«Coniacian and Santonian inoceramid bivalves from the Gosau-Group (Cretaceous, Austria) and their biostratigraphic and palaeobiogeographic ...»
The term Schloenbachi-Xont should be preserved for reasons of stability in the stratigraphical terminology. CECH (handwritten label) identified NHMW/1989/51/2 as Inoceramus (Cremnoceramus) schloenbachi J. BÖHM.
S t r a t i g r a p h i e d i s t r i b u t i o n : Inoceramus crassus PETRASCHECK is an index species of the Lower Coniacian. It is absent or very rare in the basal Coniacian.
Geographic d i s t r i b u t i o n : Europe, N-America, Western Asia.
Cremnoceramus ernsti 1928) (HEINZ, (PI. 1, Fig. 6) * 1911 Inoceramus Lamarcki PARK. - WOODS: 307-327, text-fig. 85.
1928a Inoceramus ernsti n.sp. - HEINZ: 73-74.
v. 1967 Inoceramus ernsti HEINZ - TRÖGER: 128-130, pi. 14, figs. 1-6.
1992 Cremnoceramus ernsti HEINZ, 1928 - WALASZCZYK: 55, text-fig. 18, pi. 32, figs. 1-3 (with synonymy).
M a t e r i a l : One specimen NHMW/1989/51/3 from the tunnel section N of Bad Ischi.
D e s c r i p t i o n : The described specimen is a flattened internal mould of the umbonal region of a right valve. Large parts of the auricle and the ventral margin are missing. The anterior margin (Vo; PI. 1, Fig. 6) is steeply inclined inwards and slightly bent. The stout beak does not extend beyond the auricle and is slightly curved towards the anterior margin.
TRÖGER & SUMMESBERGER: Coniacian and Santonian inoceramid bivalves 169 Obtainable H/L-ratios are between 85-90%, the Vo/L-ratios between 45-55%. GW is presumed to be greater than 90°. The beak is smooth until H = 23 mm, followed by costellatuslike undulations (9.2 mm, 9.0 mm, 13.5 mm, 8.5 mm). All indices lie within the variation of Inoceramus (Cremnoceramus) ernsti HEINZ (see TRÖGER 1967: 41).
R e m a r k s : The description of the species (HEINZ 1928: 73, 74) is based only upon textfigure 85 of WOODS (1911) which represents a specimen of unknown origin.
S t r a t i g r a p h i e d i s t r i b u t i o n : The vertical and geographic distribution of Cremnoceramus ernsti is identical to C. crassus (PETRASCHECK).
Cremnoceramus sp. aff. deformis MEEK, 1877 (PL 1, Fig. 7,7a) v.* 1877 Inoceramus deformis MEEK: 146-148, pi. 14,fig.4.
v. 1992 Cremnoceramus deformis (MEEK) - WALASZCZYK: 52-53, text-fig. 17, pi. 29,fig.4; pi. 30,fig.4. (with additional synonymy).
M a t e r i a l : 2 specimens. MA (unregistered) is an internal mould of a right valve, NHMW/1989/51/4a of a left one. Tunnel section N of Bad Ischi.
D e s c r i p t i o n : Both individuals have large parts of the auricle and the whole ventral margin missing. The umbonal region of NHMW/1989/5 l/4a protrudes obliquely over the anterior margin. The specimen from the MA collection is flattened with distinct radial cracks. Adherent shell remains are up to 6.5 mm thick. NHMW/1989/5 l/4a additionally has parts of the ligament ridge preserved (PL 1, fig. 7). Both individuals are elongate. In MA (unregistered) Na/Ha lies between 100 and 88% and Vo/Ha between 34 and 56 % at Ha 50 mm. Conspicuous in both individuals is the increasing undulation interval from 4.5-5.5 mm to more than 35 mm in the preserved ventral region.
R e m a r k s : Concerning the overall shape and the undulation intervals, both individuals differ considerably from the holotype of Cremnoceramus deformis (MEEK) (a cast has been studied). On the holotype the undulations are closer together at equal distance from the umbonal pole than on the Gosau specimens. The same is also true for the specimens of Cremnoceramus deformis (MEEK), figured by WALASZCZYK (1992: textfig. 17). The specimen figured by HEINZ (1928 a: pi. 2, fig. 1) differs from the holotype but is similar to the specimens from the Gosau. CECH (handwritten label) associated NHMW/1989/51/4a with the /. deformis-growp.
S t r a t i g r a p h i e d i s t r i b u t i o n : Cremnoceramus deformis (MEEK) occurs frequently in strata of Early Coniacian age. Specimens with differing undulation intervals are characteristic of the middle and higher part of the Lower Coniacian Schloenbachi-Zone of the NW German and Polish Cretaceous basin (HEINZ 1928 a: pl.3; TRÖGER 1974: 115, 116).
Geographic d i s t r i b u t i o n : N-America, Europe, Western Asia.
* 1888 Inoceramus (Volviceramus) Koeneni G.MÜLLER: 412-413, pi. 17,fig.1.
v. 1969 Inoceramus koeneni G. MÜLLER - TRÖGER: 68-81, pi. 1, figs. 1-6; pl.2, figs. 1-5; text-figs. 1-8.
170 Annalen des Naturhistorischen Museums in Wien 96 A M a t e r i a l : Two bivalved specimens (MA unregistered, NHMW/1989/51/6) from the tunnel section N of Bad Ischi and a single left and two isolated right valves (NHMW/1989/50/4, 11) from Strobl/Weißenbachtal, 30 m E of the Schmolnauer Alpe.
D e s c r i p t i o n : All specimens are internal moulds with adherent shell remains. Parts of the auricles and the ventral margins and large parts of the ligament ridge are generally missing. The beaks are slightly involute and turned towards the anterior margin. The tapering beak of the left valve of this inequivalved species is visible (PL 2, fig. 2). Both valves are very strongly inflated. The umbonal region is damaged by flattening in some specimens (e.g.
NHMW/1989/51/6). Superimposed shell fragments render measurement of these specimens pointless. Even the data of the better ones, NHMW/1989/50/4 and MA (unregistered; the original of pi. 2, fig. 2) are more or less changed by compaction. Obtainable NA/Ha-ratios are between 60 and 91% in right valves, between 65-85% in left ones.
Tab. 3. Comparison of undulation intervals (DU) of specimens from the Subhercynian Cretaceous basin (SCB) and from the Gosau-group (GG).
R e m a r k s : The NA/Ha-ratios of the Gosau specimens are within the variation range of Volviceramus koeneni (G. MÜLLER) from the Middle Coniacian of the type locality Steinholz (NW Quedlinburg) in the Subhercynian Cretaceous basin.
The same is the case of the average undulation intervals (DU) in 30-50 mm and 50-70 mm distance from the umbonal pole (tab. 3). Taking the considerable deformation into account, the total angle (Gw) also has comparable values: 115-165° in the SCB (complete variability of undeformed specimens), 110° (crushed) and 125° (not deformed) in the Gosau. Radial grooves between undulations (pi. 2, fig. 2) occur in specimens from both areas. The shell thickness in different parts of the valves is also comparable.
S t r a t i g r a p h i e o c c u r r e n c e : Volviceramus koeneni (G. MÜLLER) occurs frequently together with different species of Peroniceras and with Scaphites kieslingswaldensis LANGENHAN & GRUNDEY in the Middle Coniacian. Together with inoceramids of the Magadiceramus subquadratus-group it occurs through the Volviceramus involutus-Zone to the base of the Upper Coniacian.
G e o g r a p h i c d i s t r i b u t i o n : N-America, Europe, Western Asia, N-Africa.
Volviceramus involutes (J. de C. SOWERBY, 1828) (PI. 2, fig. 5, aff.: fig. 4) * 1828 Inoceramus involutus J.de C. SOWERBY: 160-161, pi. 583, figs. 1-3.
1992 Volviceramus involutus (SOWERBY, 1828) - WALASZCZYK: 5, pi. 37, fig. 5 (with additional synonymy).
M a t e r i a l : Two right and several fragments of left valves. (NHMW/1994/238), BAF/Tr/1993/Go.l) from the Stöcklwaldgraben (Rußbach). One bivalved specimen (MA unregistered) from the ditch close to Paß Gschütt is tentatively assigned to Volviceramus sp.
aff. involutus SOWERBY.
TRÖGER & SUMMESBERGER: Coniacian and Santonian inoceramid bivalves 171 D e s c r i p t i o n : All specimens are strongly flattened internal moulds, mostly with adherent shell fragments. The type of flattening indicates originally strongly inflated shells with especially thin umbonal regions. Inflation of left valves must have been even more pronounced than characteristic for involute inoceramids. The narrowly rounded beak is visible.
Shell surface is ornamented by growth striae only. Shell thickness increases towards the ventral margin (6 mm). The reason for the assignment of the specimen from the Paß Gschütt area to the V. involutus-group is the particularly narrowly rounded beaks on both valves.
Stratigraphie distribution: Volviceramus involutus (SOWERBY) occurs in the Middle and basal Upper Coniacian (N-America, Europe, Western Asia). The acme is above that of Volviceramus koeneni (G. MÜLLER).
Geographic d i s t r i b u t i o n : world-wide.
(PI. 2, figs. 7, 8) 1872 Inoceramus Mantelli de MERCEY: 21.
* 1877 Inoceramus Mantelli de MERCEY: 324, pi. 1, 2.
1878 Inoceramus Mantelli de MERCEY - BARROIS: 478.
1879 Inoceramus Mantelli de MERCEY; BARROIS: 454, pi. 54, figs. 1, 2.
1962 Inoceramus (Platyceramus) mantelli MERCEY (BARROIS) - SEITZ: 355-363, text-figs. 1, 3, 4; pi. 10, pi.
11, figs. 1,2, 6; pi. 12,figs.3.
1990 Inoceramus (Platyceramus) mantelli de MERCEY - NODA & TOSHIMITSU: 485-512, 16 figs.
R e m a r k s : Reinterpretations were given by SEITZ (1962) and NODA & TOSHIMITSU (1990).
M a t e r i a l : Two internal moulds of left valves preserved partially with shell from Nussenseebach (NHMW/1994/239) and from the tunnel section N of Bad Ischi (NHMW/1989/51/1).
D e s c r i p t i o n : Both specimens are incomplete, parts of the auricle and the ventral margin are missing. Radial cracks (PI. 2, fig. 7, 8) indicate slight flattening. The geniculated anterior margin slopes towards the commmissure. The existence of an anterior auricle is indicated in NHMW/1989/51/1.
Tab. 4. Averages of the Na/Ha-,Vo/Ha and S/Ha indices with increasing distance from the umbonal pole (UP). 1:
NHMW/1994/239, 2: NHMW/1989/51/1.
Generally the undulations equal those figured by SEITZ (1962: fig. 4). They are evenly rounded to wavelike. The distance between the undulations becomes narrower towards the ventral margin. Gw in the juvenile stage is from 96 to 100°. WA increases in NHMW/1994/239 from 28° in the umbonal region to the maximum of 65°. This is in accordance with the lectotye of Platyceramus mantelli mantelli (MERCEY). Thé pointed beaks are 172 Annalen des Naturhistorischen Museums in Wien 96 A slightly bent towards the anterior margin (Vo) and do not project over the auricle. The ligament ridge of NHMW/1989/51/1 measures 3.5 x 2.5 mm below the beak.
S t r a t i g r a p h i e d i s t r i b u t i o n : Platyceramus mantelli (de MERCEY) occurs from basal Lower Coniacian to basal Upper Coniacian (SEITZ: 1962: 370, fig. 6) in Western Europe (P. mantelli mantelli especially Middle Coniacian; TRÖGER 1974: tab. 3).
Geographic d i s t r i b u t i o n : Western and Middle Europe.
Platyceramus mantelli beyenburgi 1965) (SEITZ, (PI. 3, fig. 1, la) 1929 Inoceramus circulons SCHLÜTER var. oblonga n.v. - HEINE: 54.
1962 Inoceramus mantelli angustus n.nom. SEITZ: 367-370, pi. 12, figs. 2, 5, 7; pi. 13, fig. 1.
1965 Inoceramus mantelli beyenburgi n.nom. SEITZ: 96, footnote.
M a t e r i a l : NHMW/1989/50/6, a fragment of an internal mould from Strobl/ Weißenbachtal, 30 m E of the Schmolnauer Alpe.
D e s c r i p t i o n : The umbonal region of a left valve is preserved with adherent shell fragments. The fragment is diagenetically flattened and the anterior margin deformed. Gw. of the juvenile is 105°. Undulations are elongatedly ellipsoidal.
Tab. 5. Na/Ha-, Vo/Ha- and S/Ha-ratios of Platyceramus mantelli beyenburgi (SEITZ); (NHMW/1989/50/6).
The acute beak projects a little over the auricle and is bent slightly towards the anterior margin. WA is 50-68° and the Na/Ha-ratio is identical with the data given by SEITZ (1962: 367).
R e m a r k s : The specimen was identified by £ECH (handwritten label) as Inoceramus (Platyceramus) mantelli angustus SEITZ.
Stratigraphie d i s t r i b u t i o n : Platyceramus mantelli beyenburgi (SEITZ) occurs from basal Lower Coniacian to basal Upper Coniacian (Western Europe).
Platyceramus mantelli cf. subrhenanus (SEITZ, 1962) (PI. 2, fig. 9) * 1962 Inoceramus mantelli subrhenanus n. subsp. SEITZ: 366-367, pi. 11,figs.3, 4; pi. 12, fig. 1.
M a t e r i a l : NHMW/1989/50/1: a fragmentary internal mould of a right valve from Strobl/Weißenbachtal, 30 m E of the Schmolnauer Alpe.
D e s c r i p t i o n : Only the umbonal area is preserved. The steeply inwards sloping and compressed anterior margin indicates diagenetic crushing. The prominent and tapering beak turns towards the anterior margin and is shifted partially over the auricle. An anterior auricle is present on the specimen studied. Gw. is 120° in the umbonal area. The Na/Ha-ratio increases between UP and Ha 55 mm from 47 to 69%, the Vo/Ha-ratio from 21 to 38% and TRÖGER & SUMMESBERGER: Coniacian and Santonian inoceramid bivalves WA from 40 to 65°. Apparently due to deformation, the course of the undulations is pentagonally rounded.
R e m a r k s : The prominent and tapering beak and the elongate pentagonal undulations (originally possibly oval) indicate Inoceramus (Platyceramus) mantelli subrhenanus SEITZ.
The circular ribbing typical of the gerontic stage of the subspecies cannot be observed due to the poor state of preservation of the specimen. This is the reason for the use of open nomenclature here.
S t r a t i g r a p h i e d i s t r i b u t i o n : The subspecies is described from the Middle Coniacian (SEITZ 1962: 366) of Western Europe.
Platyceramus cycloides ahsenensis 1961) (SEITZ, (Text-fig. 3) 1931 Inoceramus cycloides WEGNER var. quadrata n. var. - RIEDEL: 662, pi. 74, fig. 4.
1961 Inoceramus (Platyceramus) cycloides ahsenensis n.nom. - SEITZ: 63-63, pi. 1,figs.3, 7, 9, 10; textfigs. 12, 13.
M a t e r i a l : Internal moulds of a right (NHMW/1994/242) and a left valve (BAF/Tr/1993/Go.2) collected by the authors in 1993. Grabenbach/ Gosau.