In the earlier overview of the family tree of the Pterosauria, we looked at the basal split between the Dimorphodontia and the Eudimorphodontia. Within the latter, we just touched on the overlooked variety in Dorygnathus, which directly gave rise to two clades of “pterodactyloid”-grade clades: the azhdarchids and ctenochasmatids.
The Scaphognathia
A sister to Sordes and the Donau specimen of Dorygnathus branched off in a direction that would ultimately produce some small, unspectacular pterosaurs, some of the tiniest of all pterosaurs and two clades of the most spectacular crested pterosaurs. This is the Scaphognathia, named for the small, plain, unspectacular Scaphognathus. Pterorhynchus was at the base of the Scaphognathia.
Figure 2. Sordes, Pterorhynchus, Scaphognathus, Kunpengopterus and Darwinopterus.
Pterorhynchus – the Oddball
Pterorhynchus was like a big Dorygnathus with small teeth, a larger sternal complex and a much longer tail. Even though it nested between Sordes and Scaphognathus, Pterorhynchus had several derived traits not seen in either sister. The naris, for instance was reduced to a slit. Rather than having a single vane at the tip of its tail, Pterorhynchus had a series of vanes running down the length of its tail. Scaphognathus was more conservative, more like Sordes in overall morphology.
This is Where Darwinopterus Nests
Earlier analyses of mine nested the purported transitional taxon, Darwinopterus (Lü et al. 2009), with Elanodactylus between several Germanodactylus specimens, but new data from Pterorhynchus and other pterosaurs changed things. Now Kunpengopterus (Wang et al. 2010) nests as a sister to Pterorhynchus at the base of the Darwinopterus/ Wukongopterus clade. The disappearance of the naris in Darwinopteruswas well underway in Pterorhynchus, which reduced the naris to a mere slit. The elongation of the skull (or rather the reduction of the orbit) also begins with Pterorhynchus. Kunpengopterus did not have a larger skull, only a longer neck. Darwinopterus had a larger skull.
Scaphognathus – The Three Specimens
The holotype Scaphognathus (Goldfuss 1830) GPIB 1304 (No. 109 of Wellnhofer 1975) gave rise to two smaller forms, both considered juveniles of Scaphognathus, even though they were morphologically distinct from the holotype and from each other.
Figure 3. Click to enlarge. The base of the Scaphognathia illustrating the size reduction that preceded the size increase in the transition from Scaphognathus to several later, larger "pterodactyloid"-grade clades.
The First Transition to the “Pterodactyloid” Grade
The smaller SMNS 59395 specimen of Scaphognathus was considered a juvenile by Bennett (2004) but it was morphologically distinct and a transitional taxon leading to the even smaller Ornithocephlaus BSPG 1971 I 17 (Soemmerring 1812-1817) Pterodactylus micronyx von Meyer 1856, No. 29 in the Wellnhofer (1970) catalog). Ornithocephalus was historically and mistakenly considered to be a “juvenile Pterodactylus,” but it was instead a close relative and a precursor taxon. If it was indeed a juvenile Pterodactylus, it would have looked more like the adult.
Preceding Germanodactylus
A series of smaller taxa, including Wellnhofer’s (1970) No. 9 and No. 6 (the smallest pterosaur known), led to a series of increasingly larger taxa, including Wellnhofer’s No. 12, No. 23 and No. 64 Germanodactylus.
Preceding Pterodactylus
Another series of tiny taxa, including Wellnhofer’s (1970) No. 9, No. 31 and Ninchengopterus led to No. 20 the most primitive Pterodactylus.
The Second Transition to the “Pterodactyloid” Grade
The other smaller Scaphognathus, the Maxberg specimen (no. 110 in the Wellnhofer 1975 catalog) phylogenetically preceded another series of tiny pterodactyloid-grade pterosaurs, including TM 13104, Gmu 10157 and Yixianopterus.
Preceding Ornithocheirids
Yixianopterus was a sister to the taxon that preceded ornithocheirids, like Haopterus, perhaps without a size shrinkage between them.
Preceding Cycnorhamphids
Yixianopterus was also a sister to the taxon that preceded cycnorhamphids via a size squeeze, with tiny BSp 1968 XV 132 and No. 30 phylogenetically preceding Cycnorhamphus and Feilongus.
No Single Transitional Taxon
Clearly there was no single “missing link,” and it was not Darwinopterus. Rather, four lineages all leading from Scaphognathus and two others leading from Dorygnathus provided all of the pterodactyloid-grade pterosaurs now known. These sequences also falsify Hone and Benton (2006) which claimed to support Cope’s Rule in the Pterosauria, but only after deleting the tiny pterosaurs.
Figure 4. Click to enlarge. The pterosaur family tree. The Scaphognathia are located at the top of the second (right) column.
As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.
Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.
References:
Bennett SC 2004. New information on the pterosaur Scaphognathus crassirostris and the pterosaurian cervical series. Journal of Vertebrate Paleontology, 24: 38A
Goldfuss GA 1830. Pterodactylus crassirostris. Isis von Oken, Jena pp. 552–553.
Hone and Benton 2006. Cope’s Rule in the Pterosauria, and differing perceptions of Cope’s Rule at different taxonomic levels. Journal of Evolutionary Biology 20(3): 1164–1170. doi: 10.1111/j.1420-9101.2006.01284.x
Lü J, Ji S, Yuan C, Gao Y, Sun Z and Ji Q 2006. New pterodactyloid pterosaur from the Lower Cretaceous Yixian Formation of Western Liaoning. In J. Lü, Y. Kobayashi, D. Huang, Y.-N. Lee (eds.), Papers from the 2005 Heyuan International Dinosaur Symposium. Geological Publishing House, Beijing 195-203.
Lü J, Unwin DM, Jin X, Liu Y and Ji Q 2009. Evidence for modular evolution in a long-tailed pterosaur with a pterodactyloid skull. Proceedings of the Royal Society London B (DOI 10.1098/rspb.2009.1603.)
von Soemmering ST 1812. Über einen Ornithocephalus. – Denkschriften der Akademie der Wissenschaften München, Mathematischen-physikalischen Classe 3: 89-158.
von Soemmering ST 1817. Über einer Ornithocephalus brevirostris der Vorwelt. Denkschriften der Akademie der Wissenschaften München, Mathematischen-physikalischen Classe 6: 89-104.
Wagner JA 1851. Beschreibung einer neuen Art von Ornithocephalus nebst kritischer Vergleichung der in derk. Paläontologischen Sammlung zu München aufgestellten Arten aus dieser Gattung. Akademie der Wissenschaften Mathematischen-physikalischen Klasse6: 127–192 & pls 5–6.
Wang X, Kellner AWA, Jiang S-X, Cheng X, Meng Xi & Rodrigues T 2010. New long-tailed pterosaurs (Wukongopteridae) from western Liaoning, China. Anais da Academia Brasileira de Ciências 82 (4): 1045–1062.
Wellnhofer P 1970. Die Pterodactyloidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Abhandlungen der Bayerischen Akademie der Wissenschaften, N.F., Munich 141: 1-133.
Wellnhofer P 1975a. Teil I. Die Rhamphorhynchoidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Allgemeine Skelettmorphologie. Paleontographica A 148: 1-33.1975b. Teil II. Systematische Beschreibung. Paleontographica A 148: 132-186. 1975c. Teil III. Paläokolgie und Stammesgeschichte. Palaeontographica 149: 1-30.
Winkler TC 1870. Description d’un nouvel exemplaire de Pterodactylus micronyx du musee Teyler. Archives des Musee Teyler 3: 84-99.
The Pterosaur Heresies 