Eostyloceros hezhengensis, Deng, Tao, Wang, Shi-Qi, Shi, Qin-Qin, Li, Yi-Kun & Li, Yu, 2014
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publication ID |
https://doi.org/ 10.11646/zootaxa.3893.3.3 |
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publication LSID |
lsid:zoobank.org:pub:F790BCBB-60E2-4B30-9C59-728A62292906 |
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DOI |
https://doi.org/10.5281/zenodo.5620781 |
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persistent identifier |
https://treatment.plazi.org/id/6C108859-8F3A-2557-FF7C-FDEBFB010954 |
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treatment provided by |
Plazi |
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scientific name |
Eostyloceros hezhengensis |
| status |
sp. nov. |
Eostyloceros hezhengensis sp. nov.
( Figs. 3 View FIGURE 3 , 4 View FIGURE 4 ; Table 1 View TABLE 1 )
Holotype. IVPP V 19059 View Materials , an adult skull with its cranial appendages, lacking the muzzle, the left dentition, and the basioccipital part ( Figs. 3 View FIGURE 3 , 4 View FIGURE 4 ).
Type locality. Gaojiashan (LX 0 0 34, 35°21'21.3" N, 103°19'00.7" E, Elevation 2459 m) in Guantangou Township, Hezheng County, Gansu Province, China ( Fig. 1 View FIGURE 1 ).
Stratigraphic 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).
Etymology. Hezheng is the county where the fossil locality of this new species is situated.
Diagnosis. A large-sized muntjak with pedicles in parallel with the sagittal axis of the skull. Between the two frontal ridges, the front bone is strongly concave and the sagittal suture forms a robust ridge. The lacrymal fossae are very large. The anterior orbital rim is above the M2/M3 boundary. The pedicle is short, cylindrical, robust, and extends posteriorly from the rear of the orbit. The shedding plane of the burr forms an angle of about 70° medially with the longitudinal axis of the pedicle. The burr consists of a series of knobby tubercles. The anterior and posterior branches arise and diverge at an angle of 30° from the burr, with a U-shaped fork. Both of them have many deep furrows and high edges on their surfaces. The posterior branch is relatively long, and its tip is strongly curved posteriorly and medially. The anterior branch is straight and long, about half as long as the posterior branch, and it is situated anteromedially from the posterior branch. The posterior branch is lateromedially compressed, and the anterior branch has a circular cross section.
Description. The broken basioccipital region comprises the inner braincase, and the right petrous bone is preserved ( Fig. 3 View FIGURE 3 F). The skull is dorso-ventrally compressed to become low in cranial height, which makes the preorbital fossa deformed, so its exact shape and size cannot be determined. Judged by the wear degree of its dentition, this skull belongs to an adult individual.
The pedicle arises on the frontal bone behind the orbit in parallel with the sagittal axis of the skull. The cylindrical pedicles are long and parallel to each other. Between pedicles the cranial roof is concave, but the sagittal frontal suture is prominent to form a strong edge, and then stretches posteriorly and curved downward to the connection of the frontal and parietal bones ( Fig. 3 View FIGURE 3 G). The anterior part of the frontal bone is obviously depressed near the nasal bone. The diameter of the supraorbital foramen is about 4 mm, and located medial to the posterior part of the frontal ridge. The frontal ridge has wide posterior and anterior parts, and narrows to the middle. The orbit is large and projecting laterally, and its lower rim is more projecting than the upper rim ( Fig. 3 View FIGURE 3 E). The orbit is 36.5 mm long and about 23 mm high (height approximated due to the compression), and its anterior end is located above the M2/M3 boundary with a straight upper rim and curved anterior, lower, and posterior rims that form a semicircle. The facial crest is unclear. The lacrymal fossa is large, deep, triangular in shape, and about 22 mm long. The ethmoidal fissure is nearly an equilateral triangle with a length of 17 mm, which is relatively deep and located at the skull roof in front of the orbit and above the lacrymal fossa ( Fig. 3 View FIGURE 3 G). The preorbital fossa is deformed so that its exact shape and size cannot be determined.
The braincase is rounded. The temporal crest is thin, straight, and declined posteriorly. The paroccipital process is oblique, inclined anteriorly, and its base is fused with the mastoid process to become very robust and large ( Fig. 3 View FIGURE 3 F). The external auditory meatus declines posteriorly, and its entrance is large and circular, with a diameter of 6 mm ( Fig. 3 View FIGURE 3 E). The postglenoid process is thin, low, and tightly closed to the front side of the external auditory meatus. From the broken position of the ear bulla, the right petrous bone can be seen ( Fig. 3 View FIGURE 3 F). The parietal bones are convex, on which the supraoccipital bone is more convex. Based on the preserved remains of the right occipital surface, it is almost facing ventrally, which may be a result of the deformation due to the compression ( Fig. 3 View FIGURE 3 D).
The cranial part behind cranial appendages is very short ( Fig. 3 View FIGURE 3 E), and the frontal bone has a strong rugose protuberance medial to the base of the pedicle. The parietal surface has an angle slightly larger than 90° to the frontal and occipital surfaces, respectively. The suture between the parietal and temporal bones is prominent to form an edge. The skull roof is the widest between the postorbital processes. The stylomastoid foramen is very large and located between the tympanic bulla and the external auditory meatus. The occipital crest is robust and turns anteriorly above the mastoid process to form the temporal crest, which does not directly extend to the posterior side of the paroccipital process. A crest behind the paroccipital process turns supero-medially at the mastoid process, and ends at a nutrient foramen below the middle part of the occipital crest, which does not connect with the occipital crest. The ventral surface of the skull is the widest at the mastoid process. The bottom of the curved depression in the lateral side of the palate is situated at the level of the posterior margin of M3.
Measurements of skull (mm): Length from the posterior rim of the orbit to the occipital crest: 56.7; Maximal width of the skull (between posterior rims of orbit): 80.6; Width between the supraorbital foramina: 39.5; Cranial height behind M3: 38.4; Exterior height of the exterior auditory meatus: 8; Length of the upper cheek tooth row: 54.
The holotype IVPP V 19059 View Materials has two complete antlers with their pedicles ( Figs. 3 View FIGURE 3 , 4 View FIGURE 4 ). The proximal end of the pedicle extends to the frontal as a strong rounded ridge. The pedicle is robust and short, arising from the frontal posteriorly. Its surface is smooth, and its proximal cross section is oval, nearly circular distally. The burr has a 70° angle sloping medially from the longitudinal axis of the pedicle, and it is consists of a series of bony tubercles, appearing as an oval cluster of a ring of pearls ( Zdansky 1925:3). The maximal diameter of the antler base is located medial-laterally, and the minimal diameter antero-posteriorly. The vertex of the bifurcate angle between the anterior and posterior branches is placed 35 mm above the burr. The posterior branch is long and straight, with a compressed cross section, but its tip is strongly curved posteriorly and medially, with a nearly circular cross section. The anterior branch is straight, with a half-length of the posterior branch, and it has a circular cross section and a 30° angle from the posterior branch. The ornamentation of the antler is deep longitudinal vessel furrows and high edges on the surface of both anterior and posterior branches ( Fig. 3 View FIGURE 3 A-C).
Other measurements of cranial appendage (mm): Medial length of the pedicle: 11.5; Lateral length of the pedicle: 58.5; Maximal diameter of the pedicle: 23; Minimal diameter of the pedicle: 20.5; Thickness of the burr: 7.6; Maximal diameter of the burr: 40.3; Minimal diameter of the burr: 36.8; Maximal diameter of the posterior branch base: 28.3; Minimal diameter of the posterior branch base: 20; Maximal length of the antler: 218; Height of the shaft including the burr: 41; Length of the anterior branch above the fork: 66.5; Maximal diameter of the anterior branch base: 19; Minimal diameter of the anterior branch base: 15.
Teeth: P2-M1 lack the lingual cingulum. The labial grooves of the cheek teeth are deep, and they gradually become shallow towards the crown base. The paracone rib is well-developed, the parastyle rib is moderate, and the mesostyle rib is weak on the labial wall of the molars. The labial anterior valley is U-shaped, and the posterior valley is V-shaped; both are narrow. The paracone and the metacone are rhombic in shape, especially the paracone, but they become rounded towards the crown base ( Fig. 3 View FIGURE 3 H).
P2 is longer than wide. The lingual crescent is narrow, and the hypocone is larger than the protocone. The paracone rib is located anteriorly, strong, and oblique anteriorly. The lingual middle groove is wide and shallow, and it is slightly oblique posteriorly on the lingual surface. The two neocristae are tiny and weak; the medial crista is strong, and its base has a tiny enamel circle. The parastyle is weak, and the paracone and the metacone are the same in size, both of them are larger than the hypocone.
P3 is nearly square, and it is similar to P 2 in shape but slightly larger than P 2 in size. Its differences from P2 include the wider lingual crescent, the weak and anteriorly positioned entoflexus, and strongly and labially projecting rib-like parastyle. The paracone rib is located and declined anteriorly, and the anterior valley is deep. The neocrista is absent, and the two medial cristae are fine. The paracone and the hypocone are similar to each other in size; both of them are larger than the metacone.
P4 is wider than long, and it is similar to P 3 in shape. Its differences from P3 are that its size is shorter and wider, the entoflexus and the neocrista are absent, the medial crista is one and weak, the paracone rib is near the middle of the labial wall, the parastyle rib is weak, the metastyle is well developed, and the anterior and posterior valleys are wide and shallow.
M1: the neocrista and the pli hypocone are weak, and the crista is absent.
M2: The neocrista and pli hypocone are weak, and the crista is well developed. The anterior and posterior cingula are strong. The entostyle is relatively developed, but it exists on the lower part of the crown.
M3: The neocrista and the pli hypocone are well developed, and the crista is weak. The anterior and posterior cingula are weak, and the entostyle is low.
Measurements of teeth (length×width×height, mm): P2: 8.4×8.8×7.7; P3: 8×10×7.9; P4: 7.7×10.2×7.8; M1: 10.8×11.9×5.6; M2: 11.7×13.2×7.7; M3: 11.6×12.2×8.4.
Comparison. The antlers of the skull (IVPP V 19059 View Materials ) are simply forked, and their anterior and posterior branches are bifurcated from each other with a very short distance above the burr, which show that this specimen belongs to a member of the subfamily Muntiacinae (Dong et al. 2004, 2014). The very short pedicle distinguishes this form from the other muntiacines, such as Dicrocerus Lartet, 1837 , Euprox Stehlin, 1928 , Muntiacus Rafinesque, 1815 , and Heteroprox Schaub, 1928 ( Colbert 1936; Dong et al. 2003, 2004; Geraads 2003), except Eostyloceros Zdansky 1925 . Its curved posterior branch is also different from those of Euprox and Heteroprox ( Dong et al. 2003; Geraads 2003). Its short pedicles have a circular cross section, the pedicle ridges on the frontal are robust, the anterior and posterior branches are directly divergent on the tubercular burr, many furrows and edges are present on the cylindrical anterior and posterior branches, and the lacrymal fossa and ethmoidal fissure are wide and deep. On the teeth of this skull, cristae are very strong, and they become small pits after wear; P2 and P3 have an anteriorly shifted strong paracone rib, but the molars have a weak paracone rib. All these characters are typical of Eostyloceros ( Zdansky 1925; Teilhard de Chardin & Trassaert 1937). As a result, this skull is attributed to the genus Eostyloceros .
Zdansky (1925) established the genus Eostyloceros and its two species ( E. blainvillei and E. triangularis ) based on materials from the Late Miocene of Wuxiang, Shanxi. Later, several species of this genus were described in Asia and Europe, including Eostyloceros pierensis Thomas, 1951 (this species is now ascribed to genus Lucentia ), E. pidoplitschkoi Korotkevich, 1964 , E. propria Abdrakhmanova, 1974 , E. longchuanensis Lin et al., 1978 , E. maci Vislobokova, 1985 , and E. actauensis Abdrachmanova, 1989 . We compare E. hezhengensis sp. nov. with the known species of Eostyloceros .
The new species of the Linxia Basin is different from Eostyloceros blainvillei in its smaller size ( Table 1 View TABLE 1 ), posteriorly curved distal end of the posterior branch, which is not medially curved, a smaller angle between the anterior and posterior branches, shorter pedicles, and anteriorly positioned anterior branch from the posterior branch (not medially positioned). In E. blainvillei , the angle between the burr plane and longitudinal axis of pedicle is nearly 90°, but 70° in the new species.
Notes: Apd burr: anterior-posterior diameter of burr; Lmd burr: latero-medial diameter of burr; Apd beam: anteroposterior diameter of beam just above burr; Lmd beam: latero-medial diameter of beam just above burr; I segm: first segment length (see Abbazzi & Croitor 2003, fig. 3); Angle: angle of bifurcation; L antler: lateral length of antler.
The specimens of Eostyloceros triangularis are few, so its characters described by Zdansky (1925) are slightly informative. In fact, Zdansky (1927) doubted the independence of this species. The new species is different from E. triangularis in having the oval cross section of the posterior branch, instead of the triangular one. The anterior branch of E. triangularis may be attached on the posterior branch, but the two branches of the antler are independently arising from the burr in the new species. There is a protuberance on the position of 40 mm above the fork of the antler in E. triangularis , which seems to develop a new branch, but the new species has no such protuberance. The posterior branch of E. triangularis is strongly curved anteriorly, with few vessel furrows on the lateral side, but that of the new species is straight, with rich vessel furrows.
Bohlin (1937) described several fragmentary antlers from Qaidam Basin and identified them as? Eostyloceros sp. Among the specimens, some have the characters of Eostyloceros , but they are different from the Hezheng species in having a strongly anteriorly curved posterior branch, a larger angle between the anterior and posterior branches, a wing-like edge on the medial aspect of the beam, smaller pearl-like bony tubercles of the burr, a pearlike or irregular angular cross section of the beam, and weaker furrows on the surface of the antler.
Eostylocerus pidoplitschkoi was from the Trifonesty type locality, south-eastern Moldova, and from the Lower Pliocene deposits of the Kuchurgan River at sites Novopetrovka, Yurievka, Voinich in the south of the Ukraine (Korotkevitsch 1964, 1970). Eostylocerus is the subsequent spelling (orthographia subsequens) of Eostyloceros , so it is a null name (nomen nullum). E. pidoplitschkoi is the only species of the genus from the Early Pliocene of East Europe. The definition of this deer is based on the morphology of cranial appendages. E. pidoplitschkoi is different from E. hezhengensis in having a much larger angle between the anterior and posterior branches, a more robust posterior branch, and a more horizontal burr related to the pedicle.
Eostylocerus propria was described from the northeast coast of the Lake Karabastuz in Kazakhstan (Abdrachmanova 1974). Its holotype is a complete right antler. This species has a relatively high position of the fork above the burr, a very large angle between the anterior and posterior branches ( Table 1 View TABLE 1 ), and weak vessel furrows, which are different from those of E. hezhengensis .
The material of Eostyloceros longchuanensis includes only an incomplete left antler from the Early Pleistocene of the Yuanmou Basin in Yunnan Province ( Lin et al. 1978). The size of E. longchuanensis is similar to that of the new species, but the angle between the anterior and posterior branches is 90° in the former, much larger than in the latter. The posterior branch of E. longchunensis is curved anteriorly, with wide and blunt edges, but that of the new species posteriorly, with narrow and sharp edges.
The fossils of Eostyloceros maci include several fragmentary antlers from the Pliocene of Olkhon Island in Lake Baikal ( Vislobokova 1985). They show slightly longer pedicles and a higher position of the bifurcation than those of E. hezhengensis . The reconstruction for the antlers of E. maci indicates that they have a larger angle between the anterior and posterior branches (about 75°) ( Vislobokova 1985:fig. 1).
Thomas (1951) described the material from the early Turolian site Piera in Barcelona, Spain as a new species Eostyloceros pierensis . But Azanza et al. (1989) stated that this species should be removed from the muntiacines on the basis of the location and disposition of the pedicles as well as the structure of the antlers, and suggested that it could be better related to the middle-late Turolian cervines. As a result, Azanza & Montoya (1995) referred this species to their new genus Lucentia as L. pierensis , because it has monopodial antlers, moderately long pedicles set on the cranial cavity but not prolonged onto the face as ridges, and tines set very high above the burr.
Eostylocerus actauensis from the Middle Miocene of Dzhungarian Aktau in East Kazakhstan was described as the smallest species without any description and figure (Abdrachmanova et al. 1989), so it is not only null but also a naked name (nomen nudum).
As a result, the skull (IVPP V 19059 View Materials ) recovered from the Linxia Basin belongs to the genus Eostyloceros but differs from any known species, and so is here described as a basal new species of this genus, E. hezhengensis sp. nov.
Phylogenetic analysis. The phylogeny of Eostyloceros has been poorly understood since Zdansky (1925) established this genus as distinct. Recently, Dong (2007) and Dong et al. (2014) included Eostylocerus blainvillei in their phylogenetic analyses of muntjacs. In order to test the phylogenetic relationship of E. hezhengensis among muntjacs and some basal cervids, the antler, cranial and dental characters were scored from Dong et al. (2014). The matrix contains 15 taxa and 26 unordered characters, in which a hypothetic ancestor serves as an outgroup (see Table 2). The analysis was carried out using TNT (V 1.1) ( Goloboff et al. 2003), with the traditional search option. The reported results are based on strict consensus and 50% majority rule of all the most parsimonious trees (MPTs). Node supports in the strict consensus tree were calculated usinga bootstrap analysis (1,000 replicates).
The results evidenced 10 MPTs. The strict consensus and 50% majority rule suggested that the genus Eostyloceros is paraphyletic. In the strict consensus tree, all the species of Eostyloceros and some other fossil taxa are clustered as the sister group of the extant Muntiacus muntjak . However, the relationships among other fossil taxa, especially among the species of Eostyloceros , are not well resolved, particularly due to incomplete data matrix and strong parallel evolution ( Fig. 5 View FIGURE 5 A). In the 50% majority rule tree, Eostyloceros hezhengensis sp. nov. is located as the sister group of other species of Eostyloceros and some other fossil taxa ( Fig. 5 View FIGURE 5 B). The supporting character status includes 3(1), moderately developed frontal crest, and 10(1), simply curved main beam. The 50% majority rule tree supports E. hezhengensis sp. nov. as the basal species within Eostyloceros , Euprox , Paracervulus , and Lucentia , which constitutes a monophyletic group.
antler, cranial and dental characters and their states are listed as follows: (1) parallel pedicles: 0, no; 1, yes. (2) position of pedicle: 0, above orbit; 1, behind orbit. (3) pedicle crest on frontal: 0, weak; 1, medium; 2, developed. (4) backward pedicle inclination: 0, weak; 1, medium; 2, strong. (5) compressed pedicle: 0, no; 1, yes. (6) burr development: 0, weak; 1, medium; 2, strong. (7) antler basal segment: 0, absent; 1, present; 2, developed. (8) centripetal mineralization of antler: 0, absent; 1, present. (9) cross section of main beam (posterior branch) base: 0, nearly round; 1. oval; 2, elongated. (10) the growth style of the main beam: 0, nearly straight; 1, simply curved; 2, multi-curved. (11) main beam size: 0, small; 1, medium; 2, large. (12) brow tine (anterior branch) size: 0, small; 1, medium; 2, large. (13) angle between main beam and brow tine: 0, small; 1, large. (14) angle shedding: 0, uncertain; 1, irregular; 2, regular. (15) antler ornamentation: 0, absent; 1, present; 2, developed. (16) antler size: 0, small;
medium; 2, large. (17) Palaeomeryx fold on lower molars: 0, present; 1, absent. (18) relationship between nasal and maxilla: 0, separate; 1, connected. (19) anterior margin of lacrimal: 0, with projection; 1, without projection. (20) lacrimal fossa: 0, small; 1, medium; 2, large. (21) metatarsal length: 0, short; 1, medium; 2, long. (22) frontal gland: 0, absent; 1, present. (23) body size: 0, small; 1, medium; 2, large. (24) neocrista on upper molar: 0, absent; 1, present; 2, developed. (25) lingual cingulum on upper molar: 0, developed; 1, present; 2, disappeared. (26) postmetaconule crista: 0, absent; 1, present; 2, developed. All the characters and character states are after Dong et
(2014) and all the scorings in the data matrix are based on adult material and unworn (or slightly worn) teeth.
TABLE 1. Measurements and comparison of cranial appendages of Eostyloceros (mm).
| Taxon | Apd burr | Lmd burr | Apd beam | Lmd beam | I segm | Angle | L antler |
|---|---|---|---|---|---|---|---|
| E. hezhengensis | 39 | 40 | 39 | 35.4 | 35 | 30 | 218 |
| E. pidoplitschkoi | 29.8–51.6 | 19.6–37 | 25.5–43.5 | 19.4–27.2 | 20–39.8 | 70 | 260 |
| E. blainvillei | 46–57 | 37–41 | 41.5–60 | 40 | 202–320 | ||
| E. longchuanensis | 40 | 38 | 38.1 | 33.7 | 40.2 | 90 | 210 |
| E. maci | 37.6–39.5 | 27.3–35.2 | 36–51.5 | 75 | |||
| E. propria | 35 | 31 | 25 | 22 | 49–59 | 80 | 200 |
| IVPP |
Institute of Vertebrate Paleontology and Paleoanthropology |
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