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.
BSt 1936 I 50 (no. 30 in the Wellnhofer 1970 catalog) nests with BSp 1968 XV 132 (Fig. 2).
AMNH 5147 nests between tiny MB.R.3530.1 (Fig. 4) and larger Gnathosaurus.
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 (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:
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.
Click to each taxon for additional references.