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^JF ABSTRACT—Elasmostoma bajaensis n. sp., a pharetronid calcareous sponge, is described from the lower Eocene (P8 or P9 Zone) portion of the Bateque Formation, Baja California Sur, Mexico. This is the first Tertiary record of this genus and its first Western Hemisphere occurrence. Elasmostoma has been previously reported only from Jurassic and Cretaceous strata of Western Europe. -**
INTRODUCTION State University, Northridge (CSUN), locality 1220a. The lo- OMPLETE CALCAREOUS sponges are a rarity in lower Tertiary cality is on the south side of a minor canyon, at an elevation of C strata, and the presence of many well-preserved specimens 120 m and about 850 m southeast of the mouth of the canyon, of an early Eocene species in Baja California Sur, Mexico, is -- on the west side of Mesa La Salina, at 1.25 km southeast of the especially noteworthy. About 30 specimens of the calcareous intersection of 113°00'W and 26°45'N, San Jose de Gracia quad- sponge Elasmostoma bajaensis n. sp. were found in the early rangle map (number G12A64), Baja California Sur, issued in Eocene portion of the Bateque Formation, about 75 km south- 1983 under the authority of the Direccion General de Geografia. west of San Ignacio (Figure 1). The sponge specimens are remarkably well preserved, un- The base of the Bateque Formation is not exposed in the abraded, and all are three dimensional. Many are complete and study area, and the formation is unconformably overlain by all are free of matrix. The specimens form a growth series, Miocene volcanics of the San Isidro Formation. For a gener- ranging from 9 to 45 mm in height. One specimen was found alized geologic map of the area, see McLean et al. (1985). In attached to a larger sponge. The absence of indications of sig- the vicinity of the sponge locality, the Bateque Formation is nificant transport suggests that the specimens were recovered 190 m thick. It consists mostly of very fine sandstone interbed- virtually in situ. Modern calcareous sponges are most commonly ded with fossiliferous lenses. The sponges were found between found in shallow tropical waters (Rigby, 1987), and a similar 80 and 120 m above the bottom of the section at California environment for the Bateque sponges is supported by the pres- ence of associated specimens of stromatolites, coralline algae, discocyclinid foraminifera, colonial scleractinians, encrusting bryozoans, thick-shelled gastropods and bivalves, and sea ur- chin spines. The sponge-bearing portion of the Bateque Formation con- tains the planktonic foraminifera Morozovella aragonensis and M. a. caucasica. M. V. Filewicz and R. W. Fulwider (personal commun.) assigned these species to the early Eocene Globoro- talia aragonensis or G. pentacamerata Zone of Stainforth et al. (1975), which are equivalent to the P8 or P9 planktonic fora- minifera Zone as used by Berggren et al. (1985). The type specimens of the sponge are deposited in the Los Angeles County Museum of Natural History, Invertebrate Pa- Laguna leontology (LACMIP) collections. Ignacio / 27°- SYSTEMATIC PALEONTOLOGY Class CALCAREA Bowerbank, 1884 Order LITHONIDA Vacelet, 1981 Family ELASMOSTOMATIDAE de Laubenfels, 1955 Genus ELASMOSTOMA Fromentel, 1860 San Jose Type species.— By original designation, Elasmostoma fron- De Gracia descens Fromentel, 1860, p. 42. Lower Cretaceous (Neocomian), x> France. ELASMOSTOMA BAJAENSIS n. sp. Figure 2.1-2.9 Diagnosis.— An Elasmostoma with ostia almost always con- fined to the convex side; these ostia commonly have a raised border that encloses a single opening or clusters of two to five (rarely more) openings. Description. — Small to medium size (up to 45 mm height and FIGURE 7—Index map to California State University, Northridge (CSUN), 32 mm in diameter, walls up to 2.25 mm thick), ear-shaped to collecting locality 1220a, Bateque Formation, Baja California Sur, vase-shaped with deep spongocoel extending to near base of the Mexico. sr LACM.If 16 Z-Z-^ sponge; rigid skeleton consists of fused spicules, ostia-bearing 440 FIGURE 2—Elasmostoma bajaensis n. sp., CSUN locality 1220a. 1-3, holotype, LACMIP 7982, vertical view, ventral view showing ostia, and side view, x2.7; 4, paratype, LACMIP 7983, side view, x2.3; 5-8, paratype, LACMIP 7984, fragmental specimen; 5, side view of spongocoel wall; 6, side view of corresponding ostia-bearing wall, x 1.7; 7, lower right-hand corner of spongocoel wall shown in Figure 2.5, x9; 8, lower left-hand corner of ostia-bearing wall shown in Figure 2.6, x9; 9, photomicrograph of a thin section of a wall of paratype, LACMIP 7985, showing the ostia-bearing wall (at the top), the internal system of cross-connecting canals, and the spongocoel wall (at the bottom), x 40. 442 JOURNAL OF PALEONTOLOGY, V. 63, NO. 4, 1989 wall (almost always convex) covered by a smooth dermal layer arranged for permission for geologic studies and paleontologic usually with a few irregularly spaced wrinkles, ostia spaced about collecting in Baja. E. J. Enzweiller and R. M. Cote (California 1 mm apart and can have a raised border that encircles either State University, Northridge) provided collecting assistance in a single incurrent opening or groups of two to five (rarely more) the field. J. K. Rigby (Brigham Young University) provided incurrent openings; internally ostia lead into radially arranged important comments regarding the identification of the sponge canals that pass in middle of sponge wall into a system of cross- and reviewed an early draft of the manuscript. M. V. Filewicz connecting canals that lead into very closely spaced radially and R. W. Fulwider (Unocal Corporation) processed several arranged openings that feed into spongocoel (Figure 2.9), cross- rock samples and identified the foraminifera and calcareous connecting canals in middle of sponge wall 0.1 mm in diameter, nannofossils. may be up to 0.5 mm long before bending, without distinct radial pattern but may form elongate or irregularly shaped rigid REFERENCES expansions where adjacent tracts join; spongocoel wall (almost BERGGREN, W. A., D. V. KENT, J. J. FLYNN, AND J. A. VAN COUVERING. always concave) irregularly wrinkled and consisting of a porous 1985. Cenozoic geochronology. Geological Society of America Bul- texture; base of sponge with a small attachment area. letin, 96:1407-1418. FROMENTEL, M. E. 1860. L'etude des eponges fossiles. Memoires de Discussion. —Elasmostoma belongs to a heterogeneous group la Societe Linneenne de Normandie, 11:1-50. of calcareous sponges, known commonly as the pharetronids, GEINITZ, H. B. 1871-1875. Das Elbthalgebirge in Sachsen. Der untere whose skeletons are rigid (de Laubenfels, 1955; Rezvoi et al., Quader. Palaeontographica, 20:1-320. 1971; Hartman, 1983). Hartman's (1983) classification is used HARTMAN, W. D. 1983. Modern Calcarea, p. 40-54. In T. W. Broad- in this present report. head (ed.), Sponges and Spongiomorphs—Notes for a Short Course. Previously Elasmostoma has been reported only from Juras- University of Tennessee, Department of Geological Sciences Studies sic and Cretaceous strata of Western Europe (de Laubenfels, in Geology 7. 1955, Rezvoi et al., 1971). The presence of E. bajaensis n. sp. LAUBENFELS, M. W. DE. 1955. Porifera, p. E21-E112. In R. C. Moore in the Bateque Formation extends the geologic range of the genus (ed.), Treatise on Invertebrate Paleontology, Pt. E, Archaeocyatha and Porifera. Geological Society of America and University of Kansas into the early Eocene and extends the geographic range of the Press, Lawrence. genus into the Western Hemisphere. MCLEAN, HUGH, B. P. HAUSBACK, AND J. H. KNAPP. 1985. Recon- The ostia of Elasmostoma are reportedly common to both naisance geologic map of part of the San Isidro quadrangle, Baja convex and concave walls (de Laubenfels, 1955), but only one California Sur, Mexico. U.S. Geological Survey, Miscellaneous Field (Figure 2.5-2.8) out of about 30 specimens of E. bajaensis has Studies Map MF-1799. ostia on the concave wall. ORBIGNY, A. D. D'. 1850. Prodrome de paleontologie stratigraphique Elasmostoma bajaensis n. sp. most closely resembles E. nor- universelle des animaux mollusques et rayonnes. Vol. 2. Paris, 427 p. manianum (d'Orbigny, 1850) from Upper Cretaceous strata of REZVOI, P. D., I. T. ZHURAVLEVA, AND V. M. KOLTUN. 1971. Phylum Porifera, p. 5-97. In Y. A. Orlov (ed.), Fundamentals of Paleontology, East and West Germany and Northwestern France (Romer, 1864; Vol. 2, Porifera, Archaeocyatha, Coelenterata, Vermes. Israel Pro- Geinitz, 1871-1875). Romer (1864, p. 45, PI. 16, fig.6a , b) and gram for Scientific Translations, Jerusalem. Geinitz (1871-1875, p. 36-37, PI. 7, figs.7-12 ) also figured this RIGBY, J. K. 1987. Phylum Porifera, p. 116-139. In R. S. Boardman, species. Elasmostoma bajaensis differs from E. normanianum A. H. Cheetham, and A. J. Rowell (eds.), Fossil Invertebrates. Black- in the following features: smaller ostia, more ostia, and more well Scientific Publications, Palo Alto. complicated ostial areas that may include groups of two to five ROMER, F. A. 1864. Die Spongitarien des norddeutschen Kreidege- (rarely more) openings. birges. Palaeontographica, 13:1-64. Etymology.— The species is named for Baja California. STAINWORTH, R. M., J. L. LAMB, H. LUTERBACHER, J. H. BEARD, AND Material. — Thirty specimens showing excellent preservation. R. M. JEFFORDS. 1975. Cenozoic planktonic foraminiferal zonation Twenty of these are complete. Holotype, LACMIP 7982; para- and characteristic index forms. University of Kansas Paleontological types, LACMIP 7983, 7984, and 7985. Contributions, Article 62, 425 p. Occurrence.—Lower Eocene (P8 or P9 planktonic foraminif- VACELET, J. 1981. Eponges hypercalcifiees ("Pharetronides," "Scler- era Zone as used by Berggren et al., 1985) portion of the Bateque sponges") des cavities de recifs coralliens de Nouvelle-Caledonia. Formation, Mesa La Salina, Baja California Sur, Mexico, lo- Museum National d'Histoire Natural Paris, Bulletin, 4(3):313-351. cality CSUN 1220a. ACCEPTED 10 FEBRUARY 1989 R. L. Squires provided $100 in support of this article. ACKNOWLEDGENTS R. S. Vernis and R. R. Quintana (Departamento de Geologia, Universidad Autonoma de Baja California Sur, La Paz) kindly