The First Fossil Mysid Statolith (Crustacea) to Be Described From
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The first fossil mysid statolith (Crustacea) to be described from western Europe Etienne Steurbaut Laboratorium voor Paleontologie, Krijgslaan 281 /S8, B-9000 Geni. Belgium ABSTRACT: A mysid statolith is described from the Aquitanian in the Aquitanian Basin (Early Miocene of southwestern France). It is the first fossil mysid statolith from western Europe, and aiso the earliest on record from Eurasia. INTRODUCTION As the fossil resembles otoliths of some whalefishcs (see Fitch Mysids are rather small shrimplike crustaceans (generally 1979, figs. 1, 2), it was tentatively attributed to the Teleostei from 1.5 to 3 cm in length) with worldwide distribution. (bonyfishes) by the present author. Lately he came across About six hundred species are known, of which only a few Voicu’s illustrations of mysid statoliths which convinced him live in freshwater. Mysids are characterized by the presence that the previous determination is erroneous and that this of a pair of ballaststones or statoliths located, one in each form has to be assigned to the Mysidae. It should aiso be statocyst, at the base of the uropodal endopodites on both emphasized that the studied statolith belongs to a giant mysid sides of the telson (text-fig. 1, after Sars in Bames 1980). as it is about ten times larger thaii the ones figured by Voicu. Moreover it represents the earliest form known from Europe These small and massive, ellipsoidal to sphaeroidal bodies (mostly between 0.2 and 0.4 mm in length) have been known so far. to zoologists for more than a century. However their mor phology, internal structure, composition and stratigraphic SYSTEMATIC DESCRIPTION distribution have only been fully understood recently thanks Subphylum CRUSTACEA to the pioneering work of Voicu (1974, 1981). He noticed Order MYSIDACEA for the first time that statoliths from freshwater and brack- Family MYSIDAE ishwatcr mysids are composed of calcite (CaCOj), while ma "genus Mysicarum” pujoli (Steurbaut 1984) rine ones consist of fluorite (CaF,). Text-figure 2 shows the Text-figure 3 morphology and internal structure of some recent mysid statoliths (after Voicu 1981). “genus Teleosteorum" pujoli STEURBAUT 1984, p. 114, pi. 36, fig. 1. Fossil mysid statoliths are known from many regions of the Material and type-locality: One statolith, Uzeste, Moulin de world from Early Miocene times up to the present. They Gamachot. have been described erroneously as foraminifera, dinofla- gcllates, fish-otoliths or molluscan gastroliths. In Europe they Types: Holotypc, a left statolith, deposited in the Museum have been found only in the Paratethys so far (Central and d’Histoire naturelle de Bordeaux under number OT.C.38. Eastern Europe), and only as early as the Late Badenian Dimensions: Length 3.0 mm; height 3.6 mm; thickness 0.8 (Middle Miocene) (see Voicu 1981, tables 1,2 for their strati mm. graphic distribution). Type-level: Faluns de Bazas, Aquitanian, Early Miocene. Recently a large mysid statolith from the Aquitanian (Early Miocene) in the Aquitanian Basin (southwestern France) was described incorrectly (Steurbaut 1984, p. 114, pi. 36, fig. 15). It was found stored in the Museum d’Histoire naturelle de Bordeaux in a shoe box together with hundreds of fossil fish- otoliths collected by the late Prof. J. Chaine. The specimen came from “Moulin de Camachoi”, one of the classic fos- siliferous sites of the Aquitanian Basin, actually on private property and inaccessible (locality: Uzcste, map-sheet XVI- 30 (Bazas), coordinates x = 386.375, y = 242.840). About one meter of highly fossiliferous, slightly indurated, bluish grey sand is exposed there, overlain by a 2 m thick pale calcareous sand and a much thinner whitish sandy marl. These deposits are known as the “Faluns de Bazas” or Bazas Coquinas. The grey sands are particularly rich in molluscs (mostly Cardium, Arca and Ostrea), bryozoans, ostracods TEXT-FIGURE 1 and crabpincers (see Daguin 1948, p. 38; Moyes and Vig A. Mysis oculata relicta, a freshwater mysid (after Pennak in Bames). neaux 1954, p. 413; and Steurbaut 1984, p. 30). B. Telson and one uropod of Mysis (after Sars in Barnes). 188 micropaleontology, vol. 35, no. 2, pp. 188-190, 1989 Micropaleontology, vol. 35, no. 2, 1989 TEXT-FIGURE 2 Statoliths of Recent Black Sea species. I. Paramysis kroeyeri (Cemiavsky 1882) Bacescu 1940.11. Mesopodopsis slabberi (Van Beneden 1861). A = ventral view; B = dorsal view; C = edge view; d = dorsal side; v = ventral side; I-IV = canalicular groups; 1 = hilum; 2 = sensorial zone; 3 = gravitational zone; 4 = interzonal limit; 5 = interlamellar spaces; 6 = lamellae; 7 = sensorial canaliculi; 8 = synaptic cups; 9 = neural fibrils; IO = arc of circle (after Voicu 1981). TEXT-FIGURE 3 Left statolith of “genus Mysidarum" pujoli from the Early Miocene of the Aquitanian Basin. A = ventral view; B = dorsal view; C = side view; D = side view, anterior; 1 = hilum; 2 = sensorial zone; 3 = gravitational zone; 4 « lamellae. 189 E. Steurbaut : Fossil mysid statolith from western Europe Description: Large ellipsoidal specimen with hat ventral face ing the photographs and to N. Reynaert for typing the manu and strongly convex dorsal face showing shallow radial in script (Laboratorium voor Paleontologie, Gent). The Na cisions. Ventral face slightly corroded. Hilum small, circular, tional Fund for Scientific Research (Brussels) is gratefully about one tenth of the statolith’s total length. Sensorial zone acknowledged for the financial support. consisting of a central depression surrounding the hilum and an outer circular ridge. The number of lamellae of the sen REFERENCES sorial and the gravitational zone is unknown because of cor rosion. Lacking microscope slides (only one specimen is BARNES, R. D., 1980. Invertebrate zoology. Philadelphia: Saunders known and hence has to be preserved entirely) the statolith College, 1089 pp. ary formula and the arc of circle could not be determined. DAGUIN, F., 1948. L’Aquitaine occidentale. Géologie Regionale de la France, v. 5, 232 pp. Discussion: As to its general outline, this form is similar to Paramysis statoliths. However, since the statoliths of most FITCH J. E., 1979. The velvet whalcfish, Barbourisia rufa. added recent genera are still unknown and since no statolithary to California’s marine fauna, with notes on otoliths of whalefishes formula could be given, a generic name cannot be proposed. and possible related genera. Bulletin of the Southern California As sueli, the name pujoli has no taxonomic standing under Academy of Sciences, 78( 1 ):61—67. I.C.Z.N. rules, but is retained in conformity with my original MOYES, J., and VIGNEAUX, M., 1954. Observations sur des Os- description. tracodes des couches aquitaniennes de Villandraut (Gironde). Compte rendu sommaire et Bulletin de la Société géologique de Distribution: Only known from the Early Miocene of the France, 6(4):413—414. Aquitanian Basin (SW France). STEURBAUT, E., 1984. Les Otolithes de Tcléostéens de l’Oligo Palcoecology: Since the mysid statolith is composed of cal- Miocène d’Aquitaine (Sud-Ouest de la France). Palaeontograph- citc, it would seem, according to Voicu’s observations, that ica, abt. A. bd. 186. lfg. 1-6:1-162. the “Faluns de Bazas”, or at least a part of them, were formed VOICU, G-, 1974. Identification des Mysidés du Miocène supérieur in brackishwaterconditions. Thisagrees with data from other da la Paratethys Centrale et Orientale et leur importance paléon- animal groups (see Steurbaut 1984, p. 119). toloqique, stratigraphique et paléogéographique. Géologica Car pathica, 25(2):231-239. ACKNOWLEDGMENTS -------. 1981. Upper Miocene and Recent mysid statoliths in Central The author wishes to thank Dr. J. Prud’homme, Conservator and Eastern Paratethys. Micropalcontology, 27(3):227—247. of the Museum d’Histoire naturelle de Bordeaux (France) for providing the studied statolith. He is aiso grateful to D. Bavay Manuscript received June 14, 1988. for reproducing the figures, to T. Temmerman for reproduc Manuscript accepted July 1, 1988. 190.