![]() Insofar as taxa cannot be contained within other taxa of equal rank, the phylum Myxozoa is abandoned and it is recommended that the group as a whole be removed from all protistan classifications and placed in a more comprehensive cnidarian system. Their "polar capsules" are redescribed as typical nematocysts bearing atrichous isorhiza. Reassessment of myxozoans as metazoans reveals terminal differentiation, typical metazoan cellular junctions, and collagen production. The results unequivocally support the inclusion of myxozoans as a clade of highly derived parasitic cnidarians, and as sister taxon to the narcomedusan Polypodium hydriforme. These morphological characters, in combination with small ribosomal subunit gene sequences, were used in a phylogenetic analysis in order to assess myxozoan origins. ![]() The ultrastructure of the development of myxozoans was critically re-examined in order to more fully explore the possibility of morphological synapomorphies with metazoan taxa. Thus, the group has remained in classifications as a protistan phylum in its own right. Systematists have failed to be decisive about myxozoan phylogenetic affinities, either finding the suggestion of a cnidarian connection to be preposterous or considering the recent suggestion of a relationship with nematodes to be an obvious failure of molecular phylogenetics. The notion that members of the phylum Myxozoa Grassé, 1970 do not properly belong in classifications of protists has frequently been suggested because the infective spores of these parasites are not unicellular. 596 57l.3'I4'014-dc21 97-20213 © The paper used in this publication meets the minimum requirements of the American National Standard for Permanence of Paper for Printed Library Materials Z39.48-1984. 596) Includes bibliographical references (p. cm.-(Smithsonian contributions to zoology no. ![]() Library of Congress Cataloging-in-Publication Data Thesaurus of sponge morphology / Nicole Boury-Esnault and Klaus Rutzler. SERIES COVER DESIGN: The coral Montastrea cavernosa (Linnaeus). OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded in the Institution's annual report, Annals of the Smithsonian Institution. The literature cited presents a historical perspective on similar attempts to create a precise terminology of sponge morphology and helps to further clarify the selected terms. The thesaurus will aid descriptions in future systematic papers, computerized data banks, and identification keys. Terms listed as rejected are those judged unsuitable, redundant, or preoccupied. Each entry is accompanied by a precise diagnosis and an illustration. Terms were selected and reviewed by an international group of 10 experts in sponge systematics, during several workshops. Definitions of microscopic features include aquiferous system, cytology, reproductive structures, skeletal architecture, and calcareous and siliceous spicules. Smithsonian Contributions to Zoology, number 596, 55 pages, 305 figures, 1997.-This is a vade mecum of terms for describing all aspects of sponge morphology, such as habit, surface structure, consistency, and anatomy. Our results support the upgrading of the calcareous sponge class to the phylum level.īoury-Esnault, Nicole, and Klaus Rutzler, editors. They also have consequences for basal metazoan classification, implying that the phylum Porifera should be abandoned. These results have important implications for our understanding of metazoan origins, because they suggest that the common ancestor of Metazoa was a sponge. Our results suggest that sponges are paraphyletic, the Calcarea being more related to monophyletic Eumetazoa than to the siliceous sponges (Demospongiae, Hexactinellida). The amplification products were cloned, sequenced and then aligned with previously reported sequences from other sponges and nonsponge metazoans and variously distant outgroups, and trees were constructed using both neighbour-joining and maximum parsimony methods. In order to allow critical evaluation of the interrelationships between the three sponge classes, and to resolve the question of mono- or paraphyly of sponges (Porifera), we used the polymerase chain reaction (PCR) to amplify almost the entire nucleic acid sequence of the 18S rDNA from several hexactinellid, demosponge and calcareous sponge species.
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