New middle Cambrian hyolith genus and species and echinoderm ossicles from the Georgina Basin, Australia
The study herein describes a new genus and species of orthothecid hyolith and numerous echinoderm ossicles. The internal mold of the hyolith bears an apical ridge and is of uniform width, distinguishing it from other known hyoliths. Biological significance of its internal apical structure is unclear, though hypotheses proposed include a streamlining effect and presence of a terminal spine on the original shell. Inclusion of the supposed Circotheca stylus depicted in Dzik (1980: fig. 7) into this species expands the newly described hyolith’s geographic range to Baltica and extends its temporal occurrence into the Late Cambrian. Some of the ossicles resemble echinoderm taxa (e.g., stylophorans and eocrinoids), but many ossicle morphologies share little to no similarities to known Cambrian echinoderms. Several fragmented ossicles bear phosphatic casts around their pores similar to Cantabria labyrinthica remains. Such results suggest that C. labyrinthica may represent echinoderm ossicles, not lobopodian plates as originally proposed by Clausen and Álvaro (2006).