When K.P. Schmidt (1919) described his Chamaeleon ituriensis (based on AMNH 11490, type locality Medje, Ituri Forest, D.R. Congo), it was “with considerable hesitation and only tentatively that Sternfeld's subspecies affinis of C. johnstoni is referred to the present form”. Schmidt (1919) pointed on differences in body stoutness and thickness of limbs of Sternfeld's female syntype (type locality “Urwald hinter den Randbergen am Nordwestufer des Tanganyika-Sees” = pristine forest behind the edge mountains on the northwestern bank of Lake Tanganyika) as compared with females collected by him (see his fig. 2 on plate XXXI) which is obvious when both figures are compared. He also noted that the canthus rostralis differed in its outline between both females, which is again comprehensible when comparing the two photographs (here combined in Fig. 1), even more distinct in the male holotype (AMNH 11490, Fig. 2). Obviously, Sternfeld's female type specimen (ZMB 22377) has been re-prepared (by alcohol injection?) because in its current shape it looks even stouter and more voluminous than on Sternfeld's (1912) original photograph (Fig. 3). According to Schmidt (1919), Sternfeld's second syntype, a juvenile male from another locality (Irumu-Mavambi Forest, situated in some distance southwest of Lake Tanganyika) fitted his males from Ituri better. It is, however, considered lost today in the ZMB collection (Bauer et al., 2006), thus giving ZMB 22377 a lectotype function. The synonymization of affinis Sternfeld, 1912 with ituriensis Schmidt, 1919 by the latter author was therefore termed questionable by Bauer et al. (2006).

In addition to his reservations synonymizing Sternfeld's (1912) name affinis with his C. ituriensis, Schmidt (1919) was well aware of the fact that C. j. affinis Sternfeld, 1912 is far antedated by the Ethiopian C. affinis Rüppell, 1845 so that ituriensis should be the valid name for the eastern Congolese species.

Loveridge (1942), possibly influenced by Sternfeld's (1912) original specific assignment of his subspecies affinis, regarded it again as a subspecies of Chamaeleon johnstoni Boulenger, 1901, irrespective of its most obvious and diagnostic characters differentiating it from johnstoni and leading to its re-elevation to species rank by Laurent (1952) and de Witte (1965, see also Klaver & Böhme, 1997): (1) much smaller body size, (2) reversed sexual dimorphism in size, (3) lack of rostral and preocular horns in males, (4) a white midventral line, and (5) several rows of distinctly enlarged flat tubercles along the body and 6) rows of conical tubercles on the sides of the throat (Tilbury, 2018).

A first morphology-based phylogenetic approach to chameleons by Klaver & Böhme (1986) based on lung and hemipenial characters lead to the resurrection of the genus-group name Trioceros Swainson, 1839 (type species C. owenii Gray, 1831) as a subgenus name for the African chameleons which are characterised by a peculiar lung septation pattern and the possession of annulated horns in representatives in each of its subgroups (Klaver & Böhme, 1986). This concept was widely accepted by subsequent authors (e.g. Nečas, 1994; Klaver & Böhme, 1997), meanwhile also as a full genus (Tilbury, 2010, 2018).

Trioceros ituriensis was long regarded as an endemic of the eastern Congo basin west of the Albertine Rift Valley, but has also been recorded from its eastern margin in Uganda; first from the Kibale Forest by Vonesh (1998) in an unpublished MSc thesis, which became publicly known only 16 years later by Tolley & Plumptre (2014; see also Tilbury, 2018). Six years earlier I had received photographs of a chameleon taken on 7 April 2008 in the Budongo Forest, Uganda showing a female of T. ituriensis which remained also unpublished until now. According to the photographer (Katja Rembold, pers. comm.) its body length was about 100 mm, and also the leaves of the bush or tree (Ficus exasperata) on which it is sitting have a mean length of 10 cm (Fig. 4A; E. Fischer, pers. comm.). The gular tubercle rows were particularly distinctly visible in this specimen in a threatening colour phase (Fig. 4B). At that time, it was the second record of the species from east of the Albertine Rift Valley. Tolley & Plumptre (2014, see also Spawls et al., 2018) recorded another find from western Uganda, viz. from the Bwamba or Semliki Forest, and very recently also Behangana & Hughes (2022), when summarizing the Ugandan localities of T. ituriensis, listed also the Budongo Forest as an ituriensis locality.

Considering the relatively small distance between these western Ugandan localities, one might assume that T. ituriensis is further distributed on the eastern side of the Albertine Rift Valley than believed so far, at least when suitable, i.e. forested, habitats are available. And in view of the obvious separation of the ituriensis populations west and east of the Albertine Rift Valley by this deep trench, a closer morphological and also molecular genetic examination as suggested by Tolley & Plumptre (2014) could dismantle phylogenetic differences: “This population should be investigated in a phylogenetic context” (Tilbury, 2010), as it was true for the geographically comparable case of the Kinyongia adolfifriderici complex (Hughes et al., 2017; Tilbury, 2018).

The synonymy list of Trioceros ituriensis (Schmidt, 1919) comprises two more species names which have also been regarded as synonyms by some authors with hesitation. In order to check this and to make it traceable, I document these based on their original descriptions and the respective type specimens.

Chamaeleo laevigularis Müller, 1926 was based on a single (subadult?) male (ZSM 139/1925) which was said to come from East London, South Africa. In the original description, its body and tail length was given with 48 and 60 mm. Hillenius (1963) re-measured it and gave 55 and 53 mm as the respective values, resulting in the same total length of 108 mm. A new re-measurement for this paper resulted in 53 and 52 mm, i.e. a little bit shorter total length of only 105 mm (M. Franzen, pers. comm.). Hillenius synonymized it with Chamaeleo johnstoni Boulenger, 1901, thus rendering the type locality wrong, because chameleons of the C. johnstoni group do not occur in South Africa. However, since it is a small hornless male, he finally suggested that it might be “still another race of hornless Chamaeleo johnstoni besides of ituriensis, of which the range is not yet known” (Hillenius, 1963).

Hillenius' (1963) synonymization with C. johnstoni was accepted by subsequent authors (e.g. Mertens, 1966; Klaver & Böhme, 1997) because at that time also ituriensis was still considered to be conspecific with the former. Synonymy with T. ituriensis was suggested by Tilbury (2010) who had re-examined the holotype in the Bavarian State Collection (ZSM) after Hillenius and “could find no significant differences from typical Trioceros ituriensis”. But because “the rediscovery of Ch. laevigularis is still pending, it seems expedient to leave this form as a synonym for Trioceros ituriensis”. This means a clear caveat.

The holotype of Müller's (1926) Ch. laevigatus is figured here (Fig. 5), but apart from an overall similarity at least one distinct difference in respect to an important key character of T. ituriensis can be seen: The gular region lacks any longitudinally arranged enlarged conical tubercles (Fig. 5A) as they are seen in Schmidt's (1919), and Witte's (1965) illustrations and also in the ZFMK specimens (Figs 6, 7) used by Tilbury (2010) for comparison, thus justifying Müller's denomination as laevigularis (Latin: smooth-throated). These gular rows of tubercles are typical for T. ituriensis and are well visible in the color photos in Tilbury (2010, 2018), Spawls et al. (2018), Behangana & Hughes (2022) and – particularly distinct – also in the living Budongo specimen shown in Fig. 4B.

In conclusion, both Hillenius (1963) and Tilbury (2010, 2018) were well advised to treat the synonymization of Chamaeleo laevigularis with some precaution.

The second name in question is Chamaeleo (Trioceros) tremperi Nečas, 1994, a nominal species from western Kenya which was accepted as valid in the checklist by Klaver & Böhme (1997). Nečas (1994) placed it already into close relationships to T. johnstoni and T. ituriensis and diagnosed it against these two species by its small size, a granular body and head scalation, the shape of the torus parasagittalis (new term by him: a bulge between the parietal and lateral crest) and an enlarged, pointed scale behind the eye on the temple (see Fig. 8).

Chamaeleo (T.) tremperi was synonymized with T. ituriensis by Tilbury (2010) who compared the Viennese syntypes with four “typical” specimens from the ZFMK collection and found “no significant or defining characteristics to separate them”. Moreover, he pointed on several subsequent searches around the Eldama Ravine/Maji Mazuri area in Kenya which failed to find more specimens. He concluded “since T. tremperi is essentially identical to ituriensis” that the Kenyan provenance would be most likely erroneous and that both names would consequently be synonyms, a view shared by Spawls et al. (2018).

There are, however, some problems connected with this conclusion. There are some discrepancies between the holotype description (which lacks any measurements) and the drawn head figure of the holotype in Nečas (1994) paper if compared with the specimen NMW 7880:1 itself (Fig. 8): The diagnostic enlarged, pointed scale behind the eye is much less prominent than in the drawing as are also the gular longitudinal rows of tubercles. Also, the “torus parasagittalis” is hardly discernible. The same is true for the description of longitudinal rows of enlarged flat tubercles along the sides of the body which are hardly distinguishable in the holotype specimen itself.

Very characteristic, in contrast, is the convex, beak-like snout tip which is very different from the rounded snout profile of the comparative ZFMK specimens (see Figs 6, 7). Here, the whole head shape looks very different from the true Congolese ituriensis where the profile of the canthus rostralis is clearly concave and the head much less high [see figs 2a, 6, 7 and fig. 23 in Schmidt (1919) and also fig. 40 in de Witte (1965)]. A different outline of the canthus rostralis was already observed by Schmidt (1919) between his Medje specimens and Sternfeld's (1912) type of his affinis (see Figs 1, 3). The prominent “torus parasagittalis” is absent in the upper view head drawings in Schmidt (1919) and de Witte (1965) and also in the ZFMK vouchers mentioned and figured above.

A last comment concerns the locality. The type series of T. tremperi was collected by Dr Grotte in 1904 and was sent to the Vienna museum together with a juvenile agamid lizard, collected at the same site. This agamid had a pattern of dark and light rings around its tail which is diagnostic for Agama lionotus, a species of the A. agama complex elevated to species rank by Böhme et al. (2005). The locality Eldama Ravine Station, southern Kenya (= Maji Mazuri, 200 km northwest of Nairobi) is situated within the distribution range of A. lionotus (Spawls et al., 2018), but far away from the ituriensis localities in Uganda or in the D.R. Congo.

My conclusion is therefore that T. tremperi might nonetheless be a valid member of the T. johnstoni-ituriensis complex, a relict of a former wider distribution of the group, which might be extinct today because a forest patch may have disappeared since 1904, or that it will be rediscovered in the future because it is always much more difficult to get proof for the absence of a species than for its presence. So, the rediscovery of the provenance of this little chameleon might also be pending, as already assumed for the likewise questionable provenance of Müller's (1926) C. laevigularis by Tilbury (2010, 2018).