Article: Differentiating evolution from environmentally induced modifications in mid-Carboniferous conodonts
Envirotypes are persistent, environmentally induced, potentially inheritable phenotypes that have not been genetically selected for an environment. Unlike ecotypes, envirotypes do not breed true in different environments. The term ecophenotype should be restricted to phenotypic modifications resulting from disease, injury, physical restrictions on growth or to modifications that develop through use. To distinguish evolution from environmentally induced modifications in conodonts one should consider: (1) number of multielement species in the fauna exhibiting modifications; (2) number of elements in the apparatus displaying modifications; (3) uniqueness of modification; (4) occurrence of modified and unmodified forms; and (5) stratigraphical range of modified form. When applied to the conodont fauna from the Carboniferous Barnett Formation in Texas, these criteria suggest that the geniculatan element is not an envirotype or ecophenotype of the ponderosiform element, but that two species of Idioprioniodus? are present. Similarly, when applied to the Pa element of the Taphrognathus varians apparatus, the criteria suggest that blade position relative to platform and platform ornamentation is not an environmentally induced feature.