448


Journal of Paleontology 92(3):442–458


of Isoxys chilhoweanus at both sites (Walcott, 1890, p. 626) could be construed as biostratigraphic support for the Little River Gap fossils having also been sourced from the Murray Shale (contra the concerns reviewed above), but it is also possible that Isoxys chilhoweanus has a long stratigraphic range that spans both the Murray Shale and the Helenmode Formation. Our new discoveries (below; Appendix) demonstrate that Walcott’s original fossil collection at Little River Gap was indeed made in the Murray Shale.


Subsequent fossil discoveries.—Since those initial discoveries in the 1880s and 1893, several workers have searched for additional body fossils at Little River Gap and Murray Gap. For nearly seventy years such efforts were almost invariably unsuccessful (e.g., King et al., 1952; Neuman and Nelson, 1965), although Neuman and Nelson (1965) reported finding fragments of an inarticulate brachiopod in the Helenmode Formation at Little River Gap. However, new roadcuts at Murray Gap were made in 1962


occurrence of the bradoriid in the new roadcuts was sufficient for Laurence and Palmer (1963) to confirm assignment of the Murray Shale to the lower Cambrian, based on the occurrence of the genus (then identified as Indiana Matthew, 1902) in lower Cambrian rocks elsewhere in North America and Europe. However, the Murray Shale bradoriid has subsequently been reassigned to Indota Öpik, 1968 (Siveter and Williams, 1997), a widespread genus that apparently ranges into the early middle Cambrian (Williams et al., 2007). Indeed, based on tentatively proposed junior synonymies, Indota tennesseensis itself might occur in the Ordian Yelvertoft Beds of Australia (Öpik, 1968; Siveter and Williams, 1997; Jones and Laurie, 2006). The Ordian Stage of Australia has been hypothesized to correlate to the uppermost Dyeran and a portion of the overlying Delamaran stages of Laurentia (Kruse et al., 2009; Peng et al., 2012). Given that the Murray Shale can be no younger than mid- Dyeran (see above), this suggests that—if the Australian occurrence is correct and the intercontinental correlation is accurate—Indota tennesseensis must have a relatively long stratigraphic range. Wood and Clendening (1982, p. 259) documented the


(Fig. 3.2, Localities MG2 and MG3; Appendix). The fresh roadcuts exposed much of the Murray Shale, from which additional specimens of the bradoriid Indota tennesseensis were recovered (Laurence and Palmer, 1963). Those new specimens came from ~6.1–18.3m above the base of the Murray Shale (Laurence and Palmer, 1963, p. C53). Wood and Clendening (1982) subsequently collected the bradoriid from 6.3–10.6m above the base of theMurray Shale at the same locality. Tracks and trails, but no body fossils, were recovered from the overlying portion of the Murray Shale (Laurence and Palmer, 1963). Acritarchs were also described from the lower part (6.3–46.7m above the base) of the Murray Shale at those roadcuts (Wood and Clendening, 1982, their “locality 1”)and from asimilar stratigraphic interval in a roadcut in northeasternmost Tennessee (Wood and Clendening, 1982, their “locality 2”). Those discoveries offer limited biostratigraphic utility. The


acritarch Medousapalla choanoklosma Wood and Clendening, 1982, which subsequently was recognized as a junior synonym of Skiagia ornata (Volkova, 1968) (see Zang, 2001 for taxonomic


revisions), from 10.6m above the base of the Murray Shale at their Locality 1. Skiagia ornata is widespread and has a long stratigraphic range, spanning from approximately the base of the trilobite-bearing portion of the traditional lower Cambrian through into the traditional middle Cambrian (Zang, 2001; Moczydlowska and Zang, 2006). The occurrence of this acritarch in Tennessee therefore suggests that the lower part of the Murray Shale is probably no older than the base of theMontezuman Stage. In summary, previous work unambiguously demonstrates


that the Murray Shale contains Isoxys chilhoweanus, Indotes tennesseensis, hyoliths, acritarchs, and abundant trace fossils. We herein confirm that the olenelline trilobite reported by Walcott (1890, 1891) was also sourced from the Murray Shale. The presence of brachiopods within the Murray Shale, as reported by Keith (1895), cannot be unambiguously substan- tiated due to vague documentation of the site(s) of collection and apparent loss of the specimens: it remains possible that they were actually sourced from the Helenmode Formation. The hitherto described and formally named fossils that were undoubtedly sourced from the Murray Shale, in combination with constraints imposed by the underlying and overlying units, suggest that the age of the base of the Murray Shale is no older than Montezuman (~520 Ma) and the top of the unit is no younger than mid-Dyeran (~514 Ma).


New paleontological work on the Murray Shale


The new trilobite-bearing locality.—Recent fieldwork on Chilhowee Mountain to the northeast of the classic Little River Gap roadcut resulted in the discovery of a 2m thick exposure of the Murray Shale (Fig. 3.1, Locality CM3; Appendix) that yielded a well-preserved cephalon of an olenelline trilobite (Hageman and Miller, 2016, fig. 7d) plus abundant hyoliths. Subsequent visits to the site have yielded six additional specimens of that trilobite, described below as Buenellus chilhoweensis n. sp. (see Systematic Paleontology section). The trilobite-bearing exposure is located in the bank of a


jeep trail on an otherwise forested hillside, and attempts to measure a stratigraphic section are frustrated by vegetation and soil cover. Nevertheless, it can be ascertained that the trilobite occurs in the upper portion of the Murray Shale within a few meters of the base of the overlying Hesse Quartzite. Other fossiliferous horizons on the hillside—lower within the Murray Shale and in stratigraphically underlying units—are consistent with this determination (see Appendix). Walcott’s original trilobite specimen (Fig. 4.8) is con-


specific with Buenellus chilhoweensis n. sp. The lithology of the newly discovered trilobite-bearing site matches that of the slabs bearing Walcott’s original trilobite specimen and the type material of Isoxys chilhoweanus. It is therefore possible that Walcott’s (1890, 1891) “Little River Gap” locality included


material sourced from the Murray Shale on the northwest-facing flank of Chilhowee Mountain northeast of Little River Gap, and maybe even from the trilobite-bearing site described herein (as was believed by Hageman and Miller, 2016, p. 146). Walcott’s (1891, p. 302) statement that his fossils were recovered from “about 20 feet above the quartzite in the upper shale bed” offers a potentially testable means of determining whether the new site is a re-discovery (or at least a stratigraphic


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