Fish egg fossils are the

fossilized A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in ...

remains of fish

egg An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the a ...

s. Fossil fish eggs have an extensive

record A record, recording or records may refer to: An item or collection of data Computing * Record (computer science), a data structure ** Record, or row (database), a set of fields in a database related to one entity ** Boot sector or boot record, ...

going at least as far back as the

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...

and spanning into the Cenozoic era. The eggs of many different fish

taxa In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...

have contributed to this record, including

lobe-finned fish Sarcopterygii (; ) — sometimes considered synonymous with Crossopterygii () — is a taxon (traditionally a class or subclass) of the bony fishes known as the lobe-finned fishes. The group Tetrapoda, a mostly terrestrial superclass includi ...

placoderms Placodermi (from Greek πλάξ 'plate' and δέρμα 'skin', literally 'Plate (animal anatomy), plate-skinned') is a Class (biology), class of armoured prehistoric fish, known from fossils, which lived from the Silurian to the end of the Devoni ...

, and

shark Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachimo ...

s. Occasionally eggs are preserved still within the mother's body, or associated with fossil

embryo An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male spe ...

s. Some fossil eggs possibly laid by fish cannot be confidently distinguished from those laid by

amphibian Amphibians are tetrapod, four-limbed and ectothermic vertebrates of the Class (biology), class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terres ...

s; for example, the

ichnogenus An ichnotaxon (plural ichnotaxa) is "a taxon based on the fossilized work of an organism", i.e. the non-human equivalent of an artifact. ''Ichnotaxa'' comes from the Greek ίχνος, ''ichnos'' meaning ''track'' and ταξις, ''taxis'' meaning ...

Mazonova ''Mazonova'' is an oogenus of fossilized eggs from the Mazon Creek area in the Pennsylvanian of Illinois. They are laid in long strings of eggs enclosed in a gelatinous sheath containing one or two rows of eggs. It is unknown what kind of animal ...

'' is known from impressions of eggs which resemble eggs of both fish and amphibians. Paleontologist B.K. Hall has observed that the discovery of fossil fish eggs, embryos and

larvae A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. The ...

link the sciences of paleontology with

evo-devo Evolutionary developmental biology (informally, evo-devo) is a field of biological research that compares the developmental processes of different organisms to infer how developmental processes evolved. The field grew from 19th-century beginni ...

Fish taxa known from egg fossils

Cartilaginous fishes

Fossilized egg cases that may have been laid by an

elasmobranch Elasmobranchii () is a subclass of Chondrichthyes or cartilaginous fish, including sharks (superorder Selachii), rays, skates, and sawfish (superorder Batoidea). Members of this subclass are characterised by having five to seven pairs of gil ...

or chimaeroid are known from as far back as the Devonian period. Egg sacs that can more confidently be referred to those taxa are known from the

Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carbonifero ...

Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the ...

, although no embryos are known from these. Shark eggs have been recognized in the fossil record. More than thirty fossil shark egg cases have been discovered at the Bear River Seep Deposit of Washington state in the US. 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 The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...

epoch, 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 ''Scyliorhinus'' is a genus of catsharks in the family Scyliorhinidae. This genus is known in the fossil records from the Cretaceous period, late Albian age to the Pliocene epoch.Carrier, J. C.; Musick, J. A. & Heithaus, M. R. (2004)''Biology of ...

'', which also has a fossil record stretching back to the Eocene. However, modern ''Scyliorhinus'' egg capsules are smoother than the Bear River Seep Deposit fossils, casting doubt on this possibility.

Lobe-finned fishes

Some well-preserved embryos have been found with

yolk Among animals which produce eggs, the yolk (; also known as the vitellus) is the nutrient-bearing portion of the egg whose primary function is to supply food for the development of the embryo. Some types of egg contain no yolk, for example bec ...

sacs in the Carboniferous

actinistian The coelacanths ( ) are fish belonging to the order Actinistia that includes two extant species in the genus ''Latimeria'': the West Indian Ocean coelacanth (''Latimeria chalumnae''), primarily found near the Comoro Islands off the east coast ...

Rhabdoderma exiguum ''Rhabdoderma'' is an extinct genus of coelacanth fish in the class Sarcopterygii. It lived in the Carboniferous and Early Triassic, and its fossils have been found in Europe, Madagascar and North America North America is a contin ...

''. These range in development from specimens still inside the egg to individuals who had partially resorbed their yolk sac. These specimens were part of the

Mazon Creek fauna Mazon may refer to: Places in the United States * Mazon, Illinois, a village * Mazon Creek fossils * Mazon River * Mazon station, Mazon, Illinois * Mazon Township, Grundy County, Illinois Organizations * MAZON: A Jewish Response to Hunger, a no ...

Illinois Illinois ( ) is a U.S. state, state in the Midwestern United States, Midwestern United States. Its largest metropolitan areas include the Chicago metropolitan area, and the Metro East section, of Greater St. Louis. Other smaller metropolita ...

Placoderms

One possible specimen of the Devonian placoderm ''

Cowralepis mclachlani ''Cowralepis'' is an extinct genus of phyllolepid placoderm of Givetian The Givetian is one of two faunal stages in the Middle Devonian Period. It lasted from million years ago to million years ago. It was preceded by the Eifelian Stage a ...

'' contained many unhatched egg sacs.

Confounding factors

Some fossil eggs possibly laid by fish can't be confidently distinguished from those laid by

s. Examples are known from various Carboniferous and

Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...

lagerstatten that preserve the eggs of aquatic vertebrates. The identity of the fossils' egglayers can't be confidently ascertained.

Footnotes

References

* Cloutier, R. 2010. The fossil record of fish ontogenies: insights to developmental patterns and processes. ''Semin Cell Dev Biology'' 21: 400–413. * Treude, T., Kiel, S., Linke, P., Peckmann, J., and Goedert, J.L. 2011. Elasmobranch egg capsules associated with modern and ancient cold seeps: A nursery for non-seep marine predators. ''Marine Ecology Progress Series'' 437: 175–181. {{eggs .