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Scaphopoda (tusk shells)<br />
small group of mostly small, infaunal or semi-infaunal, marine mollusks<br />
shell typically a few centimeters in length<br />
(largest form found 30 cm in length)<br />
shell is a slender tapering and usually gently curved tube<br />
shell is open at both ends, the large end of the shell being anterior<br />
exterior has finely spaced growth lines and usually some<br />
type of longitudinal ornamentation or ribs.<br />
protrusible burrowing foot extends from the anterior end<br />
no gills, respiration by direct exchange with mantle tissue<br />
head is poorly-developed<br />
numerous tentacles (called captacula) and a radula<br />
animal feeds on microscopic organisms and organic detritus.<br />
Scaphopoda first appear in the Ordovician or the Devonian or even the early Carboniferous<br />
rare in fossil record<br />
Scaphopods probably evolved from a tiny, semi-infaunal helcionellid ancestor<br />
(via conocardioid rostroconches)<br />
<strong>Mollusca</strong><br />
Pinnocaris (Ordovician)<br />
not a scaphopod!
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