The Mesoproterozoic Atar Group, Taoudeni Basin, Mauritania, preserves a spectacular diversity of stromatolite morphologies, including stromatolitic biostromes comprised of the conical form Conophyton, the enigmatic branching conical form Jacutophyton, and a variety of irregularly branching forms, including Tilemsina and Baicalia. Until now, the peculiar juxtaposition of high and low-relief stromatolite morphologies has posed a conundrum for environmental interpretation of stromatolite forms, and has led to interpretations of strict biological control over stromatolite morphology. Careful assessment of superpositional relationships among stromatolite elements, however, suggests that the diversity of stromatolite morphologies in the Atar Group can be readily explained via parasequence-scale sea-level changes and the incomplete and laterally discontinuous filling of accommodation space. In the Atar Group, biostrome growth initiates during relative rises in sea level with the widespread, subtidal nucleation of Conophyton. Exposure of Conophyton to wave energy during falls in relative sea level result in disruption of stromatolitic laminae, generation of interstromatolitic debris, and development of both superimposed and laterally adjacent branching stromatolite forms. In this scenario, the enigmatic stromatolite form Jacutophyton represents stromatolite growth through a complete depositional parasequence, and the unusual juxtaposition of stromatolite forms reflects growth of different forms that is separated by time and depositional environment. With subsequent rises in sea level, nucleation of new Conophyton in subtidal regions, and continued growth of branching forms and aggradation of the depositional substrate in intertidal regions, results in continued modification of sea floor topography. In the model presented here, stratigraphic time is partitioned both vertically and laterally during biostrome growth, resulting in a complex internal architecture that is not readily discerned in outcrop. In 3 connecting hydrodynamic variables to stromatolite morphology, this model provides a more comprehensive understanding of Atar Group stromatolites in terms of basin geometry, relative sea level, and carbonate production.