Morphological links in an evolutionary sequence of the Cretaceous ammonitegenus Metoicoceras Hyatt

Species of the ammonite genus Metoicoceras are not generally strongly diffe rentiated with respect to coiling and ornament. The present study addresses the problem of how well purely visual (subjective) identification succeeds in identifying taxonomically and hence evolutionarily relevant differences between forms. Multivariate statistical analysis, based on coiling, standa rd dimensions of the conch and ornamental properties, indicates that quanti tative procedures reproduce traditional methods to a conspicuous degree, wi th the added advantage of objective repeatability. Additionally, uncertain phylogenetic relationships could be resolved by appropriate methods of mult ivariate statistical analysis and possible new information on dimorphism in the conch was obtained. (C) 2000 Academic Press.