Fig. 3
From: Patterns of the evolution of aptychi of Middle Jurassic to Early Cretaceous Boreal ammonites
VEGA/Tescan SEM (a–c, f, i) and microscopic (d, e, g, h, j, k) photographs of Upper Jurassic and Lower Cretaceous aptychi. Only j is coated with ammonium chloride. a–c Laevilamellaptychus sp., Rybaki, Upper Oxfordian, Serratum Zone, a specimen in private collection; b, c MSU 121/2, details of inner structure of aptychus; d, e, j, k Didayilamellaptychus (?) sp. Lower Aptian, Volgensis Zone, d (MSU 121/3) e (MSU 121/4)—Ulianovsk, j, k in situ record within the body chamber of Sinzovia; f–i Praestriaptychus sp., f MSU6070, Mikhalenino, Upper Oxfordian, Alternoides Zone, bed 8; g MSU 121/5, Ulianovsk, Lower Aptian, Volgensis Zone; h Gorodishi. MSUAP137, Lower Volgian, Puschi Zone, bed 1/6; i MSU 121/6, Kelevudagh Mt, Lower Hauterivian, bed 177