Sivameryx moneyi Fourtau
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: 970-974
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|Sivameryx moneyi Fourtau|
Type.-CGM 30780, left dentary with p3-m3, (Fig. 3A, 3B) (also figured by Fourtau, 1920, fig. 1).
Diagnosis.-A small species of Sivameryx , length of M1-3 59 mm ( S. africanus comparable measurement 80 mm), differs from Asian Sivameryx species in having lower molar paracristid extending to lingual margin and in possessing a lingual postprotocrista on upper molars that extends distally to the transverse valley.
Occurrence.-Early Miocene, Wadi Moghra, Egypt.
Material.-CGM 30781, left dentary p3-m3 (m3 broken); CGM 39779, left dentary m3; CGM 73692, left dentary m2; CGM 73679, edentulous left dentary; CGM 84434, edentulous right dentary with symphysis; CUWM 30, left dentary, m2-3; CUWM 31, left maxilla M2-3; CUWM 64a, right maxilla P2-M3, CUWM 64b left M3; CUWM 70, right maxilla M1-2; CUWM 100a, left dentary alveoli pl-ml, crowns m2-3; CUWM 100b, left dentary m2-3; CUWM 172, skull; DPC 3421, right dentary m1-2 fragments; DPC 3932, right dentary eroded m2-3; DPC 4066, right maxilla M2-3; DPC 4067, right dentary p3-m1 (abraded); DPC 4425, right dentary m1-3: DPC 4434, right dentary with broken m3; DPC 4452, left dentary with broken m1-3; DPC 4535, right maxilla P3, P4; DPC 5968, right m3 fragment; DPC 5973, left dentary p1-2; DPC 5979, left M2; DPC 6234, left M1; DPC 6243, right maxilla P3-M2; DPC 6289, left maxilla M1-3, M1-2 broken; DPC 7281, right M2; DPC 7659, left maxilla M3: DPC 8931, right maxilla fragment; DPC 8972, right dentary p3- m3; DPC 9039, left dentary p1-dp4 roots; DPC 12538, left dentary alveolus for p1, broken crowns p2-4; DPC 12546, right dentary m2-3; DPC 12547, right maxilla P4-M1 (abraded); DPC 12605, left dentary p4-m3, m1-2 broken; DPC 12608, left dentary m1-3, m1 broken; DPC 12609, right dentary p4, m2; DPC 12610, left dentary p3-m3; DPC 12632, left M3 fragment; DPC 12940, right dentary p1-2, p4-m1, m3 abraded; DPC 14547, right dentary m2-3; DPC 14559, right dentary p1-3; DPC 17680, left dentary p4-m2; DPC 17682, left dentary m1-2; DPC 17685, left maxilla M2-3; DPC 17687, left dentary fragments; DPC 17701 right m3 fragment; DPC 17710, dentary fragments; DPC 17711, right dentary roots of p4; DPC 17714, left maxilla P4-M3, M1 and M3 broken; DPC 17742, right dentary p4-m3; DPC 21506, right maxilla M3 (Tables 1, 2).
Description.- Sivameryx has been described and discussed previously (Black, 1978; Fourtau, 1918, 1920), but most recently by Pickford (1991) who noted important distinguishing features of the genus such as: quasi-penticuspidate upper molars featuring loop-like parastyles and mesostyles, protoconule is almost fused with the protocone, canines are markedly sexual dimorphic, p2 is double-rooted, the dentition is selenodont, and the m3 talonid is loop-like and strongly obliquely oriented. Pickford (1991, p. 1511) noted that S. moneyi was mostly represented by lower jaws and the species appeared to be ‘‘ in all its known parts, merely a smaller version of S. africanus " from Gebel Zelten.
Recovery of CUWM 172, a nearly complete adult skull of S. moneyi , greatly expands our understanding of the taxon. Because the focus of this paper is on the diversity of anthracotheres found at Wadi Moghra, we provide an initial description of this Sivameryx skull here. Detailed study of the skull and its implications for larger issues involving the functional morphology , systematics, and paleobiogeography of anthracotheres in general is beyond the scope of this work.
The skull is well preserved (Fig. 4A-4D) and cranial sutures are distinct throughout allowing for clear identification of key anatomical features.
Nasal bones: the nasals are broken anteriorly but originate at anterior margin of orbit and are relatively broad posteriorly but tapering anteriorly as far as they are preserved.
Frontal bones: the frontal bones are relatively short and wide, forming the roof of the skull and comprise about two-thirds of the medial wall of the orbit. Orbital processes are broken but are presumed to have been relatively robust judging by the remaining portion of their bases. The frontals extend rostrally as bilateral narrow splints separating the caudal part of the nasals from the lacrimals. The frontal has considerable contact with the lacrimal, palatine, and orbitosphenoid but only a very small area of contact with the maxillary bone. Dorsally the frontal forms distinct ridges that sweep caudally from the orbital processes to converge towards the sagittal crest.
Orbit: the orbital mosaic is comprised of the lacrimal, maxillary, palatine, frontal, and orbitosphenoid bones, but is dominated by contributions from the frontal and palatine bones with a lesser contribution from the maxilla. The lacrimal foramen is small and located well within the orbit and the facial wing of the lacrimal extends relatively far anteriorly. The optic foramen is relatively large and enters the orbit through the orbitosphenoid. There are two smaller foramina anterior to the canal, a very small one in the frontal and a larger one formed on the maxillopalatine suture.
Parietal bones: a pronounced sagittal crest is present superiorly on the parietals, and the crest extends caudally onto the occiput where it helps form the most caudal part of the skull. The parietals are rounded laterally and demarcate a relatively small braincase that tapers anteriorly towards the parieto-frontal contact as well as caudally toward the parieto-occipital suture. Ventrally and caudally, the parietals converge to help form part of the nuchal crest, and large gutters for the temporalis muscle are found caudal and lateral to the braincase, extending along the lateral margins of the parietal and temporal bones.
Temporal bones: the temporal forms the basal and lateral portion of the braincase. The temporal extends and contacts the parietal dorsally, the orbital wing of the sphenoid rostrally, and the basisphenoid ventrally. At the juncture of the basisphenoid and temporal is the internal auditory meatus and slit-like formen lacerum medium that is continuous with that for the internal auditory meatus. The bony auditory bulla is large and bulbous, and has a distinct and elongate external auditory tube that extends caudally and dorsally, as in some suids, peccaries and hippopotami. Just rostral to the bulla is a distinct foramen ovale formed in the caudal-most aspect of the sphenoid. Caudal to the bulla is a small posterior lacerate foramen. The temporal contacts the lateral wing of the basioccipital in a relatively long dorsoventrally extend suture. The glenoid surface is flat, and almost as wide as it is long. There is a distinct postglenoid process but both an anterior process and a postglenoid foramen are absent. Dorsocaudally the temporal bone forms a robust portion of the lateral aspect of the nuchal crest.
Occipital bone: the inferior portion of the occipital is occupied by large, robust occipital condyles. Anterior and lateral to the condyles, two bony wings sweep forward to form dorsoventrally flattened surfaces. The rostral portion of these surfaces form a wall caudal and lateral to the auditory structures. These structures also extend inferiorly to form small anteroposteriorly compressed mastoids, although no stylomastoid foramina are evident. Hypoglossal foramina are present rostral to the condyles, and small but distinct jugal foramina are located inferiorly to the nuchal crest and lateral on the basioccipital.
Sphenoid bone: ventrally, the sphenoid has a distinct central ridge that continues rostrally to meet a sharply defined and high vomer. Caudally the basiosphenoid is bifurcate with bilaterally developed low processes extending caudally to the internal auditory meatus.
Maxillary bone: the maxilla is robust and forms a rostrum that is dorsoventrally relatively deep. However, the maxilla is transversely compressed just rostral to the zygoma, so that the rostrum appears relatively deep but mediolaterally fairly narrow. The rostrum is concave and narrowest superior to P4 and then broadens modestly rostrally. The concave portion of the rostrum is occupied by a small infraorbital foramen positioned superior to the posterior root of P3. From the infraorbital foramen, the maxilla extends a short distance caudally to a point superior to M3, where the bone terminates in a pointed process that is notched medially and ventrally, near where the maxilla meets the palatine. The maxilla forms the floor of the orbit and encloses the infraorbital foramen. The portion of the palate formed by the maxilla is relatively long and narrow, but not as elongate as in Afromeryx or Brachyodus. The incisive foramina are broken rostrally so their extent is hard to estimate. The caudal margin of these foramina does not extend past I2. There is a paired set of palatal foramina present at the rostral margin of P3 and a second very small pair of palatal foramina present at the rostral margin of M3.
Zygomatic bones: the rostral roots of right and left zygoma are present but most of the zygoma are absent.
Palatine bones: the palatine extends rostrally as a broad plate with a narrow central ridge until it reaches the rostral margin of M3, where it tapers to a point that extends to the rostral margin of M2. The palatine extends caudally well past the tooth row to the caudal rim of the orbit, and a distinct post-palatine process is present.
Dentition: the dentition is represented by right P4-M3, left P3 (broken), and P4-M3. All teeth except right P4 and right M3 are heavily worn. The anterior premolars are represented only by alveoli and it is difficult to be certain of homologies because supernumerary teeth were present, not only a common occurrence in Libycosaurus (Lihoreau et al., 2006; Pickford, 2006) but also in anthracotheres in general (personal observ.). The right dentition anterior to P4 has 9 alveoli. We interpret these to represent P?
(double-rooted), P1 (double-rooted), P2 (double-rooted), and P3 (triple-rooted). The left side of the palate has six alveoli anterior to P3 which we interpret to represent the homologs of the right side. Recovery of CUWM 172 confirms a number of features previously cited as characteristic of S. moneyi and also reveals some new details. The new skull confirms that P1 and P2 are double-rooted (Pickford, 1991). The occurrence of supernumerary premolars in S. moneyi has not been documented previously but extra premolars seem to be a fairly common occurrence among anthracothere species in general (personal observ.).
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