Upon extension, uniformly distributed weak seeds lead to a wider zone of extension (~500 km after 50% extension) made of numerous, discrete and synchronous basins. In both coupled and decoupled models, each seeds initially produce a set of conjugate normal faults. As extension proceeds, only a smaller number of normal faults remain active. The natural selection process is such that in the final configuration the basins are bounded by normal faults merging at the brittle-ductile transition. Overall, the lateral distribution of the stretching factor is rather homogeneous. This clearly contrasts with the wide extensional zone that results from a single weak seed in decoupled models. In the latter, progressively younger basins develop for the initial weak seed. Consequently, older basins accommodate a larger amount of extension and the stretching factor is heterogeneous over the length of the model.