Mass extinctions have altered the trajectory of evolution a number of times over the Phanerozoic. During these periods of biotic upheaval a different selective regime appears to operate, although it is still unclear whether consistent survivorship rules apply across different extinction events. We compare variations in diversity and disparity across the evolutionary history of a major Paleozoic...

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s with Programs, v. 13, p. 491. LASK, P.B., 1993, The hydrodynamic behavior of sclerites from the trilobite Flexicalymene meeki: PALAIOS, v. 8, p. 219–225. MILLER, K.B., BRETT, C.E., and PARSONS, K.M., 1988, The paleoecologic significance of storm-generated disturbance within a Middle Devonian muddy epeiric sea: PALAIOS, v. 3, p. 35–52. PIPER, D.J.W., and STOW, D.A.V., 1991, Fine-grained turbid...

A nautiloid conch containing many disarticulated exoskeletons of Omegops cornelius (Phacopidae, Trilobita) was found in the Upper Devonian Hongguleleng Formation of the northwestern margin of the Junggar Basin, NW China. The similar number of cephala, thoraces and pygidia, unbroken thoraces, explicit exuviae, and lack of other macrofossils in the conch, indicate that at least seven individual t...

Introduction: The early Late Devonian, wet-target Alamo Event at southern Nevada resulted in one of the best-exposed and well-dated impact deposits ever documented, the Alamo Breccia [1]. Because post-impact geologic processes have modified, obscured [2, 3] and perhaps wiped away its original morphological and architectural relationships, the crater stratigraphy has remained uncertain. Thus, th...