cephalochordate

Introduction
General features
- Size and range of diversity of structure
- Importance
Natural history
- Reproduction and life cycle
- Ecology and habitats
- Food, feeding, and movement
Form and function
- General features
- External features
- Internal features
  - Skeleton, tissues, and muscles
  - Nervous system and organs of sensation
  - Digestion and excretion
  - Respiration
  - Circulatory system
  - Hormones
Evolution and paleontology
Classification

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Animal Factoids

Related Questions

How do buccal cirri help lancelets feed?
How do cephalochordates detect chemicals in seawater?
How do cephalochordates feed while buried in marine sediment?
How do cephalochordates reproduce?
How do cilia create a feeding current in cephalochordates?
How do gill slits function in cephalochordate feeding?
How do lancelets move through water?
How do male and female amphioxi differ internally?
How do staggered myotomes help a lancelet swim?
How do the gonads of Branchiostoma differ from those of Epigonichthys?
How do the light-sensitive organs of lancelets detect changes in light?
How does blood circulate in a cephalochordate without a heart?
How does segmentation in cephalochordates compare with segmentation in vertebrates?
How does the atrium protect the gills of a cephalochordate?
How does the cephalochordate atrium differ from the tunicate atrium?
How does the cephalochordate nervous system compare with the vertebrate nervous system?
How does the notochord of a cephalochordate differ from the embryonic notochord of most vertebrates?
How is food digested in a lancelet?
How large are most cephalochordates?
How long does it take for ciliated amphioxus larvae to develop after fertilization?
How old is the cephalochordate fossil record?
What are myotomes in cephalochordates?
What happens to cephalochordate larvae before they become juveniles?
What is the cephalochordate caecum compared with in vertebrates?
What is unusual about phagocytosis in amphioxus digestion?
What role does mucus play in cephalochordate feeding?
Where are cephalochordate eggs fertilized?
Where do cephalochordates live?
Where does water leave the body of a cephalochordate after passing through its gill slits?
Which fins do lancelets have?
Why are cephalochordates also called lancelets?
Why are lancelets sometimes called acraniates?
Why do adult cephalochordates bury themselves in sand or gravel?
Why do cephalochordates have no paired fins?
Why do cephalochordates sink when they stop swimming?
Why do scientists debate whether the first ancestral chordate resembled a cephalochordate or a tunicate?
Why do soft-bodied cephalochordates leave few fossils?
Why was the genus Branchiostoma formerly called Amphioxus?

Science Insects & Other Invertebrates

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External Websites

University of California, Berkeley: Museum of Paleontology - Introduction to the Cephalochordata
UNESCO - Encyclopedia Life Support Systems - Tunicata and Cephalochordata

cephalochordate

chordate subphylum

Also known as: Acrania, Cephalochordata

Written by

Michael T. Ghiselin

Senior Research Fellow, California Academy of Sciences, San Francisco. Author of The Triumph of the Darwinian Method.

Michael T. Ghiselin

Fact-checked by

Britannica Editors

Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree....

Britannica Editors

History

cephalochordate, any of more than two dozen species belonging to the subphylum Cephalochordata of the phylum Chordata. Small, fishlike marine invertebrates, they probably are the closest living relatives of the vertebrates. Cephalochordates and vertebrates have a hollow, dorsal nerve cord, pharyngeal gill slits, and a notochord. In most vertebrates, the embryonic notochord is eventually replaced by bony vertebrae or cartilaginous tissue; among cephalochordates, the notochord is retained into adulthood and is never replaced by vertebrae....

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