Rhynchonellata

Rhynchonellata is a class of brachiopods, a group of marine invertebrates that possess a hinged shell. They are characterized by their distinctive, often pointed, shell shape, which is typically wider than it is long. Rhynchonellata are among the most diverse and abundant brachiopod groups, with a fossil record spanning over 500 million years. They are found in a variety of marine environments, from shallow water to deep-sea habitats, and have played an important role in marine ecosystems throughout their evolutionary history.

Kraussina rubra

Terebratulina retusa

Terebratulina meridionalis

Argyrotheca Cuneata – Argyrotheca cuneata

Common Names

Rhynchonellata are commonly referred to as "rhynchonellid brachiopods." However, they lack any other colloquial names.

Characteristics

Rhynchonellata are characterized by the following features:

  • Biconvex shell: Their shell is wider than it is long, with both valves (top and bottom) being curved outwards.
  • Pointed beak: The shell typically has a pointed beak, or "rostrum," that projects forward.
  • Brachial valve: The top valve (brachial valve) is usually smaller than the bottom valve (pedicle valve).
  • Pedicle valve: The bottom valve (pedicle valve) is typically larger and may have a pedicle opening, which is a small hole used for attaching the brachiopod to the substrate.
  • Internal structures: Rhynchonellata possess a unique internal structure called a "loop," which is a supporting structure for the brachiopod's feeding apparatus.
  • Lophophore: Rhynchonellata, like all brachiopods, possess a lophophore, which is a crown of ciliated tentacles that they use to filter food from the water.

Environments

Rhynchonellata inhabit a variety of marine environments, including:

  • Shallow water: Many rhynchonellid species live in shallow water habitats, such as reefs, seagrass beds, and sandy bottoms.
  • Deep-sea: Others thrive in deeper waters, even down to the abyssal plain.
  • Various substrates: Rhynchonellata can attach to a variety of substrates, including rocks, shells, and even other brachiopods.

References

For more detailed information about Rhynchonellata, please refer to the following resources: