Irregular Shell Coiling in Monomorph Paleozoic Ammonoids

2026/04/01 by S. E. Vdovichenko
Earth and Planetary Sciences · Agricultural and Biological Sciences · #Paleontology and Stratigraphy of Fossils #Paleontology and Evolutionary Biology #Plant Diversity and Evolution

paper · doi:10.1134/s0031030126600782

Abstract

Paleozoic monomorph ammonoids with irregular coiling, different from normal planispiral coiling, are reviewed, with regard to their classification, geochronology and paleobiogeography. Irregular coiling is known in the Late Paleozoic ammonoids of the orders Clymeniida, Tornoceratida, and Goniatitida. The potential for this trait may have existed, unexpressed, in early ammonoids of the order Anarcestida. The highest diversity of irregularly coiled forms is recorded at the end of the Famennian (Late Devonian), and in the Bashkirian–Moscovian (Pennsylvanian). Possible biotic and abiotic causes of these peaks are discussed.

Citations

• Cephalopods in the marine ecosystems of the Paleozoic
• Permian ammonoids: Biostratigraphic, biogeographical, and ecological analysis
• Paedomorphosis of ammonoids as a result of sealevel fluctuations in the Late Devonian Wocklumeria Stufe
• THE LAZARUS AMMONOID FAMILY GONIATITIDAE, THE TETRANGULARLY COILED ENTOGONITIDAE, AND MISSISSIPPIAN BIOGEOGRAPHY
• An ammonoid from the Carboniferous of Peru
• Carboniferous Ammonoids of the Taimyr Peninsula
• The concept of ‘heteromorph ammonoids’
• The First Record of Soliclymenia paradoxa (Hexaclymeniidae, Ammonoidea) from the Upper Devonian of the Middle Urals

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