ABSTRACT Beautifully fossiliferous strata in the Hamilton Group (Middle Devonian, central New York) constitute a rich “ecological archive” sufficient to probe and test foundational concepts in paleontology. The evident community stability of Hamilton faunas over 4–6 m.y.—including two proposed mechanisms for coordinated stasis—has ignited controversy. Resolving community structure and both taxonomic and ecological temporal persistence within the Hamilton Group thus becomes critical to testing whether these Hamilton communities are stable and whether they are ecologically “locked.” Toward this end, we conducted multivariate analyses (cluster and correspondence analysis) of marine faunas in 81 large samples (~300 specimens each) in shallowing-upward sequences of the Cardiff and Pecksport Members (Marcellus Subgroup, Oatka Creek Formation) of the Hamilton Group. Eight statistically and ecologically distinctive benthic communities characterize the vertical gradient, from depauperate, deeper-water dark shales below to species-rich shelf siltstones above. These communities correlate strongly with grain size, bioturbation intensity, bedding thickness, density of fossils, and faunal and ecological diversity. Species richness varies inversely with weight percent organic matter. We characterized taxonomic distributions using multivariate statistics; these statistical analyses were based on percentages of 50 taxa. In order of decreasing depth, the communities are: Cephalopod- Pterochaenia , Pterochaenia-Eumetabolotoechia , Eumetabolotoechia , Emanuella , Eumetabolotoechia-Ambocoelia , Arcuaminetes-Eumetabolotoechia , Arcuaminetes-Ambocoelia , and Mucrospirifer- Ambocoelia . The Cephalopod- Pterochaenia community represents a mixed benthic-pelagic fauna associated with the deepest and finest-grained facies. The Pterochaenia-Eumetabolotoechia , Eumetabolotoechia , and Emanuella communities have low to moderate species richness and are dominated by epifaunal, active suspension feeders, especially the small epibyssate bivalve Pterochaenia fragilis , and the pedunculate brachiopods Eumetabolotoechia multicostata and Emanuella subumbona . The Pterochaenia-Eumetabolotoechia community is an opportunistic fauna that developed when the substrate first became favorable for colonization by benthic organisms. To a lesser extent, this probably also holds true for the Eumetabolotoechia assemblage. Communities near the top of the shallowing-upward cycle— Eumetabolotoechia- Ambocoelia , Arcuaminetes-Eumetabolotoechia , Arcuaminetes-Ambocoelia , and Mucrospirifer-Ambocoelia —have higher taxonomic and ecological heterogeneity, with a more diverse array of trophic and locomotory groups than their counterparts in the finer-grained, and inferred deeper, facies. Cluster significance tests applied to all pairs of communities known from adequate numbers of samples demonstrated that the communities are statistically valid and distinctive. Multivariate means of all communities were significantly different; furthermore, most pairs of communities were drawn from populations that showed no overlap in terms of rectangular distributions. The community sequence and an ordination derived from the first two axes of the correspondence analysis provided relative depth curves. Our communities, with two exceptions, do not have clear counterparts among upper Hamilton Group faunas. The ecological locking model proposed to explain the stability of Hamilton faunas is not supported by our quantitative tests to date.

Abstract: Understanding the ecological roles of pterosaurs is a challenging pursuit, but one aided by a growing body of fossil evidence for their dietary preferences and roles as food sources for other species. Pterosaur foraging behaviour is represented by preserved gut content, stomach regurgitates, coprolites and feeding traces. Pterosaurs being eaten by other species are recorded by tooth marks and teeth embedded in their fossil bones, consumer gut content and regurgitate, and their preservation entangled with predatory animals. This palaeoecological record has improved in recent years, but remains highly selective. The Jurassic rhamphorhynchid Rhamphorhynchus , Cretaceous ornithocheiroid Pteranodon and azhdarchid pterosaurs currently have the most substantial palaeoecological records. The food species and consumers of these taxa conform to lifestyle predictions for these groups. Rhamphorhynchus and Pteranodon ate and were eaten by aquatic species, matching expectations of these animals as sea-going, perhaps partly aquatic species. Possible azhdarchid pterosaur foraging traces alongside pterosaur tracks, and evidence that these animals were eaten by dinosaurs and Crocodyliformes, are consistent with hypotheses that azhdarchids foraged and lived in terrestrial settings. Fossil evidence of pterosaur palaeoecology remains rare: researchers are strongly encouraged to put specimens showing details of dietary preferences, foraging strategies or interactions with other animals on record.

Abstract A siliceous permineralized peat block recovered from Hopen in the Svalbard archipelago hosts a low-diversity Late Triassic flora dominated by autochthonous roots and stems of bennettitaleans and lycophytes, and parautochthonous leaves, sporangia, spores and pollen from a small range of pteridophytes and gymnosperms. Some parenchymatous bennettitalean root cells show interactions with chytrid fungi and bacteria; the remains of other fungi and fungi-like organisms are dispersed within the peat’s detrital matrix. Cavities excavated through some roots and compacted detritus contain abundant coprolites probably derived from sapro-xylophagous oribatid mites, although no body fossils have yet been identified. Sparse larger coprolites containing leaf fragments attest to the presence of invertebrate folivores in the ancient ecosystem. The low-diversity flora, relatively few trophic levels and simple nutritional web, together with sedimentological aspects of the host formation and the peat structure, collectively favour accumulation of the organic mass as a fibric (root-dominated) peat within a temperate (high middle-latitude), well-aerated mire.

The vast majority of Emsian gastropods from Limestone Mountain, Medfra B-4 quadrangle, west-central Alaska (Farewell terrane) belong to species with lecithotrophic larval strategy. The present data show that there is no significant difference in the paleobiogeographic distribution of Emsian gastropod genera with lecithotrophic and planktotrophic larval strategies. Numerical analysis of the faunal affinities of the Emsian gastropod fauna from the Farewell terrane reveals that this terrane has much stronger faunal connections to regions like Variscan Europe, eastern Australia, and the Alexander terrane of southeast Alaska than to cratonic North America (Laurentia). The Canadian Arctic Islands is the only region of cratonic North America (Laurentia) that shows significant faunal affinities to the Emsian gastropod faunas of the Farewell terrane. The analysis also indicates a close faunal link between the Farewell and Alexander terranes. Published paleontological and geological data suggest that the Farewell and Alexander terranes represents tectonic entities that have been rifted away from the Siberia, Baltica, or the paleo-Pacific margin of Australia. The results of the present numerical analysis are not in conflict with any of these possibilities. However, the principle of spatial continuity of the wandering path prefers Siberia as the most probable “parental” paleocontinent for the derivation of both the Farewell and Alexander terranes.