Garrdimalga was named by Shute et al. (2017) [A genus of megapode distinguished from all extant and extinct genera by unique morphology of the carpometacarpus and tibiotarsus as follows. Carpometacarpus (i) The processus extensorius (figure 20a,b,d) is short, dorsoventrally narrow (less than half the width of the adjacent trochlea carpalis), and proximally directed. (ii) The processus pisiformis is short, blunt, does not project over the extensor process, is placed relatively close to the proximal rim of the trochlea carpalis, and its caudal portion is highly protuberant (figure 20d). (iii) The ventral rim of the trochlea carpalis has little caudal prominence relative to the os metacarpale minus in dorsal view (figure 20b), and in caudal aspect is more or less aligned with the long axis of the os metacarpale majus (figure 20c). (iv) The distal margin of the articular facet of the trochlea carpalis is defined by the link between the caudal end of the dorsal rim and the distal end of the ventral rim, which traverses the caudal facies at a wide angle relative to the axis. Tibiotarsus (i) Just proximal of the epicondylus medialis and the condylus medialis, there is a cranial protuberance of the shaft (figure 20h). (ii) The pons supratendineus is placed proportionally further proximally than in all other taxa examined (i.e. there is no overlap of the pons and the condylus lateralis, and the pons is very constricted at its medial side, resulting in a very large distal opening of the canalis extensorius (figure 20e).].

It was assigned to Megapodiidae by Shute et al. (2017) and Worthy and Nguyen (2020).