99 Evolution of Life in the Cambrian Seas: Biotic, Biogeochemical, and Sedimentological Contexts, Part I

This session is dedicated to studies that illuminate the biotic, geobiological, sedimentological, and geochemical contexts of the evolution of early animal life in the oceans, with a particular focus on the Cambrian Period.

Monday, 20 October 2025
8:00 AM - 12:00 PM
HBGCC, 304B

The fossil record of siliceous spicules can be taken at face value

Paper number: 99-3
Program: Technical Sessions
Time: 8:35 AM – 8:50 AM

Authors

Abstract

Evidence suggests sponge groups diverged in the Cryogenian, but their silicious spicule skeletons only appear in the fossil record after a hundred million year gap, a span termed the spicule gap. Due to their early branching position in animal phylogeny and the important role sponges play in regulating ocean chemistry through biomineralization and carbon burial, a taphonomically controlled global spicule gap would have major implications for the tempo and mode of changes to the Earth system as animals radiate. We find no evidence for a spicule gap. Rather, convergent evolution of siliceous spicules is likely as we find spicules evolved when they appear in the fossil record.  Siliceous skeletons, consequently, also evolve at the same geological time as all other types of animal skeletons.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-412497

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