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Wittnaudinium minutum
From Fensome et al., 2019:
Wittnaudinium minutum Bucefalo Palliani and Riding, 1998, p.169–170, fig.10, nos.1–5; fig.11, nos.1–5.
Holotype: Bucefalo Palliani and Riding, 1998, fig.11. no.1.
Age: late Toarcian–Aalenian.
Holotype: Specimen W64.69 (1), England Finder coordinate N49-2 (Fig. 11 [1]).
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Original description: Bucefalo Palliani and Riding, 1998
Derivation of name : The specific epithet derives from the Latin minutus, meaning small or little.
Type locality and stratum: Wittnau borehole, Oberrhein, Southwest Germany (Fig. 1 ). Sample at 64.96 m core depth. Aalenian, L. opalinum ammonite Zone, P torulosum ammonite Subzone.
Diagnosis: A small species of Wittnaudinium n. g. with simple, hollow, distally tapering and pointed intratabular processes which indicate a standard gonyaulacacean paratabulation. Autophragm psilate.
Description: A species of Wittnaudinium n. g. which is small (of STOVER & EviTT 1978) in size. The autophragm is relatively thin and smooth; it is surmounted by apparently 24 homomorphic, hollow, distally tapering and pointed processes. Within a population, the processes are somewhat variable in proximal width and overall length. The processes are normally straight, however, may be rarely somewhat sinuous. The processes are arranged in an intratabular configuration of straight, latitudinal rows in the apical, precingular, paracingular, postcingular, posterior intercalary and antapical series (Fig. 10). The operculum (i.e. the apical paraplate series) appears to be compound. The processes on the precingular and postcingular paraplate series are located close to the apex and antapex respectively. The precingular and cingular intratabular processes are widely separated. This means that the paracingulum is located at a low latitudinal position on the cyst and that the precingular paraplates are longitudinally elongate (Fig. 11 [2, 3]). No parasutural features are present.
Dimensions (µm) :
Holotype: length (excluding operculum) - 24.5; width- 13.3; mean height of processes - 4.0.
Overall cyst length (excluding operculum) 26.6 (24.9) 22.2; Overall cyst width 13.3 (12.9) 11.1, 23 specimens measured
Stratigraphical range: Wittnaudinium minutum n. g. n. sp. is present in the late Toarcian (P aalensis ammonite Zone, P torulosum ammonite Subzone) to Aalenian (L. opalinum ammonite Zone, L. opalinum and L. comptum ammonite subzones) of the Wittnau borehole, Oberrhein, Southwest Germany (Fig. 3).
Comments: Wittnaudinium minutum n. g. n. sp. appears to be a marker for the Toarcian-Aalenian transition in southern Germany. Further work is needed to confirm its detailed stratigraphical range and geographical distribution. This species is the oldest chorate cyst in the geological record with intratabular processes. The Pliensbachian-early Toarcian genus Luehndea MoRGENROTH 1970 has gonal and intergonal processes. The range base of complex chorate forms is within the early Bathonian (Middle Jurassic) (RIDING et al. 1985).
Wittnaudinium minutum Bucefalo Palliani and Riding, 1998, p.169–170, fig.10, nos.1–5; fig.11, nos.1–5.
Holotype: Bucefalo Palliani and Riding, 1998, fig.11. no.1.
Age: late Toarcian–Aalenian.
Holotype: Specimen W64.69 (1), England Finder coordinate N49-2 (Fig. 11 [1]).
----------------------------------------------------------------------------------------------------------------------------------
Original description: Bucefalo Palliani and Riding, 1998
Derivation of name : The specific epithet derives from the Latin minutus, meaning small or little.
Type locality and stratum: Wittnau borehole, Oberrhein, Southwest Germany (Fig. 1 ). Sample at 64.96 m core depth. Aalenian, L. opalinum ammonite Zone, P torulosum ammonite Subzone.
Diagnosis: A small species of Wittnaudinium n. g. with simple, hollow, distally tapering and pointed intratabular processes which indicate a standard gonyaulacacean paratabulation. Autophragm psilate.
Description: A species of Wittnaudinium n. g. which is small (of STOVER & EviTT 1978) in size. The autophragm is relatively thin and smooth; it is surmounted by apparently 24 homomorphic, hollow, distally tapering and pointed processes. Within a population, the processes are somewhat variable in proximal width and overall length. The processes are normally straight, however, may be rarely somewhat sinuous. The processes are arranged in an intratabular configuration of straight, latitudinal rows in the apical, precingular, paracingular, postcingular, posterior intercalary and antapical series (Fig. 10). The operculum (i.e. the apical paraplate series) appears to be compound. The processes on the precingular and postcingular paraplate series are located close to the apex and antapex respectively. The precingular and cingular intratabular processes are widely separated. This means that the paracingulum is located at a low latitudinal position on the cyst and that the precingular paraplates are longitudinally elongate (Fig. 11 [2, 3]). No parasutural features are present.
Dimensions (µm) :
Holotype: length (excluding operculum) - 24.5; width- 13.3; mean height of processes - 4.0.
Overall cyst length (excluding operculum) 26.6 (24.9) 22.2; Overall cyst width 13.3 (12.9) 11.1, 23 specimens measured
Stratigraphical range: Wittnaudinium minutum n. g. n. sp. is present in the late Toarcian (P aalensis ammonite Zone, P torulosum ammonite Subzone) to Aalenian (L. opalinum ammonite Zone, L. opalinum and L. comptum ammonite subzones) of the Wittnau borehole, Oberrhein, Southwest Germany (Fig. 3).
Comments: Wittnaudinium minutum n. g. n. sp. appears to be a marker for the Toarcian-Aalenian transition in southern Germany. Further work is needed to confirm its detailed stratigraphical range and geographical distribution. This species is the oldest chorate cyst in the geological record with intratabular processes. The Pliensbachian-early Toarcian genus Luehndea MoRGENROTH 1970 has gonal and intergonal processes. The range base of complex chorate forms is within the early Bathonian (Middle Jurassic) (RIDING et al. 1985).