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Brachiopods: A Detailed Overview of Fossils and Evolution

Explore the classification, morphology, and internal features of Brachiopods. Learn about their shell ornamentation, lophophore types, and stratigraphic range from Early Cambrian to Recent. Identify Orders, like Orthida and Strophomenida, and discover their unique characteristics. Dive into the fascinating world of these marine filter feeders and their evolutionary journey.

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Brachiopods: A Detailed Overview of Fossils and Evolution

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  1. Brachiopods—Stuff to know • Bold font terms in text • Classification and stratigraphic ranges of Classes and Orders • Be able to identify correct Order for any given specimen (not necessary to identify genera) Fossils & Evolution—Brachiopoda

  2. Living brachiopods Fossils & Evolution—Brachiopoda

  3. Fossils & Evolution—Brachiopoda

  4. Fossils & Evolution—Brachiopoda

  5. Fossils & Evolution—Brachiopoda

  6. Fossils & Evolution—Brachiopoda

  7. Brachiopoda—Phylum overview • Solitary (but individuals often live in clusters) • Bivalved, with each valve being bilaterally symmetrical • Marine; mostly shallow marine (100–200m), but can occur in depths >2000m • Attached by pedicle or unattached; some infaunal • Filter feeders Fossils & Evolution—Brachiopoda

  8. Brachiopoda—Phylum overview • Possibly share a common ancestor with bryozoans (both groups possess a lophophore) • Stratigraphic range is Early Cambrian to Recent • Peak diversity in Ordovician, Devonian, Permian • Major reduction coincident with end-Permian mass extinction • Mesozoic peak diversity in Jurassic Fossils & Evolution—Brachiopoda

  9. Brachiopod diversity Fossils & Evolution—Brachiopoda

  10. Classification Fossils & Evolution—Brachiopoda

  11. Brachiopod morphology • Ventral valve (a.k.a. “pedicle valve”) • Lower or bottom valve • Dorsal valve (a.k.a. “brachial valve”) • Upper or top valve • Foramen = pedicle opening (largely or entirely in pedicle valve) • Anterior = end of shell opposite foramen • Posterior = end of shell containing foramen • Commissure = line along which two valves meet • Hinge = articulation mechanism • Teeth in pedicle valve; sockets in brachial valve Fossils & Evolution—Brachiopoda

  12. Brachiopod morphology Fossils & Evolution—Brachiopoda

  13. Hinge, teethand sockets Fossils & Evolution—Brachiopoda

  14. Brachiopod morphology • Shells may be highly ornamented • Growth lines (concentric) • Ribs (radial) • Fold (major raised area) • Sulcus (major depressed area) • Spines (sometimes extensions of growth lamellae; sometimes discrete structures) Fossils & Evolution—Brachiopoda

  15. Shell ornamentation Fossils & Evolution—Brachiopoda

  16. Features of the posterior region (pedicle and hinge region) • Pedicle opening • Delthyrium = triagular opening in pedicle valve • Notothyrium = smaller opening in brachial valve • Interarea = planar or curved surface between “beak” and hingeline • Ventral interarea • Dorsal interarea Fossils & Evolution—Brachiopoda

  17. Posterior region “beak” Fossils & Evolution—Brachiopoda

  18. Posterior region (cont.) Among articulate forms, those with a hinge line are strophic; those without are astrophic astrohpic strophic Fossils & Evolution—Brachiopoda

  19. Internal features • Body cavity houses major organs in posterior region of shell • Mantle cavity in anterior region of shell is mostly open space • Lophophore = ciliated, arm-like structure that serves for respiration and food gathering • Pedicle = muscular stalk for attachment to external objects or substrate • Adductor and diductor muscles Fossils & Evolution—Brachiopoda

  20. Internal soft anatomy Fossils & Evolution—Brachiopoda

  21. Musculature(valves tend toclose and stayclosed upondeath) Fossils & Evolution—Brachiopoda

  22. Lophophore • Usually a two-part structure, with each half (brachium; plural brachia) leading to the mouth • May be complexly looped or coiled • May be supported by a mineralized structure—spiralium (plural spiralia) or brachidium (plural brachidia) Fossils & Evolution—Brachiopoda

  23. Lophophore types brachia Fossils & Evolution—Brachiopoda

  24. Lophophore supports spiralia looped brachidia looped brachidia spiralia Fossils & Evolution—Brachiopoda

  25. Class Inarticulata • Lingula ia an example of a “living fossil” • Relatively low diversity since Ordovician time • Infaunal, with long fleshy pedicle Fossils & Evolution—Brachiopoda

  26. Inarticulate brachiopods(Lingula et al.) Fossils & Evolution—Brachiopoda

  27. Order OrthidaStrophic; unequally biconvex valves; usually with well-developed delthyrium/notothyrium openings in interareas Fossils & Evolution—Brachiopoda

  28. Order StrophomenidaStrophic; convex ventral valve/concave dorsal valve Fossils & Evolution—Brachiopoda

  29. Order StrophomenidaStrophic; convex ventral valve/concave dorsal valve(Suborder Productina) Fossils & Evolution—Brachiopoda

  30. Order PentameridaStrophic or astrophic; strongly biconvex with incurved beaks; open delthyrium with spoon-shaped structure (“spondylium”) Fossils & Evolution—Brachiopoda

  31. Order RhynchonellidaAstrophic; biconvex shell with dorsal fold and ventral sulcus Fossils & Evolution—Brachiopoda

  32. Order SpiriferidaVariable shell form; spiralia supports for lophophore(Suborder Spiriferina) Fossils & Evolution—Brachiopoda

  33. Order SpiriferidaVariable shell form; spiralia supports for lophophore(Suborder Atrypina) Fossils & Evolution—Brachiopoda

  34. Order SpiriferidaVariable shell form; spiralia supports for lophophore(Suborder Athyrina) Fossils & Evolution—Brachiopoda

  35. Order TerebratulidaAstrophic (rarely strophic); biconvex shell; loop supports for lophophore Cererithyris (Jurassic) Fossils & Evolution—Brachiopoda

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