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Dinogymnium vergonsense
Dinogymnium vergonsense Londeix et al 1996
1990 Dinogymnium sp. A, Londeix, pp. 214-215, fig. S.38a; pl. XXVII, I
Holotype: Londeix et al 1996, Plate I, 1; Fig. 7a. Slide H12-20 Á-1 (England Finder reference: M 47/0).
Paratype: Londeix et al 1996, Plate I, 2. Slide H12-10 Á-1 (England Finder reference: Q 50/1).
Repository: D.G.O., Universite Bordeaux I.
Type locality: Vergons section (Alpes-de-HauteProvence, southeast France).
Occurrence: Vergons: Lower Hauterivian, Loryi ammonite zone (sample H12); Chatel-Saint-Denis: Lower Hauterivian, Radiatus ammonite zone equivalent (sample 152a).
Diagnosis: Proximate, acavate asymmetrical test with an elongate biconical shape and rounded poles. The single-layered wall is thick and its surface is smooth to scabrate. Trichocyst pores are absent. A relatively well-depressed narrow cingulum divides the test into two distinctive parts. The epitest is somewhat longer than the hypotest. It bears a few fine ribs or folds converging towards the unornamented apex, which, however, is not ribbed. Additional heterocostate ridges are absent. The hypotest is unornamented. The test seems to be wider in the precingular area compared with the postcingular area. The "archeopyle" is apical, recognizable as a triangular to circular opening at the apex, with the operculum being generally attached.
Dimensions: Holotype: Test length = 54 Ám; epitestal length = 33 Ám; hypotestal length = 20 Ám; test breadth = 26 Ám; cingulum height = 2 Ám; cingulum index = 0.61.
Paratype: Test length = 59 Ám; epitestal length = 33 Ám; hypotestal length = 25 Ám; test breadth = 23 Ám; cingulum height = 5 Ám; cingulum index = 0.57.
Chatel-Saint-Denis section: Test length=70 Ám; epitestal length = 42 Ám; hypotestal length = 25 Ám; test breadth = 30 Ám; cingulum height = 2 Ám; cingulum index = 0.60; number of measured specimens = 1.
Comparisons: Its distinctive elongate biconical shape, cingulum index and scarce to absent ridges on the epicyst only differentiate D. vergonsense from the other Lower Cretaceous species of Dinogymnium.
Dinogymnium sp. A Jain and Millepied, 1975 is morphologically very close to D. vergonsense Londeix, Pourtoy and Fenton, sp. nov. in terms of shape, ornamentation, and cingulum index. Nevertheless, Dinogymnium sp. A seems to have a much thinner wall and bears folds and ridges on both the epi- and the hypo-test, with a size nearly double to that of the Tethyan material. Dinogymnium digitus (Deflandre, 1935) Evitt et al., 1967, erected on the basis of a single specimen, seems to have a more elongate shape, an aproximately equilatent epi- and hypotest, and was described by Deflandre (1936, p. 12) as having longitudinally arranged "punctuations". Dinogymnium vergonsense Londeix, Pourtoy and Fenton, sp. nov. is somewhat similar to D. nelsonense (Cookson, 1956) Evitt et. al., 1967 in the shape of the asymmetrical test, and its cingulum index, in particular the paratype (Cookson, 1956, pl. 1, fig. 9). However, D. nelsonense has a much thinner wall, longitudinally arranged granulations and has folds on both the epi- and hypotest (note: the holotype and the two other designated paratypes are illustrated upside down; Cookson, 1956, pl. 1, figs. 8, 11).
Species formerly attributed to Dinogymnium are possessing a faintly ribbed or unornamented epitest and a typically unribbed hypotest which are further characterised by a bowl-shaped hypotest have been transferred to the genus Alisogymnium Lentin and Vozzhennikova, 1990: A. assamicum (Jain et al., 1975), A. deflandrei (Boltenhagen, 1977), A. evittii (Boltenhagen, 1977), and A. euclaense (Cookson and Eisenack, 1970).
Amphigymnium mitratum ( Vozzhennikova, 1967) Lentin and Vozzhennikova, 1990 has a very thin wall, a rounded antapex and a very short epitest (cingulum index=0.24).
1990 Dinogymnium sp. A, Londeix, pp. 214-215, fig. S.38a; pl. XXVII, I
Holotype: Londeix et al 1996, Plate I, 1; Fig. 7a. Slide H12-20 Á-1 (England Finder reference: M 47/0).
Paratype: Londeix et al 1996, Plate I, 2. Slide H12-10 Á-1 (England Finder reference: Q 50/1).
Repository: D.G.O., Universite Bordeaux I.
Type locality: Vergons section (Alpes-de-HauteProvence, southeast France).
Occurrence: Vergons: Lower Hauterivian, Loryi ammonite zone (sample H12); Chatel-Saint-Denis: Lower Hauterivian, Radiatus ammonite zone equivalent (sample 152a).
Diagnosis: Proximate, acavate asymmetrical test with an elongate biconical shape and rounded poles. The single-layered wall is thick and its surface is smooth to scabrate. Trichocyst pores are absent. A relatively well-depressed narrow cingulum divides the test into two distinctive parts. The epitest is somewhat longer than the hypotest. It bears a few fine ribs or folds converging towards the unornamented apex, which, however, is not ribbed. Additional heterocostate ridges are absent. The hypotest is unornamented. The test seems to be wider in the precingular area compared with the postcingular area. The "archeopyle" is apical, recognizable as a triangular to circular opening at the apex, with the operculum being generally attached.
Dimensions: Holotype: Test length = 54 Ám; epitestal length = 33 Ám; hypotestal length = 20 Ám; test breadth = 26 Ám; cingulum height = 2 Ám; cingulum index = 0.61.
Paratype: Test length = 59 Ám; epitestal length = 33 Ám; hypotestal length = 25 Ám; test breadth = 23 Ám; cingulum height = 5 Ám; cingulum index = 0.57.
Chatel-Saint-Denis section: Test length=70 Ám; epitestal length = 42 Ám; hypotestal length = 25 Ám; test breadth = 30 Ám; cingulum height = 2 Ám; cingulum index = 0.60; number of measured specimens = 1.
Comparisons: Its distinctive elongate biconical shape, cingulum index and scarce to absent ridges on the epicyst only differentiate D. vergonsense from the other Lower Cretaceous species of Dinogymnium.
Dinogymnium sp. A Jain and Millepied, 1975 is morphologically very close to D. vergonsense Londeix, Pourtoy and Fenton, sp. nov. in terms of shape, ornamentation, and cingulum index. Nevertheless, Dinogymnium sp. A seems to have a much thinner wall and bears folds and ridges on both the epi- and the hypo-test, with a size nearly double to that of the Tethyan material. Dinogymnium digitus (Deflandre, 1935) Evitt et al., 1967, erected on the basis of a single specimen, seems to have a more elongate shape, an aproximately equilatent epi- and hypotest, and was described by Deflandre (1936, p. 12) as having longitudinally arranged "punctuations". Dinogymnium vergonsense Londeix, Pourtoy and Fenton, sp. nov. is somewhat similar to D. nelsonense (Cookson, 1956) Evitt et. al., 1967 in the shape of the asymmetrical test, and its cingulum index, in particular the paratype (Cookson, 1956, pl. 1, fig. 9). However, D. nelsonense has a much thinner wall, longitudinally arranged granulations and has folds on both the epi- and hypotest (note: the holotype and the two other designated paratypes are illustrated upside down; Cookson, 1956, pl. 1, figs. 8, 11).
Species formerly attributed to Dinogymnium are possessing a faintly ribbed or unornamented epitest and a typically unribbed hypotest which are further characterised by a bowl-shaped hypotest have been transferred to the genus Alisogymnium Lentin and Vozzhennikova, 1990: A. assamicum (Jain et al., 1975), A. deflandrei (Boltenhagen, 1977), A. evittii (Boltenhagen, 1977), and A. euclaense (Cookson and Eisenack, 1970).
Amphigymnium mitratum ( Vozzhennikova, 1967) Lentin and Vozzhennikova, 1990 has a very thin wall, a rounded antapex and a very short epitest (cingulum index=0.24).