Meeting Abstract
Vertebral size, shape, and total vertebral numbers have been correlated with ecology, feeding mechanics, and locomotor type in modern vertebrates. However, it is unclear if these morphologies are related habitat preferences in early tetrapods, critical for documenting transitions such as invasion of land. Temnospondyls were an ancient lineage of stem-amphibians that ranged in size from 5 millimeters to 5 meters, and prevailed for over 200 million years. This clade offers an excellent opportunity to examine environmental correlations on a macroevolutionary timescale because they underwent repeated diversifications into new habitats. In addition, their vertebral morphologies include over half of the categories present during the Paleozoic. Early works on this group categorized their complex vertebral diversity; however, no study has determined how this diversity affects biomechanically-relevant traits and correlates with ecology. We conducted a 2D geometric morphometric study on presacral vertebrae in temnospondyls using a total of 13 landmarks to capture neural spine and intercentrum form. We reconstructed habitat shifts using a threshold model, and tested for correlations between morphology and environment. Procrustes ANOVAs revealed a significant amount of variation in intercentrum shape is explained by habitats. Conversely, 90% of variation in neural spine size and shape is unexplained by phylogeny or habitat. Ancestral state reconstructions revealed temnospondyls were not tightly constrained and could transition into new environments every 30 million years. Vertebral innovations appear to have been critical for tetrapod habitat invasion and reinvasion, emphasizing the need for future studies on extinct tetrapods to establish patterns for vertebral form-function.
