Back
Nannoceratopsis ridingii
Nannoceratopsis ridingii Poulsen 1992
Holotype: Poulsen, 1992, pl.1, fig.E
Paratypes: Poulson, 1992
Locus typicus: Denmark
Stratum typicum: Pliensbachian-Aalenian
Original diagnosis: Poulsen, 1992, p. 45
A species of Nannoceratopsis having two distinct antapical horns pointing antapically and one distinct ventral horn on the hypocyst in the position of the two small paraplates H1 and H4; this horn is pointing apically. The wall, which is an autophragm, appears almost smooth by transmitted light microscopy, but is resolved by the SEM ( x 10,000) as verrucate or granulate.
Original description: Poulsen, 1992, p. 45
Compressed lateral with an ""H""-shaped outline, i.e. square with the two sides curved towards the bar of the ""H"". The bars of the ""H"" are formed by the three horns and the apex. Two antapical horns are well-developed, with finely pointed ends similar to those of, for example, Nannoceratopsis spiculata (Plate Il). One welldeveloped horn, also with a finely pointed end is placed on the upper ventral side of the hypocyst at the end of the longitudinal groove in the position of the two small hypocystal paraplates H1 and H4. The surface commonly appears smooth. Only at high magnification by the SEM is a finely verrucate or granulate surface evident. The paracingulum, the sagittal bands and a small paracingular area are usually visible.
Affinities:
Poulsen, 1992, p. 45: This species differs from Nannoceratopsis triceras Drugg, 1978 in the position of the three horns. It differs from the other species of Nannoceratop.si.s in having three horns on the hypocyst. In SEM-studies the surface is most similar to Nannoceratopsis senex van Helden, 1977 and Nannoceratopsis cf. triangulata (see Plate Ill, A, B; Plate IV, K, L) and is finely verrucate at high magnifications. The surface of N. senex van Helden, 1977 may, however, differ in being finely microreticulate (Piel and Evitt, 1980). Nannoceratopsis gracilis Alberti, 1961 emend. Evitt, 1962 is reticulate (Piel and Evitt, 1980), N. spiculata Stover, 1966 has an apparently smooth surface but is seen to be microfibrous under the SEM ( x 10,000), and N. pellucida Deflandre, 1938 emend. Evitt, 1961 is reticulate.
Poulsen 1996 p.54, Pl. 36, Figs. 3-4, Pl. 40, Fig. 6
Remarks. The surface commonly appears smooth. A finely verrucate or granulate surface is evident only at high magnification by the SEM.
Recorded occurrences. Denmark: L. spinosa Zone, Subzone b to P. nasuta Subzone of the M. semitabulatum Zone.
Holotype: Poulsen, 1992, pl.1, fig.E
Paratypes: Poulson, 1992
Locus typicus: Denmark
Stratum typicum: Pliensbachian-Aalenian
Original diagnosis: Poulsen, 1992, p. 45
A species of Nannoceratopsis having two distinct antapical horns pointing antapically and one distinct ventral horn on the hypocyst in the position of the two small paraplates H1 and H4; this horn is pointing apically. The wall, which is an autophragm, appears almost smooth by transmitted light microscopy, but is resolved by the SEM ( x 10,000) as verrucate or granulate.
Original description: Poulsen, 1992, p. 45
Compressed lateral with an ""H""-shaped outline, i.e. square with the two sides curved towards the bar of the ""H"". The bars of the ""H"" are formed by the three horns and the apex. Two antapical horns are well-developed, with finely pointed ends similar to those of, for example, Nannoceratopsis spiculata (Plate Il). One welldeveloped horn, also with a finely pointed end is placed on the upper ventral side of the hypocyst at the end of the longitudinal groove in the position of the two small hypocystal paraplates H1 and H4. The surface commonly appears smooth. Only at high magnification by the SEM is a finely verrucate or granulate surface evident. The paracingulum, the sagittal bands and a small paracingular area are usually visible.
Affinities:
Poulsen, 1992, p. 45: This species differs from Nannoceratopsis triceras Drugg, 1978 in the position of the three horns. It differs from the other species of Nannoceratop.si.s in having three horns on the hypocyst. In SEM-studies the surface is most similar to Nannoceratopsis senex van Helden, 1977 and Nannoceratopsis cf. triangulata (see Plate Ill, A, B; Plate IV, K, L) and is finely verrucate at high magnifications. The surface of N. senex van Helden, 1977 may, however, differ in being finely microreticulate (Piel and Evitt, 1980). Nannoceratopsis gracilis Alberti, 1961 emend. Evitt, 1962 is reticulate (Piel and Evitt, 1980), N. spiculata Stover, 1966 has an apparently smooth surface but is seen to be microfibrous under the SEM ( x 10,000), and N. pellucida Deflandre, 1938 emend. Evitt, 1961 is reticulate.
Poulsen 1996 p.54, Pl. 36, Figs. 3-4, Pl. 40, Fig. 6
Remarks. The surface commonly appears smooth. A finely verrucate or granulate surface is evident only at high magnification by the SEM.
Recorded occurrences. Denmark: L. spinosa Zone, Subzone b to P. nasuta Subzone of the M. semitabulatum Zone.