Fossil Brachiopods
Lamp shells — the dominant shelly invertebrates of Palaeozoic seas, with over 30,000 described fossil species and a 500-million-year record.
Overview
Brachiopods — lamp shells — are marine animals with two shells that enclose a filter-feeding lophophore. Though unfamiliar today, they were the dominant shelly animals of Palaeozoic seas, with over 30,000 described fossil species and a living remnant of a few hundred.
Quick Facts
Key Characteristics
- •Two valves of unequal size — dorsal and ventral (unlike clam's mirror-image left/right)
- •Most attached by a fleshy pedicle through a hole in the pedicle valve
- •Loop-supported lophophore filters food from water currents
- •Articulate hinges with teeth and sockets in the dominant Palaeozoic groups
- •Lingula, essentially unchanged since the Ordovician, is a classic 'living fossil'
Fossil Record
Robust calcitic shells preserve extremely well — some limestone beds are made largely of brachiopods. Famous occurrences include the Cincinnati Series (Ordovician, Ohio/Indiana), Devonian rocks of New York and England, and Carboniferous–Permian beds worldwide.
Global Distribution
Global — brachiopod shells are among the most abundant fossils in Palaeozoic marine rocks on every continent.
Evolutionary & Scientific Importance
Brachiopods are premier Palaeozoic index fossils, recording mass extinctions (especially the end-Ordovician and end-Permian), palaeoenvironments, and predation through shell-drilling and repair scars.