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Dinogymnium rotundum
Plate 4, Figures 20, 21, 23, 24
Holotype: Plate 4, Figure 21
Type Locality: Vergol outcrop, early Valanginian, Bed V94M, inostranzewi ammonite Zone, inostranzewi Sub-zone. Holotype: Slide V94M(schulze), E.F. D40.4.
Derivation of Name: From the Latin rotundus, round, spherical - in reference to the spherical shape.
Diagnosis: A small, proximate, acavate species with an approximately circular ambitus. The epi- and hypocyst are symmetrical with only minor narrowing towards the apices. The test wall is thin and smooth, without obvious trichocyst pores and lacks well-defined surface ridges, although very faint striations may be seen, restricted to the epicyst. The cingulum is broad and slightly indented and is expressed by clear transverse folds. The "archeopyle" is apical.
Dimensions: Holotype: 48 × 43 μm.
Overall: 51 (48) 46 μm × 46 (44) 43 μm.
Specimens measured - 3.
Remarks: The spheroidal shape and smooth surface of Dinogymnium rotundum, essentially lacking the clear surface ridges more typical of the genus, sets this species apart. The closest species, Dinogymnium circulos n. sp. can have a square ambitus (but not circular) and the striate, possibly penitabular "enclosures" of the latter species are unique.
Only three specimens of this species were recorded here, but it is considered sufficiently distinctive to include as a new species. These were from the early Valanginian, Beds V48M (neocomiensiformis Zone, neocomiensiformis Sub-zone) and V94M (inostranzewi Zone, inostranzewi Sub-zone), and late Valanginian, Bed V124M (base peregrinus Zone, peregrinus Sub-zone). The wide separation of these occurrences may reflect a significant age range but extreme rarity for this species.
Holotype: Plate 4, Figure 21
Type Locality: Vergol outcrop, early Valanginian, Bed V94M, inostranzewi ammonite Zone, inostranzewi Sub-zone. Holotype: Slide V94M(schulze), E.F. D40.4.
Derivation of Name: From the Latin rotundus, round, spherical - in reference to the spherical shape.
Diagnosis: A small, proximate, acavate species with an approximately circular ambitus. The epi- and hypocyst are symmetrical with only minor narrowing towards the apices. The test wall is thin and smooth, without obvious trichocyst pores and lacks well-defined surface ridges, although very faint striations may be seen, restricted to the epicyst. The cingulum is broad and slightly indented and is expressed by clear transverse folds. The "archeopyle" is apical.
Dimensions: Holotype: 48 × 43 μm.
Overall: 51 (48) 46 μm × 46 (44) 43 μm.
Specimens measured - 3.
Remarks: The spheroidal shape and smooth surface of Dinogymnium rotundum, essentially lacking the clear surface ridges more typical of the genus, sets this species apart. The closest species, Dinogymnium circulos n. sp. can have a square ambitus (but not circular) and the striate, possibly penitabular "enclosures" of the latter species are unique.
Only three specimens of this species were recorded here, but it is considered sufficiently distinctive to include as a new species. These were from the early Valanginian, Beds V48M (neocomiensiformis Zone, neocomiensiformis Sub-zone) and V94M (inostranzewi Zone, inostranzewi Sub-zone), and late Valanginian, Bed V124M (base peregrinus Zone, peregrinus Sub-zone). The wide separation of these occurrences may reflect a significant age range but extreme rarity for this species.