Jonkeria was a large and omnivorous[3] animal, from the Tapinocephalus Assemblage Zone, Lower Beaufort Group, of the South African Karoo.

This is similar to the bone structure of the modern hippopotamus and the extinct aquatic reptile Claudiosaurus, and implies that, like them, Jonkeria was semiaquatic.

[5] Young Jonkeria individuals grew rapidly, similarly to endothermic animals, whereas adults experienced cyclical growth rates.

The authors attributed the cause of the pathology, characterised by bony spicules growing perpendicular to nonpathological fibrolamellar bone tissue, to a bacterial infection resulting from an attack by a predator, as evidenced by puncture marks on the femur.

[2] The cladogram below depicts the results of a phylogenetic analysis of a selection of dinocephalians representing the various recognised subgroups, including Jonkeria, performed by Fraser-King et al. (2019).