A case history in retrograde evolution: The onca lineage in anoline lizards. I. Anolis annectens new species, intermediate between the genera Anolis and Tropidodactylus

^-'' B R E V l.a.K A LIBRARY Miiseiiiii of Coiiiparative Zoology us ISSN 0006-96' Cambridge, Mass. 29 March ^^^^ygi^j^j^^^^^^ "^^^ A CASE HISTORY IN RETROGRADE EVOLUTION: THE ONCA LINEAGE IN ANOLINE LIZARDS. I. ANOLIS ANNECTENS NEW SPECIES, INTERMEDIATE BETWEEN THE GENERA ANOLIS AND TROPIDODACTYLUS. Ernest E. Williams Abstract. A new anole species bridges the gap between the genus Anolis, diagnosed by the presence of adhesive subdigital pads under phalanges ii and iii, and Tropidodactylus, diagnosed by the absence of such pads: Anolis annectens has typical anoline transverse lamellae with microscopic hairs and free distal margins only under phalanx ii; the third phalanx has only keeled infradigital scales as in the species onca currently referred to the monotypic genus Tropidodactylus. The genus Tropidodactylus is formally synonymized with Anolis. A morphological series in the reduction of the anoline adhesive pad that culminates in the condition seen in the species A. onca is described. The genus Tropidodactylus was erected in 1885 by Boulenger in the second volume of his classic Catalogue of the Lizards in the British Museum (Natural History) to receive the single species described as Norops onca by O'Shaughnessy in 1875. Neither the genus nor the species has received much atten-tion since their description. They have, up to the present, been very poorly known. The validity of the genus has not been ques-tioned, since the difference between Tropidodactylus and Anolis in the defining character of digital structure has seemed a sharp and important one: all Anolis (including all those species classi-cally referred to Norops) have under phalanges ii and iii ex-panded adhesive digital pads, the smooth, flattened, transverse lamellae of which are provided with microscopic hairs (Ruibal and Ernst, 1965; Killer, 1968; Maderson, 1970; Lillywhite and Maderson, 1 968 ) . The adhesive pad may be narrower or wider, may be sharply set off ("raised") from phalanx i or not so set