Name: Istiodactylus latidens
Name Meaning: Sail finger (Greek) wide tooth (Latin)
Age: Early Cretaceous
Location: Southern Britain
Istiodactylus is a genus of large pterosaur known from two species across the globe. Of these species, Istiodactylus latidens was the first discovered, but it wasn’t initially named as such. The genus originally came to light in the late 1800s, when palaeontologist Harry G. Seeley found fragmentary remains in deposits on the Isle of Wight. However, he thought these belonged to a dinosaur-like bird and called the animal Ornithodesmus cluniculus.
Seeley later described pterosaur material from the Isle of Wight and concluded that this material was similar enough to O. cluniculus that it could also be categorised as part of the same genus. This material was then named O. latidens, and he determined that the entire genus was pterodactyloid. The story gets more complicated when later analyses revealed that the material of O. cluniculus and O. latidens were dissimilar enough for the former to not be a pterosaur at all. The primary material Seeley found was reclassified as a maniraptoran dinosaur under its original name of Ornithodesmus cluniculus. All pterosaur-like material was subsequently moved to the genus Istiodactylus while retaining the original species name latidens.
The reconstruction of the skull of Istiodactylus latidens has been as convoluted as the initial nomenclature of the animal. The first reconstructions in the early 1900s showed the skull was approximately 560 mm in length, based on the in situ (the position in which it was found) cranial material. However, this effort ignored certain elements of the skull. The head of this pterosaur is now almost completely known from numerous individuals, and a reconstruction by Mark Witton suggests the skull was shorter than previously estimated, reaching a maximum length of 450 mm. This implies that the jaws took up less than 80% of the skull length, and that the animal had a broad, rounded snout, with up to 48 razor-edged teeth.
Members of the Istiodactylidae group, to which Istiodactylus belongs, all share a similar cranial structure. The group includes seven species, one of which is the second Istiodactylus, Istiodactylus sinensis, recovered from Liaoning, China. This second species was much smaller than its English cousin, despite also being known from adult remains.
The unique cranial morphology of Istiodactylus latidens indicates they exhibited specialised foraging behaviour. In the past, it was assumed that they were piscivores or even filter-feeders, yet more recent studies have determined that Istiodactylus’ teeth were adapted for shearing large mouthfuls of meat. Ensuing research has concluded that Istiodactylus latidens had a skull with carnivorous adaptations, but without the reinforcement required for taking on live prey. This morphology is seen in modern scavenging birds, so it is theorised that Istiodactylus was a scavenger. Likewise, their reduced eye size may correlate with the lack of need to find elusive prey.
Due to its diet, Istiodactylus was likely a powerful, soaring pterosaur, as it needed to find and consume carcasses ahead of ground-dwelling predators. It was also adapted for terrestrial launches, which is corroborated by the sedimentological and palaeoenvironmental context of where they have been found.
Istiodactylus has had a long, twisting history. Nevertheless, it was a unique type of pterosaur living in a world ruled by earthbound predators, and its differential diet meant it was able to thrive spatially throughout the Early Cretaceous.
 A group of Istiodactylus escaping from a Baryonyx trying to catch them while scavenging on an iguanodontid carcass. Early Cretaceous of England. Artwork by Gabriel Ugueto.
 An updated restoration of the skull of Istiodactylus latidens. Scale bar = 50 mm. Reconstruction by Mark Witton.
Information References and Further Sources
 Andres, B., and Qiang, J. (2006). ‘A New Species of Istiodactylus (Pterosauria, Pterodactyloidea) from the Lower Cretaceous of Liaoning, China’, Journal of Vertebrate Anatomy, 26 (1), pp. 70-78. Accessed 11th March 2021. Click Here.
 Hooley, R. W. (1913). ‘On the Skeleton of Ornithodesmus latidens; an Ornithosaur from the Wealden Shales of Atherfield (Isle of Wight)’, Quarterly Journal of the Geological Society, 69 (1-4), pp. 372-422. Accessed 11th March 2021. Click Here.
 Howse, S. C. B., and Milner, A. R. (1993). ‘Ornithodesmus – A Maniraptoran Theropod Dinosaur from the Lower Cretaceous of the Isle of Wight, England’, Palaeontology, 36 (2), pp. 425-437. Accessed 11th March 2021. Click Here.
 Seeley, H. G. (1887). ‘On a Sacrum, apparently indicating a new type of Bird, Ornithodesmus cluniculus, Seeley, from the Wealden of Brook’, Quarterly Journal of the Geological Society of London, 43 (1-4), pp. 206-211. Accessed 11th March 2021. Click Here.
 Witton, M. P. (2012). ‘New Insights into the Skull of Istiodactylus latidens (Ornithocheiroidea, Pterodactyloidea)’, PLOS ONE, 7 (3): e33170. Accessed 11th March 2021. Click Here.