Yan-yin Wang

1 INTRODUCTION With few exceptions (e.g. Brown, 1916; Kellner, 1996; Zheng et al., 2021), non-bony connective tissue is not preserved in the dinosaur fossil record. This presents a limitation for studies in areas such as functional morphology and behaviour, which require prior anatomical information on these types of tissues (Witmer, 1995).

Abstract Vertebral ribs of the anterior thorax in extant birds bear bony prongs called uncinate processes, which improve the mechanical advantage of mm. appendicocostales to move air through the immobile lung and pneumatic air sacs. Among non-avian archosaurs, broad, cartilaginous uncinate processes are present in extant crocodylians, and likely have a ventilatory function. Preserved ossified or calcified uncinate processes are known in several non-avian dinosaurs.

Background. The primarily Neotropical distribution of living alligatoroids raises questions as to when and how the ancestors of Alligator sinensis migrated to China. As phylogeny provides a necessary framework for historical biogeographic issues, determining the phylogenetic positions of the Chinese alligatoroids is a crucial step towards understanding global alligatoroid paleobiogeography.