Prediscosphaera
A new observation on the distal processes of Prediscosphaera
The holotype of Prediscosphaera spinosa (= Deflandrius spinosus) described by Bramlette & Martini (1964) is preserved in side view and shows a long, smooth stem terminating in blades that form acute angles with the stem. The paratype, in contrast, is a plan view of an elliptical placolith bearing an axial cross.
Using a mobile mount, I found that the side view corresponding to the holotype is associated with a circular placolith, rather than an elliptical one. At present, it remains unknown whether elliptical Prediscosphaera species also produce an identical side view.
The attached video further shows that circular Prediscosphaera can produce a second type of distal process, consisting of a two-tiered stem with nodose junctions terminating in perpendicular blades. This morphology has commonly been regarded as characteristic of subcircular to elliptical Prediscosphaera.
These observations indicate that circular Prediscosphaera possesses at least two distinct types of distal processes, demonstrating that distal-process morphology is not unique to a single species. Consequently, distal processes alone should not be regarded as definitive taxonomic characters without considering the morphology of the placolith itself.
Set number: 3251
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10µm