A new sigillarian megaspores species Sublagenicula echinata sp. nov., preserved in situ within a volcanic ash bed from the Early Permian (Asselian) Taiyuan Formation, Wuda Coalfield, Inner Mongolia is proposed. The species is distinguished by a circular to subtriangular amb, prominent trilete rays and a pyramidal subgula. The proximal-distal body bears a unique combination of laevigate, granulate, and echinate sculpture, with the echinate processes being mamillate at base and apically constricted. Analysis of the in situ megaspore population reveals a consistent range of intraspecific morphological variation, which is independent of developmental context of spores and found across the strobili. This discovery represents the first and youngest in-situ record of Sublagenicula, confirming its biological link to Sigillaria and significantly expanding the known paleogeographic distribution and diversity of this genus in the Permian of Cathaysia.