Old World Porcupines, Hystrix spp., are some of the Old World largest Rodents ranging from Late Miocene to recent. Until recently Hystrix fossils have been recorded mostly from European Neogene–Quaternay and Asian Quaternary, with only a few from Neogene of Asia. In the last decades records of Neogene Hystrix from China have been slowly accumulated. Just recently, some new and well preserved Hystrix fossils, including 4 skulls, two of them with their mandibles, were collected from Neogene deposits in Linxia Basin. This is the best Neogene material of Hystrix so far known from Eurasia. Detailed study of these fossils shows that they not only represent a new species, but also enhance our understanding of Hystrix as a whole.
In a paper published in the journal Vertebrata PalAsiatica on 16 July 2020, Wang Ban-Yue and Qiu Zhan-Xiang of the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences, describe a new species of Porcupine from the Late Miocene-Early Pliocene of Gansu Province, China.
The species is described from two specimens, HMV 2002 nearly complete skull (but the basioccipital is slightly displaced from its original position) with mandible and a thoracic vertebra, and HMV 2003, a partial skull (lacking occipital part) with mandible, both from the Early Pliocene Hewangjia Formation of Zhuangkeji Village in Guanghe County. Two further specimens are also refered to the new species, (IVPP V 26033, a nearly complete skull from the Late Miocene upper part of the Liushu Formation, at Zhuangkeji Village in Guanghe County, and HMV 2004, a complete skull, from the Late Miocene upper part of the Liushu Formation, at Maijiaji Village in Hezheng County.
The new species is named Hystrix brevirostra, which derives from brevi, Latin, short; rostra, Latin, feminine, nose. It means that the Animal has a relatively short rostrum. It is a Large-sized Hystrix. Skull low and wide, with relatively short rostrum and diastema; nasal relatively short, with posteriorly convex posterior border nearly aligned with the lacrimal. Horizontal ramus of mandible low, with a shorter and deeply concave diastema. Cheek teeth unilaterally subhypsodont, relatively low-crowned; sinus separated from both fold I and fold II in Dp4 and extending into mesoloph in P4.
According to the age-classes of the skulls proposed by Dees van Weers, the skulls of HMV 2002, HMV 2003 and IVPP V 26033 are young and belong to age-class IV, while HMV 2004 is adult and belongs to age-class VI.
The skulls are of the hystricomorphous type, relatively low and wide, and have a large infraorbital foramen.
The skull is long ovoid in outline, with relatively narrow rostrum and occipital part. The nasals are slightly longer than wide, with a slightly convex dorsal surface and a posteriorly convex posterior border, which is located much more posteriorly than the premaxillo-frontal suture and nearly aligned with the lacrimal. The premaxillo-frontal suture extends transversely. The maxillo-frontal suture extends obliquely, from the premaxillofrontal suture to the lacrimal. The lacrimal is situated mainly within the orbit, with only a small part exposed on the dorsal side at the anteromesial corner of the orbit, where a distinct lacrimal tubercle forms. The orbit is large and the postorbital process is distinct. The frontals are wide and have convex dorsal surface, but shorter than the nasals. The frontoparietal suture is M–shaped, roughly aligns with the posterior zygomatic root. Starting from the postorbital processes, the two weak parietal crests are convergent posteriorly to meet each other forming a short sagittal crest, which reaches to the distinct nuchal crest. The parietal is slightly smaller than the frontal and has slightly concave surface. The interparietal is bell-shaped, inserting between the two parietals.
The skull is relatively low, with a slightly convex roof. The anterior end of the nasal is situated posterior to that of the premaxilla. The incisura nasomaxilla is small and shallow. The rostrum is high and short. On the lateral side of the rostrum there is a large concave surface, which is for the insertion of the masseter profundus muscle. The large infraorbital foramen is within the maxilla and its posterior border is above the M1 in position. The anterior border of the large orbit is situated above M2, and the postorbital process is above M3 or slightly posterior to M3. The lacrimal tubercle is located at the anterosuperior corner of the orbit. The bridge between the infraorbital foramen and the orbit is wide and thin-plate in form. The zygomatic arch is formed by zygomatic process of maxilla, jugal, and zygomatic process of the squamosal. The anterior zygomatic root formed from the maxilla is located near the anterior part of DP4 (P4). The anterior part of zygomatic arch (the inferior margin of infraorbital foramen) is a slim triangular plate, and its posterior part (inferior margin of orbit) forms a transversely thin and vertically wide plate. The small premolar foramen is located on the mesial wall of the infraorbital foramen, above the anterior border of Dp4 (P4). The sphenopalatine foramen is large and located above M1‒2. The optic foramen is relatively small and located above the posterior border of M3 or slightly posterior to M3 and superoposteriorly to the sphenopalatine foramen. The large anterior alar fissure is located inferolaterally to the optic foramen. The tiny ethmoidal foramen is located near the superior border of the orbit and posteriorly to the lacrimal tubercle.
The diastema between I2 and DP4 (P4) is short compared with the upper cheek tooth row (ratios of length of diastema to that of P4‒M3 are 1.16 and 1.18 in HMV 2004). The incisive foramen is small and located at the anterior 1/3 of the diastema. A pair of tiny interpremaxillal foramina are located between I2 and the incisive foramen. The premaxillomaxillal suture extends anteromesially and passes the posterior end of incisive foramen. On the anterior part of the maxilla there is a pair of bulges showing the positions of the posterior ends of the alveoli of the two I2s. Between the P4 (dp4) and the premaxillo-maxillal suture there is a large concave area, which may be the site for the insertion of m. buccinator. In front of P4 (dP4) and near the mid-maxillal suture there is a pair of small posterior palatine foramina. The left and right cheek tooth rows are slightly convergent posteriorly (in young) or parallel to each other (in adult). On the hard palate between the two teeth rows there are several nutrient foramina. The transversely extending mesial part of the maxillo-palatine suture aligns with the boundary between M1 and M2 (in HMV 2002 and HMV 2003) or with anterior part of M2 (in HMV 2004 and V 26033). The posterior border of the hard palate (anterior border of the mesopterygoid fossa) is situated mesial to the M2 (in HMV 2002, HMV 2003 and V 26033), or to the anterior part of M3 in adult (HMV 2004), and usually has a small protrusion at the middle. The mesopterygoid fossa is large and wide. The pterygoid fossa is very narrow and small, with an internal pterygoid process higher than the external pterygoid process. The posterior foramen of alisphenoid canal penetrates the posterior part of the external pterygoid process. The masticatory foramen, buccinator foramen and deep temporal foramen are confluent into one foramen. The posterior foramina of the three nerve canals mentioned above are also confluent into one, which is located dorsoposterior to the ascp and anteroventral to the foramen ovale. The foramen ovale is confluent with the middle lacerate foramen.
The two zygomatic arches are slightly divergent posteriorly. The glenoid fossa of the squamosal takes a form of short and wide groove which is longitudinally straight but transversely concave. The small auditory bulla has a short external auditory meatus. The bulla has a spherical surface. The stylomastoid foramen is located between the bulla and the mastoid process. The jugular foramen is located mesioposterior to the bulla. The hypoglossal foramen is located lateral to the basioccipital and anterior to the occipital condyle.
Skulls of Hystrix brevirostra from Linxia Basin, Gansu (A) IVPP V 26033: (A1) ventral view, (A2) posterior view; (B) HMV 2004: (B1) occlusal view of left and right upper cheek teeth, (B2) ventral view of skull Abbreviations: eoc, external occipital crest; fm, foramen magnum; loc, lateral occipital crest; nc, nuchal crest; occ, occipital condyle; pmp, paramastoid process. Scale bar ($) relates to (A1), (A2), and (B2); (#) relates to (B1). Wang & Qiu (2020).
The nuchal surface is about semicircular in outline, rather flat and nearly vertical to the ventral surface of the skull. The external occipital crest is developed and extending from nuchal crest to the superior border of foramen magnum. On the two lateral areas of eoc there is a pair of vertical crests, which may be the lateral borders of the area for insertion of m. rectus capitis dorsalis minor, called here as lateral occipital crests. The paramastoid process is developed. The foramen magnum is ovoid in outline. The two occipital condyles are separated widely.
Both HMV 2002 and HMV 2003 preserve left and right hemimandibles. The mandible is of hystricognathous type, with the angular process extending laterally to the horizontal ramus. The horizontal ramus is straight and low. The symphysis extends posteriorly to below the anterior root of dp4. The mandibular diastema is shorter than dp4‒m2 in length and is deeply concave with a steep posterior part. The mental foramen is located below the anterior root of dp4 (p4) in the middle height of buccal side of the horizontal ramus. The masseteric fossa is large. The distinct masseteric ridge extends anteriorly to below the m1, nearly at the same horizontal level of the mental foramen. The ascending ramus of mandible is short and low, and extends slightly laterally to the cheek tooth row. The coronoid process is very low and small, with its anterior border rising from lateral side of horizontal ramus below m1 and its top being slightly higher than the occlusal surface of the lower cheek tooth row. The condyloid process is higher and larger than the coronoid process, and has an ovoidhemispherical articular facet. The angular process is small and bends slightly lingually below the condyloid process. On the lingual side of the ascending ramus the mandibular foramen is situated posterior to the m3. The mdf may be represented by a large single foramen (in HMV 2002) or may be separated into three small ones (in HMV 2003). The internal pterygoid fovea is large and deeply concave, with its anterior end extending to below m2 and its lower margin rolling up lingually.
The dental formula is 1·0·1·3/1·0·1·3. The cheek teeth are unilaterally subhypsodont, with the lingual side higher (lower) than the buccal side on the upper (lower) cheek teeth respectively.
The I2 is orthodont, with its anterior end bending ventrally or slightly backwards. In V 26033 the two I2s have longer and more curved anterior parts, which may represent an abnormal phenomenon. The cross section of the I2 is ovoid, with a wider and slightly convex labial surface. The enamel covers the labial side, about 1/3 medial and 1/2 lateral sides. The surface of labial side is smooth and no longitudinal ridge can be seen on it.
P4 and dP4: HMV 2004 is an adult individual and preserves P4‒M3. The P4 is the largest of the upper cheek teeth. It is ovoid in outline, slightly longer than wide, with a convex anterior border. The buccal end of fold I is shallowly open (on right P4) or closed with wear (on left P4). Fold II on the right P4 is buccally open, extending upwards almost to the base of the crown on the buccal wall. Fold II on the left P4 is Y-shaped, embracing the enlarged mesostyle. Fold III and IV join together to form a U-shaped fold, which is closed buccally. The protocone joins the anteroloph, protoloph and mesoloph. The anteroloph is shorter than the other lophs. The sinus is short transversely and extends into the mesoloph and does not meet the fold II. Its lingual opening extends upwards almost to the upper 3/5 of the crown height on the lingual side.
HMV 2002, HMV 2003 and V 26033 are all young, and have erupted dP4‒M2 and M3 still in alveolus. The dP4 is smaller than M1 in size and trapezoid in outline, slightly longer than wide, with buccal side longer than lingual one. In HMV 2002 and V 26033 the fold I‒III remain shallowly open buccally, but in HMV 2003 the buccal end of the anteroloph begins to join the paracone to close fold I on buccal side. In all the dP4, mesoloph, fold III and metaloph are L-shaped. Fold IV forms a small closed basin. The paracone and mesostyle are usually distinct cusps in HMV 2002 and V 26033, and in HMV 2003 the mesostyle forks buccally. The sinus extends anterobuccally, but does not join with fold I or fold II.
M1 is rectangle in outline, slightly longer than wide in young, but wider than long in adult. In HMV 2002 fold I is open bucally and the paracone extends anteriorly. Thus, the buccal opening of fold I is shallower and easily to be worn out. In the other specimens, fold I is closed buccally. The buccal ends of fold II and III are open shallowly or closed with wear. As in dP4 the mesoloph of M1 is L-shaped and its lingual part extends posteriorly to join the posteroloph. The metaconule is variable: it may be a distinct cusp and the metaloph is only a transverse loph (as in HMV 2002); or it may extend posteriorly to meet the posteroloph forming an L-shaped metaloph (in other specimens). Thus, fold IV may join with fold III to form a U-shaped fold (as in HMV 2002) or may be a closed basin (as in other specimens). In any case, the buccal end of fold IV is closed. The sinus extends anterobuccally to join with fold II in the young, but is separated from the latter in adult. Its lingual end is open and extends upwards to about 1/3 of the crown on the lingual side in young, but closed in adult.
M2 is trapezoid in outline, longer than wide, with a slightly narrower posterior side than anterior side in young, but is rectangular in adult. The other features of M2 are similar to M1.
M3 of HMV 2004 is trapezoid in outline, with shorter and convex lingual and posterior sides. Fold I‒IV and the sinus are all closed. The sinus extends nearly longitudinally towards the fold I. Fold III and IV are transversely long folds. M3 of V 26033 is ovoid in outline, longer than wide, with a narrower and convex posterior border. It is unworn, with the occlusal feature similar to that of M2 of HMV 2002.
The i2 is slightly curved and its anterior part extends anterosuperiorly, and the posterior end extends posteriorly to the mandibular foramen. The cross section of the i2 is narrowly ovoid, with a slightly convex labial surface. As in the I2, the enamel covers the labial side, 1/3 medial and 1/2 lateral sides. The surface of labial side is smooth and no longitudinal ridge is seen on it.
The dp4 is ovoid in outline, longer than wide and with a narrow and convex anterior border. Fold I is a small closed basin. The metalophid curves anteriorly, with its middle part meeting the mesolophid to separate fold II into two parts: the lingual one may open lingually (in HMV 2002) or may be closed (in HMV 2003); the buccal one is a closed fold. The mesolophid is variable: it may be a single lophid, or may be separated by small folds into several ones. Fold III is open lingually. Fold IV is closed lingually. There are some protrusions in fold III and IV. The sinusid is open buccally and its lingual end may or may not join with fold IV. The dp4 has three roots: a large anterior one and two small posterior ones.
The m1 is rectangular in outline, longer than wide. The metalophid is a very small circle and closes fold I into a very tiny basin. The mesolophid curves anteriorly to meet the anterolophid. Thus, fold II is L-shaped or U-shaped. Its lingual end is open. The hypolophid is long and may or may not join the posterior arm of the protoconid. Fold III is long and curved and sometimes there are some small protrusions in it. Fold IV may or may not join with the sinusid, and there are also some protrusions in it. The lingual openings of fold II‒IV are very shallow and easily to be closed with wear. The buccal opening of the sinusid is deep and extends downwards nearly to the 2/3 crown height on the buccal side.
The m2 is similar to m1 in outline and structure. But it is scarcely worn and no dentine is seen on the occlusal surface. The m2 has four roots: two small anterior and two large posterior ones.
The thoracic vertebra of HMV 2002 preserves spinous process, vertebral body, pedicle, transverse process, pre- and postzygapophyses. The long spinous process extends vertically, with ridged anterior and posterior borders. The vertebral body is short. The caput and vertebral fossa are triangle-shaped, but their epiphyses are lost. On either of the left and right lateral borders of the caput and vertebral fossa there is an articular facet for the head of the rib. The prezygapophysis extends forwards from the pedicle. The articular facet on the prezygapophysis is oval in outline, slightly concave, facing superomesially. The postzygapophysis is located on the posterior part of the pedicle. The articular facet on the postzygapophysis is oval, slightly concave, and facing inferomesially. The robust transverse process extends laterally from the pedicle, situated lower than the pre- and postzygapophyses in position. Its distal end is damaged.
The above described skulls are similar to the genus Hystrix rather than to Atherurus and Trichys in being large in size; skull having convex roof, enlarged nasal cavity; long and wide nasal with a convex dorsal surface and posteriorly convex posterior border; frontal being shorter than nasal, but larger than parietal in size; having large infraorbital foramen and small and round auditory bulla, etc.
In comparison with the known Pleistocene and living species of Hystrix, including Hystrix brachyura, Hystrix subcristata, Hystrix hodgsoni, Hystrix cristata, Hystrix indica, Hystrix javanica, Hystrix kiangsenensis, Hystrix largrelii, Hystrix zhengi and Hystrix magna etc. the specimens described by Wang and Qiu are different from them in cheek teeth being lower crowned. Besides, the specimens are larger than Hystrix brachyura, Hystrix subcristata, Hystrix hodgsoni, Hystrix cristata, Hystrix indica, Hystrix javanica, Hystrix kiangsenensis and Hystrix largrelii in size. In addition, they differ from Hystrix lagrelii, Hystrix brachyura, Hystrix indica and Hystrix javanica in having enlarged nasal; from Hystrix hodgsoni, Hystrix subcristata and Hystrix magna in skull being lower and wider, with less vaulted dorsal surface, smaller nasal cavity and shorter nasal.
Neogene Hystrix is known including 11 species: Hystrix parvae, Hystrix primigenia, Hystrix sivalensis, Hystrix leakeyi, Hystrix refossa, Hystrix depereti, Hystrix aryaensis, Hystrix trofimovi, Hystrix caucasica, Hystrix gansuensis and Hystrix lufengensis.
In comparison with these Neogene species of Hystrix the specimens described by Wang and Qiu are larger than Hystrix parvae, Hystrix leakeyi and Hystrix aryaensis; the crowns of their cheek teeth are higher than those of Hystrix parvae, Hystrix primigenia, Hystrix sivalensis, Hystrix trofimovi and Hystrix lufengensis, but lower than those of Hystrix leakeyi, Hystrix refossa, Hystrix depereti, Hystrix aryaensis, Hystrix caucasica and Hystrix gansuensis. In addition, they differ from Hystrix primigenia, Hystrix gansuensis, Hystrix depereti and Hystrix lufengensis in having shorter rostrum; from Hystrix gansuensis and Hystrix depereti in having shorter nasal; from Hystrix primigenia, Hystrix refossa, Hystrix depereti and Hystrix lufengensis in having lower horizontal ramus of mandible, and shorter and deeper concave mandibular diastema. Besides, they differ from all of the known species of Hystrix in P4 having sinus extending into mesoloph, and from Hystrix gasuensis in sinus of dP4 being separated from fold I.
The above comparison tends to show that the new specimens described above represent a new species of Hystrix, named as Hystrix brevirostra.
In 2011, Deng Tao, Hou Sukuan, Shi Qinqin, Chen Shaokun, He Wen, and Chen Shanqin, referred a skull (without mentioning the catalogue number) from Duikang (LX 200701) to Hystrix gansuensis, a species established by Wang and Qiu in 2002. According to their figure, this specimen should be the HMV 2003, the paratype of Hystrix brevirostra described by Wang and Qiu. This skull (HMV 2003) is different from Hystrix gansuensis in having shorter rostrum and nasal, cheek teeth being lower crowned and differing in occlusal features. The skull (HMV 2003) should be referred to the new species, Hystrix brevirostra rather than to Hystrix gansuensis as Deng et al. did.
There are considerable ontogenetic variations in Hystrix brevirostra: among the four skulls three (HMV 2002, 2003 and V 26033) are young and one (HMV 2004) is an adult individual. Although all the three young skulls are lumped to IV stage based on Dees van Weers system, their individual ages are not the same: in HMV 2002 and HMV 2003 the M3 are still in their alveoli, while in V 26033 M3 begins to erupt. Thus, V 26033 is slightly elder than the other two in age. In observing and describing the skulls we found the following variations in the four skulls: (1) The posterior border of the hard palatine is variable in position: it alignes with the sinus of M2 in HMV 2002 and HMV 2003, with the posterior part of M2 in V 26033, and with the anterior part of M3 in HMV 2004. It would mean that the posterior border of the hard palatine of Hystrix brevirostra moves posteriorly with age in young individuals. (2) The posterior border of nasal is above M2 (in young), but moves to above M3 (in adult) in the position, again moving posteriorly with age in young individuals. (3) The two upper tooth rows are slightly convergent posteriorly in young individuals, but parallel to each other in adult.
Wang and Qiu previously discussed the evolutionary tendencies among the species of Hystrix. Most of these evolutionary tendencies are substantiated by the new species. They are: skull changed from relatively lower and wider to higher and narrower in proportion; the rostrum became higher; the nasals and frontals enlarged; the crown of the cheek teeth became more hypsodont; and M3/m3 became reduced. Based on these evolutionary tendencies, it is obvious that Hystrix brevirostra is more primitive than all of the Pleistocene and living species of Hystrix.
Up to now only three species of Hystrix have been described from the Neogene of China. They are Hystrix gansuensis, Hystrix lufengensis and Hystrix brevirostra. Hystrix brevirostra differs from Hystrix gansuensis in skull having shorter rostrum and nasal, and cheek teeth being lower crowned. On the contrary, the cheek teeth of Hystrix brevirostra are higher crowned than those of Hystrix lufengensis. Thus, Hystrix brevirostra is slightly more progressive than Hystrix lufengensis, but more primitive than Hystrix gansuensis. However, Hystrix brevirostra has a shorter rostrum than the other two species. Therefore, Hystrix brevirostra may represent a different evolutionary lineage as the other two species.
Compared with other Neogene species of Hystrix outside China, based on the crown height of the cheek teeth, it seems that Hystrix brevirostra is more advanced than Hystrix parvae, Hystrix primigenia, Hystrix sivalensis and Hystrix trofimovi, but more primitive than Hystrix leakeyi, Hystrix refossa, Hystrix depereti, Hystrix aryaensis and Hystrix caucasica. However, this should be further testified by more convincing material to be discovered in future.
The specimens of Hystrix brevirostra are collected from three different localities: HMV 2002 and HMV 2003 from Duikang (LX 200701), IVPP V 26033 from Baihuacun (LX 200205), and HMV 2004 from Shanchengcun (LX 200041). The geologic age of Duikang is known to be Lower Pliocene (Hewangjia Formation). The other fossils from Baihuacun (LX 200205) are known to include four species: Gazella cf. Gazella gaudryi, Gazella paotehensis, Hipparion coelophyes and Hipparion hippidiodus. Among them the first three are known from Late Miocene Yangjiashan fauna. The last one, Hipparion hippidiodus, has been known from Late Miocene deposits of Qingyang. The fauna from Baihuacun may be correlated with the Late Miocene Yangjiashan fauna.
The other fossils from Shanchengcun (LX 200041) are known to include 6 species: Hipparion weihoensis, Acerorhinus hezhengensis, Chilotherium wimani, Chleuastrochoerus stehlini, Cervavitus novorassiae and Muntiacus sp. According to Deng et al., Hipparion weihoensis has been known to be early‒middle Bahean ranging from Guoligou Fauna to Dashengou Fauna in age; Acerorhinus hezhengensis, Chilotherium wimani and Chleuastrochoerus stehlini are known to be middle‒late Bahean ranging from Dashengou Fauna to Yangjiashan Fauna in age; Cervavitus novorassiae is known to range from late Bahean Yangjiashan Fauna to Early Pliocene in age. Muntiacus is known to range from Late Miocene to Recent. It seems that the fauna from Shanchengcun can also be correlated with the Late Miocene Yangjiashan Fauna.
Therefore Hystrix brevirosta ranges from Late Miocene late Bahean to Early Pliocene Gaozhuangian in age.
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