Ontogeny, Intraspecific Variation, and Systematics of the Late Cambrian Trilobite Dikelocephalus
Ontogeny, Intraspecific Variation, and Systematics of the Late Cambrian Trilobite Dikelocephalus

Author: Nigel C. Hughes

Publisher:

Published: 1994

Total Pages: 728

ISBN-13:

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Biometric analyses of well-localized specimens of the trilobite Dikelocephalus from the St. Lawrence Formation (Upper Cambrian), northern Mississippi Valley, suggest that all specimens belong to a single, highly variable morphospecies, D. minnesotensis. A complex pattern of ontogenetically-related and ontogeny-independent variation produced a mosaic of morphotypes, which show greater diversity than previously recorded within trilobite species. There is considerable variation within collections made from single beds. Variations of characters among collections are mosaic, and are clinal in some cases. Patterns of variation within Dikelocephalus cannot be related to lithofacies occurrence. There are no obvious temporal variations in D. minnesotensis within the St. Lawrence Formation, but some Dikelocephalus from the underlying Tunnel City Group may belong to a different taxon. The validity of this early taxon is questionable due to a lack of available material. The mosaic pattern of variation in Dikelocephalus mimics that documented at higher taxonomic levels in primitive libristomate trilobites, and helps explain difficulties in providing a workable taxonomy of primitive trilobites. Results caution proposition of evolutionary scenarios that do not take account of intraspecific variation. The recovery of dorsal shields of Dikelocephalus permits the first detailed reconstruction of the entire exoskeleton. The systematics of the genus is revised and twenty-five species are suppressed as junior synonyms of D. minnesotensis.

Palaeoecology
Palaeoecology

Author: P.J. Brenchley

Publisher: CRC Press

Published: 2023-07-14

Total Pages: 432

ISBN-13: 1000939405

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The first palaeoecology book to focus on evolutionary palaeoecology, in both marine and terrestrial environments. Discusses reconstruction of the past ecological world at population, community and biogeographic levels. A well-illustrated and substantial volume giving accessible coverage of the full range of subjects within palaeoecology. Reviews and summarises all the major mass extinctions.

The Ecology of the Cambrian Radiation
The Ecology of the Cambrian Radiation

Author: Robert Riding

Publisher: Columbia University Press

Published: 2001

Total Pages: 540

ISBN-13: 9780231106139

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The Cambrian radiation was the explosive evolution of marine life that started 550,000,000 years ago. It ranks as one of the most important episodes in Earth history. This key event in the history of life on our planet changed the marine biosphere and its sedimentary environment forever, requiring a complex interplay of wide-ranging biologic and nonbiologic processes. The Ecology of the Cambrian Radiation offers a comprehensive and surprising picture of the Earth at that ancient time. The book contains contributions from thirty-three authors hailing from ten countries and will be of interest to paleontologists, geologists, biologists, and other researchers interested in the global Earth-life system.

Fossils, Phylogeny, and Form
Fossils, Phylogeny, and Form

Author: Jonathan M. Adrain

Publisher: Springer Science & Business Media

Published: 2012-12-06

Total Pages: 420

ISBN-13: 1461505712

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Phylogenetic analysis and morphometrics have been developed by biologists into rigorous analytic tools for testing hypotheses about the relationships between groups of species. This book applies these tools to paleontological data. The fossil record is our one true chronicle of the history of life, preserving a set of macroevolutionary patterns; thus various hypotheses about evolutionary processes can be tested in the fossil record using phylogentic analysis and morphometrics. The first book of its type, Fossils, Phylogeny, and Form will be useful in evolutionary biology, paleontology, systematics, evolutionary development, theoretical biology, biogeography, and zoology. It will also provide a practical, researcher-friendly gateway into computer-based phylogenetics and morphometrics.

Species and Speciation in the Fossil Record
Species and Speciation in the Fossil Record

Author: Warren D. Allmon

Publisher: University of Chicago Press

Published: 2016-10-05

Total Pages: 434

ISBN-13: 022637744X

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The literature of paleobiology is brimming with qualifiers and cautions about using species in the fossil record, or equating such species with those recognized among living organisms. Species and Speciation in the Fossil Record digs through this literature and surveys the recent research on species in paleobiology. In these pages, experts in the field examine what they think species are - in their particular taxon of specialty or more generally in the fossil record. They also reflect on what the answers mean for thinking about species in macroevolution. The first step in this approach is an overview of the Modern Synthesis, and paleobiology’s development of quantitative ways of documenting and analyzing variation with fossil assemblages. Following that, this volume’s central chapters explore the challenges of recognizing and defining species from fossil specimens, and show how with careful interpretation and a clear species concept, fossil species may be sufficiently robust for meaningful paleobiological analyses. Tempo and mode of speciation over time are also explored, exhibiting how the concept of species, if more refined, can reveal enormous amounts about the interplay between species origins and extinction and local and global climate change.