LIBERONAUTINAE, Cumberlidge & Daniels, 2022

Cumberlidge, Neil & Daniels, Savel R., 2022, A new multilocus phylogeny reveals overlooked diversity in African freshwater crabs (Brachyura: Potamoidea): a major revision with new higher taxa and genera, Zoological Journal of the Linnean Society 194 (4), pp. 1268-1311 : 1280-1282

LIBERONAUTINAE SUBFAM. NOV.

( FIGS 1A , 2 , 3, 7B; TABLES 1–3 )

Zoobank registration: urn:lsid:zoobank.org:act:89F59361-7EE0-4D1D-9795-8CC0D9EEB5C7

Diagnosis: Taxa of Liberonautinae are recognized by the presence of an intermediate tooth on the anterolateral margin in between the exorbital and epibranchial teeth.

Type genus: Liberonautes Bott, 1955 , gender masculine.

Etymology: Liberonautinae is derived from the genus name Liberonautes .

Genera included: Buea Cumberlidge, Mvogo Ndongo, Clark & Daniels, 2019 , Liberonautes Bott, 1955 , Louisea Cumberlidge, 1994 , Potamonemus Cumberlidge & Clark, 1992 and Sudanonautes Bott, 1955 .

Distribution: Liberonautinae is recorded from West and Central Africa (Cumberlidge, 1999; Fig. 7B ). The eight Liberonautes species are found in West Africa west of Ghana, in Senegal, Mali, Guinea, Guinea Bissau, Burkina Faso, Sierra Leone, Liberia and Cote d’Ivoire (Cumberlidge, 1999; Daniels et al., 2016). The 14 Sudanonautes species (Cumberlidge, 1999; Cumberlidge & Boyko, 2000; Mvogo Ndongo et al., 2017a; Cumberlidge et al., 2021) are found in West Africa, from Cote d’Ivoire to Nigeria, in Central Africa ( Cameroon, D.R. Congo, Gabon, Equatorial Guinea, Central African Republic, Republic of the Congo and Cabinda) and in East Africa ( South Sudan and northern Uganda). The distributional ranges of Liberonautes and Sudanonautes overlap in Ghana and Cote d’Ivoire, whereas the four Buea species ( Cumberlidge et al., 2019; Mvogo Ndongo et al., 2020) and Louisea ( Cumberlidge, 1994; Mvogo Ndongo et al., 2017c, 2019) are all endemic to Cameroon and the three Potamonemus species ( Cumberlidge & Clark, 1992; Cumberlidge, 1993; Mvogo Ndongo et al., 2021) are endemic to Nigeria and Cameroon.

Remarks: Liberonautinae diverged from Potamonautinae c. 30.14 Mya during the Eocene- Oligocene ( Fig.1 ). Within Liberonautinae , Liberonautes forms a well-supported clade ( Fig. 1A ) which split from the clade that includes Sudanonautes , Potamonemus , Buea and Louisea ( Fig. 1A ) c. 27.65 Mya during the Eocene-Oligocene. Liberonautes is endemic to West Africa west of Ghana and is morphologically and geographically distinct from the other Liberonautinae genera (Cumberlidge, 1999). Liberonautes can be distinguished from the other four genera by a G1 TA that is directed inwards ( Fig. 2A, B ), vs. a G1 TA that is directed outward in the other four genera ( Fig. 3A–L ). In addition, the G1 TA of Buea , Potamonemus and Sudanonautes is long (0.4 to 0.5 × the G1 SA length), curved and tapers to a pointed tip ( Fig. 3A–B, D–E, G–H ), vs. a G1 TA in Louisea that is of medium length (0.3 × the G1 SA length, Fig. 3J–K ), weakly S-shaped and tube-like with a rounded tip. Moreover, the G2 TA of Buea , Potamonemus and Sudanonautes is noticeably shortened and reduced to a short stub (0.1 × the G2 SA length, Fig. 3C, F, I ), vs. a G2 TA in Louisea , which is elongated and flagellum-like, TA/SA 0.64 ( Fig. 3K ). Finally, the third maxilliped exopod of Buea , Louisea and Potamonemus lacks a flagellum, vs. a third maxilliped exopod with a long flagellum in Sudanonautes ( Cumberlidge, 1993, 1994, 1999; Mvogo Ndongo et al., 2017b, c).

The molecular phylogeny presented here ( Fig. 1 ) agrees with the phylogeny of Wood et al. (2019), which recovered a well-supported clade shared by Buea , Liberonautes , Louisea , Potamonemus and Sudanonautes ( Fig. 1A ). Liberonautes ( Fig. 1A ) diverged from the the other four genera ( Fig. 1A ) c. 27.65 Mya during the Eocene-Oligocene. Louisea split from the Buea , Potamonemus and Sudanonautes clade c. 25.14 Mya during the Oligocene-Miocene ( Fig. 1A ), while Sudanonautes diverged from Buea and Potamonemus c. 19.12 Mya (during the Miocene), and Potamonemus diverged from Buea c. 17.09 Mya (also during the Miocene). Two of the endemic Cameroonian genera, Buea and Potamonemus , have a sister-group relationship represented by a lineage that split from Sudanonautes c. 17 Mya. Louisea , also endemic to Cameroon, represents the earliest lineage in this clade that evolved in long isolation from the other genera in this tribe for 25 Myr, and as a result it is distinguished by a cluster of distinct synapomorphies not observed in any other African taxa (Cumberlidge, 1999).

Figures

Figure 1. A, maximum clade credibility tree of the Afrotropical freshwater crab fauna based on four DNA loci with support values (posterior probabilities and bootstrap values of the ML analyses) with a geological timescale below the tree topology. Posterior probabilities> 0.95 pP (*above branch) and bootstrap values> 75% (* below branch) were regarded as statistically supported and are shown on the tree topology. Clade A, Liberonautinae, clade B, Potamonautinae, clade B1, Maritimonautini, clade B2, Erimetopini, clade B3, Potamonautini. B, detail of the maximum clade credibility tree of the Afrotropical freshwater crab fauna showing Clade B3 Potamonautini with the species included in the five genera within the tribe: Arcopotamonautes (B3[1]), Lirrangopotamonautes (B3[2]), Platythelphusa (B3[3]), Potamonautes s.s. (B3[4]) and Rotundopotamonautes (B3[5]).

Figure 3. Gonopods 1 and 2 of four genera in Liberonautinae. A–C, Buea asylos (Cumberlidge et al., 2019: fig. 7a, d; 8a); D–F, Potamonemus mambilorum (Cumberlidge et al., 2019: fig. 7b, e; 8b); G–I, Sudanonautes floweri; J–L, Louisea balssi (Mvogo Ndongo et al., 2018: fig. 5a–c, © Magnolia Press, reproduced with permission from the copyright holder). A, D, G, J, left G1 ventral view; B, E, H, K, left G1 dorsal view; C, F, I, L, left G2 ventral view. Scale bar: A, B, D, E, G, H, J, K = 2.0 mm, C, F, I, L = 1.8 mm.

Figure 7. Maps showing the distributional range of (A) Potamonautidae, (B) Liberonautinae.

Figure 2. Liberonautinae. Gonopods 1 and 2 of Liberonautes latidactylus, NMU9.V.2005B (CW 72, CL 47.2, CH 20.5, FW 19.3 mm) Guinea, West Africa. A, left G1 ventral view; (B) left G1 dorsal view; (C) left G2 ventral view. Scale bar: A, B = 2.8 mm, C = 1.8 mm.