LOPHOPHORATES (ECTOPROCTA AND BRACHIOPODA)
Adult bryozoans (Ectoprocta) and brachiopods (Brachiopoda) look nothing alike, but they both mature from similar larvae. The bryozoa grow by budding many clones to produce a colony whereas the brachiopods grow to large size individually, producing individuals rather than colonies.
The most common bryozoan fossils are the "stony" bryozoa from Paleozoic rocks. The photo below shows a typical branching form -- Batostoma(?) sp. from Upper Ordovician rocks in Kentucky. The scale bar is 1cm; note that the individual openings are very tiny, barely visible in the photo. (Photo by B. Carter.)
Mesozoic and Cenozoic rocks also have Ectoproct fossils, but these are generally more delicate and less common than in Paleozoic rocks.
The brachiopods are also much more common in Paleozoic than in younger rocks, though they do occur throughout the geologic column. Brachiopods have a bivalved shell -- that is, there are two parts (valves) that are hinged along one side to create the shell. The two valves are not mirror images of each other, but each half of one valve is the mirror image of the other half of the same valve. This is exactly opposit the symmetry pattern of most bivalved molluscs, which will be discussed in a later page.
The photo below shows two brachiopods from Upper Ordovician rocks. The upper specimen is Platystrophia precursor from the western suburbs of Nashville, TN. The lower is Rafinesquina alternata from near Maude, OH. The bilateral symmetry of the valves is obvious in both specimens. The scale bar is 1cm. (Photo by B. Carter.)
