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

100%

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.

Choanocotyle platti sp.nov. from the Northern long-necked turtle, Chelodina rugosa [Pleurodira, Chelidae] in Australia

100%

Tkach V. V., Snyder S. D.

Acta Parasitologica

2007

tom 52

nr 4

Choanocotyle platti sp. nov. (Digenea, Choanocotylidae) is described from the northern long-necked turtle, Chelodina rugosa (Pleurodira, Chelidae) from the Daly and Mary Rivers, Northern Territory, Australia. This is the fifth known member of Choanocotyle. Choanocotyle platti sp. nov. differs from Choanocotyle nematoides Jue Sue et Platt, 1998 and Choanocotyle hobbsi Platt et Tkach, 2003 by smaller body length, larger oral sucker, relatively greater distance between tests, and prepharynx with an infolded posterior region. In addition the new species does not have the looped cirrus sac characteristic of Choanocotyle nematoides. Comparison of sequences of 18S, ITS (ITS1, 5.8S, ITS2) and partial 28S regions of nuclear rDNA among all 3 species strongly supports the status of Choanocotyle platti sp. nov. as a new species.

Ograniczanie wyników

1 Acta Palaeontologica Polonica

1 Acta Parasitologica

1 Sanchez-Villagra M. R.

1 Scheyer T. M.

1 Snyder S. D.

1 Tkach V. V.

2 2007

Wyniki wyszukiwania

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

Choanocotyle platti sp.nov. from the Northern long-necked turtle, Chelodina rugosa [Pleurodira, Chelidae] in Australia