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Über dieses Buch

Increasing rate of species extinction in the present day will lead to a huge biodiversity crisis; eventually, this will lead to the paucity of non-renewable resources of energy making our Earth unsustainable in future. To save our mother planet from this crisis, studies need to be performed to discover abundant new fossil sites on Earth for continued access to oil-rich locations. Most importantly, a holistic approach is necessary in solving the present problem of biodiversity loss. This book presents newly developed quantitative models in understanding the biodiversity, evolution and ecology of extinct organisms. This will assist future earth scientists in understanding the natural and anthropogenic causes behind biodiversity crisis and ecosystem collapse. In addition, this study would be of great interest to exploration geologists and geophysicists in potentially unraveling natural resources from our sustainable Earth.

Inhaltsverzeichnis

Frontmatter

Chapter 1. A Geometric Morphometric Approach in Assessing Paleontological Problems in Atrypid Taxonomy, Phylogeny, Evolution and Ecology

Rituparna Bose

Chapter2. Testing the Taxonomy and Phylogeny of Eastern North American Atrypid Brachiopods: A Geometric Morphometric Approach

The phylogeny and taxonomy of atrypides as proposed in the past has not been tested in terms of morphometric shape. Here, we investigated external shell shape variation in brachiopod morphology at the subfamily and generic level using geometric morphometrics. We measured valve shape in 1593 atrypid individuals from Silurian-Devonian time intervals from 8 EE subunits from 18 geographic localities in eastern North America. The following representatives of the Atrypida were included in the morphometric analyses: Atrypa, Gotatrypa, Kyrtatrypa, Oglupes?, Joviatrypa, Endrea, Dihelictera (Atrypinae); Pseudoatrypa (Variatrypinae) and Spinatrypa (Spinatrypinae).We used 8 external landmarks to determine shape differences among genera and subfamilies in time and space and to calculate pairwise distances between them. Phylogenetic divergence time was determined between atrypid generic pairs based on the phylogenetic tree published in prior literature. Maximum-likelihood was used to assess evolutionary rate and mode of morphological divergence. Results indicate that morphological divergences among these genera are very small compared to their within-genus variation. Thus, while morphometric differentiation is concordant with phylogeny proposed in the past, the small shell shape distances between genera, considerable morphological overlap between subfamilies, considerable variation within one subfamily, and greater morphological variation within genus, suggest that other characteristics such as ribbing, growth lamellae, pedicle opening, etc. prove to be more useful for distinguishing genera in atrypid brachiopods. Thus, a combination of quantified shape, external and internal morphological characters is essential for future phylogenetic classification in order to understand the evolutionary ecology of these complex organisms in its entirety.
Rituparna Bose

Chapter 3. Morphological Evolution in an Atrypid Brachiopod Lineage from the Middle Devonian Traverse Group of Michigan, USA: A Geometric Morphometric Approach

Geometric morphometrics were used to assess evolutionary mode and correlation with environmental factors in the shell morphology of an atrypid brachiopod species lineage. Seven landmark measurements were taken on the dorsal valve, ventral valve, anterior and posterior regions of over 1,100 specimens of Pseudoatrypa cf. lineata taxon from the Middle Devonian Traverse Group of Michigan State to quantify shell shape. Specimens were partitioned by their occurrence in four stratigraphic horizons (Bell Shale, Ferron Point, Genshaw and Norway Point) from the Traverse Group of northeastern Michigan outcrop. Geometric morphometric and multivariate statistical analyses were performed to test patterns and processes of morphological shape change of species over 5 m.y. interval of time. Maximum-likelihood method was used to determine the evolutionary rate and mode in morphological divergence in this species over time. Three hypotheses were tested regarding patterns of evolutionary change: (1) if the species conforms to a punctuated equilibrium model, there should be no significant differences between successive stratigraphic samples; (2) if the species evolved in a gradual, directional manner, then samples from successive stratigraphic units should be more similar than ones more separated in time; (3) if morphological shape was affected by change in environmental factors like water depth, etc. then we would expect a strong correlation between changes in such factors and changes in shell shape. MANOVA showed significant shape differences in mean shape between stratigraphic units (p ≤ 0.01), but with considerable overlap in morphology. There was little change in the lower part of the section, but a large jump in morphology between the Genshaw Formation and the overlying Norway Point Formation at the top of the section. Maximum likelihood estimation suggests that morphological evolution was lightly constrained, but was not subject to strong stasis. Rates of evolutionary change were slow to moderate. Euclidean based cluster analysis demonstrated that samples from successive units were more similar than widely separated ones. Changes in water depth do not show any statistical correlation with changes in shell shape. However, shallow water depth samples were significantly different than medium depth samples. Collectively, these results suggest that shell morphology did not change through the lower 61 m, but made a sharp jump between the Genshaw and Norway Point formations. Erosional unconformities below Norway Point Formation coupled with environmental heterogeneity during this time interval, may have lead to provinciality in the Michigan Basin sections, thus resulting in greater morphological change. Thus, the change in the Norway Point samples could be interpreted as the origin of a new species, either from environmental selection pressure or by an immigration event. Comparison of Michigan Basin sections with the contemporary Appalachian Basin sections suggests that morphologies from the uppermost intervals in the Traverse Group show abrupt deviation from the lowermost intervals unlike the Hamilton Group where morphological overlap was prominent between lowermost and uppermost units. Thus, the morphological trend observed in the P. cf. lineata lineage in the Michigan Basin appears to be local in scope.
Rituparna Bose

Chapter 4. Morphological Shape, Episkeletobiont Analysis, and Life Orientation Study in Pseudoatrypa cf. lineata (Brachiopoda) from the Lower Genshaw Formation of the Middle Devonian Traverse Group, Michigan: A Geometric Morphometric Approach

Atrypids examined from the lower Genshaw Formation of the Middle Devonian (early middle Givetian) Traverse Group include a large assemblage of Pseudoatrypa bearing a rich fauna of episkeletobionts. We identified two species of PseudoatrypaPseudoatrypa lineata and Pseudoatrypa sp. A based on ornamentation and shell shape. Qualitative examination suggested that the former had fine-medium size ribbing, narrow hinge line, widened anterior, gentle to steep mid-anterior fold, a more domal shaped dorsal valve, and an inflated ventral valve in contrast to the coarse ribbing, widened hinge line, narrow anterior, gentle mid-anterior fold, arched shape dorsal valve, and flat ventral valve of the latter. Geometric morphometric analysis supported two statistically different shapes (p < 0.01) for the two distinct species. This study further examined these atrypids to investigate the influence of morphology on episkeletobiont settlement on the two Pseudoatrypa species. Among the 343 atrypid hosts examined, nearly 50 % were encrusted by episkeletobionts. Common encrusters included microconchids, bryozoan sheets, and hederellids. Less common encrusters included auloporid corals, cornulitids, tabulate corals, Ascodictyon, craniid brachiopods, and fenestrate bryozoans. Hederellids, auloporid corals, cornulitids, and tabulate corals encrusted a few living Pseudoatrypa hosts, but determination of pre- or post-mortem encrustation by the majority of episkeletobionts is equivocal. In a very few cases, episkeletobionts crossed the commissure indicating the death of the host. Some episkeletobionts, microconchids and the sheet bryozoans, were more common on Pseudoatrypa lineata, which exhibited more dorsal–ventral convexity than Pseudoatrypa sp. A. Perhaps, P. lineata may have provided a larger surface area for episkeletobiont settlement relative to Pseudoatrypa sp. A. In both the host species, encrustation was heaviest on the convex dorsal valve. This suggests that most of the encrustation occurred in a reclining, dorsal-valve-up life orientation of both species, in which the convex dorsal valve was exposed in the water column and the ventral valve remained in contact with the substrate. However, life orientations of these atrypid species could not be confidently predicted simply from the location preferences of episkeletobionts alone, as the life orientation of the host would also have been a hydrodynamically stable orientation of the articulated shell after death. Most episkeletobionts encrusted the posterior region of both dorsal and ventral valves of the two species, which suggests that the inflated areas of these valves, when exposed, favored the settlement of most episkeletobiont larvae.
Rituparna Bose

Chapter 5. Success of Geometric Morphometrics in Deducing Morphological Shape Change Patterns in Paleozoic Atrypids

Rituparna Bose
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