The interpretation of the fossil material assigned to this genus is problematic, as even generic attributions have been unstable (see below). While Dryopithecus is regarded as a crown hominoid with close relevance to the African apes, Griphopithecus has been consistently grouped with stem hominoids. The material therefore indicates the range of hominoid locomotor anatomy in mid-Miocene Europe, rather than a specifically crown hominoid anatomy.
As long ago as 1856, Édouard Lartet described a humeral shaft lacking both epiphyses representing Dryopithecus fontani from St. Gaudens in France. Slightly more recently, Paidopithex rhenanus was described by Pohlig (1892, 1895) on the basis of an intact femur from Eppelsheim in Germany. Griphopithecus darwini (Abel, 1902), dated to c. 14–15 Ma, was named from a single lower molar (now one of four teeth and two postcranial fragments) from Middle Miocene deposits at Devínska Nová Ves, near Bratislava in Slovakia. A humerus and ulnar shaft from Kleinhadersdorf in Austria have also been referred to this genus by palaeontologist David R. Begun (2002), although Begun (1992) refers to them as Austriacopithecus and Szalay & Delson (1979) had referred them to Sivapithecus darwini. By far the largest number of finds of Dryopithecus come from Rudabanya in Hungary, and these include a distal humerus, proximal radial and ulnar fragments, a talar body, a fragmentary distal first metatarsal and several phalanges (Begun, 1992). Begun (2002) refers most of these to Dryopithecus brancoi.
According to Begun's (1992) analysis of these isolated bones, the Rudabanya finds (with the exception of some phalanges which he refers to a large pliopithecid, Anapithecus) and the St. Gaudens humerus are functionally consistent with each other. Their characters include a humeroulnar joint stabilized throughout a large range of flexion and extension, and a radioulnar joint with a wide range of pronation/supination, quite unlike the radioulnar joint of non-hominoids, which favours stability in a prone and semiflexed posture. The posterior convexity of the St. Gaudens humerus is attributed to resistance to bending moments in an extended elbow, and to extended and abducted glenohumeral postures. Talus, metatarsal, and pedal and manual phalanges are strongly suggestive of fore- and hindlimb suspension and suspensory locomotion. Begun (1992), however, regards the Klein Hadersdorf material as functionally mosaic, having only a few characteristic hominoid traits of the humeroulnar articulation, and suggesting only limited suspension, while showing signs of adaptation for motion primarily in the parasagittal plane. The radiohumeral articulation, however, suggests a greater mobility in pronation/supination and the bowed shaft and strong supinator crests suggest more powerful pronation/supination than in non-hominoids. The Epplesheim Paidopithex femur is lightly built, like that of hylobatids. Begun (1992) attributes the straight diaphysis and large size to "habitually suspended hindlimb postures" (p. 333) while a high neck-shaft angle may indicate habitually abducted hip postures. Overall similarities to Pliopithecus may indicate a similar habit, possibly suspensory quadrupedalism like that seen in the Howler monkey.
While the evidence of Dryopithecus from Rudabanya and St. Gaudens suggests a locomotor repertoire similar to that of D. laietanus, Begun (1992) suggests suspensory quadrupedalism was practised by both D. brancoi and the Epplesheim ape. Only one living great ape, the orangutan, has been observed to engage in suspensory quadrupedalism: neither the panins nor the gorillines exhibit this behaviour (Thorpe & Crompton, 2006). The absence of such gait in panins and gorillines might, however, be a simple statistical consequence of much more exclusive arboreality in Pongo.
The following cladogram illustrated the supposed evolutionary relations of Griphopithecus:
- Griphopithecus africanus Begun, 1987
- Griphopithecus alpani Tekkaya, 1974
- Griphopithecus darwini Abel, 1902
- Begun, D. R. (3 May 2001). "African and Eurasian hominoids and the origins of the Hominidae". In de Bonis, Louis; Koufos, George D.; Andrews, Peter. Hominoid Evolution and Climatic Change in Europe: Volume 2: Phylogeny of the Neogene Hominoid Primates of Eurasia. Cambridge University Press. pp. 231–253. ISBN 0521660750.
- King; Aiello; Andrews (1999). "Dental microwear of Griphopithecus alpani". Journal of Human Evolution. 36 (1): 3–31. doi:10.1006/jhev.1998.0258.
- Kordos (2000). "New results of Hominoid research in the Carpathian Basin". Acta Biologica Szegediensis. 44 (1-4): 71–74.