Gilbert et al.—Himalayan Cambrian microfossils
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convex dorsum. Internal surface of conch smooth. The phos- phatic internal molds display no preserved surficial details or microstructure of the original organism. No apices are preserved.
Remarks.—The cylindrical conchs with roughly triangular cross sections identify these specimens as hyoliths, but no other features are preserved to permit more accurate taxonomic determination. Hyoliths previously described from the type section of the Parahio Formation have been assigned to two species, Hyolithes (Orthotheca) aff. plicatus and Hyolithes aff. danianus (Reed, 1910). These came from Hayden’s level 9, which is within the stratigraphic range of the material described herein. Observations of the available specimen and Reed’s (1910) illustrations suggest that his material was many times
larger than that preserved described herein. Because the material figured here does not obviously differ other than the size from Hyolithes aff. danianus, these forms are conceivably closely related. Unfortunately the figured material assigned to Hyolithes (Orthotheca) aff. plicatus is missing from the collections of the Geological Survey of India in Kolkata. That of Hyolithes aff. danianus is available, and will be re-described in separate reviewof all those Himalayan hyoliths that have been published previously and are presently still available. Singh et al. (2015, p. 2193-4, figs. 3.11, 3.12) considered
some specimens from the upper part of Stage 4 in the Parahio Valley to be “indeterminate hyoliths” or “indeterminate hylothids.” The latter name is a nomen dubium and presumably an error because on their pg. 2193 ?Cupitheca is also considered “hylothid.” The tubular material illustrated is poorly preserved and, based on the illustrations provided, we consider it to be taxonomically indeterminate.
Occurrence.—New material from Parahio Formation carbonates collected at 439.44m (PO15, Kaotaia prachina Zone), 776m (PO25), Paramecephalus defossus Zone), 880.93m (PV880, Orytocephalus salteri Zone), and 1242.40m (PO9, unzoned 5) above the base of the Parahio Valley section on the north side of the Parahio River, Spiti region, Parahio Formation, all within informal global Stage 5 of the Cambrian. Approximately ten specimens available.
Family Cupithecidae Duan, 1984
Type genus.—Cupitheca Duan in Xing et al., 1984. Diagnosis.—See Parkhaev and Demidenko (2010, p. 949).
Remarks.—Cupitheca are straight conical tubes, oval in cross-section, with the proximal part having a smaller diameter. The family Cupithecidae contains only the type genus.
Figure 10. Indeterminate ptychopariid meraspid cranidium and isolated trilobite free cheeks, all specimens coated with platinum/palladium before SEM imaging. (1–5) From 776m (PO25) above base of Parahio Valley section, Parahio Formation. (1) WIMF/A/3982, meraspid cranidium; (2–5) trilobite free cheeks, (2) WIMF/A/3983; (3) WIMF/A/3984; (4, 5) with small tubercles, WIMF/A/ 3985; (5)WIMF/A/3986. Scale bars represent 200 µm(1) and 500µm(2–5).
Occurrence.—Lower Cambrian of Antarctica, Greenland, China, Australia, and Kazakhstan, Spain, and middle Cambrian of the Himalaya.
Genus Cupitheca Duan in Xing et al., 1984
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