Polyisomerism and Anisomerism in Cranial and Dental Evolution among Vertebrates
- 1 January 1934
- journal article
- research article
- Published by Proceedings of the National Academy of Sciences in Proceedings of the National Academy of Sciences
- Vol. 20 (1) , 1-9
- https://doi.org/10.1073/pnas.20.1.1
Abstract
Polyisomerism is defined as "the state in which many homologous parts, or polyisomeres, are arranged along any primary or secondary axis, whether straight or curved." It is a more inclusive term than metamerism. It "results from processes of cell division, budding, or reduplication." "The causative forces operate over time, repeat more or less frequently, and are subject to rhythmic acceleration and retardation."[long dash]Anisomerism is the result of heterogony, i.e., "unequal growth'' of one part of a polyisomerous series,"[long dash]from unbalanced or disharmonic isomerism.[long dash]"Allometrons are an expression of anisomerism, or regional emphasis."[long dash]Aristogenes are polyisomeres; so are some rectigrada-tions, but others are anisomeres; i.e., "allometry is inextricably associated with rectigradation and both are special cases of polyisomerism and anisomerism." Recurrent accelerations and retardations can give a polyisomerous growth-center anisomerous emphasis. E.g., the total lengthening of a skull phylogenetically is the "summation of the different proportional increments of each part." (Which allows primitive dolichocephaly to evolve brachycephaly (cf. titanotheres).) Anisomerism often comes about when polyisomeres are subjected to increasing stresses through long periods of geologic time. Polyisomerism gives rise on one hand to anisomerism, on the other to hyperpolyisomerism. Hence the great variation in life forms. "Adaptive radiation seems to have resulted from the summation along divergent lines of the results of secular polyisomerism, anisomerism, and hyperpolyisomerism, while the production of allometrons, rectigradations and aristogenes appears to have been incidental to the same process. Thus taxonomy, paleontology, comparative anatomy, genetics, experimental biology, physiology and allied sciences may find new grounds in tracing the history and behavior of poly-isom., anisom., hyperpolyis."[long dash]Examples, references.This publication has 0 references indexed in Scilit: