Dinoflagellate chromosomes represent a unique evolutionary experiment, as they exist in a permanently condensed, liquid crystalline state, are not packaged by histones, and contain genes organized into polycistronic arrays, with minimal transcriptional regulation. We analyze the 3D genome of {Breviolum minutum}, and find large topological domains without chromatin loops, demarcated by convergent gene array boundaries (``dinoTADs’’). Transcriptional inhibition degrades dinoTADs, implicating transcription-induced supercoiling as the primary topological force in dinoflagellates. Overall design: Hi-C libraries associated with the project