Pterobranchia
- Information from Wikipedia on these worm-shaped animals.
- http://en.wikipedia.org/wiki/Pterobranchia

First Occurrence of Rhabdopleura in North America
- First fossil representatives of Rhabdopleura (Graptolithoidea: Rhabdopleuroidea) in North America are reported.
- http://sztandary.graptolite.net/Rhabdopleura_anticosti.html

The oldest known Cephalodiscus-like hemichordate
- Eocephalodiscus polonicus Kozlowski from the upper Tremadocian of Poland: pictures of the holotype, links.
- http://www.mierzejewski.info/Eocephalodiscus.html

Cephalodiscus graptolitoides Dilly, 1993.
- This species, a probable extant graptolite (according to some researchers), is regarded as a living fossil.
- http://sztandary.graptolite.net/graptolitoides.html

Cephalodiscus densus Andersson, 1907 (Hemichordata, Graptolithoidea).
- Zooid and coenecium morphology of a cephalodiscid pterobranch from Terra Nova Bay, Ross Sea.
- http://pterobranchia.graptolite.net/C_densus.html

Collagen in the pterobranch coenecium
- Results of amino-acid analysis of the coenecium of Cephalodiscus and Rhabdopleura.
- http://www.graptolite.net/collagen.html

SEM micrographs of Rhabdopleura compacta.
- Three coenecia (two young) collected from Stoke Point, England, are illustrated.
- http://kulicki.mierzejewski.biz/compacta.html

Cephalodiscus and Classification of Cephalodiscoidea
- List of species and genera of recent and fossil cephalodiscid pterobranchs.
- http://pterobranchia.graptolite.net/Cephalodiscoidea.html

Cephalodiscus lutetianus (Graptolithoidea, Cephalodiscoidea)
- The only fossil species of the genus Cephalodiscus.
- http://www.countofcalmont.com/lutetianus.html

Pterobranchia: Classification of the Rhabdopleuroidea
- List of extinct and extant families, genera and species.
- http://pterobranchia.graptolite.net/Rhabdopleuroidea.html

Rhabdopleura kozlowskii
- Diagnosis, occurrence, images and references of the Jurassic species.
- http://pterobranchia.graptolite.net/Rhabdopleura_kozlowskii.html

Classification of the Extant Hemichordata
- List of species, genera and families.
- http://cluster3.biosci.utexas.edu/faculty/cameronc/Hemichordate.Species.html

Class Pterobranchia
- General information.
- http://faculty.washington.edu/bjswalla/Hemichordata/Pterobranchia/class%20pterobranchia.html

Cephalodiscus gracilis
- Photos of a colony and individuals.
- http://faculty.washington.edu/bjswalla/Hemichordata/Pterobranchia/cephalodiscus%20gracilis.html