  Terrestrial animals must often negotiate heterogeneous, varying environments.
Accordingly, their locomotive strategies must adapt to a wide range of terrain,
as well as to a range of speeds in order to accomplish different behavioral
goals. Studies in \textit{Drosophila} have found that inter-leg coordination
patterns (ICPs) vary smoothly with walking speed, rather than switching between
distinct gaits as in vertebrates (e.g., horses transitioning between trotting
and galloping). Such a continuum of stepping patterns implies that separate
neural controllers are not necessary for each observed ICP. Furthermore, the
spectrum of \textit{Drosophila} stepping patterns includes all canonical
coordination patterns observed during forward walking in insects. This raises
the exciting possibility that the controller in \textit{Drosophila} is common
to all insects, and perhaps more generally to panarthropod walkers. Here, we
survey and collate data on leg kinematics and inter-leg coordination
relationships during forward walking in a range of arthropod species, as well
as include data from a recent behavioral investigation into the tardigrade
\textit{Hypsibius exemplaris}. Using this comparative dataset, we point to
several functional and morphological features that are shared amongst
panarthropods. The goal of the framework presented in this review is to
emphasize the importance of comparative functional and morphological analyses
in understanding the origins and diversification of walking in Panarthropoda.

Biological Physics;Neurons and Cognition