Euroscaptor darwini, Nguyen & Bui & Dau & Le & Vu, 2025

Euroscaptor darwini sp. nov.

Figs 1 View Figure 1 , 2 View Figure 2 , 3 View Figure 3 , 4 View Figure 4 , 5 View Figure 5 , 6 View Figure 6 , 7 View Figure 7 , 8 View Figure 8 , 9 View Figure 9 , Tables 3 View Table 3 , 4 View Table 4 , 5 View Table 5 , 6 View Table 6 , 7 View Table 7

Material examined.

Holotype: Vietnam • ♂; Thanh Hoa Province, Ba Thuoc District, Thanh Son Commune, Pu Luong Nature Reserve ; 20°29.01'N, 105°6.11'E; approx. 935 m a. s. l.; 10 Nov. 2024; N. V. Ngan leg.; NTS.2024.PL.01 ; IB–VAST GoogleMaps . Paratypes: Vietnam • 2 ♀♀; same locality as for holotype; same coordinates; same altitude; 9 Apr. 2025; S. T. Nguyen, Y. H. Vu and N. V. Ngan leg.; NTS.2025.PL.02 , NTS.2025.PL.03 ; IB–VAST GoogleMaps ; and 2 ♀♀; same locality as for holotype; 20°28.95'N, 105°6.02'E; approx. 1007 m a. s. l.; 13 Apr. 2025; N. V. Ngan leg.; NTS.2025.PL.04 , NTS.2025.PL.05 ; IB–VAST GoogleMaps .

Diagnosis.

Euroscaptor darwini sp. nov. is clearly distinguished from congeners by its extremely short, vestigial tail, which protrudes slightly less than 2 mm beyond the skin surface. It is entirely covered by short, sparse bristle hairs that progressively lengthen toward the distal end, reaching approximately twice the length of the underlying tail. The tail is composed of only six or seven caudal vertebrae, significantly fewer than in other Euroscaptor species. The interorbital region is moderately narrow, with the inter-foraminal distance between the infraorbital foramina being conspicuously constricted. The zygomatic arches are weakly developed but exhibit an atypically elongated form. The osseous junction between the infraorbital foramina and the palate is slender and lacks lateral expansion. In lingual view of mandible, the fourth lower premolar and all three lower molars have crowns that are broader than height, with overall small tooth dimensions. The mandible is delicate, characterized by a narrow ascending ramus and fragile angular process. The pelvic girdle is delicate, markedly reduced in both size and structural robustness.

Description of the holotype.

External morphology. The holotype of Euroscaptor darwini sp. nov. ( NTS.2024.PL.021 ) is an adult male with a compact body and small overall size ( HB = 115.71 mm) (Table 3 View Table 3 ). The body is stream-lined and the head is conical, tapering smoothly anteriorly toward the snout. The body appears muscular, with a thick neck and prominent scapular region. The thorax and abdomen are proportionally broad, and the trunk is laterally compressed in dorsal view. The snout is elongated, naked, and prominently pink, with the distal portion slightly expanded into a bulbous structure. Numerous minute wart-like protuberances and well-developed vibrissae are present on the lateral and dorsal surface of the rhinarium for highly tactile function. The eyes are vestigial and not externally visible, deeply recessed beneath the skin. External pinnae are entirely absent. The nostrils open anteriorly and slightly laterally. The forelimbs are robust, with large palms and hyperdeveloped claws. Digits III and IV possess broad, chisel-shaped claws, while digit I bears a shorter but similarly broadened claw. The hindlimbs are more gracile but remain sturdy. The palms and soles are sparsely covered in naked skin and bear slightly keratinized pads.

Pelage coloration. Dense, plush, and velvety, the dorsal pelage is a uniform dark greyish-black, with a faint silvery reflection on the hair tips creating a subtly iridescent, metallic sheen under direct light. The lateral flanks blend seamlessly into the ventral region. The ventral fur is slightly lighter, ranging from dusky grey to smoky brown, most prominent around the throat, chest, and inguinal regions. The fur around the muzzle, vibrissae base, and forefoot digits is short and uniform in color. The forefeet and hindfeet are sparsely furred and show exposed pinkish skin around the digits and palms. The tail is uniformly dark grey and bristle-covered.

Tail and caudal vertebrae. The tail of E. darwini is extremely short, vestigial, with only approximately 1.5 mm protruding beyond the skin surface. The tail is nearly flush with the skin surface, with only a minute tip visible beyond the pelage. It is completely covered in sparse, short bristle-like hairs, forming a slightly tufted appearance. Osteological examination revealed a reduction in tail length, underlain by the presence of only 6 caudal vertebrae which is representing the most extreme case of caudal shortening documented within Euroscaptor (Fig. 5 View Figure 5 ).

Forefeet and claws. The forefeet are proportionally large and robust, with hypertrophied palms and prominent digital claws, particularly on digits III and IV. The first digit bears a shorter but stout claw. The claws are strongly recurved and lightly pigmented with ivory tips. Hindfeet are slender, lacking the specialization seen in the forefeet.

Cranium morphology. The cranium is diminutive, lightly built, and slender in profile, with a greatest length (GLS) of 30.51 mm falling within the lower size range documented for Euroscaptor species in Vietnam (Table 4 View Table 4 ). The rostrum is proportionally short and gradually tapered anteriorly, forming a triangular outline in dorsal view. In lateral aspect, the rostral region is straight and only slightly arched dorsally. The braincase is moderately inflated with a smoothly domed dorsal surface. The interorbital region is nearly parallel-sided, maintaining consistent height from the frontals to the parietals. The sagittal crest is absent, and the lambdoidal crest is low and rounded, contributing to the smooth contour of the posterior cranial vault. The zygomatic arches are poorly developed, lacking the thickened and laterally expanded morphology seen in larger species (Fig. 5 c View Figure 5 ). The infraorbital foramina are small and positioned close to the anterior margin of the maxillae. The auditory bullae are dorsoventrally flattened, not extending beyond the posterior margin of the skull, and lacking any significant lateral inflation. The occipital region is gently rounded, with no prominent ridges or projections.

Mandible and dentition. The mandible of holotype is delicate and moderately arched, with a slender ascending ramus and a weakly developed angular process. The lower border of the mandible is gently concave; the coronoid process is narrow and slightly recurved. The mandibular condyle is small, and the mandibular symphysis is short and tightly fused. The species retains the primitive fossorial mole dental formula: I 3 / 3, C 1 / 1, P 4 / 4, M 3 / 3 = 44. The first upper incisor (I 1) slightly recurved posteriorly and has a prominent cutting edge. I 2 and I 3 are slightly smaller than I 1, closely aligned, and gradually taper in height and volume. In the lower jaw, the first incisor (i 1) is small and curves slightly forward, while i 2 and i 3 are smaller and aligned along the lateral mandibular toothrow. The upper canines (C 1) are moderate in size, conical, and do not protrude strongly beyond the adjacent teeth, while the lower canines (c 1) are similar in shape to the three lower incisors. The premolars (P 1 – P 4 / p 1 – p 4) are asymmetrical in size. In the upper jaw, P 2 is the smallest of the series, whereas P 4 is the largest and more robust in overall dimensions — nearly 2.5 times the size of P 2. P 1 and P 3 are almost equal in crown height. In the lower jaw, there is a clear size progression, with p 4 being the largest. The p 1 and p 4 are subequal, while p 2 is slightly reduced. The upper molars (M 1 – M 3) exhibit a narrow lingual margin, and instead of hypocones, they possess well-developed metaconules, especially on P 2 and P 1, which are clearly visible from the lingual view. M 3 displays a triangular occlusal outline, with a prominent trigon and an anteriorly shifted protocone. The lower molars (m 1 – m 3) lack hypoconulids, and cuspid separation is relatively weak.

Pelvic morphology. The pelvic girdle is slender and reduced in overall robustness. The ischia are shortened and thin, contributing to a narrow pelvic outlet (Fig. 5 View Figure 5 ). The sacral vertebrae articulate weakly with the ilia, and the pelvis shows no evidence of expanded muscle attachment sites.

Female secondary sexual characters.

The adult female paratype ( NTS.2025.PL.02 ) exhibits clearly identifiable sexual characteristics indicative of reproductive maturity (Fig. 6 View Figure 6 ). External morphological inspection reveals the presence of two pairs of inguinal mammae, symmetrically positioned along the lower abdomen. The nipples are well-developed and slightly protruding, with the surrounding fur slightly parted. The most prominent external feature is a conspicuous pale-yellow ventral pattern, extending longitudinally from the lower thoracic region to the pelvic area. The streak is localized along the midline, forming a contrast with the darker grey – brown ventral pelage, and is absent in male and non-breeding female specimens examined in the series. This individual was confirmed to be gravid at the time of capture, based on visible abdominal distension and the presence of developing embryos upon dissection.

Variation.

The holotype displays a uniformly dark greyish – black dorsum with a faint silvery sheen, while the ventral surface is only marginally lighter, resulting in a nearly unicolored appearance. In contrast, female paratypes show more pronounced ventral pallor, especially in the throat and pelvic regions, sometimes accompanied by a brownish tinge around the chest. The pregnant female ( NTS.2025.PL.02 ) has a distinct pale-yellow fur area on the mid-ventral surface. Particularly, female paratypes ( n = 4) exhibit significantly larger craniodental dimensions than the male holotype (Fig. 5 View Figure 5 , Table 4 View Table 4 ). Female specimens show greater GLS (≤ 31.01 mm), maxillary toothrow length, and mandibular length in size. However, the overall dental morphology remains conserved across sexes. Variation is also apparent in tail vertebrae counts. The holotype male possesses only six caudal vertebrae, which corresponds to its externally vestigial tail. In the four female paratypes, three individuals ( NTS.2025.PL.03 , NTS.2025.PL.04 , NTS.2025.PL.05 ) also exhibit six caudal vertebrae, but the pregnant female ( NTS.2025.PL.02 ) differs in having seven (Fig. 5 g View Figure 5 ).

Etymology.

The specific epithet darwini honors the eminent naturalist Charles Darwin, whose foundational contributions to evolutionary biology have profoundly influenced modern systematics and the understanding of speciation. Darwin’s insights have had a particularly strong impact on the authors of this study. We propose “ Darwin’s mole ” as the English common name, and “ Chu ột chũi Darwin ” as the Vietnamese common name, reflecting the most prominent morphological trait and honoring the individual commemorated.

Distribution.

Euroscaptor darwini sp. nov. is currently known only from its type locality within Pu Luong NR, Thanh Hoa Province, north-central Vietnam. All known specimens were collected along a forested elevational transect on the southwestern ridge of Pu Luong Mountain, at altitudes ranging from 900 to 1100 meters a. s. l.

Ecological habitat notes.

Euroscaptor darwini sp. nov. was encountered in closed-canopy primary evergreen forest at the Pu Luong NR. The forest at the collection sites exhibits a dense, stratified structure with an upper canopy dominated by large dipterocarp and Fagaceae trees, an understory layer of palms, shrubs, and saplings, and a ground layer covered in deep leaf litter, decomposing organic material, and fine root networks. The soil is dark brown to reddish, loamy to clay-loam in texture, moist but well-drained, and free of surface rocks or exposed limestone. Specimens were collected along narrow animal paths, under thick vegetation, and beside moss-covered tree bases, where soil is particularly soft and cool. All trapping sites were located in non-karst areas with friable, humus-rich forest soils, and deep, organic substrates.

Comparisons.

The new species is distinguished from its close congeners by its truncated tail, along with distinctive cranial morphology, including a slender zygomatic arch and a narrow pelvic structure.

Euroscaptor darwini sp. nov. is most similar morphologically to E. subanura , with which it shares a markedly reduced tail length and compact body proportions. However, they differ in both craniodental morphology and external characters. Interestingly, despite the significantly narrower breadth across the interorbital foramina ( BIOF: 5.41–5.77 mm in E. darwini vs 6.07–6.46 mm in E. subanura ), the lateral zygomatic arch ( LZA) in E. darwini is remarkably elongated ( 7.88–8.22 mm), exceeding that of E. subanura (6.83–7.74). This associated with differences in the shape of the zygomatic arch: in E. darwini , the arch is slender and tapers posteriorly toward the palatine, whereas in E. subanura , the anterior part zygomatic arch is slightly expanded laterally, resulting in a more parallel configuration between the left and right arches (Fig. 7 View Figure 7 ). This zygomatic difference is further supported by comparative measurements across multiple E. subanura populations. All examined populations of E. subanura — from Tam Dao, Na Hang, Xuan Son, Ba Vi, and Pu Huong — exhibit consistently shorter LZA values (Fig. 8 View Figure 8 , Table 5 View Table 5 ).

The E. darwini displays shorter crown heights and weaker cuspid development, particularly on p 4, m 1, m 2, m 3. In dorsal view, the rostral portion of E. darwini appears narrower and more tapered anteriorly, with the interorbital region slightly more constricted. The snout breadth and palatal length are both consistently narrower in E. darwini , showing a slender craniofacial profile (Figs 7 View Figure 7 , 8 View Figure 8 ). This is supported by the shorter maxillary premolar length (P 1 – P 4: 3.99–4.11 mm in E. darwini vs 4.13–4.29 mm in E. subanura ) and the compact mandibular incisor row length (i 1 – c: 1.54–1.63 mm in E. darwini vs 1.65–1.88 mm in E. subanura ) (Table 4 View Table 4 ). Furthermore, dental spacing and size differentiation are pronounced: I 1 in E. darwini is medium size and curved, but smaller than that of E. subanura , and the spacing between I 2 and I 3 is more compressed. The lower incisors and premolars also follow a progressive enlargement posteriorly, but are overall less massive and vertically developed in E. darwini , contributing to a reduced masticatory apparatus.

In terms of external measurements, E. darwini displays a shorter tail than E. subanura , with tail lengths ranging from 2.11–3.74 mm compared to 2.5–5.0 mm as reported by Kawada (2016) and Bui (2022). This difference occurs despite overlapping head – body lengths: 115.71–127.93 mm in E. darwini vs 113.0– 131.5 mm and 107.0– 130.5 mm in E. subanura ( Kawada 2016, Bui 2022), resulting in a lower tail to body length ratio (1.82–2.92 %) compared to E. subanura (1.96–4.24 % and 2.33–3.85 %) (Table 3 View Table 3 ). This external truncation is supported by osteological evidence: E. darwini possesses only six or seven caudal vertebrae, whereas E. subanura retains nine or ten.

Euroscaptor darwini possesses an overall smaller skull compared to E. ngoclinhensis , as reflected by shorter measurements in GLS ( 30.51–31.01 mm vs 31.83–33.03 mm), LZA ( 7.88–8.22 mm vs 8.11–8.72 mm), and mandibular length ( ML: 18.93–19.37 mm vs 19.91–21.01 mm). It also has a narrower interorbital breadth ( BIOF: 5.41–5.77 mm vs 6.16–6.46 mm) and a shorter lower post third-premolar toothrow (p 4 – m 3: 6.07–6.47 mm vs 6.51–6.89 mm). The upper toothrow (I 1 – M 3) is reduced in length ( 11.51–12.02 mm in E. darwini vs 12.17–12.44 mm in E. ngoclinhensis , and up to 13.0 mm in E. parvidens and E. kuznetsovi ). The distance between lower incisor-canine (i 1 – c) is also shorter ( 1.54–1.63 mm), representing the smallest value recorded within the genus.

Compared to E. parvidens , the cranium of E. darwini is more slender, with a narrower basal breadth and reduced palatal length. GLS is significantly shorter ( 30.51–31.01 mm vs 33.53–34.76 mm), BB is narrower ( 13.77–14.26 mm vs 14.11–15.32 mm), and the width between upper canine CCW is reduced ( 3.64–3.85 mm vs 3.79–4.41 mm). The mandible is likewise smaller ( ML: 18.93–19.37 mm vs 20.61–22.02 mm), with shortened m 1 – m 3 ( 4.89–5.29 mm vs 5.17–5.59 mm), i 1 – p 1 ( 2.95–3.19 mm vs 3.52–3.88 mm) segments, yielding a more compact jaw proportion.

Euroscaptor darwini differs from E. orlovi and E. kuznetsovi in having a smaller cranium, shorter palatal length (PL: 11.61–12.16 mm vs 13.31–13.65 mm in E. orlovi ), and lesser posterior zygomatic root width (PZRW: 10.09–10.37 mm vs 10.44–10.79 mm). These proportions result in a noticeably more compact and domed neurocranial profile in dorsal view. Furthermore, the upper molars of E. darwini are less transversely expanded than those of E. kuznetsovi , as indicated by a narrower M 2 – M 2 width ( 6.71–7.17 mm in E. darwini vs ≤ 7.8 mm in E. kuznetsovi ). The mandibular symphysis in E. darwini is relatively shorter and more vertically aligned, contributing to a blunter jaw profile compared to the more elongated mandibles seen in larger Euroscaptor .