6533b7dcfe1ef96bd12730a4

RESEARCH PRODUCT

Reappraisal of ambulacral branching patterns in blastozoans

subject

description

6 pages; International audience; The type of ambulacral bifurcation is an important diagnostic character in primitive echinoderms. However this character is rarely used in blastozoan phylogenetic studies, whereas the corresponding character is well used in crinoid analyses. The main reason for this gap is the absence of definition of patterns for all blastozoans, resulting in terminological confusion. Although crinoid arms and blastozoan ambulacra are not homologous, the well-defined crinoid terminology has been used to describe the different topologies of ambulacral bifurcation. Unilateral and bilateral patterns have been recognized in blastozoans, and associated with the mineralization of the ambulacra. Four morphoclines are proposed to interpret the morphological relationships between the different patterns.