A NEW LOOK AT OLD DATA; AN EXAMPLE FROM THE ARTHROPODS

Abstract

Exceptionally preserved arthropod fossils from the Cambrian have gained a lot of attention as researchers hope to elucidate the arthropod stem lineage (e.g., Waloszek et al., 2007; Edgecombe, 2010). Progress is being made, though some issues remain contentious, because consensus on arthropod phylogeny seems as elusive as ever. These uncertainties hamper attempts to characterize the ground pattern of Euarthropoda through studies of extant taxa alone. While this makes the fossils all the more valuable, it also complicates their interpretation, as we do not always know what morphology to expect for representatives of a given stem lineage. This is less of a problem if the fossils are superbly preserved and thus the amount of interpretation required is minimal, as in fossils in Orsten type preservation (Maas et al., 2006). Unfortunately, the bulk of Cambrian fossils, often in Burgess Shale–type preservation, rarely lend themselves to straightforward description. Here, descriptions already contain a considerable amount of interpretation, influenced by the current understanding of the group under study. As that understanding changes, so does the interpretation of the fossils. Looking to the historical context of paradigms at the time they were established can be helpful. I will illustrate with the example of lamellipedian arthropods (trilobites and their allies) how a choice of a model that seemed reasonable at the time has led to a paradigm for the interpretation of limb morphology in the group that we only recently have started to question. The second decade of the last century saw a culmination of the early studies …