BIO 370 Vertebrate Zoology
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Vertebrate Diversity
Class Sarcopterygii Lobe-fined Fishes

(Click on any image for larger version)

Sarcopterygii Characteristics

  • Muscular lobed paired fins joined to body by single bone
  • Two dorsal fins with separate bases
  • Has a pulmonary vein
  • Phylogenetically, this clade should also include tetrapods
  • Formerly treated as a subclass of the Osteichthyes (bony fishes)

Subclass Actinistia Coelacanths

Characteristics

  • Large size (~2m)
  • Distinctive caudal fin with 3 divisions
  • Fins muscular, limb-like ("lobed")
  • Skeleton mostly cartilagenous
  • Modern species are marine, in deep water
  • 2 extant species (first one discovered in 1938)
Coelacanth
Comorese Coelacanth, Latimeria chalumnae
Axelrodichthys
Axelrodichthys sp., an extinct coelacanth (Cretaceous Period)
Coccoderma Fossil
Coccoderma barvaricum fossil; Late Jurassic Period, Europe

Subclass Dipnoi Lungfishes

Characteristics

  • Elongated bodies
  • Dorsal, caudal, anal fins fused into single rear fin
  • Fins flipper-like or reduced to long filaments
  • Paired lungs
  • Live in tropical rivers or swamps prone to drying
  • 6 living species
West African Lungfish
West African Lungfish, Protopterus annectens; Order Lepidosireniformes
Marbled African Lungfish
Marbled African Lungfish, Protopterus aethiopicus; Order Lepidosireniformes
Australian Lungfish
Australian Lungfish, Neoceratodus forsteri; Order Ceratodontiformes

Stem Tetrapodamorpha & Tetrapod Origins

Characteristics

  • The following image depicts the earliest tetrapods (Acanthostega and Ichthyostega) with some closely related lobe-finned fishes
  • All date from the late Devonian Period
  • Osteolepiform fishes (e.g. Hyneria & Eusthenopteron) share with tetrapods various skull characteristics, internal nostrils and labyrinthodont teeth (with folded enamel)
  • They also have fins with distinct humerus, ulna, radius or femur, tibia, fibula
  • All of these species probably lived in fresh water (only Ichthyostega was probably partially terrestrial)
Tetrapods
This page last updated 12 December 2015 by Udo M. Savalli ()
Images and text Udo M. Savalli. All rights reserved.