Thelodonten, een raadselachtige groep vissen

Thelodonts are considered to be an enigmatic group of jawless fishes. An attempt has been made to draw a picture on the basis of relevant literature and intact specimen from the author's collection. A juvenile Logania is discussed showing the circular shape of the mouth. Remarks are made on the flexibility with regard to scale-size reduction on the pectoral and tailfins. A well preserved large Thelodus borrowed from the Royal Museum of Scotland, is described concerning possible indications of the branchial structure. Finally the striking similarities between thelodont and 'shark' scales with three possibilities as to phylogenetic ancestry: 1) Thelodonts being the sister group of chondrichtyans. 2) Thelodonts and chondrichtyans sharing a primitive character which does not have to suggest a relationship. 3) Thelodonts being ancestral to chondrichthyans.