EEMB 136L Lecture 7: Lab 7
15 Nov 2017
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Characteristic: shell with >1 valves, a muscular foot, gill structures. Calcareous exoskeleton is secreted from the mantle and provides support for a muscular foot. Bears mineralized teeth and protudes from the mouth to aid in feeding. Lack shells, but have small aragonitic (caco3) spines= sclerites. 8 bilaterally symmetric valves surrounded by a girdles, which also contains aragonitic(caco3) sclerites. The 8 valves soon disarticulate after death so isn"t seen in fossils. Some palezoic stem-group chitons, called mutliplacophorans, are known to have. Tapering, tubular, univalved shell closed dorsally and ventrally and open both anteriorly and posteriorly. Posterior (apical) opening is used to ventrilate the mantle cavity. Bilaterally symmetrical and separates them into right and left mirror images. Has a pegma- bridge of carbonate that links the 2 valves so valves can"t open. Extinct ammonites and belemnites which were common in mesozoic. Found in all marine paleoenvironments from deep to shallow.
