A new approach to the fossil flamingo from Pie de Vaca locality (Puebla, central México) and some taxonomic and biogeographic implications

Pie de Vaca is a late Cenozoic site located in the municipality of Tepexi de Rodríguez, Puebla, Mexico. It is known for its ichnofossil record including footprints of camelids, carnivores, and peccaries, as well as the taphoglyph of an almost complete flamingo skeleton. This fossil specimen was previously identified as Phoenicopterus stocki, a small extinct species, through linear osteometric comparisons of the tibiotarsus. This study presents new data on the morphological features of the taphoglyph skull impression. The extant genera Phoenicopterus, Phoenicoparrus, and Phoeniconaias differ in the morphology and size of the skulls. The fossil specimen analyzed exhibits a small head and a distinct cranial shape when compared to those genera. The results confirm that the taphoglyph belongs to an adult of a small phenicopterid. The two-dimensional morphometric comparisons of the tibiotarsus based on the ratio of distal depth to distal width shows that the taphoglyph is larger than Phoeniconaias minor and Phoenicopterus minutus, and more similar to Phoenicopterus ruber. The analysis revealed previously unknown characteristics of the taphoglyph and refutes its previous identification as the extinct species Phoenicopterus stocki. The specimen appears to be a small adult flamingo, but it differs from known extant genera. These findings confirm the presence of a group of small flamingos in the late Cenozoic of North America and Mexico, with the most complete specimen being the taphoglyph of Pie de Vaca. However, further research remains necessary to establish its connections with extinct and extant phenonicopterids.