It was also towards the end of the Silurian, when a period of great aridity set in, that fishes appeared related to our mud-fishes or double-breathers (Dipnoi), which have lungs as well as gills.    From Wordnik.com.  [The Outline of Science, Vol. 1 (of 4) A Plain Story Simply Told] Reference

But the condition of the Dipnoi, which possess lungs but do not walk on land, does not support this supposition, for they possess fins which are either filamentous or fin-like, having a central axis with rays on each side.    From Wordnik.com.  [Hormones and Heredity] Reference

1Google “Characteristics of Dipnoi, a monophyletic group”.    From Wordnik.com.  [Panderichthys rhombolepis - The Panda's Thumb] Reference

(1997) Four species of Metaceratodus (Osteichtyes: Dipnoi, family Ceratodontidae) from Australian Mesozoic and Cenozoic deposits.    From Wordnik.com.  [PLoS ONE Alerts: New Articles] Reference

Dipnoi, fins.    From Wordnik.com.  [Hormones and Heredity] Reference