ASGP (2016), vol. 86: 17–28

ONTOGENY AND VARIABILITY IN RIBBING OF LATE VALANGINIAN LAMELLAPTYCHI (AMMONITINA)

Zdeněk VAŠÍČEK (1), Jaap KLEIN (2) & Nico M. M. JANSSEN (3)

1) Institute of Geonics, Academy of Sciences of the Czech Republic, Studentská 1768, CZ-70800 Ostrava-Poruba, Czech Republic; e-mail: zdenek.vasicek at ugn.cas.cz
2) Demmerik 12, NL-3645 EC Vinkeveen, the Netherlands; e-mail: jaap.klein at zonnet.nl
3) Waalstraat 156A, NL-3522 SV Utrecht, the Netherlands; e-mail: hibolithes at hotmail.com

Vašíček, Z., Klein, J. & Janssen, N. M. M., 2016. Ontogeny and variability in ribbing of Late Valanginian lamellaptychi (Ammonitina). Annales Societatis Geologorum Poloniae, 86: 17–28.

Abstract: Late Valanginian (Early Cretaceous) lamellaptychi of the genus Mortilletilamellaptychus were collected from seven ammonite-controlled sections in south-eastern France demonstrate distinct changes in ribbing during growth. Simpler juvenile ribbing, which is essentially uniform for all of the specimens studied, differs distinctly from the complicated arrangement of the adult ribs. Changes in ribbing morphology were observed in the five species studied, two of which were identified as new (i.e. Mortilletilamellaptychus heterocostatus sp. nov. and M. bicostatus sp. nov.).

Manuscript received 13 April 2015, accepted 25 January 2016