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Convergence in aquatic locomotion: reconstructing mosasaurian (Squamata: Mosasauria) tail fins from osteological correlates and covariation with extant sharks
Y
J
DOI:10.1017/pab.2025.10080.png)
Abstract
En 中文
The rarity of preserved soft tissues in the fossil record has limited our understanding of the life appearance of extinct vertebrates. However; through examination of various osteological features and comparisons with extant ecomorphological analogues; we can predict some of the external characteristics of ancient taxa. Specifically; for the Cretaceous mosasaurians (a group of seagoing squamates); extant sharks serve as suitable modern analogues because of their comparable caudal vertebral morphologies and ecologies. In this study; we build a novel framework by combining two-block partial least squares (2B-PLS) regression analysis and geometric morphometrics to investigate the relationship between tail fin shape and the underlying musculoskeletal morphology in sharks and mosasaurians. Our analysis reveals a strong correlation between the “tail fin expanded soft tissue” (TFEST) and shape of the associated caudal skeleton/musculature. Moreover; the covariation pattern between these two structures is remarkably similar in sharks and mosasaurians. Based on these findings; we then develop a predictive model that reconstructs the tail fin in mosasaurian taxa without known soft tissues. Our model indicates that all hydropedal forms possessed a bilobed; hypocercal (downturned) fluke; while plesiopedal species lacked a well-developed fleshy dorsal lobe. The variation in fluke morphologies between the four different evolutionary lineages of derived mosasaurians (mosasaurines; halisaurines; plioplatecarpines; and tylosaurines) suggests multiple independent origins of a bilobed tail fin. This study thus highlights the complexity of aquatic adaptations in mosasaurians and demonstrates the utility of predictive models when reconstructing the life appearance of extinct animals.
Keywords:
mosasaurian
tail fin
osteological correlates
shark
geometric morphometrics
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