Trepostomida

Trepostomida is an extinct order of bryozoans that lived during the Ordovician, Silurian, Devonian, and Carboniferous periods. Bryozoans, also known as moss animals, are colonial invertebrates that secrete a rigid exoskeleton. Trepostomes are characterized by their zooecia, which are the individual chambers within the exoskeleton, typically having a rounded or oval shape in cross-section. These zooecia are often very small and numerous, forming a dense colony.

The colonies of trepostomes could take various forms, including branching, encrusting, or sheet-like structures. They are particularly abundant in Paleozoic marine fossil assemblages. A key feature used in the classification of trepostomes is the presence of mesopores, which are smaller, often irregularly shaped zooecia that may have served different functions, such as respiration or brood chambers.

The study of Trepostomida is important for understanding ancient marine ecosystems and paleoenvironmental conditions. Their fossilized remains can be found in rocks from shallow to moderately deep marine settings. The diversity of trepostome forms and their widespread distribution make them valuable index fossils for correlating rock layers from the Paleozoic era. Their extinction occurred before the Permian period.