Micromorphologic Studies of Platform Conodonts
Abundant and well-preserved specimens of Palmatolepis spp. from the Chudleigh area of Devonshire, England, have been used to study the interrelationships between the various biocharacters employed in conventional taxonomy: platform length, platform width, strength of ornamentation, carina length, carina curvature, character of denticulation, positions of azygous node, presence of a secondary carina, and general platform outline. Most of these characters are correlated with growth, and the taxonomic and stratigraphic implications are discussed. Similar studies are presented for the genus Icriodus.
Representatives of the genus Pseudopolygnathus, from the Pilton Beds of North Devon, display a wide diversity of platform shape and ornamentation, but, in contrast, the nature of the basal cavity is similar throughout the population. Orally, five groups of forms are recognizable, four of which resemble P. vogesi, P. multistriata, P. dentilineata, and P. c.f. prima. Aborally, the basal cavities are wide, flared, and consistently equal in width to the platform, thus being typical only of P. dentilineata. Detailed measurements of maximum platform and basal cavity width serve to confirm this characteristic.
The diversity of oral ornamentation is considered to be the result of infra-specific variation within the species group P. dentilineata.