Primitive eureptilians were all small, superficially lizard-like forms, that probably scurried through the Paleozoic undergrowth in search of insects. The diapsids are the only eureptilian clade to continue beyond the Permian Period. Eureptilia is defined by the skull having greatly reduced supraoccipital, tabular, and supratemporal bones that are no longer in contact with the postorbital.
^Muller, J. and Reisz, R.R. (2006). "The phylogeny of early eureptiles: Comparing parsimony and Bayesian approaches in the investigation of a basal fossil clade." Systematic Biology, 55(3):503-511. doi:10.1080/10635150600755396