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The problem of how accurately paraphyletic taxa versus monophyletic (i.e., holophyletic) groups (clades) capture underlying species patterns of diversity and extinction is explored with Monte Carlo simulations. Phylogenies are modeled as stochastic trees. Paraphyletic taxa are defined in an arbitrary manner by randomly choosing progenitors and clustering all descendants not belonging to other taxa. These taxa are then examined to determine which are clades, and the remaining paraphyletic groups are dissected to discover monophyletic subgroups. Comparisons of diversity patterns and extinction rates between modeled taxa and lineages indicate that paraphyletic groups can adequately capture lineage information under a variety of conditions of diversification and mass extinction. This suggests that these groups constitute more than mere “taxonomic noise” in this context. But, strictly monophyletic groups perform somewhat better, especially with regard to mass extinctions. However, when low levels of paleontologic sampling are simulated, the veracity of clades deteriorates, especially with respect to diversity, and modeled paraphyletic taxa often capture more information about underlying lineages. Thus, for studies of diversity and taxic evolution in the fossil record, traditional paleontologic genera and families need not be rejected in favor of cladistically-defined taxa.
Two simple plate parameters, P, the height of the plate measured normal to the plate base, and α, the angle formed between the plate base and the adjacent edge of that plate, serve to model crinoid aboral cup morphology. With few exceptions, the resulting theoretical geometries replicate the range of calyx morphology observed in the natural world. A theoretical morphospace, derived from these parameters, encompasses both the realized and unrealized possibilities of crinoid calyx construction. The model and the associated morphospace demonstrate that the occupation of crinoid cup space varies non-uniformly in time and space and suggest that functional constraints and/or ecological habit are important components of the distribution of cup morphology in time.
Museum exhibitions possess a long history of serving as useful tools for teaching both paleontology and evolutionary biology to college undergraduates. Yet, they are frequently under-appreciated and underutilized. However, they remain potentially outstanding resources because they can be used to meet a spectrum of learning objectives related to nature of science, real-world relevance, and student interest. Specifically, even small museum displays can provide: 1) authentic specimens, which often are more diverse, of higher quality, and historically more significant than those in teaching collections; 2) specimens in context, with other specimens and/or geological or biological background available; 3) examples of how fossils connect to virtually all of Earth and life sciences (explaining why they have so frequently been at the center of traditional “natural history”); 4) cross-disciplinary experiences, connecting science, art, technology, and history within a social context; and 5) opportunities for students to learn about teaching. A survey of instructor-developed activities performed within a host of natural history museums—with particular attention devoted to the Museum of the Earth, an affiliate of Cornell University—suggests that natural history exhibitions, regardless of size and scope, can complement and strengthen formal education in an undergraduate setting.