ACKNOWLEDGMENTS
We thank H. O’Brien and J. Lemberg for helpful discussion regarding paleovasculature and tetrapodomorph evolution. We thank J. Gladman for assistance in CT scanning. We thank S. Sumida and an anonymous reviewer who provided helpful comments that improved the quality of the manuscript. We thank the Virginia Tech Geosciences Charles J. Gose Research Award, which funded the CT scanning. This work was performed in part at the Duke University Shared Materials Instrumentation Facility (SMIF), a member of the North Carolina Research Triangle Nanotechnology Network (RTNN), which is supported by the National Science Foundation (grant ECCS-1542015) as part of the National Nanotechnology Coordinated Infrastructure (NNCI).