Cohorts of marine taxa that originated during recoveries from mass extinctions were commonly more widespread spatially than those originating at other times. Coupled with the recognition of a correlation between the geographic ranges and temporal longevities of marine taxa, this observation predicts that recovery taxa were unusually long-lived geologically. We analyzed this possibility by asses...

BACKGROUND The relationships of cartilaginous fishes are discussed in the light of well preserved three-dimensional Paleozoic specimens. There is no consensus to date on the interrelationship of Paleozoic chondrichthyans, although three main phylogenetic hypotheses exist in the current literature: 1. the Paleozoic shark-like chondrichthyans, such as the Symmoriiformes, are grouped along with th...

Members of the Asteroidea (phylum Echinodermata), popularly known as starfish or sea stars, are ecologically important and diverse members of marine ecosystems in all of the world's oceans. We present a comprehensive overview of diversity and phylogeny as they have figured into the evolution of the Asteroidea from Paleozoic to the living fauna. Living post-Paleozoic asteroids, the Neoasteroidea...

Size is among the most important traits of any organism, yet the factors that control its evolution remain poorly understood. In this study, we investigate controls on the evolution of organismal size using a newly compiled database of nearly 25,000 foraminiferan species and subspecies spanning the past 400 million years. We find a transition in the pattern of foraminiferan size evolution from ...

Stratigraphic correlations presented here for the ductilely deformed and metamorphosed rocks exposed in the Shadow Mountains indicate that they formed on the North American continental margin and are not exotic or significantly displaced from their site of origin. These strata represent a depositional history that spans Late Proterozoic and Paleozoic passive margin development, late Paleozoic t...

The phylogenetic positions of frogs, salamanders, and caecilians have been difficult to establish. Data matrices based primarily on Paleozoic taxa support a monophyletic origin of all Lissamphibia but have resulted in widely divergent hypotheses of the nature of their common ancestor. Analysis that concentrates on the character states of the stem taxa of the extant orders, in contrast, suggests...

Mesozoic-Cenozoic scleractinian corals were not derived by descent from late Paleozoic rugose corals. Rather, they probably originated from a group of Paleozoic sea anemones that survived into the Mesozoic after the extinction of the Rugosa at the end of the Paleozoic. This conclusion is based on three arguments: 1. all scleractinians have cyclic septal insertion in contrast to the serial inser...

Two distinct traditions exist in the study of ancient ichnofaunas, which may be termed the ethological (invertebrate ichnology) and the biotaxonomic (tetrapod ichnology). Consequently, there are two different kinds of ichnofacies, each peculiar to one tradition, and we term them ethoichnofacies (invertebrate ichnofacies) and biotaxonichnofacies (tetrapod ichnofacies). In the Paleozoic, the Chel...

The Upper Ordovician Trenton Group of New York State is one of a number of Appalachian limestones which yields paleomagnetic poles suggesting disturbance in the late Paleozoic. Calcite fractions dissolved from samples of a 238U 206pb a e of 454+8 Ma the Trenton Limestone define g (MSWD = 12.8) in excellent agreement with 40Ar-39Ar and U-Pb ages for the deposition of the underlying Diecke Benton...

Several northeast-trending transverse faults cut the Purcell succession and parts of the Lower Paleozoic succession in the Hughes Range. Relationships along unconfonnities within and at the base of the Lower Paleozoic strata provide evidence of the natilre and timing of displacement on these faults. Field mapping of the faults and unconformities hounding three Lower Paleozoic formntions have be...