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Leptodinium millioudii
Leptodinium millioudii (Sarjeant, 1963) Sarjeant, 1969
Originally Gonyaulax, subsequently (and now) Leptodinium. See also Gonyaulacysta (combination not validly published).
Holotype: Sarjeant, 1963, pl.1, figs.4-7; Jan du Chêne et al., 1986, pl.71, figs.4-7
Age: Oxfordian
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Original description: [Sarjeant, 1963]:
Gonyaulax millioudi n. sp.
PI. 1, fig. 4-7.
Diagnosis. -- A species of fossil Gonyaulax having a broadly ovoidal theca, with epitheca in the form of an obtuse, rounded cone and hypotheca hemi-spherical. There is no longitudinal furrow as such, the ventral surface being divided into six plates, one anterior ventral, two median ventral and one posterior ventral; tabulation therefore 4', 1a, lav, 6", 2mv, 6", 1p, 1pv, 1"'. Transverse furrow of moderate breadth, leavo-rotatory, divided by low ridges into five sections 4. Crests of moderate height: an apical prominence is formed by the junction of crests.
Description. -- The shell perceptibly granulate or are solid or very finely is yellowish-brown, not punctate. The crests are solid or very finely perforate. Four apical plates are present: plate 1' is broad at its anterior end but tapers to its posterior end, thus being roughly wedge-shaped. Six preequatorial plates are present, with plate 6" reduced to accommodate a small, rectangular anterior intercalary plate. The transverse furrow is moderately broad and forms a laevo-rotatory spiral such that its two ends differ in antero-posterior position by 1.5 times the furrow's breadth. The ventral region is occupied by six plates: large anterior and posterior ventral plates and two small median ventral plates.
Six post-equatorial plates are present, with plate 1'" reduce to accommodate a large, quadrate posterior intercalary plate. The antapical
plate is large and polygonal.
A precingular archaeopyle is developed, plate 3" being lost.
Holotype. -- V. 45427: lodged in the collections of the British Museum (Natural History), London.
Dimensions. -- Holotype; overall length 70.5 p, breadth 66 p, thecal length 65 , breadth 62.5 , height of crests 2 Po 5-6 5-6 (maximum height
attained at apex).
All other specimens seen were of closely similar dimensions.
Derivatio nominis. -- Named in honour of Dr. Marcel E. Millioud, Bataafse Internationale Petroleum Maats chappij N.V., The Hague, Netherlands.
Locus typicus. -- Rochette, Switzerland; section at roadside on the Baulmes Montfeloux road, a few metres beyond the tunnel under the railway line from Yverdon to Ste.-Croix.
Stratum typicum. -- Marly horizon with ammnonites Cardioceras cf. cordatum, Perisphinctes bernensis, etc., horizon 5 of Millioud, 1951, pp. 4-5.
(Oxfordian: Cardịoceras cordatum Zone).
Remarks. -- The specimens examnined were obtained from a sample collected by Dr. M. E. Millioud. (BIPM sample No MLO 276).
Gonyaulax millioudi n. sp. differs in its combination of thecal shape, crest character and tabulation, from all other described species. G. wetzeli
LEJEUNE-CARPENTIER 1939, from the Upper Cretaceous of Belgium, also has six ventral plates: however, it differs from G. millioudi in outline and in the size, shape and position of plate 1"'.
Originally Gonyaulax, subsequently (and now) Leptodinium. See also Gonyaulacysta (combination not validly published).
Holotype: Sarjeant, 1963, pl.1, figs.4-7; Jan du Chêne et al., 1986, pl.71, figs.4-7
Age: Oxfordian
------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Sarjeant, 1963]:
Gonyaulax millioudi n. sp.
PI. 1, fig. 4-7.
Diagnosis. -- A species of fossil Gonyaulax having a broadly ovoidal theca, with epitheca in the form of an obtuse, rounded cone and hypotheca hemi-spherical. There is no longitudinal furrow as such, the ventral surface being divided into six plates, one anterior ventral, two median ventral and one posterior ventral; tabulation therefore 4', 1a, lav, 6", 2mv, 6", 1p, 1pv, 1"'. Transverse furrow of moderate breadth, leavo-rotatory, divided by low ridges into five sections 4. Crests of moderate height: an apical prominence is formed by the junction of crests.
Description. -- The shell perceptibly granulate or are solid or very finely is yellowish-brown, not punctate. The crests are solid or very finely perforate. Four apical plates are present: plate 1' is broad at its anterior end but tapers to its posterior end, thus being roughly wedge-shaped. Six preequatorial plates are present, with plate 6" reduced to accommodate a small, rectangular anterior intercalary plate. The transverse furrow is moderately broad and forms a laevo-rotatory spiral such that its two ends differ in antero-posterior position by 1.5 times the furrow's breadth. The ventral region is occupied by six plates: large anterior and posterior ventral plates and two small median ventral plates.
Six post-equatorial plates are present, with plate 1'" reduce to accommodate a large, quadrate posterior intercalary plate. The antapical
plate is large and polygonal.
A precingular archaeopyle is developed, plate 3" being lost.
Holotype. -- V. 45427: lodged in the collections of the British Museum (Natural History), London.
Dimensions. -- Holotype; overall length 70.5 p, breadth 66 p, thecal length 65 , breadth 62.5 , height of crests 2 Po 5-6 5-6 (maximum height
attained at apex).
All other specimens seen were of closely similar dimensions.
Derivatio nominis. -- Named in honour of Dr. Marcel E. Millioud, Bataafse Internationale Petroleum Maats chappij N.V., The Hague, Netherlands.
Locus typicus. -- Rochette, Switzerland; section at roadside on the Baulmes Montfeloux road, a few metres beyond the tunnel under the railway line from Yverdon to Ste.-Croix.
Stratum typicum. -- Marly horizon with ammnonites Cardioceras cf. cordatum, Perisphinctes bernensis, etc., horizon 5 of Millioud, 1951, pp. 4-5.
(Oxfordian: Cardịoceras cordatum Zone).
Remarks. -- The specimens examnined were obtained from a sample collected by Dr. M. E. Millioud. (BIPM sample No MLO 276).
Gonyaulax millioudi n. sp. differs in its combination of thecal shape, crest character and tabulation, from all other described species. G. wetzeli
LEJEUNE-CARPENTIER 1939, from the Upper Cretaceous of Belgium, also has six ventral plates: however, it differs from G. millioudi in outline and in the size, shape and position of plate 1"'.