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Mancodinium morgensternii
Mancodinium morgensternii Tykoezinski et al., 2001, p.86,88, pl.2, figs.1a-c,2a-c,3a-c,4a-b,5; pl.3, figs.1a-b,2a-b,3a-b,4a-b,5a-b,6a-b,7-8,9a-b; pl.4,fig.14. Tykoezinski et al., 2001, pl.2, figs.1a-c.
Taxonomic junior synonym: Mancodinium tykoezinskii (name not validly published), according to Tykoezinski et al. (2001, p.86).
Age: Late Bathonian.
Original description (Tykoezinski et al., 2001)
Derivation of Name. Proposed in honour of Godfrey Morgenstern, consultant haematologist at The Christie Hospital, Manchester
Type Locality. Shipton-on-Cherwell Cement Works quarry (GR 477175).
Type Horizon. Abbotsbury Cornbrash Formation, Berry Member, Late Bathonian, C. discus Zone, C. discus Subzone.
Holotype. Slide SLC2/1, Ref. M14 (Plate 2, figures la-c).
Diagnosis. The cyst is normally sub-circular to subpolygonal in outline, often with an asymmetrical antapex offset dorsally and to the left. The cyst has an autophragm only, which bears a characteristic foveo-reticulate ornament.
The parasulcus and the ventral portion of the paracingulum are clearly defined and are normally smooth to scabrate. Limited paratabulation is expressed mainly on the epicyst by narrow grooves of thinned autophragm,
devoid of any ornament (?incipient archeopyle fissures). On the hypocyst, some of the post-cingular paraplates are
vaguely distinguished by differentiation of the surface ornament. The paratabulation formula as deduced from all
the specimens observed is as follows 41 ,4a, 7", Xc, as, Xs, fm, ?Xp, 3(+)'", X"" (+ indicates that although delimited plates were not observed it can be inferred that more do exist). The cyst has a compound epicystal archeopyle, formula 2-5P + (tA, tl).
Description. Shape: Ambitus is normally sub-circular to sub-polygonal, slightly dorso-ventrally compressed.
The paracingulum may be indented. The antapex of the cyst is often asymmetrically displaced dorsally and to the
left. The epicyst is notably smaller than the hypocyst. Wall relationships: The cyst wall consists of an autophragm only (inner pedium and outer luxurium, in the terminology of Below 1987a,b). The pedium is c. 0.5 um thick and the luxurium is foveo-reticulate with a maximum thickness of 4 µm. Wall features: The cyst bears a distinctive foveo-reticulate ornament comprising mixed size lumina from <0.5 to 3 um in diameter. The ornament is greatly reduced on the parasulcus and the ventral portion of the paracingulum, where it is usually smooth to scabrate with sparce, small fovea. The dorsal side of the paracingulum has well developed but small foveo-reticulate ornament. The luxurium expands beyond these areas but particularly on the hypocyst where it can reach a maximum thickness of 4 µm with lumina as large as 3 um. Paratabulation and-parasutural features: On the ventral surface of the cyst, the paracingulum and parasulcus are clearly defined as they lack the distinctive ornament found elsewhere on the cyst. On the dorsal surface of the cyst this is less clear as the surface ornament is continuous across the paracingulum. The parasulcus is relatively large and broad and extends about 2/3 the length of the hypocyst. A large bilobed flagellar scar (reflecting the two flagellar insertion points on the theca) having a diameter of 3-8 µm is normally present. The upper lobe is commonly displaced to the right. The paracingulum is indented and 5-8 um wide and is weakly laevorotatory, being offset by 0.1-0.5 its own width. Paratabulation is occasionally expressed on the epicyst by very narrow grooves of thinned autophragm devoid of any ornament, these may be incipient archeopyle fissures. These grooves are often imperceptible because either they have not formed, or they are obscured by the ornament. Occasionally, on the hypocyst, some of the postcingular paraplates can be vaguely identified by intratabular expansion of the surface ornament (luxurium), together with the development of low pandasutural ridges. This is most clearly visible on the ventral surface adjacent to the parasulcus where the first and last paraplates of the postcingular series can be distinguished. The paratabulation formula deduced from all the specimens observed is as follows 4',4a, 7", Xc, as, Xs, fm, ?Xp, 3(+)'", X"" (+ indicates that although delimited plates were not observed it can be inferred that more do exist). Archeopyle: The cyst develops a compound epicystal archeopyle, formula 2-5P+(tA, tl). Observations of the specimens recorded indicate that the paraplates become detached in a set sequence. The first paraplates lost are the precingular series which are lost individually (solvate). Paraplates 3" or 4" are lost first, followed by 2" and occasionally 5" and 6". Paraplates 5" and 6" frequently remain adherent to the cyst. Finally, the apical and anterior intercalary series are lost as one piece (foederate). Plate 2, figure 2c shows paratype 1 with a single foederate opercular piece, comprising eight paraplates (tA, tl), which has fallen into the hypocyst. Paraplates 1" and 7" may be involved in archeopyle formation but this has not been observed in the recorded specimens. Cyst Size: Oxfordshire specimens:
Length 33 & 38 um max. (Two complete specimens measured). Width min. 32(35)40 um max. (Holotype
30 Mm). 7 specimens measured. Cyst Size: Yorkshire specimens: Length min. 35(38)42 um max.
Width min. 31(37)41 Mm max- 11 specimens measured.
Remarks and Comparisons. This species is assigned to Mancodinium as it bears strong indications of a
Glenodinioid paratabulation pattern and the compound epicystal archeopyle characteristic of this genus. As such,
this species is an important discovery as it represents the stratigraphically youngest member of this genus, all other species having range tops in the early Bajocian. Mancodinium morgensternii can be differentiated from
all other species in the genus by it's foveo-reticulate ornament. Mancodinium semitabulatum subsp.semitabulatum Morgenroth 1970 has a gemmate/tuberculate surface ornament, M. semitabulatum ssp glabrum (Below) Lentin and Williams 1989 has a scabrate to finely granulate surface ornament, Mancodinium coalitum (Davies) Below 1987 has a granulate tuberculate ornament.The morphologically closest species to M. morgensternii is M. semitabulatum subsp fossatum (Below) Lentin & Williams 1989, which also has a fossulate/foveolate surface, but these elements are widely spaced and combined with tubercules unlike in M. morgensternii. In addition, the differentiated distribution of the ornament and lack of a clear apical horn also appear to be unique to this new species. Occurrence. Late Bathonian, C. discus Zone, C. discus Subzone, Abbotsbury Cornbrash Formation, Berry Member, Shipton-on-Cherwell, Oxfordshire, Tykoezinski (written commun., 1982) [as Mancodinium sp.A]: Early Callovian, M. herveyi to basal P. koenigi Zones, M. terebratus to lowermost K. gowerianus Subzones;
Abbotsbury Cornbrash Formation, Fleet Member (unita2)-Osgodby Formation, basal Redcliff Rock Member
(basal unit |3l), Yorkshire, Smith (written communication,1995) [as M. tykoezinskii]: Early Callovian, Abbotsbury
Cornbrash Formation, Fleet Member, Bicker borehole, Bailey et al. (in prep.).
Taxonomic junior synonym: Mancodinium tykoezinskii (name not validly published), according to Tykoezinski et al. (2001, p.86).
Age: Late Bathonian.
Original description (Tykoezinski et al., 2001)
Derivation of Name. Proposed in honour of Godfrey Morgenstern, consultant haematologist at The Christie Hospital, Manchester
Type Locality. Shipton-on-Cherwell Cement Works quarry (GR 477175).
Type Horizon. Abbotsbury Cornbrash Formation, Berry Member, Late Bathonian, C. discus Zone, C. discus Subzone.
Holotype. Slide SLC2/1, Ref. M14 (Plate 2, figures la-c).
Diagnosis. The cyst is normally sub-circular to subpolygonal in outline, often with an asymmetrical antapex offset dorsally and to the left. The cyst has an autophragm only, which bears a characteristic foveo-reticulate ornament.
The parasulcus and the ventral portion of the paracingulum are clearly defined and are normally smooth to scabrate. Limited paratabulation is expressed mainly on the epicyst by narrow grooves of thinned autophragm,
devoid of any ornament (?incipient archeopyle fissures). On the hypocyst, some of the post-cingular paraplates are
vaguely distinguished by differentiation of the surface ornament. The paratabulation formula as deduced from all
the specimens observed is as follows 41 ,4a, 7", Xc, as, Xs, fm, ?Xp, 3(+)'", X"" (+ indicates that although delimited plates were not observed it can be inferred that more do exist). The cyst has a compound epicystal archeopyle, formula 2-5P + (tA, tl).
Description. Shape: Ambitus is normally sub-circular to sub-polygonal, slightly dorso-ventrally compressed.
The paracingulum may be indented. The antapex of the cyst is often asymmetrically displaced dorsally and to the
left. The epicyst is notably smaller than the hypocyst. Wall relationships: The cyst wall consists of an autophragm only (inner pedium and outer luxurium, in the terminology of Below 1987a,b). The pedium is c. 0.5 um thick and the luxurium is foveo-reticulate with a maximum thickness of 4 µm. Wall features: The cyst bears a distinctive foveo-reticulate ornament comprising mixed size lumina from <0.5 to 3 um in diameter. The ornament is greatly reduced on the parasulcus and the ventral portion of the paracingulum, where it is usually smooth to scabrate with sparce, small fovea. The dorsal side of the paracingulum has well developed but small foveo-reticulate ornament. The luxurium expands beyond these areas but particularly on the hypocyst where it can reach a maximum thickness of 4 µm with lumina as large as 3 um. Paratabulation and-parasutural features: On the ventral surface of the cyst, the paracingulum and parasulcus are clearly defined as they lack the distinctive ornament found elsewhere on the cyst. On the dorsal surface of the cyst this is less clear as the surface ornament is continuous across the paracingulum. The parasulcus is relatively large and broad and extends about 2/3 the length of the hypocyst. A large bilobed flagellar scar (reflecting the two flagellar insertion points on the theca) having a diameter of 3-8 µm is normally present. The upper lobe is commonly displaced to the right. The paracingulum is indented and 5-8 um wide and is weakly laevorotatory, being offset by 0.1-0.5 its own width. Paratabulation is occasionally expressed on the epicyst by very narrow grooves of thinned autophragm devoid of any ornament, these may be incipient archeopyle fissures. These grooves are often imperceptible because either they have not formed, or they are obscured by the ornament. Occasionally, on the hypocyst, some of the postcingular paraplates can be vaguely identified by intratabular expansion of the surface ornament (luxurium), together with the development of low pandasutural ridges. This is most clearly visible on the ventral surface adjacent to the parasulcus where the first and last paraplates of the postcingular series can be distinguished. The paratabulation formula deduced from all the specimens observed is as follows 4',4a, 7", Xc, as, Xs, fm, ?Xp, 3(+)'", X"" (+ indicates that although delimited plates were not observed it can be inferred that more do exist). Archeopyle: The cyst develops a compound epicystal archeopyle, formula 2-5P+(tA, tl). Observations of the specimens recorded indicate that the paraplates become detached in a set sequence. The first paraplates lost are the precingular series which are lost individually (solvate). Paraplates 3" or 4" are lost first, followed by 2" and occasionally 5" and 6". Paraplates 5" and 6" frequently remain adherent to the cyst. Finally, the apical and anterior intercalary series are lost as one piece (foederate). Plate 2, figure 2c shows paratype 1 with a single foederate opercular piece, comprising eight paraplates (tA, tl), which has fallen into the hypocyst. Paraplates 1" and 7" may be involved in archeopyle formation but this has not been observed in the recorded specimens. Cyst Size: Oxfordshire specimens:
Length 33 & 38 um max. (Two complete specimens measured). Width min. 32(35)40 um max. (Holotype
30 Mm). 7 specimens measured. Cyst Size: Yorkshire specimens: Length min. 35(38)42 um max.
Width min. 31(37)41 Mm max- 11 specimens measured.
Remarks and Comparisons. This species is assigned to Mancodinium as it bears strong indications of a
Glenodinioid paratabulation pattern and the compound epicystal archeopyle characteristic of this genus. As such,
this species is an important discovery as it represents the stratigraphically youngest member of this genus, all other species having range tops in the early Bajocian. Mancodinium morgensternii can be differentiated from
all other species in the genus by it's foveo-reticulate ornament. Mancodinium semitabulatum subsp.semitabulatum Morgenroth 1970 has a gemmate/tuberculate surface ornament, M. semitabulatum ssp glabrum (Below) Lentin and Williams 1989 has a scabrate to finely granulate surface ornament, Mancodinium coalitum (Davies) Below 1987 has a granulate tuberculate ornament.The morphologically closest species to M. morgensternii is M. semitabulatum subsp fossatum (Below) Lentin & Williams 1989, which also has a fossulate/foveolate surface, but these elements are widely spaced and combined with tubercules unlike in M. morgensternii. In addition, the differentiated distribution of the ornament and lack of a clear apical horn also appear to be unique to this new species. Occurrence. Late Bathonian, C. discus Zone, C. discus Subzone, Abbotsbury Cornbrash Formation, Berry Member, Shipton-on-Cherwell, Oxfordshire, Tykoezinski (written commun., 1982) [as Mancodinium sp.A]: Early Callovian, M. herveyi to basal P. koenigi Zones, M. terebratus to lowermost K. gowerianus Subzones;
Abbotsbury Cornbrash Formation, Fleet Member (unita2)-Osgodby Formation, basal Redcliff Rock Member
(basal unit |3l), Yorkshire, Smith (written communication,1995) [as M. tykoezinskii]: Early Callovian, Abbotsbury
Cornbrash Formation, Fleet Member, Bicker borehole, Bailey et al. (in prep.).