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Moderately well-preserved radiolarians are described from two measured sections of the Reef Trail Member of the Bell Canyon Formation (Middle Permian),exposed in the Patterson Hills, Guadalupe Mountains National Park, West Texas. The Reet Trail Member is the youngest member of a series of basinal marine carbonates deposited in the Delaware basin prior to the deposition of the Castile Formation evaporites, and represents the uppermost Guadalupian (upper Capitanian). The Guadalupian-Lopingian boundary is presumed to occur at or just above the top of the Reef Trail-Castile contact because of the presence of C. postbitteri hongsfuiensis ~ 2m below the top of the Reet Trail Member in sections in the Patterson Hills. A total of 30 genera containing 5 1 species were recovered from the Reef Trail Member, belonging to the orders Albaillellaria. Latentifistularia, Spumellaria, and Entactinaria. The following new taxa are described: Raphidociclicus scutum, Camptoalatas volaticus, Pseudoalbaillella delawarensis, Astroentactinia porosa, Stigmo-sphaerostylm favusa, Polyedroentactinia quadrats, Praedqflandrella firmata, P. protata, Copicyntra spinosa, Copicyntra irregidata, and Paracopicyntra punteta and Copicyntrcides natarovi The following taxa are emended: Raciditor scalae(Caridroii and DeWever 1986). and Klaengspongus Sashida 2000b. Near the top of the Reef Trail Member, there are marked fluctuations in the relative abundances of albaillellarian and latentifistularian species. Fluctuations are possibly controlled by paleoenvironmental changes associated with the onset of the end-Guadalupian extinction event. Biostratigraphically, the fauna most closely correlates with the widely recognized F. bipartitus - F. charveti Zone sensu Caridroit, which we now consider to be uppermost Guadalupian, not Lopingian, and to the Guadalupian F. charveti Zone of Sun and Xia 2006 from oceanic facies in China. Both older and younger Nustratigraphic markers also occur in the Reef Trail fauna, including Pseudoalbaillella longtanensis and A. yamakitai, requiring a reevaluation of the reliability of these albaillellarian taxa in biostratigraphy. [ABSTRACT FROM AUTHOR]

Well-preserved radiolarians are described from a road-cut of the upper Lamar Limestone Member of the Bell Canyon Formation along Highway 62/180 in the Delaware basin of West Texas. The upper part of the Lamar Limestone contains early Capitanian (late Guadalupian) conodonts and fusulinaceims and is assigned to the Reichelina tamarensis and the Jinogondotella postserrata zones. respectively. A total of 31 species were recovered from 17 samples in a ~6m section of micritic laminated limestone. Twenty species are reported from this locality for the first time, including 6 new species; Copiellintra ferula, Copiellintra lauretae. Hegleria agranusiforma, Hegleria globosa, Rectotormentum fengi, and Stigmosphaerostylus wildei. Sectioning and transmitted light microscopy of the spongy taxa reveals internal structures and allows For a more natural grouping of genera and species based on aspects of wall structure, rather than external geometry or presumed internal structure. All of the spongy taxa lack an entactinarian spicule and the genera Copiellintra, Copiellintra, Copicyntroides and Hegleria are reassigned to families within the Spumellaria. Lamar radiolarian assemblages show fluctuations in their faunal composition, alternating between albaillellarian-dominated assemblages composed mostly of Folliaicullus spp. and spumellariun-dominated assemblages composed largely of spongy taxa of spherical, oblate, to discoidal shape (Copiellintra, Copiellintra, Copicynttroides, Klaengspongus, Tetrapaurinella, and Hegleria). By far the most common radiolarians are spongy spumellarians and albaillellarians, but latenlifistularians also occur sporadically in samples, and entactinarians are rare and occur throughout the section. These marked faunal fluctuations are interpreted to be environmentally driven and is the subject of ongoing investigations using geochemical proxies to reveal paleoecological controls. [ABSTRACT FROM AUTHOR]