ICHNODISPARITY: ANOTHER VIEW OF CAMBRIAN EXPLOSION

Ichnodisparity has been recently introduced as a concept to assess the variability of morphologic plans, revealing major innovations in body plan, locomotive system and behavior patterns. Ichnodisparity is evaluated based on the identification of categories of architectural design, whereas ichnodiversity is measured in terms of the number of ichnotaxa (i.e. ichnogenera and/or ichnospecies).This study summarizes ninety ichnogenera and identifies forty architectural designs during the Precambrian-Cambrian transition (Ediacaran, Terreneuvian, Epoch 2). There are 22 architectural designs and 32 ichnogenera found in the Ediacaran, and 38 architectural designs and 84 ichnogenera for the Terreneuvian and Epoch 2 of Cambrian.Trace fossil data of the Precambrian-Cambrian transition reveals that ichnodisparity and ichnodiversity both expanded during this period. The significant increase in ichnodisparity and ichnodiversity in the Precambrian-Cambrian transition, reveals that the variety and numbers, body plans, locomotive modes and the complexity of behavior processes of organisms have increased dramatically in the Cambrian, which effectively support the Cambrian explosion event from the ichnological evidences. Combining the studies of ichnodisparity and ichnodiversity will further enhance the significance of ichnology in thestudy of evolutionary paleontology.

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