''Brychaetus'' is an extinct genus of prehistoric marine bonytongue fish known from 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 ...

to the late

Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

, and northern

Africa Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surfac ...

Taxonomy

''Brychaetus'' contains a single valid species, ''B. muelleri'' from the

Ypresian In the geologic timescale the Ypresian is the oldest age (geology), age or lowest stage (stratigraphy), stratigraphic stage of the Eocene. It spans the time between , is preceded by the Thanetian Age (part of the Paleocene) and is followed by th ...

of England (

London Clay The London Clay Formation is a Sediment#Shores and shallow seas, marine formation (geology), geological formation of Ypresian (early Eocene Epoch, c. 54-50 million years ago) age which outcrop, crops out in the southeast of England. The London C ...

) and the eastern United States (

Nanjemoy Formation The Nanjemoy Formation is a Formation (geology), geologic formation pertaining to both the Wilcox Group and the Pamunkey Group of the eastern United States, stretching across the states of Virginia, Maryland, and the District of Columbia. The f ...

in Maryland and Virginia, Tuscahoma Formation of Mississippi), with specimens from elsewhere being placed only at genus level due to their fragmentary nature. A record of ''B. muelleri'' from the

Paleocene The Paleocene ( ), or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), ...

Niger Niger, officially the Republic of the Niger, is a landlocked country in West Africa. It is a unitary state Geography of Niger#Political geography, bordered by Libya to the Libya–Niger border, north-east, Chad to the Chad–Niger border, east ...

was reassigned to an extinct

arowana Arowanas are freshwater bony fish of the subfamily Osteoglossinae, also known as bony tongues (the latter name is now often reserved for Arapaiminae). In this family of fish, the head is bony and the elongated body is covered by large, heavy sca ...

, '' Scleropages africanus''. Another species, ''B. schnarrenbergeri'' Zotz, 1928, was described from the Eocene of

Alsace Alsace (, ; ) is a cultural region and a territorial collectivity in the Grand Est administrative region of northeastern France, on the west bank of the upper Rhine, next to Germany and Switzerland. In January 2021, it had a population of 1,9 ...

(France), but its assignment to ''Brychaetus'' was later found to be a misidentification. Another species, ''B. caheni'' from the Paleocene of Cabinda (

Angola Angola, officially the Republic of Angola, is a country on the west-Central Africa, central coast of Southern Africa. It is the second-largest Portuguese-speaking world, Portuguese-speaking (Lusophone) country in both total area and List of c ...

), was later reclassified into its own genus, '' Ridewoodichthys.'' It was the first marine bonytongue described from the fossil record; although other marine bonytongues such as ''

Monopteros A monopteros (Ancient Greek: , from: μόνος, 'only, single, alone', and , 'wing'), also called a monopteron or cyclostyle, is a circular colonnade supporting a roof but without any walls.Curl, James Stevens (2006). ''Oxford Dictionary of Archi ...

'' and '' Thrissopterus'' were described before it, they were not initially recognized as bonytongues. It belonged to a now-extinct clade of marine and freshwater bonytongues known as the Phareodontinae, which also contained the well-known '' Phareodus'' and several other species.

Description

Brychaetus muelleri skull and anterior body

''Brychaetus'' had very long teeth which were half bone and half enamel. It is thought to be related to the modern

, although the presence of a sclerotic ossicle in their specimens suggests that they were a deep-water fish unlike modern day arowanas, which are surface feeders.

Paleoecology

The earliest record of ''Brychaetus'' is a dentary from the

Maastrichtian The Maastrichtian ( ) is, in the International Commission on Stratigraphy (ICS) geologic timescale, the latest age (geology), age (uppermost stage (stratigraphy), stage) of the Late Cretaceous epoch (geology), Epoch or Upper Cretaceous series (s ...

Mali Mali, officially the Republic of Mali, is a landlocked country in West Africa. It is the List of African countries by area, eighth-largest country in Africa, with an area of over . The country is bordered to the north by Algeria, to the east b ...

, indicating that it inhabited the

Trans-Saharan seaway The Trans-Saharan seaway was a sea in the present-day Sahara in the Late Cretaceous period to the Early Eocene In the geologic timescale the Ypresian is the oldest age (geology), age or lowest stage (stratigraphy), stratigraphic stage of the Eoce ...

and survived the Cretaceous-Paleogene extinction event. This dentary is relatively gracile compared to the later species. ''Brychaetus'' remains become more common during the Eocene, being known from England,

Denmark Denmark is a Nordic countries, Nordic country in Northern Europe. It is the metropole and most populous constituent of the Kingdom of Denmark,, . also known as the Danish Realm, a constitutionally unitary state that includes the Autonomous a ...

, and the United States (Louisiana, Mississippi, Maryland, and Virginia), and Nigeria, as well as still being known from the Trans-Saharan seaway in Mali. A potential record is also known in teeth and a dentary fragment from the Eocene of

Morocco Morocco, officially the Kingdom of Morocco, is a country in the Maghreb region of North Africa. It has coastlines on the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria to Algeria–Morocc ...

, which was initially identified as ''B. muelleri''; however, the subsequent identification of other concurrent marine osteoglossid genera from the Mediterranean (''Monopteros'' and ''Thrissopterus'') suggests that this identification is questionable. The last record of ''Brychaetus'' is from the late Eocene Yazoo Clay of Louisiana.

References

Osteoglossidae Monotypic prehistoric ray-finned fish genera Late Cretaceous fish of Africa Late Cretaceous bony fish Eocene animals of Africa Eocene fish of Europe Eocene fish of North America Eocene fish of Africa Maastrichtian genus first appearances Ypresian genera Priabonian genus extinctions Fossils of England Fossils of Denmark Fossils of the United States Fossils of Louisiana Fossils of Mississippi Fossils of Morocco Fossils of Nigeria Fossils of Mali Taxa named by Arthur Smith Woodward Fossil taxa described in 1901 {{osteoglossiformes-stub

Taxonomy

Description

Paleoecology

See also

References