Manual digit 5 on Bellubrunnus (= basal Rhamphorhynchus)

In several phylogenetic predecessors of pterosaurs
such as Cosesauru, Sharovipteryx and Longisquama. manual digit 5 is small but clearly present (Fig. 1). Traditional workers report that manual digit 5 is absent in pterosaurs.

pterosaur wings

Figure 1. Click to enlarge. The origin of the pterosaur wing and whatever became of manual digit 5?

In pterosaurs
I have shown here, here and here several examples of a vestigial manual digit 5 on the axially rotated metacarpal 4. Unfortunately, other workers do not yet recognize these hard to see bones. Heck, they don’t recognize these taxa as pterosaur sister taxa, so we know the similar frustration John Ostrom and John Huxley felt when workers did not accept their bird/dinosaur hypothesis reviewed here.


Figure 2. Click to enlarge. The carpus and manus of Bellubrunnus identifying element including a vestige of manual digit 5. Yes, it’s tiny, but all vestiges are. Look closely, fellow workers, and you will find it for yourself. U = ulna. Ul = ulnare. R = radius. Ra = radiale. Pt = pteroid. PC = preaxial carpal. Numbers = unfused distal carpals and manual digits.

Hone et al. 2012
provided exquisite UV closeups of the tiny specimen, but did not identify vestigial manual digit 5. I do so here (Fig. 2). It’s clear, but tiny, as most vestiges are.

The carpal elements
are unfused because this adult specimen is the result of phylogenetic miniaturization. It’s ancestors among the genus Campylognathoides, were much larger individuals, as shown here. Essentially Bellubrunnus is a precocious adult, sexually mature in an otherwise immature, reduced size body. This can confuse those who work in bone histology and workers who don’t understand lepidosaur fusion patterns. Phylogenetic analysis, as shown here, solves these problems.

Hone DWE, Tischlinger H, Frey E and Röper M. 2012. A New Non-Pterodactyloid Pterosaur from the Late Jurassic of Southern Germany. PLoS ONE 7(7): e39312. doi:10.1371/journal.pone.0039312




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