718
Journal of Paleontology 91(4):715–734 The upper Sierra Member decreases in thickness toward the
northwest from 150 m to 10 m (Villas, 1983). It is characterized by alternating shales and sandstones that frequently include highly fossiliferous sandstone lenses with calcareous cement. The fauna includes trilobites, gastropods, bivalves, rostro- chonchs, conodonts, and brachiopods and indicates the Sierra Member is late Dobrotivian (latest Darriwilian to earliest Sandbian) in age (Hammann et al., 1982; Sarmiento et al., 1995). Echinoderms from the Castillejo Formation are rare.
Diploporitans recovered include Calix rouaulti Chauvel, 1936 and fragmentary material belonging to Aristocystitidae gen. indet. sp. indet. (Carls, 1975; Kolb, 1978; Gutiérrez-Marco et al., 1996). A single complete crinoid specimen assigned herein to Heviacrinus melendezi has been collected from the siltstones of the lower part of the upper Sierra Member of the Castillejo Formation in the Castillejo hill section (Fig. 2, locality 3).
first echinoderms recovered from this member were the rhombiferans Heliocrinites? sampelayanus Meléndez, 1944 and Heliocrinites? isabellae Meléndez, 1944, which were described from poorly preserved specimens. Later, extensive sampling of the same horizons produced a moderately diverse echinoderm fauna that included the coronoid Mespilocystites lemenni Gutiérrez-Marco, Chauvel, and Meléndez, 1996, the diploporans Calix? cf. gutierrezi Chauvel and Meléndez, 1986 and Sphaeronitida fam. indet., and the rhombiferans Caryocrinites cf. rugatus Forbes, 1848, Hemicosmitida fam. indet., Heliocrinites sp., and Rhombifera bohemica Barrande, 1867 (Gutiérrez-Marco et al., 1996). The Huerva Member, which is also restricted to the
Fombuena Formation.—The Fombuena Formation overlies the Castillejo Formation and is divided into two members (Fig. 2). The lower Piedra del Tormo Member is comprised of a 1mthick ooidal ironstone overlain by 8mof marly shales and marlstones that contain abundant bryozoans, brachiopods, gastropods, benthic graptolites, and echinoderms. The ironstone is present at the base of the formation throughout the eastern Iberian Chain, but the bryozoan marls are restricted to the vicinity of Fom- buena. Brachiopods recorded in the ironstone and the overlying marls allowcorrelation with distant units in Iberia (Villas, 1992; Villas et al., 2006), and indicate the member is middle Berounian (late Sandbian to early Katian, Sa2-Ka1 stage slices) in age (Paris, 1979, 1981). The Piedra del Tormo Member is very fossiliferous. The
coronoid Mespilocystites lemenni. Samples fromthe La Peña del Tormo (locality 1) and Santa Catalina hill (locality 2) sections of Fombuena have yielded a remarkably well-preserved echino- derm fauna that was first introduced by Zamora et al. (2014, 2015a), and the crinoid content is formally described herein. Complete crinoid specimens have only been recovered from the fossiliferous horizon of the Huerva Member at these two localities. Higher in the section, occurrence of Dalmanella unguis unguis Sowerby and Murchison, 1839 in the middle horizons of the member suggests correlation with the Marsh- brookian (lower Katian, Ka1 stage slice). Finally, the uppermost levels of the Huerva Member have yielded a late Berounian (lower to middleKatian, Ka1-2 stage slices) fauna (Villas, 1995).
Paleoenvironmental interpretations.—Although the sedi- mentology and sequence stratigraphy of this section has not been studied in detail, general paleoenvironmental interpreta- tions can be made for collection localities based on lithology, taphonomy, and brachiopod assemblages. Both the Castillejo and Fombuena formations are comprised of siliciclastic rocks with fossiliferous horizons being predominantly made up of siltstones. Fossils are well preserved at all collection localities, including very delicate taxa (e.g., ramose bryozoans, astero- zoans, and solutes) and articulated echinoderm parts such as diploporan oral plates, crinoid arms, rhombiferan stems, and solute appendages (Zamora et al., 2014). This quality of pre- servation indicates the fauna experienced rapid burial and minimal transport, most likely from the effects of obrution events such as storms (Brett et al., 1997). In addition, brachio- pod assemblages from the sampled localities in both the Castillejo and Fombuena formations (Villas, 1985, 1992) are dominated by heterorthid brachiopods that have been established as valuable proxies for environmental interpreta-
tions based on the size and morphology of their ventral muscle field (Colmenar et al., 2013). Specifically, Svobodaina armoricana Babin and Mélou, 1972 in the Fombuena Forma- tion (Villas, 1992) and Heterorthina kerfornei Mélou, 1975 in the Castillejo Formation (Villas, 1985) are indicative of low- energy environments because of their small ventral muscles. On the basis of these combined lines of evidence, a low-energy offshore environmental setting is inferred for all three collection localities from the fossiliferous horizons of the Fombuena and Castillejo formations.
Fombuena area, overlies the upper marly horizon of the Piedra del Tormo Member and is comprised of sandstones with interbedded sandy shales. A single fossiliferous horizon (Fig. 2, localities 1 and 2), 20m above the base of the unit, has yielded a typical middle to early late Berounian (lower to middle Katian, Ka1-2 stage slices) brachiopod assemblage, echinoderms, and scarce trilobites. The crinoid specimens described herein from localities 1 and 2 were collected from this horizon. Although the stratigraphic position of the fossiliferous horizon of the Huerva Member varies laterally within the unit, fossil content, tapho- nomy, and preservation are nearly identical at all localities and, thus, are interpreted as correlative horizons (Villas, 1985, 1992). The first echinoderms from this level were described by Gutiérrez-Marco et al. (1996), who reported the rhombiferan Rhombifera sp., the diploporoid Diploporita indet., and the
Katian crinoid faunas of Gondwana and Laurentia
Overview of Katian crinoid faunas.—Recognition of secular changes in crinoid clade dominance through the Paleozoic has led to the identification of three crinoid faunal assemblages, termed the early, middle, and late Paleozoic crinoid evolu- tionary faunas (CEF; Ausich et al., 1994; Baumiller, 1994). Different assemblages of crinoid clades typically dominated each of the three evolutionary faunas in terms of both taxonomic diversity and relative abundance. For example, assemblages from the early Paleozoic CEF (Early Ordovician to Katian) were typically dominated by disparids, hybocrinids, and locally diplobathrid camerates. The Late Ordovician extinction trig- gered the transition to the middle Paleozoic CEF in the early Silurian, which was characterized by monobathrid camerates,
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