The earliest evidence of terrestrial animals comes from Cambrian-Ordovician trace fossils (MacNaughton et al., 2002), but the oldest body fossil to date is from the Early Silurian (Llandovery; Wilson and Anderson, 2004). Age estimates based on molecular clock assumptions, however, suggest a much earlier occurrence date (Pisani et al., 2004). As is the case for plant fossils, there appears to have been a radiation of terrestrial animals in the Late Silurian-Early Devonian when the fossil record of terrestrial animals becomes more abundant and diverse. It is interesting that the arthropods from the Siluro-Devonian (e.g., millipedes, centipedes, arachnids), including those known from the famous Gilboa, New York site (Shear et al., 1984; see Chapter 23), are all believed to have been predators (Shear and Selden, 2001). This underscores the probability that a complex terrestrial ecosystem existed prior to the Late Silurian (Jeram et al., 1990).
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