The subarctometatarsus: intermediate metatarsus architecture demonstrating the evolution of the arctometatarsus and advanced agility in theropod dinosaurs

Abstract

White, M.A., March, 2009. The subarctometatarsus: intermediate metatarsus architecture demonstrating the evolution of the arctometatarsus and advanced agility in theropod dinosaurs. Alcheringa 33, 1–21. ISSN 0311-5518.

The subarctometatarsus is a plesiomorphic form of arctometatarsus. Five individual subarctometatarsalian specimens are examined in this study including Microraptor gui, Sinornithosaurus millenii, Sinovenator changii, Sinovenator sp. and Sinornithoides youngi. Bivariate analysis illustrates a closer relationship between subarctometatarsalians and small theropods possessing the plesiomorphic theropod metatarsus (e.g. Compsognathidae and Archaeopteryx). Reduced major axis (RMA) analysis supported this conclusion but also indicates a distinct statistical difference between the three categories of theropod metatarsus. Additionally, development of the subarctometatarsus is inferred to have been linked to advanced cursoriality as implicated for the arctometatarsus. Structural similarity between the subarctometatarsus and the arctometatarsus portrays a common mechanical function of being able to withstand the forces of high impact with the substrate. Phylogenetic analysis reveals five independent origins of the arctometatarsus.

Key words:

• subarctometatarsus
• arctometatarsus
• metatarsus
• Microraptor gui
• Sinornithosaurus millenii
• Sinovenator changii
• Sinornithoides youngi

Acknowledgements

Special thanks to Professor Guang Shi for his supervisory role throughout the course of this research. Special thanks also to Professor Xu Xing for his supervisory role and for his invitation and assistance in examining subarctometatarsalian specimens held at the Institute of Vertebrate Palaeontology and Palaeoanthropology, Beijing. Thanks also to Professor Tan Lin and his team at the Stratigraphy and Palaeontology Research Committee of the Inner Mongolia Geological Society and the Longhao Geology and Palaeontology Research Center of Inner Mongolia for their invitation and assistance in examining ornithomimid specimens. Lastly special thanks to Dr Eric Snively, Dr Zhou Zhonghe and Dr Stephen McLoughlin for reviewing this work.