San Vicente and Cartanyà—A new Triassic mysid
Mysidopsis oligocenicus from the lower Oligocene of NE Italy, although its generic status is not clear due to a suboptimal state of preservation (Wittmann et al., 2014). In addition, fossil mysid statoliths have been described inMiocene deposits of the brack- ish Paratethys (Voicu, 1974, 1981; Ionesi and Pascariu, 2011) and in the Aquitanian basin (SWFrance) (Steurbaut, 1989). Cartanyà (1991) first described a crustacean found in the
Triassic reservoir of the Pinetell (Montblanc, Spain) and iden- tified it with certain reservations as a “mysidacean.” In this paper, a black and white photograph and a drawing with the trace of uropodal endopod statocysts are presented. A second “mysidacean” specimen was reported by Cartanyà (1999b) without any reference to its morphology. Revision of the aforementioned fossil specimens allows us to re-describe in detail their morphological characteristics and ascribe them to a new genus and new species of the order Mysida. This paper presents the results of this review as well as a
discussion of the position of the new taxon between the different mysid families and subfamilies. The discovery of the fossil specimens from the Pinetell presented in this study extends the range of Mysida by ~70 Myr.
Stratigraphic and environmental settings
Marine conditions present in the Iberian region during the Triassic, especially during the late Anisian and the entire Ladinian, include a wide diversity of coastal and marine deposi- tional environments (shores, lagoons, tidal flats, reefs, etc.) (López-Gómez et al., 2002). The Prades Mountains are located in the middle of the
Catalonian Prelitoral Range, part of the Catalonian Coastal Ranges, and make up one of the most important physiographic units in the NE of the Iberian Peninsula. This unit is structured by a Paleozoic basement and a Mesozoic cover, which is com- posed for the most part of Triassic sediments (Cartanyà, 1999b). The main features of the European lithostratigraphic unit upper Muschelkalk in the eastern Prades Mountains are the presence
of mound-reefs and of laminated dolomites in the Alcover unit filling the interreef depressions (Calvet and Tucker, 1995; Tucker and Marshall, 2004). The Alcover laminated dolomites unit is up to 70–80m thick, and fills the inter-reef depressions with a sharp, undulating, and locally erosive unconformity. Stratigraphically it is dated as late Ladinian (middle Triassic) (Calvet et al., 1987; Calvet and Tucker, 1995), upper Muschelkalk, from 235–242 Myr (Lucas, 2010). According to Esteban et al. (1977), the Alcover unit is
composed of a clearly marine laminated dolomicrite. The uniformity of the lamination, its fine grain size, the absence of structures such as ripples, and presence of euhedral halite crys- tals, suggest a very calm and hypersaline depositional environ- ment. Also, these authors suggested the following depositional sequence: (1) the Alcover unit was deposited in an anoxic basin, affected by sporadic currents (of density?) and evolving to hypersaline conditions; (2) it settled among preexisting depres- sions due to former bioherms; (3) the deposit was caused by decanting from muddy suspensions. The Alcover unit has yielded an abundant Triassic fauna,
traditionally considered as originating in a shallow, lagoonal basin within an extended reef complex (Fortuny et al., 2011).
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The fossil assemblage is allochtonous and composed of floral and faunal groups such as land plants, jellyfishes, brachiopods, molluscs, arthropods, echinoderms, fishes, and reptiles (Villalta and Via, 1966; Via and Villalta, 1975; Beltan et al., 1989; Carrasco, 2012), but the reputation of these localities is based on the fossils being preserved in dolomicrite and their ichthyo- faunal diversity (Cartanyà, 1999a, 1999b). Via et al. (1977) suggested a general parallel between
sedimentological and paleobiological conditions of the Alcover unit and the well-known conditions of the Solnhofen-type limestones, based on several observations: the available paleontological collections show a clear predominance (79.6%) of nectonic organisms (e.g., fishes, reptiles, cephalopods, swimming decapods), and benthic organisms well represented by limulids, decapods, holothurians, crinoids, and brachiopods. In addition, there is a remarkable assemblage of semiterrestrial reptiles, insects, and several terrestrial plants. Algae, sponges, corals, bryozoans, gastropods, and echinoids are absent. The absence of burrowing organisms and the almost complete absence of fragmented or dislocated organisms suggest an allochtonous assemblage, passively transported by low-energy mechanisms, and an anoxic environment with strong salinity variations.
Materials and methods
Fossils were found in the El Pinetell outcrop of the Alcover unit (Fig. 1). A detailed description of this locality was presented by Cartanyà (1993, 1994, 1999a, 1999b). The analyzed individual, described as the holotype, was
initially classified as an indeterminate mysidacean by Cartanyà (1991, 1993, 1994). It is an epirelief in which the fossil protrudes from the surface. The main trace suggests that this animal was settled on the bottom with the ventral surface up. As a consequence of the fossilization process, many fine details of the appendages, such as setae or spines, have been loss. A second analyzed individual (paratype) is also an epirelief settled on the bottom in ventral position, showing the dorsal part of the body.
Figure 1. Locality map showing collection locality in the Alcover limestones unit of El Pinetell, in the district of Montblanc (Catalonia, Iberian Peninsula).
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