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Journal of Paleontology 90(1):10–30
They may have been substitutes following damage or loss of the figured material. However, the specimen GSI19605, which is a
straight-sided tube, could be the specimen illustrated in Bhatt and Kumar’s (1980) figure 2. There are no characters that link this specimen to Oneotodus or to any other conodont. Becausewehaverecovered Archiasterella dhiraji n. sp. in
the bed (PO9) from which Bhatt and Kumar’s (1980) material appears to have been collected, our redetermination of the putative Oneotodus removes this argument for these rocks being EarlyOrdovician in
age.All other specimens figured as conodonts or paraconodonts by Bhatt and Kumar (1980) are considered in a forthcoming study on linguliform brachiopods (Popov et al., 2015), but none of them suggest late Cambrian or younger age. Because of this, and the fact that no conodonts or paraconodonts were found herein, the grounds for making a late Cambrian age determination for the upper part of the Parahio Formation as suggested by Bhatt and Kumar (1980) are no longer valid. As the trilobites and brachiopods also suggest middle Cambrian age, there is no current biostratigraphic evidence for any part of the Parahio Formation having a late Cambrian or younger age (contra Ramakrishnan and Vaidyanadhan, 2008, p. 581).
Systematic paleontology
The systematic part of this paper is by Gilbert and Hughes. Type and figured material are reposited on SEM stubs in the micro- fossil collection of the Wadia Institute of Himalayan Geology, Dehra Dun, Uttaranchal, India, along with some additional unfigured specimens on the same stubs. Additional Parahio Formation microfossils sorted by major taxon and collection, along with unsorted residues from the major collections, are reposited at the Cincinnati Museum Center, Ohio, under num- bers CMC IP71788, IP71791 - 71805, IP71807 - 71812.
Phylum Porifera Grant, 1836 Class Hexactinellida Sollas, 1870
Hexactinellid Family, genus and species indeterminate Figure 5.1–5.6
Material.—WIMF/A/3951-3955.
Description.—Relatively simple spicule morphologies, including four-rayed (tetract) spicules, and a five-rayed (pentact) spicule. There are twomorphotypes of tetract spicules, the first exhibits four equilateral rays that all reside in a single plane. The rays are thin and blade-like, tapering at the edges. The upper surface of each ray is slightly concave and the basal surface is slightly convex. The second tetract morphotype has four cylindrical, equilateral rays that reside in a single plane. Pentact spicules contain five rays that are at approximately 90° angles from each other, with four rays approximately residing in a single plane and a fifth ray protruding orthogonally from this plane. Some pentact spicules can display both straight and curved rays. All pentact rays have a circular cross section.
Remarks.—The Parahio Valley sponge assemblages described herein include simple spicule morphologies, all of which most likely belong to Hexactinellida due to their glass-like
appearance, which is unlike any of the phosphatic material seen in this study, and EDS confirms a siliceous composition. While generally well preserved, these isolated spicules are not further determinable taxonomically, as similar spicule types can occur in species belonging to different orders (Hartman et al., 1980; Dong, 1996). Their only stratigraphic significance is that they indicate late Neoproterozoic or younger rocks.
Occurrence.—New material from Parahio Formation carbonates collected at 775.41m (PO24, Paramecephalus defossus Zone) (containing pentacts and thin blade-like rayed tetracts), and 880.93m (PV880, O. salteri Zone) (containing cylindrical-rayed tetracts) above the base of the Parahio Valley section on the north side of the Parahio River, Spiti region, Parahio Formation, informal global Stage 5 of the Cambrian. Approximately 50 spicules inspectedintotal.
Phylum Incertae Sedis
Class Coeloscleritophora Bengtson and Missarzhevsky, 1981 Order Chancelloriida Walcott, 1920 Family Chancelloriidae Walcott, 1920
Remarks.—The family has recently been comprehensively reviewed by Moore et al., (2014, p. 844, 845). Articulated spe- cimens reveal soft-bodied, sessile, sac-like organisms, which resemble a barrel cactus, armored with star-shaped calcareous sclerites from which sharp spines radiated (Randell et al., 2005). Sclerite ray structure is here designated by using a simplified version of Sdzuy’s (1969) system of ‘m+n,’ with ‘m’ used to designate the number of lateral rays and ‘n’ used for the number of central rays. Identification of individual rays within a sclerite are here designated using the terminology of Moore et al. (2014).
Genus Archiasterella Sdzuy, 1969
Synonymy.—See Moore et al. (2014, p. 858). Type species.—Archiasterella pentactina Sdzuy, 1969
Other species.—Archiasterella charma Moore et al., 2014 (p. 859, figs. 3B, 3C, 3H, 11); A. elegans Demidenko in Gravestock et al., 2001 (p. 229, pl. 6, fig. 6); A. fletchergryllus Randell in Randell et al., 2005 (p. 992, figs. 3.1, 3.4–3.7, 4, 5, 7–9); A. hirundo Bengtson in Bengtson et al., 1990 (p. 55, pl. 29, figs.A–G; p. 56, pl. 30, figs.A–H); A. palmiformis Vasil’eva in Vasil’eva and Sayutina, 1988 (p. 195, pl. 30 fig. 4a, 4b);A. quadratina Lee, 1988 (p. 100, pl. 1, fig. 12); A. robusta Vasil’eva, 1985 (p. 168, pl. 45, figs. 7, 8); A. tetractina Duan, 1984 (p. 187, pl. 4, figs. 3a, 3b, 4a, 4b); A. tetractina (non Duan, 1984) Vasil’eva and Sayutina, 1988 (p. 195, pl. 30, figs.5,6;p.95, pl. 32, fig. 2);A. tetraspina Vasil’eva and Sayutina, 1993 (p. 138) for A. tetractina Vasil’eva and Sayutina, 1988 (p. 195, pl. 30, figs.5,6;p.195,pl. 32, fig. 2).
Diagnosis.—Sclerites lacking a central ray surround lateral rays, but with one ray oriented vertically or recurved over the other rays, with the other rays extending in the plane of the basal facet (abridged from Moore et al., 2014, p. 858).
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