Journal of Vertebrate Paleontology Nyctereutes lockwoodi, n. sp., 2016-11-03¢ 982 JOURNAL...
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Nyctereutes lockwoodi, n. sp., a new canid (Carnivora: Mammalia) from the middle Pliocene of Dikika, Lower Awash, Ethiopia Denis Geraads; Zeresenay Alemsegeda; René Bobeb; Denné Reedc a Department of Anthropology, California Academy of Sciences, San Francisco, California, U.S.A. b
Department of Anthropology, University of Georgia, Athens, Georgia, U.S.A. c Department of Anthropology, University of Texas at Austin, Austin, Texas, U.S.A.
Online publication date: 19 May 2010
To cite this Article Geraads, Denis , Alemseged, Zeresenay , Bobe, René and Reed, Denné(2010) 'Nyctereutes lockwoodi, n. sp., a new canid (Carnivora: Mammalia) from the middle Pliocene of Dikika, Lower Awash, Ethiopia', Journal of Vertebrate Paleontology, 30: 3, 981 — 987 To link to this Article: DOI: 10.1080/02724631003758326 URL: http://dx.doi.org/10.1080/02724631003758326
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Journal of Vertebrate Paleontology 30(3):981–987, May 2010 © 2010 by the Society of Vertebrate Paleontology
NYCTEREUTES LOCKWOODI, N. SP., A NEW CANID (CARNIVORA: MAMMALIA) FROM THE MIDDLE PLIOCENE OF DIKIKA, LOWER AWASH, ETHIOPIA
DENIS GERAADS,*,1 ZERESENAY ALEMSEGED,2 RENÉ BOBE,3 and DENNÉ REED4; 1UPR 2147 du CNRS, 44 rue de l’Amiral Mouchez, 75014 Paris, France, firstname.lastname@example.org; 2Department of Anthropology, California Academy of Sciences, San Francisco, California 94118, U.S.A. , email@example.com; 3Department of Anthropology, University of Georgia, Athens, Georgia 30602, U.S.A. , firstname.lastname@example.org; 4Department of Anthropology, University of Texas at Austin, Austin, Texas 78712, U.S.A. , email@example.com
The Dikika Research Project (DRP), led by one of us (Z.A.), explores Lower Pliocene to early middle Pleistocene sediments in the Lower Awash Valley, Ethiopia, mostly on the right bank of the Awash River, south of the sites of Hadar and Gona (Ger- aads et al., 2004; Alemseged et al., 2005, 2006; Wynn et al., 2006, 2008). In the eastern part of the DRP area, exposed on the right side of the Awash River, the exposures belong primarily to the Sidi Hakoma and Basal Members of the Hadar Formation, which range in age from >3.8 to
982 JOURNAL OF VERTEBRATE PALEONTOLOGY, VOL. 30, NO. 3, 2010
FIGURE 1. Nyctereutes lockwoodi, skull DIK-31–1 in A, lateral, B, dor- sal, C, ventral, and D, postero-ventro-lateral views. Scale bar equals 5 cm.
Of the incisors, only the bases of the right I2 and I3 are pre- served. The latter is significantly larger than the former, and separated from it by a short diastema. The tips of the canines are missing but these teeth were mesio-distally short and, from the convergence of their mesial and distal borders, it can be deduced that they were low-crowned. The anterior premolars are small, simple, and separated by long diastemas. P1 is peg-like, with no hint of a distal cusp. An incipient distal cusp is present on P2, and is more distinct on P3, but remains weak. The carnassials and molars are also small relative to skull size. P4 is almost twice as long as P3; its protocone extends farther mesially than the para- cone, but the mesial border of the tooth is not concave in occlusal view, and is surrounded by a well-marked cingulum. All premo- lars are slightly worn, but most of the crown of M1, lingual to the paracone and metacone, is worn off. These cusps are sub-equal in size; labially, they are bordered by a continuous cingulum. M2
TABLE 1. Cranial measurements (in mm) of Nyctereutes lockwoodi.
E1 Condylo-basal length 143.2 — E7RA6 Length from rostrum to
rear of M2 74.8 —
RA4 Length of nasals 53 — RA21 Length from orbit to
infra-orbital foramen 11.5 —
E17RA12 Bi-mastoid width 52.2 — E18RA10 Bi-condylar width 29.8 — E21RA9 Bi-zygomatic width 77.6 — E22RA15 Width over post-orbital
constriction 31 —
E24RA14 Width over post-orbital processes
E25RA13 Minimum bi-orbital width 27 28.4 E9RA8 Length P4–M2 27.2 28.3 RA5 Length P1–M2 52 ca. 52
The first column is the measurement number in Eisenmann and van der Geer, 1999 (E), and/or in Rook and Azzaroli-Puccetti, 1996 (RA).
FIGURE 2. Nyctereutes lockwoodi, mandible DIK-1–22: A, photo- graphic reconstruction based upon left (to the right of the dashed line) and right pieces, lateral view; B, detail of the angular process, medial view, with muscle scars for the superficial part of the medial pterygoid (1), and for its deeper part (2). Scale bar equals 2 cm.
FIGURE 3. Nyctereutes lockwoodi, incomplete skull DIK-70–2, occlusal view of P4–M2. Scale bar equals 2 cm.
TABLE 2. Tooth measurements (in mm) of Nyctereutes lockwoodi.
P1 P2 P3 P4 M1 M2
L W L W L W L ext L max W L W perp W max L W
DIK-31–1 4.0 2.7 6.7 2.8 7.5 3.5 12.2 13.6 6.0 9.2+ 11.9 13.1 6.6 8.5 DIK-70–2 — — — — — — 12.4 13.1 6.2 10.6 12.1 13.4 6.2 8.6
D o w n l o a d e d B y : [ S m i t h s o n i a n I n s t i t u t i o n L i b r a r i e s ] A t : 1 4 : 4 9 2 8 J u n e 2 0 1 0
SHORT COMMUNICATIONS 983
is also much worn and rather large compared to M1. Tooth mea- surements are given in Table 2.
The partial skull DIK-70–2 is less complete than DIK-31–1, but its molars are well preserved and unworn (Fig. 3). We refer it to the same species, as most of its features match those of the holo- type: (1) overall size is comparable, and measurements are simi- lar (Table 1); (2) the post-orbital processes are strong and salient, with a hint of a dorsal depression, but they are well inflated, and a break across the frontals shows them to be extensively pneu- matized; (3) the posterior border of the zygomatic arch descends above the posterior root of M2, instead of anterior to it as in most canids; and (4) the infra-orbital foramen opens immediately in front of the anterior root of P4, and is closer to the orbit than it is in most canids.
Differences from the holotype are that: (1) the temporal lines form a low sagittal crest; (2) the orbit is less anterior with respect to the tooth-row, so that the distance between it and the infra- orbital foramen is greater than in the type; and (3) the protocone of P4 is extremely small, being in fact little more than a slight inflation at the base of the paracone.
The molars of DIK-70–2 are large relative to the carnassial. The M1 is not much broader than it is long, with only a shallow distal concavity; the paracone and metacone are low and sub- equal, both in surface and height and are bordered by a strong labial cingulum. The crescent-shaped hypocone is thick and ex- tends mesially and distally into a faint cingulum. Paracone and metacone are also of similar size on M2, and the hypocone of this tooth is also large.
The teeth of the mandible pieces DIK-1–22 (Fig. 2) are too worn to offer any useful detail, except that the metaconids of m1 and m2 are still high, but the occurrence of a cristid between hypoconid and entoconid of m1 cannot be ascertained. The m3 is represented by its alveolus only. This mandible is remarkable for the expansion of the sub-angular area, as occurs in some other fossil and modern canids where its role is to provide a larger area for insertion of the digastric muscle. In DIK-1–22, it can be called a lobe, but is less expanded than it is in modern Nyctereutes or Otocyon. Although the incomplete nature of the mandible precludes precise orientation, it is also clear that the anterior edge of the ascending ramus is less vertical than it is in normal canids. However, on the medial side of the rather large angular process (Fig. 2B), the (ventral) scar for the insertion of the superficial medial pterygoid is large, as it is in canids with a sub-angular lobe, whereas it is narrower than the (dorsal) scar for the deeper part of this muscle in normal canids (Gaspard, 1964; Tedford et al., 1995).
There is no definite evidence that DIK-1–22 belongs to the same species as DIK-31–1, but they were found not far from each other in the same layers, they match in size and articulate satis- factorily, and the sub-angular lobe of the man