The Aramis Member (Sagantole formation) includes the Gàala Tuff Complex-Daam Aatu Basaltic Tuff interval which has produced a taxonomically diverse vertebrate assemblage including the primitive hominid Ardipithecus ramidus. New Eucyon remains recovered from this interval come from localities in the Aramis, Sagantole, and Kuseralee catchments. The chronology established for the GATC-DABT interval is 4.4 Ma. These recoveries represent the most abundant available Eucyon assemblage of the eastern African Pliocene. Here, Eucyon fossils from the Kapsomin and Lemudong’o Late Miocene Kenyan sites are compared with the Aramis representatives, showing comparable morphology although with smaller dimensions. E. intrepidus–E. wokari nov. sp., might constitute a single lineage, with increasing size and robusticity, and the derivation of some morphological traits mainly on the lower carnassial. E. wokari represents a new eastern species of the African Pliocene Eucyon lineage.
Nouveaux restes d’Eucyondans le Membre Aramis pliocène (Formation Sagantole) de la moyenne vallée de l’Awash (Éthiopie). Le membre Aramis de la formation Sagantole inclut le « Gàlaa Tuff Complex-Daam Aatu Basaltic Tuff interval » qui a livré un ensemble varié de vertébrés, y compris l’hominidé primitif Ardipithecus ramidus. De nouveaux restes d’Eucyon récoltés dans cet intervalle proviennent de localités des stations d’Aramis, Sagantole et Kuseralee. L’âge de l’intervalle est de 4,4 Ma. Ces découvertes représentent l’échantillon numériquement le plus important du Pliocène d’Afrique de l’Est. Les restes d’Eucyon des sites du Miocène supérieur kenyan, Kapsomin et Lemudong’o, sont comparés à ceux d’Aramis, montrant une morphologie comparable, mais une taille plus faible. E. intrepidus et E. wokari n.sp. pourraient constituer une seule lignée, avec un accroissement de taille et une augmentation de robustesse, ainsi que quelques modifications morphologiques surtout sur la carnassière inférieure. E. wokari est une nouvelle espèce orientale dans la lignée des Eucyon du Pliocène africain.
Canidae, Eucyon, Mio-Pliocene, Aramis, Middle Awash, EthiopiaCanidae, Eucyon, Mio-Pliocène, Aramis, Aouache moyen, ÉthiopiepresentedWritten on invitation of the Editorial BoardIntroduction
During the last decades, new canid material from the African Mio-Pliocene has increased our knowledge of the evolutionary history of this family. The idea that the first record of canids from eastern Africa was around 4–4.5 Ma was widely accepted until recently [10]. A newly recognized species, Eucyon intrepidus, from the Lukeino Formation, Baringo, Kenya [4 (p. 48)] is the first nominate species of Eucyon from Africa. Its diagnosis is mainly based on the small size of two upper first molars (BAR 2127’01 and BAR 719’02). Additional material recovered from Lemudong’o, Narok District, Kenya, consists of an upper first molar (KNM-NK41284) and a fragmentary lower first molar (KNM-NK 41285) assigned to this species [3]. This provided new knowledge on the morphology of this small Eucyon species. However, the African record of this canid species remains scant.
The published indications regarding the Lukeino Formation and Lemudong’o Late Miocene Kenyan sites considerably deepen the initial immigration of Eucyon into Africa, implying an expansion from Eurasia earlier than previously thought.Younger, about mid-Pliocene age occurrences of several canid taxa, including Canis sp., are reported from Laetoli (Tanzania) [1] and South Turkwell (Turkana, northern Kenya) [9]. In the latter instance, gnathic and several postcranial parts definitely attest to the genus Canis (Canis sp. nov. A of the authors, pp. 1176) at 3.5 Ma. In the former instance, incomplete cranio-dental and various postcranial remains are attributed to aff. Canis brevirostris (Ewer) by Barry [1 (pp. 237–240)], with a size comparable to extant Nyctereutes. This material exhibits features found within the morphometric range of Eucyon[6] and at a substantially younger mid-Pliocene age than the previously discussed Kenyan localities. The Langebaanweg (South Africa) cf. Eucyon[2] and [7] might represent a separate form with more robust upper molars (Morales, personal communication). AT 4.4 Ma, the Eucyon finds from the Aramis Member therefore play an important role in characterizing the evolution and spread of canids in Africa during the Mio-Pliocene.
Geology and location of the canid remains
The Ethiopian rift system comprises the Afar Depression, the Main Ethiopian Rift, and a wide rifted zone located in the Southwest of the country. The Central Awash Complex is a domelike horst located in the southwestern Afar rift and includes the Sagantole Formation with alluvial and volcanic sediments, tephras and basaltic lavas exposed. One of the Sagantole Members, Aramis, includes a thin stratigraphic interval between the Gàala Tuff Complex and the Daam Aatu Basaltic Tuff (GATC-DABT). This effectively isochronous, largely terrestrial unit has produced a taxonomically extensive vertebrate assemblage including the primitive hominid Ardipithecus ramidus[5] and [11].
The base of the Aramis Member is defined by the Gàala (camel) Tuff Complex (MA92-12), a 0.5–2-m thick, crystal-vitric tuff. The GATC variably overlies conglomerates and/or brown to orange silty clays of the underlying Haradaso Member. The Daam Aatu (baboon) Basaltic Tuff (MA92-38B) crops out a few centimetres to ∼5 m above the GATC. The DABT ranges in thickness from a few centimetres to ∼1 m. It is a poorly consolidated tuff composed chiefly of bedded and laminated dark grey basaltic glass lapilli and scoria in its lower third (∼15–20 cm). This tuff was deposited subaerially on a remarkably flat landscape and was not reworked. WoldeGabriel et al. [12] reported 40Ar/39Ar results and uniform chemical data on glass from different outcrops of the DABT. The DABT occurs in close association with the GATC along the eastern half of the Central Awash Complex. The chronology established for the GATC-DABT is 4.4 Ma [5].
The carnivore assemblage within the GATC-DABT interval comprises at least 14 species, Canidae (one species), Felidae (five species), Viverridae (one species), Herpestidae (at least three species), Hyaenidae (two species), Ursidae (one species), Mustelidae (one species). The canid remains are described below as Eucyonwokari nov. sp, a new, small to medium size Eucyon species. These finds come from the Aramis member (Sagantole Fm.) (GATC-DABT) from vertebrate paleontology localities: ARA-VP-1,-16, -17 and KUS-VP-2; and belong to a minimum of three different individuals. These remains are of special relevance given the scarce evidence of Eucyon at African sites during the Early Pliocene.
Description of the new speciesSystematic paleontology
Class mammalia Linnaeus, 1758
Order carnivora Bowdich, 1821
Infraorder cynoidea Flower, 1869
Family canidae, Gray, 1821
Subfamily caninae Fischer von Waldheim, 1817
Genus Eucyon,Tedford and Qiu, 1996
Eucyon wokari sp. nov.
Type specimen: right mandible fragment with M1–M2 (ARA 6/21; Fig. 1).
Measurements (in millimetres). Holotype (ARA VP6/21): greatest length of m1 = 13.6; greatest breadth of m1 = 6; greatest length of m2 = 7.8; greatest breadth of m2 = 5.4; greatest length of molars (m1–m2) = 21.4.
Other material: right m2 (KUS VP-2/73) and left m2 (KUS VP-2/198) (Fig. 2); maxillary fragment (KUS VP-1/197; Fig. 3) with P4-M2; left upper C (ARA VP-1/2112); left (talon) of M1 (ARA1/137); left half of a femur – distal – (ARA 6/22); right half of a humerus –distal (ARA 1/89); left proximal second metacarpal (ARA-VP-1/322).
Derivatio nominis: this canid is the size of a jackal and wokari is the name of the jackal in the local Afar language. The holotype and all other material is housed at the Ethiopian National Museum (Addis Ababa, Ethiopia).
Locality: Aramis and Kuseralee.
Horizon and associations: all the Eucyon specimens were located in the GATC-DABT interval. The chronology established for the GATC-DABT interval, from where the canid remains were recovered, is 4.4 Ma [5].
Differential diagnosis: E. wokari differs from E. monticinensis and E. davisi in a subtriangular outline of the M1 compared with the quadrangular one observed in the Eurasian species. When compared to E. intrepidus, the m1 of E. wokari presents a more robust metaconid. It also shows a more robust talonid with additional differences: a more massive and pyramidal-shaped hypoconid. It presents a well-marked oblique crest, a posterior protoconid cristid oriented postero-buccally (parallel to the buccal margin), and an internal cristid that joins a simple metaconid. A tiny and very low hypoconulid can be distinguished, isolated from the other two cuspids, resulting on a posterior open valley.
Description of the dental material assigned to <italic>Eucyon</italic>
Maxillary fragment (KUS-VP-1/197) with P4–M2; right mandible fragment with M1–M2 (ARA-VP-6/21); right m2 (KUS-VP-2/73); left m2 (KUS-VP-2/198); left C0 (ARA-VP-1/2112); left (talon) of M1 (ARA-VP-1/137). On the basis of the locality where the remains were found and additional dental criteria, a minimum number of three adult individuals was calculated; one each from Aramis VP-1, -6 and Kuseralee VP-2.
The morphology and size of the dentition is mostly comparable to the samples attributed to the genus Eucyon[8]. A comparison of dimensions in such samples and the Aramis dental material is presented in Table 1.
Upper teeth
KUS-VP-1/197 is a left maxillary fragment that preserves the posterior portion of a third premolar, a broken carnassial with missing protocone and damaged blade, a well preserved upper first and second molar (partially worn), and a broken alveolous of an M3 (Fig. 3).
The M1 of KUS-VP-1/197 is robust, with larger dimensions than the small E. intrepidus. It falls within the smallest E. davisi (one individual), but is still smaller than all the Eurasian species (Table 1 and Fig. 4).
The Lukeino (BAR 212’01) and Lemudong’o (KNM-NK 41284) M1s present an almost identical pattern, for what the original attribution E. aff. intrepidus[3] should be now considered as E. intrepidus.
The M1 of KUS-VP-1/197 (Fig. 3) has a subtriangular shape, a slightly incurved distal crown border, a well-developed buccal cingulum, and a distinct parastyle. Paracone and metacone are subequal, not very high, and pyramidal. The well-developed protocone and metaconule join in the middle, creating one continuous wear facet connected mesially to the parastyle and distally to the buccal cingulum. An anterior cingulum is present, and a postero-lingual cingulum is stronger and is as high as the protocone (looking like an hypocone). A deep fissure, open mesio-distally, separates this hypocone-like elevation from the area formed by the trigon cusps and connected by crests.
The M2 of KUS-VP-1/197 (Fig. 3) follows the same subtriangular outline as the M1, with subequal paracone and metacone and evident buccal cingulum. No parastyle is observed. The protoconid is well developed and is joined to a tiny but distinguishable metaconule. The postero-lingual cingulum is large. In general the M2 shows a very similar morphology to the M1.
No M2s have been recorded from Lukeino or Lemudong’o, and this molar is also absent from the published material from Langebaanweg. Its morphology remains unknown for E. intrepidus and for the African record.
The Aramis specimen differs from E. davisi in displaying a subtriangular outline rather than the quadrangular shape seen in the North American Eucyon.
Lower teeth
ARA-VP-6/21 is a right mandible fragment with m1–m2, and the mesial part of the alveolus of an m3 (Fig. 1). The m1 is incomplete, lacking part of the mesio-lingual (paraconid) portion of the trigonid. It shows scant wear. In order to compare this fossil with E. intrepidus, we have used the specimen described from Lemudong’o (KNM-NK 41825) [3] because no m1 was found at the type locality (Lukeino). The mesiolingual portion of the trigonid is also missing in this m1, but the rest is well preserved, and the wear stage between both molars is similar.
The m1 of ARA-VP-6/21 has a salient protoconid with the usual steep, sub-vertical distal slope to the talonid. There is a distinct but low buccal cingulum at the base of the protoconid. The buccal side of the protoconid expands, showing a well-rounded profile that differs from E. intrepidus from Lemudong’o, in which it drops vertically. The metaconid is distinct, enlarged, and disto-lingually offset from the back of the protoconid. The talonid is broad and bears a marginal hypoconid, and a larger, very robust, more posterior, and simple marginally placed entoconid (differing from E. intrepidus from Lemudong’o). These cusps are connected by a tiny cristid. The posterior-most part of the talonid basin is simple (minute hypoconulid) and is placed apart from the entoconid and hypoconid. In E. intrepidus, the talonid presents a small hypoconulid constricted by the entoconid and hypoconid, closing the molar posteriorly. The lingual outline of the talonid is almost straight (differing from Lemudong’o, which is slightly convex) and the buccal outline is slightly incurved between the protoconid and hypoconid (but does not show any constriction evident in the Lemudong’o specimen).
The m2 of ARA-VP-6/21 is also scarcely worn, and presents a strong labial cingulum, a double entoconid, and a high protoconid (Fig. 2).
Two more m2s have been recovered from the Aramis Member: KUS-VP-2/198 is a left m2 and KUS-VP-2/73 is a right m2. Both specimens present a considerable wear stage and show a similar morphological pattern that could include them within the same individual. The pattern observed in these two molars is identical to the one on place (ARA-VP-6/21). Second lower molars are not represented in any of the sites with E. intrepidus, so comparisons with this species are not possible.
Comparisons and discussion
The M1 of E. monticinensis[6] is not only more robust and quadrangular-shaped than any African representatives, but also presents a very straight buccal side, rather than rounded, with a constriction dividing paracone and metacone. E. minor also presents larger dimensions, with subequal protocone and metacone and very pronounced parastyle [7], differing from the African forms.
E. wokari differs from E. intrepidus (Kapsomin and Lemudong’o) by its larger dimensions in all molars which are still smaller than the Eurasian species and E. davisi. Furthermore, the M1 shows a paracone subequal to metacone, and smaller relative heights of the buccal cusps (which are higher and sharper in E. intrepidus, especially in the paracone). The differences with E. intrepidus from Lemudong’o lie in the lower carnassial, related not only with the distinct robustness, but with some specific traits observed in the talonid. Together, these indicate that a different species of Eucyon was present in the Pliocene of Ethiopia.
The Eucyon remains identified in GATC-DABT comprise at least three individuals, described here as a new species, based mainly on differences detected on the lower carnassial, and on intermediate dimensions between the larger Eurasian Eucyon species and the small E. intrepidus. Generally, the molars of the Aramis canid are more heavily built, and all cusps are more robust, which brings the idea of a robusticity increase during the Mio-Pliocene. Differences in the upper first molar within this proposed African lineage are less evident, although the two E. intrepidus (coming from different Late Miocene sites) present a pattern which is somewhat different than the Aramis one, especially in the high, sharp and unequal metacone and paracone, compared to the subequal, low cusped condition observed in E. wokari.
Morphological differences are even clearer in the lower carnassial, when comparing the Aramis fossil and E. intrepidus from Lemudong’o. All cusps show a more robust pattern in E. wokari, but also display a different talonid pattern from its likely forerunner Miocene species.
The remains from Aramis represent, up to date, the most abundant Eucyon assemblage of the East African Pliocene. E. wokari might represent a new eastern African chronospecies of this canid lineage that inhabited during the Pliocene and further morphological analyses will considerably improve our knowledge of this group. The Langebaanweg (South Africa) cf. Eucyon (Hendey 1974, Rook, 1993) might represent a separate form, although deeper analyses are needed to understand the full pattern of Eucyon relationships and its evolution in Africa.
Acknowledgements
The Middle Awash Project involves a number of individuals who conducted the Middle Awash fieldwork, who must be especially thanked for their participation on survey and excavations. The Authority for Research and Conservation of Cultural Heritage provided permits to fieldwork and access to the collections in the Paleoanthropology Laboratory of the National Museum of Ethiopia. Alemu Ademassu is thanked for assistance and management during the study of the collections at the National Museum of Ethiopia. The Middle Awash paleoanthropological research project is funded by the U.S. National Science Foundation (NSF) (BCS-9910344). F.C. Howell guided me to study the Middle Awash carnivore collections during my postdoctoral stay in the Human Evolution Research Centre, and supported me in all senses: comments, advice, and open access to his outstanding library. I have received an excellent assistance and care during all my stays at the University of California, Berkeley, at the Museum of Vertebrate Zoology and at the Museum of Paleontology, which provided me with helpful casts of E. davisi types.
I am indebted to Berhane Asfaw and Tim White who gave me the additional opportunity to study the Middle Awash carnivore material. Jorge Morales was extremely supportive, providing very valuable advice and discussion on the analysis, with comments and fossil material for comparison that helped to clarify the arguments exposed in this study. I also thank my colleagues Mark Goodwin, Leslea Hlusko, and Henry Gilbert, from UC Berkeley, and Yohannes Haile-Selassie, for assistance and discussions. I thank also the project Revealing Homind Origin Initiative (RHOI) of the NSF for funding the workshop at Poitiers.
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Buccal (a), lingual (b) and occlusal (c): ARA-VP-6/21 right mandible fragment with m1–m2 of Eucyon wokari; (d): ARA-VP-6/21 right m1 (Aramis, Ethiopia); (e): KNM-NK-41285 left m1 of E. intrepidus (Lemudong’o, Kenya).
Fig. 1. Vues buccale (a), linguale (b) et occlusale (c) : ARA-VP-6/21, fragment de la mandibule droite avec m1–m2 de E. wokari ; (d) : m1 droite : ARA-VP-6/21 (Aramis, Éthiopie) ; (e) : m1 gauche : KNM-NK-41285 de E. intrepidus (Lemudong’o, Kenya).
Occlusal (a) and buccal (b): KUS-VP-1/197 left maxillary fragment of Eucyon from Aramis, with a partial P3, a broken P4, M1, M2 and alveolous of M3; (c): UCMP 545 left maxillary fragment with M1–M2 of E. davisi (holotype) from Rattlesnake; (d): right M1 of E. intrepidus from (right) Lukeino (BAR 212’01 holotype) and (left) Lemudong’o (KNM-NK 41284). Scale bar 1 cm.
Fig. 3. Vues occlusale (a) et buccale (b) : KUS-VP-1/197 : fragment de maxillaire gauche de Eucyon en provenance d’Aramis, avec une P3 partielle, une P4 cassée, M1, M2 et une alvéole de M3 ; (c) : UCMP 545 : fragment de maxillaire gauche, avec M1–M2 de E. davisi (holotype) en provenance de Rattlesnake ; (d) : M1 droite de E. intrepidus en provenance de Lukeino, pour la droite (BAR 212’01 holotype) et de Lemudong’o (KNM-NK 41284) pour la gauche. Barre d’échelle 1 cm.
Plot of length/breadth relationship of upper M1 of Eucyon species. Data for E. intrepidus (Lukeino) are from [4], for E. aff. intrepidus (Lemudong’o) from [3], for E. monticinensis (Brisighella and Venta del Moro) after [6], for E. davisi and E. odessanus are from [7], for E. minor are from [8] and for Langebaanweg are from [1]. All reported measurements are in millimetres.
Fig. 4. Relations longueur–largeur de la M1 supérieure de l’espèce Eucyon. Les données pour E. intrepidus (Lukeino) proviennent de [4], pour E. aff. intrepidus (Lemudong’o) de [3], pour E. monticinensis (Brisighella and Venta del Moro) d’après [6], pour E. davisi et E. odessanus de [7], pour E. minor de [8] et pour Langebaanweg de [1]. Toutes les mesures reportées sont indiquées en millimètres.
Comparison of upper dental dimensions in Eucyon.
Tableau 1 Comparaison entre les dimensions des dents supérieures d’Eucyon.
E. wokari nov. sp. (Aramis) KUS VP1/197E. aff. intrepidus (Lemudong’o) KNM NK 41284E. intrepidus (Lukeino) BAR 2127’01E. intrepidus (Lukeino) BAR 719’02E.monticinensis (Brisighela) BRS24/12E. monticinensis (Venta del Moro) ILM VM1-VM5E. davisi (average)P4Length12.816.716.4M1Width12.68.069.39.613.712.712.8Length10.111.61112.71211.210.8M2Width9.49.29.1Length6.36.86.9Length P4–M227.2Length M1–M216.3