The extremely rare Cameroon Chameleon, Trioceros camerunensis

01/12/2024

courtesy gecko_eb

courtesy Jurgen van Overbeke

courtesy gecko_eb

courtesy Jurgen van Overbeke

Trioceros camerunensis is one of the rarest chameleon species at all, it is almost unknown and only few museum specimens are known. It has also been depicted only few times, so almost no one knows how it looks in life, its biology remains a mystery.

It was described by Müller in 1909 as Chamaeleo camerunensis (Jb. nassau. Ver. Naturk. Wiesbaden 62: 111) from Dibongo bei Edea (Cameroon) and belongs nowadays to the genus Trioceros. It is a part of the Trioceros cristatus group, to which the following forms belong:

Trioceros camerunensis (Müller, 1909)
Trioceros cristatus (Stutchbury, 1837)
Trioceros eisentrauti (Mertens, 1968)
Trioceros feae (Boulenger, 1906)
Trioceros montium (Buchholz, 1874)
Trioceros perreti (Tornier, 1900)
Trioceros pfefferi (Tornier, 1900)
Trioceros quadricornis quadricornis (Tornier, 1899)
Trioceros quadricornis gracilior (Böhme & Klaver, 1981)
Trioceros serratus (Mertens, 1922)
Trioceros wiedersheimi (Nieden, 1910).

The species of the Trioceors cristatus group received relatively little attention in the past due to scarcity of collection material of the species such as Trioceros camerunensis, eisentrauti, pfefferi and due their limited distribution to relatively inaccessible locations in Cameroon and surrounding countries. Most of the species of this complex are only found in relict patches of montane rainforest confined to mountains or mountain ranges in the Cameroon-Nigerian hinterland and T. feae occurs in a similar habitat on the peaks of Fernando Poo (Bioko). Trioceros montium that has a (sub-)montane distribution on mountains nearest to the coast. Trioceros cristatus is a widespread lowland species, recorded from the lowland rainforest of Ghana, Togo, Nigeria, Cameroon, Equatorial Guinea (Mbini and Bioko), Gabon, Central African Republic and Congo. Trioceros camerunensis is a lowland species with a distribution limited to the coastal plains south of Mt Cameroon, reaching Congo. It is one of the rarest species of the group.

Description and further characteristics (updated after Klaver & Böhme (1992):

Head: Casque flat and only slightly raised posteriorly, pointed at the end; lateral crest weakly developed anteriorly of the point where the temporal crest meets, from this point to the extremity of the casque it is well developed and consists of triangular tubercles; triangle between anterior part of the lateral crest and the temporal crest covered with somewhat larger round convex scales; scales on top of the head and in the temporal region slightly enlarged and polygonal; gular scales somewhat larger than the scales on the body; no parietal crest, horns and gular crest.

Body: Body covered with small flat scales intermixed with numerous somewhat enlarged rotund flat scales, that sometimes form longitudinal rows on the upper part of the flanks; no dorsal and caudal keel, but dorsum and anterior part of the tail slightly crenulate in o', at the higher points of the dorsum (neural spines) a somewhat enlarged flat scale; the outer margin of the dorsum with a double row of scales; no ventral crest.

Dimensions: TL generally larger than HBL in both sexes; maximal dimensions: o', HBL/TI 90/106 (ZSM 488/1916); 9, HBL/TL 85/96 (SMF 16459).

Hemipenis: Truncus with small shallow calyces; four denticulated rotulae on the apex; near the base of each sulcal rotula a papillary field with up to 10 fleshy papillae

Lung morphology: A smooth muscle network covers the entire luminal surface of the lung. Four or five diverticula may be present. Two large septa of unequal size are connected with the lateral, medial and ventral wall of the lung. They subdivide the lumen in three successive chambers. The two posterior chambers terminate in a diverticulum, the remaining 2-3 diverticula are always attached to the most posterior chamber. A diaphragm and three small dorsal septa are present. A gular pouch is absent.

Status: Mertens (1964, 1966) classified T. camerunensis as a subspecies of T. montium, based on morphological similarities and zoogeographical affinity, but Klaver & Böhme (1992) reclassified the taxon as a valid species. Molecular data support close relationships between T. camerunensis and T. montium. According to Pook & Wild (1997), T. camerunensis is more closely related to T. feae than to T. montium.

Range: Plains south of Mt. Cameroon;

type locality: Cameroon: Dibongo near Edea

Cameroon: Isongo, Dehane, Metet, Sakbayeme, Bibundi

Congo: Baposo

Biotope: T. camerunensis inhabits the dense lowland forest areas near sea-level in the coastal plains of Cameroon and Congo.

IUCN Status: Least concern (a bit strage as assessed last in 2014 based on almost no data: https://www.iucnredlist.org/species/203822/2771661)

CITES: Appendix II

PICTURES: www.chameleons.info/en/trioceros-camerunensis3/

VIDEOS: https://youtu.be/1AdEIjjji9M?si=21aa_ZdqIN2y6JUz, https://youtu.be/nJWvKsb2pH0?si=ev4ns2Du2OaPhBSH

CAPTIVE DATA: Jurgen van Overbeke reported on successful offspring, so there is a hope on a report in near future, showing more light into the behavior and biology of this mysterious species.

courtesy Jurgen van Overbeke