CONSTRUCTION AND USE OF PHYSICAL MODELS TO INTERPRET EARLY SILICOFLAGELLATE SKELETAL MORPHOLOGY AND DOUBLE SKELETONS

Three-dimensional physical models have been constructed of the silicoflagellates Variramus wisei and Cornua tapiae of Albian age from ODP Site 693 (Weddell Sea, Antarctica) and Santonian age from Devon Island (Canada Archipelago). The model generations evolved from cardboard and 18 gauge copper wire and are currently being constructed with 16 gauge floral wire. Separate wires for each strut are twisted together to form the apical structure. Measurements from photographs are used to determine spine, pike and substrut lengths and location relative to the center of the apical structure, the remaining form is manipulated into shape. An identical copy is made of each model.

These models allow examination of various unusual early silicoflagellate skeletal features, such as the spine- and pike-like limb terminations and other spines that are slightly offset along the limbs. Two identical models easily fit together to show previously unknown double skeleton configurations, with basal structures that extend along the limbs in a manner different from later silicoflagellates. The terminal structures of each limb extend to the strut attachments of the sibling skeleton, with the pike-like structures positioned behind the spine offset. All spines point away from the middle of the combined structure and spine and pike components are analogous to later silicoflagellates. The limbs of C. tapiae bend to a design that may be transitional to the basal ring structures of later Corbisema.