Ammodiscus latus Grzybowski, 1898 Fig. 16. 1,2 - Type figures of Ammodiscus latus, 3,4 - type figures of Ammodiscus umbonatus, from Grzybowski (1898) ORIGINAL DESIGNATION: Ammodiscus latus Grzybowski, 1898. TYPE REFERENCE: Grzybowski, J., 1898. Otwornice pokładow naftonośnych okolicy Krosna. Rozprawy Wydziału Matematyczno-Przyrodniczego, Akademia Umiejętności w Krakowie, serya 2, vol. 33, p. 282, pl. 10, figs. 27-28. See also: Kaminski, M.A. & Geroch, S., 1993. A revision of foraminiferal species in the Grzybowski Collection. Grzybowski Foundation Special Publication, 1, 239-323, pl. 5, figs. 4a-5 [fig. 4a,b is the lectotype]. TYPE SPECIMEN: Not originally designated. Fifty-six specimens, including the specimen figured by Grzybowski in pl. 10, figs. 27-28 are preserved in the Grzybowski collection, deposited at the Jagiellonian University, Kraków. A lectotype specimen, designated by Kaminski & Geroch (1993) is registered as UJ-132-P, 1/38. Four specimens of Ammodiscus umbonatus Grzybowski, herein considered synonymous, are registered in slide 132-P, 1/39a,b. TYPE LEVEL: Late Middle Eocene to Late Eocene. Silesian Unit of the Polish Carpathians. TYPE LOCALITY: Not originally designated. Grzybowski (1898) listed specimens from three wells (Potok H-33, Potok H-34, and the Duniecki well in Toroszówka) and from an outcrop in Kroscienko Nizne, near Krosno, Poland. The specimens from the outcrop locality are preserved in the collection. The neotype locality is Grzybowski's sample collected from red clays outcropping in the right bank of the Wislok River at the village of Kroscienko Nizne. DIAGNOSTIC FEATURES: Test free, robust, comprised of a thick, evolute planispiral coil, with a distinct coil suture. In megalospheric individuals, the test is made up of 2 - 3 whorls, and the thickness of the test at the proloculus is less than in the coiled chamber, resulting in an umbilicus which is depressed on one or both sides. Microspheric individuals may have up to 5 whorls and do not generally have a depressed umbilicus. The diameter of the coiled chamber increases in size very slowly. The wall is made up of coarse agglutinated particles. Some specimens display either irregular coiling in the last whorl or a tendency to uncoil. The uncoiled portion, when present, is short and bends away from the test an angle from the previous direction of coiling. SIZE: Lectotype: 650 microns. Paralectotypes: 600 - 800 microns. Specimens measuring up to 2.4 mm have been observed from the Labrador Margin. In the largest specimens, the last whorl may be up to 0.45 mm in diameter. SYNONYMS: Ammodiscus cf. tenuis Brady. Rzehak, A., 1895, Ann. k.u.k. naturhist. Hofmuseums, 10, p. 214, pl. 7, fig. 5 [lower Tertiary, Moravia]. Ammodiscus umbonatus Grzybowski. Grzybowski, J. 1898, Otwornice pokładow naftonośnych okolicy Krosna. Rozprawy Wydziału Matematyczno-Przyrodniczego, Akademia Umiejętności w Krakowie, serya 2, vol. 33, p. 283, pl. 10, figs. 29-30. [Eocene, Polish Carpathians]. Lituotuba eocenica Cushman & Renz. Cushman, J.A. & Renz, H.H., 1948, Cush. Lab. Foram. Res. Spec. Publ. 24, p. 7, pl. 1, figs. 20-21 [middle Eocene, Trinidad]. OBSERVED OCCURRENCES: Ammodiscus latus has been reported from the upper Middle to Upper Eocene throughout the Carpathian region (e.g., Pokorny, 1953; Maslakova, 1955; Huss, 1966; Jurkiewicz, 1967, Lesko & Samuel, 1968; Samuel, 1969; Mjatliuk, 1970, Holzknecht, 1988). Its first common occurrence marks the base of the Ammodiscus latus Zone of Geroch & Nowak (1984). In Trinidad, we have found A. latus in the Middle-Upper Eocene of the Navet and "Hospital Hill" Formations of Trinidad [where it was originally described by Cushman & Renz (1948) as Lituotuba eocenica], and in the mid Oligocene (P. opima opima Zone) of the Cipero Formation. In the Labrador Sea it occurs in the upper Middle Eocene (FAD 44.6 Ma) to lowermost Oligocene (LAD 35.5 Ma) at ODP Site 647. In Hole 647A, the maximum relative abundance of this species is found in the basal Oligocene. In the North Sea and on the Labrador Margin, the average last occurrence of this species is observed in the Upper Eocene to Lower Oligocene (Gradstein et al., 1994). Charnock & Jones (1990) reported it as Ammodiscus tenuis (Brady) from the Eocene to Middle Miocene of the North Sea. This species also occurs in the Oligocene at ODP Site 767 in the Celebes Sea (Kaminski & Huang, 1991), and the Oligocene to Middle Miocene of the Kugmallit and MacKenzie Bay formations of the Beaufort-MacKenzie Basin (Schröder-Adams & McNeil, 1994). KNOWN STRATIGRAPHIC RANGE: Middle Eocene to mid Oligocene in the Tethys and Atlantic. Oligocene to Middle Miocene in the Arctic. BATHYMETRY: Outer neritic to abyssal. Specimens from updip wells on the Labrador Margin exceed a diameter of 2 mm, but specimens from abyssal ODP Site 647 in the Labrador Sea are smaller, between 600 and 800 microns in diameter. REMARKS: This species was first illustrated by Rzehak (1895) as Ammodiscus cf. tenuis from the lower Tertiary of Nikoltschitz in Moravia. Rzehak noted that many specimens in his collection display a tendency to uncoil. Pokorný (1949) determined the age of Rzehak's Nikoltschitz fauna as middle Eocene. Therefore, Rzehak's plesiotype is undoubtedly synonymous with Grzybowski's Ammodiscus latus and A. umbonatus, described three years later. Grzybowski's (1898) described Ammodiscus umbonatus as follows: "Test siliceous or finely agglutinated, planispirally coiled. Two and one-half to four distinct whorls. In the center there is a great inflation of the tube into a spherical central chamber, in which this species differs from the preceding [Ammodiscus latus]. Periphery rounded. Diameter 0.8 - 1.2 mm." The Grzybowski collection contains two slides with specimens of Ammodiscus umbonatus, registered as 1/39a,b. The figured specimens of Grzybowski are from a sample labelled "Kroscienko II, gray clays". One slide contains three specimens of A. umbonatus, all megalosphaeric, which are otherwise identical to the syntypes of A. latus. The second slide, labelled "Potok H-33, 25 m" contains a microsphaeric specimen of A. latus. It would appear that Grzybowski generally separated out megalosphaeric forms as A. umbonatus and microsphaeric forms as A. latus, but was not consistent. As such, we regard A. umbonatus as a synonym of A. latus. Grzybowski's type specimens of A. latus from Krościenko Niżne are relatively small in comparison to specimens from other localities in the Carpathians. The specimen corresponding to Grzybowski's figure 28 is preserved in the Grzybowski Collection. This is the only specimen which uncoils among the 56 specimens preserved in the collection. The syntypes are made up of 2 to 2 1/2 whorls and in general do not uncoil. We therefore selected one of the uncoiled specimens as the lectotype. Our specimens from the Skole Unit of the Polish Carpathians, are larger (up to 1.1 mm) contain more whorls and are similar to specimens from the North Sea and Labrador. The microspheric specimens from the Skole Unit possess up to 5 whorls and megalospheric forms have up to 3 whorls. Specimens from the Labrador Margin are largest (up to 2.2 mm) and typically contain 3 to 4 1/5 whorls. In these specimens the diameter of the last whorl may be as much as 400 microns. Megalospheric individuals from Labrador have a depressed umbilicus on one or both sides, similar to the Carpathian specimens. Ammodiscus latus differs from other Late Eocene ammodiscids in its large size, coarse wall and tendency to uncoil. However, a species which closely resembles it is Ammodiscus pennyi Cushman & Jarvis 1928, originally described from the Paleocene of the Lizard Springs Formation of Trinidad. Topotypes of A. pennyi in our collections overlap with A. latus in terms of size, number of whorls, and in the coarseness of the wall. Our specimens of A. pennyi differ from A. latus in not having a depressed umbilicus or a well-developed coil suture and although their last whorl may be somewhat irregular, they do not display a tendency to uncoil perpendicular to the axis of coiling. Megalospheric specimens of A. pennyi also show a greater increase in the diameter of the coiled chamber with ontogeny than do specimens of A. latus. ILLUSTRATIONS: Plates 16a & 16b - Ammodiscus latus Grzybowski Plate 16a Fig. 1a,b. Lectotype, Middle to Late Eocene Krościenko Niżne Poland, Silesian Unit, Polish Carpathians, Grzybowski collection 1/38; Figs. 2-3. Paralectotypes; Figs. 4-5. Middle to Late Eocene, Szklary Poland, Skole Unit, Polish Carpathians; Fig. 6. Middle Eocene, Istebna Unit, Silesian Unit, Polish Carpathians (rare uncoiling specimen); Figs. 7-8. Late Eocene (P15), Hospital Hill Formation of Trinidad, topotypes of "Lituotuba eocenica" of Cushman & Renz. Plate 16b Fig. 1. Middle Eocene, ODP Site 647, Labrador Sea, Sample 647A-51R-5, 94-97 cm; Fig. 2. Eocene, Labrador Margin, Dominion O-23 well, 6540'; Fig. 3. Eocene, Labrador Margin, Dominion O-23 well, 6540'; Fig. 4. Late Eocene, Labrador Margin, Indian Harbour M-52 well, 6570'; Figs. 5-6. Labrador Margin, Hibernia K-18 well, 1425 m.