Jaggermeryx naida

Miller, Ellen R., Gunnell, Gregg F., Gawad, Mohammad Abdel, Hamdan, Mohamad, El-Barkooky, Ahmed N., Clementz, Mark T. & Hassan, , 1914, Anthracotheres from Wadi Moghra, early Miocene, Egypt, Journal of Paleontology 88 (5), pp. 967-981: 977-978

publication ID

10.1666/13-122

persistent identifier

http://treatment.plazi.org/id/CFCFC1FF-D1AC-DB6F-9DB7-FFC57307965D

treatment provided by

Donat

scientific name

Jaggermeryx naida
status

new species

Jaggermeryx naida  new species

Type.-DPC 2499, left dentary, alveoli i3-c, and partial crowns of p2-4 (Fig. 6A-6C).

Diagnosis.-Differs from all other anthracotheres in having multiple (six to ten) mental foramina present on both sides of the symphysis, inferior boarder of symphysis inflected inferiorly. Further differs from Brachyodus in having dental formula 3.1.3.3, and lacking specializations of the anterior dentition such as suppression of i1-2, or development of a tusk-like i3. Differs from Afromeryx  in having a deeper mandibular symphysis and in lacking p1. Further differs from Sivameryx  in being of larger size, and in having a bunodont rather than selenodont dentition.

Description.-The most characteristic feature of this taxon is the presence of multiple mental foramina. These foramina vary in size, but extend posteriorly from below i1/i2 to p4, most typically with four in a rhomboid configuration under i1-3, two superiorly and two inferiorly, and with the medial and inferior foramen much larger than the other three. Three additional foramina are usually present below c-p2, and at least one is positioned below p4. The symphysis is unfused, rugose, heavily constructed and broad across its base but tapers superioanteriorly. interestingly, although the symphysis remains unfused, one specimen (CUWM 115) shows an anomaly whereby plastic deformation during fossilization pressed the right and left mandibular halves together in such a way that, at first glance the specimen appears to have four left incisors and two right ones. The ventral boarder of the symphysis in J. naida  curves slightly ventrally so that the symphysis is angled ventrally at about 45-48°. The symphysis (see Fig. 6D) can be twice as deep in males (~65-80 mm) as in females (~42 mm).

Incisor alveoli are of approximately equal size, although in some cases the i3 alveolus is slightly larger than for i1-2, and is about the same size as the canine alveolus. Small diastemata separate alveoli of i1-3 (~3 mm), and i3-c (9 mm). The species is sexually dimorphic with females having a shallower symphysis and a shorter c-p2 diastema (ranging from ~ 16-21 mm, e.g., CUWM 1578b), and males having a deep symphysis and a c-p2 diastema up to twice the length of that seen in females (~45 mm, e.g., CUWM 115).

As represented on the type specimen, some but not all individuals attributed to this taxon have an unusual morphology associated with the anterior dentition, whereby the lower incisors and canine seem to be ‘‘perched’’ on the lateral edge of the dentary rather than situated perpendicular to the cheek tooth row (Fig. 6C). Also, where known, lower i1-2 alveoli are slightly procumbent anteriorly, and i3 is procumbent anterolaterally. One explanation for the ‘‘splay’’ of the lower anterior teeth is that, in addition to the normal cropping function of artiodactyl incisors, the anterior dentition may have had a scoop-like or sieve-like function.

Etymology.-" Naida’’ derived from the Greek “Naias,” waternymph , in recognition of the species’ semi-aquatic habitat.

Material.-CGM 30775, edentulous left dentary symphysis, alveoli for i2-3,c, p2-4; CGM 30885, right symphysis fragment; CGM 83752, left dentary alveoli i3-c, roots of p2-3, partial roots of p4; CUWM 115 edentulous dentary complete symphysis, alveoli left i1-p2, alveoli right i1-p2; CUWM 157a, b right dentary p3-4, m3; DPC 17702, right symphysis fragment; DPC 17738, right dentary alveoli i1-3,c, p2-4 (Table 1).

Remarks.-The type specimen of J. naida  preserves only part of the premolar series and is otherwise edentulous as is most of the hypodigm, which is less than desirable. However, all of the specimens assigned to J. naida  show a number of distinctive morphologies that individually-and certainly collectively-are unknown among other anthracothere taxa.

Interestingly, one of the J. naida  specimens has been known for a long time because it was figured in Fourtau (1920, Fig. 31) as an unnumbered dentary of Brachyodus africanus  . Pickford (1991) subsequently included this specimen as part of the hypodigm of B. mogharensis  , but we assign this specimen here (now carrying the number CGM 30775) to J. naida  , owing to the presence of multiple mental foramina arranged in the characteristic pattern, as well as the unusual canted morphology of the symphyseal region. When only one unnumbered specimen collected almost a century ago was known, it was possible to consider the unusual morphology as representing idiosyncratic variation. However, sustained collecting efforts at Moghra over the last decade have recovered additional specimens with the same unusual morphology , making clear that these specimens represent a new anthracothere taxon.

The occurrence of a large number of mental foramina present bilaterally in this species is unique among the Moghra anthracotheres. Because the mental foramen transmits the mental nerve, which provides sensory innervation to the chin and lower lip, we interpret the morphology of J. naida  as indicating that the animal must have had either a very sensitive lower lip or an acutely sensitive tactile snout, perhaps combined with perceptive vibrissae. Also, the spacing of the lower incisor alveoli, and the fact that the symphyseal region shows slight splay anteriorly, suggests that the anterior lower dentition may have functioned as a kind of scoop-like or sieve-like structure. This morphological information, together with sedimentological data showing that the Moghra deposits formed under wet conditions, and preliminary results from stable isotope analyses indicating that many of the Moghra anthracotheres, including J. naida  , were semiaquatic, leads to the conclusion that J. naida  may have foraged along the river banks, using its sensitive tactile snout, and employing the lower anterior teeth in a cropping and scoop-like fashion.