Middle Devonian dipnoan tooth-plates from Estonia

Middle Devonian dipnoan tooth-plates have been known for an hundred and sixty years. However, although gross morphology has been described, there are still several difficulties with these descriptions. The best known Middle Devonian species is Dipterus valenciennesi from Scotland. Most of the specimens of this species are preserved in a dark sediment and all the bone and dentine are stained, making it difficult to outline the microstructure clearly. In this paper we illustrate external surfaces and histology from Middle Devonian tooth plates from the basal Givetian of Estonia. These specimens are preserved as tissue which is not stained by sediment, and has yielded microstructures clearly visible by scanning electron microscopy. The specimens are not associated with hard parts of the external skeleton, and so generic identification cannot be certain. Their value is that they illustrate for the first time details that have been unavailable on previously known Middle Devonian specimens. The role of these plates for the interpretation of Devonian dipnoan tooth-plates is outlined.