''Angolasaurus'' ("

Angola , national_anthem = "Angola Avante"() , image_map = , map_caption = , capital = Luanda , religion = , religion_year = 2020 , religion_ref = , coordina ...

lizard") is an extinct genus of mosasaur. Definite remains from this genus have been recovered from the

Turonian The Turonian is, in the ICS' geologic timescale, the second age in the Late Cretaceous Epoch, or a stage in the Upper Cretaceous Series. It spans the time between 93.9 ± 0.8 Ma and 89.8 ± 1 Ma (million years ago). The Turonian is preceded ...

and

Coniacian The Coniacian is an age or stage in the geologic timescale. It is a subdivision of the Late Cretaceous Epoch or Upper Cretaceous Series and spans the time between 89.8 ± 1 Ma and 86.3 ± 0.7 Ma (million years ago). The Coniacian is preceded b ...

Angola , national_anthem = "Angola Avante"() , image_map = , map_caption = , capital = Luanda , religion = , religion_year = 2020 , religion_ref = , coordina ...

, and possibly the

of the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., federal district, five ma ...

, the

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

, and the

Maastrichtian The Maastrichtian () is, in the ICS geologic timescale, the latest age (uppermost stage) of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interv ...

Niger ) , official_languages = , languages_type = National languagesPlatecarpus ''Platecarpus'' ("flat wrist") is an extinct genus of aquatic lizards belonging to the mosasaur family, living around 84–81 million years ago during the middle Santonian to early Campanian, of the Late Cretaceous period. Fossils have been fou ...

'', recent phylogenetic analyses have placed it between the (then) plioplatecarpines '' Ectenosaurus'' and '' Selmasaurus'', maintaining a basal position within the plioplatecarpinae. Its wide geographic range make it the one of the only

mosasaur Mosasaurs (from Latin ''Mosa'' meaning the 'Meuse', and Ancient Greek, Greek ' meaning 'lizard') comprise a group of extinct, large marine reptiles from the Late Cretaceous. Their first fossil remains were discovered in a limestone quarry at Ma ...

s with a transatlantic range.

Description

''Angolasaurus'' was a small mosasaur, with a total length of about 4 meters (13 feet). It shared much of a body plan with its relative ''

Platecarpus ''Platecarpus'' ("flat wrist") is an extinct genus of aquatic lizards belonging to the mosasaur family, living around 84–81 million years ago during the middle Santonian to early Campanian, of the Late Cretaceous period. Fossils have been fou ...

'', but with a slightly longer skull relative to body length. Its skull housed 11 maxillary teeth, 4 premaxillary teeth, and 12 dentary teeth. The phylogenetic relationship of ''Angolasaurus'' indicates that individuals of this genus possessed a tail fluke, more forward-lying nostrils, and keeled scales for hydrodynamic efficiency. Due to declining sea temperatures in the area that ''Angolasaurus'' inhabited, as well as the later Bientiaba locality, it has been hypothesized that it and the other mosasaurs inhabiting its region may have had an increased coverage of dark patterning on its dorsal surface to aid in thermoregulation.

History of discovery

First named in 1964 by Miguel Telles Antunes on the basis of a partial skull and skeleton, ''Angolasaurus'' was reassigned in 1994 to the genus ''

''. This placement was subsequently struck down in studies in 2005, which nested it within the

plioplatecarpinae Plioplatecarpinae is a subfamily of mosasaurs, a diverse group of Late Cretaceous marine squamates. Members of the subfamily are informally and collectively known as "plioplatecarpines" and have been recovered from all continents, though the occ ...

. Fieldwork between 2005 and 2009 recovered at least two new ''Angolasaurus'' skeletons. One new skull as well as the type skull were CT scanned to reveal intricate details of the interior braincase that allowed for a more concrete placement within the

. The most recent major phylogenetic analysis conducted on the

idae placed ''Angolasaurus'' as basal to the clade composed of the russellosaurine subfamilies

Tylosaurinae The Tylosaurinae are a subfamily of mosasaurs,Williston, S. W. 1897. Range and distribution of the mosasaurs with remarks on synonymy. ''Kansas University Quarterly'' 4(4):177-185. a diverse group of Late Cretaceous marine squamates. Members of ...

and Plioplatecarpinae, and part of neither. In 2007, two individuals from the Eagle Ford Formation of

Texas Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...

were described as belonging to the genus ''Angolasaurus'', one of which preserved part of the hyoid apparatus. The same abstract assigned two teeth previously assigned to ''

'' to ''Angolasaurus''. These teeth came from the

Sergipe Sergipe (), officially State of Sergipe, is a state of Brazil. Located in the Northeast Region along the Atlantic coast of the country, Sergipe is the smallest state in Brazil by geographical area at , larger only than the Federal District. S ...

Basin of

, and are virtually indistinguishable from those found in the holotype of ''Angolasaurus bocagei''. These discoveries made ''Angolasaurus'' the first known

genus with a transatlantic distribution.

Paleoecology

Angola

''Angolasaurus'' ''bocagei'', recovered only from the

Itombe Formation The Itombe Formation is a geological formation of the Kwanza Basin in Angola dated to the Coniacian stage of the Late Cretaceous. The environment of deposition is shallow marine. Reptile fossils have been recovered from the Tadi beds locality wit ...

, shared its habitat with the tylosaurine species ''

Tylosaurus ''Tylosaurus'' (from the ancient Greek (') 'protuberance, knob' + Greek (') 'lizard') is a genus of mosasaur, a large, predatory marine reptile closely related to modern monitor lizards and to snakes, from the Late Cretaceous. Description A ...

'' (formerly ''Mosasaurus'') ''iembeensis'' and the durophagous shallow-water

turtle Turtles are an order of reptiles known as Testudines, characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden necked ...

Angolachelys ''Angolachelys'' is an extinct genus of African eucryptodiran turtle which existed in Angola , national_anthem = "Angola Avante"() , image_map = , map_caption = , capital = Luanda , rel ...

''. Indeterminate

halisaurine The Halisaurinae are a subfamily of mosasaurs, a group of Late Cretaceous marine lizards. They were small to medium-sized, ranging from just under 3 meters in ''Eonatator sternbergi'' to as much as 8 or 9 meters in ''Pluridens serpentis''. The ...

and plesiosaur remains have also been recovered from this region. Terrestrial fauna consisted solely of the sauropod ''

Angolatitan ''Angolatitan'' (meaning "Angolan giant") is a genus of titanosauriform sauropod dinosaur from the Upper Cretaceous. It is also the first non-avian dinosaur discovered in Angola. The genus contains a single species, ''Angolatitan adamastor'', kn ...

''.

Niger

Known from the

Dukamaje Formation The Dukamaje Formation is a geological formation in Niger whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation.Weishampel, David B; et al. (2004). "Dinosaur distribution ( ...

on the basis of a few vertebrae of varying ontogenetic stages, ''Angolasaurus'' coexisted here with fellow

plioplatecarpine Plioplatecarpinae is a subfamily of mosasaurs, a diverse group of Late Cretaceous marine squamates. Members of the subfamily are informally and collectively known as "plioplatecarpines" and have been recovered from all continents, though the occu ...

genera ''

'' and '' Plioplatecarpus,'' the globidensine genus '' Igdamanosaurus,'' the

genus ''

Halisaurus ''Halisaurus'' is an extinct genus of marine reptile belonging to the mosasaur family. The holotype, consisting of an angular and a basicranium fragment discovered near Hornerstown, New Jersey, already revealed a relatively unique combination ...

'', the

mosasaurine The Mosasaurinae are a subfamily of mosasaurs, a diverse group of Late Cretaceous marine squamates. Members of the subfamily are informally and collectively known as "mosasaurines" and their fossils have been recovered from every continent except ...

genus ''

Mosasaurus ''Mosasaurus'' (; "lizard of the Meuse River") is the type genus (defining example) of the mosasaurs, an extinct group of aquatic squamate reptiles. It lived from about 82 to 66 million years ago during the Campanian and Maastrichtian stages ...

'', and the

id genus '' Goronyosaurus''.

United States

''Angolasaurus'' is known from the Eagle Ford Formation of

. Other Turonian aquatic reptiles from the Eagle Ford Formation include the

plesiosaurs The Plesiosauria (; Greek: πλησίος, ''plesios'', meaning "near to" and ''sauros'', meaning "lizard") or plesiosaurs are an order or clade of extinct Mesozoic marine reptiles, belonging to the Sauropterygia. Plesiosaurs first appeared ...

Polyptychodon ''Polyptychodon'' (meaning 'shaped fin tooth') is a genus of pliosaurid found in Middle-Late Cretaceous marine deposits in southern England, France and Argentina. It has been considered a ''nomen dubium'' in a 2016 review. History of discovery ...

Libonectes ''Libonectes'' is an extinct genus of sauropterygian reptile belonging to the plesiosaur order. It is known from specimens found in the Britton Formation of Texas (USA) and the Akrabou Formation of Morocco, which have been dated to the lower Tur ...

Cimoliasaurus ''Cimoliasaurus'' was a plesiosaur that lived during the Late Cretaceous (Maastrichtian) of New Jersey. It grew up to long and weighed up to . Etymology The name is derived from the Greek , meaning "white chalk", and , meaning "lizard", in ...

,'' and ''

Plesiosaurus ''Plesiosaurus'' (Greek: ' ('), near to + ' ('), lizard) is a genus of extinct, large marine sauropterygian reptile that lived during the Early Jurassic. It is known by nearly complete skeletons from the Lias of England. It is distinguishable by ...

'', and the mosasaur ''Clidastes''. Indeterminate mosasaur and plesiosaur remains are also known from here.

References

{{Taxonbar, from=Q4763802 Russellosaurins Maastrichtian genus extinctions Mosasaurs of Africa Mosasaurs of North America Cretaceous Niger Fossils of Niger Fossil taxa described in 1964 Taxa named by Miguel Telles Antunes Mosasaurs of South America Turonian genus first appearances Coniacian genera Santonian genera Campanian genera