Angolasaurus

Angolasaurus Temporal range: Turonian-Coniacian 92.1–88 Ma PreꞒ Ꞓ O S D C P T J K Pg N [1][2][3][4]
Partial skeleton (MGUAN-PA 065) at the National Museum of Natural History
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Squamata
Clade:	†Mosasauria
Family:	†Mosasauridae
Clade:	†Russellosaurina
Subfamily:	†Plioplatecarpinae
Genus:	†Angolasaurus Antunes, 1964
Species:	†A. bocagei
Binomial name
†Angolasaurus bocagei Antunes, 1964
Synonyms[3][5][6]
Platecarpus bocagei Lingham-Soliar, 1994

Angolasaurus ("Angola lizard") is an extinct genus of mosasaur. Definite remains from this genus have been recovered from the Turonian and Coniacian of Angola,^[7] and possibly the Coniacian of the United States, the Turonian of Brazil,^[8] and the Maastrichtian of Niger.^[9][10] While at one point considered a species of Platecarpus,^[6] recent phylogenetic analyses have placed it between the (then) plioplatecarpines Ectenosaurus and Selmasaurus, maintaining a basal position within the plioplatecarpinae.^[11]

Its wide geographic range make it one of the only Turonian mosasaurs with a transatlantic range.^[8]

Description

Angolasaurus was a small mosasaur, with a skull length estimated at 40 centimetres (1.3 ft),^[12] suggesting a possible total length of about 4 meters (13 feet) based on the ratio provided by Russell (1967).^[13] It shared much of a body plan with its relative Platecarpus, but with a slightly longer skull relative to body length.^[6] 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,^[14] and keeled scales for hydrodynamic efficiency.^[15]

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.^[16]

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.^[6] This placement was subsequently struck down in studies in 2005, which nested it within the plioplatecarpinae.^[7] 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.^[8] 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.^[17]

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.^[8]

Paleoecology

References

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