Century Dictionary and Cyclopedia
- 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.
GNU Webster's 1913
- n. (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
- n. bony fishes of the southern hemisphere that breathe by a modified air bladder as well as gills; sometimes classified as an order of Crossopterygii
“Silurian and the coal measures, we find very plentiful remains of certain fish called the dipnoi, of which group three genera still survive; they display, in numberless features of their anatomy, transitional characters between true fish and amphibia.”
“Of the older dipnoi (Paladipneusta) we have now only one specimen, the remarkable Ceratodus of East Australia; its amphiblastic gastrulation has been recently explained by Richard Semon (cf. Chapter 2.21).”
“So again, while the group of fishes, termed ganoids, is, at the present time, so distinct from that of the dipnoi, or mudfishes, that they have been reckoned as distinct orders, the Devonian strata present us with forms of which it is impossible to say with certainty whether they are dipnoi or whether they are ganoids.”
“5Google “Diabolepis and its relationship to dipnoi””
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