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Kimmeridgian dimorphic pairs
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Sexual dimorphism in the "Marls of St. Doulchard"
The sexual dimorphism also applies to some ammonites of the kimmeridgian marls of the department of Cher. It concerns all the three families - Aspidoceratidae, Aulacostephanidae, Perisphinctidae - present in these deposits. Being given the relative small number and especially the very bad preservation of many species, we restrict this page only to a small faunal insight.
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Aspidoceras caletanum (Opp.) M Ø 251 mm
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Aspidoceras caletanum (Opp.) m Ø 128 mm
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Orthaspidoceras schilleri (Opp.) m Ø 122 mm (Unfortunately, this ammonite is not very well preserved.)
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Orthaspidoceras schilleri (Opp.) M Ø 200mm
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Microconque (m) :
This term is used for the smaller shell of a dimorphic pair, probably the male. When complet, the microconch often has lappets at the aperture.
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We are seeking.....
A. (Aulacostephanoceras) eudoxus ( d' Orb.) M
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A. (Aulacostephanoceras) eudoxus ( d' Orb.) m Ø 54 mm with starting lappets
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Perhaps a microconch ?
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Sutneria eumela (d'Orb.) Ø 19 mm
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Macroconque (M) :
The bigger shell of the dimorphic pair, with simple aperture, is called macroconch. It is probably the female.
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