Preondactylus: an early pterosaur from the Norian

Preondactylus buffarinii was a small pterosaur from the Norian of what is now north-eastern Italy. Its principal fossil is one incomplete skeleton preserved mainly as a natural impression in a slab of dolomite. The specimen already shows a fully formed wing, a long tail and proportions unlike those of later short-tailed pterodactyloids. It is among the earliest pterosaurs known from a reasonably connected skeleton, but the record is too limited to make it a simple, definitive model of the first stage of pterosaur evolution. It belongs in the pterosaur catalogue with other Triassic forms whose anatomy is only partly known.

Quick facts

A discovery at Preone

Nando Buffarini found the thin dolomite slab in 1982 near Preone in the Friuli region of north-eastern Italy. Rupert Wild described the pterosaur in 1984 and named the species for its discoverer. The holotype, MFSN 1770, is held by the Friuli Museum of Natural History. Its discovery added one of the rare connected pterosaur skeletons from the Late Triassic to a record otherwise dominated by isolated or incomplete bones.

The fossil was initially exposed on the surface of the slab. During preparation much of the actual bone was lost, leaving a combination of surviving bone and natural impressions. Later study examined both sides of the slab and refined the interpretation of the wrist and metacarpals. That history matters: an impression can preserve the outline and position of a bone even where its internal structure is gone, but fine anatomical details may remain difficult to distinguish.

In 1998 Fabio Marco Dalla Vecchia redescribed the holotype, revising several wing measurements and its anatomical interpretation. Comparisons with Eudimorphodon showed that the earliest pterosaurs were not necessarily arranged in a simple ladder from primitive to advanced. The position of Preondactylus depends on a limited set of characters from a compressed and incomplete specimen.

A complete flight plan by the Norian

The holotype preserves parts of the skull and lower jaw, vertebral column, shoulder girdle, forelimbs and hind limbs. Its tail was long. The metacarpals remained relatively short compared with those of later pterodactyloids, while the greatly elongated fourth finger and its phalanges formed the main extension of the wing. The first three fingers were shorter and retained claws.

This anatomy shows that by the early Norian a pterosaur could already support a broad flight membrane on a specialised fourth finger. The small body and early age of the fossil do not make it the ancestor of every later pterosaur. It is a member of an early radiation, not a preserved snapshot of the moment flight first evolved.

The bones suggest a wingspan of roughly 45–50 centimetres. The estimate is built from the preserved parts and comparisons where gaps remain. It describes an approximate scale, not a complete measured wing. The skull and limb proportions indicate a small animal, but the fossil does not reveal how often it flew, whether it launched from trees or ground, or how it moved through its habitat.

Teeth and possible food

The preserved teeth are small and relatively simple. They do not form the dense comb of a specialised filter feeder or the crushing battery of a shell-eating reptile. Capturing small invertebrates is plausible, but no contents of the holotype's stomach or other direct feeding trace are known. Tooth shape narrows the possibilities without identifying a specific prey item.

Comparisons with Dimorphodon and other early pterosaurs show variation in skull and tooth form. They are useful for testing relationships and potential feeding mechanics, but they do not turn one relative's diet into a documented diet for Preondactylus. Nor does a marine fossil bed prove that this small flyer spent all its time above open water.

The uncertain second specimen

A second slab, MFSN 1891, was described in 1989 from the same Rio Seazza dolomite. It contains tiny, scattered bones interpreted as the remains of a small pterosaur that may have passed through the digestive tract of a larger fish and then been regurgitated. The specimen was originally assigned to Preondactylus.

Later comparisons have made that identification less secure. MFSN 1891 does preserve pterosaur remains, but its fragmentation leaves few features that can reliably connect it to the holotype genus. It is evidence that a small flying reptile entered a food chain, if the regurgitation interpretation is right. It does not directly establish that Preondactylus was the swallowed animal.

The setting in the Tethys

The Dolomia di Forni formed in a marine environment along the margin of the tropical Tethys. A pterosaur could have fallen or been carried into the water from nearby land before burial on the sea floor. The deposit records where the carcass was preserved, not necessarily the animal's normal feeding grounds.

One main skeleton cannot establish population size, migration, seasonality or social behaviour. The soft outline of the tail, skin covering, colour and vocalisation are not preserved. An illustration can supply those details for a coherent scene, but the fossil account should distinguish them from the long tail, wing finger and other structures actually recorded.

Preondactylus is most useful as an early, incomplete record of an already capable flying pterosaur. It demonstrates that the specialised wing was present by the Norian while leaving the path by which that wing originated open to further fossils and analyses.