Rzehakina epigona (Rzehak, 1895)



Fig. 31. 1. Type figure of R. epigona, from Rzehak (1895);
2. type figure of Spiroloculina occulta, from Grzybowski (1901);
3. type figure of Spiroloculina waageni from Liebus & Schubert (1903)


ORIGINAL DESIGNATION: Silicina epigona Rzehak, 1895.

TYPE REFERENCE: Rzehak, A., 1895. Über einige merkwürdige Foraminiferen aus dem Österreichischen Tertiär. Annalen des K.K. Naturhistorisches Hofmuseum, 10, 213-230. Wien.

TYPE SPECIMEN: Our search for Rzehak's Collection of types has not uncovered its whereabouts. The collection is presumed lost.

TYPE LEVEL: Originally given by Rzehak as Early Cenozoic, according new observations the Upper Maastrichtian, Zdounky Unit (marginal facies of the Silesian Unit) of the Outer Carpathians in Moravia.

TYPE LOCALITY: Zdounky, Moravia. A "neotype locality" designated by Bubík & Kaminski (2000) is in a small abandoned quarry southeast of Zdounky village at the current site of the sports shooting range.

DIAGNOSTIC FEATURES: Test elliptical, with pointed anterior and posterior ends, compressed, central part strongly excavate on both sides. Periphery bluntly carinate. The coiling is planispiral, semi-evolute, with two chambers per whorl, alternating slightly more than 180°. The internal diameter of the chamber is thickest near the middle, and tapers towards the ends. The chambers of early whorls are oval in cross section; chambers of later whorls are triangular in cross section. Wall imperforate, finely agglutinated with smooth surface and much cement. Aperture a small oval or rounded-triangular opening, without a tooth.

SIZE: The holotype was reported to be 0.6 mm in length. Specimens from abyssal DSDP sites are somewhat smaller.

SUSPECTED SYNONYMS:
Agathammina dubia Grzybowski. Grzybowski, J., 1896. Rozprawy Wydziału Matematyczno-Przyrodniczego, Akademia Umiejętności w Krakowie, serya 2, 30, p. 282, pl. 8, fig. 49. [Paleogene, Polish Carpathians]
Spiroloculina occulta Grzybowski. Grzybowski, J., 1901. Rozprawy Wydziału Matematyczno-Przyrodniczego, Akademia Umiejętności w Krakowie, serya 2, 41, p. 261, pl. 7, fig. 25 [type specimen re-illustrated by Kaminski & Geroch, 1993, pl. 15, fig. 3].
Spiroloculina waageni Liebus & Schubert. Liebus, A. & Schubert, R.J., 1903. Jahrbuch der k.k. geologischen Reichsanstalt, 52 (for 1902), p. 287, pl. 15, fig. 1a-c [Campanian-Maastrichtian, Klippen Zone in Gbellan Slovakia]

OBSERVED OCCURRENCES: The paleobiogeography of Rzehakina epigona and related forms was first studied in detail by Thalmann (1949) and Hiltermann (1974). The R. epigona group has now been reported from Late Cretaceous to Paleogene agglutinated foraminiferal assemblages from the Atlantic, Caribbean, Mediterranean, and Pacific regions. It was recorded from the Velasco Shale of Mexico (Cushman, 1926; White, 1928); the Lizard Springs Formation of Trinidad (Cushman & Jarvis, 1928; Kaminski et al. 1988); from a sample of presumed Paleocene age dredged from the Burdwood Bank of the Falklands Plateau (Macfadyen, 1933); from the Upper Cretaceous of Ecuador (Hiltermann, 1974); from the Upper Cretaceous Colon Shale of western Venezuela (Fuenmayor, 1989); and from the Upper Cretaceous to Lower Paleogene of the Alpine-Carpathian region of southern and central Europe (Rzehak, 1885; Jedlitschka, 1935; Majzon, 1943; Noth, 1951, 1954; Geroch, 1960; Pokorný, 1960; Hillebrandt, 1962; Grün, 1969; Mjatliuk, 1970; Hiltermann, 1974; Săndulescu, 1972; Beckmann et al. 1982, Geroch & Nowak, 1984). In the Atlantic region, Beckmann (1994) recorded its range as Santonian to Late Paleocene (P5) in Trinidad; Krasheninnikov & Pflaumann (1967) reported specimens from the Upper Cretaceous of DSDP Site 368 on the Cape Verde Rise; Volat et al. (1996) reported its range as Campanian to Maastrichtian offshore Gabon; and Koutsoukos (2000) reported it from the upper Coniacian-Maastrichtian of the Sergipe Basin, NE Brazil. In the Pacific region, it was reported from the Paleocene Lodo Formation of California (Mallory, 1959), the "Teratian to Teurian" [Coniacian/Santonian to Paleocene] of New Zealand (Hornibrook et al. 1989; Scott, 1961), from the upper Paleocene of the Tawanui section in New Zealand (Kaiho et al. 1996), from the Campanian to Maastrichtian Rosario Formation of southern California (Sliter, 1968), from the Maastrichtian to Paleocene of Kamchatka (Serova, 1969), from the Turonian to Paleocene of Hokkaido, Japan (Takayanagi, 1960; Kaiho, 1992; Kaiho et al., 1993; Kaiho & Hasegawa, 1994), and from the Paleocene of DSDP Site 283 in the Tasman Sea (Webb, 1975). In Hokkaido, Kaiho et al. (1993) defined a mid-Turonian "Rzehakina epigona Interval Zone (KB3)" based on the FO of the species, and Nishida et al. (1998) described an Upper Turonian to Coniacian "Silicosigmoilina ezoensis - Rzehakina epigona concurrent range zone" based on the FO of the latter species. Brohi (1994) illustrated a specimen from the Paleocene Jamburo Group of the Khuzdar District in Pakistan. In Papua New Guinea, Milner (1997) found this species in the Paleocene Burns Peak beds and Moogli Mudstone.
In our material, Rzehakina epigona was found in high abundance in samples from the lower bathyal Campanian to Paleocene Tangier Formation of the North African Margin (Rif, Morocco). It occurs consistently but in lower numbers in the flysch sediments of the Alpine-Carpathian region and at Zumaya, Spain. It is comparatively rare in the high-latitude slope assemblages of the Labrador Margin, Central North Sea, offshore mid-Norway, western Barents Sea, and in flysch-type assemblages at DSDP Sites 141, 367 and 368, and in the Paleocene of the Cauvery Basin, India. Our oldest records are from the mid-Turonian of offshore mid-Norway, where it occurs as isolated specimens. We did not observe any specimens of the R. epigona group in the deep abyssal assemblages from DSDP/ODP Sites 137, 543, 603, and 641. It occurs very rarely in Campanian-Maastrichtian Scaglia-type assemblages from Gubbio (Kuhnt, 1990). Our examination of an additional 60 samples from the Upper Cretaceous of the Contessa Valley section did not uncover a single specimen. In California, we observed R. epigona in a Campanian sample from the north flank of Mt. Diablo, Contra Costa County (Colburn, 1960; Field Trip No. 5).

KNOWN STRATIGRAPHIC RANGE: Mostly Campanian to Early Eocene Zone P9; rare in Turonian to Santonian strata.

BATHYMETRY: Predominently bathyal, rare in upper abyssal flysch-type assemblages. Not found in deep abyssal assemblages from pelagic substrates.

REMARKS: As the type species of the genus, Rzehakina epigona serves as the model for the whole group of Late Cretaceous to early Paleogene rzehakinids. Since 1895 when Rzehak first published the description of Silicina epigona, a number of authors have proposed new species that are either synonymous with Rzehakina epigona, or are closely allied with it (Table 1). The majority of these species has been described from the Carpathian flysch deposits in Poland (Grzybowski, 1989, 1901; Jurkiewicz, 1967), but additional species have been described from Trinidad (Cushman & Jarvis, 1928; Cushman & Renz, 1946); northern Italy (Montanaro-Gallitelli, 1955), and the Soviet Far East (Serova et al., 1980; Kalishevich et al., 1981). The current status of these species is given in Table 1.


Table 31-1. Current status of species here regarded as belonging to Rzehakina.
SpeciesAuthorType level/Type localityComments
Silicina epigonaRzehak, 1895Zdounky, Czech RepublicRzehak's type collection no longer exists
Agathammina dubiaGrzybowski, 1896Campanian red clays, Subsilesian Unit, Wadowice PolandRegarded by Kaminski & Geroch (1993) as a junior synonym of R. epigona
Spiroloculina complanataGrzybowski, 1901Reported from the Inoceramus beds in a well from Bartne, Magura Unit near Gorlice, PolandNo specimens preserved in the Grzybowski Collection. Regarded as a possible senior synonym to R. minima, pending revision
Spiroloculina fissistomataGrzybowski, 1901Reported from wells in the Magura Unit, near Gorlice PolandNeotype was designated by Kaminski & Geroch (1993)
Spiroloculina inclusaGrzybowski, 1901An outcrop of the Inoceramus beds in Siary, Magura Unit near Gorlice PolandA lectotype was designated by Kaminski & Geroch (1993).
Spiroloculina occultaGrzybowski, 1901Reported from a well in Ropica Górna, Magura Unit, near Gorlice PolandType specimen re-illustrated by Kaminski & Geroch, 1993
Spiroloculina simplexGrzybowski, 1901Reported from the Inoceramus beds in Bartne and Przegonina, Magura Unit, near Gorlice, PolandNo specimens are preserved in the Grzybowski Collection. Regarded as nomen dubium
Miliolina tenuisFriedberg, 1901Reported from the Inoceramus beds in Stobiernia, Poland; Skole Unit of the CarpathiansDescribed based on a single specimen (probably R. epigona). The species was regarded as nomen dubium by Kaminski et al. (1993)
Spiroloculina waageniLiebus & Schubert, 1903Campanian-Maastrichtian Puchov Marls of SlovakiaA suspected synonym of R. epigona. The Schubert collection no longer exists.
Rzehakina epigona var. lataCushman & Jarvis, 1928Paleocene, Lizard Springs, TrinidadAmple material from the type locality is preserved in the Cushman Collection
Rzehakina epigona var. minimaCushman & Renz, 1946Paleocene, Lizard Springs, TrinidadAmple material from the type locality is preserved in the Cushman Collection
Rzehakina spiroloculinoidesMontanaro-Gallitelli, 1955Campanian to Maastrichtian, fucoid marls near Serramazzoni, ItalyCharacterised by its elongated biconcave test, and few chambers. Two type specimens are preserved in the author's collection at the University of Modena, Italy
Rzehakina sogabeiFukuta, 1957Campanian, Rumoi Coal field, Hokkaido, JapanCharacterised by its flat, strongly asymmetrical test.
Rzehakina uryuensisFukuta, 1957Campanian, Rumoi Coal field, Sorachi Province, Hokkaido, JapanCharacterised by its flat, symmetrical test. Only forms known from marginal marine environments.
Rzehakina fissistomata asimetricaJurkiewicz, 1967Paleocene Czarnorzeki Shales, Silesian Unit, near Krosno PolandNow regarded to be an aberrant specimen of R. fissistomata
Rzehakina kakyineicaSerova, 1980Paleocene Ivtygiinska Formation, Koryakskoye Mtns, N. KamchatkaCharacterised by its evolute coiling and large angle of translation between whorls
Rzehakina sakhalinicaSerova, 1981Lower Paleocene, Sinegorka horizon, Sakhalin IslandA suspected synonym of R. fissistomata
Rzehakina macilentaTurenko, 1983L. Campanian- Maastrichtian, Lower Krasnoyarsk Member, Sakhalin IslandSimilar to R. fissistomata, but chambers are more evolute.


Rzehakina epigona is generally regarded to be a morphologically variable species. Several of the species of Rzehakina described subsequently (Table 1) have been regarded as junior synonyms of R. epigona by various authors. A number of authors have regarded some of these forms (e.g., R. fissistomata, R. inclusa, R. lata, R. mimima) as subspecies of R. epigona (e.g., Cushman & Jarvis, 1928; Geroch, 1960; Jurkiewicz, 1967; Hiltermann, 1974; Serova, 1987).
Hiltermann (1974) compared the morphology of over 150 specimens of R. epigona from Ecuador, Austria and Poland, and discussed 22 quantitative and qualitative parameters that can be used for studies of morphological variability of the Rzehakina group. Among these, the newly introduced involution value ("Involutionswert") abbreviated "Z" was most valuable. This variable expresses the degree of embracing of the older part of the test by the last two chambers, or the relative width of central area respectively. Hiltermann compiled distributional data from the literature, and measured specimens figured by earlier authors from original figures. Based on this morphometrical data, Hiltermann distiguished five different forms (epigona, fissistomata, inclusa, minima and bowsheri) which he regarded to be subspecies of Rzehakina epigona The Caribbean species R. epigona lata of Cushman & Jarvis was considered to fall within the range of variability of R. epigona epigona. Hiltermann demonstrated that the five subspecies can be ranked to form a continuous series in terms of increasing "Z" values, although other morphological parameters such as the L/B index partially overlap. However, the stratigraphic ranges of these five forms are partially disjunct, with R. epigona (sensu stricto) possessing the longest range. While these five forms are no doubt closely related, most authors now consider them as separate species.
The term Rzehakina epigona is used here for those forms with a deeply excavate umbilical region and a poorly developed or missing coil suture (=R. epigona epigona of Hiltermann). In these forms, each successive chamber moderately overlaps the chambers of preceeding whorl. Hiltermann considered Spiroloculina occulta Grzybowski, 1901 to be synonymous with R. epigona, a view confirmed by a re-study of the type material (Kaminski & Geroch, 1993). We also regard Spiroloculina waageni Liebus & Schubert, 1903 to be fully synonymous with R. epigona. The type locality of S. waageni is within the Pieniny Klippen Belt in Slovakia, and consists of reddish marls of Campanian-Maastrichtian age (the Gbelany Member of the Puchov Marls). The assemblage described by Liebus & Schubert contains a bathyal benthic foraminiferal assemblage with Reussella szajnochae (Grzybowski) and Contusotruncana. A comparison of biometric parameters (length/breadth index and involution index sensu Hiltermann) of the figured specimens of both species reveals that the type specimens were nearly identical. Unfortunately, the Schubert collection no longer exists.
The species Rzehakina inclusa (Grzybowski) differs from R. epigona in being more involute, and in having an umbilical plug that obscures all but the final two chambers of the test. As a result, the test of R. inclusa is more biconvex. The species R. fissistomata (Grzybowski) is more evolute than R. epigona, and has a well-developed coil suture, while Rzehakina lata Cushman & Jarvis is broader, more involute, and has a thicker outer whorl. Rzehakina minima Cushman & Renz is smaller, more evolute, and thinner than R. epigona (see the remarks for these species for further diffferences).

ILLUSTRATIONS: Plate 31 - Rzehakina epigona (Rzehak).
Topotype specimens of Rzehakina epigona from Zdounky, Czech Republic. SEM and light microscope images. 1a, 2a. SEM images; 1b. detail of aperture (SEM); 1c, 2b, 3a, 4a. reflected light in immersion; 1d, 2c, 3b, 4b. transmitted light in immersion.