Fossil Sponges
The oldest animal fossils — sponges have filtered the world's oceans for over 600 million years, building reefs and leaving a record from the earliest Cambrian to today.
Overview
Sponges are the simplest living animals — sessile filter feeders with no nerves, muscles or organs — and among the oldest, with a fossil record reaching back toward the beginning of animal life. They built Earth's first reefs and still structure seafloor communities today.
Quick Facts
Key Characteristics
- •Body of canals and chambers circulating water for filter feeding
- •Skeleton of microscopic spicules (silica or calcite) and/or spongin fibres
- •No true tissues or organs — cells reorganise if the sponge is passed through cloth
- •Grow as encrusting sheets, vases, branches or massive reef frames
Fossil Record
Spicules preserve abundantly in cherts and limestones; whole sponges appear in Cambrian Burgess-type faunas, Devonian and Permian reef complexes, and Jurassic sponge reefs of Europe.
Global Distribution
Global — every marine basin through the Phanerozoic records sponges or their spicules.
Evolutionary & Scientific Importance
Sponges are central to debates on the origin of animals, are the earliest suspected reef builders (archaeocyathids), and their silica/calcite skeletons record the long-term chemistry of the oceans.