Back
Nannoceratopsis
From Williams et al., 2017:
[Nannoceratopsis, Deflandre, 1939a, p.183. Emendations: Evitt, 1961b, p.306; Piel and Evitt, 1980, p.102; Poulsen, 1992b, p.44; Riding and Helby, 2001a, p.13
Type species: Nannoceratopsis pellucida, Deflandre, 1939a (pl.8, fig.10)] ; emend. Evitt, 1961
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Deflandre, 1938]: (Translation: Stover and Evitt, 1978, p. 214):
Diagnosis:
It is an organism whose immediate aspect is very characteristic, for it assumes the shape of a sort of very robust fork, which would recall a little, if you like, the half open pincer of a crab. One distinguishes on the one hand the main body, which carries the two strong horns; on the other hand, opposite these horns, an apex of peculiar structure, which is lacking in a good number of specimens and can only be studied under very favorable conditions. The upper part of this apex is separated from the rest of the body by a sort of very oblique groove, starting from the left side and sloping towards the right. I interpret this groove as a longitudinal furrow. To the right of this furrow stands the projecting part of the apex, often a little constricted to the level of the upper part of the groove, then slightly widened and carrying, at its extremity, a short lip perpendicular to the main plane of the organism as it is oriented in the figures. If the face into which the groove is spreading is considered ventral, then this apical protrusion is dorsal and normal to the groove.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Emended description:
Evitt, 1961:
Diagnosis:
Theca laterally compressed, usually subtriangular with two prominent antapical horns (points) separated by antapical concavity. ventral antapical horn may be reduced or completely undeveloped, causing thecal outline to be ovoid in extreme cases. Epitheca minute, separated by subapical girdle from the hypotheca that constitutes most of the theca. Dorsal, antapical, and ventral surfaces of hypotheca narrow, set off from larger lateral surfaces by narrow ridges developed with variable distinctness. Longitudinal furrow confined to the hypotheca where it occupies a portion of narrow ventral surface.
---------------------------------------
Piel and Evitt, 1980:
Synopsis:
Cysts proximate, compressed laterally, usually with two antapical horns, of which the ventral horn may be reduced or undeveloped; epicyst minute, hypocyst large; dorsal, ventral, and antapical surfaces narrow, lateral surfaces wide. Paratabulation rarely visible, combining peridinialean arrangement in epicyst with dinophysialean in hypocyst. Archaeopyle cingular, Type C, involving paraplate 3c and possibly others.
Description:
Shape (in lateral view): Some what triangular with pronounced concavity between antapical horns; ventral horn may be reduced or absent. Outline of dorsal surface gently convex, that of ventral surface convex to straight, commonly with marked angularity at anterior end of sagittal band. Epicyst minute; large hypocyst constitutes most of the cyst. Specimens show preferred orientation because of latter flattening.
Wall features: Parasutural interruptions may be visible in complexly sculptured, spongy to areolate wall; surface may also be smooth. On only the hypocyst a sagittal band is commonly differentiated, and lateral connections of similar form may extend along the paracingulum between the ends of sagittal band. Bans vary between concave and convex, and may be transversely striate, margined by a narrow ridge, and crossed by ridges, or not any of these.
Paratabulation: Indicated by parasutural features, formula: ?pr, 5`, 5``, 4c, 4s, 4H; hypocyst with two large lateral paraplates and two small, elongate ventral ones immediately posterior to parasulcus; larger and smaller hypocystal paraplates separated by lateral continuations from sagittal band. Largest sulcal paraplate is the anterior one, which extends onto epicyst, separating 1`` and 5``.
Archaeopyle: Cingular, Type C, formed by middorsal paraplate (3c) alone or, possibly, in combination with others; operculum free.
Paracingulum: Expressed as a narrow, necklike, encircling, subapical band between the minute epicyst and the large hypocyst; a descending spiral with ends offset about one paracingulum width.
Parasulcus: Formed largely by part of ventral surface between ends of precingular and cingular series of paraplates; limits not sharply marked, but extends anteriorly onto epicyst.
Size: Mostly in the range of 50-100 µm.
---------------------------------------
Poulsen, 1992:
Description:
Cyst proximate, compressed laterally, lacking or with one, two or three antapical horns and lacking or with a ventral horn. In specimens with only one antapical horn, this may be reduced. In species with two antapical horns the ventral horn may be reduced. A ventral horn may be present at the end of the the longitudinal groove area in the position of the two small hypocystal paraplates H1 and H4. This horn may point upwards. All other features as in Piel and Evitt (1980).
Remarks:
Piel and Evitt (1980) showed that scanning electron microscopy (SEM) high magnification studies (x 10,000) of wall structures show important specific characteristics. Examinations of other Nannoceratopsis species (this study) in SEM indicates three distinct `lineages` within the genus:
Senex complex:
The autophragmal wall sculpture and structure of species of the Senex complex is shagreenate, spongy, perforate and granulate.
Nannoceratopsis ridingii Poulsen 1992 - Pl. 36, Figs. 3-4, Pl. 40, Fig. 6
The surface commonly appears smooth. A finely verrucate or granulate surface is evident only at high magnification by the SEM.
Gracilis complex:
The wall of cysts in this complex includes both an autophragm and an ectophragm. The ectophragm is smooth, microscabrate, corrugate to rugulate with variable perforations, being partial, and is supported by structures from the underlying autophragm (Pl. 37). The autophragm is a shagreenate, spongy and granulate, very similar to that of the Senex complex.
N. senex occurs consistently earlier then N. gracilis, for which reason it is believed that the Gracilis complex arose from the Senex complex by developing an ectophragm. The ectophragm of N. gracilis developed through time from its first appearance in the Pliensbachian until it became extinct at the Bathonian-Callovian boundary (Davies, 1983; Riding and Thomas, 1992). The perforation of the ectophragm apparently changed from large pores to small pores.
It should be noted that specimens of the Gracilis complex with a damaged or corroded ectophragm may be misidentified as belonging to the Senex complex, (Pl. 37, Figs. 5-8). However, N. gracilis specimens with two distinct antapical horns are never seen without an ectophragm, indicating that N. senex and N. gracilis are two separate species.
The ectophragm of figured specimens from the Late Toarcian of Germany shows weak granulation and finer and more widely spaced perforations than the specimens of N. gracilis figured by Piel and Evitt (1980).
Spiculata complex:
This complex appears to have a smooth surface at lower magnifications, but in SEM (x 10,000) it has an irregular vermiculate `felt-like` mesh on the surface.
Nannoceratopsis sp. 1 of Poulsen 1996 - Pl. 40, Fig. 1: A species comprising rounded cysts, without horns. The wall structure is a smooth autophragm. The size is small (length 43 µm, width 34 µm). It resembles Nannoceratopsis evae in shape, but has a smooth wall structure.
Nannoceratopsis sp. 2 of Poulsen 1996 - Pl. 35, Fig. 16: This is the only specimen found in Denmark with somewhat thickened sagittal bands, but the sagittal bands on this specimen are not as thick as those of Nannoceratopsis ambonis Drugg 1978 emend. Riding 1984.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Modified description:
Stover and Evitt, 1978, p. 215:
Synopsis:
Cysts proximate, compressed laterally, usually with two antapical horns, of which the ventral horn may be reduced or undeveloped; epicyst minute, hypocyst large; dorsal, ventral, and antapical surfaces narrow, lateral surfaces wide; archeopyle epicystal, probably analogous to Type APa.
Description:
Shape (in lateral view): Somewhat triangular with pronounced concavity between antapical horns; ventral horn may be reduced or absent. Outline of dorsal surface gently convex, that of ventral surface gently convex to straight, commonly with marked angularity at juncture of parasulcus and sagittal band. Epicyst minute; larger hypocst constitutes most of the cyst. Specimens show preferred orientation because of lateral flattening.
Wall relationships: Autophragm only.
Wall Features: No parasutural features. Low sagittal ridges may occur along the junctures of the lateral surfaces with the dorsal and ventral surfaces. Short transverse ridge may cross the ventral surface. Autophragm smooth to areolate.
Paratabulation: None indicated.
Archeopyle: Epicystal, probably analogous to combination archeopyle, Type APa; operculum usually attached ventrally.
Paracingulum: Expressed as a narrow, necklike, encircling, subapical band between the the minute epicyst and the large hypocyst.
Parasulcus: Part of the ventral surface extending from the ventral angularity; lateral and antapical limits may be defined by ridges.
Size: Intermediate to large.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Nannoceratopsis Deflandre, 1939a, emend. Evitt, 1961b, emend Piel and Evitt, 1980, emend. Poulsen, 1992b. Nannoceratopsis was emended by Poulsen (1992b, p.44) as follows, Cyst proximate, compressed laterally, lacking or with one, two or three antapical horns and lacking or with a ventral horn. In specimens with only one antapical horn, this may be reduced. In species with two antapical horns the ventral horn may be reduced. A ventral horn may be present at the end of the longitudinal groove area in the position of the two small hypocystal paraplates H1 and H4. This horn may point upwards. All other features as in Piel and Evitt (1980). These authors (p.102) provided the following synopsis: Cysts proximate, compressed laterally, usually with two antapical horns, of which the ventral horn may be reduced or undeveloped; epicyst minute, hypocyst large; dorsal, ventral, and antapical surfaces narrow, lateral surfaces wide. Paratabulation rarely visible, combining peridinialean arrangement in epicyst with dinophysialean in hypocyst. Archeopyle cingular, type C, involving paraplate 3c and possibly others.
[Nannoceratopsis, Deflandre, 1939a, p.183. Emendations: Evitt, 1961b, p.306; Piel and Evitt, 1980, p.102; Poulsen, 1992b, p.44; Riding and Helby, 2001a, p.13
Type species: Nannoceratopsis pellucida, Deflandre, 1939a (pl.8, fig.10)] ; emend. Evitt, 1961
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Deflandre, 1938]: (Translation: Stover and Evitt, 1978, p. 214):
Diagnosis:
It is an organism whose immediate aspect is very characteristic, for it assumes the shape of a sort of very robust fork, which would recall a little, if you like, the half open pincer of a crab. One distinguishes on the one hand the main body, which carries the two strong horns; on the other hand, opposite these horns, an apex of peculiar structure, which is lacking in a good number of specimens and can only be studied under very favorable conditions. The upper part of this apex is separated from the rest of the body by a sort of very oblique groove, starting from the left side and sloping towards the right. I interpret this groove as a longitudinal furrow. To the right of this furrow stands the projecting part of the apex, often a little constricted to the level of the upper part of the groove, then slightly widened and carrying, at its extremity, a short lip perpendicular to the main plane of the organism as it is oriented in the figures. If the face into which the groove is spreading is considered ventral, then this apical protrusion is dorsal and normal to the groove.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Emended description:
Evitt, 1961:
Diagnosis:
Theca laterally compressed, usually subtriangular with two prominent antapical horns (points) separated by antapical concavity. ventral antapical horn may be reduced or completely undeveloped, causing thecal outline to be ovoid in extreme cases. Epitheca minute, separated by subapical girdle from the hypotheca that constitutes most of the theca. Dorsal, antapical, and ventral surfaces of hypotheca narrow, set off from larger lateral surfaces by narrow ridges developed with variable distinctness. Longitudinal furrow confined to the hypotheca where it occupies a portion of narrow ventral surface.
---------------------------------------
Piel and Evitt, 1980:
Synopsis:
Cysts proximate, compressed laterally, usually with two antapical horns, of which the ventral horn may be reduced or undeveloped; epicyst minute, hypocyst large; dorsal, ventral, and antapical surfaces narrow, lateral surfaces wide. Paratabulation rarely visible, combining peridinialean arrangement in epicyst with dinophysialean in hypocyst. Archaeopyle cingular, Type C, involving paraplate 3c and possibly others.
Description:
Shape (in lateral view): Some what triangular with pronounced concavity between antapical horns; ventral horn may be reduced or absent. Outline of dorsal surface gently convex, that of ventral surface convex to straight, commonly with marked angularity at anterior end of sagittal band. Epicyst minute; large hypocyst constitutes most of the cyst. Specimens show preferred orientation because of latter flattening.
Wall features: Parasutural interruptions may be visible in complexly sculptured, spongy to areolate wall; surface may also be smooth. On only the hypocyst a sagittal band is commonly differentiated, and lateral connections of similar form may extend along the paracingulum between the ends of sagittal band. Bans vary between concave and convex, and may be transversely striate, margined by a narrow ridge, and crossed by ridges, or not any of these.
Paratabulation: Indicated by parasutural features, formula: ?pr, 5`, 5``, 4c, 4s, 4H; hypocyst with two large lateral paraplates and two small, elongate ventral ones immediately posterior to parasulcus; larger and smaller hypocystal paraplates separated by lateral continuations from sagittal band. Largest sulcal paraplate is the anterior one, which extends onto epicyst, separating 1`` and 5``.
Archaeopyle: Cingular, Type C, formed by middorsal paraplate (3c) alone or, possibly, in combination with others; operculum free.
Paracingulum: Expressed as a narrow, necklike, encircling, subapical band between the minute epicyst and the large hypocyst; a descending spiral with ends offset about one paracingulum width.
Parasulcus: Formed largely by part of ventral surface between ends of precingular and cingular series of paraplates; limits not sharply marked, but extends anteriorly onto epicyst.
Size: Mostly in the range of 50-100 µm.
---------------------------------------
Poulsen, 1992:
Description:
Cyst proximate, compressed laterally, lacking or with one, two or three antapical horns and lacking or with a ventral horn. In specimens with only one antapical horn, this may be reduced. In species with two antapical horns the ventral horn may be reduced. A ventral horn may be present at the end of the the longitudinal groove area in the position of the two small hypocystal paraplates H1 and H4. This horn may point upwards. All other features as in Piel and Evitt (1980).
Remarks:
Piel and Evitt (1980) showed that scanning electron microscopy (SEM) high magnification studies (x 10,000) of wall structures show important specific characteristics. Examinations of other Nannoceratopsis species (this study) in SEM indicates three distinct `lineages` within the genus:
Senex complex:
The autophragmal wall sculpture and structure of species of the Senex complex is shagreenate, spongy, perforate and granulate.
Nannoceratopsis ridingii Poulsen 1992 - Pl. 36, Figs. 3-4, Pl. 40, Fig. 6
The surface commonly appears smooth. A finely verrucate or granulate surface is evident only at high magnification by the SEM.
Gracilis complex:
The wall of cysts in this complex includes both an autophragm and an ectophragm. The ectophragm is smooth, microscabrate, corrugate to rugulate with variable perforations, being partial, and is supported by structures from the underlying autophragm (Pl. 37). The autophragm is a shagreenate, spongy and granulate, very similar to that of the Senex complex.
N. senex occurs consistently earlier then N. gracilis, for which reason it is believed that the Gracilis complex arose from the Senex complex by developing an ectophragm. The ectophragm of N. gracilis developed through time from its first appearance in the Pliensbachian until it became extinct at the Bathonian-Callovian boundary (Davies, 1983; Riding and Thomas, 1992). The perforation of the ectophragm apparently changed from large pores to small pores.
It should be noted that specimens of the Gracilis complex with a damaged or corroded ectophragm may be misidentified as belonging to the Senex complex, (Pl. 37, Figs. 5-8). However, N. gracilis specimens with two distinct antapical horns are never seen without an ectophragm, indicating that N. senex and N. gracilis are two separate species.
The ectophragm of figured specimens from the Late Toarcian of Germany shows weak granulation and finer and more widely spaced perforations than the specimens of N. gracilis figured by Piel and Evitt (1980).
Spiculata complex:
This complex appears to have a smooth surface at lower magnifications, but in SEM (x 10,000) it has an irregular vermiculate `felt-like` mesh on the surface.
Nannoceratopsis sp. 1 of Poulsen 1996 - Pl. 40, Fig. 1: A species comprising rounded cysts, without horns. The wall structure is a smooth autophragm. The size is small (length 43 µm, width 34 µm). It resembles Nannoceratopsis evae in shape, but has a smooth wall structure.
Nannoceratopsis sp. 2 of Poulsen 1996 - Pl. 35, Fig. 16: This is the only specimen found in Denmark with somewhat thickened sagittal bands, but the sagittal bands on this specimen are not as thick as those of Nannoceratopsis ambonis Drugg 1978 emend. Riding 1984.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Modified description:
Stover and Evitt, 1978, p. 215:
Synopsis:
Cysts proximate, compressed laterally, usually with two antapical horns, of which the ventral horn may be reduced or undeveloped; epicyst minute, hypocyst large; dorsal, ventral, and antapical surfaces narrow, lateral surfaces wide; archeopyle epicystal, probably analogous to Type APa.
Description:
Shape (in lateral view): Somewhat triangular with pronounced concavity between antapical horns; ventral horn may be reduced or absent. Outline of dorsal surface gently convex, that of ventral surface gently convex to straight, commonly with marked angularity at juncture of parasulcus and sagittal band. Epicyst minute; larger hypocst constitutes most of the cyst. Specimens show preferred orientation because of lateral flattening.
Wall relationships: Autophragm only.
Wall Features: No parasutural features. Low sagittal ridges may occur along the junctures of the lateral surfaces with the dorsal and ventral surfaces. Short transverse ridge may cross the ventral surface. Autophragm smooth to areolate.
Paratabulation: None indicated.
Archeopyle: Epicystal, probably analogous to combination archeopyle, Type APa; operculum usually attached ventrally.
Paracingulum: Expressed as a narrow, necklike, encircling, subapical band between the the minute epicyst and the large hypocyst.
Parasulcus: Part of the ventral surface extending from the ventral angularity; lateral and antapical limits may be defined by ridges.
Size: Intermediate to large.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Nannoceratopsis Deflandre, 1939a, emend. Evitt, 1961b, emend Piel and Evitt, 1980, emend. Poulsen, 1992b. Nannoceratopsis was emended by Poulsen (1992b, p.44) as follows, Cyst proximate, compressed laterally, lacking or with one, two or three antapical horns and lacking or with a ventral horn. In specimens with only one antapical horn, this may be reduced. In species with two antapical horns the ventral horn may be reduced. A ventral horn may be present at the end of the longitudinal groove area in the position of the two small hypocystal paraplates H1 and H4. This horn may point upwards. All other features as in Piel and Evitt (1980). These authors (p.102) provided the following synopsis: Cysts proximate, compressed laterally, usually with two antapical horns, of which the ventral horn may be reduced or undeveloped; epicyst minute, hypocyst large; dorsal, ventral, and antapical surfaces narrow, lateral surfaces wide. Paratabulation rarely visible, combining peridinialean arrangement in epicyst with dinophysialean in hypocyst. Archeopyle cingular, type C, involving paraplate 3c and possibly others.