Stick insect on unsafe ground: does a fossil from the early Eocene of France really link Mesozoic taxa with the extant crown group of Phasmatodea?
2011
BRADLER, SVEN | Buckley, Thomas (Thomas R.)
The recently described Gallophasma longipalpis from Earliest Eocene French amber is considered to be a key fossil taxon that phylogenetically links ‘Mesozoic Phasmatodea’ with extant stick and leaf insects. However, our re‐evaluation of the evidence provided for this placement reveals that Gallophasma does not possess any unambiguous synapomorphies with extant forms, e.g. neither with Euphasmatodea nor with the more inclusive Phasmatodea. The fusion of abdominal segment 1 with the metathoracic segment, a derived character state present in both Gallophasma and Euphasmatodea, shows fundamental structural differences, and cannot be homologized between both taxa. We argue that the presence of a well‐developed, externally visible ovipositor and four‐segmented cerci in Gallophasma can be interpreted only as plesiomorphic with regards to all extant Phasmatodea, or even to Phasmatodea plus its putative sister groups Embioptera or Orthoptera. Gallophasma does not belong to the stem lineage of recent Phasmatodea, and is referred to best as ‘lower Neoptera’ or Polyneoptera incertae sedis. Therefore, this fossil may be central to reconstructing the ground pattern of the aforementioned orthopteroid lineages, and to determining wing character polarity within Polyneoptera.
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