نتایج جستجو برای: Conodont

تعداد نتایج: 287  

Journal: :Proceedings. Biological sciences 2013
Duncan J E Murdock Ivan J Sansom Philip C J Donoghue

The morphological disparity of conodont elements rivals the dentition of all other vertebrates, yet relatively little is known about their functional diversity. Nevertheless, conodonts are an invaluable resource for testing the generality of functional principles derived from vertebrate teeth, and for exploring convergence in a range of food-processing structures. In a few derived conodont taxa...

2017
MUHUI ZHANG HAISHUI JIANG MARK A. PURNELL XULONG LAI

Knowledge of the conodont skeleton, in terms of the morphology of the elements and the positions they occupy, provides the foundation for understanding of homology, taxonomy and evolutionary relationships in conodonts. This knowledge also underpins analyses of conodont functional morphology and feeding. Direct evidence of skeletal anatomy and apparatus architecture comes from natural assemblage...

پایان نامه :وزارت علوم، تحقیقات و فناوری - دانشگاه فردوسی مشهد - دانشکده علوم 1376

saluk mount is selected for devonian biostratigraphy. this area located at southwest of bojnurd. in this study three sections are selected and two sections, chahar-borj and tabar sections with a thickness of 650 m, which consist mainly of calcareous sediments was studied in detailed but third section, qelli section, with a thickness of about 450m which consist mainly of sandstone and evaporates...

2009
PETER H. VON BITTER

Accurate hypotheses of primary homology are fundamental to many aspects of the systematics and palaeobiology of fossils. They are particularly critical for conodonts: virtually all areas of conodont research are underpinned by homology, yet the majority of conodont taxa are found only as disarticulated skeletal elements, and hypotheses of element homology are inferred from morphological compari...

2000
Philip C. J. Donoghue Mark A. Purnell

—Conodont element function and feeding mechanisms are of considerable paleobiological importance, yet many details remain poorly understood and speculative. Analysis based on morphology, physical juxtaposition, and patterns of surface damage and microwear on pairs of Pa elements from individuals of Idiognathodus indicates that these elements crushed food by rotational closure, which brought the...

Journal: :Trends in ecology & evolution 1996
R J Aldridge M A Purnell

The discovery of fossilized conodont soft tissues has led to suggestions that these enigmatic animals were among the earliest vertebrates and that they were macrophagous, using their oropharyngeal skeletal apparatus to capture and process prey. These conclusions have proved controversial. There is now a consensus that conodonts belong within the chordates, but their position within the clade is...

2002
Shunxin Zhang Christopher R. Barnes

Anticosti Island, Que¤bec, has perhaps the most fossiliferous and complete Llandovery (Early Silurian) sequence in the world. The undeformed limestones are well exposed and yield extremely well preserved conodonts whose taxonomy and biostratigraphy has been studied in detail. In addition to documenting the general temporal and spatial distribution of Llandovery conodonts, a set of 107 conodont ...

Journal: :Science 2013
Yadong Sun Michael M Joachimski Paul B Wignall Chunbo Yan Yanlong Chen Haishui Jiang Lina Wang Xulong Lai

Goudemand et al. replot a subset of our well-constrained data using a new Early Triassic biostratigraphic scheme based on a lower-resolution ammonoid zonation scheme and hypothetical ammonoid-conodont correlation to produce a less distinct seawater temperature history. We dispute their unsubstantiated correlation and, consequently, their allegations.

Journal: :Proceedings. Biological sciences 2001
P C Donoghue

Recognition that conodonts were the earliest vertebrate group to experiment with skeletal biomineralization provides a window in which to study the origin and early evolution of this developmental system. It has been contended that the conodont skeleton comprised a classic suite of vertebrate hard tissues, while others suggest that conodont hard tissues represent divergent specializations withi...

2005
MARK A. PURNELL

The different types of elements that occurred together in conodont apparatuses are not recovered from the fossil record in the expected numbers. The causes of this are complex and difficult to study. Numerous complete articulated skeletons of Ozarkodina excavata (Branson and Mehl) have been recovered from the Eramosa Member at Hepworth, Ontario, and as a consequence, several of the potential bi...

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