Richard Whitekettle, «Rats are Like Snakes, and Hares are Like Goats: A Study in Israelite Land Animal Taxonomy», Vol. 82 (2001) 345-362
Israelite taxonomic thought drew a contrast between a land animal taxon referred to by the words Cr#$ or #&mr that contained animals such as rats and snakes (Land Animals I), and a land animal taxon referred to by the words hmhb or hyx that contained animals such as hares and goats (Land Animals II). This essay shows that the Land Animals I taxon was characterized by locomotory movement in the horizontal plane and the Land Animals II taxon was characterized by locomotory movement in the vertical plane. Thus, the contrast was between land animals that were perceived to move along the ground (Land Animals I) and land animals that were perceived to move over the ground (Land Animals II).
Snakes use various techniques for locomotion33. First, there is a method of locomotion (rectilinear movement) which involves neither lateral bending nor vertical lifting of the body. Instead, movement is achieved through waves of muscular contraction passing along the length of the body. Second, there are methods of locomotion (lateral undulation, concertina locomotion, sidewinding) which involve lateral bending. This is seen in the following dorsal drawing of a snake engaged in ‘concertina’ movement34:
In some cases of locomotion that involve lateral bending, the full length of the body remains in contact with the substrate throughout the locomotory process. In such cases, the snake’s body engages in no vertical movement. In other cases of locomotion which involve lateral bending, some vertical movement occurs, as parts of the body are lifted off the substrate, thrust ahead, and then re-placed on the substrate. These vertical movements, however, are only high enough to allow the part of the body in motion to clear the substrate and transit ahead. Consequently, the predominant impression of snake locomotion that involves both lateral bending and vertical lifting, is centered in the lateral undulations.
In summary, the locomotion of legless Land Animals involves movement that is either exclusively or largely confined to a horizontal plane relative to the ground.