Abstract: Laccopithecus robustus gen. et sp. nov. from late Miocene formation of Lufeng Ra- mapiihecus site, is described in this paper.
Tre materials are as follows:
Holotype:
PA 876 A fragment of left maxilla with I*, P3-Ms and broken C', right maxilla with I1,I2, P3, M1 and broken C\ P4, M2. All belong to the same individual.
PA 880 A relatively complete mandible with all teeth except right C,.
Paratype:PA 878 A fragment of left maxilla with P3 — M1.
PA 877 An upper tooth row with left M： M3, broken C\ M1 and right I2, C’, M3.
PA 881 A fragment of left mandible with C―M2.
PA 879 A relatively complete right mandible with I1- M3.
In addition, 10 maxillae and mandibles, 8 tooth rows and about 60 isolated teeth, an incomplete skull are also assigned to this genus and species.
Diagnosis:
P4 is highly molarised. The canines show marked sexual dimorphism. The upper premolars are relatively large in sue. The upper molars are square in outline. M3 is rather large and its distal fovea enlarged postero-lingually. The mandibular body is rather high. The mandibular symphysis extends backward to the level of the posterior part of P3. Both the superior and inferior tori are well-developed.
Description:
Upper dentition
I1 is broad and spatular with moderate lingual cingulum. I2 is conical and canineform. The male C' is robust, very tall and sharp and has one mesial sulcus on the crown. Canines are strongly dimorphic in height and shape.
The upper premolars are relatively large and have weak lingual cingula. The upper molars are square in outline. is large with large distal fovea. The upper molars have weak or moderate lingua] cingula. M2 > M3 > M1.
Lower dentition. The incisors are mosio-distally short and highcrowned. They are similar to those of Dcndropithecus and Micro pith ecus. L has a distal prong and its distal lingual surface is concave. C, shows marked dimorpnism in size and height. P3 is compressed. P4 is highly molarised and its talon is long and broad. The lower molars present weak buccal ein^ula. M3 is longer than the preceding teeth. The connecting line from the protoconid to hypoconulid is practically straight in M3>M2>Mi，
The mandibular symphysis extends backward to the level of the posterior part of R.
Laccopithecns robust us of Lufeng is similar to European Pliopithecus in size and some morphological features. On the other hand, it also has features similar to Hylobates and Symphalangus, especially to the former. Therefore it is a link between the known Miocene and Pieistoeene-Recent forms and affords important fossil evidence for the origin of living gibbons.
Yunnan Province is one of the important habitats of extant gibbons. The discovery at Lufeng seems to indicate that the hylobatids had lived in their hometown of southwest China when Ramapithccus was living in Yunnan.

Key words: Laccopithecus robustus; Hylobatidae; Late Miocene; Lufeng