Gilbert et al.—Himalayan Cambrian microfossils
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Figure 8. Chancelloria sp. Walcott, 1920, all specimens coated with platinum/palladium before SEM imaging. Scale bar represents 200 µm. (1–4) From 775.41m (PO24) above base of Parahio Valley section, Parahio Formation. (5–8) From 880.93m (PV880) above base of Parahio Valley section, Parahio Formation. (1) WIMF/A/3965, 775.41 m, 6+ 1 sclerite, view of adaxial surface; (2) WIMF/A/3966, 6+ 1 sclerite, view of abaxial surface; (3) WIMF/A/3967, 4+1 sclerite, oblique view of adaxial surface; (4), WIMF/A/3968, 4+ 1 sclerite, view of adaxial surface with central ray broken; (5) WIMF/A/3969, 6+1 sclerite, view of adaxial surface; (6) WIMF/A/3970, 5+ 1 sclerite with central ray missing, making orientation of sclerite difficult to determine; (7, 8) WIMF/A/ 3971, 4 +1 sclerite, oblique views of adaxial surface.
Stage 4 in the Parahio Formation to Archiasterella. In our
opinion, only one of their figured specimens (Singh et al., 2015, fig. 3.2) is sufficiently well preserved to warrant assignment to this genus, and we consider it to belong to A. dhiraji. The single other relatively complete chancelloriid sclerite illustrated by Singh and colleagues (2015, fig. 3.1) was suggested to belong to Chancelloria in the text of that paper (Singh et al., 2015, p. 2193) but was assigned to Archiasterella in the figure caption (Singh et al., 2015, p. 2194). Because ray number and its basal attachment is different from that of Archiasterella dhiraji,we do not consider it to belong that species or genus, but more comparable to Chancelloria (see below). Other putative chancelloriid material (Singh et al., 2015, fig. 3.3–3.9, 3.13–3.19) includes isolated rays that, in our opinion, do not merit assignment at the generic level.
Occurrence.—From carbonates collected at 78.07m (PO3, Haydenaspis parvatya level); reportedly also from ~20mhigher in the section (Singh et al., 2015), 439.44m (PO15, Kaotaia prachina Zone), 765.14m(PO21), 775.41m(PO24), and 776m (PO25) (all Paramecephalus defossus Zone); 836.36m (PO31 Orytocephalus salteri Zone); and 1242.4m (PO9, unzoned 5) above the base of the Parahio Valley section on the north side of the Parahio River, Spiti region, Parahio Formation. The PO3 occurrence is from the top of the informal global Stage 4 of the Cambrian System, and thus would traditionally be considered latest early Cambrian. Other collections span the informal global Stage 5 of the Cambrian. In addition, from carbonates collected at 74.11m above base of PU3 section (PI13), from Zanskar Valley, Parahio Formation which, based on co-occurrence with a new brachiopod species (Popov et al.,
2015) lies within the Paramecephalus defossus Zone and thus also belongs to Cambrian Stage 5. Approximately 300 spicules inspected.
Genus Chancelloria Walcott, 1920
Type species.—Chancelloria eros Walcott, 1920; Burgess Shale, middle Cambrian, British Columbia, Canada.
Diagnosis.—See Moore et al. (2014, p. 12).
Chancelloria sp. Figure 8.1–8.8
Material.—WIMF/A/3965-3971.
Description.—Isolated sclerites, poorly preserved as internal molds of the central cavity (lumen). Sclerites with tapering central ray, the presence of which is either evident or inferred, and lateral rays vary in number. Abundant sclerites represented by 4+1, 5+ 1, and 6 +1 form, with a few poorly preserved 7+1 sclerites also present. Sclerites are composed of four to seven distally tapering lateral rays each of similar proportions and radial symmetry arranged around a distally tapering central vertical ray projecting from the basal surface. Lateral rays reside within the basal plane, either parallel to the basal surface or raised slightly forming an acute abaxial angle to it. Specimens poorly preserved as isolated phosphatic internal
molds of sclerites, as in some A. dhiraji n. sp. described above (Fig. 6.1–6.8). Although sclerites are preserved as internal
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