| Gnathostomulida |
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80 species
Characteristics
- hardened jaws and basal plate; head with sensory bristles
In what other invertebrate did we see jaws?
- no cuticle
- small interstitial (meiofaunal) animals, typically in fine, anoxic marine sediments
Phylogeny
Several hypotheses:
At any rate, spiral cleavage suggest affinity to Spiralia ('Platyhelminthes-Rotifer-Lophotrochozoa' clade).
1) Platyhelminthes affiliations suggested by several features shared with ;
- triploblastic with no coelomic cavity
- externally ciliated
- no functional anus
2) Cnidarian affiliations suggested by the presence of monociliate cells (as in cnidarian planula larvae). Possibly an intermediate between the Cnidarians and Platyhelminthes.3) Gastrotrich affiliations suggested by molecular sequence data. But the gastrotrichs (next) are themselves of uncertain affliation.
4) Rotifer affiliations suggested by jaws and similar head, neck and trunk, which tapers to a tail in some. However, some consider rotifers as a phylum of uncertain affliation.
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