208


Journal of Paleontology 92(2):207–220


from turbidity currents (Ferri et al., 2010). The Toad Formation is not recognized in the subsurface of B.C. and Alberta, where Anisian rocks are referred to the upper part of the Montney Formation and the lower part of the Doig Formation, both of which are considered lateral equivalents of the Toad Formation. The Montney Formation consists of shale, siltstone, and very fine-grained sandstone, whereas the Doig Formation is primarily siltstone and sandstone (Zonneveld, 2010). The Mon- tney and Doig formations represent deposition in a wide range of environments, fromoffshore turbidites (e.g.,Moslow, 2000) to the shoreface (e.g., Evoy andMoslow, 1995). Deposition of all of the Anisian rocks of B.C. took place on the margin of the ancestral North American continent, in the Peace River sub-basin of the Western Canada Sedimentary Basin (Davies, 1997). In Nevada, the Anisian rocks belong to the Fossil Hill


Member, shared by both the Prida and Favret formations. This member consists primarily of an alternation of silty shale and micritic limestone, deposited below storm wave base in an oxygen-poor environment (Monnet and Bucher, 2005b). These rocks were formed in the Star Peak Basin, an intra-plate exten- sional basin related to the Early–Middle Triassic Sonoma Oro- geny (Nichols and Silberling, 1977; Wyld, 2000). The Anisian of North America is divided into the lower,


middle and upper Anisian sub-stages, whereas the Aegean, Bithynian, Pelsonian, and Illyrian sub-stages are recognized in the Tethys region (Ogg et al., 2014). Tozer recognized five ammonoid zones in the lower and middle Anisian of B.C. (Tozer, 1967, 1994; Silberling and Tozer, 1968), and Bucher (2002) added an additional zone first recognized in Nevada (Fig. 1). In Nevada, a much larger number of ammonoid zones have been recognized through the work of Silberling


(Silberling and Tozer, 1968; Silberling and Wallace, 1969; Silberling and Nichols, 1982) and Bucher (1988, 1989, 1992a, 1992b, 1994; Monnet and Bucher, 2005b), who identified a total of eight zones and 14 subzones throughout the lower and middle Anisian (Fig. 1). The correlation between the ammonoid zones in Nevada and B.C. (Fig. 1) follows the work of Monnet and Bucher (2005a). The samples utilized for the present paper are primarily lower and middle Anisian in age, coming from the Lenotropites caurus, Paracrochordiceras americanum, Tetsaoceras hayesi, and Hollandites minor ammonoid zones in B.C., and from the Japonites welteri, Pseudokeyserlingites guexi, Lenotropites caurus, and Acrochordiceras hyatti ammo- noid zones in Nevada. Specimens belonging to the upper Anisian have been recovered from the subsurface of B.C., but cannot be related to the ammonoid zonation.


Materials and methods


Material for this study comes from 38 samples that were col- lected from 21 sections by various workers in northeastern B.C. and Nevada over the course of the past 30 years (Fig. 2; Table 1). Together, these collections yield more than 600 spe- cimens of Magnigondolella n. gen. Samples from northeastern B.C. come from exposures of the Toad Formation at sections on the Liard and Toad rivers (Toad River map area 094 N) and the Alaska Highway (Tuchodi Lakes map area 094 K), and from the Doig Formation recovered in core taken from subsurface hydrocarbon wells drilled in the vicinity of Fort St. John. Sam- ples from Nevada come from outcrop of the Prida and Favret formations exposed at sections in the Humboldt, New Pass, and Augusta mountain ranges of Pershing and Churchill counties.


Figure 1. Chart showing the occurrences of the conodont species reported in this paper within lower and middle Anisian ammonoid zones. Squares indicate occurrences within the ammonoid zones of Nevada, and circles indicate occurrences within the ammonoid zones of B.C. Dashed lines between symbols indicate the inferred stratigraphic range of these species. Note that the ranges of M. alexanderi n. sp., M. nebuchadnezzari n. sp., M. julii n. sp., and M. salomae n. sp. continue into the upper Anisian. B.C. ammonoid zones after Tozer (1994) and Bucher (2002); Nevada ammonoid zones and correlation after Monnet and Bucher (2005a).


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