Topology, divergence dates, and macroevolutionary inferences vary between different tip-dating approaches applied to fossil theropods (Dinosauria).

Dated phylogenies of fossil taxa allow palaeobiologists to estimate the timing of major divergences and placement of extinct lineages, and to test macroevolutionary hypotheses. Recently developed Bayesian 'tip-dating' methods simultaneously infer and date the branching relationships among fossil taxa, and infer putative ancestral relationships. Using a previously published dataset for extinct theropod dinosaurs, we contrast the dated relationships inferred by several tip-dating approaches and evaluate potential downstream effects on phylogenetic comparative methods. We also compare tip-dating analyses to maximum-parsimony trees time-scaled via alternative a posteriori approaches including via the probabilistic cal3 method. Among tip-dating analyses, we find opposing but strongly supported relationships, despite similarity in inferred ancestors. Overall, tip-dating methods infer divergence dates often millions (or tens of millions) of years older than the earliest stratigraphic appearance of that clade. Model-comparison analyses of the pattern of body-size evolution found that the support for evolutionary mode can vary across and between tree samples from cal3 and tip-dating approaches. These differences suggest that model and software choice in dating analyses can have a substantial impact on the dated phylogenies obtained and broader evolutionary inferences.

Probabilistic divergence time estimation without branch lengths: dating the origins of dinosaurs, avian flight and crown birds.

Branch lengths-measured in character changes-are an essential requirement of clock-based divergence estimation, regardless of whether the fossil calibrations used represent nodes or tips. However, a separate set of divergence time approaches are typically used to date palaeontological trees, which may lack such branch lengths. Among these methods, sophisticated probabilistic approaches have recently emerged, in contrast with simpler algorithms relying on minimum node ages. Here, using a novel phylogenetic hypothesis for Mesozoic dinosaurs, we apply two such approaches to estimate divergence times for: (i) Dinosauria, (ii) Avialae (the earliest birds) and (iii) Neornithes (crown birds). We find: (i) the plausibility of a Permian origin for dinosaurs to be dependent on whether Nyasasaurus is the oldest dinosaur, (ii) a Middle to Late Jurassic origin of avian flight regardless of whether Archaeopteryx or Aurornis is considered the first bird and (iii) a Late Cretaceous origin for Neornithes that is broadly congruent with other node- and tip-dating estimates. Demonstrating the feasibility of probabilistic time-scaling further opens up divergence estimation to the rich histories of extinct biodiversity in the fossil record, even in the absence of detailed character data.

Phylogenetically structured variance in felid bite force: the role of phylogeny in the evolution of biting performance.

A key question in evolution is the degree to which morphofunctional complexes are constrained by phylogeny. We investigated the role of phylogeny in the evolution of biting performance, quantified as bite forces, using phylogenetic eigenvector regression. Results indicate that there are strong phylogenetic signals in both absolute and size-adjusted bite forces, although it is weaker in the latter. This indicates that elimination of size influences reduces the level of phylogenetic inertia and that the majority of the phylogenetic constraint is a result of size. Tracing the evolution of bite force through phylogeny by character optimization also supports this notion, in that relative bite force is randomly distributed across phylogeny whereas absolute bite force diverges according to clade. The nonphylogenetically structured variance in bite force could not be sufficiently explained by species-unique morphology or by ecology. This study demonstrates the difficulties in identifying causes of nonphylogenetically structured variance in morphofunctional character complexes.

Release of neurosecretory granules within the corpus allatum in relation to the regulation of juvenile hormone synthesis in Diploptera punctata.

The release of neurosecretory granules within the corpora allata (CA) of the viviparous cockroach Diploptera punctata has been compared in glands with intact nerves from the brain (Brain-CA) and those detached from the brain. Measurements of juvenile hormone (JH) synthesis in vitro, comparing these two conditions of the CA at several stages of vitellogenesis in adult females, showed lower production of hormone in Brain-CA complexes than in CA alone. Glands treated with tannic acid to trap exocytotic granules before fixation for electron microscopical examination showed, in sample sections, 10 times more exocytotic profiles in the glands with intact nerves to the brain than in the isolated glands. Sections treated with antibody against allatostatin I (Dip 7), a member of the neuropeptide family that inhibits JH synthesis by CA in vitro, showed neurosecretory granules in allatostatin immunoreactive nerves to be 75+/-4% of the granules in the sample of sections of CA. Because the total quantity of allatostatin in CA was found by ELISA not to vary significantly with changes in JH synthesis, it is concluded that the lower rates of JH synthesis by glands with intact nerves to the brain are most likely due to the release of small amounts of allatostatin within the CA.

Do surgical residents, emergency medicine physicians, and nurses experience significant radiation exposure during the resuscitation of trauma patients?

During this study we investigated the yearly risk of radiation exposure for surgical residents (group 1, n = 8), emergency department (ED) physicians (group 2, n = 6) and nurses (group 3, n = 97) participating in the resuscitation of trauma victims in the emergency department of a 500-bed teaching hospital. Dosimeter readings of the three study groups were recorded monthly over the 1-year study period. During the study interval, 758 patients underwent resuscitation following trauma; 2098 portable radiographs (758 chest films, 758 lateral cervical spine films, and 582 radiographs of the pelvis) were obtained during the resuscitation phase of these patients. The total radiation exposure for group 3 was significantly greater than that for groups 1 and 2 (340 +/- 50 vs. 160 +/- 112 and 20 +/- 14 mrem, respectively, p < 0.01). Individual residents received a significantly greater amount of radiation than ED physicians and nurses (20 +/- 28 vs. 3.3 +/- 2.0 and 3.5 +/- 2.0 mrem, respectively, p < 0.05). However, despite repeated exposure to radiation, individuals in the three groups did not exceed the safety limits of 0.05 Gy/year set by the National Council on Radiation Protection and Measurements. Based on the results of this study, we conclude that trauma resuscitation teams can provide quality care to their patients without concern over the detrimental effects of radiation exposure, provided that the basic principles of radiation protection are followed.