Macroevolutionary patterns of Triassic Ammonoid morphology
- 页数：371 p. :
- 第一责任说明：Alistair John McGowan.
- 分类号：a555.81
MARC全文
62h0020742 20140522143903.0 cr un||||||||| 101009s2003 xx ||||f|||d||||||||eng | CNY371.35 (UnM)AAI3097138 UnM UnM NGL a555.81 McGowan, Alistair John. Macroevolutionary patterns of Triassic Ammonoid morphology [electronic resource] : drelationships among disparity, morphotypes, and spatiotemporal evolutionary patterns / Alistair John McGowan. 371 p. : digital, PDF file. Adviser: David Jablonski. ; Source: Dissertation Abstracts International, Volume: 64-07, Section: B, page: 3159. Thesis (Ph.D. ) -- The University of Chicago, 2003. Ammonoids have been a major target for morphospace studies. However, the Triassic ammonoid morphological evolution has not been quantitatively studied in depth. The Triassic is a key bridging interval between the Paleozoic and Jurassic-Cretaceous ammonoids. Within the Triassic, ammonoids undergo smaller crises taxonomic diversity crises, allowing the study of the effects of repeated turnovers on morphological evolution.;After the Permo-Triassic mass extinction Xenodiscus became the Triassic ammonoid “rootstock”. To analyze the influence of this “bottleneck”, morphological comparisons among the Carboniferous, Triassic and Early Jurassic ammonoids were made. Within the Triassic ammonoid disparity was compared to Gould's (1989) models. Patterns of changes in disparity and taxonomic richness of Triassic ammonoids were also compared with Foote's (1992) models.;Strong similarities existed between W-D geometries of the Mid-Upper Carboniferous and Triassic ammonoids, while S-D geometries among the Triassic ammonoids were more similar to those of Early Jurassic ammonoids. Triassic ammonoids have similar correlations among morphological characters to the Mid-Upper Carboniferous ammonoids, but the correlations are weaker, suggesting that during the Triassic character combinations were less constained.;With respect to Gould's (1989) models, Triassic ammonoids best fit a model of rapid expansion to a relatively constant level of disparity. The overall pattern of Triassic morphological evolution is diffusive, interrupted by turnovers that vary between being selective and non-selective with respect to morphology. No one pattern in changes in taxonomic richness and disparity dominates.;The spatial deployment of Triassic ammonoids among paleobiogeographic provinces was studied to test whether taxonomically less rich provinces were also morphologically impoverished, and whether certain morphologies were predisposed to either cosmopolitan or endemic distributions. Differences in disparity among the provinces were mostly explicable by differences in taxonomic richness alone, and no linkage between morphology and spatial deployment was found.;Jablonski (1995) proposed that position in morphospace might influence taxon longevity. Little evidence was found that genus duration had any correlation with distance from the centroid, although boundary-crossing genera plotted, on average, further from the centroid. Taxa descended from these boundary-crossing genera tended to plot closer to the centroid, suggesting that new taxa preferentially originated closer to the center of morphospace. Paleontology ; Ammonoidea. ; Morphology (Animals) Triassic. aJablonski, David. aCN bNGL http://pqdt.bjzhongke.com.cn/Detail.aspx?pid=DwuoSEIf44o%3d NGL Bs645 rCNY371.35 ; h1 xhbs1003