• WordNet 3.6
    • n Dipnoi bony fishes of the southern hemisphere that breathe by a modified air bladder as well as gills; sometimes classified as an order of Crossopterygii
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Webster's Revised Unabridged Dictionary
    • n. pl Dipnoi (Zoöl) A group of ganoid fishes, including the living genera Ceratodus and Lepidosiren, which present the closest approximation to the Amphibia. The air bladder acts as a lung, and the nostrils open inside the mouth. See Ceratodus, and Illustration in Appendix.
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Century Dictionary and Cyclopedia
    • dipnoi A subclass of fishes, by some considered to be a peculiar class of vertebrates intermediate between fishes and batrachians, and by others an order of fishes (by some ranked as a suborder of ganoid fishes), containing the lung-fishes of the genera Lepidosiren and Protopterus (Dipneumona) and Ceratodus (Monopneumona), and many extinct relatives. They have both branchial and pulmonary respiration, whence the name; no distinct suspensorium is developed, but the lower jaw articulates directly with descending processes of the cranium; there is a median pelvic element; and the limbs are multiarticulate. The skeleton is partially osseous, with persistent notochord; the heart has two auricles and one ventricle; there is a muscular conus arteriosus and spiral intestinal valve; the gills are free, with a narrow opening and rudimentary gill-cover; and the air-bladder is nearly or quite double, and developed into functional lungs permanently communicating with the esophagus. The body is covered with cycloid scales. The living Dipnoi are divisible into two groups, Dipneumona with paired lungs, and Monopneumona with a single lung of two symmetrical halves. Some old extinct relations are referred to another order (or suborder) called Ctenodipterini, by others endowed with the rank of a family only. See barramunda, Ceratodidœ, Ctenodipterini, Dipteridœ, Lepidosirenidœ, mudfish, and Sirenoidea. Also called Diplopnoi, Dipneusta, Dipneusti, Dipnoa.
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Chambers's Twentieth Century Dictionary
    • n.pl Dipnoi dip′noi the lung fishes
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Webster's Revised Unabridged Dictionary
NL., fr. Gr. with two breathing apertures; di- = di`s- twice + breath


In literature:

The Dipnoi show a distinct transition between fishes and amphibia.
"Encyclopaedia Britannica, 11th Edition, Volume 2, Slice 8" by Various
In Protopterus among the Dipnoi it is enclosed within the walls of the stomach.
"Encyclopaedia Britannica, 11th Edition, Volume 8, Slice 8" by Various
This is especially the case with the Ganoids and the Dipnoi.
"The Chain of Life in Geological Time" by Sir J. William Dawson
There is again no indication of any close affinity between the Dipnoi and, at any rate, existing Ganoids.
"The Works of Francis Maitland Balfour, Volume 1" by Francis Maitland Balfour