Registered users receive a variety of benefits including the ability to customize email alerts, create favorite journals list, and save searches.
Please note that a BioOne web account does not automatically grant access to full-text content. An institutional or society member subscription is required to view non-Open Access content.
Contact firstname.lastname@example.org with any questions.
Localized accumulations of small vertebrate fossils are relatively common in the Hell Creek Formation (latest Maastrichtian–Paleocene) and have traditionally been collected using nonstandardized field methods. The lack of established protocols has resulted in biased datasets and assemblage interpretations. Two commonly used collection methods were compared from two different microvertebrate localities in the Upper Cretaceous part of the Hell Creek Formation of southeastern Montana in order to identify their influence on taphonomic interpretations. The first of these methods was surface collection, in which weathered specimens were picked from the surface of the rock and in talus piles. This method commonly involves the selection and collection of larger and more easily identifiable specimens. The second method used in this study was quarrying and disaggregation, which requires excavation, collection, and total screen rinsing of a large volume of rock; this method was utilized in order to recover all fossils present. Both methods were applied at a sandstone-dominated and a mudstone-dominated site to assess an absolute concentration of fossils for each technique. Results of a quantitative analysis of these two common collection methods demonstrate how each one influences fossil recovery according to shape and size by skewing the characteristics of collected fossil assemblages and the taphonomic interpretations of microvertebrate accumulations. Although the study sites reflect only two possible types of microvertebrate localities, the results are applicable to many microvertebrate studies.
The Fossil Forest Research Natural Area (FFRNA) in New Mexico is the site of an exceptionally preserved fossil forest of Campanian age. This study combines paleoecological, taxonomic, and sedimentological analysis, together with GIS mapping of 68 fossil tree stumps and nine fossil logs, in order to provide a detailed description of this forest. Wood analysis of stumps illustrates that the forest is almost exclusively composed of conifers most likely related to the Cupressaceae. Reconstruction of the forest indicates that the conifers were mature and widely spaced, creating an open canopy woodland; however, leaf litter directly associated with the fossil woodland has not been preserved, so the detailed composition of its understory remains enigmatic. Analysis of the substrate in which the stumps were rooted suggests that trees grew in a gley soil under wet floodplain conditions. Mean sensitivity analysis of growth rings in the stumps indicates that small-scale environmental disturbances on the floodplain, such as periodic flooding, or regional environmental disturbances, such as volcanism, disrupted wood production. The death of the woodland was probably due to waterlogging and burial by suspended sediment associated with flooding. Despite the presumed dominance of angiosperms in disturbed, riparian environments during the Late Cretaceous, this study indicates that conifers were still dominant in some subenvironments at this time and could form mature open canopy woodlands on wet unstable floodplains.
In this paper we report on a rare fossil vertebrate burrow system in Upper Triassic (Norian) fluvial deposits of the Holy Cross Mountains in central Poland. The burrows are preserved mainly by prominent green infillings in red mudstone and claystone exposed in the wall of a clay pit. The mode of occurrence, morphology, and size of the burrows suggests that cynodont therapsids most likely constructed them.
The Ordovician is a period when novel reef ecosystems appeared along with new reef constructors and skeletal-dominated reefs. The Lower Ordovician (late Tremadocian) Fenhsiang Formation of the Three Gorges area in South China contains the oldest known bryozoan reefs (lithistid sponge–bryozoan and bryozoan–pelmatozoan reefs) alongside lithistid sponge–microbial reefs. The latter are characterized by the dominance of microbialites that encrusted and bound the frame-building sponges and inter-sponge sediments. In contrast, the lithistid sponge–bryozoan and bryozoan–pelmatozoan reefs are generally characterized by bryozoans that encrusted the frame-building sponges or pelmatozoans and grew to fill the inter-frameworks. These sponges and pelmatozoans did not construct the rigid frameworks unaided; their association with bryozoans enabled the development of small skeletal-dominated reefs with rigid frameworks. Skeletal-dominated reefs, for which frame-constructing and encrusting roles are conspicuous, were largely unknown before the Early Ordovician. The appearance of skeletal organisms (specifically colonial, encrusting bryozoans) enabled the development of skeletal-dominated reefs, which were pioneers in the rise of Middle–Late Ordovician reefs. The Early Ordovician establishment of skeletal-dominated reefs at the earliest stages of the Great Ordovician Biodiversification Event would have created novel niches and biological interactions that further promoted the evolution of reef-building and -dwelling organisms, as well as ensuing reef ecosystems.
Fossils of extinct fur seals and walruses (Carnivora: Pinnipedia) occur within rich vertebrate fossil assemblages recovered from the shallow marine Mio-Pliocene Purisima Formation, central California. Two isolated postcranial bones—a humerus and a radius—belonging to a juvenile fur seal (Pinnipedia: Otariidae) exhibit circular depressions. These bone modifications are associated with radial and circular fractures, and are characterized by inward displacement of the cortex. These depressions lack features typical of erosive invertebrate borings, trampling damage from media ( = substrate) interaction, puncturing by another object during diagenetic compaction, such as a clast embedded or associated with the modification, or pathologic bone modification. These features are best interpreted as tooth marks. These tooth marks lack certain characteristics of commonly reported marks inflicted by shark teeth, such as linear gouges and subparallel scrapes formed by xiphodont and serrated teeth. These bone modifications instead exhibit a circular shape and inward displacement of the cortex, consistent with puncturing by a conical mammal tooth. The size and distribution of the tooth marks, in concert with the known vertebrate assemblage from the Purisima Formation, indicate several possible producers of the bone modifications: a pilot whale or beluga-like cetacean, a terrestrial carnivore, a dusignathine or odobenine walrus, or a case of infanticide by a conspecific otariid.