It’s always wonderful to see a new, complete pterosaur skeleton.
This one comes with a backstory that is making the rounds. Here we’ll talk about the specimen itself, GP/2E 9266 (Beccari et al. 2021; Early Cretaceous; Figs. 1-5), presently assigned to the name Tupandactylus navigans, a putatitve relative of Tupandactylus imperator.
The first strange thing about GP/2E 9266
is how much it resembles Tupandactylus (known from a partial skull only)… except for size (Fig. 1). The authors considered both to be adults. From the abstract: “The specimen can be assigned to Tupa. [= Tupandactylus] navigans due to its vertical supra-premaxillary bony process and short and rounded parietal crest.” Let’s stop assigning taxa based on a few traits. That’s “Pulling a Larry Martin“. Case in point: See the next paragraph.
The second strange thing about GP/2E 9266
is how it doesn’t nest with Tupandactylus in the Large Pterosaur Tree (LPT, 260 taxa). Instead it nests with a similarly-sized Chinese taxon, ZMNH M 8131 (Fig. 1), closer to the base of the Tapejaridae.
The third strange thing about GP/2E 9266
is that tall headcrest. It leans anteriorly, distinct from other, otherwise similar, crests. The authors found no posteriorly projecting process, but this is often broken off in fossils. There is an impression that matches the missing bone (Fig. 3). Speculative, but there it is, an impression.
The fourth and fifth strange things about GP/2E 9266
is it has one parasagittally expanded neural spine. The authors report that five vertebrae form a notarium, different than any other tapejarid… and the medial scapula is not modified to articulate with it. Likewise the ventral coracoid is not expanded, as in related taxa.
The sixth and seventh strange thing about GP/2E 9266
is the lack of a prepubis… and the extremely slender ventral process of the pubis, likely incapable of supporting a prepubis.
The eighth strange thing about GP/2E 9266
is the fusion of pedal phalanges 4.2 and 4.3 (Fig. 4). Beccari et al. also overlooked the fifth metatarsal and its two digits. The authors mistakenly wrote: “As in all later-diverging pterodactyloids, there are only four pedal digits.”
BTW, I’ve never seen distal tarsals on any tetrapod or pterosaurs like those shown in Beccari et al. (red elements in Fig. 4). Let’s leave those be for the time being.
The ninth strange thing about GP/2E 9266
is the authors flipped the wing finger upside-down with the leading edge trailing (Fig. 5). They also did not create horizontal stabilizers of the sprawling hind limbs (Fig. 6). Pterosaurs are such perfect natural inventions. Don’t leave the hind limbs dangling uselessly. Remember Sharovipteryx!
The tenth strange thing about GP/2E 9266
is the odd quadrupedal pose Beccari et al. put their reconstruction into (Fig. 7). Sure some pterosaurs walked around quadrupedally and left tracks. These were all beachcombers, seeking food in shallow waters. Tapedjarids are not members of those clades. Don’t generalize and make all pterosaurs awkward quadrupeds. Look at each one individually. Bipedal pterosaur ancestors were able to flap before they were pterosaurs. That was the initial attraction, together with crests.
The eleventh strange thing about GP/2E 9266
is the gracile pteroid. Really slender, more so than I’ve seen in pterosaurs.
The twelfth strange thng about GP/2E 9266
is the longer than typical phalanx 4.1, extending to the proximal ulna when the wing is folded (Fig. 7). Beccari et al. got things mixed up when they reported, “first wing phalanx length to metacarpal IV length in GP/ 2E 9266 = 0.58.”
The thirteenth strange thing about GP/2E 9266
is the tiny size of the foot.
Beccari et al. performed a phylogenetic analysis
(unfortunately, derived from previous studies). The authors reported, “The holotype of Tupa. navigans SMNK PAL 2344 was initially coded as a separate OUT, but no character differed from the scoring of GP/2E 9266. Therefore, the phylogenetic position of Tupa. navigans was accessed through the scoring of GP/2E 9266 using the character-taxon matrix of, composed by 64 taxa (including the new specimen) and 150 discrete characters.” This is why convergence can be so difficult to deal with. What can be scored of the two skulls are virtually identical. In the Beccari et al. analysis the Huaxiapterus corollatus specimen ZMNH M8131 (Fig. 1) nests in a polytomy with other Chinese pterosaurs separate from a sister polytomy of Brazilian pterosaurs. Since no one in Beccari et al. published comparable reconstructions or figures of related taxa (as in Fig. 1), other than some colorful silhouettes, we can assume they did as they said they did: borrowed data, never traced taxa, trusted scores and taxon lists.
Beccari et al. have outdated notions regarding pterosaur ontogeny
and bone fusion. They seek the fusion of elements as a ‘sign’ of maturity, as in the archosaurs and dinosaurs in their outdated cladogram. Adding taxa shows this notion is false. Fusion is entirely phylogenetic. When you look at enough taxa you learn that immature and late-stage embryo pterosaurs are identical to adults, except for an 8x difference in overall size, as in the lepidosaurs missing from the Beccari et al. cladogram.
The authors report, “The relatively longer forelimbs and the long cervical series may argue for a terrestrial foraging lifestyle.” “This could indicate that the aberrant crest may have restricted Tupa. navigans to short-distance flights, such as to flee from predators.” Sure the wing finger is skinny and phalanx 4.4 is short, but this taxon is far from flightless.
Beccari V, Pinheiro FL, Nunes I, Anelli LE, Mateus O and Costa FR 2021. Osteology of an exceptionally well-preserved tapejarid skeleton from Brazil: Revealing the anatomy of a curious pterodactyloid clade. PLoS ONE 16(8): e0254789. https://doi.org/10.1371/journal.pone.0254789