Pterodactylus? micronyx? (undescribed) St/Ei I (JME 1) Late Jurassic ~160 mya ~2 cm skull length, was originally considered a juvenile Pterodactylus. Here it nests between dorygnathids and ctenochasmatids as a tiny tranisitional taxon. Once again, pterosaurs phylogenetically become precocious and tiny when they evolve to become something quite different. This specimen was about a tenth the size of Angustinaripterus, and that means it was smaller than a hatchling Angustinaripterus. St/Ei I phylogenetically preceded a specimen falsely attributed to Pterodactylus micronyx, MB.R.3530.1, 40 of Wellnhofer, 1970.
Distinct from Angustinaripterus, St/Ei I had a shorter rostrum with relatively smaller teeth. The cranium was larger. The mandible was more gracile.
Distinct from the R156 specimen of Dorygnathus, the cervicals were slightly shorter and the caudals were smaller without stiffening rods.
The sternal complex was not a triangle but a small shield shape. The humerus was much larger with an oversized deltopectoral crest that angled medially. The radius and ulna were much shorter and the metatacarpus relatively longer. The wing was no higher than the skull when folded.
The femur was strongly curled distally. The tibia was not longer than the femur.
Considering the size of the pelvic canal, the eggs of St/Ei I would have been no more than 4 mm in diameter and hatchlings would have been the size of flies. At that size desiccation becomes a problem due to high surface area and low volume. That threat might have prevented flight until a certain minimum size was reached and restricted movement to crawling about damp leaf litter.
The dorygnathid tree is here. The pterosaur family tree is here.
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