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Malformations of trilobites are classified as healed injuries, teratological conditions, and pathological conditions. An improved method of recognizing such malformations combines information about the conditions under which cell injury can occur, the processes by which animal tissues react to injury, and trilobite morphology.Study of healed injuries of polymeroid trilobites shows that injuries attributed to sublethal predation tend to be most commonly preserved on the pleural lobes, the posterior half of the body, and the right side. Statistically significant differences in the number of predation scars between the right and left sides is interpreted as evidence of right-left behavioral asymmetry in some predators of trilobites or the trilobites themselves. Asymmetrical, or lateralized, behavior in present-day animals is one manifestation of handedness, and is usually related to a functional lateralization of the nervous system. Evidence of behavioral lateralization in some Paleozoic predators or prey suggests that those organisms also possessed lateralized nervous systems. Right-left differences in preserved predation scars on trilobites date from the Early Cambrian (Olenellus Zone), and are the oldest known evidence of behavioral asymmetry in the fossil record.Other examples of structural or behavioral asymmetry from the fossil record of animals are cited. Lateralization is recognized in representatives of the Arthropoda, Annelida, Bryozoa, Echinodermata, Cnidaria, Mollusca, Chordata, and Conodonta, and in trace fossils.

The Geological Society of America has sponsored versions of the geologic time scale since 1983. Over the past 30 years, the Geological Society of America Geologic Time Scale has undergone substantial modifi cations, commensurate with major advances in our understanding of chronostratigraphy, geochronology, astrochronology, chemostratigraphy, and the geomagnetic polarity time scale. Today, many parts of the time scale can be calibrated with precisions approaching less than 0.05%. Some notable time intervals for which collaborative, multifaceted efforts have led to dramatic improvements in our understanding of the character and temporal resolution of key evolutionary events include the Triassic-Jurassic, Permian-Triassic, and Neoproterozoic-Phanerozoic boundaries (or transitions). In developing the current Geological Society of America Time Scale, we have strived to maintain a consistency with efforts by the International Commission on Stratigraphy to develop an international geologic time scale. Although current geologic time scales are vastly improved over the fi rst geologic time scale, published by Arthur Holmes in 1913, we note that Holmes, using eight numerical ages to calibrate the Phanerozoic time scale, estimated the beginning of the Cambrian Period to within a few percent of the currently accepted value. Over the past 100 years, the confl uence of process-based geological thought with observed and approximated geologic rates has led to coherent and quantitatively robust estimates of geologic time scales, reducing many uncertainties to the 0.1% level. History of Chronometric-Chronostratigraphic Geologic Time Scales "For it was evident to me that the space between the mountain ranges, which lie above the City of Memphis, once was a gulf of the sea, like the regions

The Global Standard Stratotype‐section and Point (GSSP) of the Furongian Series (uppermost series of the Cambrian System) and the Paibian Stage (lowermost stage of the Furongian Series), has been recently defined and ratified by the International Union of Geological Sciences (IUGS). The boundary stratotype is 369 metres above the base of the Huaqiao Formation in the Paibi section, northwestern Hunan Province, China. This point coincides with the first appearance of the cosmopolitan agnostoid trilobite Glyptagnostus reticulatus, and occurs near the base of a large positive carbon isotopic excursion (SPICE excursion).

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A core drilling (Andrarum-3), from the classical locality at Andrarum, Scania, southernmost Sweden, penetrated a 28.90-m-thick Cambrian succession. The core comprises dark grey to black, finely laminated mudstones and shales with early concretionary carbonate lenses (stinkstones or orsten ) and a few primary carbonate beds. The middle Cambrian (provisional Series 3) part of the core comprises 17.35 m, whereas the Furongian Series (upper Cambrian) part covers the remaining 11.55 m. Nineteen trilobite and two phosphatocopine genera are present in the middle Cambrian, whereas the less diverse Furongian interval yielded four trilobite and three phosphatocopine genera. Other, less frequent, faunal elements include conodonts ( s . l .), brachiopods, sponge spicules, bradoriids, and coprolites. Trilobites and phosphatocopines were used to subdivide the core into seven biozones ranging from the Ptychagnostus atavus Zone to the Parabolina spinulosa Zone ( P . spinulosa Subzone). Carbon isotopic analyses ( δ 13 C org ) through the core show two important excursions, the negative DrumIan Carbon isotope Excursion (DICE) in the Pt . atavus Zone, and the Steptoean Positive Carbon Isotope Excursion (SPICE) beginning near the first appearance of Glyptagnostus reticulatus and extending upward into the Olenus and Agnostus ( Homagnostus ) obesus Zone. The DICE displays a peak value, in the samples at hand, of -30.45‰ δ 13 C org in the lower part of the P . atavus Zone. The δ 13 C org values increase through the overlying L . laevigata and A . pisiformis zones and display peak values of c . -28.00‰ δ 13 C org in the lowermost Furongian Olenus wahlenbergi and O . attenuatus subzones. Thereafter the values decrease significantly through the O . scanicus Subzone. Both isotopic excursions have been documented from several palaeocontinents, but never before from Baltica. Moreover, for the first time these excursions are recorded from organic matter in an alum shale setting. The recorded shift of +1.50-2.00‰ δ 13 C org is approximately half the magnitude of the SPICE documented from other regions. This discrepancy may be related to temporal variations in the type, origin, or diagenesis of the organic fraction analysed. ᮀ Biostratigraphy , Cambrian , carbon isotope stratigraphy , DICE , SPICE , Sweden , trilobites . Per Ahlberg [per.ahlberg@geol.lu.se], Niklas Axheimer [niklas.axheimer@geol.lu.se], Mats E. Eriksson [mats.eriksson@geol.lu.se], Birger Schmitz [birger.schmitz@geol.lu.se], and Fredrik Terfelt [fredrik.terfelt@geol.lu.se],

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