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. 2025 Sep 16:13:e19711.
doi: 10.7717/peerj.19711. eCollection 2025.

Azhdarchid pterosaur diversity in the Bayanshiree Formation, Upper Cretaceous of the Gobi Desert, Mongolia

R V Pêgas  1 , Xuanyu Zhou  2 , Yoshitsugu Kobayashi  3
Affiliations

Azhdarchid pterosaur diversity in the Bayanshiree Formation, Upper Cretaceous of the Gobi Desert, Mongolia

R V Pêgas et al. PeerJ. .

Abstract

Pterosaur remains are very rare in Mongolian Mesozoic deposits, in stark contrast with the great abundance of dinosaur fossils in the region. This contribution presents a reassessment of the azhdarchid pterosaur remains from the Bayanshiree Formation's "upper beds" (Turonian-Santonian), represented by two specimens coming from two distinct localities: the Burkhant and the Bayshin Tsav azhdarchids. These specimens, collected by the Japanese-Mongolian Joint Paleontological Expedition and originally described in 2009, have been previously interpreted as indeterminate azhdarchids. Under the light of current knowledge on the morphological diversity of azhdarchid cervical vertebrae, as well as on the taxonomic and phylogenetic signals these skeletal elements carry, we herein identify diagnostic features and reassess the phylogenetic affinities of the Bayanshiree azhdarchids in further detail. Our results suggest that the Burkhant azhdarchid, hereby named Gobiazhdarcho tsogtbaatari gen. et sp. nov., represents a medium-sized (3.0-3.5 meters in wingspan) basal member of a Quetzalcoatlus-Arambourgiania lineage. The Bayshin Tsav azhdarchid, Tsogtopteryx mongoliensis gen. et sp. nov., is recovered as a basal member of a Hatzegopteryx-lineage and, surprisingly, seems to represent a small form under 2 m in wingspan. Our results shed fresh light on the diversity and phylogeny of azhdarchid pterosaurs, and reinforce the reoccurring pattern of coexistence between multiple, differently-sized azhdarchid species from a same deposit.

Keywords: Azhdarchidae; Cervical vertebrae; Late Cretaceous; Mongolia; Phylogeny; Pterosauria; Systematics.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Figure 1
Figure 1. Map of Mongolia.
Highlighted are the aimags (provinces) of Dornogovi (East Gobi) and Ömnögovi (South Gobi) and the localities of Burkhant (1) and Bayshin Tsav (2).
Figure 2
Figure 2. MPC−Nd 100/302a, atlantoaxis of the holotype of Gobiazhdarcho tsogtbaatari.
(A) Anterodorsal view; (B) left lateral view; (C) dorsal view; and (D–F) respective schematic drawings. (G) Posterior view; (H) right lateral view; and (I) ventral view; and (J–L) schematic drawings. Abbreviations: ana, atlas neural arch; ai, atlas intercentrum; co, condyle; ct, cotyle; dy, diapophysis; ep, epipohysis; fo, fossa; if, intervertebral foramen; nc, neural canal; ns, neural spine; po, postzygapophysis; poex, postexapophysis; pof, postzygapophyseal facet; pop, postzygapophyseal pedicle; py, parapophysis. Scale bar = 20 mm.
Figure 3
Figure 3. MPC−Nd 100/302b, cervical III of the holotype of Gobiazhdarcho tsogtbaatari.
(A) Dorsal view; (B) ventral view; (C) anterior view; and (D–F) respective schematic drawings. (G) Left lateral view; (H) right lateral view; and (I) posterior view; and (J–L) schematic drawings. Abbreviations: adj.fo, adjacent foramen; co, condyle; ct, cotyle; dy, diapophysis; ipoel, interpostexapophyseal ridge; nc, neural canal; ns, neural spine; poex, postexapophysis; pop, postzygapophyseal pedicle; pop.b, postzygapophyseal pedicle base; poz, postzygapophysis; prex, preexapophysis; prf, prezygapophyseal facet; prp, prezygapophyseal pedicle; prz, prezygapohysis; su, sulcus; ta.dis, taphonomic distortion; tr, transverse ridge; vlr, ventral longitudinal ridge; vtb, ventral tubercle. Scale bar = 20 mm.
Figure 4
Figure 4. MPC−Nd 100/302c, cervical VI of the holotype of Gobiazhdarcho tsogtbaatari.
(A) Dorsal view; (B) ventral view; (C) posterior view; and (D–F) respective schematic drawings. (F) Right lateral view; (H) left lateral view; and (I, J) schematic drawings. Abbreviations: adj.fo, adjacent foramen; co, condyle; ep, epipophyis; epk, epipophyseal keel; ipoel, interpostexapophyseal ridge; lf, lateral fossa; nc, neural canal; poex, postexapophysis; pof, postzygapophyseal facet; pop, postzygapophyseal pedicle; psp, posterior spinous process; tr, transverse ridge; vlr, ventral longitudinal ridge. Scale bar = 20 mm.
Figure 5
Figure 5. MPC−Nd 100/303, cervical VI of the holotype of Tsogtopteryx mongoliensis.
(A) Anterior view; and (B) schematic drawing; (C) dorsal view; and (D) schematic drawing; (E) ventral view; and (F) schematic drawing; (G) left lateral view; and (H) schematic drawing; right lateral view; and (J) schematic drawing. Abbreviations: adj.fo, adjacent foramen; asp, anterior spinous process; ct, cotyle; cr, cervical rib; hy, hypapophysis; nc, neural canal; nr, neural ridge; poex.b, postexapophyseal base; pop.b, postzygapophyseal pedicle base; prf, prezygapophyseal facet; pr.k, prezygapophyseal keel; prp, prezygapophyseal pedicle; psp, posterior spinous process; tf, transverse foramen; tr, transverse ridge; vl.r, ventrolateral ridge; vt, vestibule; vcs, vertebrocostal sulcus. Scale bar = 10 mm.
Figure 6
Figure 6. Time-scaled strict consensus phylogenetic tree.
Partial tree focused on the Azhdarchomorpha (the remaining of the tree is available in the File S3). 1, Azhdarchomorpha; 2, Chaoyangopteridae. Azhdarchid silhouettes modified from the Quetzalcoatlus silhouette by Mark P. Witton & Darren Naish, distributed by PhyloPic (phylopic.org/) under a CCBY 3.0 license (https://creativecommons.org/licenses/by/3.0/).
Figure 7
Figure 7. Life restoration of the Bayanshiree azhdarchids.
The coexistence between Gobiazhdarcho tsogtbaatari and Tsogtopteryx mongoliensis in the Bayanshiree paleoenvironment, with a group of Gobihadros mongoliensis nearby. Artwork by Zhao Chuang.
See this image and copyright information in PMC

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