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Nannoceratopsis globiformis
Nannoceratopsis globiformis Bucefalo Palliani and Riding, 1997b, p.115–116, pl.1, figs.1–8; text-fig.9 (part).
Holotype: Bucefalo Palliani and Riding, 1997b, pl.1, figs.1–2.
Age: late Pliensbachian.
Original description: Bucefalo Palliani & Riding, 1997: Nannoceratopsis globiformis sp. nov. (Pl. 1, fig . 1-8)
1988. Nannoceratopsis globiformis. - DE VAINS, p. 463; pl. 1, figs. 13-16. ·
Derivation of name: The specific name is derived from the globose, subspherical lateral outline of this form.
Holotype: Specimen MPK 10751, Sample 012, England Finder coordinate H51.
Repository: Collections of the Basin Analysis and Stratigraphy Group, British Geological Survey, Nottingham, United Kingdom.
Type localities: Lower Loubressac section, Ouercy, southwest France.
Stratigraphical horizon: Late Pliensbachian, Spinatum Zone, sample 012.
Diagnosis: A globose, subspherical to rounded subtriangular species of Nannoceratopsis having a two rounded antapical horns of broadly similar size; the autophragm is microperforate.
Description: A species of Nannoceratopsis which has a globose, subspherical to rounded subtriangular lateral outline. The large hypocyst is normally characterized by two well-developed, wide antapical horns with rounded terminations. The ventral horn is normally slightly smaller than the dorsal horn, the horns may be of similar size, or the ventral horn may be significantly reduced. The morphology of the horns helps to impart the characteristic globose, rounded lateral outline of the hypocyst. The autophragm is relatively thin and the surface is microperforate. The sagittal band is not thickened. The paracingulum is consistently well developed.
Dimensions (Min.(Mean)Max.):
Overall length of cyst: 53 (57) 62 µm
Overall width of cyst: 33 (39) 44 µm
35 specimens measured.
Comparison: Nannoceratopsis globiformis sp. nov. differs from Nannoceratopsis ridingii and Nannoceratopsis triceras in having two, not three, hypocystal horns. It differs from Nannoceratopsis evae, which is devoid of horns. Furthermore, Nannoceratopsis deflandrei subsp. senex is characterized by a prominent single hypocystal horn. The well rounded, subspherical outline of the hypocystal horns distinguishes Nannoceratopsis globiformis sp. nov. from the other species of Nannoceratopsis with two distally pointed horns, for example Nannoceratopsis deflandrei subsp. deflandrei, N. gracilis, N. pellucida, N. plegas, N. radiata, N. spiculata, and N. triangulata. Moreover the autophragm of Nannoceratopsis globiformis sp. nov. is microperforate, whereas that of Nannoceratopsis deflandrei and Nannoceratopsis gracilis are respectively areolate to granulate /scabrate and microreticulate (Evin, 1961; ILYINA et al .. 1994). The sagittal band of Nannoceratopsis globiformis sp. nov. is not thickened as in Nannoceratopsis ambonis and Nannoceratopsis dictyambonis. The most important morphological and stratigraphical features of the species of Nannoceratopsis are illustrated in Tab.I-II and Fig. 9.
Holotype: Bucefalo Palliani and Riding, 1997b, pl.1, figs.1–2.
Age: late Pliensbachian.
Original description: Bucefalo Palliani & Riding, 1997: Nannoceratopsis globiformis sp. nov. (Pl. 1, fig . 1-8)
1988. Nannoceratopsis globiformis. - DE VAINS, p. 463; pl. 1, figs. 13-16. ·
Derivation of name: The specific name is derived from the globose, subspherical lateral outline of this form.
Holotype: Specimen MPK 10751, Sample 012, England Finder coordinate H51.
Repository: Collections of the Basin Analysis and Stratigraphy Group, British Geological Survey, Nottingham, United Kingdom.
Type localities: Lower Loubressac section, Ouercy, southwest France.
Stratigraphical horizon: Late Pliensbachian, Spinatum Zone, sample 012.
Diagnosis: A globose, subspherical to rounded subtriangular species of Nannoceratopsis having a two rounded antapical horns of broadly similar size; the autophragm is microperforate.
Description: A species of Nannoceratopsis which has a globose, subspherical to rounded subtriangular lateral outline. The large hypocyst is normally characterized by two well-developed, wide antapical horns with rounded terminations. The ventral horn is normally slightly smaller than the dorsal horn, the horns may be of similar size, or the ventral horn may be significantly reduced. The morphology of the horns helps to impart the characteristic globose, rounded lateral outline of the hypocyst. The autophragm is relatively thin and the surface is microperforate. The sagittal band is not thickened. The paracingulum is consistently well developed.
Dimensions (Min.(Mean)Max.):
Overall length of cyst: 53 (57) 62 µm
Overall width of cyst: 33 (39) 44 µm
35 specimens measured.
Comparison: Nannoceratopsis globiformis sp. nov. differs from Nannoceratopsis ridingii and Nannoceratopsis triceras in having two, not three, hypocystal horns. It differs from Nannoceratopsis evae, which is devoid of horns. Furthermore, Nannoceratopsis deflandrei subsp. senex is characterized by a prominent single hypocystal horn. The well rounded, subspherical outline of the hypocystal horns distinguishes Nannoceratopsis globiformis sp. nov. from the other species of Nannoceratopsis with two distally pointed horns, for example Nannoceratopsis deflandrei subsp. deflandrei, N. gracilis, N. pellucida, N. plegas, N. radiata, N. spiculata, and N. triangulata. Moreover the autophragm of Nannoceratopsis globiformis sp. nov. is microperforate, whereas that of Nannoceratopsis deflandrei and Nannoceratopsis gracilis are respectively areolate to granulate /scabrate and microreticulate (Evin, 1961; ILYINA et al .. 1994). The sagittal band of Nannoceratopsis globiformis sp. nov. is not thickened as in Nannoceratopsis ambonis and Nannoceratopsis dictyambonis. The most important morphological and stratigraphical features of the species of Nannoceratopsis are illustrated in Tab.I-II and Fig. 9.