Scontromeryx apruthiensis ( Mazza et Rustioni, 2011 )

Van Der Geer, Alexandra A. E., 2014, Systematic revision of the family Hoplitomerycidae Leinders, 1984 (Artiodactyla: Cervoidea), with the description of a new genus and four new species, Zootaxa 3847 (1), pp. 1-32 : 18-20

Scontromeryx apruthiensis ( Mazza et Rustioni, 2011)

Hoplitomeryx Leinders, 1984 — Mazza & Rustioni 1996: p. 95 [SCT16, SCT29, SCT50].

Hoplitomeryx sp. Leinders, 1984 — Mazza & Rustioni 1999: p. 305, fig. 1 [SCT16, SCT29, SCT50, SCT58, SCT59, SCT71, SCT81, SCT89, SCT102, SCT125, SCT195].

Taxon B—Mazza & Rustioni 1999: p. 307, fig. 2 [SCT51, SCT67, SCT79].

Hoplitomeryx apruthiensis Mazza & Rustioni, 2011 — Mazza & Rustioni 2011 (partim): p. 1304, 1322, 1330, fig. 4, 5, tables 1, 2 [SCT16, SCT29, SCT50, SCT51, SCT58 + SCT67, SCT59, SCT71, SCT79, SCT81, SCT89, SCT102, SCT125, SCT195].

Holotype. Right hemimandible SCT29 ( Figure 4 , D, E, F in Mazza & Rustioni 2011).

Paratypes. Maxillaries SCT59, SCT125; mandible fragments SCT16, SCT50, SCT51, SCT58 + SCT67, SCT79, SCT71, SCT81, SCT89, SCT102, SCT195.

Original diagnosis. See Mazza & Rustioni (2011).

Revised diagnosis. Parastyle and mesostyle very robust and paracone supported by prominent median rib. Weak external rib of metacone and weak metastyle. Upper molars very similar to one another, with trapezoidal, closely packed lingual crescents. Protocone somewhat smaller than metacone. Tiny entostyle on second molars. Lingual walls somewhat more corrugated than labial walls in upper check teeth, opposite in lower ones. Mandible with slightly sinuous horizontal ramus; marked mandibular scissure; premolars compressed mesiodistally and enlarged labiolingually; molars elongated mesiodistally and somewhat compressed labiolingually; paraconid absent or rudimentary; lingually open mesial fossette; metastylid and postentocristid strong; small ectostylid on each lower molar; third lower molars with wide, mesiolingually open mesial fossette; distal margin of hypoconulid separated from entoconulid occlusalward, and fused to it towards the collar; cementum occasionally present; cingula absent in lower cheek teeth; rugose enamel on lower molars.

Differential diagnosis. Differs from S. minutus , S. falcidens and S. apulicus by its larger size and the presence of rugose lingual enamel on lower molars. Differs from S. falcidens and S. apulicus by rugose labial enamel on lower molars. Differs from S. minutus , S. apulicus and S. mazzai by having mesodont molars. Differs from S. minutus and S. falcidens by absence of a cingulum on lower molars. Differs from S. falcidens by the presence of a tiny entostyle on M2. Differs from S. mazzai by non-pachyostotic mandible, the presence of an ectostylid on lower molars and strong metastylids.

Derivation of name. From the Latin name of the region Abruzzo (central Italy).

Preservation and deposition of type specimens. Soprintendenza Archeologica dell’Abruzzo (Chieti, central Italy).

Type locality and horizon. Tortonian Scontrone Member of the Lithothamnium Limestone ( Patacca et al. 2008; 41°45'15.54''N, 14°02'13.14''E), outskirts of Scontrone, southern border of the National Park of Abruzzi, L’Aquila, central Italy.

Description. For original description of the holotype, see Mazza & Rustioni (2011)). Morphological description of upper molars are erroneous, because the holotype is a mandible. Revised description: Mandible tapers abruptly rostrally. Fairly long diastema in front of p2. Ventral profile markedly convex under the lateral dentition. Marked mandibular scissure. p3 and p4 short, somewhat compressed mesiodistally and enlarged labiolingually. Parastylid well developed, paraconid absent; weak, backward verging metaconid. Entoconid well developed and backward verging like metaconid. Entostylid very small. Vertical groove on the posterolingual region of p4. Labial enamel wall rugose, lingual wall smooth. m1–m2 elongated mesiodistally and somewhat compressed labiolingually. Labial conids markedly triangular. m1 tightly in contact with p4, mesial wall flattened, preprotocristid bent abruptly in lingual direction with marked angle. Premetacristid very sharp and prominent lingually. Metastylid and postentocristid also very sharp and prominent. Preprotocristid fused to premetaconid crista, and postprotocristid to pre-entocristid. Hypoconid isolated. Small ectostylids. Enamel rugose. Residual cementum. m3 with tetraconid similar to that of m2. Premetacristid bent lingually, and preprotocristid separated from it, mesial fossette thus wide and opened mesiolingually. Distal margins of hypoconulid and entoconulid separated occlusalwards and rapidly fused towards collar.

Additional characters shown by paratypes, revised after Mazza & Rustioni (2011). SCT59 and SCT125 are both fragmentary right maxillaries preserving only M2-M3. All other paratypes are mandible fragments preserving various elements or their alveoles: SCT16 (p4–m3), SCT50 (p4-m3), SCT51 (p4, part of m1), SCT58 + SCT67 (m2), SCT81 (m1–m3), SCT89 (m1, m2), SCT102 (m1–m3, alveoles of p4 and (partial) p3) and SCT79, SCT71, SCT195 with unknown preservation (not described, not figured; likely small fragments). Wear stage not given in Mazza & Rustioni (2011). Occlusal surfaces of lower cheek teeth quite inclined outwards; inner cuspids sharp and pointed, whereas outer cuspids are affected by relatively higher degrees of wear; mesodont. M2–M3. Molars very similar to one another. Both bear robust parastyles, even stronger mesostyles, as well as considerably developed labial rib of the paracone. Much weaker external rib of metacone and metastyles. Lingual crescents trapezoidal, and postprotocristae and postmetaconule cristae robust. M3 with large metaconule. Cingula and cementum not present. Lingual crescents very closely spaced. Tiny entostyle in M2. p3–p4. Paraconid rudimentary in poorly worn specimens, obliterating as wear progresses (see, however, remark on wear stage above). m1–m2. In unworn or moderately worn first lower molars, preprotocristid extended to contact premetaconid crista, and postprotocristid to contact preentocristid. As wear progresses, these structures normally fuse together, so that protoconid connects mesially with premetaconid crista, as well as distally with pre-entocristid. Hypoconid isolated from the other conids at most levels of wear; only in considerably worn specimens posthypocristid fused to postentocristid. Prehypocristid fused mesially to postprotocristid only in heavily worn teeth. Residual cementum on some specimens.

Measurements. See Table 2 .

Figures

FIGURE 4. Postcranial elements of Hoplitomeryx. A, right distal humerus (RGM 178.487; Chiro 20 E) showing conical aspect of the trochlea: anterior view; B, distal left humerus (RGM 425.409; Fina N) without a supracondylar foramen: posterior view; C, distal right humerus (RGM 178.483; Chiro 20 A) with a small foramen: posterior view; D, right radius-ulna (RGM 260.916; San Giovannino) with high degree of synostotic fusion: lateral view; E, right radius-ulna (RGM 425.282; San Giovannino) with no fusion: medial view. Variations observed in the distal (left) radius: F, typical cervid pattern with the radial facet extending further than the intermedial facet; both facets are elongated (after Heintz 1970); G, both facets are tear-shaped and equally developed (after Zeder & Lapham 2010); H, the intermedial facet is much smaller than the radial facet and is almost round (after Heintz 1970). I, left metacarpal (RGM 425.350; Gervasio): anterior (dorsal) view; J, right metacarpal (RGM 425.351; Gervasio): posterior (palmar) view; K, right metacarpal (RGM 425.300; San Giovannino): anterior (dorsal) view; L, right metacarpal (RGM 425.300; San Giovannino): posterior (palmar) view. Schematic drawings of metacarpals showing the variation in morphology of the proximal articulation in proximal view: M, pattern seen in RGM 260.919 (San Giovannino), the typically cervid pattern; N, pattern seen in RGM 425.322 (San Giovannino); O, pattern seen in RGM 262.000 (Gargano, unknown fissure); P, pattern seen in RGM 425.350 (Gervasio).