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. 2024 Apr 12;7(1):456.
doi: 10.1038/s42003-024-06132-6.

New insights into pterosaur cranial anatomy: X-ray imaging reveals palatal structure and evolutionary trends

He Chen  1   2   3 , Shunxing Jiang  2 , Alexander W A Kellner  4 , Xiaolin Wang  5   6
Affiliations

New insights into pterosaur cranial anatomy: X-ray imaging reveals palatal structure and evolutionary trends

He Chen et al. Commun Biol. .

Abstract

Among the least studied portion of the pterosaur skeleton is the palate, which tends to be poorly preserved and commonly only visible from one side (the ventral portion). Even in well-preserved specimens, the bones tend to be fused, with the limits of individual palatal elements obscured. To shed new light on this region, we employed advanced X-ray imaging techniques on the non-pterodactyloid Kunpengopterus (Wukongopteridae), and the pterodactyloids Dsungaripterus (Dsungaripteridae), Hongshanopterus (Istiodactylidae), and Hamipterus (Hamipteridae). Our analyses revealed the presence of sutures between palatal bones in Dsungaripterus and Kunpengopterus, which resulted in different interpretations of the relation between palatine, ectopterygoid, and pterygoid, leading to a new identification of the palatal openings. Furthermore, our study shows six main observations such as the variation of the angle between the palatine rami and the variation in the relative sizes of the palatal openings. We also point out that the presence of a maxillopalatine fenestra (previously identified as postpalatine fenestra), is unique within Diapsida. Although much more work needs to be done, we showed that advanced X-ray imaging techniques open a window for understanding pterosaur cranial anatomy and provide a new perspective for investigating the evolutionary history of these flying reptiles.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Fig. 1
Fig. 1. CT slices of Dsungaripterus weii IVPP V 26257.
a, c, d CT slices, showing the sutures pointed by arrows and internal structure. b Shows the place where those CT slices are. This specimen’s CT-rendered result is shown in Fig. 2c.
Fig. 2
Fig. 2. The three specimens of Dsungaripterus weii and their CT-rendered results.
a The skull IVPP V 4063 in ventral view. b CT-rendered the left part of the palate of IVPP V 4063 in ventral and dorsal views. c CT-rendered model of IVPP V 26258, showing the contact region of the right side of the palatine, pterygoid, and ectopterygoid in ventral and dorsal views. d CT-rendered model of IVPP V 26257 showing the contact region of the left side of the palatine, pterygoid, and ectopterygoid, in ventral and dorsal views. e The posterior part of the maxilla in ventral, medial, dorsal, and lateral views. f The maxilla process of the jugal in ventral, medial, dorsal, and lateral views. g The palatine in ventral, medial, dorsal, and lateral views. h The pterygoid with unclear posterior boundary in ventral, medial, dorsal, and lateral views. i the ectopterygoid in ventral, medial, dorsal, and lateral views. Abbreviations: asecp articular surface of ectopterygoid, asj articular surface of jugal, asm articular surface of maxilla, aspl articular surface of palatine, aspt articular surface of pterygoid, asv articular surface of vomer, ch choana, fo foramen, laj lacrimal process of jugal, mpf maxillopalatine fenestra, plfo palatine foramen, pplf postpalatine fenestra, poj postorbital process of jugal, stf subtemporal fenestra. Scale bars: a = 100 mm; c–i = 10 mm.
Fig. 3
Fig. 3. The similar structure on the palatal region in pterodactyloids.
a A piece of skull of Hamipterus tianshanensis (left side) IVPP V 18943.3. b CT-rendered bone corresponding to the (a) in dorsal and ventral view. c A close-up shot of the palatine of Ludodactylus SMNK PAL 3828 in dorsal view. d the posterior part of the palate of Hongshanopterus lacustris IVPP V 14852 in ventral view, modified from ref. . e CL-scan results corresponding to the circle area in (d). f CL-scan results corresponding to the circle area in (g). g The posterior part of palate of Kunpengopterus sinensis IVPP V 23674 in dorsal view, modified from ref. . h The posterior part of the palate of Caupedactylus ybaka MN 4726-V in dorsal view, modified from ref. . i The posterior part of the palate of Tupuxuara leonardii IMCF 1052. j The posterior part of the palate of Gnathosaurus subulatus SOS 4580 (cast) in ventral view. k The posterior part of the palate of Pteranodon, modified from ref. . l–r Seven skulls of Anhanguera focus on the palate region, and they are RGM 401880 (lateral-dorsal view on the right side, photographed by Dr. T. Rodrigues), AMNH 22555 (lateral view on the right side), SNSB-BSPG 1982 I 89 (lateral view on the left side), AMNH 25555 (dorsal-lateral view on left side, CT-rendered model modified from ref. , SAO 16494 (ventral view, photographed by Dr. T. Rodrigues), SNSB-BSPG 1982 I 89 (ventral view, photographed by Dr. T. Rodrigues), MN 4805-V (ventral view), respectively. s The posterior part of palate of Tropeognathus mesembrinus BSP 1987 I 46 (cast) in ventral view. Scale bar: a, d, e, g = 10 mm; b = 4.2 mm; j = 20 mm; f = 1 mm; h, i, k, l, m, p, q, r = 50 mm; n = 100 mm; s = 85 mm.
Fig. 4
Fig. 4. The nearly complete palatal region from the other four pterodactyloids.
a Photo of a skull of Hamipterus tianshanensis IVPP V 18943.1 seen on the ventral side, and b is the sketch drawing of it. c Line drawings of the ventral side of Liaodactylus primus PMOL-AP00031, modified from ref. . d Reconstruction of the ventral side of Nyctosaurus gracilis FM P 25026, modified from ref. . e Reconstruction of the ventral side of Aurorazhdarcho micronyx BSP 1936 I 50, modified from ref. . Abbreviations: bp basipterygoid, bs basisphenoid, ch choana, d dentary, ecp ectopterygoid, fo foramen, ipf interpterygoid fenestra, j jugal, ltf lower temporal fenestra, m maxilla, mpf maxillopalatine fenestra, oc occipital condyle, pm premaxilla, pl palatine, pplf postpalatine fenestra, pr palatal ridge, pty pterygoid, ptyf pterygoid fenestra, ps parasphenoid, q quadrate, sq squamosal, stf subtemporal fenestra, v vomer. Scale bars: a, b = 50 mm, c = 20 mm, e = 5 mm.
Fig. 5
Fig. 5. Line drawings of the palatal region in non-pterodactyloid.
a Rhamphorhynchus muensteri CM 11434, modified from ref. . b Cacibupteryx caribensis IGO-V 208, modified from ref. . c Parapsicephalus purdoni GSM 3166, modified from ref. , and the skull length is about 140 mm. d Dorygnathus banthensis SMNS 18969, modified from ref. . e Campylognathoides liasicus CM 11424, modified from ref. . f Scaphognathus crassirostris GPIB 1304 (Nr. 109), modified from ref. . The red represents the palatine and the yellow represents the ectopterygoid. Abbreviations: amp apertura maxillo-premaxillaris, anf antorbital fenestra, bp basipterygoid, ch choana, ecp ectopterygoid, fi foramen incisivum, ipf interpterygoid fenestra, j jugal, lj lower jaw, ltf lower temporal fenestra, m maxilla, mpf maxillopalatine fenestra, na naris, orf orbital fossa, pl palatine, pm premaxilla, pplf postpalatine fenestra, ps parasphenoid, pt pterygoid, q quadrate, stf subtemporal fenestra, utf upper temporal fenestra, v vomer. Scale bar: a, f = 20 mm; b, d = 50 mm; e = 10 mm.
Fig. 6
Fig. 6. The line drawings of three hypothetical models of the palate in ventral view and its evolution in pterosaurs.
a palate model based on Rhamphorhynchus and Cacibupteryx. b Palate model of Kunpengopterus. c Palate model of pterodactyloids. d The cladogram was simplified and modified from ref. . Line drawings of the palates of Rhamphorhynchus, Cacibupteryx, Gnathosaurus, Caupedactylus, Pteranodon, Nyctosaurus, Hongshanopterus, and Anhanguera were reconstructed and modified from previous publications,,,,,,. Abbreviations: bp basipterygoid, ch choana, ipf interpterygoid fenestra, j jugal, ltf lower temporal fenestra, m maxilla, mpf maxillopalatine fenestra, oc occipital condyle, pcf posterior cranial fenestra, pm premaxilla, pplf postpalatine fenestra, ps parasphenoid, ptyf pterygoid fenestra, q quadrate, stf subtemporal fenestra, v vomer.
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