Charles D. Walcott's thin sections of the Middle Cambrian Burgess Shale of British Columbia, Canada, have yielded many specimens of the helically coiled microfossil Obruchevella delicata, as well as fragments of the cyanobacteria Marpolia and Morania, sphaeromorph acritarchs, and sclerites of the enigmatic metazoan Wiwaxia. Obruchevella of the Burgess Shale displays a spectrum of preservation styles ranging from tangled masses to well-developed helixes. All Obruchevella specimens are preserved in three dimensions, which suggests original skeletalization or early post-mortem mineralization of the organism. Morphologic analysis of Obruchevella supports an affinity with modern helical cyanobacteria. Study of all reported occurrences of Obruchevella indicates that: 1) the genus has been overly split into seventeen species; 2) no correlation between size and age of Obruchevella exists; and 3) most Obruchevella specimens are tightly coiled and have helix diameters four to six times their filament diameters.

Solitary rugose corals (Cnidaria, Rugosa) are common to abundant in the calcareous Box Member of the late Famennian Percha Shale (Lower expansa Zone) of southwestern New Mexico; the Box is best developed in the western part of the Percha outcrop belt. The corals include a number of forms characteristic of Strunian faunas throughout the world. Recognized here are Gorizdronia sp. cf. G. tenuis Rozkowska, Campophyllum? ursinum n. sp., Caninia cooperi n. sp., Siphonophyllia? folia n. sp., S.? corbicula n. sp., “Bothrophyllum” argenteum n. sp., “B.” argenteum argenteum n. subsp., “B.” argenteum bilateralis n. subsp., “B.” argenteum dibunophylloides n. subsp., Arachnolasmella elytra n. sp., and Cyathoclisia sp. A. This fauna is clearly ancestral to Carboniferous genera and species. Percha species, where represented by large populations, are seen to be remarkably variable, especially in axial structure.

Correlations exist between diversity and colonial growth pattern and variability in Paleozoic stenolaemate bryozoans. Habitats occupied by diverse communities contained colonies whose growth trajectories were different and were more highly constrained than those of low-diversity habitats. Because previous studies have not examined variability during colony growth, it was unclear whether observed variabilities were constant during growth (astogeny) or whether variability changed with age. Astogenetic trajectories and growth variability are here reexamined in populations of colonies of Heterotrypa ulrichi from the same high-diversity and low-diversity communities examined by Pachut (1989).

Growth trajectories of populations differ in both intermonticular and monticular regions of colonies for fundamental stereological characters. Total zooidal surface areas generally decrease during astogeny whereas zooidal densities increase. Surface areas per zooid also decrease with increasing age, but are consistently larger in monticular zooecia and in populations from low-diversity communities irrespective of the colony region sampled. These patterns of declining values are caused by increasing wall thicknesses, larger and more abundant mesozooecia and acanthostyles, and the development of maculae during colony growth. Larger values in low-diversity settings may have provided reproductive and feeding benefits necessary for survival.

Covariances reflect levels of morphological integration and are larger in populations from high-diversity communities in both intermonticular and monticular regions. Values differ more during early stages of growth (1–3) than later in astogeny (stages 4–5), and are consistently higher in intermonitulcar than in monticular zooecia. Lower levels of integration in monticules may be caused by spatial adjustments as the number of monticules increases across the expanding colony surface during growth. In general, stabilizing selection may have been weaker and less effective in establishing character covariance patterns in populations from low-diversity communities, perhaps because of greater environmental stress. These findings suggest that evaluations of astogenetic patterns and age-related changes in levels of morphological integration within a paleoenvironmental context are important in measuring species richness, in determining the direction of character evolution, and in assessing tempo and mode of evolutionary changes.

Clinal variation is systematic, morphologic variation within a species along a geographic or ecologic gradient. While common among today's biotas, it has rarely been well documented in the fossil record. It is, however, clearly displayed among the large populations of the Trentonian brachiopod genus Sowerbyella. In general, shallow agitated waters were populated by specimens with flat or round pedicle valve exteriors and ornately sculptured brachial valve interiors. Deeper, quieter facies were populated by forms with medial folds on pedicle valve exteriors and plain brachial valve interiors. This clinal variation was apparently the product of heterochrony with either the shallow-water forms having been peramorphic or the deeper water forms having been paedomorphic.

The distributions of the Sowerbyella clines are directly related to the facies developed within approximately eight million years of continuously deposited strata of the Trenton Limestone. Evolution of the Trentonian species of Sowerbyella appears to have been phyletic and locally adaptive. New clinal variants evolved by orthoselection during episodes when new environments were becoming available for occupation. The lower Trentonian transgression and the middle Trentonian shallowing were the major examples. Some clinal variants were eliminated when they failed to pass through facies bottlenecks in the lower and upper Trentonian. Thus, the history of the Sowerbyella lineage of the Trenton Group is the product of the facies-controlled production and selection of clinal variants. Clinal variation appears to be a central factor of phyletic evolution.

Sowerbyella kayi n. sp. is described.

New collections of Caradoc brachiopods from the lower half of the Fombuena Formation in the Iberian Chains (northeastern Spain) have yielded rich fossil associations that, in spite of the endemism of most of their species, permit detailed correlations with other sequences in southwestern Europe, Bohemia, and the British Isles. The oldest association studied occurs at the top of the basal oolitic ironstone of the Fombuena Formation, where 10 brachiopod species have been recorded; the youngest association occurs in sandstones in the middle part of the unit, having yielded seven brachiopod species. Herein, 11 forms are described including four new species (Gelidorthis carlsi, Saukrodictya tormoensis, Reuschella herreraensis, and Rostricellula marciali) and one new subspecies (Aegiromena aquila intermedia). The stratigraphic setting of the oolitic ironstone and its brachiopods suggest a correlation with similar beds that crop out at various localities in the Iberian Peninsula and northwestern France, as well as with the Zdice-Nucice Iron Ore, placed at the base of the Vinice Formation in Bohemia. The regressive–transgressive cycle, whose point of maximum shoaling coincides with the deposition of the apparently widespread ferruginous bed, is restricted to the Mediterranean Province and may have been caused by regional epeirogenic movements. The stratigraphic gap marked by the ironstone had been assessed at several localities in Iberia and Armorica; it ranges from late Costonian to Soudleyan, an age not in disagreement with the occurrence of a new species of Reuschella immediately above the ironstone of the Iberian Chains, since Reuschella is not known before the Soudleyan. Dalmanella unguis unguis, which has been recorded in the youngest assemblage and which in Wales is restricted to the Marshbrookian, is another important guide form in the problematic correlation between the Mediterranean Caradoc and the British type sequence.

The naticid gastropod predator–prey system has been cited as a possible example of coevolution. Previous work indicated that Miocene bivalves from the Chesapeake Group responded to naticid drilling with a predation-avoidance strategy of gradual thickness increase over evolutionary time. The present study examined whether the predators, Euspira heros (Say) and Neverita duplicata (Say), coevolved by increasing their efficiency in response to prey adaptation.

Neither predator showed significant trends in most characters thought to affect predator efficiency, including measures of globosity and aperture size relative to shell height. Stasis occurred for all such characters except Euspira aperture height, which showed a statistically significant decrease of 9 percent through the section. Morphologic trends occurred in two additional characters, shell thickness relative to height, and shell height. Euspira increased in thickness by 63 percent through the section; Neverita decreased in thickness by 37 percent (through slightly less section) and simultaneously increased mean height by 60 percent.

The size increase exhibited by Neverita could be interpreted as a coevolutionary response to increased prey defenses. Naticids are subject to predation by other naticids, however; the trends in size and thickness may be viewed instead as an evolutionary strategy to escape naticid predation, including cannibalism. Although the possibility of coevolution is difficult to eliminate, Chesapeake Group naticids appear to have evolve more in response to their own predators than to evolution of their prey.

Specimens of the ammonite genus Balatonites from the Middle Triassic of Austria and Hungary are analyzed morphometrically to obtain growth invariant character states. A new method transforming growth dependent qualitative characters into age invariant metric variables is developed. Weighted standardization as a method preserving univariate discriminatory efficiency is applied to character states preceding numerical classification procedures, resulting in a clearer separation of homogeneous groups in comparison to simple standardized data. All clustering and ordination procedures produce two identical classes, which are interpreted according to the cohesion concept as distinct biological species. In adherence to the taxonomic rules they are denominated as Balatonites egregius Arthaber and Balatonites balatonicus (Mojsisovics).

Very well preserved specimens of a macruran decapod from the Lower (Lacustrine) Member of the Ñirihuau Formation, northwestern Patagonia, Argentina, permitted description of Lammuastacus longirostris, a new genus and species of Parastacidae. The sedimentological and paleontological evidences provided by the faunal assemblage indicate a freshwater environment. This is the first certain record of a fossil Parastacidae from Tertiary deposits, most probably Oligocene. The fossil material shows similarities with Geocharax, the extant Australian genus considered to retain many primitive characters, and other related genera from New Zealand and Chile.

Seventeen flexible crinoids, including three new species, are reported from the Fort Payne Formation with new material from Cumberland, Clinton, and Russell Counties in south-central Kentucky and from Clay County, Tennessee. This study extends the geographic range of all taxa studied, as only seven species were previously known from the Fort Payne Formation. Fort Payne flexible crinoids include Taxocrinus colletti, Onychocrinus ramulosus, O. grandis n. sp., Nipterocrinus monroensis, Mespilocrinus romingeri, M. kentuckyensis n. sp., Gaulocrinus veryi, G. robustus, G. trauscholdi, G. bordeni, G. symmetros n. sp., Metichthyocrinus tiaraeformis, M. clarkensis, Forbesiocrinus pyriformis, F. saffordi, F. wortheni, and Wachsmuthicrinus spinosulus. Mespilocrinus columnals are also described, and the diagnosis of N. monroensis is emended. The Fort Payne Formation occurrence of O. exsculptus could not be verified. Forbesiocrinus multibrachiatus and Parichthyocrinus crawfordsvillensis are considered to be junior synonyms of Forbesiocrinus wortheni. Fort Payne flexible crinoids in the Lake Cumberland area occur at nine localities in four facies types. No more than three species occur at any Fort Payne locality.

Contrary to ideas that Cretaceous fresh waters contained few teleosts, there were several taxa of Esocoidei (pikes and relatives) in North American Cretaceous rivers. Dentaries and palatines of Campanian to Maastrichtian age all have C-shaped tooth bases and other distinctive features of shape and foramina. The fossils include at least three distinct kinds, two of which are described here as new genera and species in the Esocidae: Estesesox foxi n. gen. and sp. and Oldmanesox canadensis n. gen. and sp.

These old, diverse, and apparently primitive specimens show that pikes radiated when Eurasia and North America were still joined. Some references in the literature to the Cretaceous fish Platacodon Marsh are based on referred dentaries that are here identified as esocoid fossils. The Esocidae are the first example of a family of Recent North American freshwater teleosts that has been shown to have speciated in Cretaceous fresh waters and survived the terminal Cretaceous extinction.

The Duchesnean Lac Pelletier Lower Fauna, Cypress Hills Formation, Saskatchewan, includes 15 isolated teeth that are referred to the Carnivora (Mammalia). The fauna includes Miocyon magnus n. sp., Daphoenus cf. D. demilo, Hesperocyon sp., and indeterminate taxa; no members of the Creodonta were identified. This is the latest record of Miocyon and the earliest record of Hesperocyon. The fauna is transitional between Uintan carnivoran faunas that were dominated by miacids and the establishment in the early Chadronian of the White River carnivoran chronofauna, and suggests that the transition, which was largely a Duchesnean event, was gradual.