Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: life habit

Sortuj według:

Ogranicz wyniki do:

Artykuł dostępny w postaci pełnego tekstu - kliknij by otworzyć plik

Growth and life habits of the Triassic cynodont Trirachodon, inferred from bone histology

100%

Botha J., Chinsamy A.

Acta Palaeontologica Polonica

2004

tom 49

nr 4

Growth pattern and lifestyle habits of the Triassic non−mammalian cynodont Trirachodon are deduced from bone histology and cross−sectional geometry. Several skeletal elements of Trirachodon were examined in order to document histological changes during ontogeny, as well as histovariability in the skeleton. The bone histology of all the elements consists of a moderately vascularized, periodically interrupted, fibro−lamellar bone tissue. This suggests that the overall growth of Trirachodon was probably rapid during the favourable season, but decreased or ceased during the unfavourable season. As the environment is thought to have been semi−arid with seasonal rainfall, it is possible that Trirachodon was sensitive to such environmental fluctuations. Some inter−elemental histovariability was noted where the number and prominence of growth rings varied. Limb bone cross−sectional geometry revealed a relatively thick bone wall and supports earlier proposals that Trirachodon was fossorial.

Enrolment in a Middle Ordovician agnostoid trilobite

80%

Bruton D. L., Nakrem H. A.

Acta Palaeontologica Polonica

2005

tom 50

nr 3

Study of silicified material of Trinodus elspethi, from the Edinburg Formation, Virginia, USA, shows there is no gliding of distal parts of segments but an articulating furrow and opposing flange with prongs, acting as apodemes for muscle attachment, allowed cephalon and thorax to move as a single unit. Articulation between thorax and pygidium was more rigid with prongs from the thorax articulating in sockets on the pygidium. Support is given to the view that agnostoids lived partially enrolled with cephalon and pygidium gaping. They are unique in lacking an articulating half−ring between cephalon and thorax and the hinge joint is modified medially to provide an opening for what is interpreted as an exhalatory organ through which water passed during feeding and swimming. Peculiarities of the thorax are connected with the presence of only two thoracic segments articulating as a unit with distal tips directed anteriorly rather than posteriorly. Otherwise articulating half rings are present in the rest of the thorax and pygidium and lack of articulating facets is not unique. It is concluded that agnostoids can be shown to be trilobites.

Ograniczanie wyników

2 Acta Palaeontologica Polonica

1 Botha J.

1 Bruton D. L.

1 Chinsamy A.

1 Nakrem H. A.

1 2005

1 2004

Wyniki wyszukiwania

Growth and life habits of the Triassic cynodont Trirachodon, inferred from bone histology

Enrolment in a Middle Ordovician agnostoid trilobite