Malawania

Malawania; Temporal range: Early Cretaceous, 132–125 Ma PreꞒ Ꞓ O S D C P T J K Pg N
	Restoration
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	†Ichthyosauria
Family:	†Ichthyosauridae
Genus:	†Malawania; Fischer et al., 2013
Type species
	†Malawania anachronus; Fischer et al., 2013

Malawania is an extinct genus of basal thunnosaur ichthyosaur known from the middle Early Cretaceous (Hauterivian or Barremian stage) of Iraq. Malawania was named by Valentin Fischer, Robert M. Appleby, Darren Naish, Jeff Liston, Riding, J. B., Brindley, S. and Pascal Godefroit in 2013 and the type species is Malawania anachronus.^[1] It is unusual as it is much more primitive than other Cretaceous ichthyosaurs, being most closely related to Ichthyosaurus from the Late Triassic and Early Jurassic, over 70 million years earlier than Malawania, with all other known ichthyosaurs from the Late Jurassic onwards belonging to the family Ophthalmosauridae.

Discovery[]

The holotype and only known specimen was discovered in 1952 by British petroleum geologists D. M. Morton, F. R. S. Henson, R. J. Wetzel and L. C. F. Damesin while working in Chia Gara, Amadia in Iraqi Kurdistan. The slab was being used to dam a small river and was part of a mule track. It was then transported back to the UK and donated to the Natural History Museum in 1959. Robert M. Appleby would study the specimen for many years until his death in 2004, but never published a paper, one manuscript submitted to Paleontology in 1979 was rejected due to the uncertain provenance of the specimen.^[2] The specimen was formally described in 2013 by Fischer and colleagues. Using palynology it was determined that the rocks surrounding the specimen were Hauterivian-Barremian in age, which was unexpected given the archaic nature of the specimen.^[1]

Description[]

The lacrimals (paired bones at the front edges of the orbits) have long backwards projections, extending along half the length of the lower edges of the orbits (eye sockets). The front region of each lacrimal bears a triangular hollow. Fischer and colleagues speculated that these might house the lacrimal glands (which produce the tear film). The sclerotic rings (rings of plates that supported the eyeballs) are each composed of 13 individual bones.^[1]

Malawania has at least five neck vertebrae. The first two are fused together, with the boundary between them visible. The first vertebra about twice the length of the second. The neural spines of the vertebrae in the neck and front trunk are shaped like trapezoids and widely spaced, a unique feature of the genus. All of the centra (vertebral bodies) preserved in Malawania are of equal length. In some of the trunk vertebrae, two pairs of outwards projections (the diapophyses and parapophyses) flow together smoothly with the centra, similar to ichthyosaurs outside of Parvipelvia. Like other thunnosaurs, the ribs of Malawania have cross-sections with a figure eight-shape.^[1]

The front edges of the scapulae (shoulder blades) of Malawania are straight, differing from baracromians. The humeri (upper arm bones) of Malawania are short and shaped like trapezoids, unique to this genus. The upper end of each humerus bears a backwards-pointing projection known as a capitular process. This is unique to Malawania; in other ichthyosaurs, these processes are semicircular. The humeri are not constricted, unlike most other neoichthyosaurs outside of Ophthalmosauridae. The lower ends of the humeri have surfaces for articulating with two bones and are not expanded. The unnotched, hexagonal lower arm bones (radii and ulnae) are narrower than long. There is no space between them.^[1]

The radiales (carpals below the radii) are shaped like rhombi, a condition also seen in Macgowania, while almost all the rest of the bones of the hand are shaped like hexagons. They interlock in a mosaic-like structure, as in some early diverging neoichthyosaurs as well as Macgowania. The intermedia (a pair of wrist bones) approach the size of the radii, distinctive of Malawania. Two digits originate from each intermedium, similar to Ichthyosaurus. There are two other digits in the foreflippers of Malawania for a total of four. The first phalanx (digit bone) of the first digit has a notch. This digit would have had more than nine bones in it when complete.^[1]