Summary for those in a hurry:
Your pterosaur traditions are going to be upset once again as this small adult pterodactylid with a long tail and a long, bent pedal digit 5 nests apart from the wukongopterid, Kunpengopterus, whenever more taxa are added to compete for its attraction.
Jiang et al. 2021 had the right idea, but did not see it through.
They wrote: “It is worth noting that Jianchangopterus zhaoianus, first published as a rhamphorhynchid pterosaur, may represent a young wukongopterid (Witton 2013, Wu et al. 2017). The only specimen of Jianchangopterus should have been housed at Yizhou Museum (Lü & Bo 2011), but none of the staff knew the whereabouts of this specimen when two of our authors (JS & CX) checked in the museum in 2019. Without observation of the holotype, especially the confluent condition of the nasoantorbital fenestra, it is impossible to confirm whether Jianchangopterus is a wukongopterid. Here, we described the first small-sized wukongopterid pterosaur to show some skeletal changes during ontogeny and revised the diagnosis of Kunpengopterus sinensis.”
There is no phylogenetic analysis in Jiang et al.
Evidently they didn’t feel the need to do so. After analysis in the large pterosaur tree (258 taxa, 183 characters) the ‘Kunpengopterus juvenile’ (STM 19-59) nests between the pterodactylids, Douzhanopterus (not mentioned in the Jiang et al. text) and Jianchangopterus (see paragraph above). These are basal pterodactylids close to the Painten pterosaur (privately owned and cited in Jiang et al.). Contra Jiang et al., it is not “impossible to confirm whether Jianchangopterus is a wukongopterid.” It is not a wukongopterid in the LPT and never was. 23 additional steps are needed to move STM 19-59 to Kunpengopterus.
Don’t freak out
over the long tail and bent pedal digit 5 in the pterodactylid, STM 19-59. Some traditions have exceptions and reversals when tested. These are things you learn by testing, not out of current textbooks, videos and lectures. So, put away your favorite traditions and test this for yourself.
From the Jiang et al. 2021 abstract:
“The Wukongopteridae is a transitional clade between the long- and short-tailed pterosaur groups, and at least ten specimens have been studied without a determined juvenile specimen.“
Actually, after testing in the LPT, Wukongopteridae is a clade without descendants in the Cretaceous. Pterosaur workers, all PhDs with reputation to lose if found to be wrong, have been cherry-picking and omitting taxa, including outgroup taxa, to perpetuate the myths they have been teaching at their universities and museums. No one has been brave enough to match the 250+ taxon list in the LPT, now ten years old, first discussed in front of a gathering of PhDs and chronicled in Peters 2007.
“Here, we described a small-sized Kunpengopterus sinensis, less than half the size of the holotype, which is the smallest specimen in wukongopterids. Based on unossified small elements, unfused cranial and postcranial elements, and grooves on the bone surface, this specimen is thought to be at least an early juvenile or even a late hatchling.”
If so, STM 19-59 should nest with an adult Kunpengopterus, since pterosaurs matured isometrically, like other lepidosaurs (Maisano 2002a, b), not like archosaurs. In the LPT STM 19-59 nests within an expanded Pterodactylidae. Clade members have a long tail and and elongated pedal digit 5. In paleontology we call this a reversal.
“By comparing the juvenile and subadult specimens of K. sinensis, we have found that the mid region of the upper and lower jaws had a higher growth rate than the anterior part, and that the growth rates were similar in most postcranial elements except for a higher rate in the caudal vertebrae.”
That does not sound like isometry. So this observation by Jiang et al. should be a red flag. This is where phylogenetic analysis comes in handy. Don’t assume. Test. You might be surprised by the results. Juveniles nest with adult pterosaurs in analysis.
The Jiang et al. 2021 abstract concludes:
“We revised the previous diagnosis of K. sinensis and specified that two characteristics, nasoantorbital fenestra approximately 40% of the skull length and a thin and relatively short maxillary process of the jugal, should be diagnostic in subadult or adult specimens. We have also found that pedal features are stable during ontogeny and can be diagnostic in juvenile, subadult or adult specimens in K. sinensis.”
So now new myths and false traditions enter the world of pterosaurs.
Stable is the word you want to hear as it indicates isometry, but the authors actually found convergence.
Without a valid phylogenetic context, don’t even attempt to try to understand ontogenetic patterns. In this case the authors were attempting to force the adoption of an adult Jinchangopterus on unsuspecting Kunpengopterus parents.
Yes, the STM 19-59 specimen
has a long tail and a long, bent pedal digit 5. These are traditional rhamphorhynchoid (= pre-pterodactyloid-grade traits). Workers make the mistake of drawing a line in the systematic sand because these traits have been traditions for centuries. Test all traditions. Some of them have exceptions and reversals you may not be aware of. Don’t end up ‘Pulling a Larry Martin‘. Don’t base your decisions on a few traits, even a few famous traits. Several pterodactyloid pterosaurs have a surprisingly long tail. And that’s okay! Test the entire taxon against a wide gamut of competing candidates. Then your cladogram will model actual evolutionary events, including reversals without adding to the mythology that PhDs have been putting on your favorite pterosaurs.
An email from lead author S Jiang suggested running the analysis without Jianchangopterus. So let’s do that (and more) to see how many taxa must be deleted to move the STM 19-59 specimen to the wukongopteridae.
Deletion of Jianchangopterus: no topology change
Plus deletion of Douzhanopterus: no topology change
Plus deletion of the Painten private specimen: shift to Wukongopteridae, but not with Kunpengopterus.
Deletion of only the Painten private specimen: no topology change
Remember, skull shape does not lengthen with maturity, as all other juvenile/adult pairings in pterosaurs demonstrate (contra Jiang et al. 2021).
Jiang S et al. 2021. An early juvenile of Kunpengopterus sinensis (Pterosauria) from the Late Jurassic in China. An. Acad. Bras. Ciênc. [online]. 2021, vol.93, suppl.2, e20200734. Epub Apr 19, 2021. ISSN 1678-2690. https://doi.org/10.1590/0001-3765202120200734.
Maisano JA 2002a. The potential utility of postnatal skeletal developmental patterns in squamate phylogenetics. Journal of Vertebrate Paleontology 22:82A.
Maisano JA 2002b.Terminal fusions of skeletal elements as indicators of maturity in squamates. Journal of Vertebrae Paleontology 22: 268–275.
Peters D 2007. The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.
wiki/Pterodactyloidea – this is the traditional, untested view