U/Ul 31^9 „OS. COMP. ZOOI„ LIBRARY OCCASIONAL PAPERS JAN 1 S 1982 ^ . , n 'N R V A R 3 or tne u.NiiveRSJTY MUSEUM OF NATURAL HISTORY The University of Kansas Law rence, Kansas NUMBER 97, PAGES 1-10 JANUARY 15, 1982 A NEW SPECIES OF TROPIDURUS (SAURIA, IGUANIDAE) FROM THE ARID CHACOAN AND WESTERN REGIONS OF ARGENTINA by Jose M. Cei^ The South American iguanid hzards of the genus Tropidurus foiTTi a widely ranging and diverse group of species, with repre-sentatives on l)oth sides of the Andes. Those species that occur mainly or entirely to the west of the Andes seem to fall into two distinct species groups. The peruviamis group (peruviamis, tigris, thoracicus, theresiae, theresoides, tarapacensis) is characterized by small, juxtaposed body scales (116-165 around midbody) and an inconspicuous, often discontinuous row of vertebral scales; the oc-cipitalis group (occipitalis, koepckeorum, stolznianni) is character-ized by large, keeled, imbricate body scales (48-106 at midbody) and a continuous row of enlarged vertebral scales ( Mertens, 1956; Donoso Barros, 1966; Dixon and Wright, 1975). The Galapagoan species are all similar to occipitalis and may be included in that group. East of the Andes this dichotomy appears to be represented by T. melanopJeurus and T. spimdosus. Tropidurus melanopleurus occurs along the eastern slopes of the Andes from extreme south-eastern Peru through Bolivia to extreme northwestern Argentina, and resembles the peruviamis group by having minute body scales (160-222 around midbody) and an inconspicuous and sometimes discontinuous vertebral scale row. Tropidurus spinulosus occurs at higher latitudes along the eastern Andean slopes, but extends east-ward into the arid lowlands of Bolivia, western Mato Grosso, and western Paraguay; it resembles the occipiialus group by having ' Departamento Ciencias Naturales, Universidad Nacional de Rio Cuarto, Prov. de Cord()l)a, Argentina. Personal address: Rancho Somuncura, Rua Fausto de Figueiredo, Birre-2750, Cascais, Portugal.