Stearn, Colin W. Department of Earth and Planetary Sciences, McGill University, Montreal, Ontario, Canada.
- Biologic position
- History and habitat
- Links to Primary Literature
- Additional Readings
A common group of fossil organisms that lived during the Ordovician, Silurian, and Devonian periods. They are preserved in rocks of these systems as large (cabbage-sized) calcium carbonate fossils in the shape of crusts, plates, domes, fingers, bulbs, cylinders, and bushes consisting internally of a three-dimensional network of regularly repeating structural elements such as pillars, laminae, cyst plates, and walls (illus. a, b, c). Although recognized as a class, or subclass, of sponges, these fossils, unlike most sponges, are lacking in siliceous or calcareous spicules (spikelike supporting structures). The term stromatoporoid has been used for a very similar group of Mesozoic fossils that are discussed here as sphaeractinids. Unlike the Paleozoic stromatoporoids, some of the sphaeractinids show the remains of siliceous spicules and can be assigned to several subclasses of the sponge class Demospongiae. Stromatoporoid has also been used as a descriptive term to apply to a grade of evolution of a wide range of different groups of sponges in which a calcareous basal skeleton of stromatoporoid-like architecture was secreted. The implication of such usage is that the Paleozoic fossils are not a natural group but a collection of disparate lineages of sponges that are at a similar stage of evolution. The term stromatoporoid is best restricted to the fossils of Ordovician, Silurian, and Devonian age defined by their lack of spicules and characteristic internal structures that can be grouped as the class Stromatoporoidea of the Porifera. See also: Demospongiae; Porifera; Sphaeractinoidea
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 9000 highly qualified scientists and 43 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