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Lieberman BS, Kurkewicz R, Shinogle H, Kimmig J, MacGabhann BA. (2017) Disc-shaped fossils resembling porpitids (Cnidaria: Hydrozoa) or eldonids from the early Cambrian (Series 2: Stage 4) of western U.S.A.PeerJ Preprints5:e2706v2https://doi.org/10.7287/peerj.preprints.2706v2
The morphology and affinities of newly discovered disc-shaped soft-bodied fossils from the early Cambrian (Series 2: Stage 4, Dyeran) Carrara Formation are discussed. These specimens show some similarity to the Ordovician Discophyllum Hall, 1847; traditionally this taxon had been treated as a fossil porpitid. However, recently it has instead been referred to another clade, the eldonids, which includes the enigmatic Eldonia Walcott, 1911 that was originally described from the Cambrian Burgess Shale. The status of various Proterozoic and Phanerozoic taxa previously referred to porpitids and eldonids is also briefly considered. To help ascertain that the specimens were not dubio- or pseudofossils, elemental mapping using energy dispersive X-ray spectroscopy (EDS) was conducted. This, in conjunction with the morphology of the specimens, indicated that the fossils were not hematite, iron sulfide, pyrolusite, or other abiologic mineral precipitates. Instead, their status as biologic structures and thus actual fossils is supported. Enrichment in the element carbon, and also possibly to some extent the elements magnesium and iron, seems to be playing some role in the preservation process.
We have revised our interpretation and description of the fossil specimens. Two new co-authors have been added to the paper. We have also replaced the previous figures and added several additional figures.
SEM image and spectra of KUMIP 389538
An SEM image and the spectra and weight percentages of elements for the portion of the D. cf. peltatum fossil, KUMIP specimen 389538, subjected to elemental mapping; maps shown in Fig. 1.
SEM image and spectra of another part of KUMIP 389538
An SEM image and the spectra and weight percentages of elements for a different portion of the D. cf. peltatum fossil, KUMIP specimen 389538, that was also subjected to elemental mapping; maps shown in supplemental file “ElementalmapsKUMIP389538a2.pdf”.
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