Hostname: page-component-586b7cd67f-gb8f7 Total loading time: 0 Render date: 2024-11-25T03:54:00.418Z Has data issue: false hasContentIssue false

Crises in Cephalopod Evolution

Published online by Cambridge University Press:  19 July 2017

Curt Teichert*
Affiliation:
Department of Geological Sciences, University of Rochester, Rochester, NY 14627
Get access

Extract

The 520 million year evolutionary history of the Cephalopoda is punctuated by a number of severe crises during each of which this class came very close to extinction. These are fully documented only for the externally shelled, or ectocochlian, cephalopods to which my remarks are, therefore, restricted. The word crisis should be defined narrowly in the sense in which it is used in medicine, business, and the social sciences: “a condition…. felt to endanger the continuity of the individual or his group “(Webster's Third International Dictionary). Within species, genus, and family groups evolutionary crises are, of course, commonplace, and even orders may disappear without threatening the extinction of an entire class. It is only when all, or almost all, taxa of family-group and lower hierarchic level disappear more or less simultaneously, or within a geologically very short period of time, that we may speak of a crisis, a situation that threatens the very survival of a class, or higher taxon, of organisms. It is the purpose of this presentation to study in some detail this kind of situation as it has affected the evolutionary history of the Cephalopoda.

Type
Research Article
Copyright
Copyright © 1985 University of Tennessee, Knoxville 

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)