Rhacheosaurus, VON MEYER, 1831

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 : 579

RHACHEOSAURUS VON MEYER, 1831

Type species: Rhacheosaurus gracilis Von Meyer, 1831 .

Holotype: lost; however, two plastotypes survive (of vertebral column and hindlimbs), AMNH FR 4804 and NHM R.3961.

Etymology: ‘Spine lizard’. Rhacheos- is the Ancient Greek for backbone or spine, in reference to the holotype, which was a vertebral column with limbs and girdles.

Geological range: The lower Tithonian (hybonotum ammonite zone).

Geographical range: European endemic ( Germany).

Emended diagnosis: Metriorhynchid thalattosuchian with procumbent teeth, with no lateromedially compression, lacking carinae; cranial bones smooth, lacking conspicuous ornamentation; rounded almost 90° angle formed by the lateral and medial processes of the frontal; dorsal margin of the supratemporal arcade is lower than the medial process of the frontal; eyes as large as the supratemporal fenestra; infratemporal flange absent; surangular and angular well-developed extending rostrally beyond the orbits; symphysial part of the mandible is low, only about 15-mm high; lateral margin of the prefrontals is rounded; external nares not wholly bifurcated by premaxillary septum; external nares begins just after the first premaxillary alveolus, and does not exceed the first maxillary alveolus; humerus deltopectoral crest absent; hypocercal tail possesses a fleshy upper lobe.