Early tetrapod neck mobility modelled using an extant analogue.

Early tetrapod necks were surprisingly rigid, with most stem tetrapods able to move their heads less than 6° laterally and less than 3° dorsally, and unable to rotate.

• Why it matters: Understanding neck mobility in early tetrapods is crucial for testing hypotheses that increased neck movement facilitated terrestrial adaptation during their evolutionary transition.
• What they did: Using material tests on the axial columns of sturgeon as an analogue, the study modeled lateral flexion, extension, and rotation capacities of early tetrapod necks, focusing on the notochord-dominated axial column.
• The result: The findings suggest that neck mobility did not increase with head-shoulder separation, indicating that neck movement was unlikely to be a driver of this morphological change, which may instead relate to forelimb-driven locomotion.