Fig. 5: Comparative schematic of the organization of bone tissue in two Carboniferous stem tetrapods, Whatcheeria and Greererpeton, throughout ontogeny.

Whatcheeria (a–d) is a large-bodied predator whose juvenile growth is characterized by fibrolamellar bone (a) that is eventually remodeled and completely replaced with parallel-fibered tissue (b, c) and subsequent slow deposition of lamellar bone (c, d). By contrast, Greererpeton³⁷ (e–g) is characterized by moderately paced bone deposition, even early in ontogeny (e), with a distinct lamellar band of bone deposited at the late juvenile stage (e–g). Sub-adult growth in Greererpeton is subsequently characterized by slowly deposited tissues (f) as well as endosteal deposition that results in a particularly thick adult cortex (g). Scale bar = 5 mm.