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Morphological Evolution and Extinction of Eodiscids and Agnostoid Arthropods
Huarui Li1, Tao Dai2, Yanlong Chen1
1State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life and Environments, Department of Geology, Northwest University, Xi'an 710069, China.
Life (Basel, Switzerland)
|January 25, 2025
Summary
Agnostoid arthropods showed declining morphological diversity after the Cambrian Series 2, coinciding with significant geological and evolutionary events. Their extinction resulted from episodic reductions, not a single cause.
Area of Science:
- Paleontology
- Evolutionary Biology
- Geology
Background:
- Agnostoid arthropods and eodiscids existed during significant early Paleozoic geological events.
- The impact of these events on agnostoid evolution remains unclear.
Purpose of the Study:
- To investigate the evolutionary responses of agnostoids to early Paleozoic geological events.
- To reconstruct agnostoid morphospace occupation and diversity over time.
Main Methods:
- Geometric morphometrics was used to analyze agnostoid fossils.
- Morphospace occupation was reconstructed to track evolutionary changes.
Main Results:
- Maximum agnostoid morphospace occupation occurred in Cambrian Series 2.
- Declines in morphospace occupation correlated with major abiotic and biotic events, including the Botoman-Toyonian Extinctions (BTEs), Redlichiid-Olenellid Extinction Carbon Isotope Excursion (ROECE), Drumian Carbon Isotope Excursion (DICE), Steptoean Positive Carbon Isotope Excursion (SPICE), and the Great Ordovician Biodiversification Event (GOBE).
Conclusions:
- Agnostoid extinction was a gradual process of reduced morphological diversity, not a single event.
- The extinction was likely caused by a combination of factors rather than a singular abiotic or biotic trigger.
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