Cephalodiscus gracilis - Photos of a colony and individuals. Class Pterobranchia - General information. Rhabdopleura kozlowskii - Diagnosis, occurrence, images and references of the Jurassic species. Pterobranchia: Classification of the Rhabdopleuroidea - List of extinct and extant families, genera and species. Cephalodiscus lutetianus (Graptolithoidea, Cephalodiscoidea) - The only fossil species of the genus Cephalodiscus. Cephalodiscus and Classification of Cephalodiscoidea - List of species and genera of recent and fossil cephalodiscid pterobranchs. SEM Micrographs of Rhabdopleura compacta. - Three coenecia (two young) collected from Stoke Point, England, are illustrated. Collagen in the Pterobranch Coenecium - Results of amino-acid analysis of the coenecium of Cephalodiscus and Rhabdopleura. Cephalodiscus densus Andersson, 1907 (Hemichordata, Graptolithoidea). - Zooid and coenecium morphology of a cephalodiscid pterobranch from Terra Nova Bay, Ross Sea. Cephalodiscus graptolitoides Dilly, 1993. - This species, a probable extant graptolite (according to some researchers), is regarded as a living fossil. The Oldest Known Cephalodiscus-like Hemichordate - Eocephalodiscus polonicus Kozlowski from the upper Tremadocian of Poland: pictures of the holotype, links. First Occurrence of Rhabdopleura in North America - First fossil representatives of Rhabdopleura (Graptolithoidea: Rhabdopleuroidea) in North America are reported. Pterobranchia - Information from Wikipedia on these worm-shaped animals.