| Measurements | D mm | H/D | T/D | O/D | H/T |
|---|---|---|---|---|---|
| CP-41 | 54 | 0.44 | 0.43 | 0.31 | 1.04 |
| Holotype | 75 | 0.44 | 0.41 | 0.29 | 1.06 |
| CP-49 | 91 | 0.43 | 0.42 | 0.29 | 1.04 |
| Age | Origin |
|---|---|
|
Lower Albian D. inaequinodum Malagasy zone |
Malandiandro outlier Boeny Region Madagascar |
Description. Specimen preserved in oxidized glauconitic sandstone with its bronzed test. Whorls slightly compressed, half-overlapping, and increasing very rapidly in height (H/h ≈ 2.5). Broad umbilicus clearly exposing the inner whorls. The beginning of the last whorl is subcircular, with an umbilical wall at 45° without noticeable rim. The cross-section then becomes broadly ovoid, with more convergent flanks and a slightly pinched venter. The umbilical wall rises, becomes steeper (70°), and develops an increasingly distinct shoulder. Eight very fine and shallow constrictions are noted on the last whorl. They are radial, except for a forward shift on the umbilical shoulder. They have a steep posterior slope and a gentle anterior slope. Clearly visible on the inner whorls, they get closer but diminish on the last whorl. Between these constrictions, the test is adorned with very fine and closely spaced striations of the same course.
Remarks. E. numidum sensu stricto is known as small pyritic ammonites in the Middle Aptian (Gargasian) of the Mediterranean region; see Gérard Thomel's Atlas of Aptian Ammonites. Young specimens often have a slightly depressed whorl section, and the overlap ratio increases slowly with age. Our specimens nos. 41 and 49, however, come from the Lower Albian of Madagascar and correspond to the malandiandrensis variety of Collignon (1963, p. 15 and fig. 1056). This variety is distinguished with age by whorls that increase very rapidly in height, constrictions that diminish and get closer, more convergent flanks giving a sub-triangular or ovoid whorl section, and an umbilical wall whose slope becomes more pronounced. The table shows that its proportions are quite stable. Rare Malagasy specimens reaching 37 cm in diameter have been found. To the best of my knowledge, E. numidum is not present in the Upper Aptian (Clansayesian): the Albian variety of Collignon may be a new species.