Pelusios hyneki hyneki Široký & Fritz sp. et subsp. nov.

Hynek’s hinged terrapin

Pelusios subniger (partim), Fritz et al. (2013), TTWG (2017, 2021, 2025)

Holotype. National Museum Prague (NMP-P6 V 74976 /2), adult female in alcohol, vicinity of Luena (approx. -9.4409, 25.7894), Democratic Republic of the Congo, leg. Hynek Prokop, 2014 (Fig. 6).

Paratypes. National Museum Prague (NMP-P6 V 74975, NMP-P6 V 74976 /1), adult female and subadult of unknown sex; Museum of Zoology, Senckenberg Dresden (MTD 49501, MTD 49502), subadult of unknown sex and adult male, all same data as the holotype.

Diagnosis. A species closely related to Pelusios bechuanicus, P. upembae, and P. subniger sensu stricto. Pelusios hyneki sp. nov. resembles P. subniger sensu stricto and differs from P. bechuanicus and P. upembae in the presence of a characteristic constriction of the plastral hindlobe near the bridge region along the abdominal-femoral seam, resulting in an outwards curved contour of the femoral scutes and a pronounced incision between the femoral and anal scutes. Furthermore, P. hyneki sp. nov. differs from P. bechuanicus and P. upembae in the distinctly lighter plastral coloration with more or less extensive brownish suffusions that may cover much of the horn-colored or yellow plastron (completely or nearly completely black plastron in P. bechuanicus and P. upembae). Pelusios hyneki sp. nov. differs from P. bechuanicus also in the absence of a conspicuous symmetrical coarse and contrasting yellow head pattern. Pelusios hyneki sp. nov. differs from P. subniger sensu stricto in its diffuse brownish plastral pattern instead of a contrasting blotched pattern. The nominotypical subspecies Pelusios h. hyneki sp. et subsp. nov. differs from P. h. tanganyika subsp. nov. genetically both with respect to mitochondrial and nuclear DNA markers and in its allopatric distribution. A selection of diagnostic sites for the mitochondrial cyt b and ND4 genes is listed in Table 2.

Description of holotype. Adult female in alcohol, with oval carapacial outline. Plastral hindlobe indented at bridge (along abdominal-femoral seam), outer contour of femorals curved, resulting in an emarginated edge at the femoral-anal seam. Anal scutes deeply notched; notch with straight edges. All following values are maximum measurements in straight line: carapacial length 116 mm, carapacial width 89 mm, plastral length 115 mm, and shell height 45 mm. Length of the elongated diamond-shaped intergular scute 24 mm, separates the small triangular gular scutes completely. Midseam lengths of the remaining plastral scutes as follows: humerals— 13 mm, pectorals— 3 mm, abdominals— 34 mm, femorals— 27 mm, and anals— 15 mm. Color of carapace chestnut brown; basic color of plastron horn yellow with extensive pale brownish tinge mainly along the plastral seams.

Coloration in life and variation. According to life photographs of the types and additional turtles with the same locality data (Table S3), no significant differences can be discerned in comparison to the alcohol-preserved specimens. The skin of the head is uniform greyish, without fine darker mottling as frequently seen in P. subniger sensu stricto. The extent of the diffuse brownish plastral coloration varies. NMP-P6 V 74976 /1 has a mostly yellowish plastron with some diffuse dark pigment along the seams. In NMP-P6 V 74975, approximately one third of the plastron is covered by brownish suffusions, whereas MTD 49501 and the photograph of a not preserved life turtle have the most extensive dark plastral coloration, with more and larger darker suffusions than the holotype. Straight carapacial lengths of the type specimens and live individuals in the former collection of H. Prokop ranged between 82 and 134 mm (n =11); the two smallest individuals were immature. Adult males had straight carapacial lengths between 106 and 119 mm (n =3), adult females, 108 and 134 mm (n =6). This suggests that P. h. hyneki sp. et subsp. nov. is smaller than P. subniger sensu stricto, for which a maximum straight carapacial length of 200 mm has been reported (Branch 2008).

Distribution. Genetically confirmed records of P. h. hyneki sp. et subsp. nov. are presently only known from the type locality in the southeastern DRC. However, there are three iNaturalist records of similar turtles from central Zambia (Kasanka National Park and Mpongwe) that likely represent P. h. hyneki sp. et subsp. nov. as well, even though their collection sites are approximately 600 km away. This is also likely for the two photographic records of “ P. subniger ” with a diffuse plastral pattern in northern Botswana (Khwai [Kwaai] River and Ngamiland) and another photographic record from northeastern Zimbabwe (Fig. 8; Table S3).

Etymology. We dedicate the nominotypical subspecies to the late Hynek Prokop (1972–2023) who devoted much of his live to keeping and breeding Pelusios species. Only his unique live collection of long-term captives, sampled in 2012 and 2013, made the present study possible.