[1,2,4]. In addition, Haile-Selassie ([10]: 345) suggested that some of the largest specimens of *Ny. tulotos* at Lothagam, from Upper Nawata and the Apak Member of the Nachukui Formation, could in fact belong to *Ny. australis*. Such restriction of the hypodigm of *Ny. tulotos* would be in favor of a greater distinction between this species and *Ny. khinzir*.

Within late specimens of *Ny. tulotos*, the most complete specimen, male cranium STD-VP-1/1 from Adu-Asa, differs in some noticeable aspects from the male cranium KNM-LT 316 from the Lower Nawata, possibly somewhat affected by postmortem distortion of both specimens. These differences bear essentially on dimorphic characters (notably expansion of zygomatic arches). They could be linked to the biological age and the sexual status of these specimens, KNM-LT 316 being an aged hypermale and STD-VP-1/1 a young adult. We observed such differences in extant species of suids, and they do not necessarily document any evolutionary trend or interspecific differentiation relevant to distinguish *Ny. khinzir* from 'late' *Ny. tulotos*.

The difference between *Ny. khinzir* on the one hand, and *Ny. australis* and *Ny. kanamensis* on the other hand, is notably expressed by the two latter species being larger, having third molars longer and much higher-crowned, generally lacking p1, and having proportionally smaller premolars. The difference between *Ny. australis* and *Ny. kanamensis* is much less conspicuous, and some authors propose alternately a placement of the material from Langebaanweg within *Ny. kanamensis* as a subspecies, *Ny. kanamensis australis* [1,15,38]. The Langebaanweg nyanzachoere has now been identified in deposits of Lothagam [17] and the Middle Awash research area [10] roughly contemporaneous to those of Langebaanweg.

Our observations confirm the initial diagnosis proposed by Cooke and Hendey [15], *Ny. australis* differing from *Ny. kanamensis* by: longer canine-second premolar diastemata; the consistent retention of P1; and overall larger tooth dimensions. In addition, *Ny. australis* has markedly more elongate p2 (Table S3). In the hypodigm of *Ny. kanamensis*, only specimens from the Ibole Member of the Wembere-Manonga Formation display similar dimensions [39]. When excluding these specimens, the difference is more pronounced, *Ny. kanamensis* displaying ranges of 7.0 mm–10.8 mm (x̄ = 8.6 mm, N = 13) for p2 length and of 67.7–109.6 (x̄ = 89.5, N = 13) for p2 width/length ratio (see Tables 4 and S3 for comparison). On the contrary, we did not observe marked differences of premolar size relative to molar size between *Ny. australis* and *Ny. kanamensis*.

The absence of a median conulid between the third pair of cuspidids and the distoconid of m3 is viewed by Haile-Selassie [10] as a strong diagnostic feature of *Ny. australis*. First, in *Ny. kanamensis*, this conulid is absent not only from some Hadar specimens [10], but also from half a dozen Kanapoi specimens, including KNM-KP 239. Second, it is observed, sometimes unilaterally, in some specimens of *Ny. australis*: at Langebaanweg, on SAM-PQL 11889, SAM-PQL 14431, and SAM-PQL 20490; in the Kuseralee Member of the Sagantole Formation, on AMW-VP-1/21, KUS-VP-1/67, KUS-VP-1/102, as well as on AMW-VP-1/37, attributed to *Ny. cf. kanamensis* by Haile-Selassie [10] on the basis of the presence of the conulid. The occurrence of this conulid seems thus to display some degree of variation, being accounted as rare in *Ny. australis* whereas frequent in *Ny. kanamensis*.

Given these morphological differences, given that *Ny. australis* encompasses the entire distribution range of *Ny. kanamensis*, and given that it predates the first occurrence of *Ny. kanamensis* "sensu stricto" in the Middle Awash deposits ([10]: 358), we are in favor of the specific differentiation of *Ny. australis* and *Ny. kanamensis*.

We further note that the material from the older deposits at Manonga Valley could possibly be better accommodated within *Ny. australis*, in good agreement with the relative large dimensions of the Manonga specimens as well as with the proposed temporal range of the Ibole Member [56].

The specimens found in south TM and attributed to *Ny. cf. australis* are homogeneously more advanced than *Ny. khinzir*, notably in their third molar complexity, hypsodonty, and premolar/molar ratios. Given the lack of more complete specimen, notably cranial, we viewed the attribution of this material to *Ny. australis* as likely but not certain, because it bears mostly on the development of the p2 evidenced only by alveoli or broken roots. Our recognition of this taxon in Chad is therefore provisional.

*Nyanzachoerus devauxi* is generally considered as the smallest species of the genus, with the simpler and shorter third molars (see, e.g. [10,17,31]). Unlike in the Oued el Hammam Valley where the holotype was found isolated [11], the presence of *Ny. devauxi* concurs with that of *Ny. syrticus* at Sahabi, and with that of *Ny. tulotos* at Lothagam and in the Adu-Asa Formation. At TM, no third molar combines the small size and the low CS observed in *Ny. devauxi*, and the overlap with *Ny. khinzir* is negligible. It is more complicated to discriminate with certainty large third molars of *Ny. devauxi* from small ones of *Ny. tulotos*, as they display quite similar morphological ranges (Fig. 6C, D). Similarly, premolars cannot be easily discriminated (Tables 3–6, Fig. 7). In contrast, the proportions of m1 relative to m3 and dental row relative lengths (Fig. 7B and Table 2) distinguish the species, so species determinations based only on isolated teeth may need further scrutiny. This is the case for the Adu-Asa Formation, where *Ny. devauxi* is represented by isolated unerupted molars and by a relatively small distal portion of a M3, ASK-VP-3/115, with a CS of 1.2 [10]. The distocone of this specimen has a height of 18.2 mm, i.e. much higher than other specimens of *Ny. devauxi* (Table 7), and could be well accommodated within *Ny. tulotos*. If the presence of *Ny. devauxi* in the Adu-Asa was to be revised on these grounds, the only well-dated occurrence of the species would be the Nawata Formation. To complicate the matter, it is to be noted that the holotype mandible was reported lost ([57]: 72) and recent efforts accomplished to find it did not succeed.

Although not documented by abundant material, *Ny. waylandi* is clearly distinct from *Ny. khinzir* in its flatter symphysis [10,37], its absolutely smaller premolars (Tables 4–6), its lower premolars relatively narrower (Table S3), and its m3 short but on average relatively as narrow as in *Ny. australis* and *Ny. kanamensis* (Table 8). In the Kuseralee Member of the Sagantole Formation, *Ny. waylandi* co-occurs with *Ny. kuseralensis*. Haile-Selassie, 2009 [10]. This species was principally distinguished from other species of *Nyanzachoerus* by its smaller size, its buccolingually compressed p3, its robust but shallow mandibular corpus, its higher premolar/molar ratio, its small m3 with two pairs of pillars, and its lack of p1 and p2 [10].

On the basis of our measurements, the holotype specimen of *Ny. kuseralensis*, KUS-VP-1/15, presents a small absolute size (Md5 = 123 mm, Table 2) not different from the range of *Ny. devauxi* and falling close to the same measurement in another specimen from the Kuseralee Member, AMW-VP-1/71 (Md5 = 139 mm, Table 2), attributed to *Ny. waylandi* by Haile-Selassie [10]. The p3 absolute dimensions and width/length ratio of KUS-VP-1/15 fall exactly within the ranges of *Ny. waylandi* (Tables 5 and S3). Corpus height at p2–p3 and corpus width across m1 are 49 mm and 39 mm respectively, not departing much from the values of AMW-VP-1/71 (ca. 52 mm and 36 mm respectively), both falling close to the lowest dimensions observed
on specimens of Lower Nawata *Ny. tulotos* and Kanapoi *Ny. kanamensis*. We failed to find the premolar/molar ratio for KUS-VP-1/15 higher than those of all other species of *Nyanzachoerus*. On the contrary, its ratios tend to be similar to those of *Ny. kanamensis*, *Ny. australis*, and the high values observed for *Ny. khinzir* (see, e.g., Fig. 7C–D). The m3 of KUS-VP-1/15 present a talonid development also encountered in *Ny. khinzir* and correspond to a CS of 2.25 (Fig. 5M). Given the high degree of variation of the m3 talonid in extant *Potamochoerus* and in *Nyanzachoerus*, this morphology should not be considered incompatible with that observed in *Ny. waylandi* from the Kuseralee Member, with CS of 2.0 and 2.5 for AMW-VP-1/7 and AMW-VP-1/71, respectively.

We failed to find any significant departure in measurements and dental ratios of the specimens attributed to *Ny. waylandi* and *Ny. kuseralensis* in the Kuseralee Member (see, e.g., Fig. 7B). A single feature seemed to differ radically between AMW-VP-1/71 and KUS-VP-1/15: the complete lack of p2 in the latter. In the extant sample of *Potamochoerus* we observed, the presence of p2 is variable: out of 48 specimens of *P. porcus*, it was absent bilaterally in one case, and twice unilaterally; out of 76 specimens of *P. larvatus*, it was absent bilaterally in no less than 12 specimens, and unilaterally in seven. Similarly, in *Ny. khinzir*, we found no p2 alveoli in two specimens, including above discussed TM 170-01-019. Given the variations observed in extant species, it seems more cautious to not consider the presence/absence of the reduced mesial premolars of *Nyanzachoerus* as an absolutely diagnostic feature, other than referring to frequency differences based on relatively large samples. We therefore failed to distinguish KUS-VP-1/15 from *Ny. waylandi*, and therefore consider *Ny. kuseralensis* as a junior synonym of the latter.

Finally, *Ny. khinzir* markedly differs from *Ny. jaegeri*, which is larger and has significantly higher-crowned, longer and more complex third molars, proportionally smaller premolars, and a more sexually dimorphic craniomandibular morphology reminiscent of more derived African tetracnodonts (see notably [4,8,14,17]). The generic attribution of *Ny. jaegeri* is currently debated, with a proposal to attribute this species to *Notochoerus* ([34]; but see [58]).

## Paleoecology of *Nyanzachoerus khinzir* nov. sp.

*Nyanzachoerus khinzir* is morphologically close to *Ny. tulotos* of eastern Africa [10,14,17,42]. Their dental morphological proximity implies that these species may have been ecologically similar. Carbon stable isotope results from TM 266-TM 267 support this view, indicating a diversified diet including a mixture of C₃ and C₄ plants (Fig. 8, Table S6) as for *Ny. tulotos* from the Turkana Basin [51,59,60]. Although TM *Nyanzachoerus* displays an average diet slightly more C₃-enriched than *Ny. devauxi* and *Ny. tulotos* and much more C₃-enriched than other specimens of *Nyanzachoerus* from the Turkana Basin, some TM individuals had a diet quite rich in C₄ plants (being most generally grasses). It can be noted that no sample of *Nyanzachoerus* displays a range of variation similar to what is observed for extant *Potamochoerus* (Fig. 8). This could be interpreted as an indication of more constant food preferences than in *Potamochoerus*, but it may also reflect a poor representation of populations that lived in closed habitats in late Miocene–early Pliocene sites.

TM *Nyanzachoerus* has low values of δ¹⁸O within the TM fauna: between -9.0 ‰ and 0.5 ‰, with a mean value of -3.7 ‰ for 27 specimens (Table S6). They match only those of local hippopotamids and anthracotheriids [21]. The average values are much lower than those obtained for *Nyanzachoerus* from the Turkana Basin, ranging from -4.9 ‰ to 1.4 ‰ with a mean of -

<figure><img src="image_12.png" /><figcaption>**Figure 8.** δ¹³C values (in ‰) for *Nyanzachoerus* from TM and from the Turkana Basin. TM data are from TM 266 and TM 267. Extant comparative data (*Potamochoerus*) are from [51]. Data for eastern African *Nyanzachoerus* are from [51,59,60]. doi:10.1371/journal.pone.0103221.g008</figcaption></figure>

1.3 ‰ for 24 specimens (data compiled from [51,59]). This possibly indicates that *Nyanzachoerus* was particularly dependent on wet habitats at TM 266-TM 267.

Therefore, the occurrence of *Nyanzachoerus* at TM differed from that at Lothagam in diversity (only one species at TM, two to three in the Nawata Formation [17]) as well as in stable isotopic data. This may be linked to different environmental settings: the Lothagam ecosystem was identified as a dwarf shrubland [59] whereas that of TM was previously described as analogous to the Okavango Delta in central Kalahari, Botswana [61].

## Paleobiogeographical implications

Previous interpretations of the suid material from Sahabi and TM [19,31] suggested a wide distribution of the late Miocene *Ny. syrticus* encompassing northern, central, and eastern Africa. Our findings suggest a more fragmented geographical distribution for species of *Nyanzachoerus* during this time interval: *Nyanzachoerus khinzir* is so far known only from the TM localities in central Africa; *Ny. tulotos* is so far known only from eastern Africa (Fig. 9).

The ‘anthracotheriid unit’ further differs from other localities of roughly this antiquity in lacking the small *Ny. devauxi*, found in northern Africa [11,31,33] and eastern Africa [10,17]. Other TM taxa previously indicated a faunal provincialism of the Lake Chad Basin with regard to eastern Africa (e.g., anthracotheriids, hippopotamids, bovids, birds, carnivores, fishes, see [20,23,24,62–64] respectively), as well as stronger affinities with the Sirte Basin in Libya, and beyond with Eurasia. The specific distribution of *Nyanzachoerus* is therefore congruent with a
on specimens of Lower Nawata *Ny. tulotos* and Kanapoi *Ny. kanamensis*. We failed to find the premolar/molar ratio for KUS-VP-1/15 higher than those of all other species of *Nyanzachoerus*. On the contrary, its ratios tend to be similar to those of *Ny. kanamensis*, *Ny. australis*, and the high values observed for *Ny. khinzir* (see, e.g., Fig. 7C–D). The m3 of KUS-VP-1/15 present a talonid development also encountered in *Ny. khinzir* and correspond to a CS of 2.25 (Fig. 5M). Given the high degree of variation of the m3 talonid in extant *Potamochoerus* and in *Nyanzachoerus*, this morphology should not be considered incompatible with that observed in *Ny. waylandi* from the Kuseralee Member, with CS of 2.0 and 2.5 for AMW-VP-1/7 and AMW-VP-1/71, respectively.

We failed to find any significant departure in measurements and dental ratios of the specimens attributed to *Ny. waylandi* and *Ny. kuseralensis* in the Kuseralee Member (see, e.g., Fig. 7B). A single feature seemed to differ radically between AMW-VP-1/71 and KUS-VP-1/15: the complete lack of p2 in the latter. In the extant sample of *Potamochoerus* we observed, the presence of p2 is variable: out of 48 specimens of *P. porcus*, it was absent bilaterally in one case, and twice unilaterally; out of 76 specimens of *P. larvatus*, it was absent bilaterally in no less than 12 specimens, and unilaterally in seven. Similarly, in *Ny. khinzir*, we found no p2 alveoli in two specimens, including above discussed TM 170-01-019. Given the variations observed in extant species, it seems more cautious to not consider the presence/absence of the reduced mesial premolars of *Nyanzachoerus* as an absolutely diagnostic feature, other than referring to frequency differences based on relatively large samples. We therefore failed to distinguish KUS-VP-1/15 from *Ny. waylandi*, and therefore consider *Ny. kuseralensis* as a junior synonym of the latter.

Finally, *Ny. khinzir* markedly differs from *Ny. jaegeri*, which is larger and has significantly higher-crowned, longer and more complex third molars, proportionally smaller premolars, and a more sexually dimorphic craniomandibular morphology reminiscent of more derived African tetracnodonts (see notably [4,8,14,17]). The generic attribution of *Ny. jaegeri* is currently debated, with a proposal to attribute this species to *Notochoerus* ([34]; but see [58]).

## Paleoecology of *Nyanzachoerus khinzir* nov. sp.

*Nyanzachoerus khinzir* is morphologically close to *Ny. tulotos* of eastern Africa [10,14,17,42]. Their dental morphological proximity implies that these species may have been ecologically similar. Carbon stable isotope results from TM 266-TM 267 support this view, indicating a diversified diet including a mixture of C₃ and C₄ plants (Fig. 8, Table S6) as for *Ny. tulotos* from the Turkana Basin [51,59,60]. Although TM *Nyanzachoerus* displays an average diet slightly more C₃-enriched than *Ny. devauxi* and *Ny. tulotos* and much more C₃-enriched than other specimens of *Nyanzachoerus* from the Turkana Basin, some TM individuals had a diet quite rich in C₄ plants (being most generally grasses). It can be noted that no sample of *Nyanzachoerus* displays a range of variation similar to what is observed for extant *Potamochoerus* (Fig. 8). This could be interpreted as an indication of more constant food preferences than in *Potamochoerus*, but it may also reflect a poor representation of populations that lived in closed habitats in late Miocene–early Pliocene sites.

TM *Nyanzachoerus* has low values of δ¹⁸O within the TM fauna: between -9.0 ‰ and 0.5 ‰, with a mean value of -3.7 ‰ for 27 specimens (Table S6). They match only those of local hippopotamids and anthracotheriids [21]. The average values are much lower than those obtained for *Nyanzachoerus* from the Turkana Basin, ranging from -4.9 ‰ to 1.4 ‰ with a mean of -

<figure><img src="image_11.png" /><figcaption>**Figure 8.** δ¹³C values (in ‰) for *Nyanzachoerus* from TM and from the Turkana Basin. TM data are from TM 266 and TM 267. Extant comparative data (*Potamochoerus*) are from [51]. Data for eastern African *Nyanzachoerus* are from [51,59,60]. doi:10.1371/journal.pone.0103221.g008</figcaption></figure>

1.3 ‰ for 24 specimens (data compiled from [51,59]). This possibly indicates that *Nyanzachoerus* was particularly dependent on wet habitats at TM 266-TM 267.

Therefore, the occurrence of *Nyanzachoerus* at TM differed from that at Lothagam in diversity (only one species at TM, two to three in the Nawata Formation [17]) as well as in stable isotopic data. This may be linked to different environmental settings: the Lothagam ecosystem was identified as a dwarf shrubland [59] whereas that of TM was previously described as analogous to the Okavango Delta in central Kalahari, Botswana [61].

## Paleobiogeographical implications

Previous interpretations of the suid material from Sahabi and TM [19,31] suggested a wide distribution of the late Miocene *Ny. syrticus* encompassing northern, central, and eastern Africa. Our findings suggest a more fragmented geographical distribution for species of *Nyanzachoerus* during this time interval: *Nyanzachoerus khinzir* is so far known only from the TM localities in central Africa; *Ny. tulotos* is so far known only from eastern Africa (Fig. 9).

The ‘anthracotheriid unit’ further differs from other localities of roughly this antiquity in lacking the small *Ny. devauxi*, found in northern Africa [11,31,33] and eastern Africa [10,17]. Other TM taxa previously indicated a faunal provincialism of the Lake Chad Basin with regard to eastern Africa (e.g., anthracotheriids, hippopotamids, bovids, birds, carnivores, fishes, see [20,23,24,62–64] respectively), as well as stronger affinities with the Sirte Basin in Libya, and beyond with Eurasia. The specific distribution of *Nyanzachoerus* is therefore congruent with a
<figure><img src="image_13.png" /><figcaption>**Figure 9.** Geographical and temporal distribution of the main sites and species of *Nyanzachoerus* compared with *Ny. khinzir* nov. sp.
Abbreviated sites are: TM, Toros-Ménalla; south TM, south Toros-Ménalla; KB, Kossom Bougoudi; Kus., Kuseralee Member of the Sagantole Formation; Lower Naw., Lower Member of the Nawata Formation; Upper Naw., Upper Member of the Nawata Formation; Ibole, Ibole Member of the Wembere-Manonga Formation. Vertical bars represent site temporal range: light tone, biochronologically dated ranges; dark tone, geochronologically dated ranges; discontinuous outline, uncertain ranges. Biochronological range for TM is from [19], geochronological ranges for TM and Kossom Bougoudi are from [29].
doi:10.1371/journal.pone.0103221.g009</figcaption></figure>

biogeographical distinction between central Africa and eastern Africa. The biogeographical affinities of the late Miocene *Nyanzachoerus* from northern Africa are more uncertain because of limited samples, fragmentary preservation, and stratigraphic uncertainties.

## Biochronological implications

Together with other taxa, the tetraconodont material of TM was initially used to correlate the 'anthracotheriid unit' to the Lower Member of the Nawata Formation at Lothagam [19]. This was done on a limited sample confined to locality TM 266 and since then has been considerably augmented for a variety of mammalian taxa. The present work led us to recognize that this suid assemblage is instead attributable to a new species not yet found in other African sites, and therefore not supportive of previous correlation. Currently, it is therefore not possible to propose a biochronological correlation of TM on the basis of this suid material. The previous biochronological correlation proposed by Vignaud et al. ([19]: 154) between the 'anthracotheriid unit' and the Lower Nawata deposits remains supported by other faunal elements (prominently the proboscideans), the age of TM being based on this correlation and on the radiochronological dates proposed by Lebatard et al. [29,30]. The temporal placements of *Nyanzachoerus* from TM and other important Mio-Pliocene sites are summarized in Figure 9.

Within the 'anthracotheriid unit', locality TM 9 is somewhat different from other localities bearing *Ny. khinzir* because of specimen TM 9-01-019. This specimen could come from an unusual individual, which presence is not unexpected in such a large sample. Alternately, it could be indicative of an environmental and/or chronological difference between TM 9 and other localities. TM 9 is further particular because it is the richest TM locality with so few *Libycosaurus* (less than 1% of ca. 800 collected specimens). A chronological lag between TM 9 and other TM localities would probably involve limited time, because TM 9

otherwise differs clearly from Chadian fossiliferous areas with later deposits including more advanced tetraconodonts and different suid associations, namely Kossom Bougoudi in the upper-most Miocene [65,66] and Kollé in the lower Pliocene [67].

A subset of TM localities (south TM) bears a different, more advanced tetraconodont, provisionally recognized as *Ny. cf. australis*. According to the First Appearance Datum proposed for *Ny. australis* by Haile-Selassie [10] using the record of the Middle Awash research area in Ethiopia, this could indicate that these Chadian sediments were deposited after 5.5 Ma. South TM is distinct from the rest of TM localities in bearing the camelid *Paracamelus gigas*, whereas this taxon is present at Kossom Bougoudi [68] where it constitutes the oldest known occurrence of a camelid in Africa, dated to the Mio-Pliocene transition [29,65]. It also lacks any remains of *Libycosaurus*. Further work should be necessary to determine if south TM could be coeval with Kossom Bougoudi (Fig. 9), notably a detailed comparison between *Ny. cf. australis* and the tetraconodont material of Kossom Bougoudi, initially attributed to *Ny. kanamensis* [65].

## Supporting Information

**Figure S1 Dental nomenclature after** [47]. A, tooth orientation: the top arrow indicates the mesio-lingual direction; B, structures identifiable on cingula/-ids; C, sketch of a right upper molar in occlusal view; D, Sketch of a right lower molar in occlusal view; E, sketch of a right upper premolar in occlusal view; F, Sketch of a right lower premolar in occlusal view. Abbreviations: Para., paracone; Proto., protocone; Meta., metacone; Metaul., metaconule; Metad., metaconid; Protod., protoconid; Entod., entoconid; Hypod., hypoconid; Hypoulid., hypoconulid; -c., -crista; -cul., -cristule; -cid., -cristid; -culid., -cristulid. (TIF)

**Figure S2 Complexity scoring of third molar variations in *Nyanzachoerus*.** Variation ranges of complexity scores (CS)
<figure><img src="image_12.png" /><figcaption>**Figure 9.** Geographical and temporal distribution of the main sites and species of *Nyanzachoerus* compared with *Ny. khinzir* nov. sp.
Abbreviated sites are: TM, Toros-Ménalla; south TM, south Toros-Ménalla; KB, Kossom Bougoudi; Kus., Kuseralee Member of the Sagantole Formation; Lower Naw., Lower Member of the Nawata Formation; Upper Naw., Upper Member of the Nawata Formation; Ibole, Ibole Member of the Wembere-Manonga Formation. Vertical bars represent site temporal range: light tone, biochronologically dated ranges; dark tone, geochronologically dated ranges; discontinuous outline, uncertain ranges. Biochronological range for TM is from [19], geochronological ranges for TM and Kossom Bougoudi are from [29].
doi:10.1371/journal.pone.0103221.g009</figcaption></figure>

biogeographical distinction between central Africa and eastern Africa. The biogeographical affinities of the late Miocene *Nyanzachoerus* from northern Africa are more uncertain because of limited samples, fragmentary preservation, and stratigraphic uncertainties.

## Biochronological implications

Together with other taxa, the tetraconodont material of TM was initially used to correlate the 'anthracotheriid unit' to the Lower Member of the Nawata Formation at Lothagam [19]. This was done on a limited sample confined to locality TM 266 and since then has been considerably augmented for a variety of mammalian taxa. The present work led us to recognize that this suid assemblage is instead attributable to a new species not yet found in other African sites, and therefore not supportive of previous correlation. Currently, it is therefore not possible to propose a biochronological correlation of TM on the basis of this suid material. The previous biochronological correlation proposed by Vignaud et al. ([19]: 154) between the 'anthracotheriid unit' and the Lower Nawata deposits remains supported by other faunal elements (prominently the proboscideans), the age of TM being based on this correlation and on the radiochronological dates proposed by Lebatard et al. [29,30]. The temporal placements of *Nyanzachoerus* from TM and other important Mio-Pliocene sites are summarized in Figure 9.

Within the 'anthracotheriid unit', locality TM 9 is somewhat different from other localities bearing *Ny. khinzir* because of specimen TM 9-01-019. This specimen could come from an unusual individual, which presence is not unexpected in such a large sample. Alternately, it could be indicative of an environmental and/or chronological difference between TM 9 and other localities. TM 9 is further particular because it is the richest TM locality with so few *Libycosaurus* (less than 1% of ca. 800 collected specimens). A chronological lag between TM 9 and other TM localities would probably involve limited time, because TM 9

otherwise differs clearly from Chadian fossiliferous areas with later deposits including more advanced tetraconodonts and different suid associations, namely Kossom Bougoudi in the upper-most Miocene [65,66] and Kollé in the lower Pliocene [67].

A subset of TM localities (south TM) bears a different, more advanced tetraconodont, provisionally recognized as *Ny. cf. australis*. According to the First Appearance Datum proposed for *Ny. australis* by Haile-Selassie [10] using the record of the Middle Awash research area in Ethiopia, this could indicate that these Chadian sediments were deposited after 5.5 Ma. South TM is distinct from the rest of TM localities in bearing the camelid *Paracamelus gigas*, whereas this taxon is present at Kossom Bougoudi [68] where it constitutes the oldest known occurrence of a camelid in Africa, dated to the Mio-Pliocene transition [29,65]. It also lacks any remains of *Libycosaurus*. Further work should be necessary to determine if south TM could be coeval with Kossom Bougoudi (Fig. 9), notably a detailed comparison between *Ny. cf. australis* and the tetraconodont material of Kossom Bougoudi, initially attributed to *Ny. kanamensis* [65].

## Supporting Information

**Figure S1 Dental nomenclature after** [47]. A, tooth orientation: the top arrow indicates the mesio-lingual direction; B, structures identifiable on cingula/-ids; C, sketch of a right upper molar in occlusal view; D, Sketch of a right lower molar in occlusal view; E, sketch of a right upper premolar in occlusal view; F, Sketch of a right lower premolar in occlusal view. Abbreviations: Para., paracone; Proto., protocone; Meta., metacone; Metaul., metaconule; Metad., metaconid; Protod., protoconid; Entod., entoconid; Hypod., hypoconid; Hypoulid., hypoconulid; -c., -crista; -cul., -cristule; -cid., -cristid; -culid., -cristulid. (TIF)

**Figure S2 Complexity scoring of third molar variations in *Nyanzachoerus*.** Variation ranges of complexity scores (CS)
for: A, talons of upper molars and B, talonids of lower third molars, mapped from various specimens of Nyanzachoerus. Grey cusps/-ids are not considered in the definition of the CS.
(TIF)

**Table S1** Additional cranial measurements (min.-max. in mm; mean; N) in Nyanzachoerus. Abbreviations: LN, Lower Nawata; AA, Adu-Asa; LW, Langebaanweg; *, male; Cr6, length between rostral extremity of premaxillae and staphylion; Cr7, length between staphylion and basion; Cr8, length between rostral and nuchal extremities of premaxillae; Cr9, premaxilla width at I3 level; Cr10, width between medial edges of canine alveoli; Cr11, width between P2 mesial extremities; Cr12, width between M3 distal extremities; Cr13, maximal enlargement of nasals on dorsal side, above premolar rows; Cr14, height between dorsal edge of orbit and M3 distal extremity.
(PDF)

**Table S2** Additional mandibular measurements (min.-max. in mm; mean; N) in Nyanzachoerus. Abbreviations: LN, Lower Nawata; UN, Upper Nawata; AA, Adu-Asa; LW, Langebaanweg; *, male; a, includes other specimens from Sahabi described as Ny. cf. syrticus by Cooke [31] in addition to the holotype; Md6, length between il-il diastema and nuchal extremity of condyle; Md7, length between il-il diastema and nuchal extremity of symphyse; Md8, width between distal i3; Md9, width between mesial p2; Md10, width between lingual p4; Md11, c-p2 diastema; Md12, c-p3 diastema.
(PDF)

**Table S3** Premolar width/length ratios (min.-max., mean; N) in Nyanzachoerus. Abbreviations: LN, Lower Nawata; UN, Upper Nawata; AA, Adu-Asa; LW, Langebaanweg; K, Kanapoi; M, Manonga; a, includes other specimens from Sahabi described as cf. Ny. syrticus by Cooke [31] in addition to holotype; difference with sample of Ny. khinzir (t-test): °, non-significant; *, p<0.05; **, p<0.01; ***: p<0.001. For all premolars, ratio is 100*w/L.
(PDF)

**Table S4** Additional molar measurements (min.-max. in mm; mean; N) in Nyanzachoerus. Abbreviations: LN, Lower Nawata; UN, Upper Nawata; AA, Adu-Asa; LW, Langebaanweg; K, Kanapoi; L, mesiodistal length at cervix; w, labiolingual width of mesial lobe of crown; difference with sample of Ny. khinzir (t-test): °, non-significant; *, p<0.05; **, p<0.01; ***: p<0.001.
(PDF)

**Table S5** Additional third molar measurements (min.-max. in mm; mean; N) in Nyanzachoerus. Abbreviations: LN, Lower Nawata; UN, Upper Nawata; AA, Adu-Asa; LW, Langebaanweg; h1, maximal height of the first pair of cusps/-ids; h2, maximal height of the second pair of cusps/-ids; H1, hypsodonty index (100*(h1/w)) of the first pair of cusps/-ids; H2, hypsodonty index (100*(h2/w)) of the second pair of cusps/-ids; H-tal, hypsodonty index (100*(h-tal/w)) of the talon/-id.
(PDF)

## References

1. Bishop LC (2010) Suoidea. In: Werdelin L, Sanders WJ, editors. Cenozoic Mammals of Africa. Berkeley: University of California Press. pp. 821–842.

2. Cooke HBS, Wilkinson AF (1978) Suidae and Tayassuidae. In: Maglio VJ, Cooke HBS, editors. Evolution of African Mammals. Cambridge: Harvard University Press. pp. 435–482.

3. Cooke HBS (1978) Suid evolution and correlation of African hominid localities: an alternative taxonomy. Science 201: 460–463.

4. Harris JM, White TD (1979) Evolution of the Plio-Pleistocene African Suidae. Transactions of the American Philosophical Society 69: 1–128.

5. White TD, Harris JM (1977) Suid evolution and correlation of African hominid localities. Science 198: 13–21.

**Table S6** Stable isotope data (δ13C and δ18O in ‰) obtained from carbonates of enamel apatite of Nyanzachoerus at TM 266 and TM 267. Abbreviations: *, specimens attributed to Ny. khinzir nov. sp. (other specimens are attributed to Nyanzachoerus sp.).
(PDF)

**Table S7** Craniodental measurements (in mm) and complexity scores of TM Nyanzachoerus. Note: measurements obtained with a digital caliper with a maximum deviation of 0.02 mm, rounded to nearest 0.1 mm.
(XLS)

**Text S1 Specimens of Nyanzachoerus from Toros-Ménalla, Chad.**
(PDF)

**Text S2 Summary of the dental nomenclature.**
(PDF)

**Text S3 Definition of complexity scores (CS).**
(PDF)

## Acknowledgments

This research was developed under the auspices of the following institutions: Chadian Ministère de l'Enseignement Supérieur et de la Recherche; Centre National d'Appui à la Recherche, N'Djamena; University of N'Djamena; French Ministère de l'Enseignement Supérieur et de la Recherche; Centre National de la Recherche Scientifique, Institut National Écologie et Environnement; University of Poitiers (UFR SFA); French Ministère des Affaires Étrangères (French Embassy in Chad). In addition, we would like to thank the following institutions and all their staff for authorizing the study of their collections: Authority for Research and Conservation of Cultural Heritage, Addis Ababa, Ethiopia; CNAR, N'Djamena, Chad; Field Museum, Chicago, USA; Forschungsinstitut und Naturmuseum Senckenberg, Frankfurt, Germany; HERC, University of California, Berkeley, USA; iPHEP, University of Poitiers, France; Iziko South African Museum, Cape Town, South Africa; Laboratory of Evolutionary Biology, Howard University, Washington D.C., USA; Muséum National d'Histoire Naturelle, Paris, France; Musée Royal de l'Afrique Centrale, Tervuren, Belgium; Museo di Paleontologia, Sapienza Università di Roma, Italy; Museum für Natuurkunde, Berlin, Germany; National Museums of Kenya, Nairobi; Natural History Museum, Berne, Switzerland; Natural History Museum, London, United Kingdom. We are most grateful to Tim White for discussions and for the opportunity to study the suids collected by the Middle Awash research project, as well as to the following people for their technical help and assistance: Lucile Jacques (isotopic analyses); Allowen Evin (Field Museum specimen imaging); Ghislaine Florent and Carine Noël (administrative guidance); Jérôme Surault (support in N'Djamena); Margaret Avery and Thalassa Matthews (support in Cape Town); all contributors to the MPFT field missions.

## Author Contributions

Conceived and designed the experiments: JRB PV MB. Performed the experiments: JRB AS. Analyzed the data: JRB AS MB. Contributed reagents/materials/analysis tools: JRB AS HTM AL PV MB. Wrote the paper: JRB.

6. Leakey LSB (1958) Some East African Pleistocene Suidae. London: British Museum (Natural History), Fossil Mammals of Africa 14. 132 p.

7. White TD (1995) African omnivores: global climatic change and Plio-Pleistocene hominids and suids. In: Vrba ES, Denton GH, Partridge TC, Burekle LH, editors. Paleoclimate and evolution with emphasis on Human origins. New Haven: Yale University Press. pp. 369–384.

8. Coppens Y (1971) Une nouvelle espèce de suidé du Villafranchien de Tunisie, *Nyanzachoerus jaegeri* nov. sp. Comptes Rendus de l'Académie des Sciences 272: 3264–3267.
for: A, talons of upper molars and B, talonids of lower third molars, mapped from various specimens of Nyanzachoerus. Grey cusps/-ids are not considered in the definition of the CS.
(TIF)

**Table S1** Additional cranial measurements (min.-max. in mm; mean; N) in Nyanzachoerus. Abbreviations: LN, Lower Nawata; AA, Adu-Asa; LW, Langebaanweg; *, male; Cr6, length between rostral extremity of premaxillae and staphylion; Cr7, length between staphylion and basion; Cr8, length between rostral and nuchal extremities of premaxillae; Cr9, premaxilla width at I3 level; Cr10, width between medial edges of canine alveoli; Cr11, width between P2 mesial extremities; Cr12, width between M3 distal extremities; Cr13, maximal enlargement of nasals on dorsal side, above premolar rows; Cr14, height between dorsal edge of orbit and M3 distal extremity.
(PDF)

**Table S2** Additional mandibular measurements (min.-max. in mm; mean; N) in Nyanzachoerus. Abbreviations: LN, Lower Nawata; UN, Upper Nawata; AA, Adu-Asa; LW, Langebaanweg; *, male; a, includes other specimens from Sahabi described as Ny. cf. syrticus by Cooke [31] in addition to the holotype; Md6, length between il-il diastema and nuchal extremity of condyle; Md7, length between il-il diastema and nuchal extremity of symphyse; Md8, width between distal i3; Md9, width between mesial p2; Md10, width between lingual p4; Md11, c-p2 diastema; Md12, c-p3 diastema.
(PDF)

**Table S3** Premolar width/length ratios (min.-max., mean; N) in Nyanzachoerus. Abbreviations: LN, Lower Nawata; UN, Upper Nawata; AA, Adu-Asa; LW, Langebaanweg; K, Kanapoi; M, Manonga; a, includes other specimens from Sahabi described as cf. Ny. syrticus by Cooke [31] in addition to holotype; difference with sample of Ny. khinzir (t-test): °, non-significant; *, p<0.05; **, p<0.01; ***: p<0.001. For all premolars, ratio is 100*w/L.
(PDF)

**Table S4** Additional molar measurements (min.-max. in mm; mean; N) in Nyanzachoerus. Abbreviations: LN, Lower Nawata; UN, Upper Nawata; AA, Adu-Asa; LW, Langebaanweg; K, Kanapoi; L, mesiodistal length at cervix; w, labiolingual width of mesial lobe of crown; difference with sample of Ny. khinzir (t-test): °, non-significant; *, p<0.05; **, p<0.01; ***: p<0.001.
(PDF)

**Table S5** Additional third molar measurements (min.-max. in mm; mean; N) in Nyanzachoerus. Abbreviations: LN, Lower Nawata; UN, Upper Nawata; AA, Adu-Asa; LW, Langebaanweg; h1, maximal height of the first pair of cusps/-ids; h2, maximal height of the second pair of cusps/-ids; H1, hypsodonty index (100*(h1/w)) of the first pair of cusps/-ids; H2, hypsodonty index (100*(h2/w)) of the second pair of cusps/-ids; H-tal, hypsodonty index (100*(h-tal/w)) of the talon/-id.
(PDF)

## References

1. Bishop LC (2010) Suoidea. In: Werdelin L, Sanders WJ, editors. Cenozoic Mammals of Africa. Berkeley: University of California Press. pp. 821–842.

2. Cooke HBS, Wilkinson AF (1978) Suidae and Tayassuidae. In: Maglio VJ, Cooke HBS, editors. Evolution of African Mammals. Cambridge: Harvard University Press. pp. 435–482.

3. Cooke HBS (1978) Suid evolution and correlation of African hominid localities: an alternative taxonomy. Science 201: 460–463.

4. Harris JM, White TD (1979) Evolution of the Plio-Pleistocene African Suidae. Transactions of the American Philosophical Society 69: 1–128.

5. White TD, Harris JM (1977) Suid evolution and correlation of African hominid localities. Science 198: 13–21.

**Table S6** Stable isotope data (δ13C and δ18O in ‰) obtained from carbonates of enamel apatite of Nyanzachoerus at TM 266 and TM 267. Abbreviations: *, specimens attributed to Ny. khinzir nov. sp. (other specimens are attributed to Nyanzachoerus sp.).
(PDF)

**Table S7** Craniodental measurements (in mm) and complexity scores of TM Nyanzachoerus. Note: measurements obtained with a digital caliper with a maximum deviation of 0.02 mm, rounded to nearest 0.1 mm.
(XLS)

**Text S1 Specimens of Nyanzachoerus from Toros-Ménalla, Chad.**
(PDF)

**Text S2 Summary of the dental nomenclature.**
(PDF)

**Text S3 Definition of complexity scores (CS).**
(PDF)

## Acknowledgments

This research was developed under the auspices of the following institutions: Chadian Ministère de l'Enseignement Supérieur et de la Recherche; Centre National d'Appui à la Recherche, N'Djamena; University of N'Djamena; French Ministère de l'Enseignement Supérieur et de la Recherche; Centre National de la Recherche Scientifique, Institut National Écologie et Environnement; University of Poitiers (UFR SFA); French Ministère des Affaires Étrangères (French Embassy in Chad). In addition, we would like to thank the following institutions and all their staff for authorizing the study of their collections: Authority for Research and Conservation of Cultural Heritage, Addis Ababa, Ethiopia; CNAR, N'Djamena, Chad; Field Museum, Chicago, USA; Forschungsinstitut und Naturmuseum Senckenberg, Frankfurt, Germany; HERC, University of California, Berkeley, USA; iPHEP, University of Poitiers, France; Iziko South African Museum, Cape Town, South Africa; Laboratory of Evolutionary Biology, Howard University, Washington D.C., USA; Muséum National d'Histoire Naturelle, Paris, France; Musée Royal de l'Afrique Centrale, Tervuren, Belgium; Museo di Paleontologia, Sapienza Università di Roma, Italy; Museum für Natuurkunde, Berlin, Germany; National Museums of Kenya, Nairobi; Natural History Museum, Berne, Switzerland; Natural History Museum, London, United Kingdom. We are most grateful to Tim White for discussions and for the opportunity to study the suids collected by the Middle Awash research project, as well as to the following people for their technical help and assistance: Lucile Jacques (isotopic analyses); Allowen Evin (Field Museum specimen imaging); Ghislaine Florent and Carine Noël (administrative guidance); Jérôme Surault (support in N'Djamena); Margaret Avery and Thalassa Matthews (support in Cape Town); all contributors to the MPFT field missions.

## Author Contributions

Conceived and designed the experiments: JRB PV MB. Performed the experiments: JRB AS. Analyzed the data: JRB AS MB. Contributed reagents/materials/analysis tools: JRB AS HTM AL PV MB. Wrote the paper: JRB.

6. Leakey LSB (1958) Some East African Pleistocene Suidae. London: British Museum (Natural History), Fossil Mammals of Africa 14. 132 p.

7. White TD (1995) African omnivores: global climatic change and Plio-Pleistocene hominids and suids. In: Vrba ES, Denton GH, Partridge TC, Burekle LH, editors. Paleoclimate and evolution with emphasis on Human origins. New Haven: Yale University Press. pp. 369–384.

8. Coppens Y (1971) Une nouvelle espèce de suidé du Villafranchien de Tunisie, *Nyanzachoerus jaegeri* nov. sp. Comptes Rendus de l'Académie des Sciences 272: 3264–3267.
9. Kotsakis T, Ingino S (1979) Osservazioni sui *Nyanzachoerus* (Suidae, Artiodactyla) del Terziario superiore di Sahabi (Cirenaica-Libia). Bollettino del Servizio Geologico d'Italia 100: 391-408.

10. Haile-Selassie Y (2009) Suidae. In: Haile-Selassie Y, WoldeGabriel G, editors. *Ardipithecus kadabba*. Late Miocene Evidence from the Middle Awash, Ethiopia. Berkeley: University of California Press. pp. 331-371.

11. Arambourg C (1968) Un suidé fossile nouveau du Miocene supérieur de l'Afrique du Nord. Bulletin de la Société Géologique de France 7: 110-115.

12. Cooke HBS, Coryndon SC (1970) Pleistocene mammals from the Kairo Formation and other related deposits in Uganda. In: Leakey LSB, Savage RJG, editors. Fossil Vertebrates of Africa. London: Academic Press. pp. 147-198.

13. Leonardi P (1952) Resti fossili di *Sivachoerus* del Giacimento di Sahabi in Cirenaica (Africa settentrionale). Notizie preliminari. Atti della Accademia Nazionale dei Lincei, Rendiconti, Series 8, 13: 166-169.

14. Cooke HBS, Ewer RF (1972) Fossil Suidae from Kanapoi and Lothagam, Northwestern Kenya. Bulletin of the Museum of Comparative Zoology 143: 149-296.

15. Cooke HBS, Hendey QB (1992) *Nyanzachoerus* (Mammalia: Suidae: Tetracodonontinae) from Langebaanweg, South Africa. Durban Museum Novitates 17: 1-20.

16. van der Made, J (1999) Biometrical trends in the Tetracodonontinae, a subfamily of pigs. Transactions of the Royal Society of Edinburgh: Earth Sciences 89: 199-225.

17. Harris JM, Leakey MG (2003) Lothagam Suidae. In: Leakey MG, Harris JM, editors. Lothagam. The dawn of humanity in eastern Africa. New York: Columbia University Press. pp. 485-519.

18. Pickford M (2012) Ancestors of Broom's pigs. Transactions of the Royal Society of South Africa 67: 17-35.

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9. Kotsakis T, Ingino S (1979) Osservazioni sui *Nyanzachoerus* (Suidae, Artiodactyla) del Terziario superiore di Sahabi (Cirenaica-Libia). Bollettino del Servizio Geologico d'Italia 100: 391-408.

10. Haile-Selassie Y (2009) Suidae. In: Haile-Selassie Y, WoldeGabriel G, editors. *Ardipithecus kadabba*. Late Miocene Evidence from the Middle Awash, Ethiopia. Berkeley: University of California Press. pp. 331-371.

11. Arambourg C (1968) Un suidé fossile nouveau du Miocene supérieur de l'Afrique du Nord. Bulletin de la Société Géologique de France 7: 110-115.

12. Cooke HBS, Coryndon SC (1970) Pleistocene mammals from the Kairo Formation and other related deposits in Uganda. In: Leakey LSB, Savage RJG, editors. Fossil Vertebrates of Africa. London: Academic Press. pp. 147-198.

13. Leonardi P (1952) Resti fossili di *Sivachoerus* del Giacimento di Sahabi in Cirenaica (Africa settentrionale). Notizie preliminari. Atti della Accademia Nazionale dei Lincei, Rendiconti, Series 8, 13: 166-169.

14. Cooke HBS, Ewer RF (1972) Fossil Suidae from Kanapoi and Lothagam, Northwestern Kenya. Bulletin of the Museum of Comparative Zoology 143: 149-296.

15. Cooke HBS, Hendey QB (1992) *Nyanzachoerus* (Mammalia: Suidae: Tetracodontinae) from Langebaanweg, South Africa. Durban Museum Novitates 17: 1-20.

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