Long bones

Pterosaur long bones are essentially the wing and leg bones.  They cover the scapulo-coracoid, humerus, ulna and radius, wing metacarpal, metacarpals, phalanges, femur, tibio-tarsus and phalanges.

Most of the long bones are hollow, having a large pneumatic cavity and showing a pneumatic foramen where the air sac cavities pass into the bone.  The outer cortex of pterosaur bone is very thin and very dense, more so in the short tailed species.

     

The scapulo-coracoid is a very diagnostic bone in  pterosaurs.  It has a crescent shape, with the glenoid cavity, into which the humerus articulates, situated about mid-way around the bone.  The left bone is of a Rhamphorhynchus and the right is of Nyctosaurus.  Larger pterosaurs tend to have more massive scapulo-coracoids to accommodate the greater bone stress of flying.  The problem with these bones is being able to identify fragments of scapula or coracoid.

The wing bones of a typical Pterodactyloid pterosaur are seen here in this model of the wing of Ornithocheirus.  The wing metacarpal is long and has a very distinct distal (away from the body) end.  This long bone is characteristic of Pterodactyloid pterosaurs.

The wing metacarpal of Rhamphorhynchoid pterosaurs is significantly smaller and flatter in profile than that of Pterodactyloids.  Here can be seen a large and a small example from different species of Rhamphorhynchus.

Many of the wing bones show variation in features between different species, none more so than the Humerus.  The large articular crest is quite variable and develops in size towards the Cretaceous species.

     

On the left is a typical Rhamphorhynchus humerus, showing the crest and the curvature of the bone shaft.  On the right are a selection of pterosaur humeri, the more recent species being to the left and the more ancient to the right.

This bone is a femur.  The small angle of inflection of the head of the femur is is typical of most pterosaur species and the pneumatic foramen can be seen on the side of the bone.  This is an Ornithocheirid femur bone.

One of the main problems with pterosaur long bones is the state of preservation.  If the ends are found in isolation or they are missing, the bones can be difficult to identify.

     

The fossils on the left show the ends of pterosaur long bones.  These are Ulna fragments currently at Shrewsbury Museum Services.  The fossil on the right is from Morocco.  With the ends missing, it is difficult to know if this bone is from a pterosaur, a bird or a small theropod dinosaur.  I would suggest that the bone cortex is too thick for it to be a pterosaur bone, but if there is a pathological issue then I may be just that.

If there is any doubt about the classification of a fossil, it is always worth consulting an expert.

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