The adaptation of mesozoic brachiopods to different environments

摘要: Abstract Seven different general habitats are recognized among the Mesozoic articulate Brachiopoda. Each of these is characterized by particular morphological adaptations as follows: ( 1 ) very shallow water sea-floors, usually transgressive and possibly littoral: large reinforced pedicle openings, thickened anterior margins, coarsely-ribbed rhynchonellids, sharply biplicate terebratulids; 2 sublittoral, sand-grade sea-floors without reefs: “ordinary” trilobate rhynchonelids “unusual” forms (spinose, cynocephalous, etc.), rectimarginate or gently plicate terebratulids, indentate zeilleriids, all living in dense colonies; 3 seafloors vicinity large, thick-shelled forms, sometimes elongate beaks, broadly assymmetrical rhynchonellids; 4 non-depositional sea-floors: coarsely ribbed smooth mergifer crura, opposite folds; 5 mud-grade generally smaller, thin-shlled, compressed finely ribbed, falcifer prefalcifer crura; 6 deeper (? bathyal) their equivalent calm, shallower water: axiniform, perforate sulcate smooth; 7 floating weed: small, thin-shelled rhynchonellids with crura. Several repeated unrelated groups. Functional interpretations suggested for some, but not all, features. A purely uniformitarian attitude shown to be inadequate. taxonomic anomalies demonstrated where genetic relationships adaptive changes apparently inextricably interwoven.