Lahimia selloumi, Solé & Gheerbrant & Amaghzaz & Bouya, 2009

Solé, Floréal, Gheerbrant, Emmanuel, Amaghzaz, Mbarek & Bouya, Baâdi, 2009, Further evidence of the African antiquity of hyaenodontid (‘ Creodonta’, Mammalia) evolution, Zoological Journal of the Linnean Society 156 (4), pp. 827-846 : 830-843

LAHIMIA SELLOUMI SOLE & GHEERBRANT SP. NOV.

( FIGS 5–8 )

Etymology: Dedicated to Omar Selloum, a technician from OCP, for his expert knowledge of the geology of the phosphates quarries, and for his key help with the fieldwork and recovery of fossil material.

Holotype: OCP DEK/GE 443 ( PM 75 ), right dentary with M 1–3 and alveoli of P 2–4 and part of C 1.

Hypodigm: OCP DEK/GE 443 ( PM 75 ), holotype, right dentary with M 1–3 ; MNHN PM 56 , right dentary with M 2–3 and roots of M 1 ; MNHN PM 57 , left dentary with M 1–3, and roots of P 3 ; OCP DEK/GE 442 ( PM 76 ), left dentary with M 2–3 and alveoli (with broken roots) of P 2–4 –M 1 .

Diagnosis and distribution: As for the type species, only known species.

Etymology: Derived from ‘Lah’me’ (Arabic) = meat, Laahime (Arabic,) = carnivorous, by reference to the carnivorous diet of this taxon.

Type locality and age: Ouled Abdoun basin, Sidi Chennane quarries, bed IIa of the local mining lithostratigraphical terminology, lower bone-bed horizon, Thanetian. Specimens of this species were found by local people (as for most mammal material from the Ouled Abdoun basin) and the exact localities in the Sidi Chennane quarries are unknown. However, we located the place of origin of OCP DEK/GE 442 with the help of our field collaborator O. Selloum ( OCP) and the discoverer (M. Makroub). Geographical coordinates of the locality of OCP DEK/GE 442 are: 32°39.130′N, 6°41.300′W .

Diagnosis: Dental morphology most closely related to Boualitomus with shared features such as mandibular symphysis anterior to P 2, mental foramina posteriorly located (below P 2 and P 4), P 1 lost, reduced exodaenodonty, precingulid extended labially, protoconid labially inflated with apex set lingually, trigonid much larger than talonid, very narrow postfossid, talonid cusps reduced and crestiform (but remaining inflated transversally at their base), and hypoconulid and hypoconid not separated by a notch. It differs from Boualitomus by the P 2 being small with anterior root reduced, the paraconid being larger and more lingually located, the metaconid being reduced (distinctly smaller than paraconid), the trigonid being extended mesiodistally, and the talonid on M 3 being shorter than on M 1 and M 2. Close relationships of Lahimia and Boualitomus with Koholia and Koholiinae are suggested by the affinity of occlusal and wear pattern of molars.

Description

Lower molars ( Figs 5 , 6 , 7 ): This species is known only by the lower dentition, and mostly by the lower molars.

M 1 is significantly smaller than M 2 and M 3. M 2 and M 3 are of similar size. M 2 is slightly higher than M 3 in OCP DEK/GE 443, but not in other specimens ( Table 2). M 1 is distinguished by a paraconid slightly shifted labially with respect to the metaconid; in M 2, the paraconid is more or less at the level of the metaconid; in M 3 it is more lingual. The talonid is very slightly smaller in M 3 than in M 2 and M 1. The trigonid is slightly longer from M 1 to M 3, except in MNHN PM57.

Otherwise, the three lower molars have similar morphology. The trigonid is remarkably high and sharp. It is much larger (and higher) than the talonid. It is not compressed, but somewhat expanded mesiodistally with a prefossid well opened lingually. The paraconid is in a lingual position, and more so on the posterior molars. The paraconid is noticeably large; it is larger and significantly higher than the metaconid. The metaconid is remarkably reduced in MNHN PM56. The protoconid is much higher (and larger) than the metaconid and paraconid. The paracristid is blade-like and high. It is more longitudinal than transversal. The protocristid is by contrast transversal, with a metaconid more or less aligned transversely to the protoconid. The mesiolingual flank of the paraconid is strongly prominent mesiolingually; and it is sharp with development of a slight crest overhanging the talonid of the preceding tooth. This crest is in the continuity of the entocristid of the anterior tooth, as a functional extension. The tooth fits closely with the preceding molar between this ‘pre-paraconid’ crest and the precingulid. However, there is no mesiolingual cuspule below the paraconid. The precingulid is thin and long; it extends labially nearly as far as the labial flank of the protoconid. Its lingual part is steep below the paracristid notch. There are deep carnassial notches on the protocristid and paracristid. The lingual flank of the protoconid is convex in its vertical axis. The metaconid apex is only weakly more distal than the protoconid apex. The postmetacristid is absent.

The talonid is remarkably narrow, as well as its postfossid. It is elongate and oblique with respect to the longitudinal axis of the tooth (labially shifted distally). The talonid cusps are typically reduced and crestiform. However, their bases are more inflated transversally than in Prototomus Cope , *Estimated measurements.

L, length; Ltri, length of trigonid; Ltal, length of talonid; Wtri, width of trigonid; Wtal, width of talonid; Htri, height of trigonid; Htal, height of talonid.

1874. All cusps are in posterior positions. The hypoconulid is distal, and slightly closer to the hypoconid than to the entoconid. The hypoconid is poorly differentiated; it appears as a crest slightly inflated at its base (it is more inflated than in Prototomus ). The hypoconulid is the higher talonid cusp, but it is smaller than entoconid and hypoconid. The entoconid is as high as the hypoconid. The hypoconulid is particularly well developed on M 3. The hypoflexid is deep. The cristid obliqua joins the trigonid almost at its lingual half, and it rises on the posterior wall of the trigonid. There is a small but distinct carnassial notch on the mesial part of the cristid obliqua, at the base of its rising segment on the trigonid. The entocristid reaches the metaconid at its base, and it lingually closes the postfossid. It is oblique distolabially. No postcingulid or labial cingulid are present.

Anterior dentition ( Figs 5 , 8 ): No lower premolars are known, but information on the anterior dentition is available from the preserved alveoli and broken roots. Premolars seem to have been compressed labiolingually. P 3 and P 4 are of comparable size and are double-rooted. The mesial root of P 3 is smaller than the distal one. P 2 is double-rooted on OCP DEK/GE 442, also with a smaller mesial root ( Fig. 7 ). The anterior root of P 2 seems strongly reduced or absent on OCP DEK/GE 443. The alveolus preserved in OCP DEK/GE 443 suggests that P 2 was slightly proclive. There is a diastema of increasing size between P 4 and P 3 (very small, see Table 3), P 3 and P 2, and P 2 and C 1. Only OCP DEK/GE 443 preserves a trace of the lower canine (posterior margin of the alveolus).

Wear ( Fig. 11 ): Attrition wear facets 1 and 2, with steep striae, are distinct. The most remarkable wear feature is the development of a strong wear facet 3 in M 1–3 of all specimens. This facet lacks enamel and markedly truncates the labial flank of the hypoflexid (where the ectocingulid is usually located in several other ‘creodonts’). It corresponds to the extensive occlusion of the paracone of the opposite upper molar, which was probably very high and sharp (by contrast to a reduced Values in parentheses are the estimated measurement from alveoli position.

metacone). Some specimens, such as MNHN PM56, show that this facet extends on the posterior wall of the trigonid along the cristid obliqua, where the enamel is worn off. By contrast, wear facet 4 is absent because of the small and distal hypoconid.

Occlusal lower molar pattern and significance for upper molar pattern ( Fig. 11 ): The morphology and wear pattern of the lower molars bear evidence of some important features of the upper molars. The high and large trigonid, the reduced (crestiform) and distally located hypoconid, and the small talonid and postfossid indicate a strongly fused paracone and metacone (zalambdodonty), a paracone significantly larger and higher than the metacone, and a narrow and small protofossa and protocone. The remarkable extension of wear facet 3 on the labial flank of the hypoconid and hypoflexid in Lahimia reflects the enhancement of the cristid obliqua/postparacrista shearing couple. It is correlated primarily in Lahimia with a very sharp and high paracone, which was at the origin of the wear during the occlusion, and which was an important shearing–puncturing structure in the molar construction of the Moroccan form. It may be also related to the posterior position of the hypoconid and a lingual position of the paracone with respect to the metacone. The absence of wear facet 4 and the small (and distal?) hypoconid may correspond to a metaconid strongly connate to the paracone (reduced premetacrista). In addition to the dominant *Estimated measurements. postvallum/prevallid shearing, a significant role of prevallum/postvallid shearing in Lahimia is indicated by the development of the protocristid and wear facet 1. The orientation of the paracristid (poorly transversal) suggests a correspondingly distolabially orientated metacrista.

Dentary ( Figs 5 , 6 , 8 ): The horizontal ramus is moderately high ( Table 5) but its height is constant from its distal part to the canine. It is rather robust with a ventral margin more or less inflated transversely, especially at the posterior part. No trace of symphysis is visible, suggesting it was short, anterior to P 2. There is a large mental foramen below the P 2–3 diastema (OCP DEK/GE 443), and a smaller one below the distal root of P 4 (OCP DEK/GE 442). The coronoid crest is well developed and is clearly inclined distally. The masseteric fossa is deep. The lingual flank of the horizontal ramus is deepened by a longitudinal fossa; this fossa follows the mandibular canal, which is remarkably large in the Moroccan species, as seen in OCP DEK/GE 442 and 443. This structure results from a post-mortem deformation related to the synsedimentary compaction.

Comparisons

This comparison is summarized in Table 6 (except for Koholia , only known by its upper dentition). The comparison refers to the derived features 1–15 of Lahimia listed in Table 6. Figure 9 is a comparison of occlusal sketches of the lower molars of Lahimia , Boualitomus , and Prototomus minimus Smith & Smith, 2001 . Figure 10 is a comparison of tooth length and width profiles from the three lower molars in different ‘Proviverrinae’ taxa.

‘Proviverrinae’: ‘Proviverrinae’ represents a paraphyletic stem group assemblage of hyaenodontids ( Polly, 1996). Morlo & Gunnell (2003) distinguished two groups within ‘Proviverrinae’: (1) ‘true’ Proviverrinae or Proviverrinae s.s., which includes ‘ Proviverra ’ eisenmanni Godinot, 1981 and Parvagula palulae Lange-Badré, 1987 , and is characterized by a doublerooted P 1 and a talonid with well cuspate and distinct cusps; in this work it is hereafter referred to as the Proviverra -like group; and (2) North American, European, and Asian ‘ Prototomus -like group’ which is characterized by a single-rooted P 1 and reduced cusps of the talonid, notably the entoconid (except for the primitive genus Arfia Van Valen, 1965 ); it is hereafter referred to as the Prototomus -like group.

Features of the lower molars of Lahimia shared with primitive ‘proviverrine’ hyaenodontids such as Tinerhodon , Proviverra Rütimeyer, 1862 , Boualitomus , Parvagula Lange-Badré, 1987 , and Prototomus , which are probably representative of the ancestral morphotype of the Hyaenodontidae , are the following: M 1 smaller than M 2–3, and M 2 and M 3 of comparable size; paraconid enlarged but poorly shifted mesially; protoconid sharp and high above the paraconid and metaconid; posterior position of the talonid cusps; hypoconulid higher than entoconid and hypoconid, and distally salient; presence of a carnassial notch on the cristid obliqua; talonid oblique; cristid obliqua median or slightly lingual on the trigonid. The presence of diastemata developed between the premolars is also primitive in the ‘Proviverrinae’. Among ‘proviverrines’, the species is larger than Boualitomus , Tinerhodon , and Prototomus minimus Smith & Smith, 2001 . Its size is close to that of Galecyon morloi Smith & Smith, 2001 from Dormaal ( Belgium, MP7, early Eocene). Lahimia differs from these taxa by noticeable derived features such as the small metaconid (smaller than the paraconid), the typical reduction of the entoconid, the absence of P 1 and P 2 small with reduced anterior root.

Tinerhodon : Tinerhodon , described from the late Palaeocene of the Ouarzazate Basin ( Gheerbrant, 1995), is the most primitive known Hyaenodontidae ‘Proviverrinae’ (Gheerbrant et al., 2006). Lahimia is much larger than Tinerhodon . The mesiodistally expanded trigonid of Lahimia is derived with respect to Tinerhodon ( Table 6, K10). The paraconid is larger (although nearly as high as the metaconid in Tinerhodon ) and more developed lingually and mesially ( Table 6, K6), which results in a more elongated and less transverse paracristid. The mesiolingual flank of the paraconid presents a distinct crest (no trace in Tinerhodon ). The precingulid extends less lingually on the mesial flank of the trigonid. This might be related to the lingual development of the paraconid. The metaconid is much smaller, less slender, and especially shorter transversely ( Table 6, K 7); its apex is less lingually set. The protoconid is also higher with respect to the metaconid and paraconid. The protoconid apex is also less projected distally and labially ( Table 6, K9). The talonid is much narrower in Lahimia ( Table 6, K11), and it bears more reduced and crestiform talonid cusps ( Table 6, K12). It is also more oblique and slightly shorter (especially in M 1–2) in Lahimia . Contrary to Tinerhodon , there are no accessory cusps (no entoconulid and mesoconid; Table 6, K13). The hypoconid and hypoconulid are not separated by a distolabial notch ( Table 6, K14). The exodaenodonty is reduced in Lahimia ( Table 6, K 5).

Underlined numbers indicate characters supporting a close relationship between Lahimia selloumi gen. et sp. nov. and Boualitomus marocanensis . K, characters.

reduced talonid cusps which are very well developed in Arfia . Moreover, Arfia is derived in several traits with respect to Lahimia : the strong development of the precingulid, the ectocingulid, and the postcingulid, the crenulated enamel, the lower crowned M 1 and M 2 (whereas M 3 is higher and trenchant), the talonid as large as the trigonid and the hypoconid higher than the hypoconulid.

The anterior mental foramen is located more distally in Lahimia : it is placed below the posterior part of P 2, whereas in Tinerhodon it is located below the anterior part of P 2 ( Table 6, K 1).

Most of these differences from Tinerhodon are also distinctive for Boualitomus . They relate to the remarkably derived construction of Lahimia and Boualitomus by contrast to Tinerhodon and also to Proviverra and Prototomus (see Table 6). This is especially true for the construction of the talonid ( Table 6, K12–14) and trigonid ( Table 6, K6, 7, 10) of the molars. This underlines the precociously specialized morphology of Lahimia (and Boualitomus ).

Arfia : Arfia Van Valen, 1965 is one of the first hyaenodontid genera to appear at the beginning of the Eocene in the Laurasian continents with Prototomus , Proviverra , and Galecyon Gingerich & Deutsch, 1989 . It is the only known hyaenodontid genus common to Asia, Europe, and North America ( Gingerich & Deutsch, 1989; Smith & Smith, 2001; Lavrov & Lopatin, 2004). Lahimia has no particular resemblance to Arfia . Lahimia differs by its derived features listed in Table 6, such as especially the smaller metaconid, the loss of P 1 and the small P 2 (with reduced anterior root), the narrow prefossid, and the Prototomus : European species of Prototomus are differentiated by M 3 being distinctly smaller than M 2 ( Smith & Smith, 2001). This character is more derived than in Boualitomus and Lahimia . Lahimia is the same size as Prototomus deimos Gingerich & Deutsch, 1989 (Wasachtian 0–3), which is the oldest and smallest of the North American species of the genus. It shares features with Prototomus such as the talonid cusps being more crestiform than in Proviverra , and the presence of three similar diastemata between the premolars (before P 2, P 3, and P 4). Other shared features are primitive ‘proviverrine’ features: M 1 smaller than M 2 and M 3, M 2 and M 3 similar in size (North American Prototomus ). Lahimia differs from Prototomus mostly by derived features. Important differences are the absence of P 1, P 2 small with reduced anterior root ( Table 6, K 3–4), the paraconid much larger and higher, and more lingual ( Table 6, K6) resulting in a longer paracristid, and the metaconid smaller ( Table 6, K 7). The precingulid is more extended labially ( Table 6, K8). The protoconid is higher, but less raised vertically because of its labial flank being more inflated and its apex set more lingually ( Table 6, K9). Comparison with Tinerhodon suggests that the condition is derived in Lahimia . The trigonid is less compressed mesiodistally ( Table 6, K10). The proportion of the trigonid and talonid is also very distinctive. In Lahimia , the trigonid is larger with respect to the talonid and the postfossid is significantly narrower than in Prototomus ( Table 6, K11). The talonid cusps are significantly more reduced and crestiform, but also more inflated transversally ( Table 6, K12). The entoconulid, which is present in the oldest Prototomus species , is absent in Lahimia ( Table 6, K13). The hypoconulid and hypoconid are less separated distally ( Table 6, K14). The M 3 has a noticeably shorter talonid ( Table 6, K15). The crown is poorly or not exodaenodont by contrast to other ‘proviverrine’ genera ( Table 6, K 5). The mandibular symphysis is shorter: it extends below P 2 in Prototomus ( Table 6, K 1). Probably correlated to this mandible symphysis shortening, the anterior mental foramina are more distal (anterior to P 2 and P 3 in Prototomus minimus ) ( Table 6, K 2). In addition, the lower molars of Lahimia are proportionally wider than in Prototomus , although less markedly than Boualitomus with respect to Prototomus . Some of these features are also distinctive of Boualitomus from Prototomus , and are probably indicative of close affinity of Boualitomus and Lahimia , especially the shortening of the anterior dentition ( Table 6, K 1–3), and the small and simplified talonid ( Table 6, K11–12, 14).

A few known features of Lahimia with respect to Prototomus might be primitive. The entoconid being more inflated transversely at its base is reminiscent of Proviverra and Tinerhodon . Inflated talonid cusps, as well as accessory cusps, are, as a whole, primitive features known in cimolestids (Gheerbrant et al., 2006). The shearing specialization of hyaenodontids resulted in structural simplification with respect to the ancestral cimolestid morphotype. In this respect, the entoconid more compressed in Prototomus is a possible autapomorphic trait. Prototomus and related taxa are also more derived in the presence of an ectocingulid or ectostylid, also known in Tinerhodon , ‘ Proviverra ’ eisenmanni, and Parvagula palulae .

Galecyon: The genus Galecyon is as old as Prototomus , but its lower molars possess a more derived morphology ( Smith & Smith, 2001). The entoconid is more reduced and crestiform in Galecyon than in Prototomus . It is replaced by a lingual crest that links the distal facet of the metaconid to the hypoconulid.

Proviverra : Proviverra has the most primitive molars within the Proviverra -like group. It is characterized by well-developed talonid cusps, as in Tinerhodon and Cimolestidae . The generic position of ‘ Proviverra ’ eisenmanni is questionable; its features shared with Proviverra typica may only be primitive. Lahimia differs from ‘ Proviverra’ eisenmanni in its size (three times larger) and by the loss of P 1, which is retained and biradicular in Proviverra and other ‘true’ Proviverrinae. Lahimia differs from ‘ Proviverra ’ eisenmanni by several other noticeable features reported in Table 6 (K1, 3, 5–10, 12, 14–15). In ‘ Proviverra’ eisenmanni the hypoconid is much more developed and salient labially, and it is separated from the other cusps by a significant notch. Noticeable shared primitive characters of Lahimia and Proviverra are the base of the talonid cusps being transversely inflated and the absence of an ectocingulid or ectostylid. Lower molars of Parvagula palulae have the same differences as ‘ Proviverra ’ eisenmanni with respect to Lahimia .

Boualitomus : Lahimia shares primitive hyaenodontid (‘proviverrine’) features with Boualitomus , such as the M 3 comparable in size to M 2 and occurrence of similar diastemata between the premolars. Lahimia is closer to Boualitomus than to any ‘proviverrine’, notably in the talonid remarkably narrow and oblique, the talonid cusps typically reduced (crestiform) and the weak exodaenodonty. Boualitomus and Lahimia share also features related to a shortening of the anterior dentition, such as the mental foramina being more distal than in Prototomus and other ‘proviverrine’ genera, the symphysis short, and the absence of P 1. These features are derived amongst primitive hyaenodontids: They suggest close affinity of the two genera with respect to known ‘proviverrines’. The ventral margin of the horizontal ramus is inflated transversely in the two genera, but the polarity of this feature is uncertain.

Lahimia is however distinctive from Boualitomus in several features such as the larger size (150%) and features related to a more specialized carnassial/ shearing function: the trigonid is more expanded mesiodistally with the paracristid more extended mesially, the paraconid is significantly larger (and higher) and more lingual, and the metaconid is smaller. The talonid is slightly shorter on M 3 and wider on M 1, more or less as in Prototomus . The compression and reduction (shortening) of the anterior dentition is more marked in Lahimia with the P 2 smaller (anterior root reduced), and slightly more distal mental foramina. These features clearly support the generic distinction of L. selloumi and B. marocanensis , and they indicate that Lahimia is more derived, despite its presumed older age (but note that the Ypresian age of Boualitomus remains uncertain).

Koholia ( Fig. 11 , Table 7): The genus Koholia from the late early Eocene of El Kohol ( Algeria) cannot be compared directly with Lahimia because it is known only from a fragment of maxillary bearing P 4 and M 1 and roots of M 2. However, the remarkable upper molar occlusal pattern of Koholia is indicative of related morphological features of the opposite molars (e.g. Butler, 1961: 121: ‘every upper pattern implies a lower pattern’): this is illustrated in Figure 11 and Table 7. The very small protocone of Koholia is reminiscent of the reduced talonid in Lahimia . In addition, the metacone highly fused to paracone in Koholia agree with the reduced talonid cusps, especially the hypoconid, and with the very high trigonid (protoconid) seen in Lahimia . These features are linked to the zalambdodont morphology. The wide stylar shelf bearing long crests in Koholia exemplifies the predominance of the labial phase (phase I) major shearing structures (paracrista and metacrista) at the expense of the small primary grinding structures (protocone–protofossa) involved in the lingual phase. This is reminiscent of the wide primary trigon ( Butler, 1978) known in cimolestids and primitive eutherians. This pattern of Koholia functionally corresponds to the wide predominance of the lower molar whole, the significant prevallum/postvallid shearing is a noticeable shared feature of Lahimia and Koholia . Moreover, the paracone is very high and pointed, more lingually located than the metacone, and it bears an extensive lingual wear facet 3 in Koholia . This corresponds precisely to the strong wear facet 3, which truncates the long labial flank of the cristid obliqua and the deep hypoflexid in Lahimia . The distolingual facet of the protocone is very worn in Koholia (wear facet 6). This seems correlated in Lahimia with the crest-like development of the mesiolingual flank of the paraconid, which presents a wear facet with steep striae. This structure functionally supplies or extends the entoconid (small and crestiform).

This comparison suggests systematic affinity of Lahimia and Koholia . Koholia remains distinctive from Lahimia in its much larger size and in the probably more advanced development of the carnassial/shearing. Noticeable derived features in Koholia are the very long and distally orientated postmetacrista (55° in M 1 with respect to the longitudinal axis vs. 65° for the M 2 paracristid of Lahimia ), and the very small protocone.

trigonid and its shearing structures (paracristid and protocristid) over the small (narrow) talonid and postfossid seen in Lahimia . The developed paracrista, high and very transverse in the M 1 of Koholia , with a parastyle (homology fide Crochet, 1988) not shifted mesially by contrast to e.g., Prototomus , fits with a transverse protocristid (with metaconid very poorly shifted distally) bearing a strong wear facet 1, as seen in Lahimia . In Koholia , the prevallum/postvallid shearing structure extends to the paraconule and protocone, which are aligned transversally in continuity with the parastyle and preparacrista, and which present distinct wear facets (1b and 5). As a Discussion

Within ‘creodonts’, Lahimia , as Boualitomus , has obvious affinities with primitive hyaenodontids, and especially with ‘Proviverrinae’. It shows closer resemblances with European and North American ‘Proviverrinae’ such as the Prototomus -like group, than with the Proviverra -like group. This is especially supported by the absence of P 1 (P 1 biradicular in the Proviverra -like group, uniradicular in the Prototomus -like group), the narrow talonid (although wider in Prototomus ), and the reduced and crestiform talonid cusps, including the entoconid (although the base of the cusps are more compressed in Prototomus ). These resemblances between the Prototomus - like group and Lahimia (and Boualitomus ) may be the result of possible close phylogenetic relationships, if they are not homoplastic.

However, Lahimia is more advanced than primitive European and North American ‘Proviverrinae’ in several remarkable features. It differs strikingly from Prototomus by the more advanced reduction of anterior premolars, with complete loss of P 1, and smaller P 2. Other notable derived features of Lahimia , such as the narrow molar talonid with reduced and crestiform cusps, are indicative of a more advanced carnassial/shearing function than in early European and North American ‘Proviverrinae’. These derived features of Lahimia are actually shared with Boualitomus , and are notably original with respect to ‘Proviverrinae’. They are probable synapomorphies indicating an original African suprageneric hyaeno- See comparison of the occlusal sketches of the M 1 of Koholia , and the M 1 of Lahimia in Figure 11 .

dontid clade, distinct from all known hyaenodontid subfamilies. This early African group is precociously specialized, with an original shortening of the dentary (Gheerbrant et al., 2006), a reduction and simplification of the talonid, and a weak exodaenodonty. These features refute a direct ancestral relationship to European and North American ‘proviverrines’ such as Prototomus and Proviverra (contra Gheerbrant et al., 2006). Lahimia and Boualitomus exemplify a derived but old lateral African endemic hyaenodontid lineage, with at least late Palaeocene roots. This is therefore an early African hyaenodontid offshoot.

Lahimia and Boualitomus , from the same Ouled Abdoun Basin, indeed seem to exemplify an original group of early African hyaenodontid, distinct from known Laurasian ‘proviverrines’. However, Lahimia is significantly more derived than Boualitomus , especially in the larger size, the smaller P 2, and a more advanced carnassial specialization with larger paraconid and paracristid and reduced metaconid. This is unexpected because Boualitomus , which comes from the Grand Daoui Quarries, is presumed to be younger ( Gheerbrant et al., 2003, 2006). However, the exact locality and level of Boualitomus in Grand Daoui remains unknown. The stratigraphical discrepancy in the evolutionary grade of Lahimia and Boualitomus has at this time three possible interpretations: (1) the two genera are not directly related, and this is evidence of a significant radiation of the African group illustrated by the two genera; (2) Boualitomus has been wrongly dated as Ypresian, and is actually significantly older than Lahimia (which is late Palaeocene); (3) Boualitomus belongs to an old conservative lineage, as is probable for Tinerhodon .

Koholia (late early Eocene of Algeria) was described by Crochet (1988) as representative of an old African endemic hyaenodontid lineage. Although Koholia cannot be compared directly, the occlusal pattern of its upper molars is most consistent with the lower molar pattern of Lahimia and Boualitomus (see Table 7, Fig. 11 and section on Koholia ). The most striking related features of upper molars of Koholia are reported in Table 7 and Figure 11 . The welldeveloped preparacrista of Koholia agrees with relative development and function of the protocristid in Lahimia ( Table 7: I). It indicates a significant prevallum/postvallid shearing function in both Lahimia and Boualitomus , in addition to the specialized (dominant) postvallum/prevallid shearing ( Table 7: V). This is a peculiar character of the Koholiinae , which is unknown in other Hyaenodontidae . It is a primitive feature reminiscent of eutherian stem groups such as the cimolestids, or a secondary (i.e. enhanced) feature. The transversal alignment of the preparacrista, the parastyle, the paraconule, and the protocone in Koholia may support a secondary development of the prevallum/postvallid shearing in the Koholiinae . These affinities in molar pattern suggest to us a likely relationship of Lahimia and Boualitomus to Koholiinae , even if it must be acknowledged that this needs to be further substantiated with the discovery of homologous dentitions. The shortening of the anterior dentition (loss of P 1, symphysis very short, mental foramina posteriorly located) shared by Lahimia and Boualitomus remains in particular to be evaluated in Koholia .

The advanced morphology of Lahimia is quite surprising with respect to its age, the species being the oldest known hyaenodontid. Tinerhodon , also from the Thanetian, is much more primitive and fits better with ‘Proviverrinae’, although it also illustrates a suitable ancestral morphotype for Lahimia , and actually for the whole Hyaenodontidae . It is indeed noticeable that few primitive features are recorded in Lahimia with respect to other ‘Proviverrinae’. The only known primitive feature of Lahimia with respect to ‘Proviverrinae’ may be the entoconid being transversally inflated at its base. The developed prevallum/ postvallid shearing in Lahimia and Koholiinae is interpreted as a possible secondary (enhanced) original feature. In the alternative view, it would be a primitive eutherian feature supporting the basal branching of the Koholiinae within Hyaenodontidae . In any case, Lahimia remains poorly known, and only by the lower molars. In particular, the primitive morphology of P 4 of Boualitomus , which retains a protostylid (as in European Prototomus ), cannot be checked in Lahimia . Other primitive features of Lahimia are actually also known in Boualitomus , Tinerhodon , and the oldest ‘true’ Proviverrinae (see ‘Proviverrinae’ section), and may be representative of the Hyaenodontidae ancestral morphotype.

Figure 12 illustrates our preliminary view of the phylogenetic relationships of L. selloumi and the Koholiinae within Hyaenodontidae (main lineages), based on our character analysis and current knowledge. The character study especially supports sister group relationships of the Koholiinae and the Prototomus -like group (possibly related to Limnocyoninae). This phylogeny emphasizes an early – widely unknown – African evolution with several ghost lineages for the Koholiinae , as well as for Laurasian ‘Proviverrinae’ such as the Proviverra -like group and the Prototomus- like group. This tentative phylogeny of the Koholiinae needs to be further substantiated and tested (1) by better knowledge of the Koholiinae , and (2) by a dedicated parsimony analysis dealing especially with the early Eocene European hyaenodontid taxa (F. Solé, unpubl. data).

Figures

Figure 5. Lahimia selloumi gen. et sp. nov. A–C, holotype OCP DEK/GE 443, right lower jaw bearing M1–M3, roots of P4 and alveoli of C1 and P2–P3. A, Occlusal stereo-view; B, labial view; C, lingual view. D–F, OCP DEK/GE 442, left lower jaw bearing M2–M3 and alveoli with broken root of P2–P4 and M1. D, Occlusal stereo-view; E, labial view; F, lingual view.

Figure 6. Lahimia selloumi gen. et sp. nov. A–C, MNHN PM 56, right lower jaw bearing M2–M3 and alveoli of M1. A, Occlusal stereo-view; B, labial view; C, lingual view. D–F, MNHN PM 57, left lower jaw bearing M1–M3. D, Occlusal stereo-view; E, labial view; F, lingual view.

Figure 7. Lahimia selloumi gen. et sp. nov. Detailed scanning electron micrograph views of the molars. A, B, MNHN PM56, M2–M3 in occlusal stereo-view (A), and labial view (B). C, D, holotype OCP DEK/GE 443, M1–M3 in occlusal (C) and labial views (D).

Figure 8. Lahimia selloumi gen. et sp. nov. View of the anterior part of the dentition of OCP DEK/GE 442. Alveoli with broken roots of left P2–M1. Occlusal stereo-view. Occlusal sketch of the anterior part of the dentition of OCP DEK/GE 442.

Figure 9. Comparison of the occlusal sketch of the lower molars of: A, Prototomus minimus (reconstruction; M3 in reversed view); B, Boualitomus marocanensis (reversed view); and C, D, Lahimia selloumi gen. et sp. nov. [C: MNHN PM57; D: OCP DEK/GE 443 (reversed view)].

Figure 10. Comparison of tooth length and width profiles (natural-logarithm scale in ordinate) for the three lower molars in Lahimia selloumi gen. et sp. nov. (OCP DEK/GE 443, OCP DEK/GE 442, MNHN PM56, and MNHN PM57), Boualitomus marocanensis, Prototomus minimus, and Prototomus girardoti Smith & Smith, 2001.

Figure 11. Comparison of the occlusal sketch of the lower molars of Lahimia selloumi gen. et sp. nov. (M1 and M2 of MNHN PM 57 and M1 trigonid of OCP DEK/GE 443) and the upper molars of Koholia atlasense (M1). I–V: related morphological features: see Table 7. 1–6: wear facets.

Figure 12. Preliminary tentative and informal hypothesis on the phylogenetic relationships of Lahimia selloumi gen. et sp. nov. and Koholiinae with main lineages of hyaenodontids, based on the present character study, with indications of stratigraphical and palaeogeographical distribution. This phylogenetic sketch supports an African origin of the Hyaenodontidae (e.g. Gheerbrant et al., 2006) and a significant early African radiation that remains nearly unknown and that is exemplified here by several ghost lineages [Prototomus-like lineage, Proviverra-like lineage, Limnocyoninae, Boualitomus (? = uncertain age), Koholia]. D, dispersal from Africa to Laurasia. Cimolestes is taken here as the outgroup ancestral eutherian morphotype. Node 1: Hyaenodontidae: postvallum/prevallid shearing developed (postmetacrista/ paraconid–paracristid enhanced); first molar smaller than M2–3. Node 2: Trigonid larger than talonid; postfossid slightly narrow; P4 without metaconid ridge. Node 3: P1 single-rooted; postfossid narrow; talonid cusps reduced and crestiform (but base inflated transversally), especially the entoconid. Node 4: Koholiinae (lower dentition: inferred in Koholia): mandibular symphysis anterior to P2; P1 absent; precingulid extended labially; protoconid with labial flank inflated and apex set lingually; trigonid much larger than talonid; talonid reduced and simplified (including vs. Prototomus); postfossid very narrow (including vs. Prototomus); hypoconid and hypoconulid poorly separated distally (no deep notch); reduced exodaenodonty; prevallum/postvallid shearing secondarily developed? Node 5 (lower dentition: inferred in Koholia): P2 small with mesial root reduced; paraconid large, high and well lingual; talonid short; protocone reduced (Lahimia?) metaconid reduced; trigonid extended mesiodistally.