The lyotropic mesomorphism and morphological properties of anew type of lyotropic liquid crystalline system, i.e. a tetranuclear platinum mesogen/apolar organic solvent, have been investigated. The texture transformations in a large temperature interval, especially in the phase transition regions have been studied. The temperature widths of the heterophase regions of the nematic-nematic and nematic-isotropic liquid phase transitions have been determined with a high accuracy. (C) 2002 Published by Elsevier Science B.V.