending across the entire cortex, we demonstrate that, in both studied taxa, the initial growth rate was faster in comparison to the later. This suggests that the ability of rapid growth at high rates was already present in basal non-ar-chosauriform archosauromorphs.

Carapace bone histology in the giant pleurodiran turtle Stupendemys geographicus: phylogeny and function

80%

Scheyer T. M., Sanchez-Villagra M. R.

Acta Palaeontologica Polonica

2007

tom 52

nr 1

Stupendemys geographicus (Pleurodira: Pelomedusoides: Podocnemidae) is a giant turtle from the Miocene of Venezuela and Brazil. The bone histology of the carapace of two adult specimens from the Urumaco Formation is described herein, one of which is the largest of this species ever found. In order to determine phylogenetic versus scaling factors influencing bone histology, S. geographicus is compared with related podocnemid Podocnemis erythrocephala, and with fossil and Recent pelomedusoides taxa Bothremys barberi, Taphrosphys sulcatus, “Foxemys cf. F. mechinorum”, and Pelomedusa subrufa. Potential scaling effects on bone histology were further investigated by comparison to the Pleistocene giant tortoise Hesperotestudo (Caudochelys) crassiscutata and the Late Cretaceous marine protostegid turtle Archelon ischyros. A diploe structure of the shell with well developed external and internal cortices framing interior cancellous bone is plesiomorphic for all sampled taxa. Similarly, the occurrence of growth marks in the shell elements is interpreted as plesiomorphic, with the sampled neural elements providing the most extensive record of growth marks. The assignment of S. geographicus to the Podocnemidae was neither strengthened nor refuted by the bone histology. A reduced thickness of the internal cortex of the shell elements constitutes a potential synapomorphy of the Bothremydidae. S. geographicus and H. crassiscutata both express extensive weight−reduction through lightweightconstruction while retaining form stability of the shell. The bone histology of A. ischyros presents features likely related to an open marine lifestyle.

Ograniczanie wyników

2 Acta Palaeontologica Polonica

1 Acta Ornithologica

1 Castanet J.

1 Chinsamy A.

1 Cubo J.

1 Elzanowski A.

1 Ponton F.

1 Sanchez-Villagra M. R.

1 Sayao J. M.

1 Scheyer T. M.

1 Soares M. B.

1 Veiga F. H.

1 de Margerie E.

1 de Ricqles A.

1 2015

1 2007

1 2004

Wyniki wyszukiwania

Variation of the outer circumferential layer in the limb bones of birds

Osteohistology of hyperodapedontine rhynchosaurs from the Upper Triassic of Southern Brazil

Carapace bone histology in the giant pleurodiran turtle Stupendemys geographicus: phylogeny and function