Fishy Tales - things to learn from fish fossils
Fishy Tales - things to learn from fish fossils
Let the rocks tell their story
What
fish teeth from 110 million years ago can tell us?
What
a fish vertebra (backbone) from 110 million years ago tell us?
The Story - what can we learn from fossil fish teeth?
Teeth first appeared in the fish. They may be considered fundamental building blocks for vertebrates..
Shape of a tooth indicates it's use..
The agnathans (jawless fish)
- generally lack teeth,
- but some parasitic forms, such as the lampreys have tooth-like structures. sharp, horny, uncalcified structures around the mouth
- some regard them as real teeth
- if this is the case, then teeth originated before jaws.
acanthodians (extinct spiny sharks)
and
actinopterygians (ray-finned fishes).
At this time,
placoderms (extinct armoured fish)
also had tooth-like structures on their jaws but...
- they weren't set into the jaws, and
- they not delineated from the jaw bone.
- placoderm teeth are regarded as cusps, not true teeth.
True teeth were developed by
. 
osteichthyan fish
- they were composed of 3 layers, central pulp cavity surrounded by a layer of dentine, which was surrounded by layers of enameloid.
- they lacked root systems
- in most fish, all the teeth are roughly similar size and shape (homodont).
crossopterygians fringe finned fish
- size tooth size variation is common.
- they have very large stabbing fangs surrounded by small rows of marginal teethdeveloped one of the earliest innovations, "dental lamina", a structure producing teeth throughout the life of the animal
- developed one of the earliest innovations, "dental lamina", a structure producing teeth throughout the life of the animal
- in some crossopterygians and early tetrapods (amphibians), complex labyrinthine infolding of dentine and enamel is a specialised feature
- in the strict definition of enamel, it occurs only in crossopterygian fish and higher terrestrial vertebrates
- it is the shiny, highly mineralised outer layer of the tooth, with highly-ordered, perpendicular crystalline orientations when viewed in cross section
holocephalans and
bradyodont (cochliodont) sharks
- teeth developed by fish that feed by crushing hard-shelled invertebrates can be flat pavement-like reinforced by tubes of pleuromic dentine, as in .
- sharks shed teeth throughout their life and they are continually replaced.
some lungfish
- have flat crushing tooth-plates, some with numerous rows of teeth on each tooth plate
- grow out from a dentine base, have outer enameloid over the individual tooth cusps
- the central region of each tooth cusp on the tooth plate is strengthened by hypermineralised tissues such as petrodentine.
.What fish teeth from 110million years ago can tell us...
Size of jaw and shape of teeth suggest this carviverous fish caught something small (it is small itself) and slippery (hence the "hooked" teeth)
The small fragments in the matrix include scales, teeth and bone fragments and give us an idea of what food sources could be around
What a fish vertebra (backbone) from 110million years ago tell us?
The size of the backbone in this case can give us an idea of the size of the fish, maybe even it's approximate length
In the matrix surrounding the fossil at this site were possible stomach contents - a record of what that fish ate ... written in the stone with the fossilised remains of scales, bones and squid claws
Want to know more about FOSSILS and INDEX FOSSILS
source from the collection of Earth Science Australia
John Long The Long History of Australian Fish Fossils p337-428, in P. Vickers-Rich et al Vertebrate Palaeontology of Australasia1996
http://austhrutime.com/fish_teeth.htm
https://upload.wikimedia.org/wikipedia/commons/5/54/Neeyambaspis_enigmaticus.jpg
https://en.wikipedia.org/wiki/Acanthodii
https://en.wikipedia.org/wiki/Actinopterygii