Tiny pterosaurs – breaking the short rostrum false paradigm

With the false paradigm still in force among professional paleontologists that juvenile pterosaurs all have a short rostrum and a large orbit (Witton 2013 and references therein, like birds and crocs and mammals), it’s worthwhile to take a look at several tiny pterosaurs, each with a long rostrum. Each has been nested phylogenetically in the large pterosaur tree, the only effort, so far, to nest the tiny ignored ones. 

Here are nine tiny taxa, each with a fairly long – to extremely long – rostrum
Seven are found without an eggshell present (Figs. 1-7). Whether these are hatchlings, juveniles or adults cannot be determined except by their phylogenetic nesting. If sister taxa are large, then it’s more likely that these are juveniles. However, 1-7 are all surrounded by or nest next to tiny taxa. They also all nest after a series of larger taxa and prior to another series of larger taxa that all establish new clades. This is how pterosaurs evolved new clades.

Two others are embryos surrounded by eggshells (Figs. 8-9). Both of these are phylogenetically surrounded by large taxa.

Figure 1. I didn't realize the teeth were so long in ?Pterodactylus spectabilis, TM10341, n1 in the Wellnhofer 1970 catalog. This is no Pterodactylus, but a tiny dorygnathid. Click to learn more.

Figure 1. ?Pterodactylus spectabilis, TM10341, n1 in the Wellnhofer 1970 catalog. This is no Pterodactylus, but a tiny dorygnathid. Click to learn more.

TM 10341 nests between a much larger Dorygnathus (SMNS 50164) and slightly larger Rhamphodactylus BSPG 2011 I 133.

Figure 2. BSp 1968 XV 132

Figure 2. BSp 1968 XV 132 nests with Cycnorhamphids and tiny scaphognathids. Click to learn more.

BSp 1968 XV 132 nests between the smaller GMU 10157 and the equally small, BSt 1936-I-50 no. 30 (Fig. 3), close to cycnorhamphids.

B-St-1936-I-50-no30

Figure 3. B-St-1936-I-50 no. 30. Click to learn more.

BSt 1936 I 50 (no. 30 in the Wellnhofer 1970 catalog) nests with BSp 1968 XV 132 (Fig. 2).

MB.R.3530.1-(No.40)

Figure 4. MB.R.3530.1-(No.40) basal to ctenochasmatids

MB.R.3530.1 (No.40) nests between the equally tiny St/Ei I (derived from the larger Angustinaripterus) and ?Ctenochasma elegans (AMNH 5147, Fig. 5).

AMNH 5147

Figure 5. AMNH 5147, basal to ctenochasmatids

AMNH 5147 nests between tiny MB.R.3530.1 (Fig. 4) and larger Gnathosaurus.

Pterodactylus? elegans? BSPG 1911 I 31 (no. 42 in the Wellnhofer 1970 catalog)

Figure 6. Pterodactylus? elegans? BSPG 1911 I 31 (no. 42 in the Wellnhofer 1970 catalog). Click to learn more. Basal to azhdarchids, distantly derived from no. 1 (Fig 1.)

BSPG 1911 I 31 (no. 42 in the Wellnhofer 1970 catalog) nests between CM 11426 (no. 44 in the Wellnhofer 1970 catalog) and Sos 2428, the flightless pterosaur on one branch and the pro to-azhdarchid, Jidapterus, on the other branch.

Senckenberg-Museum Frankfurt a. M. No. 4072

Figure 7. Senckenberg-Museum Frankfurt a. M. No. 4072. Click to learn more.

Senckenberg-Museum Frankfurt a. M. No. 4072 (no. 12 in the Wellnhofer 1970 catalog) nests between the smallest pterosaur, B St 1967 I 276 (No. 6 of Wellnhofer 1970) and a larger specimen, B St ASXIX 3 (plate) SMF No. R 404 (counterplate), No. 23 of Wellnhofer 1970). No. 6 had a smaller snout and larger rostrum because it was more closely related to tiny Ornithocephalus and the larger Scaphognathus (no. 110), and the even larger Scaphognathus (no. 109). See all of these in one image here.

And now, the embryos:

JZMP-03-03-2

Figure 8. JZMP-03-03-2 embryo shown with hypothetical 8x larger adult and sister taxa scaled to the adult. Click to learn more and see detailed imagery of the embryo in the eggshell.

Misinterpreted as a Beipiaopterus, the embryo JZMP-03-03-2 nests between the basal ornithocheirids, Yixianopterus and Haopterus (Fig. 8). An adult of the embryo would be twice the size of Haopterus 

Pterodaustro embryo

Figure 9. Pterodaustro embryo. There certainly is no short snout/large eye here! However there are several differences between this specimen and the adult. Click to learn more.

The Pterodaustro embryo nests with its parent, Pterodaustro and this lineage disappears after this taxon. There are slight differences between the embryo and adult Pterodaustro. There are differences between adult Pterodaustro, detailed here.

Certainly there are embryos and tiny pterosaurs with a short rostrum and large orbit (like the IVPP embryo which is the size of other adult anurognathids!). All sister taxa likewise have a short rostrum and large orbit and other similar traits detailed here.

Earlier we looked at a hypothetical Quetzalcoatlus sp. embryo tucked into a long shell to accommodate that long rostrum. Pterodaustro likewise produced an elongated egg to accommodate that hyperelongated rostrum.

References
Click to each taxon for additional references.

2 thoughts on “Tiny pterosaurs – breaking the short rostrum false paradigm

  1. Each has been nested phylogenetically in the large pterosaur tree, the only effort, so far, to nest the tiny ignored ones.

    Several people have been trying to explain to you for years that this doesn’t mean shit. A phylogenetic analysis is not capable of telling you if an individual is an adult, a juvenile of another OTU in the matrix, a juvenile of a species that is not in the matrix, or any such thing.

    Phylogenetic analysis starts from the assumption that the OTUs are comparable.

    It is a well-known empirical fact that, in all sorts of animals (not just vertebrates), juveniles look alike, and autapomorphies of their clades only develop with age. In my work I run into this fact again and again and again. If you take the absence of such character states in immature individuals at face value, you’ll inevitably get a tree that will show a wild mixture of ontogeny and phylogeny.

    If you can’t be bothered to find the literature on this, perhaps try it on your own with extant taxa?

  2. Reality trumps analogy in this case. The embryos are verifiable in age and they are virtual copies of adults. Moreover, you’re forgetting that certain tiny pterosaurs, like basal Rhamphorhynchus, nest closer to larger ancestors among Campylognathoides than to derived Rhamphorhynchus. And the large reptile tree nests many other such instances.

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