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)
Osteolepis fossil
Osteolepis panderi fossi; Devonian Period, Scottland; Order Osteolepiformes

Tetrapods
This page last updated 20 July 2017 by Udo M. Savalli ()
Images and text Udo M. Savalli. All rights reserved.