Phylum
Chordata
Subphylum Vertebrata
Infraphylum Gnathostomata
Superclass Osteichthyes
Class
Sarcopterygii
Subclass
Coelacanthimorpha (Coelacanths)
Subclass
Dipnoi (Lungfishes)
Subclass
Tetrapodomorpha (Tetrapods and relatives) |
Members
of Class
Sarcopterygii, the Sarcopterygians, belong to Superclass
Osteichthyes, a group or bony fishes, characterized by a
bony skeleton rather than cartilage. The oldest Sarcopterygians
come from the upper Silurian and closely resemble Acanthodians.
The Sarcopterygians closest relatives were the Actinopterygian
ray-finned fishes. The oldest Sarcopterygians date
to the late Silurian. Sarcopterygians probably evolved
in the
oceans, but they later migrated to freshwater environments
to avoid the predatory placoderms
that dominanted the early to middle Devonian marine habitats.
The Sarcopterygians evolved in the early Devonian to split
into the Coelacanths, and the Rhipidistia. The Coelacanths
appeared in the early Devonian, and became widespread in
late Devonian and Carboniferous seas. The Coelacanths were
once believed to have gone extinct at the end of the Cretaceous
period, that is, until the first Latimeria specimen was
found off the east coast of South Africa in 1938. They are
known as a Lazarus taxon, i.e.,a taxon that disappears from
one or more periods of the fossil
record, and appears again in a later period. Since 1938,
Latimeria has been found in the Comoros, Kenya, Madagascar,
Mozambique, and Tanzania; many consider a Coelacanths to
be living fossils. |
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| Osteolepis
macrolepidotus
Middle Devonian
Cruday Quarry, Scotland |
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