Crocidura narcondamica sp. nov.
Systematic Zoology
Class: Mammalia Linnaeus, 1758
Order: Eulipotyphla Waddell et al., 1999
Family: Soricidae G. Fischer, 1814
Subfamily: Crocidurinae Milne-Edwards, 1872
Genus: Crocidura Wagler 1832
Etymology. narcondamica: The new species is named of the type locality, Narcondam Island from where the type specimens were collected. The specific epithet is treated as a noun in apposition.
Type specimens
Holotype. Adult female, ZSI 29313, collected at Narcondam Island (13° 27.290'N, 94° 16.436'E) Andaman and Nicobar Archipelago, in the Bay of Bengal, India (Fig. 2); 11 m elevation; collected by the fourth author, April 17, 2020, at 9.58 hrs. The specimen consists of a fluid-preserved skin and cleaned skull. Skull extracted by the first author. Paratype. Locality and collector as for holotype. Adult male, ZSI 29314. The specimen consists of a fluid-preserved skin and cleaned skull. Skull extracted by the first author.
Diagnosis
The species is assigned to the genus Crocidura by having small body size and presence of three upper unicuspids. C. narcondamica sp. nov. (Fig. 1) differs from its congeners occurring in AN Archipelago, the mainland of India, and Myanmar as follows (Table 1, Supplementary Table S2): C. narcondamica sp. nov. possess darker-grey dense fur dorsally and a thick and darker tail (Fig. 1a), whereas the species known from the AN Archipelago possesses different dorsal pelage and tail; C. jenkinsi (Supplementary Fig. S3a) and C. hispida has spiny dorsal fur with slender tail, C. andamanensis has bluish-grey washed with brown and darker brown tail, C. nicobarica has bristly scooty brown dorsal fur with slender tail and C. attenuata has a soft brownish-grey dorsal fur with a slender tail2,51 (Supplementary Fig. S2a).
With regard to the head and body (HB) length of C. narcondamica sp. nov. (holotype: 67 and paratype: 63 mm) is shorter than in C. jenkinsi (107 mm), C. nicobarica (120 mm), C. hispida (85 mm), C. andamanensis (114 mm), C. fuliginosa (range 72-100 mm) and C. pullata (73-89 mm). However, the head and body length of this new species was overlapped with rest of the congeners: C. attenuata (60-89 mm), C. cranbrooki (65-86 mm), C. horsfieldii (49-71 mm), C. indochinensis (53-71 mm), C. pergrisea (65-86 mm), C. rapax (56-70 mm) and C. vorax (54-90 mm). The tail length (TL) (58.5 and 55.6 mm) of C. narcondamica sp. nov. was significantly varied from all the comparative congeners except C. attenuata (Supplementary Table S2). Although the HB and TL of the newly discovered species were overlapped with C. attenuata, the morphological characters are significantly different (soft brownish-grey dorsal pelage with a brownish slender tail; Supplementary Fig S2a).
The length of the hindfoot, relative to head and body length of C. narcondamica sp. nov. (holotype: 13.4 and paratype: 12.4 mm) also differs from two Indian species, C. pullata (14-16 mm) and C.horsfieldii (10-13 mm); two Myanmar species C. cranbrooki (14-16 mm) and C. indochinensis (10-13 mm), and two species C. fuliginosa (15-19 mm) and C. rapax (11-13 mm) sharing their range distribution in both India and Myanmar. However, the rest of the congeners known from the same biogeographic regions showed overlapped length of the hindfoot (Supplementary Table S2).
With regard to the craniodental characters, the newly discovered species were further examined and compared with the closest congener C. attenuata (Fig. 3, Supplementary Fig. S2). The braincase (BC) of C. narcondamica sp. nov. is rounded and elevated (Figs. 1b and 1d), with weak lambdoidal ridges (LR; Fig. 1b) than that of C. attenuata (slightly flattened with developed LR (Supplementary Figs. S2c and S2e). The foramen ovale (FO)-openings are more prominent than in C. attenuata (Fig. 3b). In C. narcondamica sp. nov., the condylobasal length (holotype: 19.6 and paratype: 18.9 mm), palatal length (7.4 and 7 mm), upper toothrow (8.8 and 7.9 mm ), maxillary toothrow (7.7 and 7 mm) and mandible length (11.6 and 10.8 mm) which are significantly either higher or lower than other congeners (Supplementary Table S2). Significantly, with regard to the first unicuspid or incisor (I1) in C. narcondamica sp. nov. was less sharp and slightly protruded from rostrum than in C. attenuata (Figs. 1d and 3c).
Description of the Holotype
The new species is a medium-sized white-toothed shrew under the genus Crocidura, with the head and body length of 67 and tail length of 58.5 mm. Its pelage is shorter with dense fur; darker-grey dorsally (Fig. 1a) and slight greyish ventrally. The snout is elongated with discernible vibrissae hairs dorsally and naked and pinkish ventrally. The eyes are small and compressed by the snout muscles. The external ears are small but well visible. The tail is thick and nearly naked with sparse bristle hairs on the proximal half. The tail length is shorter than head and body length. The tail pigmentation is darker to that of the dorsal pelage. The fore and hindfoot having five pale toes with transparent claws; plantar surfaces of feet are moderately pigmented; the upper side of the toes are having hairs. The cranial bones are thin and translucent; the braincase is rounded and slightly elevated with weak lambdoidal ridges in dorsal profile (Fig. 1b). The rostrum is angled downward and a slight depression is seen in the dorsal side of above the orbital region; the zygomatic arches are incomplete (Fig. 1b). The suture between the basioccipital and basisphenoid is fully fused (Fig. 1c). The mandible is slender, with a low mandibular ramus (Fig. 1e and 1f). The dentition is unpigmented, fully erupted; the total tooth is 28 (Fig. 1c and 1d). No significant morphological variations were observed between female (holotype) and male (paratype) specimens other than its external genital organs. There was little morphometric variation among individuals between the type series (Table 1).
Distribution. Presently known only from its type locality, Narcondam Island, Andaman and Nicobar Archipelago, in the Bay of Bengal, India.
Habitat. The new species was collected from a plantation and littoral forest along the coastline at 11 m elevation. No anthropogenic disturbances were observed in the habitat (Fig. 2).
Molecular identification and phylogenetic interpretation
The partial mitochondrial mtCytb gene sequences (Accession Nos. MW417367 and MW417368) were generated from both holotype and paratype of the newly discovered shrew species and contributed to the global database (GenBank). The similarity search results in BLAST depicted 90% similarity with the publicly available sequence of Crocidura sp. collected from Xizang, China. However, the next closest results of the similarity search revealed 89.57% similarity with Crocidura sp. collected from Yunnan, China and C. attenuata (MK765768) collected from Jiangxi, China. The present dataset of 22 soricid species, including the newly described C.narcondamica sp. nov. showed an overall mean genetic distance of 23%. The highest mean genetic distance (31.7%) was observed between Feroculus and Nectogale, however the lowest (15.3%) was detected between Crocidura and Chimarrogale in the present dataset (Supplementary Table S3). The newly discovered species revealed sufficient mean genetic distances (12% to 16.6%) with other Crocidura species. Both ML and BA phylogenetic trees showed similar topologies and distinctly separated the newly described species (C.narcondamica sp. nov.) from other Crocidura congeners with high posterior probabilities and bootstrap supports (Fig. 4, Supplementary Fig. S4). The Crocidura congeners elucidate monophyletic clustering and clade separately as compared with other soricid genera.