Article
Article
Ammonoidea
Article By:
Monks, Neale Department of Palaeontology, Natural History Museum, London, United Kingdom.
Last reviewed:October 2019
DOI:https://doi.org/10.1036/1097-8542.900223
An extinct subclass of Cephalopoda (phylum Mollusca). Besides the Ammonoidea (chambered ammonoids), the other subclasses of Cephalopoda are Nautiloidea (chambered nautiloids) and Coleoidea (squid, cuttlefish, octopus, and extinct belemnites), both of which include extant species. The Ammonoidea had buoyant external shells similar to those of the Nautiloidea, but their life cycle and anatomy resembled the Coleoidea. The Ammonoidea and Coleoidea most likely share a common ancestor with the straight-shelled and chambered Bactritida, which arose 390 million years ago in the Devonian Period. The Ammonoidea were very diverse and their fossil remains are abundant. Ammonoid fossils have been used widely for relative age dating and biostratigraphy (Fig. 1), as well as being objects of cultural or ritualistic significance. See also: Cephalopoda; Coleoidea; Fossil; Mollusca; Nautiloidea
The content above is only an excerpt.
About AccessScience
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
