''Atractosteus'' (from Greek ''atraktos'' (ἀτρακτὀς), 'spindle' and ''osteon'' (ὀστέον), 'bone') is a genus of gars in the family Lepisosteidae, with three extant species. It is one of two surviving gar genera alongside '' Lepisosteus''. The three surviving species are all widely separated from one another, with ''A. spatula'' being found in the south-central United States, ''A. tropicus'' in southern Mexico and Central America, and ''A. tristoechus'' in Cuba. Although generally inhabiting fresh water, they are tolerant of marine conditions.

Evolution

The genus first appeared during the

Santonian The Santonian is an age in the geologic timescale or a chronostratigraphic stage. It is a subdivision of the Late Cretaceous Epoch or Upper Cretaceous Series. It spans the time between 86.3 ± 0.7 mya ( million years ago) and 83.6 ± 0.7 m ...

stage of the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...

, having diverged from ''Lepisosteus'' earlier in the Cretaceous. It quickly achieved a widespread distribution throughout the rest of the Cretaceous, being known from North America, South America and Europe. ''Atractosteus'' survived the Cretaceous-Paleogene extinction event, with one articulated fossil of the species '' A. grandei'' being recovered from strata dated to just a few thousand years after the extinction event, making it the oldest known articulated vertebrate fossil from the

Cenozoic The Cenozoic Era ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterized by the dominance of mammals, insects, birds and angiosperms (flowering plants). It is the latest of three g ...

. It was found throughout North America and Europe during the

Paleogene The Paleogene Period ( ; also spelled Palaeogene or Palæogene) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period Ma (million years ago) to the beginning of the Neogene Period Ma. It is the fir ...

, but by the

Neogene The Neogene ( ,) is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period million years ago ( Mya) to the beginning of the present Quaternary Period million years ago. It is the second period of th ...

this had shrunk to only certain parts of North America, where it is still found today.

Systematics

Species

Extant species

Fossil species

The following fossil species are known: *†'' Atractosteus atrox'' (Leidy, 1873) * †'' Atractosteus grandei'' Brownstein & Lyson, 2022 * †'' Atractosteus messelensis'' Grande 2010 * †'' Atractosteus simplex'' (Leidy 1873) Former fossil species: * †'' Atractosteus cuneatus'' (Cope 1884) non (Cope 1878) (now in '' Cuneatus'') * †'' Atractosteus falipoui'' (Cavin & Brito 2001) (now in '' Oniichthys'')

Dubious fossil species

* † "''Atractosteus''" ''africanus'' (Arambourg & Joleaud, 1943) (''nomen dubium'', placement in ''Atractosteus'' disputed, often placed in the dubious genus ''Paralepisosteus'') * †"''Atractosteus''" ''emmonsi'' Hay 1929 (

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

of North Carolina, ''nomen dubium'') * †"''Atractosteus''" ''lapidosus'' Hay 1919 (

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

of Florida, ''nomen dubium'') * †''Atractosteus occidentalis'' (Leidy 1856) non Wiley 1976 (Campanian of Montana, ''nomen dubium'') The extinct ''

nomen dubium In binomial nomenclature, a ''nomen dubium'' (Latin for "doubtful name", plural ''nomina dubia'') is a scientific name that is of unknown or doubtful application. Zoology In case of a ''nomen dubium,'' it may be impossible to determine whether a ...

'' fossil species ''A. strausi'' (Kinkelin, 1884) is based on a single

-aged gar scale from Germany, and has often been used as the species for the ''Atractosteus'' gars from the older Messel Formation. Although this scale provides evidence for gars surviving in Europe as late as the Miocene, it is not diagnostic enough to be considered a member of ''Atractosteus'', nor can the Messel gars (now placed in '' A. messelensis'') be confidently placed in it.

References

* Lepisosteidae Taxa named by Constantine Samuel Rafinesque Extant Late Cretaceous first appearances {{Lepisosteiformes-stub