Junior synonyms for Gnathosaurus: several mistakes noted – pt2
Part 1 of this report
was presented earlier here based only on the abstract. Now the PDF is at hand.
Bennett 2025 linked several small to tiny Solnhofen pterosaurs
to Gnathosaurus (Fig 1), the otherwise rare spoon-billed ctenochasmatid with a 28cm long skull. In the large pterosaur tree (LPT, 236 taxa) two taxa omitted by Bennett nest with Gnathosaurus, Liaodactylus (from China, Fig 1) and the small, but not juvenile AMNH 5147 specimen, also from the Solnhofen (Fig 2). This was likely a phylogenetic precursor to Gnathosaurus, smaller of size and shorter to skull proportions. Pterosaur juveniles had the same proportions as adults = isometry, because they were fenestrasaurian lepidosaurs.
Details from the text follow.
Figure 1. Liaodactylus (in color in in situ compared to Gnathosaurus.
” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2017/02/liaodactylus-primus-588.jpg?w=183″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2017/02/liaodactylus-primus-588.jpg?w=584″ class=”size-full wp-image-26091″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2017/02/liaodactylus-primus-588.jpg” alt=”Figure 1. Liaodactylus (in color in in situ compared to Gnathosaurus.” width=”584″ height=”955″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2017/02/liaodactylus-primus-588.jpg?w=584&h=955 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2017/02/liaodactylus-primus-588.jpg?w=92&h=150 92w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2017/02/liaodactylus-primus-588.jpg?w=183&h=300 183w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2017/02/liaodactylus-primus-588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 1. Liaodactylus (in color in in situ compared to Gnathosaurus.
Bennett 2025 reported on the history of each small specimen.
“v. Meyer (1856) had briefly described a small headless pterosaur specimen from the Solnhofen Lithographic Limestones, characterized it as having small claws and the wing metacarpal and antebrachium of the same length, and named it Pterodactylus micronyx. v. Meyer (1859–1860) described it and a second headless specimen referred to P. micronyx thoroughly, and later a third, larger specimen with a skull was described as having pfriemenförmige teeth and referred to P. micronyx (v. Meyer 1862).”
While the history is interesting, no specimen numbers were given here, leaving the interested reader in the dark. Unfortunately this continues throughout the introduction. With so many obscure and sometimes headless pterosaur specimens, museum numbers are essential. Don’t forget to include them.
Specimen numbers do come later in the Bennett 2025 text.
Figure 6. AMNH5147
” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2013/06/amnh5147.jpg?w=300″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2013/06/amnh5147.jpg?w=584″ class=”size-full wp-image-11503″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2013/06/amnh5147.jpg” alt=”AMNH5147″ width=”584″ height=”530″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2013/06/amnh5147.jpg?w=584&h=530 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2013/06/amnh5147.jpg?w=150&h=136 150w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2013/06/amnh5147.jpg?w=300&h=272 300w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2013/06/amnh5147.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 2. AMNH 5147. Thought tiny, the short skull nests this specimen basal to Gnathosaurus as a phylogeentically miniaturized adult. This is how pterosaurs diversified.
Bennett reported on the history of Gnathosaurus itself,
“Mook (1934) placed Gnathosaurus in the Teleosauridae, Romer (1956) listed it as ?Gnathosaurus in both the Teleosauridae and Pterosauria incertae sedis. The confusion was finally dispelled when Wellnhofer (1970) described an excellently preserved skull from the Lithographic Limestones at Eichstätt, Germany, referred it to G. subulatus, and placed Gnathosaurus in the Ctenochasmatidae.”
Bennett is excellent as a historian, if that’s your thing.
Imagine, back in the day they thought this pterosaur could be a sea-croc.
Bennett reported,
“Bennett (1996b) interpreted the small specimens referred to the four Pterodactylus species as juveniles of large species, most of which were in different genera, and, based primarily on skull and tooth morphology, it was suggested that specimens of P. antiquus, P. kochi, and P. longicollum were conspecific, specimens of P. elegans were juveniles of Ctenochasma gracile, and specimens of P. micronyx were juveniles of Gnathosaurus subulatus.”
After phylogenetic analysis
(see the LPT tree and Peters 2007), this is incorrect. Bennett was not aware of (or chose to ignore) phylogenetic miniaturization at the genesis of pterosaur clades. Instead he assessed specimens on size and superficial aspects rather than testing specimens by trait analysis. Bennett prefers to continue to consider pterosaurs as archosaurs, as do all academics. Archosaurs change shape during ontogeny = allometry. Pterosaurs don’t.
Here’s another example of Bennett’s erroneous assessment method:
“Based on the presence of edentulous jaw tips and skeletal proportions, Bennett (2006) reinterpreted two small specimens previously considered to be P. kochi and P. micronyx, respectively, as juveniles of Germanodactylus cristatus.”
These two taxa were small adults in analysis. They nested with other small taxa, rather than with large but identical adults. Bennett 2025 does not include a phylogenetic analysis, so he is ‘eyeballing’ these taxa without examining details and without understanding ontogenetic strategies in these lepidosaurs (Peters 2007).
This lack of curiosity = keeping the blinders on is inappropriate for a scientist – but unfortunately typical, traditional and acceptable in the pterosaur expert community.
Bennett observed,
“Indeed, specimens of P. micronyx with skull lengths 50 mm exhibit skull and tooth morphologies are significantly different from the smaller juveniles.”
In pterosaurs changes are due to phylogeny, rather than ontogeny, but Bennett failed to test thes differences he noted in analysis.
Getting to the core of the present observations, Bennett reported,
“The holotype mandible and the referred skull of Gnathosaurus subulatus and the four largest specimens referred to Pterodactylus micronyx by Wellnhofer (1970) are described below.”
At this point in the Bennett text specimen numbers were provided.
Figure 3. The MBR 3655 specimen of Pterodactylus compared to scale with the much smaller PMU 24792 specimen. Note the identical proportions in the skull.
” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/03/mbr3655_pmu24792-588-3.gif?w=129″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/03/mbr3655_pmu24792-588-3.gif?w=440″ class=”size-full wp-image-92083″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/03/mbr3655_pmu24792-588-3.gif” alt=”Figure 3. The MBR 3655 specimen of Pterodactylus compared to scale with the much smaller PMU 24792 specimen. Note the identical proportions in the skull. ” width=”584″ height=”1359″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/03/mbr3655_pmu24792-588-3.gif?w=584&h=1359 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/03/mbr3655_pmu24792-588-3.gif?w=64&h=150 64w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/03/mbr3655_pmu24792-588-3.gif?w=129&h=300 129w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/03/mbr3655_pmu24792-588-3.gif 588w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 3. The MBR 3655 specimen of Pterodactylus compared to scale with the much smaller PMU 24792 specimen. Note the identical proportions in the skull despite the size difference.
Bennett reported
“PMU 24792: This specimen, which consists of a largely complete articulated skeleton on incomplete 18.5 × 17.5 cm part and counterpart slabs”
Bennett showed only the skull.
Wiman 1925 showed the entire slab (Fig 3). When added to the LPT this specimen nested with the much larger Pterodactylus MBR 3655 F(ig 3), not Gnathosaurus (Fig 1). So it is indeed a juvenile, and a first for Pterodactylus, not for Gnathosaurus. The premaxilla is not expanded laterally on any of Bennett’s proposed juvenile forms.
Differences from the adult: MBR 3655 include a longer metacarpal 4 and longer m4.1 than 4.2. The feet of the small PMU 24792 specimen are relatively smaller than the larger MBR 3655. Ctenochasmatids, like Gnathosaurus, have large feet (Fig 1).
Figure 4. This is figure 7 from Bennett 2025. Yellow areas and reduced skulls added here.
” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/03/bennett.skulls2scale588.jpg?w=225″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/03/bennett.skulls2scale588.jpg?w=584″ class=”size-full wp-image-92088″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/03/bennett.skulls2scale588.jpg” alt=”Figure 4. This is figure 7 from Bennett 2025. Yellow areas and reduced skulls added here.” width=”584″ height=”778″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/03/bennett.skulls2scale588.jpg?w=584&h=778 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/03/bennett.skulls2scale588.jpg?w=113&h=150 113w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/03/bennett.skulls2scale588.jpg?w=225&h=300 225w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/03/bennett.skulls2scale588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 4. This is figure 7 from Bennett 2025. Yellow areas and reduced skulls added here. The smallest one, SNSB-BSPG 1936 is shown reconstructed in figure 7 below. It is a cycnorhamphid.
Bennett’s figure 7 includes seven taxa
now mistakenly attributed by him to Gnathosaurus (Fig 4). None have the laterally expanded anterior rostrum (Fig 5). Bennett’s lateral view of Gnathosaurus (Fig 4) does not show this lateral expansion, to his advantage, since none of his purported juveniles have this trait. None have the elongate skull proportions either. His freehand drawing of PMU 24972 (Fig 4) greatly overestimates the size of the orbit and cranium (see Figs 3, 6).
Figure 4. Gnathosaurus skull with standard DGS colors. Compare to Ctenochasma in figures 1–3.
” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2021/09/gnathosaurus.jpg?w=300″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2021/09/gnathosaurus.jpg?w=584″ class=”size-full wp-image-59657″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2021/09/gnathosaurus.jpg” alt=”Figure 4. Gnathosaurus skull with standard DGS colors. Compare to Ctenochasma in figures 1–3.” width=”584″ height=”429″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2021/09/gnathosaurus.jpg?w=584&h=429 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2021/09/gnathosaurus.jpg?w=150&h=110 150w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2021/09/gnathosaurus.jpg?w=300&h=220 300w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2021/09/gnathosaurus.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 5. Gnathosaurus skull with standard DGS colors. Compare to Bennett’s illustration, copied from Wellnhofer 1970 where details are lacking.
B-St-1936-I-50 = SNSB-BSPG 1936 I 50 = n30 in Wellnhofer 1970: This is a complete specimen nesting within the Cycnorhamphidae in the LPT. It also lacks a laterally expanded premaxilla.
Figure 6. The tiny PMU 24792 specimen nests with the MBR 3655 specimen of Pterodactylus in the LPT, far from Gnathosaurus.
” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/03/pmu_24792_n43pterosaur588.gif?w=300″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/03/pmu_24792_n43pterosaur588.gif?w=584″ class=”size-full wp-image-92091″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/03/pmu_24792_n43pterosaur588.gif” alt=”Figure 6. The tiny PMU 24792 specimen nests with the MBR 3655 specimen of Pterodactylus in the LPT, far from Gnathosaurus.” width=”584″ height=”393″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/03/pmu_24792_n43pterosaur588.gif?w=584&h=393 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/03/pmu_24792_n43pterosaur588.gif?w=150&h=101 150w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/03/pmu_24792_n43pterosaur588.gif?w=300&h=202 300w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/03/pmu_24792_n43pterosaur588.gif 588w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 6. The tiny PMU 24792 specimen nests with the MBR 3655 specimen of Pterodactylus in the LPT, far from Gnathosaurus.
Because Bennett used statistical analysis
rather than the phylogenetic analysis he urged me to learn several decades ago, he once again hobbled his research.
The LPT nested Liaodactylus
(Fig 1) and the AMNH 5147 specimen (Figs 2, 4) with Gnathosaurus. Neither are listed in the Bennett paper. So taxon exclusion adversely affects this paper. Instead he mistakenly assumed ontogenetic growth was allometric, which gave him the leeway to interpret = cherry pick taxa that had a large orbit, short rostrum and short teeth that might have led to Gnathosaurus – but they don’t. They nest elsewhere as unrelated taxa. So inappropriate taxon inclusion also affects this paper.
Figurre 3. B-St-1936-I-50-no30
” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2013/06/b-st-1936-i-50-no30.jpg?w=298″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2013/06/b-st-1936-i-50-no30.jpg?w=584″ class=”size-full wp-image-11501″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2013/06/b-st-1936-i-50-no30.jpg” alt=”B-St-1936-I-50-no30″ width=”584″ height=”587″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2013/06/b-st-1936-i-50-no30.jpg?w=584&h=587 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2013/06/b-st-1936-i-50-no30.jpg?w=150&h=150 150w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2013/06/b-st-1936-i-50-no30.jpg?w=298&h=300 298w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2013/06/b-st-1936-i-50-no30.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 7. B-St-1936-I-50 aka n30 in Wellnhofer 1970 is a tiny Cycnorhamphid in the LPT. Bennett moved it to Gnathosaurus as a juvenile. That is incorrect.
Bennett should have taken his own advice
and run a phylogenetic analyis. That’s the only way to determine which taxa go with whcih other taxa. He should have known about the isometric growth series in pterosaurs and their origin from lepidosaur stock (Peters 2007). Since he didn’t, or refused to, this 2025 paper introduced myth into science and thus was a waste of his time and the readers’ time. Don’t make the same mistake.
I your own studies, take Bennett’s advice from decades ago.
Start with a phylogenetic analysis.
References
Bennett SC 2025. A review of the pterosaur Gnathosaurus subulatus from the Tithonian Solnhofen Lithographic Limestones of Germany: taxonomy and ontogeny. DOI: 10.1127/njgpa/2025/1245
Bennett SC 2002. Soft tissue preservation of the cranial crest of the pterosaur Germanodactylus from Solnhofen. Journal of Vertebrate Paleontology, 22(1): 43-48.
Mayr FX 1964. Die Naturwissenschaftlichen Sammlungen der Philosophisch-theologischen Hochschule, Eichstätt. In:Festschrift zur 400 Jahre Coll. Willibald. Eichstätt: 302–334.
Meyer von CEH 1834. Beiträge zur Petrefactenkunde. [Gnathosaurus subulatus, ein Saurus aus dem lithographischen Schiefer von Solnhofen.] – Museum Senckenbergianum1(3): 1–26 & pls 1–2. [pp. 1–7 & pl. 1]. omic and Systematic Implications. Journal of Vertebrate Paleontology, 16(3):432-444.
Peters D 2007. The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.
Wellnhofer P 1970. Die Pterodactyloidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Abhandlungen der Bayerischen Akademie der Wissenschaften, N.F., Munich 141: 1-133.
Zhou C-F, Gao K-Q, Yi H, Xue J, Li Q and Fox RC 201. Earliest filter-feeding pterosaur from the Jurassic of China and ecological evolution of Pterodactyloidea. R. Soc. open sci. 4: 160672. http://dx.doi.org/10.1098/rsos.160672
Source: https://pterosaurheresies.wordpress.com/2025/03/23/junior-synonyms-for-gnathosaurus-several-mistakes-noted-pt2/
