| Anguanax | |
|---|---|
 | |
| Partial skull | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Superorder: | †Sauropterygia |
| Order: | †Plesiosauria |
| Family: | †Pliosauridae |
| Genus: | †Anguanax Cau & Fanti,2015 |
| Type species | |
| †Anguanax zignoi Cau & Fanti, 2015 | |
Anguanax is anextinctgenus ofbasalpliosaurid known from theLate Jurassic (Oxfordian stage)Rosso Ammonitico Veronese Formation of northernItaly. It contains asingle species,Anguanax zignoi, known from a partially complete individual, representing the first articulatedskeleton of an Italianplesiosaurian.[1]
Anguanax is known solely from theholotype MPPL 18797, currently housed at the Museo Paleontologico e della Preistoria ‘P. Leonardi’ inFerrara. Theskeleton, still articulated in several blocks oflimestone, consists of a partialskull including thelower jaw, 32 isolatedteeth, neck, back and tailvertebrae, a rightpectoral girdle, a partial lefthumerus, a leftradius, a leftulna, three leftcarpals, a partialpelvis, afemur, two epipodials, isolated metapodials andphalanges. It was collected during the 1980s from a nodular and cherty limestone interval at the Kaberlaba quarry in theAsiago Municipality of theVicenza Province of northern Italy. This interval belongs to Lithozone 5 of the Middle Unit of theRosso Ammonitico Veronese Formation which dates to the middleOxfordian stage of the earlyLate Jurassic, about 160million years ago. This quarry was first briefly mentioned byAchille de Zigno in 1883, who collected a series of vertebrae and other elements from the neighboring Cesuna quarry. The remains originally described as being exclusivelyplesiosaurian by Zigno, were subsequently identified to includecrocodylomorph elements among them, although neither of which can be identified to the family level. Since then, the first identifiablemarine reptile was collected and named from the upper units of the formation - themetriorhynchid crocodylomorphNeptunidraco ammoniticus which is known from several specimens.[1]
Despite its discovery during the 1980s, MPPL 18797 was only first thoroughly described by Andrea Cau and Federico Fanti in 2014, and was found to represent the first articulated skeleton of an Italianplesiosaurian. The large size of the skull compared to the rest of the skeleton, as well as the presence of alacrimal bone, and a distinct front-side facing projection of theprefrontal into theorbital margin, allowed to easily identify the specimen as belonging toPliosauridae.[2] The specimen was named in2015 by Cau and Fanti following the preparation of additional bones, with thetype species beingAnguanax zignoi. Thegeneric name is derived fromAnguana, an aquatic creature with bothfish andreptilian traits present in North Eastern Italian mythologies, and fromanax,Greek for alord, a "tribal and military leader". Thespecific name honors Zigno for discovering the first plesiosaurian remains from the Rosso Ammonitico Veronese Formation.[1]
Anguanax is a medium-sizedcarnivorousbasalpliosaurid, at an estimated body length of about 3–4 m (9.8–13.1 ft).[2] Its general body proportions are similar to those of other early pliosaurid, for example the well-preservedPeloneustes.Anguanax fed on soft or small-bodied prey in theupper pelagic zone of its environment, as suggested by its moderately expanded side-facingeye sockets, the gracile and relatively long lower jaw, and the small, slender, and slightly curved teeth with fine serrations.[1][2]
Anguanax possesses two unique traits among otherplesiosaurians including a projection on thepalpebral placed at midheight of the front-facing margin of the eye socket; and a posteroventral process ofcoracoid developed as a distincttrapezoid that does not reach theglenoid level from the side, and with a straight margin directed back and to the side from its back facing position. Additionally, other traits are relatively rare inpliosaurids and thus their combination inAnguanax distinguishes it from other pliosaurids. These include narrow axialneural spines, a back-directed retroarticular projection on the vertebrae, a hill on the coronoid depression, a stepped posteroventral corner of the back margin of the eye socket, rib facets that are placed dorsally oncaudal vertebrae but does not extended to the neural arches, and frontcervical centra that bear a low and broad midline ridge on their bottom surface.[1]
Aphylogenetic analysis was performed by Cau and Fanti in 2015 in order to resolveAnguanax position among other pliosaurids. They used the large species-level data-set of Benson and Druckenmiller (2014) that includes most known plesiosaurians, and recoveredAnguanax as a non-thalassophonean pliosaurid. As in the original analysis of Benson and Druckenmiller (2014), advanced pliosaurids form a largepolytomy unless fragmentary species are removed orstratigraphic assumptions are made. The followingcladogram is simplified after this analysis, showing only the relationships inside Pliosauridae.[1]
| Pliosauridae |
| |||||||||||||||||||||||||||||||||||||||||||||||||||
.png)