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| HOME | SYLLABUS | WEEKLY ASSIGNMENTS | J. SYSTEMATIC BIOLOGY | TAXA OF LIFE | |
| PHYLUM CEPHALOCHORDATA | |||||
INTRODUCTION TO THE CEPHALOCHORDATA
Cephalochordata (se-fa-lo-kor-DA-ta) is derived from two Greek roots that mean "head cord" [head -kephali (κεφαλή); and cord -chordi (χορδή)]. The reference is to the notochord extending into the animal's head.
The lancets are free-swimming marine organisms that generally live tucked into the sediment with their anterior end exposed to the water (Figure A). They pull water in through their mouths and filter it through their pharyngial gill slits (Figure B). A sister group to the vertebrates, the cephalochordates have a hollow dorsal nerve chord and a notochord that extends forward into their rostellum. Brusca and Brusca (2003) indicate that this group (a subphylum in their system) can be called Acrania. I follow Nielsen (2001) and Margulis and Schwartz (1998) in elevating the lancets to phylum-level status from the tradition Chordate subphylum designation.
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A. Living amphioxus in feeding position. |
B. Preserved and stained amphioxus to show pharynx with gill slits and notochord. |
| Images taken from: A&B: http://io.uwinnipeg.ca/~simmons/16cm05/1116/chordate.htm |
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SYNOPTIC DESCRIPTION OF THE CEPHALOCHORDATA
| The following description of the phylum Cephalochordata came from Margulis and Schwartz (1998), Buchsbaum (1938), Barnes (1980), Barnes (1984), Brusca and Brusca (2003), Hickman (1973), Storer and Usinger (1965), Colbert and Morales (1991), and Tudge (2000). |
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I. SYNONYMS: lancets, amphioxus. II. NUMBER: 23 III. PHYLUM CHARACTERISTICS:
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HIERARCHICAL CLASSIFICATION OF THE CEPHALOCHORDATA
The taxonomy of this phylum came from Nielsen (2001). It has a single class that I call Branchiostomata. |
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CLASS BRANCHIOSTOMATA (1 ORDER)
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This page is maintained by Jack R. Holt. Last modified: 01/08/08.
