A relatively large-sized, lowland Leoptobrachella (males: 32– 38 mm, females 41–47 mm) in the subgenus Leptolalax. It occurs in the southwestern parts of Sarawak and most likely neighboring Kalimantan.  It has originally been described from Annah Rais, Padawan, Kuching Division, Sarawak. The known elevational range is below approximately 900 m a.s.l.

The  tibiotarsal articulation of limb at least reaches nostril level when adpressed along the body. L. marmorata differs from all the other congeners except for L. hamidi and L. picta by unique dorsal coloration, with large dark brown markings, light-edged, on a tan to light brown background of dorsum. The underside is devoid of dark markings, the belly mostly whitish. The white belly without markings separates L. marmoratus from L. dringi, L. sabahmontanus, L. maurus, L. gracilis, and  L. fritinniens, all of which have some ventral dark markings or a dark brown to black belly.

From the very similar L. hamidi, it differs in its larger body size, presence of discrete dark spots posterior to sacrum, and higher dominant frequency of advertisement call. It overlaps with L. picta in body size but differs by much more conspicuous, discrete dorsal markings, including a large dark marking on top of snout, and a higher dominant frequency of its advertisement call. 

The larvae have not been described but are most likely similar to other larvae in the subgenus, see L. gracilis, for example.