Fish egg fossil
Fish egg fossils are the fossilized remains of fish eggs.
Fossilized egg cases that may have been laid by an elasmobranch or chimaeroid are known from as far back as the Devonian period.[1] Egg sacs that can more confidently be referred to those taxa are known from theCarboniferous to Oligocene, although no embryos are known from these.[1] Carboniferous and Triassic lagerstatten have both preserved the eggs of aquatic vertebrates, although it can't be known for certain whether these were laid by fish or amphibians.[1] Hall has observed that the discovery of fossil fish eggs, embryos and larvae link the sciences of paleontology with evo-devo.[2]
Cartilaginous fishes
Fossilized egg cases that may have been laid by an elasmobranch or chimaeroid are known from as far back as the Devonian period.[1] Egg sacs that can more confidently be referred to those taxa are known from theCarboniferous to Oligocene, although no embryos are known from these.[1]
More than thirty fossil shark egg capsules have been discovered at the Bear River Seep Deposit. These capsules are up to 5 cm in length and resemble those of modern catshark species in the genus Apristurus. Since fossil teeth attributable to this genus go back to the late Eocene this, an ancient Apristurus species might very well be the mother of the fossil egg cases. A less likely candidate mother would be the genus Scyliorhinus, which also has a fossil record stretching back to the Eocene. However, modern Scyliorhinus egg capsules are smoother than the fossil specimens, casting doubt on this possibility.
Lobe-finned fishes
Some well-preserved embryos have been found with yolk sacs in the Carboniferous actinistian Rhabdoderma exiguum.[3] These range in development from specimens still inside the egg to individuals who had partially resorbed their yolk sac.[4] These specimens were part of the Mazon Creek fauna of Illinois.
Placoderms
One possible specimen of the Devonian placoderm Cowralepis mclachlani contained many unhatched egg sacs.[1]
See also
Footnotes
- ^ a b c d e f "Fossil record of fossilized ontogenies", Cloutier (2010); page 401.
- ^ "Phylogenetic perspective on developmental patterns and processes", Cloutier (2010); page 410.
- ^ "Fossil record of fossilized ontogenies", Cloutier (2010); pages 401-402.
- ^ "Fossil record of fossilized ontogenies", Cloutier (2010); page 402.
References
- R. Cloutier, The fossil record of fish ontogenies: insights to developmental patterns and processes. Semin Cell Dev Biology, 21 (2010), pp. 400–413.