Angolasaurus

Angolasaurus ("Angola lizard") is an extinct genus of mosasaur. Definite remains from this genus have been recovered from the Turonian of Angola, and possibly the Turonian of the United States and Brazil, and the Maastrichtian of Niger. While at one point considered a species of "Platecarpus", 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 Turonian Mosasaurs 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", 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 "Platecarpus". This placement was subsequently struck down in studies in 2005, which nested it within the plioplatecarpinae. 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 plioplatecarpinae. The most recent major phylogenetic analysis conducted on the mosasauridae placed "Angolasaurus" as basal to the clade composed of the russellosaurine subfamilies Tylosaurinae and Plioplatecarpinae, and part of neither.
In 2007, two individuals from the Eagle Ford Formation of Texas 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 "Platecarpus" to "Angolasaurus". These teeth came from the Sergipe Basin of Brazil, and are virtually indistinguishable from those found in the holotype of "Angolasaurus bocagei". These discoveries made "Angolasaurus" the first known Turonian mosasaur genus with a transatlantic distribution.
Paleoecology.
Angola.
"Angolasaurus" "bocagei", recovered only from the Itombe Formation, shared its habitat with the tylosaurine species "Tylosaurus" (formerly Mosasaurus) "iembeensis" and the durophagous shallow-water turtle "Angolachelys". Indeterminate halisaurine and plesiosaur remains have also been recovered from this region. Terrestrial fauna consisted of the sauropod Angolatitan.
Niger.
Known from the Dukamaje Formation on the basis of a few vertebrae of varying ontogenetic stages, "Angolasaurus" coexisted here with fellow plioplatecarpine genera "Platecarpus" and "Plioplatecarpus," the globidensine genus "Igdamanosaurus," the halisaurine genus "Halisaurus", the mosasaurine genus "Mosasaurus", and the mosasaurid genus "Goronyosaurus".
United States.
"Angolasaurus" is known from the Eagle Ford Formation of Texas. Other Turonian aquatic reptiles from the Eagle Ford Formation include the plesiosaurs "Polyptychodon, Libonectes, Cimoliasaurus," and "Plesiosaurus", and the mosasaur "Clidastes". Indeterminate mosasaur and plesiosaur remains are also known from here.