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Muderongia endovata
Muderongia endovata Riding et al., 2001, p.24–26,28, pl.1, figs.1–2; text-fig.3.
Holotype: Riding et al., 2001, pl.1, fig.1; text-fig.3.
Age: Valanginian.
Original description (Riding et al., 2001):
Muderongia endovata sp. nov. Plate 1, figs. 1, 2; Text-Figure 3 Muderongia simplex, Alberti, 1961, p. 12, pi. 2, fig. 6, pi. 12, fig. 1 (non. pi. 2, figs. 1,2,4,5, pi. 12, fig. 2); Millioud, 1967, pi. 2, fig. 16; Brideaux, 1976, pi. 44.2, fig. 1; Duxbury, 1977, p. 55, pi. 14, fig. 9; Harris, 1977, pi. 20, fig. 6; Duxbury, 1978, pi. 3, fig. 2; Raynaud, 1978, pi. 1, fig. 8; Thusu, 1978, pi. 2, fig. 4; Ashraf, 1979, p. 136, pi. 6, fig. 10; Davey, 1979, pi. 2, figs. 7-8; Piasecki, 1979, fig. 15; Dorhofer and Davies, 1980, figs. 34D, 36C-G; Morgan, 1980, pi. 19, figs. 7-10; Williams and Bujak, 1980, pi. 5, figs. 2,4; Below, 1981, pi. 1, fig. 6; Woollam and Riding, 1983, pi. 8, figs. 7-8; Thusu and Van der Eem, 1985, pi. 53, fig. 4; Williams and Bujak, 1985, textfig. 33.16; Aarhus et al., 1986, fig. lOo; Davey, 1987, pi. 5, fig. 14; Habib and Drugg, 1987, pi. 4, fig. 1; Heilmann-Clausen, 1987, pi. 1, figs. 9-10; Thusu et al., 1988, pi. 29, figs.8,9;?Barron, 1989, pi. 2, figs. 8,9; Colin etal., 1992, pi. 4, figs. 11,12; Costa and Davey, 1992, pi. 3.2, fig. 4; Poulsen, 1996, pp. 57, 58, pi. 23, fig. 5.
Muderongia simplex Alberti, 1961, p. 12, pi. 2, fig. 6, pi. 12, fig. 1 (non. pi. 2, figs. 1, 2, 4, 5, pi. 12, fig. 2) subsp. simplex (autonym, now redundant); Schi0ler, 1992, pi. 9, fig. 5.
Muderongia sp. cf. M. simplex Alberti, 1961, p. 12, pi. 2, figs. 1,6, pl.12, fig. 2 (non. pi. 2, figs. 2,4, pi. 12, fig. 2); Mclntyre and Brideaux, 1980, pi. 12, fig. 4.
Muderongia sp. cf. M. mcwhaeli Cookson & Eisenack 1958, p. 41, pi. 6, figs. 1-5; Wiseman, 1980, pi. 1, fig. 3.
Derivation of Name. The specific epithet refers to the ovoidal shape of the endocyst.
Diagnosis. A species of Muderongia, the thin periphragm of which forms one apical horn, two equatorial/lateral horns and one antapical horn giving a typical rhomboid to rounded subpentagonal ceratioid amb. The area of the periphragm in the right antapical area, close to the 5"/6"' parasuture, forms a prominent shoulder or protrusion which is a reduced or incipient right antapical horn. The left antapical horn is close to the lp/1"" parasuture and is the longest and most prominent. The horns are subconical, tapering distally and with rounded, closed terminations. The equatorial/lateral horns, however, may be subrhombic with a medial concavity at the distal extremities at the position of the paracingulum. The equatorial/lateral horns are frequently longer posterior to the position of the paracingulum and may point slightly in an antapical direction. The endocyst is ovoidal to longitudinally elongate subspherical; it may have a small antapical boss. The ovoidal/subspherical endocyst engenders a circumcavate cyst organisation. Periphragm continuous, thin, smooth to microscabrate; endophragm continuous, relatively thick, smooth, scabrate or microgranulate. Archeopyle apical, type (4A). Paratabulation corniform gonyaulacacean, indicated, sometimes partially, by low, smooth, discontinuous ridges on the periphragm. Paracingulum indicated by low ridges on the periphragm and frequently a medial concavity on the equatorial/lateral horns. Parasulcus indicated by low ridges on the periphragm and the parasulcal notch, offset to the left.
Holotype. Specimen MPK 1275, Housed in the palynological collections of the British Geological Survey, Keyworth, Nottingham, UK.
Locality and Horizon. Haldager No. 1 Borehole, Denmark (Davey, 1979, text-fig, lb), core depth 863.19m- 866.24m.
Paratype. Specimen figured as Muderongia simplex Alberti, 1961 (pi. 2, fig. 6). Housed in the palynological collections of the Bundesanstalt fur Geowissenschaften und Rohstoffe Aussenstelle, Berlin, Germany.
Locality and Horizon. The Valanginian of the Dabendorf Borehole, Germany (slide 2a/Dl of Alberti, 1961).
Dimensions. The holotype measures 104.5 µm in overall length and 75.5 µm in overall width; the endocyst is 64.5 µm long and 55.5 µm wide. The paratype is 118.0 µm in overall length and 92.5 µum in overall width; the endocyst measures 76.0 µm in length and 72.5 µm in width.
Assemblage of 35 specimens measured (µm, Min.(Mean)Max.)
Overall cyst length (incl. operculum): 98.5(107.5)118.5
Overall cyst width: 63.5(69.5)78.0
Endocyst length (incl. operculum): 62.5(66.0)71.5
Endocyst width: 50.5(56.5)63.5
Remarks. The periphragm of Muderongia endovata sp. nov. is normally psilate and the pericoel is typically narrow. The horns are usually relatively short in comparison to other representatives of the genus, however the length of these may vary significantly within the species.
Stratigraphical and Geographical Distribution. Muderongia endovata sp. nov. is a geographically extremely widespread species which has been reported from the Early Cretaceous of arctic Canada, Australia, Europe, Greenland, the Middle East, offshore North Africa, the North and South Atlantic, Norway, and Spitsbergen (see synonymy listing, above). It is present, in significant proportions, (attributed to Muderongia simplex) from the late Ryazanian (Stenomphalus zone) to the late Hauterivian (Marginatus/Variabilis zones) in northwest Europe (TextFigure 1; Duxbury, 1978; Davey, 1979; 1982; Woollam andRiding, 1983; Costa and Davey, 1992). Duxbury (1977) and Heilmann-Clausen (1987) stated that this form extends into the early-mid Barremian. It is possible that either the species is present sporadically and in low numbers in Lower Barremian strata or that these Barremian records represent reworking. Schi0ler (1992) illustrated a specimen of this species (as Muderongia simplex subsp. simplex) from the Upper Cretaceous (Coniacian) of Bornholm, Denmark, which is intepreted as representing stratigraphical recycling from the late Ryazanian to late Hauterivian. Barron (1989, pi. 2, figs. 8, 9) illustrated a single specimen which he attributed to Muderongia simplex (i.e. Muderongia endovata) from the Middle Volgian of northeast Scotland. This specimen differs from typical Lower Cretaceous specimens of Muderongia endovata in that it has relatively long equatorial/lateral and antapical horns. It is therefore questionably attributed to Muderongia endovata and is most likely to be an aberrant specimen. Poulsen (1996, pi. 23, fig. 5) also illustrated a rather squat specimen of Muderongia endovata (as Muderongia simplex) from ammonite-bearing strata from the Middle Volgian of Poland. This record is from the Scythicus Subzone of the Scythicus Zone, which is equivalent to the Albani Zone. Thus it appears that Muderongia endovata may be extremely rare in the mid Volgian of Europe, absent during the late Volgian-early-earliest late Ryazanian and reappearing in large numbers in the late Ryazanian (Stenomphalus Zone).
Comparison. Muderongia endovata sp. nov. differs from all other species of this genus in having relatively short, straight and blunt apical, lateral and antapical horns and an ovoidal to subspherical endocyst, giving a circumcavate cyst organisation. The lateral horns are of the Axial type L I of Monteil (1991), meaning that they are aligned with the paracingulum, indented and show equal development of precingular and postcingular extensions (Monteil, 1991, table 3). Thus all species with 'bent' and 'curved' lateral horns (types L II and L IV of Monteil (1991) respectively) differ profoundly from Muderongia endovata in both lateral horn morphology and general shape. These taxa comprise Muderongia australis, M. asymmetrica, M. crucis, M. extensiva, M. macwhaei, M. staurota, M. testudinaria andM tetracantha. Furthermore, although Muderongia endovata has a single antapical horn, it is not axial (i.e. type ATP I of Monteil, 1991) as the horn is distinctly offset to the left and there is a reduced or incipient horn in the right antapical area. Hence, Muderongia endovata is deemed to have 'joined' (type ATP II) antapical horns of Monteil (1991, table 4). This means that Muderongia aequicornus, M. pariataandM. tomaszowensis differ from M. endovata as they have 'not joined' (type ATP HI) and axial antapical horn types (Monteil, 1991). Additionally, Muderongia longicorna has two long, subequal antapical horns, which may be pointed distally. Microperforate periphragm is a characteristic feature of Muderongia microperforata, M. perforata and M. siciliana. Furthermore, M. siciliana is a small species with unequally developed lateral horns (Torricelli, 1996). Muderongia simplex differs from M. endovata in having a rounded rectangular to subpentagonal endocyst, engendering a cornucavate cyst organisation.
Holotype: Riding et al., 2001, pl.1, fig.1; text-fig.3.
Age: Valanginian.
Original description (Riding et al., 2001):
Muderongia endovata sp. nov. Plate 1, figs. 1, 2; Text-Figure 3 Muderongia simplex, Alberti, 1961, p. 12, pi. 2, fig. 6, pi. 12, fig. 1 (non. pi. 2, figs. 1,2,4,5, pi. 12, fig. 2); Millioud, 1967, pi. 2, fig. 16; Brideaux, 1976, pi. 44.2, fig. 1; Duxbury, 1977, p. 55, pi. 14, fig. 9; Harris, 1977, pi. 20, fig. 6; Duxbury, 1978, pi. 3, fig. 2; Raynaud, 1978, pi. 1, fig. 8; Thusu, 1978, pi. 2, fig. 4; Ashraf, 1979, p. 136, pi. 6, fig. 10; Davey, 1979, pi. 2, figs. 7-8; Piasecki, 1979, fig. 15; Dorhofer and Davies, 1980, figs. 34D, 36C-G; Morgan, 1980, pi. 19, figs. 7-10; Williams and Bujak, 1980, pi. 5, figs. 2,4; Below, 1981, pi. 1, fig. 6; Woollam and Riding, 1983, pi. 8, figs. 7-8; Thusu and Van der Eem, 1985, pi. 53, fig. 4; Williams and Bujak, 1985, textfig. 33.16; Aarhus et al., 1986, fig. lOo; Davey, 1987, pi. 5, fig. 14; Habib and Drugg, 1987, pi. 4, fig. 1; Heilmann-Clausen, 1987, pi. 1, figs. 9-10; Thusu et al., 1988, pi. 29, figs.8,9;?Barron, 1989, pi. 2, figs. 8,9; Colin etal., 1992, pi. 4, figs. 11,12; Costa and Davey, 1992, pi. 3.2, fig. 4; Poulsen, 1996, pp. 57, 58, pi. 23, fig. 5.
Muderongia simplex Alberti, 1961, p. 12, pi. 2, fig. 6, pi. 12, fig. 1 (non. pi. 2, figs. 1, 2, 4, 5, pi. 12, fig. 2) subsp. simplex (autonym, now redundant); Schi0ler, 1992, pi. 9, fig. 5.
Muderongia sp. cf. M. simplex Alberti, 1961, p. 12, pi. 2, figs. 1,6, pl.12, fig. 2 (non. pi. 2, figs. 2,4, pi. 12, fig. 2); Mclntyre and Brideaux, 1980, pi. 12, fig. 4.
Muderongia sp. cf. M. mcwhaeli Cookson & Eisenack 1958, p. 41, pi. 6, figs. 1-5; Wiseman, 1980, pi. 1, fig. 3.
Derivation of Name. The specific epithet refers to the ovoidal shape of the endocyst.
Diagnosis. A species of Muderongia, the thin periphragm of which forms one apical horn, two equatorial/lateral horns and one antapical horn giving a typical rhomboid to rounded subpentagonal ceratioid amb. The area of the periphragm in the right antapical area, close to the 5"/6"' parasuture, forms a prominent shoulder or protrusion which is a reduced or incipient right antapical horn. The left antapical horn is close to the lp/1"" parasuture and is the longest and most prominent. The horns are subconical, tapering distally and with rounded, closed terminations. The equatorial/lateral horns, however, may be subrhombic with a medial concavity at the distal extremities at the position of the paracingulum. The equatorial/lateral horns are frequently longer posterior to the position of the paracingulum and may point slightly in an antapical direction. The endocyst is ovoidal to longitudinally elongate subspherical; it may have a small antapical boss. The ovoidal/subspherical endocyst engenders a circumcavate cyst organisation. Periphragm continuous, thin, smooth to microscabrate; endophragm continuous, relatively thick, smooth, scabrate or microgranulate. Archeopyle apical, type (4A). Paratabulation corniform gonyaulacacean, indicated, sometimes partially, by low, smooth, discontinuous ridges on the periphragm. Paracingulum indicated by low ridges on the periphragm and frequently a medial concavity on the equatorial/lateral horns. Parasulcus indicated by low ridges on the periphragm and the parasulcal notch, offset to the left.
Holotype. Specimen MPK 1275, Housed in the palynological collections of the British Geological Survey, Keyworth, Nottingham, UK.
Locality and Horizon. Haldager No. 1 Borehole, Denmark (Davey, 1979, text-fig, lb), core depth 863.19m- 866.24m.
Paratype. Specimen figured as Muderongia simplex Alberti, 1961 (pi. 2, fig. 6). Housed in the palynological collections of the Bundesanstalt fur Geowissenschaften und Rohstoffe Aussenstelle, Berlin, Germany.
Locality and Horizon. The Valanginian of the Dabendorf Borehole, Germany (slide 2a/Dl of Alberti, 1961).
Dimensions. The holotype measures 104.5 µm in overall length and 75.5 µm in overall width; the endocyst is 64.5 µm long and 55.5 µm wide. The paratype is 118.0 µm in overall length and 92.5 µum in overall width; the endocyst measures 76.0 µm in length and 72.5 µm in width.
Assemblage of 35 specimens measured (µm, Min.(Mean)Max.)
Overall cyst length (incl. operculum): 98.5(107.5)118.5
Overall cyst width: 63.5(69.5)78.0
Endocyst length (incl. operculum): 62.5(66.0)71.5
Endocyst width: 50.5(56.5)63.5
Remarks. The periphragm of Muderongia endovata sp. nov. is normally psilate and the pericoel is typically narrow. The horns are usually relatively short in comparison to other representatives of the genus, however the length of these may vary significantly within the species.
Stratigraphical and Geographical Distribution. Muderongia endovata sp. nov. is a geographically extremely widespread species which has been reported from the Early Cretaceous of arctic Canada, Australia, Europe, Greenland, the Middle East, offshore North Africa, the North and South Atlantic, Norway, and Spitsbergen (see synonymy listing, above). It is present, in significant proportions, (attributed to Muderongia simplex) from the late Ryazanian (Stenomphalus zone) to the late Hauterivian (Marginatus/Variabilis zones) in northwest Europe (TextFigure 1; Duxbury, 1978; Davey, 1979; 1982; Woollam andRiding, 1983; Costa and Davey, 1992). Duxbury (1977) and Heilmann-Clausen (1987) stated that this form extends into the early-mid Barremian. It is possible that either the species is present sporadically and in low numbers in Lower Barremian strata or that these Barremian records represent reworking. Schi0ler (1992) illustrated a specimen of this species (as Muderongia simplex subsp. simplex) from the Upper Cretaceous (Coniacian) of Bornholm, Denmark, which is intepreted as representing stratigraphical recycling from the late Ryazanian to late Hauterivian. Barron (1989, pi. 2, figs. 8, 9) illustrated a single specimen which he attributed to Muderongia simplex (i.e. Muderongia endovata) from the Middle Volgian of northeast Scotland. This specimen differs from typical Lower Cretaceous specimens of Muderongia endovata in that it has relatively long equatorial/lateral and antapical horns. It is therefore questionably attributed to Muderongia endovata and is most likely to be an aberrant specimen. Poulsen (1996, pi. 23, fig. 5) also illustrated a rather squat specimen of Muderongia endovata (as Muderongia simplex) from ammonite-bearing strata from the Middle Volgian of Poland. This record is from the Scythicus Subzone of the Scythicus Zone, which is equivalent to the Albani Zone. Thus it appears that Muderongia endovata may be extremely rare in the mid Volgian of Europe, absent during the late Volgian-early-earliest late Ryazanian and reappearing in large numbers in the late Ryazanian (Stenomphalus Zone).
Comparison. Muderongia endovata sp. nov. differs from all other species of this genus in having relatively short, straight and blunt apical, lateral and antapical horns and an ovoidal to subspherical endocyst, giving a circumcavate cyst organisation. The lateral horns are of the Axial type L I of Monteil (1991), meaning that they are aligned with the paracingulum, indented and show equal development of precingular and postcingular extensions (Monteil, 1991, table 3). Thus all species with 'bent' and 'curved' lateral horns (types L II and L IV of Monteil (1991) respectively) differ profoundly from Muderongia endovata in both lateral horn morphology and general shape. These taxa comprise Muderongia australis, M. asymmetrica, M. crucis, M. extensiva, M. macwhaei, M. staurota, M. testudinaria andM tetracantha. Furthermore, although Muderongia endovata has a single antapical horn, it is not axial (i.e. type ATP I of Monteil, 1991) as the horn is distinctly offset to the left and there is a reduced or incipient horn in the right antapical area. Hence, Muderongia endovata is deemed to have 'joined' (type ATP II) antapical horns of Monteil (1991, table 4). This means that Muderongia aequicornus, M. pariataandM. tomaszowensis differ from M. endovata as they have 'not joined' (type ATP HI) and axial antapical horn types (Monteil, 1991). Additionally, Muderongia longicorna has two long, subequal antapical horns, which may be pointed distally. Microperforate periphragm is a characteristic feature of Muderongia microperforata, M. perforata and M. siciliana. Furthermore, M. siciliana is a small species with unequally developed lateral horns (Torricelli, 1996). Muderongia simplex differs from M. endovata in having a rounded rectangular to subpentagonal endocyst, engendering a cornucavate cyst organisation.