A new species of Euprox (Cervidae, Artiodactyla) from the upper Miocene of the Linxia Basin, Gansu Province, China, with interpretation of its paleoenvironment Author Hou, Sukuan text Zootaxa 2015 3911 1 43 62 journal article 36741 10.11646/zootaxa.3911.1.2 8cb33c03-5966-44d3-9d2a-83e966e503d3 1175-5326 287678 AE247236-09A1-45E9-8E70-1C7ADD709B0D Euprox grandis sp. nov. ( Figures 2–6 ; Tables 1–2) Etymology. The new species is larger than all the known species of Euprox , so it is named by this character. Holotype . IVPP V 20080.1-3, an adult skull and a pair of antlers ( Figures 2-4 , 6 ). The skull was compressed vertically, and the anterior and middle part of the snout, the zygomatic, the posterior part of the frontal bone, the parietal bone and the temporal-squamosal region are partly missing; the pedicle ridge is crushed, but there are clear fracture surfaces preserved on both the skull and the pedicle ridge of the left antler, which indicate they belong to the same individual. The right M3 is broken at the second lobe. Included specimens. IVPP V 20081.1-2, a pair of nearly complete antlers ( Figure 5 ). The pedicle ridge is almost entirely missing, and only the left antler preserves a small part of the pedicle ridge. The right antler is laterally compressed. Locality and Horizon. upper part of the Liushu Formation, late Miocene, late Bahean Chinese land mammal age, with an age of about 8 Ma ( Deng et al. 2013 ). Diagnosis. The largest known Euprox with significantly long pedicle and weak burr. The skull length is about twice that of Muntiacus reevesi , and 150% of M. muntjak ; and the cheek teeth about 115-120% of E. robustus . The ethmoidal fissure is broad; the preorbital fossa is small, reaching forward to a level above the anterior part of P4; the orbit is behind and above M3; the pedicle arises above the middle and posterior part of the orbit rim and inclines backwards and laterally, curving slightly posteriorly; the burr is clear but weak; the two prongs diverge medio-laterally slightly above the burr at an angle of about 30º; the main beam and the brow tine are weakly curved medially and posteriorly, and the distal end of the main beam turns to curve laterally; the main beam is thinner and shorter than the pedicle, and the brow tine is about 60–70% as long as the main beam; the burr and the lower part of the prongs are decorated by weak longitudinal grooves and crests; the cheek teeth are brachydont, with strong parastyle and paracone rib, medium internal postprotocrista and metaconule fold, and weak external postprotocrista in the upper molars; the cingula are weak or absent. Description. Most of the nasal bone is missing, so the anterior part of the nasal cavity is exposed, and there is a clear sagittal crest on the dorsal surface of the palate ( Figure 2 a). The naso-frontal suture is broad and convex backwards. Only the posterior part of the ethmoidal fissure is preserved, which is broad and inserts between the frontal bone and the lacrimal bone; the medial border of the ethmoidal fissure inclines antero-medially and the lateral border directs forwards; the visible broadest part of the ethmoidal fissure is at the level of the anterior end of the frontal bone, about 17 mm at the right side and 21 mm at the left side; broken turbinates can be observed from the ethmoidal fissure. The frontal bone is broad and weakly concave between the pedicle ridges, and there is a weak ridge along the frontal-frontal suture. The supraorbital fossae set slightly anterior to the posterior rim of the orbit, far away from the frontal-frontal suture and close to the pedicle ridge. The pedicle ridge arises above the middle of the orbital rim, and it is concave at the base on both the supra-medial and the infra-lateral surfaces; the two pedicle ridges form an angle of about 30º. The posterior part of the frontal bone and the parietal bone are missing, only the squamosal part of the temporal bone on the right side is preserved. The supraoccipital bone is nearly parallel to the basioccipital bone. Thick cancellous bone can be observed from the fracture surface, which is thin in the middle (about 8 mm ) and thick on lateral sides (about 25 mm ). The nuchal crest is nearly straight, without a tuberosity in the middle, which differs from the extant muntiacines; the crest extends infra-laterally and ends at a triangular protuberance. The right side of the skull is better preserved than the left side ( Figure 2 b). The infraorbital foramen is broken, which is about 16 mm infro-anterior to P2. The lacrimal pit is deep and strongly compressed. The right orbit is complete but undergoes a dorsoventral compression; it is 50 mm long and 33 mm high (due to the compression), the estimated, uncompressed length×width is about 40 mm × 40 mm . The postorbital process of the frontal bone is significantly broad compared with the postorbital process of the maxillae. The lateral surface of the pedicle ridge is concave, above and posterior to the orbit. The temporal surface of the cranium is notably medial to the lateral surface of the pedicle ridge, and the distance between these two surfaces is about 55 mm . The process of mandibular fossa (post-glenoid process) is strong, which can be observed from the lateral side; there is a gap about 15 mm between the process of mandibular fossa and the base of the paroccipital process for the external auditory meatus to get through. The palate is flat and broad ( Figure 2 c), forming an angle of about 20º with the basioccipital bone in lateral view; there’s a thin crest along the palatine suture. The anterior border of the choana reaches the posterior part of M3 at the lateral side and extends at least 16 mm behind M 3 in the middle. The vomer is thick, and it is close to the foramen orbitale. The foramen ovale is big, set between the foramen orbitale and the foramen lacerum. The basioccipital bone is broad and flat. The posterior tuberosities are strong with notable concavities lateroanteriorly located, and the pharyngeal tuberosities are very weak. The occipital condyle is broad from the ventral view. Two separated hypoglossal foramina can be observed; the anterior one is large and can be observed at both the condyloid fossa from the ventral view and the inner surface of the occipital condyle from the occipital view, while the posterior one is smaller and can only be seen at the inner surface of the occipital condyle from the occipital view. The occipital region ( Figure 3 ) is low and broad, with a weak occipital crest. The external medial crest of the occipital is very weak, as are the lateral fossae along the upper part of the external medial crest of the occipital. The antlers of the holotype V 20080 ( Figure 4 ) are partly broken off at the pedicle ridge. The break of the left antler is from the orbit rim to a point about 2/5 up the pedicle; the right antler was broken at the ventral and lateral part of the pedicle. The pedicle is notably long (Table 1). The pedicle inclines supra-posteriorly from the lateral view and postero-laterally from the dorsal view, with the distal part curving slightly backwards. The surface of the pedicle is smooth. The cross section at the pedicle ridge is triangular at the insertion, and then becomes oval immediately; the long axis of the cross section changes from antero-posterior to medio-lateral. The burr consists of a series of bony nodes and appears as an oval pearl ring. The diameter of the nodes is 5-8 mm , so that the burr only weakly projects from the pedicle. The weakest part of the burr is at the posterior surface. The cross section of the burr is also oval, and its long axis matches with the distal cross section of the pedicle. The antler base (shaft) is low and thick, about 30-40 mm in height. The main beam and the brow tine diverge medio-laterally at an angle of about 30º. The main beam is shorter than the pedicle and has a smaller diameter than the latter; it arises directly from the burr and curves both medially and backwards; a large shallow concave can be observed on the medial surface of the proximal part of the main beam and extends to the base of the brow tine; the distal end of the main beam curves postero-laterally. The brow tine is at the medial side of the main beam, and also arises directly from the burr; it is about 3/5 as long as the main beam, and only very weakly curves backwards; the lateral surface of the brow tine is more concave than the medial surface. The antler is weakly ornamented with longitudinal grooves and crests covering the surface from the proximal part of the main beam and the brow tine to the burr; the ornamentation is also weaker on the posterior surface than the anterior surface. TABLE 1 . Measurements and comparisons of the skulls of Euprox grandis sp. nov. from the Linxia Basin (mm) E. grandis sp. nov. * E. robustus E . sp. E .cf. furcatus E. altus 26.3 23.4 28.0 22.7 19.9 17.7 16.5 13 100 >124 111 ca.98 69 73# 32# 3*100 147 155 149>143 216 212 194 Notes: 1. lateral length of pedicle; 2. medial length of pedicle; 3. maximum diameter of distal pedicle; 4. minimum diameter of distal pedicle; 5. maximum diameter of proximal pedicle; 6. minimum diameter of proximal pedicle; 7. height of burr; 8. maximum diameter of burr; 9. minimum diameter of burr; 10. length of antler base; 11. maximum diameter of proximal antler base; 12. minimum diameter of proximal antler base; 13. length of main beam; 14. maximum diameter of proximal main beam; 15. minimum diameter of proximal main beam; 16. length of brow tine; 17. maximum diameter of proximal brow tine; 18. minimum diameter of proximal brow tine. * mean value; # calculated 2/13*100.
V 20080.2 V 20080.3 V 20081.1 V 20081.2 (Dong et al. 2003) (Dong et al. 2003) (Zdansky 1925) (Wang & Zhang 2011)
1 2 >155>155 173.0>154 >165 166.5 104.7 64.2 102.5 43.6
3 4 41.1 33.5 38.9 33.0 39.5 33.4 40.5 35.0 32.0 25.0 24.3 28.3 22.2 22.3
5 6 39.5 33.9 43.8 33.6 29.4 31.1 24.2
7 8 9 10 11 11.7 60.4 52.7 ca. 34 57.8 12.6 60.2 44.4 ca. 29 55.3 13.2 58.7 47.5 39.2 56.4 13.0>58 47.4 39.0 53.3 11.7 10.1 8.3 69.3 53.0 47.2 24.7–35.7 54.2 39.6 42.0 24.7 26.7 31.0 31.0–72.9 48.9 36.3 44.4
12 13 47.5 125.0 40.0>112 39.7 156.0 35.6>168 31.6 23.1 34.0 151.1 141.0 136.2
14 15 39.0 28.8 38.4 27.5 33.5 30.3 38.8 27.8 32.9 25.6 27.5 29.0 19.6 19.0
16 17 71.9 30.0 78.0 30.5 111.5 31.3 105.0 28.5 88.5 67.5 84.7 28.1 21.8 20.2
FIGURE 2. Skull of Euprox grandis sp. nov. (V 20080.1, holotype). a, dorsal view; b, lateral view; c, ventral view; scale bar equals 5 cm; the dash line shows the orientation of the pedicle ridge. FIGURE 3. Occipital view of the skull of Euprox grandis sp. nov. (V 20080.1, holotype). Scale bar equals 5 cm. The referred specimen V 20081.1-2 ( Figure 5 ) is a pair of well-preserved antlers, only broken at the start of the pedicle ridge; and the pedicle of the right antler is strongly compressed medio-laterally. The antler is larger than antlers of the holotype . The pedicle is longer than the main beam and has a smooth surface. The burr is weak, more prominent anteriorly. The main beam and the brow tine have more pointed apexes, and are also more curved than in the holotype . The concave between the main beam and the brow tine on the superior surface of the antler base is narrower and shallower than in the holotype . The ornamentation of the antler is weaker than in the holotype , gently developed from the middle of the main beam and the brow tine to the burr. The angle between the main beam and the brow tine is about 30º. This pair of antlers may belong to an older individual than the holotype . The upper cheek teeth ( Figure 6 ) of the holotype are well preserved, only the right M3 is broken at the second lobe. The tooth row is gently curved, and the M1-M3 length is longer than the P2-P4 length. The dental morphology is described below (see Table 2 for measurements). TABLE 2. Measurements of the upper cheek teeth of Euprox grandis sp. nov. from the Linxia Basin (mm)
Tooth Length Width Height Hypsodonty index
P2 left 17.0 15.7 13.0 76.47
right 17.0 16.0 13.0 76.47
P3 left 17.2 17.5 13.9 80.81
right 16.2 17.3 14.0 86.42
P4 left 16.0 19.0 13.5 84.38
right 14.0 19.1 14.2 101.43
M1 left 20.2 21.3 11.0 54.46
right 20.6 21.4 11.0 53.40
M2 left 24.0 25.7 14.0 58.33
right 23.9 25.7 14.0 58.58
M3 left 22.8 23.5 14.0 61.40
FIGURE 4. Antlers of Euprox grandis sp. nov. (V 20080.2-3, holotype) a, V 20080.2, left antler, anterior view; b, V 20080.2, left antler, medial view; c, V 20080.3, right antler, posterior view; scale bar equals 5 cm. The length of P2 is greater than its width. P2 is composed of two crescents. The lingual crescent is narrow, and the anterolingual cone and the posterolingual cone (=hypocone in Gentry et al . 1999 ) are similar in size and not separated. Three tiny central folds (medial cristae in Dong 2004 ) appear on the posterolingual cone of the left P2. The anterolabial cone (paracone in Gentry et al . 1999 ) is slightly larger than the posterolabial cone (metacone in Gentry et al. 1999 ), and they are both larger than the anterolingual cone. The anterior style (parastyle) and the anterolabial cone rib (paracone rib) are strong, which are nearly vertical, while the mesostyle and the posterior style (metastyle) are not developed. P2 lacks cingulum. P3 is near square, slightly wider than long. The length of P3 is similar to P2 but the width is larger than P2. Its lingual crescent is thicker and more convex than in P2, and the central fold is stronger than in P2 and connected to the posterolabial cone after being worn. The anterior style and the anterolabial cone rib are strong. There is no cingulum. The width of P4 is greater than its length. The lingual crescent is as thick as in P3 but much shorter than the latter; the central fold is stronger than in P3, connected to the posterolabial cone in the left P4 and separated from the posterolabial cone in the right P4; there is one more tiny fold posterior to the central fold in the left P4. The labial crescent is as in P2 and P3 but much shorter. The anterior style and the anterolabial cone rib are strong and the posterior style is relatively weak. There is no cingulum. The width of M1 is slightly greater than its length. It is composed of four selenodont main cusps. The lingual main cusps are lower than the buccal ones. The internal postprotocrista (neocrista in Gentry et al . 1999 ) is developed and bifid, while the external postprotocrista (postprotocrista in Gentry et al . 1999 ) is very weak. The premetaconulecrista is relatively strong; there is one tiny internal premetaconulecrista fold in the right M1, which directs to the posterior fossa, and there is one internal premetaconulecrista fold and one external premetaconulecrista fold in the left M1.The metaconule fold (spur in Gentry et al . 1999 ) is stronger than the premetaconulecrista fold and weaker than the internal postprotocrista. The parastyle, mesostyle and paracone rib are strong, and the metastyle is relatively weak and only slightly protrudes buccally. The metacone rib is very weak. The anterior cingulum is only very weakly developed on the protocone, and the posterior cingulum only weakly visible at the postero-lingual corner of the metaconule. M2 is similar to M 1 in shape and larger than M1. The internal postprotocrista and metaconule fold are stronger than in M1. The metacone rib is still weakly developed but stronger than in M1. The cingulum is almost absent, only the lingual cingulum being visible, which is very thin and not continuous. M3 is similar to M 1 in size but bears a smaller second lobe. The internal postprotocrista and the postprotocrista are the largest of the three molars and the internal postprotocrista is slightly folded. There are two small external premetaconulecrista folds and the metaconule fold is absent. The parastyle, paracone rib and the mesostyle are weaker than in M1 and M2, but the metacone rib is stronger than in M2. There is a very weak entostyle and there is no cingulum.