G404 Geobiology
Fall 2013
Name __________________________________
Lab 4
Fossil fishes: the non-tetrapod vertebrates
Today we will look at fish. The term “fish” is colloquial and not used in scientific literature
because it can refer to anything from a goldfish (Actinopterygia) to a lungfish (Sarcopterygia)
to a shark (Chondricthyes) to a lamprey (Pteromyzodontida). Thus, “fish” is paraphyletic
because it contains all of these vertebrate groups but not tetrapods. Scientists are
uncomfortable using paraphyletic group names, but nevertheless it is sometimes convenient
to call all these swimming creatures “fish”.
This lab provides you with a chance to see fossils, casts of fossils, and reconstructed models
of key fish taxa.
“jawed fish”
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Agnatha, “jawless fish” (paraphyletic)
* jaws
Unnamed
Pteraspidomorphi
* neurocranium (braincase) closed dorsally
* oak-leaf shaped
dermal tubercles
Unnamed
* sensory line enclosed in canals
* opercular flaps
Unnamed
* paired fins or fin folds
Unnamed
* trunk dermal skeleton
Unnamed
* calcified dermal skeleton
Craniata
* eye muscles
* symmetrical gills
* 2 semicircular canals
Vertebrata
Figure 1. Phylogeny of jawless fishes.
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Chondricthyes
(sharks and relatives)
Osteichthyes (bony fish)
* loss of bone
* specialized tooth
replacement
Unnamed
* teeth erupt from dental lamina
* nasal capsule attached to rest of chondrocranium
Gnathostomes
* jaws derived from palatoquadrate (upper)
and Meckel’s (lower) cartilages
* endoskeletal pectoral and pelvic girdles
Figure 2. Phylogeny of jawed fishes (Gnathostomata).
Figure 3. Anglaspis, a typical heterostracan (from Moy-Thomas and Miles, 1971).
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Figure 4. Hemicyclapsis, a typical osteostracan (from Moy-Thomas and Miles, 1971).
Figure 5. Phlebolepis, a thelodont. Note armor of bony scales. (from Moy-Thomas and
Miles, 1971).
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Figure 6. Placoderm skulls (from Moy-Thomas and Miles, 1971).
Assignment
Concentrate on the following when looking at the fossils:
1. What features tell you that it is a vertebrate?
2. Are there features that tell you which group it belongs to?
3. What features can be used to infer the lifestyle of the species?
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