First record of a bivalved larval shell in Early Cambrian tommotiids and its phylogenetic significance

2011/01/12 by LARS E. HOLMER, Lars E. Holmer, Christian B. Skovsted +7 · 4 citations
Earth and Planetary Sciences · Agricultural and Biological Sciences · #Marine Biology and Ecology Research #Cephalopods and Marine Biology #Paleontology and Stratigraphy of Fossils

paper · pdf · doi:10.1111/j.1475-4983.2010.01030.x

Abstract

Abstract: 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.

Citations

• Shell structure, ontogeny and affinities of the Lower Cambrian bivalved problematic fossil <i>Mickwitzia muralensis</i> Walcott, 1913
• Tommotiids from the Lower Cambrian of South China

Cited by

• Scleritome construction, biofacies, biostratigraphy and systematics of the tommotiid <i>Eccentrotheca helenia</i> sp. nov. from the Early Cambrian of South Australia
• Tommotiids from the early <scp>C</scp>ambrian (<scp>S</scp>eries 2, <scp>S</scp>tage 3) of <scp>M</scp>orocco and the evolution of the tannuolinid scleritome and setigerous shell structures in stem group brachiopods
• The Problem of Axial Organization and Body Plan of Brachiopods in Phylogeny
• Partially preserved cornulitid feeding apparatuses from the lowest Silurian of South China support the lophophorate affinities of this enigmatic group

Related

• A Stem Group Brachiopod From The Lower Cambrian: Support For A <i>Micrina</i> (Halkieriid) Ancestry
• Shell structure, ontogeny and affinities of the Lower Cambrian bivalved problematic fossil <i>Mickwitzia muralensis</i> Walcott, 1913
• Exceptionally preserved<i>Mickwitzia</i>from the Indian Springs Lagerstätte (Cambrian Stage 3), Nevada
• Sclerite fusion, ultrastructure, micro‐ornament and homology in early Cambrian eccentrothecimorph tommotiids
• Early ontogeny and other possible molluscan traits in hyolith biology and anatomy