نتایج جستجو برای: conodont
تعداد نتایج: 287 فیلتر نتایج به سال:
Conodonts have been considered the earliest skeletonizing vertebrates and their mineralized feeding apparatus interpreted as having performed a tooth function. However, the absence of jaws in conodonts and the small size of their oropharyngeal musculature limits the force available for fracturing food items, presenting a challenge to this interpretation. We address this issue quantitatively usi...
Conodont elements are the earliest vertebrate dental structures. The dental tools on elements responsible for food fracture-cusps and denticles-are usually composed of lamellar crown tissue (a putative enamel homologue) and the enigmatic tissue known as 'white matter'. White matter is unique to conodonts and has been hypothesized to be a functional adaptation for the use of elements as teeth. W...
Conodonts comprising six species have been recovered from the Aplington Formation from five localities in northccntral Iowa. Although the Aplington conodont fauna is meager -it suggests a correlation with the Maple Mill Shale of southeastern Iowa. The Aplington Formation is vegarded as representing the youngest Devonian formation exposed in northcentral Iowa.
Devonian-Carboniferous boundary is not clear in the Eastern Alborz Mountains. In the current study Tuyeh-Darvar section with about 170 m, thickness is selected. In this investigation, the primary goal is revision of Devonian/Carboniferous Boundary (known as DCB) and the other goal is the redefinition of the DCB as a famous necessity (based on ICS program in 2008 for defining the boundary and to...
Interpretations of conodont anatomy and affinity continue to generate controversy. Fossilized soft-tissue evidence indicates that conodonts possessed eyes, extrinsic eye muscles, a notochord, myomeres, a differentiated tail with fin radials, possible otic capsules and possible branchial structures. Indirect evidence suggests a differentiated brain and cartilaginous head skeleton. The multi-comp...
Please cite this article as: Sun, Yadong, Lai, Xulong, Wignall, Paul B., Widdowson, Mike, Ali, Jason R., Jiang, Haishui, Wang, Wei, Yan, Chunbo, Bond, David P.G., Védrine, Stéphanie, Dating the onset and nature of the Middle Permian Emeishan large igneous province eruptions in SW China using conodont biostratigraphy and its bearing on mantle plume uplift models, LITHOS (2010), doi: 10.1016/j.li...
Almost all aspects of conodont research rely on a sound taxonomy based comparative analysis. This is founded hypotheses homology which ultimately rest knowledge the location elements in apparatus. Natural assemblages—fossils that preserve articulated remains skeletal apparatus—provide our only direct evidence for element location, but very few are known from Late Triassic. Here we describe fuse...
The end-Permian mass extinction is now robustly dated at 252.6 ± 0.2 Ma (U–Pb) and the Permian–Triassic (P–T) GSSP level is dated by interpolation at 252.5 Ma. An isotopic geochronological timescale for the Late Permian–Early Triassic, based on recent accurate high-precision U–Pb single zircon dating of volcanic ashes, together with calibrated conodont zonation schemes, is presented. The durati...
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