While the leaf insects (Phylliidae) are a well-supported group within Phasmatodea, the genus Phyllium Illiger, 1798 has repeatedly been recovered as paraphyletic. Here, the Phyllium (Phyllium) celebicum species group is reviewed and its distinctiveness from the remaining Phylliini genera and subgenera in a phyloge- netic context based on morphological review and a phylogenetic analysis of three genes (nuclear gene 28S and mitochondrial genes COI and 16S) from most known and multiple undescribed species is shown. A new genus, Cryptophyllium gen. nov., is erected to partially accommodate the former members of the celebicum species group. Two species, Phyllium ericoriai Hennemann et al., 2009 and Phyllium bonifacioi Lit & Eusebio, 2014 morphologically and molecularly do not fall within this clade and are therefore left within Phyllium (Phyllium). The transfer of the remaining celebicum group members from Phyllium Illiger, 1798 to this new genus creates the following new combinations; Cryptophyllium athanysus (Westwood, 1859), comb. nov.; Cryptophyllium celebicum (de Haan, 1842), comb. nov.; Cryptophyllium chrisangi (Seow-Choen, 2017), comb. nov.; Cryptophyllium drunganum (Yang, 1995), comb. nov.; Cryptophyl- lium oyae (Cumming & Le Tirant, 2020), comb. nov.; Cryptophyllium parum (Liu, 1993), comb. nov.; Cryptophyllium rarum (Liu, 1993), comb. nov.; Cryptophyllium tibetense (Liu, 1993), comb. nov.; Crypto- phyllium westwoodii (Wood-Mason, 1875), comb. nov.; Cryptophyllium yapicum (Cumming & Teemsma, 2018), comb. nov.; and Cryptophyllium yunnanense (Liu, 1993), comb. nov.
The review of specimens belonging to this clade also revealed 13 undescribed species, which are described within as: Cryptophyllium animatum gen. et sp. nov. from Vietnam: Quang Nam Province; Cryptophyllium bankoi gen. et sp. nov. from Vietnam: Quang Ngai, Thua Thien Hue, Da Nang, Gia Lai, Quang Nam, and Dak Nong Provinces; Cryptophyllium bollensi gen. et sp. nov. from Vietnam: Ninh Thuan Province; Cryptophyllium daparo gen. et sp. nov. from China: Yunnan Province; Cryptophyllium echidna gen. et sp. nov. from Indonesia: Wangi-wangi Island; Cryptophyllium faulkneri gen. et sp. nov. from Vietnam: Quang Ngai and Lam Dong Provinces; Cryptophyllium icarus gen. et sp. nov. from Vi- etnam: Lam Dong and Dak Lak Provinces; Cryptophyllium khmer gen. et sp. nov. from Cambodia: Koh Kong and Siem Reap Provinces; Cryptophyllium limogesi gen. et sp. nov. from Vietnam: Lam Dong, Dak Lak, and Dak Nong Provinces; Cryptophyllium liyananae gen. et sp. nov. from China: Guangxi Province; Cryptophyllium nuichuaense gen. et sp. nov. from Vietnam: Ninh Thuan Province; Cryptophyllium phami gen. et sp. nov. from Vietnam: Dong Nai and Ninh Thuan Provinces; and Cryptophyllium wennae gen. et sp. nov. from China: Yunnan Province. All newly described species are morphologically described, il- lustrated, and molecularly compared to congenerics.
With the molecular results revealing cryptic taxa, it was found necessary for Cryptophyllium westwoo- dii (Wood-Mason, 1875), comb. nov. to have a neotype specimen designated to allow accurate differen- tiation from congenerics. To conclude, male and female dichotomous keys to species for the Cryptophyl- lium gen. nov. are presented.