Gnathostomata, Superclass Osteichthyes, Class Sarcopterygii, Subclass
Dipnoi, Family Dipteridae
Time: Middle Devonian (385 Million Years Old)
Achanarras Slate Quarry, Caithness, Scotland
This is a fine fossil specimen of the first lungfish described in
1828. It is one of the oldest to possess cranial ribs, and is thus
believed to have been capable of gulping air, allowing it to extract
oxygen directly from the atmosphere. The lungfish arose during the
early Devonian, reaching a peak in diversity by the Late Devonian.
While all early Dipnooans were marine, all known from the Carboniferous
on have been freshwater
denizens. A few survive today in Africa, South America, and Australia.
The shine to the specimen is the result of cosmine, a layer of shiny
bony tissue that consists of an external enameloid layer over a
dentine layer. Cosmine is thought to have comprised apart of the
skin’s complex vascular system. This cosmine layer was lost
in most Dipnoan by the Late Devonian in favor of thinner scales.
Interestingly, the deposits of Caithness also hold the remains of
Palaeospondlyus, a much smaller fish though by some to be a larval
form of Dipterus because of similar cranial structures.
see: Sarcopterygii Fish Fossils