Tuesday 14 October 2014

The Rosso Ammonitico Veronese Crocodylomorph.

The Rosso Ammonitico Veronese is a red nodular limestone found on the Trento Plateau in northern Italy, and Middle to Late Jurassic in age. It is noted for its numerous Ammonite fossils, but also produces occasional Marine Reptiles, notably Thalattosuchian Crocodylomorphs and Plesiosaurians. The earliest recorded discovery of such a Reptile is a Crocodylian discovered in 1787 at a quarry on Mount Zovetto, near Tresche, in the Asiago Municipality, though the exact location of this quarry is no longer known. It is currently housed in the Museo Paleontologico dell’Universit├ádi Padova.

The Crocodylomorph was named ‘Steneosaurus barettoni’ in 1883 by Achille de Zigno, though he provided no formal description of the fossil, which makes his naming of the specimen invalid under current rules on taxonomy. The first formal description of the specimen was made by Giovanni Omboni in 1890.

In a paper published in the journal Historical Biology on 4 April 2013, Andrea Cau of the Museo Geologico ‘Giovanni Capellini’ in Bologna redescribes the Rosso Ammonitico Veronese Crocodylomorph, and attempts to resolve its classification.

The Rosso Ammonitico Veronese Crocodylomorph. Photograph (A) and line drawing (B). In (B), dark grey tone indicates preserved bones, light grey tone indicates natural cast of bones on slab and asterisk indicates fragment of mandible overlapped by skull. Scale bar in cm. Cau (2013).

The specimen comprises a partial skull and associated mandible preserved in a limestone slab. The skull is poorly preserved, with most of the left side eroded away. The end of the snout is missing, but preserved as an impression on the slab which preserves some fairly good detail.

As noted before, de Zigno’s naming of the specimen as ‘Steneosaurus barettoni’ is not considered valid under current rules on taxonomy. Furthermore Cau does not find any evidence for the assignation of the specimen to the Teleosauroid genus Steneosaurus, instead referring it to the Geosaurine genus Neptunidraco. Due to the poor preservation of the specimen it is not assigned to a species.

See also…

The Sebecosuchians were the only group of Crocodylomorphs other than the modern Crocodyliforms to survive the end Cretaceous extinction, radiating in South America and Europe during the Palaeogene, then going extinct later in the Tertiary. A variety of South American forms have been described, and the group is reasonably well...

 Crocodylomorphs arose during the Triassic and diversified throughout the Mesozoic, reaching a great diversity of forms by the end of the Cretaceous. However they group were badly affected by the...

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