A possible lungfish burrow in the Upper Cretaceous Adamantina Formation (Bauru Basin, Brazil) and its paleoecological and paleoenvironmental significance

Vertebrates produce a variety of trace fossils, mostly tracks and trackways, coprolites, and burrows resulting from fossorial and subterranean habits. Burrows, particularly, tend to represent temporary or permanent shelter. Vertebrate burrows are relatively understudied in the Brazilian Mesozoic units, as well as in Cretaceous rocks worldwide. This study aims to analyze a paleoburrow in the Upper Cretaceous Adamantina Formation and to discuss its paleobiological and paleoenvironmental implications. A descriptive study was carried out on the paleoburrow morphology, following aspects such as orientation, architecture, and dimensions, and facies association analysis provided the interpretation of the paleoenvironment in which the tracemaker lived. The origin of the paleoburrow was highlighted, as well as the size of its possible producer, besides inferring the exposure time of the paleoburrow from taphonomic interpretations, which contains allochthonous bone remains. The results suggest long periods of dry conditions, as previously suggested for the much-debated Adamantina Formation, interrupted by flooding events as evidenced by facies analysis and suggested by the lungfish burrow. The possibility of a lungfish record also expands the presence of these animals to Adamantina Formation, even though more data are needed to understand the paleoecology of these formations. Keywords: lungfish, paleoburrow, floodplain, Adamantina Formation.