Trioceros is a genus of lizards in the family Chamaeleonidae, the chameleons, native to lowlands and highlands in the African mainland, ranging from Ethiopia south to Mozambique and west as far as Ghana. Trioceros was considered a subgenus of the genus Chamaeleo until 2009, when it was elevated to full genus level. (2009). "A re-appraisal of the systematics of the African genus Chamaeleo (Reptilia: Chamaeleonidae)". Zootaxa 2079: 57–68.
Trioceros vary greatly in appearance and size. Many species in the genus have various ornaments, such as one to four horns on the head, crests on the nape or throat, or spines or sail-like structures on the top of the back or tail. They are primarily found in adult males, but generally reduced or even absent in females, and there are also many species in the genus where both sexes lack conspicuous ornaments. Although horn-like structures are found in certain other chameleon genera, Trioceros is the only where it can be cylindrical, annulated and bony.
Trioceros contains species that lay eggs (similar to most other chameleon genera) and species that give birth to live young (similar to only Bradypodion). It is likely that giving birth to live young is an adaption to temperature, as it in Trioceros generally is found in species from highlands. The relatively cold highland climate slows the development of eggs laid in the ground; when instead retained inside the body until birth, a female can actively sun bask to increase the temperature.
Species The following species are recognized as being valid. Image Name Common name Subspecies DistributionTrioceros affinis beardless Ethiopian montane chameleon, Rüppell's desert chameleon Ethiopia.Trioceros balebicornutus Bale two-horned chameleon Ethiopia.Trioceros bitaeniatus side-striped chameleon, two-lined chameleon Ethiopia, southern Sudan, Somalia, Kenya, Tanzania, Uganda, and the northeastern Democratic Republic of the Congo.Trioceros camerunensis Cameroon dwarf chameleon Cameroon.Trioceros chapini Chapin's chameleon,Beolens et al., p. 51. grey chameleon Gabon and Democratic Republic of the Congo.Trioceros conirostratus South Sudanese unicorn chameleon South Sudan and Uganda.Trioceros cristatus crested chameleon, fringed chameleon Bioko, Equatorial Guinea, Cameroon, Central African Republic, Democratic Republic of the Congo, Republic of the Congo, Gabon, Nigeria, Ghana, and Togo.Trioceros deremensis Usambara giant three-horned chameleon, wavy chameleon East Usambara, Uluguru, Nguu and Nguru Mountains, and Udzungwa Mountains. Trioceros ellioti Elliot's chameleon,Beolens et al., p. 82. montane side-striped chameleon, Elliot's groove-throated chameleon Burundi, Kenya, South Sudan, Rwanda, Tanzania, Uganda, and Democratic Republic of the Congo.Trioceros feae Bioko hornless chameleon, Bioko montane chameleon, Fea's chameleon Bioko.Trioceros fuelleborni (named after Friedrich Fülleborn),Beolens et al., p.95. flapjack chameleon, Ngosi Volcano chameleon, Poroto three-horned chameleon, mountain three-horned chameleon TanzaniaTrioceros goetzei Goetze's chameleon,Beolens et al., p. 103. Ilolo chameleon, Goetze's whistling chameleonTrioceros goetzei goetzei – Goetze's whistling chameleon Trioceros goetzei nyikae – Nyika whistling chameleon Tanzania and Malawi.Trioceros hanangensis Mount Hanang montane dwarf chameleon, Mount Hanang chameleon TanzaniaTrioceros harennae Harenna hornless chameleonTrioceros harennae harennae – Harenna hornless chameleon Trioceros harennae fitchi – Fitch's Harenna hornless chameleonBeolens et al., p. 90.EthiopiaTrioceros hoehnelii helmeted chameleon, high-casqued chameleon, von Höhnel's chameleonBeolens et al., p. 124. Kenya and UgandaTrioceros incornutus Ukinga hornless chameleon TanzaniaTrioceros ituriensis Ituri forest chameleon Democratic Republic of the Congo and Kenya.Trioceros jacksonii Jackson's chameleonBeolens et al., p. 132.Trioceros jacksonii jacksonii – Jackson's three-horned chameleon Trioceros jacksonii merumontanus – dwarf Jackson's chameleon Trioceros jacksonii xantholophus – Mount Kenya three-horned chameleon, yellow-crested Jackson's chameleon south-central Kenya and northern Tanzania.Trioceros johnstoni Johnston's chameleon,Beolens et al., p. 135. Johnston's three-horned chameleon, Ruwenzori three-horned chameleon Democratic Republic of the Congo, Burundi, Rwanda, and UgandaTrioceros kinangopensis Aberdare Mountains dwarf chameleon Kenya.Trioceros kinetensis Mount Kineti montane dwarf chameleon, Mount Kineti chameleon South Sudan.Trioceros laterispinis spiny-flanked chameleon Tanzania.Trioceros marsabitensis Marsabit one-horned chameleon, Mt. Marsabit chameleon, Tilbury's chameleon Kenya.Trioceros melleri giant one-horned chameleon, Meller's chameleon,Beolens et al., p. 175. Meller's giant one-horned chameleon Malawi, northern Mozambique, and TanzaniaTrioceros montium Cameroon sailfin chameleon Cameroon.Trioceros narraioca Mount Kulal chameleon or Mount Kulal stump-nosed chameleon KenyaTrioceros ntunte Mount Nyiru chameleon, Nyiru montane dwarf chameleon KenyaTrioceros nyirit Mount Mtelo stump-nosed chameleon, Pokot chameleon KenyaTrioceros oweni Owen's chameleonBeolens et al., p. 198. Nigeria in the north, to Angola in the south, and Burundi in the eastTrioceros perreti Perret's chameleon,Beolens et al., p. 203. Perret's montane chameleon Cameroon.Trioceros pfefferi Pfeffer's two-horned chameleon,Beolens et al., p. 205, Pfeffer's chameleon, Bakossi two-horned chameleon Cameroon.Trioceros quadricornis four-horned chameleonTrioceros quadricornis quadricornis – southern four-horned chameleon Trioceros quadricornis eisentrauti – Rumpi Hills chameleon Trioceros quadricornis gracilior – northern four-horned chameleonwestern Cameroon and southeastern Nigeria. Trioceros rudis coarse chameleon, rough chameleon, Ruwenzori side-striped chameleon, Rwenzori bearded montane dwarf chameleon western Uganda, Rwanda, Burundi, and eastern DR CongoTrioceros schoutedeni Schouteden's montane dwarf chameleonBeolens et al., p. 237. Rwanda and Democratic Republic of the Congo.Trioceros schubotzi Mount Kenya montane dwarf chameleon, Mount Kenya side-striped chameleon, Schubotz's chameleonBeolens et al., p. 238. KenyaTrioceros serratus CameroonTrioceros sternfeldi (named after Richard Sternfeld),Beolens et al., 253. Crater Highlands side-striped chameleon, Tanzanian montane dwarf chameleon TanzaniaTrioceros tempeli Tanzania mountain chameleon, Tempel's chameleon,Beolens et al., p. 263. Udzungwa double-bearded chameleon TanzaniaTrioceros werneri Werner's chameleon,Beolens et al., p. 282. Wemer's chameleon, Wemer's three-horned chameleon TanzaniaTrioceros wiedersheimi Mount Lefo chameleon, Wiedersheim's chameleonBeolens et al., p. 285. Cameroon and NigeriaTrioceros wolfgangboehmei Ethiopia.
Nota bene: In the above list, a binomial authority or trinomial authority in parentheses indicates that the species or subspecies was originally described in a genus other than Trioceros.
Footnotes
References (2011). The Eponym Dictionary of Reptiles. Baltimore: Johns Hopkins University Press. xiii + 296 pp. . (1839). The Natural History of Fishes, Amphibians, & Reptiles, or Monocardian Animals. Vol. II. London: Longman, Orme, Brown, Green & Longmans; John Taylor. (A. Spottiswoode, printer). 452 pp. (Trioceros, new genus, p. 369).