Morphogeometric analysis of tooth plates of Lepidosiren paradoxa (Sarcopterygii, Dipnoi) to infer Late-Holocene paleoenvironmental variations in the South American Gran Chaco

Abstract

The Gran Chaco region, a highly biodiverse forested ecoregion in South America, has undergone significant environmental changes in the past. Understanding these past environmental conditions can help in assessing how humans and ecosystems have responded to past climate changes. To develop a new proxy for reconstructing past environmental conditions in this region, we morphometrically analysed the pterygopalatine tooth plates of Lepidosiren paradoxa, the sole representative species of lungfish in South America. We tested whether its permanent dentition correlates with environmental conditions for this species and the species it feeds on. By examining 110 pterygopalatine tooth plates from archaeological sites and comparing them with seven contemporary tooth plates, we identified morphological similarities that confirm the archaeological specimens as L. paradoxa. Our findings suggest a trend towards more favourable environmental conditions from approximately 1700 years BP to the present, characterized by warming temperatures and increased humidity. This trend peaked around 1000 years BP, as evidenced by a notable change in tooth plate form expression, specifically an increase in size and more pronounced shape features. This findings aligns with regional paleoenvironmental data, indicating a shift from semi-arid to more humid climates during this period. The study’s results contribute to our understanding of the late Holocene paleoenvironmental variations in the South American Gran Chaco and demonstrate the potential of tooth plate morphology as a paleoenvironmental indicator.