Cynelos jitu, Morlo & Friscia & Miller & Locke & Nengo, 2021
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publication ID |
https://doi.org/ 10.4202/app.00794.2020 |
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persistent identifier |
https://treatment.plazi.org/id/3F6287C1-FFB0-FF99-CA11-AD29FDC2ED85 |
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treatment provided by |
Felipe |
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scientific name |
Cynelos jitu |
| status |
sp. nov. |
Cynelos jitu sp. nov.
Figs. 5–8 View Fig View Fig View Fig View Fig , Tables 2–4.
Zoobank LSID: zoobank.org:act: E00245FD76DB403FB1251253E 68380EF
Etymology: From Swahili jitu , giant; as the taxon represents the largest known species of African Cynelos .
Holotype: KNMWS 12663, a partially crushed cranium preserving partial right and left maxillary dentitions, and an associated snout fragment. Right maxilla in two fragments, with the first fragment bearing the roots of I1, I2, I3 fragment, C fragment, root of singlerooted P1, P2–P3 alveoli, anterior root and buccal portion of P4, and the second fragment bearing the root of right M2 and the talon of M3. Left maxilla with roots of I1–I3, C alveolus, root of singlerooted P1, alveoli of P2, P3, and anterior root and buccal part of lingual alveolus of P4. Associated isolated fragments of right P4, left and right M1 talons, left and right M1 paracones.
Type locality: Buluk, Kenya.
Type horizon: Early Miocene.
Material.— Hypodigm: KNMWS 2, left lower canine; KNMWS 12621, left upper canine fragment; KNMWS 12625, left m2; KNMWS 12632, associated partial mandibles with root of left p2, roots of left and right p3–m3, and left m2 trigonid; KNMWS 12661, left mandible in two pieces with i2–i3, c, root of p2, p3, roots of p4, m1 talonid, roots of m2, and alveolus of m3; KNMWS 12870, right M3; KNMWS 49461, right mandibular fragment with roots of p4 and complete m1; KNMWS 49470, right mandible fragment with m1 fragment; KNMWS 49481, left m3; KNMWS 49495, left P2; KNMWS 49497, talon of right M1; KNMWS 49509, right m2; KNMWS 65385, right m1; KNMWS 65625, left c fragment; KNMWS 101033, right m3; KNMWS 65651, distal phalanx. All from the type locality and horizon.
Diagnosis.— Cynelos jitu sp. nov. differs from all other species of Cynelos in being much larger ( Tables 2–4), even though the North American C. sinapius is only slightly smaller. C. jitu sp. nov. differs from other species of African Cynelos ( C. macrodon , C. anubisi , and C. ginsburgi ) in having a taller m1 hypoconid, and the m2 metaconid separated from the anterior cingulid by a small notch (see Morlo et al. 2007). Further differs from C. macrodon and C. anubisi in having an m1 paraconid that protrudes more anteriorly, and further differs from C. macrodon in having a taller m2 paraconid, taller M1 hypocone, and stronger M1 hypoconule and entoconule.
Description.—Skull and upper dentition: The skull KNMWS 12663 ( Fig. 5 View Fig ) is partly crushed laterally, and this, coupled with some distortion, obscures nearly all sutures and key landmarks. Only maximum length of the cranium without snout (410 mm), and maximum width across the jugals 225 mm) can be measured with confidence. As the palatines and occipital condyles are broken, measurements of the basicranium can also only be estimated. Although the dimensions of the occiput cannot be fully assessed, the remnant of a pronounced sagittal crest is preserved, indicating a large attachment area for the temporalis muscle. The skull is broken such that the snout is not attached to the rest of the skull ( Fig. 6 View Fig ). As measured along the basicranium and including the separately measured snout, the type skull of C. jitu sp. nov. is about 450 mm long, which is longer than the basilar length of 390–440 mm reported for the North American C. sinapius ( Hunt and Stepleton 2015) .
The incisors are only represented by roots with the exception of a fragmentary right I3 that does not reveal any morphological details. Root size increases only moderately from I1–I3. Only a part of the right upper canine alveolus is preserved, and judging from the size of the alveolus, this would have been a very large tooth ( Table 3). An additional isolated upper canine, KNMWS 12621, is assigned here to C. jitu sp. nov. on the basis of its large size, and because it differs from the upper canine of H. sulzeri ( Morales et al. 2003) , the only possible alternative assignment, by possessing an anterior ridge rather than a strong anterior cusplet.
There is a diastema between P1 and P2 of about 10– 11 mm, and a shorter diastema between P2 and P3 of 3–5 mm length ( Table 3).
Both right and left P1 are preserved in the holotype, and P1 is a singlerooted and peglike tooth. A low crest runs centrally from the anteriorly placed tip of the main cusp to the posterior edge of the crown. A strong cingulum surrounds the tooth.
KNMWS 49495 is a left P2 ( Fig. 7D View Fig ). The tooth resembles P1, but the postprotocrista is longer. Although KNMWS 49495 is an isolated specimen, its two diverging roots fit perfectly into the left P2 alveoli of the holotype.
The alveoli for right and left P3 are present but the teeth are not. The P3 alveoli are located directly anterior to P4, with no diastema separating these two teeth. Due to breakage and abrasion, little information is available from the one preserved right P4 fragment. What is clear is that a low but distinct protocone is placed anterolingually, and the protocone is connected to the paracone by a faint crest. The protocone has a strong buccal cingulum, and although the metastyle is broken, it is separated from the protocone by a notch. No information about the paracone or parastyle is available, owing to the severe abrasion of the crown.
The upper first molars in the holotype skull are fragmentary, but the talons of both right and left M1s show the nearly symmetrical configuration typical of Cynelos , with a large hypocone, strong hypoconule and entoconule, and a strong lingual cingulum. The same features are also found in the partial upper molar KNMWS 49497, but the talon is longer than in the holotype ( Table 3), suggesting some size variability in the species. In both preserved M1s, the trigon is much longer than the talon, a characteristic that is also present in the much smaller upper first molars of C. macrodon from Buluk (KNMWS 49485) and C. ginsburgi from Namibia ( Morales et al. 2016).
No information is available for M2, because the tooth is represented by only a single maxillary fragment preserving an M2 posterior root. One M3, KNMWS 12870, is known from Buluk, in addition to the partial M3 preserved in the holotype. Both are similar in size, singlerooted, with symmetrical crowns, a strong lingual cingulum, and a small cusp at the lingual margin of the cingulum. The specimens differ only in that the hypocone in KNMWS 12870 is taller than in the other specimen. The M3 trigon basin is low. The lingual wall has some small cuspules.
KNMWS 12632 preserves associated right and left partial mandibles, with the right one having a length of 350 mm, while the length of the left one cannot be measured as it lacks the incisor region. The mandibular symphysis extends posteriorly to below the anterior root of p3. However, where it can be measured, the absolute length of the symphysis varies with the size of the jaw. The distance from the posterior margin of the lower canine to the anterior margin of p3 may vary between individuals (KNMWS 12661 vs. right mandible of KNMWS 12632) by up to 25% ( Table 3). The height of the mandible also varies between the individuals.
The ascending ramus rises directly behind m3, at about 45°, and a large area for insertion of the M. temporalis is present, as would be expected given the pronounced sagittal crest on the holotype skull.
On all mandibles, diastemata separate p2, p3, and p4, but the lengths of these diastemata appear to vary as much as 25% even within the same individual (KNMWS 12632, Table 4). Contrastingly, mandibular height below m2 varies not within but only between individuals (KNMWS 12632 and KNMWS 12661, Table 4) but also by about 25%.
The lower incisors are represented in KNMWS 12661 only by their roots. Judging from the size of the alveoli, there is a slight increase in size from i1–i3.
The KNMWS 12661 mandible also contains a wellpreserved canine, although this tooth is slightly broken lingually ( Fig. 8 View Fig ). The KNMWS 2 is a nearly identical isolated lower canine. Both teeth are very robust and are oval in crosssection. The enamel border surrounds the tooth at about the same height, which differs from the morphology in hyaenodonts.
None of the Buluk specimens preserve the p1 crown, but a small p2 is present in the left mandible of KNMWS 12632, and this tooth differs from the single-rooted p 2 in C. anubisi ( Morlo et al. 2019) in being double-rooted. Details of the crown morphology of p3 are unknown, as this tooth is fragmentary in KNM-WS 12661 ( Fig. 8 View Fig ). The p4 is also represented only by roots. There is no diastema between p4 and m1.
The m1 is well-preserved in KNM-WS 49461 ( Fig. 7A View Fig ), slightly damaged in KNM-WS 65385, and represented by partial talonids in KNM-WS 12661 and 49470; in KNM-WS 12632 only the roots remain. The m1 is characterized by a relatively short but anteriorly projecting paraconid, and a small metaconid, which is positioned close to the protoconid, and is located slightly posterior of the protoconid. The m1 talonid is dominated by a very high hypoconid reaching the height of the paraconid (KNM-WS 12661). Lingually, a strong entocristid is present, and in KNM-WS 49461, a faint buccal cingulid reaches from the posterobuccal corner of the tooth to the tooth’s anterior tip.
The m2 crown is preserved in three specimens (KNM-WS 12625, 12632, and 49509, Fig. 7B View Fig ), and the roots of m2 are present in one (KNM-WS 12661). All of the m2s show a slight swelling at the posterobuccal corner of the tooth, and all have a high protoconid and metaconid, both of similar height, and the paraconid is absent. The talonid on m2 displays a very high hypoconid, while the entoconid is much lower and is nearly merged into the buccal ridge. Distally on the talonid a small trough is present, and this feature reaches almost to the posterior cingulid. In contrast to other African Cynelos , the metaconid is separated from the anterior cingulid by a small notch.
Three m3 are known, within the right mandible of KNM-WS 12632, and two isolated specimens, KNM-WS 101033 ( Fig. 7C View Fig ) and KNM-WS 65651 ( Fig. 7F View Fig ). Although there is some size variability within this small sample ( Table 4), all three teeth are single-rooted, low and ovoid, with a low but broad cingulid surrounding the tooth. The only cuspid recognizable on this broad cingulid is a very low protoconid, which is connected to the lingual side of the tooth by a low crest that separates the trigonid from the talonid.
One postcranial element is attributed here to the species. This is a very large terminal phalanx (KNM-WS 65651, Fig. 7F View Fig ), which is not fissured and thus cannot to belong to a hyainailourid.
Remarks.—The presence at Buluk of an undescribed amphicyonine of outstanding size has been known for more than thirty years ( Leakey and Walker 1985; Anemone et al. 2005; Morlo et al. 2007, 2019; Werdelin and Peigné 2010). The species currently represents the largest amphicyonid known from Africa, exceeding in size even Amphicyon giganteus Schinz, 1825 , from South Africa ( Fig. 9 View Fig ). As all Cynelos , C. jitu sp. nov. further differs from A. giganteus ( Kuss 1965; Bastl et al. 2018; Siliceo et al. 2020) in having a diastema between p3 and p4, a more reduced ovoid m2, and a much lower and more reduced m3.
The hypodigm of C. jitu sp. nov. comprises the largest assemblage of individuals of an African species of Cynelos and may offer a first insight into variation in this species. However, the damage to some specimens complicates separating taphonomic distortion from individual variation, sexual dimorphism, and important functional and phylogenetic signals. There are noteworthy differences in overall size, mandibular height, and m1 metaconid height. Moreover, there are differences in the presence or absence of p2, and length of the c–p3 and p3–p4 diastemata, features varying even intra-individually in the KNM-WS 12632 mandibles, in which the length of the p3–p4 diastema is different on the right versus left sides ( Table 4). Taken together, variation in these features suggests that the premolar region may be functionally and taxonomically irrelevant, owing to the fact that upper and lower premolars do not contact each other during chewing in this species.
Among the different species of Cynelos , members of C. jitu sp. nov. most closely resemble material attributed to C. ginsburgi , due to the shared presence in these taxa of a strong anteriorly protruding m1 paraconid. In addition, both C. jitu sp. nov. and C. ginsburgi show a distinct M1 hypoconule and entoconule, in contrast to C. macrodon , which has only very weak conules.
Stratigraphic and geographic range.— Type locality and horizon only.
Family Viverridae Gray, 1821
Genus Mioprionodon Schmidt-Kittler, 1987
Type species: Mioprionodon pickfordi Schmidt-Kittler, 1987 , from the early Miocene of Songhor, Kenya.
Fig. 10 View Fig , Table 4.
Material.—KNM-WS 49500, right mandible fragment with damaged m1 crown and alveolus of m2 ( Fig. 10A View Fig , Table 4); from Buluk, east of Lke Turkana, Kenya; lower section of the Buluk Member, Bakate Formation, uppermost lower Miocene.
Description.—The mandible fragment KNMWS 49500
Fig. 10A View Fig ) has a slender body. The lingual portion of the m1 paraconid is broken, as is the cusp tip of the protoconid. Both the paraconid and metaconid are slightly shorter than the height of the protoconid. Judging by the size of the alveoli, the m 1 in this specimen is likely slightly longer than in the holotype of Mioprionodon pickfordi SchmidtKittler, 1987 , from the early Miocene of Songhor , Kenya. The short talonid basin has a single cusp, a high hypoconid, which is perched on the edge of the talonid. The second lower molar is represented only by a single root, which has a length of about 1.0 mm .
Remarks.—The typical viverrid morphology of this mandibular fragment, combined with its small size, invites comparison with the other very small African early Miocene viverrids: Leptoplesictis Major, 1903 , Mioprionodon SchmidtKittler, 1987 , and Ugandictis Morales, Pickford, and Soria, 2007 . The two similarly sized species of Leptoplesictis , L. rangwai SchmidtKittler, 1987 , and L. mbitensis SchmidtKittler, 1987 , both have a wider and more basinlike talonid, and the hypoconid is shorter than in the Buluk specimen. In Ugandictis , the metaconid and the talonid basin are larger than in the Buluk specimen. In our view, KNMWS 49500 most closely resembles Mioprionodon pickfordi from Songhor. Even so, the m1 metaconid of M. pickfordi is located more anteriorly than in the Buluk specimen, and the m2 of M. pickfordi is larger. The same characters also distinguish KNMWS 49500 from Mioprionodon hodopeus Rasmussen and Gutierrez, 2009 . Due to the fragmentary nature of the specimen we refrain from a specific allocation. Better material may reveal whether KNMWS 49500 represents a new species of Mioprionodon or a new genus of viverrid.
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