''Delphyodontos dacriformes'' is a prehistoric holocephalan fish from the middle

Carboniferous The Carboniferous ( ) is a Geologic time scale, geologic period and System (stratigraphy), system of the Paleozoic era (geology), era that spans 60 million years, from the end of the Devonian Period Ma (million years ago) to the beginning of the ...

-aged

Bear Gulch Limestone The Bear Gulch Limestone is a limestone-rich Lens (geology), geological lens in central Montana, renowned for the quality of its marine fossils from the late Mississippian (geology), Mississippian subperiod, about 324 million years ago. It is expo ...

Lagerstätte A Fossil-Lagerstätte (, from ''Lager'' 'storage, lair' '' Stätte'' 'place'; plural ''Lagerstätten'') is a sedimentary deposit that preserves an exceptionally high amount of palaeontological information. ''Konzentrat-Lagerstätten'' preserv ...

, during the

Bashkirian The Bashkirian is in the International Commission on Stratigraphy geologic timescale the lowest stage (stratigraphy), stage or oldest age (geology), age of the Pennsylvanian (geology), Pennsylvanian. The Bashkirian age lasted from to Mega annu ...

Stage in

Montana Montana ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Idaho to the west, North Dakota to the east, South Dakota to the southeast, Wyoming to the south, an ...

. The adult form is unknown, as the only fossil specimens are of aborted fetuses or recently born young.Lund, R. 1980. Viviparity and intrauterine feeding in a new holocephalan fish from the Lower Carboniferous of Montana. Science, 209: 697‑699. Sharp teeth and fecal matter in the fossils suggests that ''Delphyodontos'' practiced intrauterine cannibalism, like some modern sharks, such as

sand tiger shark The sand tiger shark (''Carcharias taurus''), grey/gray nurse shark (in Australia), spotted ragged-tooth shark (in South Africa), or blue-nurse sand tiger, is a species of shark that inhabits subtropical and temperate waters worldwide. It inhabit ...

Appearance

According to the fossils, the recently born would have resembled tadpoles with small, but sharp beaks. Because of the evidence suggesting intrauterine cannibalism, ''D. dacriformes'' is assumed to have been carnivorous, though, besides siblings, it is unknown what other organisms they would have eaten.

Etymology

The generic name, ''Delphyodontos'', means "womb tooth", in reference to the sharp, beak-like teeth and their possible habits of intrauterine cannibalism. The specific name, ''dacriformes'', refers to the teardrop-shaped body.

References

Holocephali Monotypic prehistoric cartilaginous fish genera Carboniferous cartilaginous fish Pennsylvanian fish of North America Fossil taxa described in 1980 Natural history of Montana {{paleo-holocephalan-stub