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First record of a bivalved larval shell in Early Cambrian tommotiids and its phylogenetic significance
Author(s) -
HOLMER LARS E.,
SKOVSTED CHRISTIAN B.,
LARSSON CECILIA,
BROCK GLENN A.,
ZHANG ZHIFEI
Publication year - 2011
Publication title -
palaeontology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.69
H-Index - 63
eISSN - 1475-4983
pISSN - 0031-0239
DOI - 10.1111/j.1475-4983.2010.01030.x
Subject(s) - neoteny , body plan , biology , paleontology , larva , phylogenetic tree , shell (structure) , cladistics , zoology , anatomy , ecology , fishery , gene , embryo , biochemistry , materials science , composite material
Brachiopods are marine Lophotrochozoa whose soft parts are enclosed in a bivalved shell. Although brachiopods are represented by a rich record from the Early Cambrian to the present, the origin of their bivalved body plan remains controversial. The Early Cambrian organophosphatic tommotiids Micrina and Paterimitra from Australia have been proposed as stem brachiopods. Here, we describe their earliest ontogeny, indicating that tommotiids possessed bivalved planktotrophic larvae. The curious combinations of characters in Micrina and Paterimitra indicate that they may belong to the stems of the Linguliformea and Rhynchonelliformea, respectively. The bivalved shell of adult living brachiopods may represent a plesiomorphic character retained from planktic tommotiid larvae; the crown group body plan of the Brachiopoda may have evolved through the paedomorphic retention of a bivalved larval state.