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Recent advances in heteromorph ammonoid palaeobiology
René Hoffmann1, Joshua S Slattery2, Isabelle Kruta3
1Institut für Geologie, Mineralogie und Geophysik, Ruhr-Universität Bochum, Bochum, 44801, Germany.
Biological Reviews of the Cambridge Philosophical Society
|January 13, 2021
Summary
Heteromorph ammonoids, with their unique coiled shells, evolved convergently. This study reveals their anatomy, diet, and ecological roles, explaining their extinction after the Chicxulub impact.
Area of Science:
- Paleobiology
- Evolutionary Biology
- Marine Biology
Background:
- Heteromorphs are ammonoids with non-planispiral or detached coiled shells, evolving convergently multiple times.
- Previous research has laid the groundwork, but a comprehensive understanding of heteromorph palaeobiology remains incomplete.
Purpose of the Study:
- To synthesize current knowledge on heteromorph ammonoid palaeobiology.
- To reconstruct their anatomy, buoyancy, locomotion, diet, ecology, and extinction patterns.
Main Methods:
- Analysis of fossil records.
- Phylogenetic bracketing with extant cephalopods (nautiloids, coleoids).
- Physical and virtual modeling.
Main Results:
- Heteromorphs possessed 10 arms, lacked suckers/hooks, and had an aptychus-type jaw.
- Diet varied from microphagous to zooplanktic, with some forms as suspension feeders.
- Buoyancy control was effective; locomotion varied, impacting benthic prey access.
- Habitat preferences shifted through geological time.
- Extinction linked to the Chicxulub impact, with heteromorphs persisting briefly.
Conclusions:
- Heteromorph ammonoids exhibited diverse adaptations in anatomy and ecology.
- Their life history traits, including small hatchling size and planktotrophy, contributed to their extinction.
- Phylogenetic bracketing provides crucial insights into their biology.
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