"More specifically, we find that a particular type of locomotor behavior -- suspensory locomotion, which involves hanging below tree branches, rather than speed -- is associated with increases in variation in numbers of vertebrae across mammals."
Pincho says... My own study in 2017 can also be used as a similar marker where I used hanging to lead to 8 legs... Pincho Paxton: How Animals got 8 legs By combining the two things you have more transitions available. The new study adds to my belief even more, and should work the other way that it adds to the vertebrae belief even more.