RARE Opabinid Fossil from Emu Bay Shale of Australia

Myoscolex ateles

Geological Time: Early Cambrian (~525 million years ago)

Size (25.4mm=1 inch): 40 mm long by 15 mm tall on a 33 mm by 58 mm matrix

Fossil Site: Emu Bay Shale, Big Gully, White Point, Kangaroo Island, South Australia

Fossil Code: AAF06

Price: $395.00 - sold


Myoscolex ateles emu bayDescription: This unusual creature was first thought when described in 1979 to be a polychaete worm. Recent specimens with more detail have shown it to have affinities with the unusual stem-group arthropod Opabinia regalis of the slightly younger Burgess Shale. Myoscolex is unusual in that the preservation is in apatite (calcium phosphate) rather than calcium carbonate as are most Emu Bay fossils. What are actually seen here are the muscle blocks separated by segmented boundaries, along with the outlines of the lobopodous segments themselves. These specimens show the oldest known instances of muscle tissue yet recorded, making them most unusual. During decay of muscle tissue, phosphates and fatty acids create a low-pH microenvironment. When such decay takes place in the absence of oxygen over several weeks, deposition of calcium phospahte can occur. This is a truly exceptional specimen, and as such is quite uncommon. I have included a reconstruction of the taxon showing what they looked like in life. The tip of the “trunk” and the tailfan have been restored after Opabinia. The Emu Bay Shale is Australia’s only Burgess Shale type deposit. It has fauna in common with both the younger Burgess Shale and the slightly older Chengjiang Biota. For this reason I have chosen to place this item in the Chengjiang Biota section. Unlike the Burgess Shale and Chengjiang Biota, however, the Emu Bay Shale deposits were a shallow water depositional environment. Perhaps the combination of shallow water and anoxia is what led to the unusual muscle preservation seen here. Whatever the case, this is a most unique offering, indeed!

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