A study by CNAM members Prof. Ian Appelbaum and Dr. Pengke Li has been featured as an Editor's Suggestion in PRB. Applying group theoretic methods to study the unusual electronic structure of atomically-thin two-dimensional "four-six-ene" semiconductors such as tin sulfide, germanium telluride, etc, this work provides a straightforward framework for understanding the consequences of inversion symmetry breaking due to inequivalent sublattice atomic identity. In particular, the quantum states at the edge of the fundamental bandgap -- relevant to all transport, optoelectronic, and spintronic properties -- are shown to directly inherit their character from nearby points of high symmetry in the reciprocal lattice, where the form of allowable energetic interactions is constrained. This work is published in Physical Review B; more information can be found on Prof. Appelbaum's web site.