Wyniki wyszukiwania

1

Genomic catastrophism and the origin of vertebrate immunity

100%

Hughes A. L.

Archivum Immunologiae et Therapiae Experimentalis

|

1999

|

tom 47

|

nr 6

2

Artykuł dostępny w postaci pełnego tekstu - kliknij by otworzyć plik

New fossil remains from the Pliocene Koetoi Formation of northern Japan provide insights into growth rates and the vertebral evolution of porpoises

80%

Murakami M., Shimada C., Hikida Y., Hirano H.

Acta Palaeontologica Polonica

|

2015

|

tom 60

|

nr 1

Extant porpoises (Phocoenidae) are odontocetes characterized by their small size, short and wide rostrum, late (or absent) completion of epiphyseal ankylosis in the vertebral column (= physical maturity), and short life cycles, all of which are thought to have resulted from progenetic evolution. We describe a small fossil phocoenid from the lower Pliocene Koetoi Formation of Hokkaido (northern Japan), preserving a small, narrow rostrum, as well as anteroposteriorly elongate thoracic and lumbar vertebral centra with completely fused epiphyses. Physical maturity in this specimen occurred significantly earlier than in extant phocoenids, as shown by dental data indicating that the specimen died at only four years of age. The difference between the present material and extant porpoises may be attributable to different growth rates during ontogeny. The long centra and caudally inclined neural spines of the specimen from Hokkaido are primitive characters among phocoenids. By contrast, the great height of its neural spines is highly derived, even among extant species, and suggestive of a fast swimmer. In terms of its vertebral morphology, the new specimen falls within a morphological continuum defined by the archaic Numataphocoena yamashitai and the highly derived vertebral morphology of Phocoenoides dalli. Phocoenid vertebral evolution has been complex and frequently convergent, as opposed to stepwise and unidirectional. The different vertebral morphologies of the new specimen and the contemporaneous extinct taxa Numataphocoena and Piscolithax longirostris indicate that they were adapted to different environments.

3

Palaeoenvironment and palaeoecology of three Cretaceous snakes: Pachyophis, Pachyrhachis, and Dinilysia

80%

Caldwell M. W., Albino A. M.

Acta Palaeontologica Polonica

|

2001

|

tom 46

|

nr 2

The palaeoecology of three Late Cretaceous snakes is evaluated. Pachyophis woodwardi Nopcsa, 1923 and Pachyrhachis problematicus Haas, 1979, are Cenomanian in age and are found in carbonate rocks deposited in marine inter-reef basin environments of the European and African Tethys Sea. Dinilysia patagonica Woodward, 1901, Coniacian in age, is considered closely allied to Living anilioid snakes, and is found in clastic rocks deposited in a terrestrial inter-dune basin environment in northern Patagonia, Argentina. All three snakes are known from well preserved and articulated specimens found in sediments where detailed sedimentological and taphonomic analyses are possible. Pachyophis and Pachyrhachis were laterally compressed, have pachyostotic ribs and vertebrae, and small, narrow heads. These two snakes are interpreted as aquatic predators living in and around the margins of reef mounds on a shallow water carbonate platform. Dinilysia was a large bodied snake with a relatively large head, and is interpreted here as a terrestrial predator that lived in a dry, interdune basin environment dominated by aeolian sedimentation. Sedimentary units preserve ichnological evidence of burrowing insects and rooting plants.

Ograniczanie wyników

2 Acta Palaeontologica Polonica

1 Archivum Immunologiae et Therapiae Experimentalis

1 Albino A. M.

1 Caldwell M. W.

1 Hikida Y.

1 Hirano H.

1 Hughes A. L.

1 Murakami M.

1 Shimada C.

1 2015

1 2001

1 1999

Genomic catastrophism and the origin of vertebrate immunity

New fossil remains from the Pliocene Koetoi Formation of northern Japan provide insights into growth rates and the vertebral evolution of porpoises

Palaeoenvironment and palaeoecology of three Cretaceous snakes: Pachyophis, Pachyrhachis, and Dinilysia