Scottish Dearc is another Dorygnathus, and it’s not the largest Jurassic pterosaur

Dearc sgiathanach
(Jagielska et al. 2022, NMS G.2021.6 Middle Jurassic, Figs 1, 2) was originally considered the largest Jurassic rhamphorhynchine pterosaur. It is not. Late Jurassic Sericipterus (Fig 1) was larger.

Figure 1. Dearc shown to scale with the larger Jurassic pterosaur, Sericipterus.

With taxon exclusion
and their borrowed low-resolution, 30-pterosaur phylogenetic analysis, the eleven authors estimated the upper range of wingspan of gracile-winged Dearc (Fig 1) from unrelated long-winged Rhamphorhynchus.

Jagielska et al wrote,
“Its most remarkable attribute is its size: its wingspan was ca. 1.9–3.8 m, roughly the size of the largest flying birds today.”

1.9mx 2 = 3.8m. That is a rough estimate with a 100% range. Based on published scale bars and comparisons to related Dorygnathus taxa (Fig 2), Dearc had an est 1.5m wingspan.

Jagielska et al also wrote,
“Dearc is the first Jurassic pterosaur whose wingspan can confidently be estimated at ca. 2.5 m or greater, based on a well-preserved, articulated skeleton.5 Its closest relatives, Angustinaripterus and Sericipterus, are also sizeable for Jurassic species, with wingspans previously estimated at 1.61–1.738 m extrapolated from patchy fossils.”

The authors, referees and editors should have caught this internal discrepancy, especially so since wingspan is the core of their headline grab. Angustinaripterus is known from a skull only. Sericipterus is larger in every regard.

Jagielska et al also wrote,
“To estimate wingspan, we compiled measurements of complete wingspans of two non-monofenestratans represented by large sample sizes—Rhamphorhynchus and Dorygnathus—and regressed these against the lengths of individual bones to create predictor formulas. These results demonstrate that Dearc is the largest Jurassic pterosaur yet known, consistent with the fact that its humerus and skull are the longest of any Jurassic specimens.”

Perhaps documenting this claim with to-scale graphics (Fig. 1) would have helped. The first wing phalanx of Rhamphorhynchus extends back to the elbow when folded. By contrast, in Dorygnathus the first wing phalanx typically does not extend back to the half point of the ulna.

Figure 2. Click to enlarge. Dearc (bottom row, second from left) nests in the middle of several Dorygnathus specimens in the LPT. The variety in morphology in this clade is typical for pterosaur clades.

Dearc was also considered a new genus.
Here in the large pterosaur tree (LPT, 262 taxa) Dearc (Fig 3) nests in the middle of several Dorygnathus specimens. So Dearc is not a new genus, at least not until someone volunteers to split up Dorygnathus. Older workers tend to lump. Younger workers tend to split.

Taxon exclusion
remains the number one problem in paleontology. We can’t test just one Dorygnathus. No two are alike (Fig 2).

We also can’t borrow long wings from unrelated taxa
in order to produce a superlative-laden headline.

We also need to stop borrowing cladograms.
Jagielska et al. reported they borrowed data from eleven other cladograms, not all of them original studies. Apparently none of the borrowed cladograms included a wide gamut of Dorygnathus specimens.

Jagielska et al. reported,
“The Middle Jurassic age of Dearc adds to increasing evidence that this interval—once a frustrating gap in the pterosaur record—was in fact a dynamic time of diversification, in which a variety of basal taxa and early monofenestratan lineages.”

The Middle Jurassic has never been a frustrating gap for pterosaurs.
A wide variety of Dorygnathus (Fig. 2) taxa filled the Middle Jurassic of Europe. Omitting them gave Jagielska et al. perimission to borrow cladograms and wingspans.

Dearc is the same pterosaur discussed a few days ago when the authors announced their paper had been accepted for publication and it was supposed to be embargoed until January 2023, according to information available at the Cell Press website. I guess the editors changed their mind or there was an editorial mistake.

Figure 3. ‘Dimorphodon’ weintraubi was another large pterosaur from the Middle Jurassic.

‘Dimorphodon’ weintraubi (Fig 3) was another large Middle Jurassic pterosaur.

Figure 4. Here the CZ specimen of Campylognathoides is shown to scale with Dearc.

The Early Jurassic CZ specimen of Campylognathoides (Fig 4) was almost as tall as Dearc with a wider wingspan and more robust wing fingers.

Figure 5. Dearc compared to the two largest specimens of Rhamphorhynchus, which have longer and more robust wing phalanges and a more robust torso with larger sternal complex.

The authors compared Dearc (est 1.5m wingspan) to the largest Rhamphorhynchus (est 1.7m wingspan and slightly taller and more robust, Fig 5). The authors came up with some estimates for wingspan (see above), but published no side-by-side comparative graphics (Figs 1–5), which is traditional fare in superlative stories like this one.

We have to raise our standards
Referee David Hone wrote, “It’s clearly a non-monofenestratan pterosaur and actually one that is very close to Rhamphorhynchus, enough in fact to be found to be a member of the Rhamphorhynchinae in the phylogenetic analysis that they did.”

Dearc is not very close to Rhamphorhynchus (Fig 5).

Was Hone chosen to be a referee for his expertise in pterosaurs?
Few other workers have been responsible for so much misidentification and bungling of pterosaur anatomy and phylogeny. You’ll note that Hone did not have his own wide gamut phylogenetic analysis comparable to the LPT, but gladly accepted the Jagielska et al. 2022 analysis at face value. He also accepted all the bungles listed above. This is the state of pterosaur paleontology today. That’s why we get papers riddled with omissions.

Jagielska N et al. (ten co-authors) 2022. A skeleton from the Middle Jurassic of Scotland illuminates an earlier origin of lage pterosaurs. Current Biology 32:1–8.


BBC YouTube video:

Lovely fossil suffering only from hyperbole.

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