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.
Spinicaudatans are a diverse and geographically widespread group of small branchiopod crustaceans with an excellent fossil record. They inhabit ephemeral freshwater habitats with warm conditions and pH levels from neutral to alkaline. Many studies have been performed on the systematics of this group, also known as ‘conchostracans', although the paleoecology of these clam shrimp has not been widely analyzed. This paper examines some aspects of the relationship between spinicaudatans and their environments from the Upper Jurassic (Cañadón Asfalto Formation) of Argentina. We used sedimentological analysis to infer paleoenvironmental factors. Spinicaudatan features were also measured, including carapace size, growth band width, and growth lines. The results of this study reveal that the observed spinicaudatan species (Congestheriella rauhuti, Wolfestheria smekali, and Wolfestheria sp.) would have lived in carbonate lacustrine systems characterized by benthic microbial communities dominated by cyanobacteria. However, environmental factors such as oxygenation, pyroclastic deposits, and associated fauna (fish, ostracods, bivalves, and charophytes) were different at each locality. The spinicaudatan carapaces also show varying morphological features such as small or large carapace size, narrow or wide growth bands and low or high density of growth lines. These differences are related to abiotic (volcanic-oxygen) and biotic (fish and microbial) factors regarded as important agents for the development of the spinicaudatan populations.
A new mass death assemblage in Lower Cretaceous strata of east-central Utah contains well-preserved skeletons representing an ontogenetic series of individuals of Utahraptor, and at minimum two iguanodont grade ornithischian skeletons. The dinosaurs were entombed in ovoid-lensoidal, fine-grained sandstone sills linked by sandstone pipes and/or dikes and another basal lensoidal mass with scattered and broken iguanodont and sauropod bones and to an underlying gravelly sandstone bed. Exposed in the excavation high-walls are syndepositional normal-faults bounding graded ripple strata. Multiphased fluid over-pressurization in an artesian setting creating the structures. Trapping, killing, and subsequent burial mechanism was generated by variations of pressure in a localized artesian spring system that breached the surface and is the first such mechanism documented with numerous dinosaur victims.
Endobiotic tentaculitoids formed symbiotic associations with tabulates, heliolitids, rugosans, bryozoans, crinoids, stromatoporoids, and chaetetids from the Late Ordovician to the Carboniferous. The Ordovician was dominated by coral hosts, but there was a shift from mostly coral-based associations to stromatoporoid-based associations in the early Silurian. Specialization increased during the evolution of tentaculitoid symbiosis. In the Devonian, specialized symbiotic endobiont genera appeared which did not occur separately from their hosts.
Gastric pellets (i.e., regurgitated indigestible food remains) are rare in the fossil record. Here, we describe three gastric pellets with bird remains from the early Eocene Messel fossil site in Germany. A small, ball-shaped specimen that contains various broken bird bones resembles the pellets of owls and may have been produced by the Messel owl Palaeoglaux artophoron, which would make it the oldest owl pellet identified so far. The two other gastric pellets with bird remains have more elongated shapes and probably stem from snakes or other squamates. Both contain partially articulated bird skeletons, one of which belongs to an undescribed species that is otherwise unknown from the abundant avian fossil record from Messel. The fossil pellets described here therefore not only contribute to a better understanding of the avifauna of Messel, but are also important for reconstructing trophic webs and add to an understanding of the early Eocene Messel ecosystem.