An enigmatic ammonite population from the late Callovian of Montreuil-Bellay (Maine-et-Loire, France)
Abstract
An enigmatic ammonite (Ammonoida, Ammonitida) population represented by ten immature specimens from the late Callovian (Pseudopeltoceras leckenbyi Horizon) of Montreuil-Bellay is documented in this work. No evident similarities can be found between the studied material and any previously described species overall, suggesting at first glance that this population represents a new taxon. However, a thorough literature review on ammonoid pathologies and a detailed investigation on the morphology and ornamentation of the specimens lead us to instead support the hypothesis that the studied population reflects abnormal specimens. More specifically, we suggest that the specimens described herein are genetically-induced abnormal (forma aegra circumdata) Taramelliceras taurimontanum Erni, 1934 specimens (or alternatively – although more unlikely – Granulochetoceras hungaricum Lóczy, 1915 specimens). In our opinion, additional material providing information on the adult morphology of this remarkable and extremely rare ammonite assemblage is required before completely ruling out the hypothesis that this population represents a new taxon.
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BibTeX
@article{jattiot2026enigmatic,
title = {{An enigmatic ammonite population from the late Callovian of Montreuil-Bellay (Maine-et-Loire, France)}},
author = {Romain Jattiot and Pierre-Yves Boursicot},
journal = {Geodiversitas},
year = {2026},
month = jul,
doi = {10.5252/geodiversitas2026v48a13},
url = {https://hal.science/hal-05760132v2},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - An enigmatic ammonite population from the late Callovian of Montreuil-Bellay (Maine-et-Loire, France)
AU - Romain Jattiot
AU - Pierre-Yves Boursicot
PY - 2026
DA - 2026/07/02
JO - Geodiversitas
DO - 10.5252/geodiversitas2026v48a13
UR - https://hal.science/hal-05760132v2
AB - An enigmatic ammonite (Ammonoida, Ammonitida) population represented by ten immature specimens from the late Callovian (Pseudopeltoceras leckenbyi Horizon) of Montreuil-Bellay is documented in this work. No evident similarities can be found between the studied material and any previously described species overall, suggesting at first glance that this population represents a new taxon. However, a thorough literature review on ammonoid pathologies and a detailed investigation on the morphology and ornamentation of the specimens lead us to instead support the hypothesis that the studied population reflects abnormal specimens. More specifically, we suggest that the specimens described herein are genetically-induced abnormal (forma aegra circumdata) Taramelliceras taurimontanum Erni, 1934 specimens (or alternatively – although more unlikely – Granulochetoceras hungaricum Lóczy, 1915 specimens). In our opinion, additional material providing information on the adult morphology of this remarkable and extremely rare ammonite assemblage is required before completely ruling out the hypothesis that this population represents a new taxon.
SN - 1280-9659
SN - 1638-9395
ER -