Istiodactylus latidens BMNH R 3877 (Hooley 1913, "Ornithodemus" latidens; Howse, Milner and Martill 2001) ~56 cm skull length, Aptian, Early Cretaceous ~130 mya was an unusual ornithocheirid known from a partial skeleton. It was derived from a sister to Nurhachius and was a sister to SMNK PAL 1136, an otherwise unnamed pterosaur.
Distinct from SMNS PAL 1136, the skull of Istiodactylus was a quarter smaller than SMNK 1136 PAL and similar in size to Coloborhynchus. The long gracile skull was dominated by an antorbital fenestra comprising 63 per cent of its estimated length. The anterior margin of the antorbital fenestra was posterior to all teeth, which fill only the anterior fourth of the jaws. Both narial openings (per side) were dorsal to the teeth. The long quadrates were so inclined that the orbit was positioned even further posteriorly than in PAL 1136. The teeth were lancet-shaped, closely spaced, and interlocked like a bear trap. A central dentary tooth filled the gap left by the medial premaxilla teeth, which were diminutive. The teeth increased in size posterolaterally. Two posterior dentary teeth fit into slots in the premaxilla.
The dorsal vertebral transverse processes were nearly vertical. Large postexapophyses appeared on each cervical centrum. A notarium of six vertebrae was present.
Asymmetrical coracoidal articulations on the anterior edge of the deep sternal complex keel continued on the lateral surface. The reconstructed wing/torso ratio was estimated at ~9:1.The deltopectoral crest was warped into a spiral. The ulna had a ridge that supported the radius. The antebrachium was relatively longer than in PAL 1136. What Hooley identfied as an ischium is identified here as the pubis and ischium.
?Pterodactylus giganteus (Bowerbank 1846, 1851, 1852, at right above) = Ornithocheirus giganteus is represented by a rostrum and a few other pieces including a fused scapulocoracoid. The rostral crest is low. The two nares appear to be relatively large and close together. The mandible has a very shallow keel.
The ornithocheirid family tree is here. The entire pterosaur family tree is here.