Earth:Bakiribu

Bakiribu (lit. comb) is an extinct genus of ctenochasmatid pterosaurs known from the Early Cretaceous (Aptian–Albian age) Romualdo Formation of Brazil. The genus contains a single species, Bakiribu waridza, known from the fragment remains of two individuals preserved in a regurgitalite. This indicates the pair may have been consumed by a spinosaurid theropod dinosaur. It represents the first member of the broader clade Archaeopterodactyloidea described from the Romualdo Formation. Bakiribu has a unique pattern of closely-packed comblike teeth in the upper and lower jaws that may have been used for filter feeding, similar to the closely related Pterodaustro.

Discovery and naming

Several years prior to 2025, Aline M. Ghilardi and William B. S. Almeida discovered a calcareous concretion from the Romualdo Formation, part of the Araripe Basin, in northeastern Brazil in the collection of the Museu Câmara Cascudo. The concretion specimen had remained at the museum for several years without study; its exact provenance is unknown. The concretion style of preservation, with specimens preserved in a part and counterpart visible when the block is split open, is typical of material collected in this formation. The two specimen parts were accessioned as MCC1271.1-V and MCC1271.2-V at the Museu Câmara Cascudo (MCC), part of the Federal University of Rio Grande do Norte in Rio Grande do Norte, Brazil. It comprises the fragmented upper and lower jaws of two pterosaur individuals, as well as four associated fish, likely of the genus Tharrhias, with their heads pointing in the same direction.

Subsequently, researchers recognized that the pterosaur material in the concretion represented a novel taxon. They arranged for one half of the concretion (MCC 1271.2-V) to be transferred to the Museu de Paleontologia Plácido Cidade Nuvens (MPSC) in Ceará, Brazil, which is closer to the region from which it was collected. It is now deposited at this institution as specimen MPSC R 7312.

In 2025, R. V. Pêgas and colleagues described Bakiribu waridza as a new genus and species of ctenochasmatid pterosaurs based on these fossil remains. The generic name, Bakiribu, is a Kariri word meaning 'comb', referencing the comblike teeth of this taxon and its relatives. The specific name, waridza, is a Kariri word meaning 'mouth' The combined binomial name is intended to reference the animal's unique dentition, as well as honor the Kariri people—the indigenous inhabitants of the type locality—and their cultural heritage. Of the jaw fragments identified (labeled as a–g), a was assigned as the holotype specimen, with b–d likely belonging to this individual, while e was assigned as a paratype, with f and g likely belonging to the same individual.

Description

Skull of the related Pterodaustro, which had a comparable arrangement of long, comblike teeth, albeit only in the lower jaw

Like many ctenochasmatid pterosaurs, Bakiribu has very elongate jaws with many closely-packed teeth. The upper jaw tip is slightly more expanded than that of the lower jaw, allowing the two larger and two smaller jaw fragments observed in the concretion to be recognized as the upper and lower jaws of at least two individuals. The jaws were slightly curved upward, similar to Gegepterus and other members of this family. The extreme degree to which teeth are packed into the jaws is most comparable to Pterodaustro although the dense, comblike teeth are only present in the lower jaw. In Bakiribu, there are may have been between 440 and 568 teeth per side of the jaw, with the interdental gaps (space between teeth) smaller than the diameter of the teeth themselves. In contrast, the teeth of Pterodaustro are so densely packed that there are no interdental gaps. Two autapomorphies (unique derived traits) were identified in Bakiribu; first, the teeth exhibit acrodont implantation (teeth implanted at the top of an alveolar ridge, rather than in sockets) in both the upper and lower jaws, and second, the tooth crowns have a subquadrangular cross-section. In comparison only the upper jaw teeth of Pterodaustro are acrodont, and the teeth of all other ctenochasmatids are circular or elliptical in cross-section.

The tooth and skull morphology of Bakiribu is somewhat transitional between the older Ctenochasma and younger Pterodaustro, with the former having shorter, more widely-spaced teeth and the latter having longer, more densely-packed teeth. Regardless, all of these taxa are speculated to have used their unique dentition as a means for filter feeding.

Paleobiology

The concretion specimen containing both Bakiribu specimens was identified as a likely regurgitalite, meaning the preserved remains of the stomach contents regurgitated by a predator. The likely producer of this regurgitalite was a spinosaurid theropod dinosaur, as these are known to have lived in the Romualdo Formation paleoenvironment and were large enough to predate on smaller pterosaurs. The presence of four fish preserved in the same orientation supports this hypothesis, as modern piscivorous animals are known to preferentially consume fish head-first. Pêgas and colleagues suggested that the pterosaurs were consumed first, and that the discomfort of digesting them (especially the tooth-bearing jaw bones) caused it to regurgitate them in addition to its more recent meal of fish.

Notably, Bakiribu is the only archaeopterodactyloid pterosaur yet described from the Romualdo Formation. This may indicate that these specimens are allochthonous, having originated from a different locality. Pêgas and colleagues speculated that the predator that regurgitated the Bakiribu specimens consumed them outside of the environment that preserves other Romualdo Formation pterosaurs. This is further supported by the fact that ctenochasmatids are otherwise only found in formations representing depositional environments with calm water, such as lagoons and lakes. The Romualdo Formation preserves marine environment, which would be unusual for a ctenochasmatid to inhabit.

Classification

Speculative life restoration of the closely related Pterodaustro

In their 2025 description of Bakiribu, Pêgas and colleagues recovered this taxon as the sister taxon to Pterodaustro, forming the clade Pterodaustrini. These two genera are in turn sister to Ctenochasma spp., together forming the clade Ctenochasmatinae, which is a subset of the broader family Ctenochasmatidae. Beipiaopterus and Gegepterus, both of which have been traditionally regarded as pterodastrinins, were instead recovered as non-ctenochasmatine ctenochasmatids based on a reanalysis of their respective anatomies. These results are displayed in the cladogram below:

Archaeopterodactyloidea

Germanodactylus cristatus     Germanodactylus rhamphastinus         Pterodactylus antiquus       Diopecephalus kochi   Ctenochasmatoidea     Normannognathus wellnhoferi       Cycnorhamphus suevicus     Gallodactylus canjuersensis           Aerodactylus scolopaciceps   Ctenochasmatidae       Ardeadactylus longicollum     Huanhepterus quingyangensis           Gladocephaloideus jingangshanensis     Feilongus youngi     Moganopterus zhuiana         Elanodactylus prolatus       Forfexopterus jeholensis       Gegepterus changi     Beipiaopterus chenianus                   Liaodactylus primus       Cathayopterus grabaui     Pterofiltrus qiui         Ctenochasmatinae     Ctenochasma elegans     Ctenochasma taqueti     Pterodaustrini   Bakiribu waridza     Pterodaustro guinazui       Gnathosaurinae   Plataleorhynchus streptophorodon         Lusognathus almadrava     Garudapterus buffetauti         Gnathosaurus subulatus     Tacuadactylus luciae

A non-peer-reviewed preprint published later in 2025 reinterpreted the pterosaur 'jaw bones' as the gill arch apparatus of an amiid fish, and suggested the specimen does not represent a regurgitalite.

Palaeoevironment

Restoration of the environment of the Romualdo Formation

Bakiribu lived in a marginal marine habitat. It lived alongside dinosaurs including the spinosaurids Irritator and its possible junior synonym Angaturama, and the smaller theropods Aratasaurus, Santanaraptor, and Mirischia.

Other animals known from the formation include the crocodylomorphs Araripesuchus and Caririsuchus, turtles such as Santanachelys, and many other pterosaurs such as Tropeognathus, Anhanguera and Tapejara.

References

Template:Pterosauria Wikidata ☰ Q136756872 entry