The Pterosaurs were the first group of Vertebrates to master powered flight, going on to become a highly diverse and successful group throughout the Mesozoic, with the largest species approaching the size of light aircraft. The earliest Pterosaur fossils studied by scientists came from the Solnhofen Limestone deposits of southern Germany in the eighteenth century, an area which has produced a huge number of Pterosaur specimens, from a wide range of species. The vast majority of Pterosaur fossils are isolated and often fragmentary bones, typically preserved in two dimensions. However, Solnhofen also produces complete specimens on a fairly regular basis, with the best-preserved specimens being in three dimensions, and often retain traces of soft tissue.
The Solhofen Limestone beds yield some of the last known non-Pterodactyloid ‘Rhamphorhynchoid’ Pterosaurs (which had disappeared by the Cretaceous), as well as early Pterodactyloid Pterosaurs (the group which survived into the Cretaceous), and the more enigmatic non-Pterodactyloid Monofenestratans, from which the Pterodactyloid Pterosaurs (probably) derived. The most diverse Pterosaur group in the Solho1fn Limestone are the Ctenochasmatid Pterodactyloids, long legged Pterosaurs many of which appear to have been specialist filter feeders anf hunters of small aquatic prey.
In a paper published in the journal Palaeontologica Electronica In June 2023, David Hone of the School of Biological and Behavioural Sciences at Queen Mary University of London, René and Bruce Lauer of the Lauer Foundation for Paleontology, Science and Education, and Frederik Spindler of the Dinosaurier Museum Altmühltal, describe a new species of Ctenochasmatid Pterosaur from the Solnhofen Limestime.
The new species is named Petrodactyle wellnhoferi, where 'Petrodactyle' means 'stone-finger' and 'wellnhoferi' honours palaeontologist Peter Wellnhofer, who spent most of his career working on pterosaurs from the Solnhofen. The name 'Petrodactyle' appeared on the cover of Cuvier's first description of a Pterosaur in 1809, although the name he used within the publication was 'Pterodactyle' (since modified to 'Pterodactylus').
The species is described from a single specimen, LF 2809, found in the summer of 2010 in the visitor’s section of the Schaudiberg Quarry near Mülheim, Bavaria, by an unknown collector within the Dritte Rosa Layer of the Mörnsheim Formation, which has been dated to the Lower Tithonian, making it 149.2-147.5 million years old. It was excavated by Ulrich Leonhardt and Roland Pöschl, prepared by Ulrich Leonhardt, and acquired by the Lauer Foundation in March 2015, where it is permanently housed.
The specimen comprises an incomplete subadult individual consisting of the cranium and mandible, seven cervical and 12 dorsal vertebrae, shoulder girdles, a partial pelvis, numerous ribs and gastralia, both wings and one hindlimb. It was almost entirely disarticulated, although many elements remain close to their anatomical neighbours and the specimen is mostly complete. This is an unusual state of affairs, with most Pterosaur specimens from Solnhofen either being articulated or completely disarticulated, with the former presumably indicating rapid burial, while the later suggests the body of the Animal was left exposed to the actions of scavengers, probably while hanging in the water column. Hone et al. suggest that this specimen sank rapidly into deep water, where it lay exposed on the sediment surface for some time, undisturbed by currents or large scavengers.
The specimen appears to be almost fully grown, based on its large size, smooth bone texture, presence of an extensive cranial crest, complete fusion of the sacral vertebrae, the proximal and distal carpals into units, and complete fusion of the extensor tendon process on the first wing phalanx; it only lacks the complete fusion of bones that would be required to consider it fully adult, with the cranial elements being incompletely fused, and the synsacral vertebrae being incompletely fused to the sacrum.
The skull has been partially crushed, and its posterior is less well preserved than the rest, but is on the whole in good condition. It is 258 mm long and 50 mm tall, with a triangular profile. The naso-antorbital fenestra is small, with a maximum length of 67 mm, and positioned unusually far back, with its anteriormost point on the midline of the skull. The orbits are subcircular and large, measuring 25 mm by 26 mm, the upper temporal fenestra is small, about 10 mm wide, while the lower temporal fenestra is narrow and elongate, approximately 29 mm by up to 9 mm. The rostrum is slightly elevated, possibly implying an upturned snout, although the mandible does not show this, possibly indicating this elevation is a product of the skull's crushing. A bony premaxillary crest is present; this is tall and extensive, as much as 32 mm high, and 104 mm long, striated and anteriorly swept.
The teeth of Petrodactyle wellnhoferi are small, up to 5 mm tall, conical, and inward curving. Isolated teeth show a root longer than the crown, and a general 'Banana-shape'. The foremost teeth are the largest, with the teeth becoming progressively smaller further backward in the mouth. Several of the teeth are worn, exposing their dentine layer, and showing that the enamel was quite thick. Combined with the length of the jaw, this would have given Petrodactyle wellnhoferi a strong grip, but not the ability to crush hard prey, suggesting it fed on small Fish, Cephalopods, Crustaceans, and possibly very young Tetrapods.
Petrodactyle wellnhoferi appears to have been a large animal, with a wingspan of slightly over 2 m, making it one of the largest known fossil Pterosaurs from Solnhofen, despite not being fully grown. As such it is possible that it is a representative of a species already described, from a smaller, more immature specimen. However, Hone et al. reject this hypothesis, on the basis that most Pterosaurs retained much the same structure as they grew, with the exception of features such as crests, which are assumed to have been sexual signalling devices, and typically did not appear until the Animal was close to mature. Thus, the presence of a large crest in Petrodactyle wellnhoferi may be another sign of it being close to maturity. Some Pterosaur species appear to have shown sexual dimorphism, with two morphs, only one of which (presumably the male) developed large crests. However, this does not appear to have been the case in all species, with some species having crests on all known specimens, and sufficient specimens known to make it unlikely all were male. Therefore, the sex of Petrodactyle wellnhoferi cannot be determined.
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