What is Geosaurus? Redescription of Geosaurus giganteus (Thalattosuchia: Metriorhynchidae) from the Upper Jurassic of Bayern, Germany Author Young, Mark Thomas Author Andrade, Marco Brandalise De text Zoological Journal of the Linnean Society 2009 2009-10-26 157 3 551 585 https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2009.00536.x journal article 10.1111/j.1096-3642.2009.00536.x 0024-4082 5443313 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.