Bubalus arnee (Kerr, 1792)

Suraprasit, Kantapon, Jaeger, Jean-Jacques, Chaimanee, Yaowalak, Chavasseau, Olivier, Yamee, Chotima, Tian, Pannipa & Panha, Somsak, 2016, The Middle Pleistocene vertebrate fauna from Khok Sung (Nakhon Ratchasima, Thailand): biochronological and paleobiogeographical implications, ZooKeys 613, pp. 1-157 : 47-52

Taxon classification Animalia Artiodactyla Bovidae

Bubalus arnee (Kerr, 1792)

Referred material.

A nearly complete cranium associated with a right mandible, DMR-KS-05-03-20-1; a cranium with a right tooth row (P3-M3), DMR-KS-05-03-21-1; a partial cranium with two tooth rows (P3-M1), DMR-KS-05-03-16-3; a partial cranium with a right tooth row (P3-M3), DMR-KS-05-03-11-1; three horn cores-DMR-KS-05-03-16-2 (right), DMR-KS-05-03-31-6 (right), and DMR-KS-05-03-19-28 (left); a left P2, DMR-KS-05-03-18-14; a left DP3, DMR-KS-05-03-00-103; two right P3-DMR-KS-05-03-22-14 and DMR-KS-05-04-05-3; a right DP4, DMR-KS-05-04-29-8 (broken anterior lobe); two P4-DMR-KS-05-03-18-13 (right) and DMR-KS-05-03-18-9 (left); four M1-DMR-KS-05-03-31-5 (right), DMR-KS-05-03-18-12 (right), DMR-KS-05-03-18-6 (left), and DMR-KS-05-03-22-13 (left); five M2-DMR-KS-05-03-00-2 (right), DMR-KS-05-03-25-21 (right), DMR-KS-05-03-18-5 (right), DMR-KS-05-03-16-2(1) (left), and DMR-KS-05-03-18-7 (left); four M3-DMR-KS-05-03-00-7 (right), DMR-KS-05-03-22-12 (left), DMR-KS-05-03-14-1 (left), and DMR-KS-05-03-18-10 (left); a right mandible with p2-m1, DMR-KS-05-03-20-2; three left mandibles-DMR-KS-05-03-10-3 (with p2-m3), DMR-KS-05-03-20-10 (with p2-m1), and DMR-KS-05-03-20-20 (with m1 and m2); a right i1, DMR-KS-05-03-18-8; a right i2, DMR-KS-05-03-22-15; a left i3, DMR-KS-05-03-00-106; a right i4, DMR-KS-05-03-16-3; a right p3, DMR-KS-05-03-14-4; a left dp4, DMR-KS-05-03-00-4; a right p4, DMR-KS-05-03-19-6; four m1-DMR-KS-05-03-25-3 (right), DMR-KS-05-03-18-18 (right), DMR-KS-05-03-00-105 (left), and DMR-KS-05-03-00-3 (left); two m2-DMR-KS-05-03-27-12 (right) and DMR-KS-05-03-25-2 (left); two m3-DMR-KS-05-03-18-11 and DMR-KS-05-04-29-2 (left posterior lobe); eleven thoracic vertebrae-DMR-KS-05-04-1-11 (T3), DMR-KS-05-04-1-26 (T4), DMR-KS-05-04-1-13 (T5), DMR-KS-05-04-1-14 (T6), DMR-KS-05-04-1-15 (T7), DMR-KS-05-04-1-16 (T8), DMR-KS-05-04-1-12 (T9), DMR-KS-05-04-1-17 (T10), DMR-KS-05-04-1-18 (T11), DMR-KS-05-04-1-19 (T12), and DMR-KS-05-04-1-20 (T13); four lumbar vertebrae-DMR-KS-05-04-1-24 (L1), DMR-KS-05-04-1-23 (L2), DMR-KS-05-04-1-22 (L3), and DMR-KS-05-04-1-21 (L4); two humeri-DMR-KS-05-03-31-1 (right) and DMR-KS-05-03-31-8 (left); two scapulae-DMR-KS-05-03-26-2 (right) and DMR-KS-05-02-20-4 (left); three ulnae and radii-DMR-KS-05-03-00-61 (right), DMR-KS-05-03-31-2 (right) and DMR-KS-05-03-31-9 (left); a right metacarpus, DMR-KS-05-03-26-3(1); a pelvis, DMR-KS-05-04-1-25; two femora-DMR-KS-05-04-1-1 (right) and DMR-KS-05-04-1-2 (left); a right fragmentary femur, DMR-KS-05-03-20-8 (distal part); three tibiae-DMR-KS-05-4-1-11 (right), DMR-KS-05-04-1-3 (left), and DMR-KS-05-03-20-9 (left); two fourth tarsal bones-DMR-KS-05-04-1-7 (right) and DMR-KS-05-04-1-5 (left); three metatarsi-DMR-KS-05-04-1-8 (right), DMR-KS-05-04-1-6 (left), and DMR-KS-05-03-28-30 (left); a left astragalus, DMR-KS-05-04-1-4; a left phalanx I, DMR-KS-05-04-1-9; a left phalanx II, DMR-KS-05-04-1-10.

Material description.

Crania and upper dentition: DMR-KS-05-03-20-1 is undeformed and nearly complete (for measurements, see Appendix 14). Only the right maxilla, squamosals, and basicranium are damaged (Fig. 30 A–C). The horn cores are broken at their middle portion. The cross-section of the horn core base is subtriangular and anteriorly flat (Fig. 30A). The frontals are narrow between the orbits and are flat or slightly convex at the region between horn core bases (Fig. 30A, C). The supraorbital foramina are large. The orbits face slightly forward (Fig. 30A, B), not laterally like Leptobos brevicornis and Bubalus teilhardi ( Dong et al. 2014). The lateral margins of the premaxilla are concave (Fig. 30B).

DMR-KS-05-03-21-1, a juvenile cranium, is incomplete but slightly deformed. The posterior part of the skull is almost complete but the anterior part is broken (Fig. 30D, E). The cranium is likely elongated and laterally compressed (Fig. 30D). This specimen preserves two horn cores (broken at the right one) and a right tooth row with the M1, the P3 and P4 roots, and the unerupted M2 and M3 (Fig. 30E). The horn cores of DMR-KS-05-03-21-1 are slender, straight, and inclined upward and backward, and bend outward (Fig. 30D), similar to that of recent Bubalus arnee (e.g., MNHN-ZMO-1863-65). The horn cores are subtriangular in cross-section base, becoming subrounded toward the apex (Fig. 30D). The divergent angle between the horn cores is 105°. The frontals are short and narrow, forming an obtuse angle with the occipital plane. The parietals merged together. The occiput extends so far, posterior to the horn core bases. The basioccipital is laterally concave and triangular in outline (Fig. 30E).

DMR-KS-05-03-11-1 preserves the right zygomatic bone and the premaxilla and maxilla with a nearly complete tooth row (P3-M3) (Fig. 30F, G). Another specimen, DMR-KS-05-03-16-3, preserves the premaxilla and maxilla with P3-M1 (Fig. 30H, I). In dorsal and ventral views, the lateral margins of the premaxilla are concave, as expected for Bubalus (Fig. 30H).

Three isolated horn cores (DMR-KS-05-03-16-2: Fig. 30J, DMR-KS-05-03-31-6, and DMR-KS-05-03-19-28) are incomplete. The apical portion is broken away on each specimen. All horn cores are robust, long, and curved backward. Their anterior and dorsal surfaces are flat and their cross-sections are subtriangular at the base (Fig. 30J).

Upper cheek teeth of Bubalus arnee are more robust, compared to those of Bos . P2 (DMR-KS-05-03-18-14: Fig. 30K) is elongated. The parastyle on the P2 is less developed than that on the P3 and P4. The molarized DP3 (DMR-KS-05-03-00-103: Fig. 30L) is characterized by a well-developed buccal styles, anterior cingulum, entostyle, and spur, and a larger posterior lobe. The P3 is subtriangular in outline and is marked by a distinct parastyle, paracone rib, and metastyle and a U-shaped fossette (Fig. 30G, I). The parastyle of the P3 often curves posteriorly. The DP4 (DMR-KS-05-04-29-8: Fig. 30M) is also molarized with the broken protocone. This specimen has well-developed buccal styles and two separate medial fossettes. The entostyle curves posteriorly in occlusal view and is positioned more lingually than the protocone and hypocone. The P4 is similar in morphology to the P3, but is more anteroposteriorly compressed.

Upper molars display Bos -like patterns (e.g., the degree of the hypsodonty and selenodonty and the presence of distinct styles) but are more robust than most species of Bos (e.g., Bos sauveli and Bos javanicus ) (Tab. 15). However, the mesostyles of upper molars of Bubalus arnee are more developed than those of Bos . The medial fossette between the anterior and posterior fossettes (infundibula) is well-developed, often separating into two or three islands with wear (Fig. 30G, I, N). The infundibula are U-shaped but sometimes become metacentric chromosome-shaped due to strong wear, like in Bos sauveli (Fig. 30G, N). In occlusal view, the entostyle is long and straight or curves posteriorly, depending on the stage of wear, but is never bifurcated (Fig. 30G, I, N). The small fossette is sometimes present within the entostyle in relation to strong wear (Fig. 30N).

Mandibles and lower dentition: five mandibles: DMR-KS-05-03-20-1 (Fig. 31A, B), DMR-KS-05-03-10-3 (Fig. 31C, D), DMR-KS-05-03-20-2 (Fig. 31E, F), DMR-KS-05-03-20-10 (Fig. 31G, H), and DMR-KS-05-03-20-20 (Fig. 31I), are almost complete (for measurements, see Appendix 13). The first specimen is associated with the cranium. The right specimen DMR-KS-05-03-20-2 and the left specimen DMR-KS-05-03-20-20 belong to the same individual, bearing p2, dp3, dp4, and an unerupted m2. The left one is very fragmentary. Another mandible DMR-KS-05-03-20-10 is nearly complete, preserving the mandibular symphysis and bearing an unerupted m2, but lacking all incisors. All incisors drop out of the mandibles. The isolated lower incisors are spatulate in shape (Fig. 31 J–L). The i2 is similar in size to the i3 (Tab. 15).

All lower cheek teeth are robust. All lingual stylids are distinct. The p2 has a well-developed postentocristid and posthypocristid (Fig. 31B, D, F, H). The metaconid is positioned more lingually than all of lingual cristids. The dp3 is elongated (Fig. 31F, H). The postprotocristid is large and the metaconid is well-developed. A small anterior fossette is present with wear. The p3 displays a well-developed preprotoconulidcristid and a posteriorly bending metaconid (Fig. 31B, D). The isolated dp4 (DMR-KS-05-03-00-4: Fig. 31M) is trilobed and elongated with a well-developed stylids (anterior and posterior ectostylid, parastylid, metastylid, and entostylid. On the dp4, the buccal outline of the protoconulid, protoconid, and hypoconid is V-shaped in occlusal view (Fig. 31F, H, M). The anterior ectostylid curves slightly posteriorly in contrast to the posterior ectostylid that bends anteriorly (Fig. 31M). A large fossette is present between the medial and posterior valley in relation to middle wear stage (Fig. 31M). On the p4, the metaconid is most lingually positioned (Fig. 31B, D). The premetacristid is more developed than the postmetacristids. The postprotocristid is very anteroposteriorly constricted. The postentocristid fuses with the posthypocristid beyond the middle stage of wear.

Lower molars have well-developed stylids and conids. The metastylid is most developed on the unworn to slightly worn specimens (Fig. 31F, H, I, N and Tab. 15). The metastylid is located closely to the metaconid. In occlusal view, the anterior and posterior fossettes are U-shaped, similar to that of Bos . The entostylid is well-developed and sometimes curves anteriorly (Fig. 31F, I). On the m3, the posterior ectostylid is absent. The posthypoconulidcristid protrudes posteriorly slightly and is sometimes bifurcated (Fig. 31B, D). The back fossette is sometimes present with wear.

Postcranial remains: postcranial elements include scapulae (Fig. 32C), humeri (Fig. 32D), ulnae and radii (Fig. 32E), femora (Fig. 32H, L), tibiae (Fig. 32I, M), fourth tarsal bones (Fig. 32O), metacarpi (Fig. 32F), metatarsi (Fig. 32K, P), pha langes (Fig. 32Q, R), a pelvis (Fig. 32G), and thoracic and lumbar vertebrae (Fig. 32A, B). Most of postcranial remains belong to the same individual because they were found in connection. But some isolated specimens (scapula: DMR-KS-05-03-26-2, ulna and radius: DMR-KS-05-03-00-61, femur: DMR-KS-05-03-20-8, and metatarsus: DMR-KS-05-03-28-30) were found separately. The articulated skeletons show a typical character of Bubalus arnee whose postcranial bones are more massive and thicker than those of Bos (Fig. 32 and Appendix 1).

Taxonomic remarks and comparisons.

According to IUCN (2015), the wild forms of water buffaloes are considered as Bubalus arnee , while their domestic forms are regarded as Bubalus bubalis ( Gentry et al. 2004).

Although the cheek teeth of Bos and Bubalus are almost morphologically identical and often show highly variable occlusal morphologies in relation to the wear stages, they are distinguishable based on the dental morphology. Bacon et al. (2011) mentioned that Bubalus arnee is distinguished from Bos by several dental characters: more massive and voluminous cones, conids, and lingual stylids, more complex patterns of folded infundibula on the upper molars, U-shaped protoconids and hypoconids on the lower molars, and unbilobed entostyles and ectostylids. However, the latter two characters are highly variable with wear, as observed on many extant specimens of Bubalus arnee from MNHN, ZSM, and THNHM. Among the modern large bovids in Southeast Asia, some lower premolar (p3 and p4) and third molar features are more informative for the species identification than others ( Thein 1974). Our comparisons suggest that the cheek teeth of Bubalus arnee differ from those of Bos in having more developed mesostyles, more complex shapes of the infundibulum at the similar stages of wear, less developed or smaller metaconids and narrower postprotocristids on the p3 and p4, a presence of the small fossette within the entostyle and an absence of the longitudinal groove on the lingual surface of the entostyle on upper molars, more distinct entostylids on the m3, and a presence of the back fossette on the m3. For the incisors, it is difficult to make a morphological distinction between Bubalus and Bos . However, we assign these isolated lower incisors to Bubalus arnee because they were found together with their molars at the same spot.

As demonstrated by the scatter diagrams (Figs 26 and 27), the cheek teeth of recent Bos and Bubalus populations are highly overlapping in size. The lower molar sizes of Bubalus arnee also overlap with some fossil species ( Bubalus teilhardi and Leptobos brevicornis ). However, tooth dimensions are informative to make an ongoing distinction among the Khok Sung large bovids. The largest bovid in this locality is Bubalus arnee , followed by Bos gaurus and Bos sauveli , respectively, similar to the size tendency of their recent population (Tab. 14).