The Proterostomata have some characteristics in common that cause it to be classified as a Subkingdom (Margulis and Schwartz, 1998). Some of these characteristics include the true coelom, as mentioned before, the presence of trochophore larva, and the presence of lophophores (Holt, 2000). These characteristics differ with that of the Subkingdom Pseudocoelomata because they have a pseudocoelom and do not have true lophophores (Holt, 2000).

In a pseudocoelom, the internal body cavity is in between the outer body wall and the digestive tract (Margulis and Schwartz, 1998). While in a coelom, the body cavity has all organs systems contained within the membrane, and it lies between the outer body wall and the gut (Holt, 2000; Margulis and Schwartz, 1998).

Ectoprocta is classified by itself because, according to Margulis and Schwartz (1998), there is a disappearance of the larval stage during metamorphosis, therefore, it can not be completely certain that the Ectoprocta has a true coelom. It does however have a true lophophore, and that is why it is placed in the Subkingdom Lophophorates by Margulis and Schwartz (1998) and Szuch, et. al. (2000).

A main difference in comparing the two Phyla was that Ectoprocta have an anus on the lophophore and it is not considered to be true because it does surround both the mouth and the anus (Pennack,1953; Margulis and Schwartz, 1998). While in the Ectoprocta the lophophore is true because it only surrounds the mouth (Margulis and Schwartz 1998).

A true lophophore is a round ridge that has slender tentacles which surround the mouth (Hickman 1973). Although the Ectoprocta resemble the Entoprocta since they each have a basal stalk surrounded by tentacles, the evidence specified above shows that the Entoprocta's lophophores are not true (Margulis and Schwartz, 1998). Proterostomes and Pseudoceolomates do have characteristics in common including a complete digestive tract as well as bilateral symmetry (Holt, 2000).

We examined the classification of the Ectoprocts to determine whether or not reclassification into its own superphylum was necessary.

.

Organisms Examined-
We investigated 25 genera for our cladistic analysis of the Phylum Ectoprocta. Of the 25 genera considered, we chose seven from three classes in the phylum Ectoprocta in order to represent the whole phylum. We then chose six from four phyla of the Proterostomes, nine from five phyla of the Pseudocoelomates, and three from the subkingdom Lophophorates. These genera and the sources used to obtain the information about the characters are in Table 1.

Table 1. This table contains a list of the genera studied along with the sources of information used. H = Holt (2000), MS = Margulis and Schwartz (1998), HC = Hickman (1973), SU = Storer and Usinger (1965).
 

Phylum	Genera	Literature Cited
Ectoprocta	Cristatella	H, HC, MS
Ectoprocta	Lophopus	H, HC, MS
Ectoprocta	Plumatella	H, HC, MS
Ectoprocta	Crisia	H, HC, MS
Ectoprocta	Victorella	H, HC, MS
Ectoprocta	Microporella	H, HC, MS
Ectoprocta	Bugula	H, HC, MS
Annelida	Dina	H, HC, MS
Mollusca	Nautilus	H, MS
Crustacea	Lucifer	H, MS
Chelicerata	Limulus	H, MS
Mollusca	Octopus	H, MS
Annelida	Nereis	H, MS
Entoprocta	Loxosoma	H, MS
Entoprocta	Urnatella	H, MS
Kinorhycha	Pycnnophyes	H, MS
Nematoda	Trichuris	H, MS
Rotifera	Seison	H, MS
Nematomorpha	Nectonema	H, MS
Rotifera	Rotaria	H, MS
Brachiopoda	Crania	HC, MS, SU
Brachiopoda	Lingula	HC, MS, SU
Phoronida	Phonois	HC, MS, SU
Entoprocta	Barentsia	H, MS, SU
Entoprocta	Pedicellina	H, MS, SU

Characters Examined-
As displayed in Table 2, we chose 20 characters and their varying states in order to examine relationships among our selected genera. Although we selected most of these characters based on anatomical features, we considered reproductive and developmental characters as well. We chose these characters because they best relate the genera to each other. We did not weight the characters in order to prevent bias within our cladogram. Table 2 displays the various states of our characters.

Table 2: This table displays the 20 characters used to examine the genera in Table 1 and their states. None of the characters were weighted.
 

Character	States
Segmentation	Absent Present
Digestive Tract	Complete Incomplete Degenerate
Mouth	Absent Present
Coelom	True Pseudocoelom
Nephridia	None Protonephridia Renette Cells Metanephridia Nephridia
Nerve Cord	Absent Present
Trochophore	Absent Present
Tentacles	Absent Present
Hydrostatic Skeleton	Absent Present
Retractor Muscles	Absent Present
Reproductive System	Monoecious Dioecious
Stomach	Absent Present
Development	Larval Direct
Gills	Absent Present
Anus	Absent Terminal Subterminal
Eyes	Absent Simple Compound Eye spots Simple and compound
Bristles	Absent Present
Foot	Absent Present
Cuticle	Absent Present
Jaws	Absent Present

Constructing the Phylogram-
We produced our phylogram, as shown in Figure 1, by using the information presented in Tables 1 and 2, and MacClade 3.08 (Maddison and Maddison 1999), we were able to classify our 25 genera due to similarities within the character states. We did not weight the characters in order to prevent bias. We then manipulated the branches to generate the most parsimonious tree (Figure 1).
 

Hickman (1973) states that Ectoprocta and Entoprocta are two groups that have been classified in the phylum Bryzoa. However, an alternate classification separates Ectoprocta and Entoprocta into two phyla (Hickman, 1973). One explanation for this separation is the true coelom of Ectoprocta versus the pseudocoelom of Entoprocta (Hickman 1973, Holt, 2000). Another reason for the separation is the differences in embryological development and the presence of a true lophophore in Ectoprocta but not in Entoprocta (Hickman, 1973).

We have come to the conclusion that Ectoprocta should not be classified with Pseudocoelomates, Proterostomes, or Lophophorates.

Figure 1 verifies our conclusion that Ectoprocta should be classified separate from the Pseudocoelomates, the Protostomes, and the Lophophorates. Our cladogram branches into four separate clades. Clade one shows five similar genera classified as Psuedocoelomates. Of the four genera of Entoprocts, two are out-groups and two represent clade two. Clade three shows seven similar genera classified as the superphyla Ectoprocta. Clade four consists of six genera from Proterostomes and three genera from Lophophorates. In Ectoprocta, the disappearance of the larval stages during metamorphosis causes uncertainty on whether or not they have a pseudo or true coelom (Margulis and Schwartz, 1998). As shown in the cladogram, Ectoprocta has fewer derived characteristics from the common ancestor and this is due to the uncertainty of whether or not they have a pseudo or true coelom.

Proposed Taxonomy-
Our taxonomy is an investigation of the Phylum Ectoprocta to resolve whether it should be classified in the Subphyla Pseudocoelomates or Subphyla Proterostomes. Upon examining our tree, we found that our results disagreed with all other proposed taxonomy. The Superphylum Ectoprocta is separate from Pseudocoelomates, Proterostomes, and Lophophorates.

The Ectoprocta are classified separate from the Pseudocoelomates, Proterostomes, and the Lophophorates due to their body cavity. The Ectoproct's unknown type of coelom, due to the disappearance of the larval stage during metamorphosis, distinguishes it from the Pseudoceolomates, Proterostomes, and the Lophophorates. The Pseudocoelomates have pseudocoelom while the Proterostomes and Lophophorates have true coeloms.

Through these differences in the body cavities, the Ectoprocta can be distinguished from the Pseudocoelomates, the Proterostomes, and the Lophophorates and emerge as a distinct superphylum.

Table 3: Proposed taxonomy for cladistic analysis. The superphyla Ectoprocta, Protostomata, and Pseudocoelomates.
Kingdom Animalia
Superphyla Ectoprocta
    Genera Victorella, Bugula, Micropovella, Cristaella, Lophopus, Crisia, Plumatella,
Superphyla Proterostomes
    Genera Dina, Nautilus, Lucifer, Limulus, Octopus, Nereis, Crania, Lingula, Phoronis
Superphyla Pseudocoelomates
    Genera Pycnnophyes, Trichuris, Seison, Nectonema, Rotaria,
Superphyla Entoprocta
    Genera Barentsia, Pedicellina
Out-groups
    Genera Loxosome, Urnatella
 

Hickman, Cleveland P. 1973. Biology of the Invertebrates. 2^nd ed. The C. V. Mosby Co. Saint Louis. 276-291.

Holt, Jack R. 2000. SUPPLEMENT: A CLASSIFICATION OF THE ANIMAL KINGDOM AND DESCRIPTIONS OF PHYLA.Systematic Biology. http://www.susqu.edu/facstaff/h/holt/animals/ANIMALKINGDOMS.htm Date accessed:24 January 2000

Maddison, Wayne P. and David Maddison. 1999. MacClade. Version 3.08. Sinauer Associates, Inc. Sunderland.

Margulis, L. and K. Schwartz. 1998. Five Kingdoms, An Illustrated Guide to the Phyla of Life on Earth. 3^rd ed. W. H. Freeman and Co. New York. 242-245, 248-249, 260-267, 272-279, 290-293, 302-305.

Pratt, Henry S. 1935. A Manual Of The Common Invertebrate Animal. P. Blackiston’s Son & Co.,Inc. Philadelphia. 330

Pennak, Robert W. 1953. Fresh-Water Invertebrates of the United States. The Ronald Press Co. New York. 276

Storer, Tracy I. and Robert Usinger. 1957. General Zoology. 4^th ed.McGraw-Hill Book Co. New York. 271, 369-370.

Szuch, Ryan, Jason Schofield, Erin Riedel, Theresa Culley, Jen Wiley, and Stacey Knepp. 2000. Examination of the lophophorates to determine if they belong to the proterostomes or deuterostomes. Journal of Systematic Biology. 7(1): http://www.susqu.edu/facstaff/h/holt/Systematics/Journal/vol7/number1/FungusRus.htm