A MORPHOLOGICAL STUDY OF STEJNEGER’S PITVIPER Trimeresurus stejnegeri (SERPENTES, VIPERIDAE, CROTALINAE), WITH THE DESCRIPTION OF A NEW SPECIES FROM THAILAND Patrick David, 1 Nicolas Vidal, 2 and Olivier S. G. Pauwels 3 Submitted August 30, 2001. The status of populations currently referred to the green pitviper Trimeresurus stejnegeri in the Indo- chinese Peninsula and Thailand is reevaluated on the basis of 30 morphological characters obtained from 152 preserved specimens of T. stejnegeri and related species. These data, in conjunction with observations on living and freshly collected specimens, reveal the existence of an undescribed species from eastern cen- tral Thailand, which is named here. Preliminary comparisons with various populations of T. stejnegeri from China and the Indochinese Peninsula and a taxonomic discussion are also provided. Key Words: Reptilia, Serpentes, Viperidae, Crotalinae, Trimeresurus , Trimeresurus stejnegeri, China, Thailand, Vietnam. The intricate and confusing systematics of the Asian bamboo pitvipers, comprising approximately 12 bright or grass-green species of the genus Trime- resurus Lacepède, 1804, has long been emphasized. In spite of several studies, entirely based on morpho- logical characters, by Stejneger (1927), Pope and Pope (1933), and Regenass and Kramer (1981), the systematics of this group still remains unresolved (David and Ineich, 1999). The main cause of confu- sion within this group is the large intraspecific varia- tion of some morphological characters, such as the number of ventrals and subcaudals, whereas other characters are relatively constant, such as the number of dorsal scale rows. Several characters are also re- lated to sex, such as the presence of ventrolateral stripes (Malhotra and Thorpe, 1996, 2000). Examination of living specimens and their off- spring from central eastern Thailand and Vietnam, al- lowed investigation of the coloration and pattern in life of these southern populations of Trimeresurus stejnegeri . This new material raised the possibility that several taxa were hidden under the specific epi- thet stejnegeri . In this paper, we present preliminary results of the morphological analyses of T. stejnegeri populations, with the description of a new species from Thailand. It must be emphasized that this paper is just a first step in a much wider study of the T. stejnegeri subgroup, the purpose of which is to un- derstand the specific and intraspecific systematics of this group. Detailed morphological variation of all populations of pitvipers currently known as Trimere- surus stejnegeri, compared with data provided by mtDNA analyses, will be presented in a forthcoming paper. MATERIAL AND METHODS This study is based on the examination of 152 specimens of T. stejnegeri sensu lato, listed in the Ap- pendix. These include 33 specimens (13 adults [9 males, 4 females] and 20 juveniles [14 males, 6 fe- males]) from Nakhon Ratchasima Province in central eastern Thailand. In our study of T. stejnegeri we used 30 morpho- metric, meristic and coloration characters, of which fourteen, which proved here to be diagnostic for sep- arating an undescribed species, are detailed below. Standard characters used by previous authors for Tri- meresurus species, especially by Pope and Pope (1933) and Regenass and Kramer (1981) were re- tained, along with other morphometrical and meristic characters not previously used by these authors, some 1026-2296/2001 /0803-0 205 © 2001 Folium Publishing Company Russian Journal of Herpetology Vol. 8, No. 3, 2001, pp. 205 – 222 1 Laboratoire des Reptiles et Amphibiens, Muséum National d’Histoire Naturelle, 25 rue Cuvier, F-75005 Paris, France. E-mail: pdavid@mnhn.fr 2 Service de Systématique Moléculaire, Muséum National d’His- toire Naturelle, 43 rue Cuvier, F-75005 Paris, France. E-mail: nvidal@mnhn.fr 3 Department of Recent Vertebrates, Institut Royal des Sciences Naturelles de Belgique, Rue Vautier 29, B-1000 Brussels, Bel- gium. E-mail: osgpauwels@hotmail.com