Fig. 127-1. Type figure of H. rotundidorsatum, from Hantken (1875);
2. Lectotype of R. rotundidorsatum, after Horváth (2002).
ORIGINAL DESIGNATION: Haplophragmium rotundidorsatum Hantken, 1875
TYPE REFERENCE: Hantken, M., 1875. Die fauna der Clavulina szaboi-Schichen Theil 1 - Foraminiferen. K. Ungar. Geol. Anst., Mitt. Jahrb. Budapest, Bd. 4, Heft 1, p. 12. pl. 1, fig. 2.
TYPE SPECIMEN: The lectotype designated by Horváth (2002) is deposited in the Geological & Paleontological Department of the Hungarian Natural History Museum, Budapest (M.99.40). Additional syntypes are housed in the paleontological collections of the Natural History Museum, Vienna.
TYPE LEVEL: Not originally designated. Reported from the lower Clavulina szaboi Beds (Early Oligocene) and the Kiscell Clay (NP 24) of Hungary. The lectotype is from the upper part of the Kiscell Clay Formation (Zone P21a).
TYPE LOCALITY: Hanken reported the species from Ofen [Budapest], Nagy-Kovácsi, and Budakeszi, Hungary. The lectotype is from Budapest, Újlak (the former Holzpach brickyard).
DIAGNOSTIC FEATURES: Test free, planispirally coiled, involute, with 7 1/2 to 9 chambers in the last whorl, and a shallowly depressed umbilicus. Test is as thick as it is broad, with a broadly rounded periphery. Chambers increase in thickness rapidly as added, with alveoles evenly distributed throughout the chamber lumen. Sutures straight, may be somewhat incised. Aperture is usually an interiomarginal slit, but largest specimens may have supplementary areal pores. The test wall is finely agglutinated and relatively thin, and the test is often compressed.
SIZE: Eocene specimens are typically 0.30 - 0.70 mm in diameter; Oligocene specimens from Hungary range up to 3 mm in diameter.
SUSPECTED SYNONYMS: None verified.
OBSERVED OCCURRENCES: Reticulophragmium rotundidorsatum was originally described from Oligocene epicontinental deposits in Hungary (Hantken, 1875). In the Hungarian basin it occurs from the upper Eocene to the upper Oligocene (Sztrákos, 1979, 2002; Horváth, 2002). In Romania it has been reported (as Cyclammina rotundidorsata) to occur in large numbers in the upper Oligocene Lăpuş Valley Beds in the Preluca region (Popescu & Iva, 1971). It has also been reported (as Cyclammina rotundidorsata) from the Upper Eocene of the Outer Flysch Carpathians (Geroch & Nowak, 1984), from the Oligocene and Lower Miocene of Leg 38 DSDP sites in the Norwegian-Greenland Sea (Verdenius & Van Hinte, 1983), and from the Eocene-Oligocene of the North Sea and Labrador Margin (Gradstein & Berggren, 1981). Braga et al. (1975) reported it as Haplophragmoides rotundidorsatum from the upper Eocene of the Possagno section in Italy. Wenger (1987) recorded it from the Eggenburgian [Early Miocene] of the Bavarian Molasse deposits. Cicha et al. (1998) recorded its range as Late Eocene to Eggenburgian in the Austrian Molasse Basin. In Bulgaria it is reported from the middle-upper Eocene (Darakchieva, 1999). In the Arctic, Schröder-Adams & McNeil (1994) reported it as Reticulophragmium rotundidorsatus from the Oligocene to Upper Miocene of the Beaufort-MacKenzie Basin. In the North Sea basin, Charnock & Jones (1997) reported its first undoubted occurrence [as Cyclammina (Reticulophragmium) rotundidorsata] in the lower Oligocene just above the FO of Karreriella seigliei (29/2a-6SY well, SWC at 4453') but noted that presumedly caved specimens are found in the Eocene. These authors reported it usually disappears in the upper Oligocene (Zone P21), but noted a single occurrence from lower Miocene Zone N4. In Venezuela, it was reported (as Cyclammina rotundidorsata) from the basal part of the Pecaya Formation (upper Oligocene) of the Falcon Basin by Diaz de Gomero (1977). Preece (1999) illustrated specimens from the Miocene of offshore Cabinda (West Africa).
KNOWN STRATIGRAPHIC RANGE: Late Eocene to Late Miocene.
BATHYMETRY: Bathyal. We have not observed this species in abyssal ODP holes, in contrast to the modern species C. orbicularis (see below).
REMARKS: Reticulophragmium rotundidorsatum appears suddenly in Late Eocene flysch-type assemblages without any antecedent forms known to us. The lack of precurser forms suggests that the species may have migrated into bathyal assemblages from shallow water, since rotund cyclamminids are known from shallow-water Campanian deposits in France (Hofker, 1959) and in Antarctica and Argentina (Brian Huber & Norberto Malumian, personal communication to MAK). Many calcareous benthic species enlarged their bathymetric ranges into deeper water during the Late Eocene climatic cooling (Tjalsma & Lohmann, 1983; Miller et al., 1987), and we suspect that these paleoceanographic changes also affected agglutinated forms.
Fig. 127-2. Internal structure of R. rotundidorsata,
specimens from the Oligocene of Transylvania, from Popescu (1972)
ILLUSTRATIONS: Plate 127 - Reticulophragmium rotundidorsatum (Hantken)
Fig. 1a,b. Oligocene, "Autotype" from the Hantken Collection, (NHM, Wien), Kiscel marls, Budapest; Fig. 2. Upper Eocene, Silesian Unit of the Polish Carpathians, photo courtesy of G.D. Jones; Fig. 3a,b. Oligocene, Topotype from the Kiscell marls, Budapest, Specimen identified by Prof. L. Majzon, Cushman Collection; Fig. 4. Oligocene, ODP Site 985, Norwegian Sea, detail of aperture. Fig. 5a-c. Lower Miocene, MacKenzie Bay sequence of the Beaufort Sea, Orvilruk O-3, 2985-300 m.