3 Cephalodiscus gracilis AF236798 -- Cephalodiscus densus EU728439 -- Cephalodiscus EU728440 -- nigrescens Rhabdopleuridae Rhabdopleura sp.
We were able to include three 16S rDNA sequences from the pterobranch genus Rhabdopleura in our analyses, as well as 18S rDNA data from two additional Rhabdopleura and three additional Cephalodiscus taxa.
We gratefully acknowledge Jon Norenburg and Darryl Felder for providing Rhabdopleura sp.
Phylogenetic analysis reveals that Rhabdopleura is an extant graptolite.
2009 Cephalodiscus EU728440 na na EU728440 nigrescens Rhabdopleura U15664 * na na Halanych, normani 1995 Echinodermata Asteriodea, DQ060776 DQ297073 AMCC 113321 Janies, 2005 Asterias unpublished forbesii Crinoidea, AY275891 na D1425 Cohen et al.
Ultrastructure of adult gonads and development and structure of the larva of Rhabdopleura normani (Hemichordata: Ptero-branchia).
Fine structure of the heart vesicle and pericardium in the pterobranch Rhabdopleura
Molecular sequence data suggest that the harrimaniid worms are more closely related to the colonial class Pterobranchia (including the genera Rhabdopleura
and Cephalodiscus), which also have paired protocoel ducts and pores, than they are to the ptychoderid worms (Balanoglossus and Ptychodera) (Cameron et al.
Given that the males of Cephalodiscus sibogae and all Rhabdopleura species have a single pair of arms (there are only two pterobranch genera; Atubaria is most likely a form of Cephalodiscus), the ancestral condition for pterobranchs is assumed, by parsimony, to be a single pair of arms because a single evolutionary event can account for the multiple arms in Cephalodiscus.
The entire 18S rDNA gene was aligned for all of the taxa with the exception of the Rhabdopleura normani sequence for which only the 5[prime] third of the 18S gene has been obtained.
Taxon Plumatella repens U12649 Bryozoan Terebratalia transversa U12650 Articulate Glottidia pyramidata U12647 Inarticulate Phoronis vancouverensis U12648 Phoronid Rhabdopleura normani U15664 Pterobranch Balanoglossus carnosus D14359 Enteropneust Antedon serrata D14357 Crinoid Asterias amurensis D14358 Seastar Artemia salina X01723 Crustacean Placopecten magellanicus X53899 Bivalve Branchiostoma floridae M97571 Cephalochordate Xenopus laevis X04025 Vertebrate Acanthopleura japonica X70210 Chiton Tenebrio molitor X07801 Insect Anemonia sulcata X53498 Cnidarian Sycon calcaravis D15066 Sponge