Bettongia haoucharae, Newman-Martin & Travouillon & Warburton & Barham & Blyth, 2025

Bettongia haoucharae sp. nov.

The results of this investigation indicate that the taxon identified by Haouchar et al. (2016) is morphologically valid as the taxon is both genetically and morphologically distinct. We have chosen to give the taxon species status with the name Bettongia haoucharae . This taxon is clearly morphologically distinct from the Bettongia penicillata complex, which can be seen in the PCA analyses performed (Fig. 4,5,6,7,8, and 9), where B. haoucharae is more distant morphologically than Bettongia tropica and Bettongia gaimardi are from the rest of the complex. Initially, we suspected that individuals of B. haoucharae could represent Bettongia pusilla or Bettongia anhydra as both of these taxa are known from arid regions and are very cryptic. However, when comparing available specimens of B. pusilla (Supp. Fig. 1), including the type specimen (SAMA P35450), it was shown that the dp2 and dp3 of B. haoucharae are markedly larger than B. pusilla . Additionally, the molars are markedly smaller in B. pusilla . Similarly, B. anhydra was also compared with B. haoucharae , and the P3 of the latter is more buccally angled than the straight molars that are present in B. anhydra . Similary, B. haoucharae was also directly compared with Bettongia lesueur and specimens did not morphologically match.

Based on the available material, B. haoucharae was likely an arid adapted bettong that could be found throughout the Nullarbor and arid South Australia, through to the Great Victoria Desert until the border of the Gibson Desert. This means that it was a fairly wide-ranging Bettong that occupied the southwestern deserts of Western Australia and South Australia, in the habitats that were formerly believed to be occupied by an arid living Bettongia penicillata . Bettongia haoucharae is fairly abundant in Nullarbor cave deposits alongside Bettongia pusilla and Bettongia lesueur , indicating that it could live in sympatry with both species. No specimens are known from the Roe Plains or any other mesic environments in Western Australia, which could indicate that the species was specialised for arid environments and could not compete with other small potoroids in a mesic setting in Western Australia. However, the species is recorded as far east as Venus Bay in South Australia in the Haouchar et al. (2016) investigation. Whilst no photographs or skins of this taxa survive today, it is possible to speculate at its appearance. Based on the holotype specimen (WAM 75.12.21), and habitat information an artist’s rendition of the taxa in life was created (Fig. 35.)

According to features found on the forelimbs of the holotype of Bettongia haoucharae the species engaged in partial fossorial behaviours, similar to other Bettongia ( Baker et al. 2023) . This is based on the presence of a shorter and more robust humerus with an enlarged insertion of pectoralis superficialis muscle. Bettongia haoucharae , like other Bettongia , likely dug or foraged through the substrate for food. However, without an adult individual or more specimens for analysis, the authors are hesitant to comment on the fossorial abilities of the taxa compared to other Bettongia taxa. In other Bettongia , hypogeous mycorrhizal fungi make up the bulk of their diet ( Taylor, 1992; Nuske et al. 2018; Zosky et al. 2018; Mitchell et al. 2024). However, it is not known what food source was widely available for B. haoucharae in an arid setting. Although the diet of B. haoucharae is uncertain, it is likely to have been similar to B. lesueur in the region. Future studies could examine the holotype specimen for stomach contents or perform stable carbon and nitrogen isotope analysis on the dentition as well as dental microwear texture analysis. The hind limbs were adapted to saltatorial locomotion as in other macropodines; however, based on their morphology B. haoucharae may have spent more time in a quadrupedal gait due to the shorter proportional length of the limb bones in comparison to other Bettongia , as well as their robust muscle attachments.

FIGURE 35. Artist’s reconstruction of Bettongia haoucharae in life based on cranial elements, habitat data, and known morphology of related Bettongia taxa. Artwork by Eleanor “Nellie” Pease.

It is believed that “ B. penicillata ” of the Nullarbor, recognised here as B. haoucharae , went extinct sometime during the 1920s due to the spread of foxes in this region ( Richards & Short, 1996). This is a similar extinction window to other small mammalian fauna in the region, such as Perameles papillon (Travouillon & Phillips, 2018) and Dasycercus archeri ( Newman-Martin et al., 2023) which were both last seen alive on the Nullarbor in the 1920s.

The B. penicillata complex

Another hypothesis that was tested in this investigation was that Bettongia ogilbyi and Bettongia penicillata represent two distinct species. This proposal was based on: (i) Kangaroo Island specimens (which were identified as B. p. penicillata ) being genetically distinct from specimens in the southwest of Australia ( Haouchar et al. 2016), with Kangaroo Island specimens a 99.3% genetic match to B. penicillata from the mainland ( Haouchar et al. 2014);. (ii) if there is a valid distinct taxon present on the Nullarbor ( Bettongia haoucharae ), then the subspecies of B. penicillata are geographically separated, indicating that speciation could occur.

The results of this investigation confirmed that B. p. ogilbyi and B. p. penicillata are indeed morphologically distinct when compared using LDA and PCA (Fig. 4-9) with both cranial and dental characters seperating the taxa. Notably, B. penicillata was found to differ from B. ogilbyi in that; a frontal-squamosal suture contact is present contra to B. ogilbyi where a parietal-alisphenoid contact is present, the auditory bulla is larger and ovate, contra to B. ogilbyi where it is kidney shaped, P3 is more anteriorly angled towards the premaxilla, the P3 is intermittently more bulbous than B. ogilbyi , and there is no StC present on the M1. Many more differences can be observed between B. penicillata and B. ogilbyi cranially, dentally and postcranially, and these can be found in the systematics section. Non-allometry corrected PERMANOVAs demonstrated that the taxa are morphologically distinct ( Table 3, 7 & 11); with non-allometry corrected cranial test of just the B. penicillata complex, non-allometry corrected upper dental test for the B. penicillata complex, and allometry corrected lower dental test for the B. penicillata complex. Additional allometry corrected PERMANOVAs demonstrated that the taxa are morphologically distinct ( Table 4, 8 & 12); with allometry corrected cranial test of just the B. penicillata complex, allometry corrected upper dental test for the B. penicillata complex, and allometry corrected lower dental test for the B. penicillata complex. Referring to Fig. 2 in Haouchar et al. (2016), it can be seen that B. penicillata is more closely related genetically to Bettongia gaimardi , than to B. ogilbyi . Based on the results of this investigations, which show that B. penicillata and B. ogilbyi are morphologically very different and have many characters separating them, the authors propose that B. ogilbyi be elevated to full species status and should be referred to as Bettongia ogilbyi ogilbyi .