Figure 1. Tiny Pterodactylus? pulchellus (=micronyx) from the Natural History Museum London. Some DGS has been applied to bring out certain details. If your screen resolution is 72 dpi, then you’re seeing this fossil full size.
In the new book, Pterosaurs (Witton 2013:198), a tiny pterosaur with a 3 cm long skull with a long rostrum was pictured (Fig. 1). Witton identified the tiny pterosaur as a juvenile in the Natural History Museum London collection. After process of elimination, I’m guessing this is a Solnhofen (Late Jurassic) specimen PV R 2721 attributed by Meyer (1841) to Pterodactylus puchellus. [I could be wrong.] Later workers called it P. micronyx. I don’t know the Wellnhofer (1970) number.
Here it is at full scale (Fig. 1, if your screen is set to 72dpi). The inset shows the pes reconstructed. The pes alone with its long metatarsal 1 identifies it as a descendant of the scaphognathids (Peters 2011). Phylogenetic analysis nested it between another tiny pterosaur (but slightly larger) with a shorter rostrum, GMU-10157 (Fig. 2) and Cycnorhamphus (Fig. 3) a much larger specimen.
Notice the resemblance?
Figure 2. GMU-10157 (above) and (I think) the Meyer 1841 specimen PV R 2721 (below) to the same scale. The Meyer specimen is slightly smaller overall, yet has a longer rostrum and nests at the base of the Cycnorhamphus clade. GMU-10157 nests at the base of the cycnorhamphids + ornithocheirids.
The interesting thing…
The Meyer 1841 specimen is actually smaller than GMU-1-157, and yet it has a longer rostrum! That breaks one of the “rules” under the old allometric ontogenetic growth paradigm. Here these two tiny adults are part of a long gradual evolutionary continuum of size reduction and enlargement (Fig. 3). And this, ladies and gentlemen, is how you evolve a Cycnorhamphus. It’s the closest known outgroup taxon. Further out GMU-10157 nests at the base of the cycnorhamphids + ornithocheirids.
Figure 3. Cycnorhamphus, its sisters and predecessor taxa, sans the Meyer 1841 specimen.
Witton (2013) considered Cycnorhamphus a ctenochasmatoid, related to Pterodactylus and Ctenochasma. They’re not related according to the results of the large pterosaur family tree (where the Meyer specimen will shortly be added). You have to go back to Dorygnathus to find a last common ancestor. If you eliminate Ctenochasma then Scaphognathus is the last common ancestor. Obviously, given the generic name Meyer (1841) applied to this specimen, this sort of mistake has been going on for a long, long time.
Figure 4. Reconstruction of the tiny London specimen, shown larger than actual size. Derived from a sister to the GMU specimen (Fig. 2), the London specimen was ancestral to cycnhorhamphids. A great pes subdivided by PIL (parallel interphalangeal lines). You can even see the very beginnings of that dentary bend that reaches its acme in the bent-jaw cyc (Fig. 3). But no long legs yet.
The short neck problem
Darwinopterus was promoted as a transitional pterosaur, having the long rostrum and long neck of a pterodactyloid, but the remainder of the body with its long tail and long toe 5 were pre-pterodactyloid. The Meyer specimen, along with others, then presents a problem. It has a short neck and, for that matter, a shorter rostrum than Darwinopterus. GMU 1-157 has an even shorter rostrum. TM-13104 (Fig. 3) has an even shorter rostrum and longer metacarpals, yet it nests as a descendant of Scaphognathus.
Expectations and reality all fall apart rather quickly if you hang your hat on Darwinopterus, a specimen that is a “dead end” taxon in the large pterosaur family tree. Expand the gamut in your taxon list and see what new relationships emerge.
No such problems here.
If you don’t believe me that this is a tiny adult in the lineage of cycnorhamphids, just add it to your own analysis. Repeating the test is good Science. Throwing insults from the sidelines is not, unless they come with good evidence in tow. It is also possible that this specimen is young. Without an eggshell beside it, the tiny pterosaurs give few clues as to their ontogenetic age, other than their phylogenetic nestings and the sizes of their sisters. Here the sizes vary considerably.
Pterosaur workers have been avoiding tiny pterosaurs, denigrating them as pre-morph juveniles, when tiny pterosaurs hold the key to understanding pterosaur relations. Similarly pterosaur workers have been avoiding tritosaur/fenestrasaur/lepidosaurs, when they hold the key to pterosaur origins.
Take a good look at that skull
With that long concave rostrum, procumbent anterior teeth and pelvis shape in the Meyer specimen, we’re getting very close to the morphology of Cycnorhamphus. There’s no fronal/parietal crest yet. The long neck, long legs and longer metacarpals were yet to come. The free fingers were likewise getting close in proportion to one another.
If this is not the Meyer 1841 specimen, PV R 2721, please let me know to make the correction.
Witton M. 2013. Pterosaurs. Princeton University Press. 291 pages.