We present zircon (U-Th)/He(ZHe) data for 17 Proterozoic basement samples from elevation profiles on the three peaks in Front Range of Colorado that are at elevations over 14,000 ft. (4267 m, locally known as “fourteeners”), with complementary Raman a sample subset. ZHe dates Longs Peak northern uniformly Late Cretaceous to Eocene (37 ± 1 Ma 137 2 Ma), while those Mt. Evans (34 606 18 Ma) and P...

Macrofossils of the late Ediacaran Period ( c. 579–539 Ma) document diverse, complex multicellular eukaryotes, including early animals, prior to Cambrian radiation metazoan phyla. To investigate relationships between environmental perturbations, biotic responses and evolutionary trajectories, it is vital distinguish ecological controls on global distribution macrofossils. The contributions temp...

, 65, 85–87.Prasad, N. and Roscoe, S.M., 1996. Evi-dence for anoxic to oxic atmosphericchange during 2.45–2.22 Ga from lowerand upper sub-Huronian paleosols.Catena, 27, 105–121.Prave, A.R., 1999a. Two diamictites, twocap carbonates, two dC excursions,two rifts: the Neoproterozoic KingstonPeak Formation, Death Valley, Califor-nia. Geology, 27, 339–342....

Almost all of the modern animal phyla appear to originate in a relatively compressed interval of time known as the Cambrian Explosion. Although several factors have been identified that may have enabled the Cambrian Explosion, there remains the question of the final trigger. The development of cellular differentiation, the capacity of a cellular lineage to become specialized permanently in resp...

—In post-Cambrian time, five events—the end-Ordovician, end-Frasnian in the Late Devonian, end-Permian, end-Triassic, and end-Cretaceous—are commonly grouped as the ‘‘big five’’ global intervals of mass extinction. Plotted by magnitude, extinction intensities for all Phanerozoic substages show a continuous distribution, with the five traditionally recognized mass extinctions located in the uppe...

The discovery of fossilized brains and ventral nerve cords in lower and mid-Cambrian arthropods has led to crucial insights about the evolution of their central nervous system, the segmental identity of head appendages and the early evolution of eyes and their underlying visual systems. Fundamental ground patterns of lower Cambrian arthropod brains and nervous systems correspond to the ground p...

The evolutionary divergence of cnidarian and bilaterian lineages from their remote metazoan ancestor occurred at an unknown depth in time before the Cambrian, since crown group representatives of each are found in Lower Cambrian fossil assemblages. We report here a variety of putative embryonic, larval, and adult microfossils deriving from Precambrian phosphorite deposits of Southwest China, wh...

Beautifully preserved organisms from the Lower Cambrian Maotianshan Shale in central Yunnan, southern China, document the sudden appearance of diverse metazoan body plans at phylum or subphylum levels, which were either short-lived or have continued to the present day. These 530 million year old fossil representatives of living animal groups provide us with unique insight into the foundations o...

, 65, 85–87.Prasad, N. and Roscoe, S.M., 1996. Evi-dence for anoxic to oxic atmosphericchange during 2.45–2.22 Ga from lowerand upper sub-Huronian paleosols.Catena, 27, 105–121.Prave, A.R., 1999a. Two diamictites, twocap carbonates, two dC excursions,two rifts: the Neoproterozoic KingstonPeak Formation, Death Valley, Califor-nia. Geology, 27, 339–342....