2025 azhdarchid phylogenetic study stumbles on taxon exclusion/inclusion issues
This is what happens
in supermatrix studies. Myths and mistakes are nourished by inclusion – without observation and specimen study. Omitted taxa remain omitted.
Even so, this is common practice and academically acceptable.
Thomas and McDavid promote several myths here in their abstract.
“Azhdarchidae is a clade of pterosaurs which includes the largest-ever flying animals.
This is incorrect. Large size evolved after flightlessness, as in birds (Fig 1). The wings were too small – way too small.
Figure 1. Click to enlarge. The largest flying and non-flying birds and pterosaurs to scale.
” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2018/06/largest_pterosaurs588.jpg?w=300″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2018/06/largest_pterosaurs588.jpg?w=584″ class=”size-full wp-image-31423″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2018/06/largest_pterosaurs588.jpg” alt=”Figure 1. Click to enlarge. The largest flying and non-flying birds and pterosaurs to scale.” width=”584″ height=”441″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2018/06/largest_pterosaurs588.jpg?w=584&h=441 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2018/06/largest_pterosaurs588.jpg?w=150&h=113 150w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2018/06/largest_pterosaurs588.jpg?w=300&h=227 300w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2018/06/largest_pterosaurs588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 1. The largest flying and non-flying birds and pterosaurs to scale.
“The evolutionary history of this clade and its closest relatives remains incompletely understood and highly debated.”
Still incomplete in 2025 due to taxon exclusion. See the large pterosaur tree (266 taxa) for the list of largely complete taxa missing from the Thomas and McDavid study.
“To investigate this, we combined multiple preexisting datasets with 29 new operational taxonomic units and 57 new characters, resulting in the most comprehensive phylogenetic analysis of pterosaurs published to date, with a focus on Azhdarchomorpha.”
Other than Peters 2007 (not cited) prior analyses also suffered from taxon exclusion.
The LPT does not test largely inocmplete texa, Most azhdarchids are incompletely known. Thomas and McDavid omitted several completely known taxa that preceded the entry of azhdarchids and they included unrelated tapejarids (Fig 1).
Figure 1. The ancestry of Huanhepterus. It retained a relatively short metacarpus inherited from Beipiaopterus.
” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2012/04/huanhepterus-kin.jpg?w=215″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2012/04/huanhepterus-kin.jpg?w=584″ class=”size-full wp-image-5738″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2012/04/huanhepterus-kin.jpg” alt=”The ancestry of Huanhepterus. I” width=”584″ height=”816″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2012/04/huanhepterus-kin.jpg?w=584&h=816 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2012/04/huanhepterus-kin.jpg?w=107&h=150 107w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2012/04/huanhepterus-kin.jpg?w=215&h=300 215w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2012/04/huanhepterus-kin.jpg 623w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 2. The ancestry of Huanhepterus. It retained a relatively short metacarpus inherited from Beipiaopterus.
“Higher level phylogenetic taxonomy of Azhdarchomorpha is revised based on the results of this analysis, and three new clade names are established: Shenzhoupterinae (cl. nov.) for the subgroup of Chaoyangopteridae containing Shenzhoupterus that is sister to the existing Chaoyangopterinae;”
In the LPT, Shenzhoupterus and tiny Nemicolopterus (correctly omitted from the Thomas and McDavid study) are not related to Azhdarchidae, but nest between Eopteranodon and Dsungaripterus.
“Concilazhia (cl. nov.) for the clade uniting Chaoyangopteridae and Azhdarchiformes; and Serpennata (cl. nov.) for the clade with highly elongated cervical series that includes the giant (10 m wingspan) Quetzalcoatlus and Arambougiania”
Huanhepterus (Fig 2) also has a highly elongated cervical series.
“The iconic genus Quetzalcoatlus is recovered as polyphyletic, with its giant and moderately large species belonging to separate clades within Serpennata}.”
This may or may not be so, but without any sort of understanding of outgroup taxa, and so many ingroup taxa largely incomplete, this is a problem that needs to be admitted.
“Gigantism evolved convergently at least four times in quetzalcoatline azhdarchids: in Cryodrakon, once in a clade containing Hatzegopteryx and its closest relatives, and twice independently in different lineages of Serpennata.”
This may or may not be so, but without any sort of understanding of outgroup taxa, and so many ingroup taxa largely incomplete, this is a problem that needs to be admitted.
From the definitions section of Thomas and McDavid:
“Azhdarchomorpha Pegas, Holgado, Ortiz David, Baiano & Costa, 2022. Definition. The most inclusive clade containing Azhdarcho lancicollis Nesov, 1984, but not Thalassodromeus sethi Kellner & Campos, 2002 or Tapejara wellnhoferi Kellner, 1989 (Pegas et al., 2022).”
In the LPT tapejarids are not related to azhdarchds. Sharp-snouted tapejarids are derived from sharpt-snouted germanodctylids. Azhdarchids arise from tiny dorygnathids.
Figure 2. Thanatosdrakon compared to Quetzalcoatlus showing the distinct morphologies.
” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2022/04/thanatosdrakon_quetz_recon2-588.gif?w=193″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2022/04/thanatosdrakon_quetz_recon2-588.gif?w=584″ class=”size-full wp-image-66921″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2022/04/thanatosdrakon_quetz_recon2-588.gif” alt=”Figure 2. Thanatosdrakon compared to Quetzalcoatlus showing the distinct morphologies.” width=”584″ height=”908″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2022/04/thanatosdrakon_quetz_recon2-588.gif?w=584&h=908 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2022/04/thanatosdrakon_quetz_recon2-588.gif?w=96&h=150 96w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2022/04/thanatosdrakon_quetz_recon2-588.gif?w=193&h=300 193w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2022/04/thanatosdrakon_quetz_recon2-588.gif 588w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 2. Thanatosdrakon compared to Quetzalcoatlus showing the distinct morphologies.
There are no skeletal reconstructions in this study.
The only azhdarchid illustrations are freehand paintings and colorful ‘sticker’ graphics.
So here’s Quetzalcoatlus (Fig 3) compared to Thanatosdrakon, which entered the LPT as the largest Pteranodon. Note the much larger wings on the latter. Thomas and McDavid accepted Thanatosdrakon as an azhdarchid because it was mistakenly considered one in an earlier study. That’s the danger of creating a supermatrix from prior work.
Figure 1. Microtuban wing compared to scale with the unnamed flightless pterosaur, SOS2428.
” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/08/sos2428.jpg?w=290″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/08/sos2428.jpg?w=584″ class=”size-full wp-image-87986″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/08/sos2428.jpg” alt=”Figure 1. Microtuban wing compared to scale with the unnamed flightless pterosaur, SOS2428.” width=”584″ height=”604″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/08/sos2428.jpg?w=584&h=604 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/08/sos2428.jpg?w=145&h=150 145w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/08/sos2428.jpg?w=290&h=300 290w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/08/sos2428.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 4. Microtuban wing compared to scale with the unnamed flightless pterosaur, SOS2428.
The smallest azhdarchids
included as some of the 23 new ingroup taxa added to the dataset of Thomas and McDavid include Microtuban (Fig 4) and Vectidraco.
Though small, Microtuban has a vestigial distal phalanx on its wing, resembling a digit 4 wing claw.
Vectidraco is known from a pelvis and sacrum that shares traits with both tapejarids and azhdarchids, illustrated and compared earlier here. Don’t Pull a Larry Martin by focusing on one trait or a dozen. That will lead you to confusing homology with convergence. Always consider the entire skeleton (Fig 1).
It will be worth your while to
take a moment to compare a few tapejarids to Quetzalcoatlus (Fig 1). These taxa do not resemble one another – and yet academics have been lumping them together for more than 20 years (Kellner 2003) due to taxon exclusion.
That false interrelationship needs to end. Peters 2007 has been ignored ever since, following Bennett’s curse, “You will not be published – and if you are published, you will not be cited.”
Figure 5. On the left: BSPG 1911 I 31 (no. 42 in the Wellnhofer 1970 catalog) with volant wingspan compared to JME SOS 2428 with a non-volant wingspan.
” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/11/sos2428-2.jpg?w=300″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/11/sos2428-2.jpg?w=584″ class=”size-full wp-image-95118″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/11/sos2428-2.jpg” alt=”Figure 5. On the left: BSPG 1911 I 31 (no. 42 in the Wellnhofer 1970 catalog) with volant wingspan compared to JME SOS 2428 with a non-volant wingspan. ” width=”584″ height=”304″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/11/sos2428-2.jpg?w=584&h=304 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/11/sos2428-2.jpg?w=150&h=78 150w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/11/sos2428-2.jpg?w=300&h=156 300w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/11/sos2428-2.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 5. On the left: BSPG 1911 I 31 (no. 42 in the Wellnhofer 1970 catalog) with volant wingspan compared to JME SOS 2428 with a non-volant wingspan. See figure 4 lateral view of the flightless pterosaur SOS 2428.
Not included in any prior study
and likewise omitted from Thomas and McDavid 2025 is the plover-sized, unnamed and flightless Microtuban relative, JME-SOS 2428, the first reported flightless pterosaur (Figs 4, 5). In the LPT the 2428 specimen nests just outside tested azhdarchids.
References
Kellner AWA 2003. Pterosaur phylogeny and comments on the evolutionary history of the group. Geological Society, London, Special Publications, 217(1), 105–137.
Peters D 2007. The origin and radiation of the Pterosauria. Flugsaurier. The Wellnhofer Pterosaur Meeting, Munich 27
Thomas HN and McDavid SN 2025. Enter the dragons:the phylogeny of Azhdarchoidea (Pterosauria: Pterodactyloidea) and the evolution of giant size in pterosaurs, Journal of Systematic Palaeontology, 23:1, 2569368,
DOI: 10.1080/14772019.2025.2569368
The large pterosaur tree at ReptileEvolution.com
‘Thanatosdrakon’ enters the LPT as the largest Pteranodon – not an azhdarchid
Source: https://pterosaurheresies.wordpress.com/2025/11/07/2025-azhdarchid-phylogenetic-study-stumbles-on-taxon-exclusion-inclusion-issues/
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