Fragmentary fossil remains from the Romualdo Formation (Lower Cretaceous) of Brazil, preserved in association with two fish were interpreted as two individuals of a new genus and species of ctenochasmatine pterosaur, Bakiribu waridza Pêgas et al. 2025. Comparison with fossils from the same geological unit show that the remains represent the gill arch apparatus of a large actinopterygian fish. A series of partially articulated bony elements correspond closely in morphology to the ceratohyals, hypohyals, basibranchial and hypobranchials of amiid fish while the purported 'teeth', which lack enamel, dentine tubules and in most cases evidence of a structure corresponding to a pulp cavity, are reinterpreted as gill filaments. Bakiribu waridza is a fish, not a pterosaur and the name, founded on indeterminate remains of an actinopterygian fish, possibly an amiid, should be treated as a nomen dubium. Rather than a regurgitalite this association of several fish remains appears to be a typical Romualdo Formation concretion. This reinterpretation of Bakiribu has negligible impact on our current understanding of the evolutionary history of pterosaurs as ctenochasmatines represented, for example, by Pterodaustro, were already known to be present in South America until the end of the Early Cretaceous.
Unwin et al. (Thu,) studied this question.