Aggiosaurus, AMBAYRAC, 1913

Young, Mark Thomas & Andrade, Marco Brandalise De, 2009, What is Geosaurus? Redescription of Geosaurus giganteus (Thalattosuchia: Metriorhynchidae) from the Upper Jurassic of Bayern, Germany, Zoological Journal of the Linnean Society 157 (3), pp. 551-585 : 578-579

AGGIOSAURUS AMBAYRAC, 1913 B

Type species: Dakosaurus maximus (Plieninger, 1846) Von Quenstedt, 1856 .

Valid species: Dakosaurus maximus (Plieninger, 1846) Von Quenstedt, 1856 .

Holotype: lost; therefore, we designate SMNS 8203 (incomplete skull and mandible) as the neotype of the species (and the type specimen of the genus). Dakosaurus manselii (Hulke, 1870) Woodward, 1885 .

Holotype: NHM 40103, incomplete skull and mandible.

Dakosaurus andiniensis Vignaud & Gasparini, 1996 .

Holotype: MHNSR PV344 , poorly preserved snout Dakosaurus nicaeensis (Ambayrac, 1913b) comb. nov.

Holotype: Muséum d’Historie Naturelle Nice unnumbered, poorly preserved upper jaw, with teeth preserved in limestone.

Teeth taxa: Most of the isolated teeth of Dakosaurus recovered in Europe have automatically been assigned to D. maximus . However, as the phylogeny has demonstrated, the contemporaneous species D. maximus and D. manselii have distinct cranial apomorphies. As such, only teeth from the Swabian Alb of the upper Kimmeridgian and lower Tithonian are here considered as belonging to D. maximus . All other isolated teeth are hereby referred to Dakosaurus sp. until further studies can determine if the crowns possess species-level apomorphies.

Invalid species: Dakosaurus amazonicus was erected by Giebel (1870) for vertebrae and teeth found in the Amazon. However, Gervais (1876) erected the name Dinosuchus terror (currently considered an alligatorid closely related to Purussaurus ) for the material.

Giebel (1876) considered Dinosuchus terror to be a junior synonym of Dakosaurus amazonicus .

Possibly valid species (1): Dakosaurus lissocephalus Seeley, 1869 ( CAMSM J.29419). Comparison between D. maximus ( SMNS 8203) and the holotypes of D. manselii and D. lissocephalus leads to the conclusion that D. manselii and D. lissocephalus are not conspecific ( MTY, pers. obs.), because of the shape of the supratemporal fenestra, squamosal, and parietal in D. lissocephalus being much more reminiscent of D. andiniensis and D. maximus , than of D. manselii . However, until better-preserved material is found from Ely, Cambridgeshire, the synonymy between D. maximus and D. lissocephalus must remain provisional.

Possibly valid species (2): Isolated Dakosaurus teeth have long been known from the lower Oxfordian of England (Lydekker, 1890) and the Middle Oxfordian of Poland (Jentzsch, 1884; Gallinek, 1895). These teeth are far smaller and less robust than those from the upper Oxfordian onwards, and possibly represent a distinct species.

Etymology: ‘Tearing lizard’. Dakos- is the Ancient Greek for to tear, referring to the large, lateromedially compressed, and serrated teeth.

Geological range: From the lower Oxfordian (mariae ammonite zone; NHM 47989) to the lower Berriasian (Gasparini et al., 2006).

Geographical range: Cosmopolitan ( Argentina, UK, France, Germany, Mexico, Poland, Russia, and Switzerland).

Emended diagnosis: Metriorhynchid thalattosuchian with large robust teeth, with little lateromedially compression, and the carinae formed by denticles wider transversely than in the root-apex direction; cranial bones smooth, lacking conspicuous ornamentation; acute angle formed by the lateral and medial processes of the frontal; the supratemporal fenestrae reach the minimum intraorbital distance; the lateral mandibular groove possesses a well-developed foramen at either end; surangular poorly developed, terminating caudal to the anterior margin of the orbit; distance between the ventral margin of the antorbital fenestra and ventral margin of the tooth row is greater than the diameter of the antorbital fenestrae; cross-sectional thickness of cranial bone generally> 1.5 mm.