Smith, Andrew B. Department of Paleontology, Natural History Museum, London, United Kingdom.
Last reviewed:January 2020
- Related Primary Literature
- Additional Reading
An order of irregular echinoids (sea urchins) of the superorder Atelostomata (class Echinoidea), with a strongly bilaterally symmetrical test. Members of the Holasteroida have a small, oval mouth (lacking buccal notches) that lies close to the anterior on the lower surface; a jaw apparatus is never present. Ambulacral plating is simple. The anterior ambulacrum is often differentiated, and petals are developed adapically (see illustration), except in deep-sea forms. The anus lies on the posterior face. The elongate apical disk, in which ocular plates II and IV abut along the midline and separate the anterior and posterior pairs of genital plates, is the most distinctive characteristic. In a few genera, the apical disk is split, with anterior and posterior parts being separated by intervening interambulacral plates. Phyllodes (petal-shaped ambulacra near the mouth) of penicillate feeding tube feet, with their associated characteristically large pores, are typically developed around the mouth. See also: Echinodermata; Echinoidea
The content above is only an excerpt.
for your institution. Subscribe
To learn more about subscribing to AccessScience, or to request a no-risk trial of this award-winning scientific reference for your institution, fill in your information and a member of our Sales Team will contact you as soon as possible.
to your librarian. Recommend
Let your librarian know about the award-winning gateway to the most trustworthy and accurate scientific information.
AccessScience provides the most accurate and trustworthy scientific information available.
Recognized as an award-winning gateway to scientific knowledge, AccessScience is an amazing online resource that contains high-quality reference material written specifically for students. Contributors include more than 10,000 highly qualified scientists and 46 Nobel Prize winners.
MORE THAN 8700 articles covering all major scientific disciplines and encompassing the McGraw-Hill Encyclopedia of Science & Technology and McGraw-Hill Yearbook of Science & Technology
115,000-PLUS definitions from the McGraw-Hill Dictionary of Scientific and Technical Terms
3000 biographies of notable scientific figures
MORE THAN 19,000 downloadable images and animations illustrating key topics
ENGAGING VIDEOS highlighting the life and work of award-winning scientists
SUGGESTIONS FOR FURTHER STUDY and additional readings to guide students to deeper understanding and research
LINKS TO CITABLE LITERATURE help students expand their knowledge using primary sources of information