Rhacheosaurus, VON MEYER, 1831

Young, Mark T., Brusatte, Stephen L., Ruta, Marcello & Andrade, Marco Brandalise De, 2010, The evolution of Metriorhynchoidea (mesoeucrocodylia, thalattosuchia): an integrated approach using geometric morphometrics, analysis of disparity, and biomechanics, Zoological Journal of the Linnean Society (Zool. J. Linn. Soc.) 158 (4), pp. 801-859 : 851

RHACHEOSAURUS VON MEYER, 1831

Racheosaurus Giebel, 1846 [sic]

Type species: Racheosaurus gracilis von Meyer, 1831 .

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

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

Geological range: Lower Tithonian (hybonotum ammonite zone).

Geographical range: European endemic ( Germany). Diagnosis: Metriorhynchid thalattosuchian with procumbent teeth, with no lateromedial compression, and lacking carinae; cranial bones smooth, and lacking conspicuous ornamentation; rounded, almost 90° angle formed by the lateral and medial processes of the frontal; the 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; the symphysial part of the mandible is low, only about 15-mm high; the lateral margin of the prefrontals is rounded; the external nares are not wholly bifurcated by the premaxillary septum; the external nares begin just after the first premaxillary alveolus, and do not exceed the first maxillary alveolus; the humerus deltopectoral crest is absent; the hypocercal tail possesses a fleshy upper lobe.