Invertebrate zoologists consider the phyla Dicyemida, Orthonectida, Placozoa, Cycliophora, Entoprocta (Kamptozoa), Chaetognatha,
Pterobranchia, and Enteropneusta along with the order Seisonidae.
Interrelationships between Enteropneusta and
Pterobranchia have been controversial.
Fragments of acanthograptids, Desmograptus sp., ?Pfrogaptus sp., and some unidentified fragments of
Pterobranchia, are also present (Fig.
The phylum Hemichordata is divided into two classes:
Pterobranchia and Enteropneusta.
Graptolithina with Sections on Enteropneusta and
Pterobranchia. The Geological Society of America, Inc.; The University of Kansas, Boulder, Colorado and Lawrence, Kansas, 101 pp.
The deuterostome phylum Hemichordata is composed of three extant classes: the Enteropneusta are solitary worms, the
Pterobranchia are colonial tube-dwelling suspension feeders, and the Planktosphaeroidea are known only from their larvae.
In this research, a phylogeny based on 18S rDNA sequence data is used to test the putative homology of the feeding apparatuses found in the Lophophorata and
Pterobranchia. Patterson's (1, 2) three criteria of conjunction, similarity, and congruence constitute the framework for the test.