TY - JOUR
T1 - Dimorphism in the Early Cenomanian (Late Cretaceous) Ammonoid Parajaubertella
AU - Shigeta, Yasunari
AU - Maeda, Haruyoshi
AU - Sakai, Toshihiro
N1 - Funding Information:
I am deeply indebted to the University Museum, the University of Tokyo (Tokyo) and the Kyushu University Museum (Fukuoka) for kindly providing the opportunity to examine the type specimens. I thank R. Hoffmann (Ruhr University, Bochum), A. Misaki (Kitakyushu Museum of Natural History and Human History, Kitakyushu) and associate editor K. Tanabe (University Museum, University of Tokyo, Tokyo) for valuable comments on the first draft. Thanks are extended to the Northern Sorachi Bureau of the Sorach Forestry Office for their cooperation in the field and to Jim Jenks (West Jordan, Utah) for his helpful suggestions and improvement of the English text.
Publisher Copyright:
© by the Palaeontological Society of Japan.
PY - 2023/3/1
Y1 - 2023/3/1
N2 - Ontogenetic development of ornamentation and whorl geometry of the Cretaceous ammonoids Parajaubertella kawakitana and P. zizoh are studied based on well-preserved specimens collected from the lower Cenomanian in the Horokanai area, Hokkaido, Japan. Our results indicate that their comparably sized immature stages share identical ornamentation and shell morphology, while the size of their adult shells is distinctly bimodal. They also share the same stratigraphic ranges in the lower Cenomanian and have overlapping geographic distributions in Northwest Pacific region, and lastly, they co-occur in the same concretions. This evidence strongly suggests that the two taxa should be considered as dimorphs, microconch and macroconch of a single species, which is herein described as P. kawakitana.
AB - Ontogenetic development of ornamentation and whorl geometry of the Cretaceous ammonoids Parajaubertella kawakitana and P. zizoh are studied based on well-preserved specimens collected from the lower Cenomanian in the Horokanai area, Hokkaido, Japan. Our results indicate that their comparably sized immature stages share identical ornamentation and shell morphology, while the size of their adult shells is distinctly bimodal. They also share the same stratigraphic ranges in the lower Cenomanian and have overlapping geographic distributions in Northwest Pacific region, and lastly, they co-occur in the same concretions. This evidence strongly suggests that the two taxa should be considered as dimorphs, microconch and macroconch of a single species, which is herein described as P. kawakitana.
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U2 - 10.2517/PR220023
DO - 10.2517/PR220023
M3 - Article
AN - SCOPUS:85150240614
SN - 1342-8144
VL - 27
SP - 396
EP - 416
JO - Paleontological Research
JF - Paleontological Research
IS - 4
ER -