Prosantorhinus yei, Sun & Deng & Wang, 2024

Sun, Danhui, Deng & Wang, Shiqi, 2024, Ŋe first record of the genus Prosantorhinus % Perissodactyla: Rhinocerotidae) of East Asia, Zoological Journal of the Linnean Society 202 (2), pp. 1-12 : 3-6

Prosantorhinus yei sp.nov.

( Figs 2–6 ; Tables 1–3)

Zoobank registration: urn:lsid:zoobank*org:pub: A307A235- FB07-41FF-AD68-3DA0FF60BA94 *

Holotype: IVPP V 23530 , a well-preserved and complete skull with both cheek tooth rows %less and right DP1–M3) % Figs 2–4 )*

Diagnosis: Ŋe V-shaped nasal notch with its posterior edge at the level of the middle part of P3 and anterior margin of the orbit located at the level of the anterior edge of M1 differs from P.douvillei * Ŋe upper premolars are semi-molarized with a lingual bridge between the protocone and hypocone different from P. germanicus , P. laubei , and P.douvillei * Ŋe strong constrictions of the protocone, as well as stout antecrochet and crochet on molars, differ from P. laubei and P. shahbazi * Ŋe multiple crochet on the upper premolars and the present crista on P3 differ from P. germanicus , P. laubei , and P. douvillei * Ŋe cement on the cheek teeth is developed differently from P. germanicus , P. laubei , and P. douvillei *

Etymology: Ŋe species’ name is in honour of Professor Jie Ye, who has made great contributions to Neogene palaeontology and stratigraphy in the ºongxin area*

Type locality and horizon: Zhang’enbao Formation exposed in Lijiazhuang in Shishi ºownship, ºongxin County, Wuzhong City, Ningxia Hui Autonomous Region, China; Middle Miocene* Description

Cranium: IVPP V 23530 is a well-preserved and complete adult skull with moderately worn cheek teeth %Fig* 2)* In the dorsal view %Fig* 2A), the nasal suture between both nasals is observable, and the rostral end of the nasal bone is very rugose, indicating the presence of a nasal horn* Ŋe nasal bone becomes narrow gradually before the orbits %i*e* the nasal base does not have a constriction)* Ŋe skull roof has the widest distance at the level of the supraorbital processes, at 154* 96 mm * Ŋe parietal crests are not fused to a sagiưal crest, and the minimal separation is 46* 28 mm * Ŋe width of the occipital crest is 137* 32 mm * In the lateral view %Fig* 2B), the dorsal skull profile is concave* Ŋe nasal bone has a slightly upturning anterior part, and the occipital part is raised* Ŋe premaxillae are not preserved* Ŋe nasal bone is short and stout* Ŋe nasal notch has a V-shaped outline, and its posterior edge is at the level of the middle part of P3* Ŋe distance between the posterior edge of the nasal notch and the orbit is 71* 32 mm * Ŋe infraorbital foramen is located dorsal to the level of P3 and behind the nasal notch* Ŋe position of the dorsal margin of the orbit is high, and the anterior margin of the orbit is located at the level of the anterior edge of M1* Ŋe supraorbital edge of the frontal bone has a coarse area, but lacks any process or tubercle* Ŋe posterior orbital border is formed by the zygomatic bone, and presents a coarse area, without any tubercle* Ŋe zygomatic arch is thin %particularly the posterior part), the anterior end of which is located at the level of M1 and close to the cheek tooth row, and the posterior end of the dorsal edge has a short process* Ŋe temporal articulation for the mandible protrudes from the ventral edge of the zygomatic arch* Ŋe postglenoid process is laterally flaưened* Ŋe occipital part is raised, with the occipital face slightly inclined anteriorly in lateral view* Ŋe post-tympanic process is short and fused with the paraoccipital process, and contacts anteriorly with the postglenoid process* Ŋe upper edge of the external auditory pseudomeatus is short and located in the lower half of the occipital crest* Ŋe area between the temporal and occipital crests is depressed* In the ventral view %Fig* 2C), the medial edge of the cheek tooth row is nearly straight, and the lateral edge is arched* Ŋe anterior edge of the posterior nares is U-shaped in outline, at the level between M2 and M3* Ŋe posterior edge of the lateral wall of the posterior nares with a steep part is continuous, extending to the foramen lacerum anterius that is at the back of the level of the temporal condyle* Ŋe temporal condyle is high, and its transverse axis is concave posteriorly* Ŋe tympanic bulla has been crushed, exposing the inner bones* Ŋe alar foramen is opened on the lateral wall of the posterior nares, anteroposteriorly at the level of the temporal condyle* Ŋe post-tympanic process is wide, transversely extending to the level of the lateral half of the temporal condyle* Ŋe hypoglossal foramen is laterally positioned, at the base of the paraoccipital process* Ŋe ventral and occipital surfaces of the occipital condyle are rounded, without a median ridge* In the posterior view %Fig* 3), the occipital face is trapezoidal in outline, and the upper part is slightly narrower than the lower part* Ŋe nuchal tuberosity is strongly developed* Ŋere is a shallow notch between the base of the paraoccipital process and the post-tympanic process* Ŋe foramen magnum is small, triangular, and higher than wide* Ŋe upper margin of this foramen is narrow, inverted V-shaped, and higher than the upper margin of the occipital condyles* Ŋe occipital condyles are relatively small %ºable 1)*

Dentition: Ŋe cheek teeth have relatively low crowns, covered by abundant cement on the buccal walls and they are moderately worn %Fig* 4; ºable 2)* Ŋe ratio of the length of the upper premolars %P3–4) to the molars %M1–3) is high, more than 50%*

DP1 is fairly small and deeply worn to a flat surface with a triangular outline; the protoloph is weak and nearly worn off; the metaloph is developed; the hypocone has slight anterior and posterior constrictions; the postfosseưe is closed; the lingual cingulum is present, but the buccal cingulum is absent*

P2 is nearly quadrangular in occlusal view with a parastyle and comparatively developed paracone rib* Ŋe protocone and hypocone, with slight constrictions, connect by a lingual bridge* Ŋe hypocone is marginally larger than the protocone* Ŋe hypocone is at the same level as the metacone* Ŋe protoloph is as buccally narrow as the metaloph and joins with the ectoloph* Ŋe crochet and crista are very weak* Both the median valley and the postfosseưe are closed* Ŋe anterior and the posterior cingula are developed* Ŋe lingual cingulum is reduced around the entrance of the median valley* Ŋe buccal cingulum is absent* Ŋe cement on the buccal surface is abundant*

P3 has marked paracone and metacone ribs* Ŋe protocone has anterior and posterior constrictions, and the hypocone only has a slight anterior constriction* Ŋe protocone and hypocone connect by a lingual bridge* Ŋe protocone is slightly larger than the hypocone* Ŋe crochet and crista are weak, and the crochet is multiple* Ŋe median valley and postfosseưe are closed* Ŋe lingual margin of the protocone is convex* Ŋe anterior and posterior cingula are developed, but the lingual cingulum is reduced around the entrance of the median valley* Ŋe buccal cingulum is reduced*

P4 is similar to P3, but much larger* Ŋe hypocone is not expanded, with slight anterior and posterior constrictions* Ŋe protocone is slightly smaller than the hypocone* Ŋe lingual margin of the protocone is convex* Ŋe protoloph is shorter than the metaloph* Ŋe anterior and posterior cingula are developed, but the lingual cingulum is reduced, forming a pillar around the entrance of the median valley* Ŋe buccal cingulum is almost absent*

M1, with an undulating buccal wall, has a projecting parastyle, a marked parastyle groove, and a paracone rib* Ŋe strongly constricted protocone has a convex lingual margin, and the hypocone only has a slight anterior constriction* Ŋe crochet is short and stout* Ŋe antecrochet is strong and extends to the entrance of the median valley* Ŋe postfosseưe is round* Ŋe development of anterior and posterior, as well as lingual and buccal, cingula are similar to P4*

M2 has a narrow and long parastyle, a developed parastyle groove, and a paracone rib* Ŋe protocone is expanded, with anterior and posterior constrictions* Ŋe hypocone only has a slight anterior constriction* Ŋe crochet is well-developed* Ŋe antcrochet is strongly developed and extends to the entrance of the median valley* Ŋe antecrochet and hypocone are separated* M2 has an open median valley, a V-shaped and closed postfosseưe, and a relatively narrow and long metastyle* Ŋe development of anterior and posterior, as well as lingual and buccal, cingula are similar to P4 and M1*

M3 has a triangular outline in occlusal view* It has a short and sharp parastyle* ºhe protocone has anterior and posterior constrictions* ºhe protoloph is anteriorly convex* ºhe crochet is well-developed but does not reach the protoloph* ºhere is a reduced antecrochet that enlarges to the base of the crown* ºhe anterior cingulum is well developed, and the posterior and lingual cingula are reduced, forming a pillar*

Figures

Figure 2. Photographs and sketches of the skull of Prosantorhinus yei sp* nov*, holotype %IVPP V 23530) A, dorsal view; B, lateral view; C, ventral view*

Figure 3. Photograph and sketch of the skull of Prosantorhinus yei sp* nov*, holotype %IVPP V 23530)*

Figure 4. Photograph and sketch of upper teeth %IVPP V 23530) of Prosantorhinus yei sp* nov* in occlusal view, holotype %IVPP V 23530)*