here and here we looked at pregnant pterosaurs. As you may recall, as lepidosaurs pterosaurs could retain their young in utero much longer than archosaurs do. Archosaur embryos are microscopic when laid and they develop in the egg outside of the uterus. Some extant lepidosaurs retain their young in utero to the stage of viviparity. Others lay eggs at an advanced stage. Today, two more tiny pterosaurs are shown to be adult females, based on the embryo inside of each of them.
As long-time readers know,
phylogenetic analysis of the Pterosauria that includes the tiniest hummingbird-sized individuals from the Solnhofen formation nest them all as adults. They have been phylogenetically miniaturized and generally they nest at the bases of major clades. Generally the smallest pterosaurs are transitional from larger taxa and to larger taxa, but they are also often surrounded by other tiny transitional pterosaurs. That’s how we arrive at pterodactyloid-grade pterosaurs at least 4x. By convergence anurognathids and wukongopterids also added some, but not all, pterodactyloid traits.
who refuse to test the tiny ones, mistakenly assert that the tiny ones are babies. If that were true then, as the other workers suggest, pterosaurs would have to develop isometrically, changing shape with maturity. Several examples of embryo and juvenile pterosaurs demonstrate irrevocably that that is not true. Juveniles and embryos are carbon copies of the adults.
The smallest adult pterosaur is
Pterodactylus? kochi? B St 1967 I 276 (No. 6 of Wellnhofer 1970, (Figs. 1,2).
I did not realize
how large the sternal complex was on this pterosaur, Such a large pectoral anchor suggests the wings were flapped strongly or rapidly or both, possibly as in similarly-sized hummingbirds. The coracoids are also larger than earlier reconstructed.
Nesting with the smallest known pterosaur
in the large pterosaur cladogram, is another tiny Solnhofen specimen, BMNH 42736, which also has a large sternal complex and is, by coincidence, pregnant.
All I really wanted to do
was gather the data on this pterosaur to see where mistakes had been made. Finding tiny extra bones in the base of the abdomen was a surprise. These two, despite their differences, nest together in the large pterosaur tree.
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Wellnhofer P 1970. Die Pterodactyloidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Abhandlungen der Bayerischen Akademie der Wissenschaften, N.F., Munich 141: 1-133.