Multivariate discrimination of Buryella species from the Lower Eocene of the Outer Flysch Carpathians, Poland

Variegated shales in the Lower Eocene hemipelagic deposits of the Subsilesian Series, Polish part of the Western Carpathians, have yielded rich radiolarians with common representatives of the genus Buryella. Two new radiolarian species, Buryella spina sp. nov. and Buryella hannae sp. nov., are described, and two other species have been recognized: Buryella tetradica Foreman and Buryella clinata Foreman. Specimens have been measured, grouped and interpreted using cluster analysis, principal component analysis (PCA) and canonical variates analysis (CVA). Species attributed to Buryella have three or four segments, a fusiform or lobate outline, and a constricted, rather than flared, aperture. The cephalis always possesses an apical horn of varying length with a distinct vertical pore at the collar stricture. All specimens possess a pronounced vertical tube, rounded or elongate, that might extend to the base of apical horn. Near the base of the cephalis the parallel ridges observed on the external wall of the cephalis are ridges from the horn that diverge and extend to the collar stricture except ventrally, where two ridges rejoin to enclose the vertical pore and form an upwardly directed tube. These structure might be evidence of the presence of arches (A-Vbl, A-Vbr) and bars (Vbl, Vbr), which form the vertical tube.


INTRODUCTION
The genus Buryella was first erected by Foreman (1973) and included in the family Theoperidae based on material from the Gulf of Mexico (DSDP, Leg 10). Foreman described three new species of Buryella and proposed a new Buryella clinata Zone, the base of which is defined by the earliest evolutionary appearance of B. clinata.
The present paper evaluates diversification of Buryella in the Carpathians in comparison with representatives described from low latitude localities. Two new radiolarian species, Buryella spina sp. nov. and Buryella hannae sp. nov., are also described. The taxa discussed herein occur in a rich and diverse Lower Eocene radiolarian assemblage within the Subsilesian Series of the Outer Carpathians. All the original siliceous skeletons are replaced by pyrite framboids, resulting in exceptional preservation of external, morphological features (for explanation of the pyritization processes, see Bak & Sawlowicz, 2000).
A qualitative approach to buryellid systematics has been used, using detailed measurements and statistics. Additionally, recent studies of the genus Buryella (O'Connor, 1997(O'Connor, , 2001 have been referred to, which include a new genus diagnosis, as well as the inclusion of Buryella into the family Artostrobiidae. The complexities of the phylogenetics of the Lower Eocene members of the genus from the Carpathians are also discussed. and Pacific (e.g., Andrusov, 1959;Winkler, 1983;Stefanescu & Micu, 1987;Moullade et al., 1988;Kuhnt & Kaminski, 1990;Bak, 2000).
The Subsilesian unit crops out in the Polish part of the Western Carpathians in two parallel zones. The northern zone is located to the north of the Silesian Nappe, while the southern zone crops out in a few tectonic windows (Fig. 1).
The study area is one of a series of exposures in the axial zone of the Wisniowa tectonic window east of Myslenice. These Subsilesian deposits were folded and form two tectonic slices. Though they crop out in isolated exposures, Late Cretaceous through Palaeogene deposits have been mapped.
Lithostratigraphic units have been defined following Burtan (1974Burtan ( , 1978 and Cieszkowski et al. (2001): the 'Weglówka-type marls' are Senonian in age, whilst the Czerwin Sandstone, the Green Shales and the Variegated Shales are Palaeogene in age.

Radiolarian assemblage
The material used in this study was collected for foraminifera originally by Waskowska-Oliwa (University of Science and Technology, Kraków, Poland). Radiolarians were extracted by washing fine residue left over from that previous study through a 63 µm sieve.
Type specimens are currently housed in the author's collection (Institute of Geological Sciences, Jagiellonian University), collection reference is ING-EE-II. Scanning electron micrographs were prepared using a HITACHI S-4700 SEM.
Generally, radiolarians are present throughout the Variegated Shales, but common, well-preserved specimens occur rarely. These well-preserved radiolarian skeletons have occurred due to pyritization, which can result in exceptional replacement of original siliceous skeletons by pyrite framboids. Although this process has preserved the external skeletal features, inner structures remain obscured or damaged by the pyritization process.
The radiolarian assemblage contains common Buryella, especially B. clinata Foreman and B. tetradica Foreman s.s., which together make up 9% of the total assemblage. Other common species include Calocycloma ampulla (Ehrenberg) Kozlova).

Biostratigraphy and age
The biostratigraphic age determination is based on the presence of radiolarian taxa widely distributed in the low-latitude Lower Eocene, such as Phormocyrtis striata striata Brandt, Lychnocanium bellum Clark & Campbell, Thyrsocyrtis rhizodon Ehrenberg, Theocotylissa ficus (Ehrenberg) and other representatives of the Phormocyrtis striata striata Interval Zone (RP9) (Foreman, 1973;emend. Riedel & Sanfilippo, 1978). However, this radiolarian zonation which is defined for the tropics was found to be not fully applicable for dating and correlating the Carpathian material. Some species whose first and last occurrences define this zone in the tropics were either missing or have different ranges in the Subsilesian Series. For example, Lychnocanoma auxilla Foreman has its last occurrence  Zytko et al., 1988 -simplified). Black triangle indicates location of the outcrop. in the Subsilesian Series later than in the tropics; Theocotyle venezuelensis Riedel & Sanfilippo is present in the Subsilesian deposits, although its first appearance in the tropics is noted in the Theocotyle cryptocephala Zone (RP10). Buryella tetradica Foreman, has its last occurrence later in the Subsilesian Series. Species missing in the Subsilesian Series by comparison with the tropical faunas are: Theocorys anaclasta Riedel & Sanfilippo, the lowest occurrence of which defines the lower limit of the Phormocyrtis striata striata radiolarian Zone and Lamptonium fabaeforme constrictum Riedel & Sanfilippo and Podocyrtis (Lampterium) acalles Sanfilippo & Riedel, the first occurrences of which are approximately synchronous with the lower limit of the RP9 zone. The Lithocyclia ocellus group Ehrenberg is also missing here, although it is common to abundant in the Skole Series of the Western Polish Carpathians (Bak et al., 1997). Diachronous first and last occurrences, or the absence of some species in the Lower Eocene deposits of the Subsilesian Series result from many factors, including preservation, reworking, geographical distribution of species, and their dependence on oceanic water masses and currents.

Statistical analysis
From 120 specimens of Buryella, 40 of the best preserved complete skeletons were selected for scanning electron microscope investigation. Of these specimens, 28 were measured and grouped by statistical methods. The specimens illustrated and described by Foreman (1973Foreman ( , 1975 as Buryella clinata and Pterocodon(?) anteclinata were also measured and included into the dataset. The specimen parameters used in the calculations are presented in Table 1. A combination of cluster analysis, principal component analysis (PCA) and canonical variates analysis (CVA) was used for calculations. Statistical analyses were carried out on the original specimen dimensions (Table 1) using the software package PAST-Palaeontological Statistics, ver. 0.97, written by Ryan et al. (1995). Explanations of statistical techniques implemented there are presented in Harper (1999) and Hammer et al. (2001).

Remarks. The diagnosis emended by O'Connor
Genus Buryella Foreman, 1973, emend. O'Connor, 2001 Type species. Buryella tetradica Foreman, 1973. Species from the Lower Eocene of the Subsilesian Series attributed to Buryella have three or four segments, are fusiform or lobate in outline and have a constricted rather than flared aperture. The cephalis always possesses an apical horn of varying length with a distinct vertical pore at the collar stricture. Internal structures of cephalis are invisible because of pyritization. However, all specimens possess a pronounced vertical tube (e.g. Pl. 1, fig. 2), rounded or elongate, which may extend to the base of apical horn. Near the base of the cephalis are external longitudinal ridges that diverge from the horn and extend to the collar stricture. Ventrally, two of these ridges rejoin to enclose the vertical pore and form an upwardly directed tube. These structures might be evidence of the presence of arches (A-Vbl, A-Vbr) and bars (Vbl, Vbr), which form the vertical tube. Based on this feature, the species described herein is included in the genus Buryella, although the internal structures of the cephalis need further investigation to confirm the placement of these species in Buryella. Buryella tetradica Foreman, 1973 (Pl. 1, figs 1-3) 1973 Buryella tetradica Foreman: 433, pl. 8, figs 4, 5;pl. 9, figs 13, 14. 2001 Buryella tetradica Foreman;O'Connor: 11, pl. 1, figs 14-18;pl. 3, figs 16-21. Description. See Foreman (1973), Hollis (1997) and O'Connor (2001).
Stratigraphic range. This taxon is known from the Lower Eocene of the Carpathians, present within the Phormocyrtis striata striata Radiolarian Zone and Saccamminoides carpathicus Foraminiferal Zone. The first and the last occurrences of B. tetradica differ globally. Its first occurrence is known from the Upper Paleocene of the Gulf of Mexico, from the lower part of an unzoned interval (Foreman, 1973); from the Upper Paleocene of the Caspian and the middle Volga areas (Kozlova, 1983b(Kozlova, , 1993. It ranges from an unzoned interval to the Buryella clinata Radiolarian Zone in the Caribbean region (Riedel & Sanfilippo, 1973); from RP5b to RP10 zones in the Southwest Pacific (Hollis, 1997;O'Connor, 2001;Hollis et al., 2005). B. tetradica s.l. (Sanfilippo & Blome, 2001) is also known from RP6-RP10 zones in the western North Atlantic.
Remarks. Four-segmented, subovate test, with well-developed strict longitudinal and transverse alignment of abdominal pores and pronounced longitudinal ridges separate each row of pores observed on the specimens are features appearing in later members of this species. Another feature is the orientation of the vertical tube. As mentioned and illustrated by O'Connor (2001), the vertical tube is directed upwards at an angle in the early evolutionary members, whilst in Foreman's specimens and those herein the vertical tube is directed horizontally or almost horizontally. Specimens found in the Subsilesian Series match the original description of Foreman (1973). In comparison with the specimens of Sanfilippo & Blome (2001), they correspond to B. tetradica s.s. rather than to B. tetradica var. A, which also appeared stratigraphically earlier. It differs from B. tetradica tetradica, B. tetradica tridicaas presented by Hollis (2002) and B. tetradica described by O'Connor (2001) and Hollis (1997) in having a much more elongated and oval post-thoracic test. Foreman, 1973 (Pl. 1, figs 4-10, 16) 1973 Buryella clinata Foreman: 433, pl. 8, figs 1-3; pl. 9, fig. 19.
Stratigraphic range. This species has been hitherto recorded in the Carpathians from the Lower Eocene. It is present in the Buryella clinata through the Phormocyrtis striata striata Radiolarian Zones (Bak et al., 1997;Rajchel et al., 1999;Rajchel & Barwicz-Piskorz, 2005;Bak & Barwicz-Piskorz, 2005). B. clinata is found in the Lower to lowest Middle Eocene from tropical localities. Its evolutionary transition from Pterocodon (?) anteclinata marks the base of the B. clinata Zone. It becomes extinct at approximately the lower limit of the Theocotyle cryptocephala Zone (Foreman, 1973;Sanfilippo & Nigrini, 1998, 2001. (2001), during his examination of the genus Buryella, excluded B. clinata from the genus, as it needs more elucidation of the internal structures. Although B. clinata is commonly present in the Carpathians there is no sufficiently well-preserved specimens for internal investigation.

Remarks. The problem of placing B. clinata into the Family Artostrobiidae remains open because O'Connor
Specimens measured herein as B. clinata represent groups 1 and 2 on the dendrogram (Fig. 3) and the PCA and CVA graphs (Figs 4,5). The Carpathian specimens (Group 1) are slightly different from the forms described by Foreman (1975) (Group 2). Both groups include forms having four-segmented tests, a bladed apical horn with bases as wide as the cephalis. However, Foreman's specimens are more elongated in the thorax and the abdominal width, while the Carpathian specimens are more inflated and the arrangement of pores on the thorax is disrupted in some places by areas of non-porous wall. This may be a consequence of very strongly developed ridges extending from the apical horn. The fourth segment is inversely truncated being conical, but very short in the specimens herein, having only one or two transverse rows of pores. This taxon is included in the genus Buryella on the presence of the external skeletal features, especially the pronounced vertical tube directed proximally at an angle (as discussed above).
Buryella hannae sp. nov. (Pl. 1,17) Derivation of name. In honour of Prof. Hanna Górka for her significant contributions to radiolarian studies in Poland.
Description. Tri-segmented test. Cephalis hemispheroidal, with very few circular pores, bearing a thick, bladed apical horn, almost equal to the length of the thorax. Weak cephalic ridges, starting distally and continuing on the external wall of the cephalis. Vertical tube at posterior base of cephalis, expressed as a low, truncated cone. Thorax truncate-conical, with circular to sub-circular pores, quincuncial to randomly arranged in three to four transverse rows. Abdomen inflated cylindrical, slightly longer than the thorax. Stricture between the thorax and abdomen is externally visible as a change of outline. Abdominal pores circular, quincuncially arranged in five to six rows, termination ragged. Buryella sp. C, as described by Dumitrica (1973), differ from B. spina which has a long, and more massive, bladed apical horn, and a truncated-conical rather than an inflated thorax.

CONCLUSIONS
Well-preserved, pyritized radiolarian assemblages from the Lower Eocene deposits of the Subsilesian Series (Polish part of the Outer Flysch Carpathians) have yielded common specimens of the genus Buryella. The pyritization process, preserved the external radiolarian skeletons exceptionally well; however, subsequent pyrite framboid crystallization has destroyed any internal structures. Two new species of the genus Buryella have been described based on the material investigated. However, it should be stressed that their description is based on external skeletal morphology, with only the tracing of external cephalic features to indicate the presence of internal arches and bars. It was not possible to observe any internal structures due to pyritization. Additionally, the problem of placing Buryella clinata into the Family Artostrobiidae remains open, as stated by O'Connor (2001), subsequent to further studies of internal skeletal structures.
Despite the absence of Pterocodon (?) anteclinata or any ancestral material of B. clinata, and the unclear position of the internal skeletal structures, some phylogenetic connections have been inferred, based on specimen morphology and external measurements. The newly described species are probably local Carpathian variants of low-latitude representatives of the genus Buryella, which has been useful in the southern high-latitude radiolarian biostratigraphy of the Palaeogene (Hollis, 1993(Hollis, , 1997(Hollis, , 2002O'Connor, 2001), as well in the Boreal realm (Kozlova, 1983a(Kozlova, , b, 1984(Kozlova, , 1993(Kozlova, , 1999. B. hannae appears to be an offshoot of B. clinata Foreman developed by the loss of the distal segment, with a weaker grid of ridges on the external abdomen wall. However, the non-porous areas on the thorax wall may be the distal remnants of strongly developed apical horn ridges. B. spina appears to be an offshoot of B. clinata through a similar loss of the distal segment. The phylogenetic relationships of the Carpathian species with the forms of B. clinata, as described by Foreman, and its ancestor Pterocodon (?) anteclinata, as suggested by Foreman (1975), cannot be discussed here without reference to the internal cephalic structure. The application of simple statistical methods has shown close similarity between the Carpathian B. clinata and Pterocodon (?) anteclinata and suggests that the