Novel information on the cranial anatomy of the tapejarine pterosaur Caiuajara dobruskii

Caiuajara dobruskii is a tapejarid pterosaur from the Cretaceous of the 'Cemitério dos Pterossauros' (pterosaur graveyard) site, a unique pterosaur bonebed which is located at the municipality of Cruzeiro do Oeste (Paraná, Brazil). Preliminary inferences on Caiuajara morphology were founded on a few partial skeletons, with no detail on the skull anatomy. Here we describe a new specimen from the pterosaur graveyard site, which corresponds to the most complete skull of Caiuajara dobruskii known so far. Furthermore, we describe and compare other specimens including the holotype, a paratype, and several other undescribed specimens. The new specimen preserves the posterior portion of the skull, allowing a better comprehension of its morphology and provides an appreciation of the anatomic structures of the basicranium, enabling better interpretation of this region. We also described the lower jaw of Caiuajara, reporting a unique feature of its symphyseal which adds to the diagnosis for the species. A variability in the premaxillary crest is also noted in different specimens of Caiuajara, which might be interpreted as sexual dimorphism or ontogenetic variability. Therefore, those new findings allow a better comprehension of its skull and enables a more precise comparison between the skulls of those extinct flying reptiles

Comparison of the identified ontogenetic stages in the Tapejarinae specimens discussed in this work.

Comparison of the identified ontogenetic stages in the Tapejarinae specimens discussed in this work.</p

Comparison of both morphology of the parietal crest and contact of the premaxilla with the dorsal margin of the skull in the Tapejarinae specimens discussed in this work.

The specimens compared are those Tapejarinae with at least preserved one of those features analysed.</p

Picture of the whole block of specimen CP.V 8175.

(TIF)</p

Picture of skulls belonging to several specimens of <i>Caiuajara dobruskii</i>.

(A) specimen CP.V 1449 (holotype) in right lateral view; (B) specimen CP.V 1005; (C) specimen CP.V 1050–1; (D) inverted specimen CP.V 8171 in left lateral view; (E) inverted specimen CP.V 1448; (F) inverted specimen CP.V 5703. Bold arrows indicate the slight dorsal expansion of the premaxillary posterior process. Scale bar equals 50 mm.</p

The parietal crest of <i>Caiuajara dobruskii</i>.

(A) at the specimen CP.V 8175 in right lateral view; (B) at the specimen CP.V 1449 (holotype) in right lateral view. Scale bar equals 50 mm.</p

Morphological disparity in some <i>Caiuajara dobruskii</i> from smaller to larger individuals.

From left to right, CP.V 1050–1, CP.V 8171, CP.V 8175, CP.V 1447, CP.V 1449, CP. 1448, and CP.V 1005. Scale bar equals 50 mm.</p

<i>Caiuajara dobruskii</i> CP.V 8175 preserved cranium and postcranial elements measurements.

Caiuajara dobruskii CP.V 8175 preserved cranium and postcranial elements measurements.</p

Schematic drawing of specimen CP.V 8175 skull and lower jaw with their respective measures.

Scale bar equals 50 mm.</p

The mandibular symphysis of <i>Caiuajara dobruskii</i>.

(A) Picture in posterodorsal view; (B) schematic drawing in posterodorsal view; (C) picture in posterior view; (D) schematic drawing in posterior view. Shaded patches are marking concavities as a result of the suture processes of the symphyseal shelf. Scale bar equals 50 mm.</p