Pterosaurs of the Isle of Wight - Istiodactylus, an Isle of Wight istiodactylid pterosaur

Istiodactylus,

an Isle of Wight istiodactylid pterosaur

Istiodactylus skeleton

Meaning

Sail finger

Wingspan

2 metres (6 feet)

Classification

Pterosauria,
Pterodactyloidea,
Istiodactylidae Howse et al, 2001

Istiodactylus latidens Howse, Milner & Martill, 2001 (formerly Ornithodesmus, Seeley, 1901)

Locations

Sandown

A pterodactyloid, it has no tail, but does have a mouth full of teeth, used to catch fish while in flight

Istiodactylus was not always known as this, as the holotype is actually material belonging to the dinosaur Ornithodesmus, which was originally mistaken for bird and then pterosaur material, but once the specimen was designated dinosaur, the later “Ornithodesmus” material had to be renamed.

The skull is elongate, but with a short snout region in front of the nostrils. There is an unusually extensive naso-antorbital fenestra occupying most of the snout. The orbit is anterodorsally capped by a hemispherical tuberosity, and is continuous with a long, narrow suborbital vacuity. The mandible has an abbreviated symphysis, with the mandible deepest at the divergence point of the jaw rami. There are 24 teeth in the upper jaw, which are limited to the prenarial region, and 25, including an anterior median tooth, in the lower jaw.

The teeth are labio-lingually compressed, with pointed crowns and truncated triangular roots, shorter than the crowns. The upper and lower teeth interlock, with the front teeth closely spaced compared to those to the posterior.

The neural arches have tall, steeply sloping laminae, the six shoulder vertebrae, which are fused into a notarium, are completely fused with the neural spines fused as a supraneural plate. The main body of the sternum is deep, with an obtusely bowed leading edge and a transversely triangular keel.

The humerus has an acutely curved deltopectoral crest, with a free margin that terminates beneath the infra-axial surface.

The sternum has a saddle-shaped coracoid facet situated dorsally, and is arranged asymmetrically, which is a primitive feature unique in pterodactyloids.

Material is rare, so please report it if you find some…

HOWSE, S. MILNER, A. R.and MARTILL, D. M. 2001. Pterosaurs.In MARTILL, D. M. and NAISH, D (eds). Dinosaurs of the Isle of Wight. The Palaeontological Association. Field Guide to Fossils 10, 324-335.

WANG, X., KELLNER, A. W. A, ZHOU, Z and CAMPOS, D. d. A. 2005. Pterosaur diversity and faunal turnover in Cretaceous terrestrial ecosystems in China. Nature, 437, 875-879.