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Bryozoan astogeny and evolutionary novelties: their role in the origin and systematics of the Ordovician monticuliporid trepostome genus Peronopora
- David R. Hickey
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- Journal:
- Journal of Paleontology / Volume 62 / Issue 2 / March 1988
- Published online by Cambridge University Press:
- 19 May 2016, pp. 180-203
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Modifications of primitive astogenetic patterns were central to the origin of bifoliate Peronopora. Outgroup comparison with Prasopora indicates that fundamental events in the former's origin included vertical growth of basal lamina skeleton to form the median lamina and heterochronic modifications of early and later-stage astogeny. Heterochronic modifications of early astogeny included acceleration of budding rates in the ancestrular disc, disc enlargement, and reduction of the basal expansion. Later-stage heterochronic modifications included reduction of zooecial length and width of “endozonal” growth and parallel orientation of cystiphragms about maculae. Also important were “2-D” budding in longitudinal ranges and a unique mode of secondary frond formation. Paedomorphosis resulted in constraints on zoarial form, autozooecial morphology, cystiphragm patterning, and increased colonial integration. Coordination of early and later-stage astogenetic events suggests developmental integration linked to median lamina formation. Heterochronic modifications are inferred to have been products of spatial competition in early astogeny and competitive avoidance and resource exploitation in later astogeny. Restricted biogeographic distribution and characteristics of the ancestrula suggest that the larvae of bifoliate Peronopora were nonplanktotrophic.
A shared derived suite of characters including the median lamina unite the bifoliate Peronopora clade. Results of cladistic analyses indicate that bifoliate Peronopora comprise a cohesive, statistically significant clade. Character analysis, phylogenetic results, and the restricted biogeographic distribution of bifoliate species support the hypothesis of a monophyletic bifoliate Peronopora clade of generic rank. The generic concept of Peronopora is revised and limited to bifoliate species.
Shell shape plasticity in Late Pennsylvanian myalinids (Bivalvia)
- David R. Hickey
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- Journal:
- Journal of Paleontology / Volume 61 / Issue 2 / March 1987
- Published online by Cambridge University Press:
- 14 July 2015, pp. 290-311
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Analyses of shell shape variation in epifaunal and semi-infaunal myalinids from the LaSalle “cyclothem” attest to the extensive shape plasticity of some Late Pennsylvanian myalinids. Mean shell shapes differ significantly within and among species across three nearshore facies. Discriminant analyses of Fourier biometric data categorized by taxonomic, populational (habitat), life-mode, and “multi-species habitat assemblage”” discriminant groups reveal patterns of shape change and variation across an inferred environmental stress gradient in addition to taxonomic and life-mode shape differences. Fourier harmonic data are good indicators of shape differences between epifaunal and semi-infaunal life modes. Mean shapes of epifaunal species vary among habitats. Within-habitat shell shape convergence occurred between Myalina glossoidea and M. (Orthomyalina) slocomi. Interpopulational shape divergence occurred among all populations of M. (Orthomyalina) slocomi, M. glossoidea, and M. wyomingensis. Within-species variation among habitats produced significant mean shape differences among each of three “multi-species habitat assemblages.” Results indicate that a portion of the variation is of ecophenotypic origin.
Mean interspecific shape differences reflect internal functional organization and life modes. Intraspecific shape differences among epifaunal species could reflect physical and biotic habitat variables. Several harmonic amplitudes vary in concert with inferred environmental variation among habitats. Although biologic interpretation of harmonic data is problematic, parallel trends in fifth harmonic amplitudes of epifaunal species mirror inferred differences in water turbulence among habitats and could reflect shape variation related to byssal attachment.
Stress gradient trends in intraspecific shape variability cannot be collectively explained by either of the antithetical stability-diversity-variation hypotheses. Each species exhibits a different nonmonotonic trend. Maximal levels of intraspecific variation within each species occurred within different habitats. Within-species differences in levels of variation could result from genetic variation among populations as well as ecophenotypic influences. Comparative studies of ontogenetic shape change between valves of individuals, among individuals, and among populations are necessary to determine the relative influence of environmental variables on shape variation and evolutionary significance of phenotypic plasticity.
Contributors
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- By Linda S. Aglio, Cyrus Ahmadi Yazdi, Syed Irfan Qasim Ali, Caryn Barnet, Jessica Bauerle, Felicity Billings, Evan Blaney, Beverly Chang, Christopher Chen, Zinaida Chepurny, Hyung Sun Choi, Allison Clark, Lauren J. Cornella, Lisa Crossley, Michael D’Ambra, Galina Davidyuk, Whitney de Luna, Manisha S. Desai, Sukumar P. Desai, Kelly G. Elterman, Michaela K. Farber, Iuliu Fat, Jaida Fitzgerald, Devon Flaherty, John A. Fox, Gyorgy Frendl, Rejean Gareau, Joseph M. Garfield, Andrea Girnius, Laverne D. Gugino, J. Tasker Gundy, Carly C. Guthrie, Lisa M. Hammond, M. Tariq Hanifi, James Hardy, Philip M. Hartigan, Thomas Hickey, Richard Hsu, Mohab Ibrahim, David Janfaza, Yuka Kiyota, Suzanne Klainer, Benjamin Kloesel, Hanjo Ko, Bhavani Kodali, Vesela Kovacheva, J. Matthew Kynes, Robert W. Lekowski, Joyce Lo, Jeffrey Lu, Alvaro A. Macias, Zahra M. Malik, Erich N. Marks, Brendan McGinn, Jonathan R. Meserve, Annette Mizuguchi, Srdjan S. Nedeljkovic, Ju-Mei Ng, Michael Nguyen, Olutoyin Okanlawon, Jennifer Oliver, Krishna Parekh, Jessica Patterson, Christian Peccora, Pete Pelletier, Sujatha Pentakota, James H. Philip, Marc Philip T. Pimentel, Timothy D. Quinn, Elizabeth M. Rickerson, Susan L. Sager, Julia Serber, Shaheen Shaikh, Stanton Shernan, David Silver, Alissa Sodickson, Pingping Song, George P. Topulos, Agnieszka Trzcinka, Richard D. Urman, Rosemary Uzomba, Joshua Vacanti, Assia Valovska, Michael Vaninetti, Scott W. Vaughan, Kamen Vlassakov, Christopher Voscopoulos, Emily L. Wang, Laura Westfall, Zhiling Xiong, Stephanie Yacoubian, Dongdong Yao, Martin Zammert, Maksim Zayaruzny, Jose Luis Zeballos, Natthasorn Zinboonyahgoon, Jie Zhou
- Edited by Linda S. Aglio, Robert W. Lekowski, Richard D. Urman
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- Book:
- Essential Clinical Anesthesia Review
- Published online:
- 05 February 2015
- Print publication:
- 08 January 2015, pp xi-xvi
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