Scaphognathus sp. (Bennett 2004) the Maxberg specimen, no. 110 in the Wellnhofer 1975 catalog, Late Jurassic ~150 mya, was originally considered a juvenile of Scaphognathus crassirostris, no. 109 because it stood only as high as the hips of no. 109 and it appeared to have the expected juvenile proportions. Actually it was a very small adult, the second in a line of even smaller adults in a phylogenetic series (see below) that eventually produced Cycnorhamphus and Haopterus, No. 110 was derived from a sister to the SMNS 59395 specimen of Scaphognathus and phylogenetically preceded a specimen wrongly attributed to Pterodactylus, TM 13104 - n3 an even smaller adult pterosaur.
Distinct from SMNS 59395 the skull of the Maxberg specimen had a relatively shorter, blunter skull and larger orbit. The teeth were more robust. The postorbital process of the jugal was vertical. The premaxillary teeth are not so reduced. The quadratojugal process of the jugal is reduced to a nub. The mandible appears to shallow posteriorly.
The cervicals were shorter, half the torso length. The tail was shorter and more gracile. Extended hemal arches and zygopophyses are present, but extremely gracile.
The sternal complex was more circular. The humerus was greatly reduced. The ulna and radius were shorter. Manual digits II and III were subequal. The wing was slightly shorter.
The ischium was broader, higher and smaller. The small foot was just longer than half the tibia. Metatarsal I was longer than mt II. Pedal 5.1 extended nearly to the ungual of digit IV.
See the pterosaur family tree here.
We know that no. 110 was not a juvenile because pterosaur embryos (see Pterodaustro, IVPP embryo, JZMP embryo) demonstrate that pterosaurs matured isometrically, not allometrically, like crocs, birds and mammals. Hatchling pterosaurs did not have a short rostrum and large eyes, but were 8x times smaller versions of their parents. Plus, in a phylogenetic analysis, the evolutionary reduction and enlargement of tiny pterosaurs is apparent (see below) and no 8x larger adults have ever been found that would nest with any of these tiny transitional taxa. That means, of course, that hatchlings of these tiny adults would have been 8x smaller, approximately 1 cm in standing height, in the range of the smallest known living reptiles (Hedges and Thomas 2001). The threat of desiccation probably preventing such tiny hatchlings from flying. |
