Hylomys maxi Sody, 1933

Hinckley, Arlo, Camacho-Sanchez, Miguel, Chua, Marcus A H, Ruedi, Manuel, Lunde, Darrin, Maldonado, Jesús E, Omar, Hasmahzaiti, Leonard, Jennifer A & Hawkins, Melissa T R, 2024, An integrative taxonomic revision of lesser gymnures (Eulipotyphla: Hylomys) reveals five new species and emerging patterns of local endemism in Tropical East Asia, Zoological Journal of the Linnean Society 202 (2), pp. 1-33 : 14-15

Hylomys maxi Sody , 19&& stat. nov.

Hylomys suillus maxi Sody, 1933: 438 . Original description.

Hylomys suillus tionis Chasen, 1940: 12 .

Hylomys suillus suillus Corbet, 1988: 122 (part).

Holotype: RMNH 23895 , an adult male collected by Sody on 4 January 1930.

Type locality: ‘Giesting, Lampoengs, S. Sumatra’ (= Giesting , Mt. Tanggamus , Lampung, Sumatra, Indonesia; c. –5.44, 104.71).

Paratypes (5): Five according to Sody (1933), although Sody did not examine them: ‘For examining the Atchinese specimens I have to thank Mr. F.J. Naing-Golan’. Naturalis Biodiversity Centre holds three of these ( RMNH 23896–98 ), the other two might be lost .

Emended diagnosis: A large-sized Hylomys (average HB = 139 mm, W = 64 g, GLS = 36.9 mm) characterized by a brown suffusion in throat (from late April to mid-November but absent from late February to late April), bicoloured (except specimen RMNH 23896) and short tail (average T = 16 mm, T / HB = 11.7%), long hindfoot (average HF = 25 mm, HF + nail = 26 mm), uniformly brown-coloured and relatively short ears (average E = 16 mm, E/ GLS = 45%). Its skull can be distinguished from all relatives by its relatively larger molars (Supporting Information, File S1, Fig. S5 ) and from all relatives but allopatric H. suillus by its long and relatively broad rostrum ( Fig. 6 ). Its skull can also be distinguished from all other relatives by the combination of the following characters: obtuse-angled notch between anterior side of premaxilla; posterior end of nasals does not extend to the level of the antorbital rim; dorsal region of maxillary and frontal have a rugged appearance with capillary grooves and pores; prominent antorbital ridge/flange; anterior side of the antorbital rim is posterior to second cusp of M1; robust supraorbital processes and dentition; short alisphenoid canal (average ASC = 0.2 mm), prominent posterior cuspule in P 2 in Sumatran specimens with unworn dentition; P3 is much larger than P1; P4 has a thick labial cingulum; posterior nasal spine present; prominent occipital crest that extends more ventrally than in most other species; single root/two well fused roots in p3; anterior margin of p1 crown extends to root of c1.

Comparisons: Distinguished from parapatric H. parvus by its larger size ( HB: 123–156 mm vs. 100–115 mm, GLS: 35.5– 38.4 mm vs. 29.2–33.4 mm), relatively shorter tail (average: 16 vs. 23 mm) and harsher dorsal fur. Its skull has a more angular and robust appearance than H. parvus , its supraorbital process is well developed vs. absent in H. parvus , and its dentition is robust (particularly the canines and adjacent teeth) vs. gracile in H. parvus ( Ruedi et al. 1994) . The notch between premaxilla tips is obtuse vs. acute-angled in H. parvus . The frontal bone and dorsal region of maxillary is more rugged, with greater capillary grooves and pores, than in H. parvus . It has a prominent antorbital ridge and occipital crest, and thick P4 labial cingulum, while these are absent or vestigial/inconspicuous in H. parvus . It has a single root/two well fused roots in P2 and p3 vs. two non-fused roots in H. parvus ( Jenkins and Robinson 2002) .

Comparisons with additional species have been included in the following accounts, after such species have been formally defined.

Distribution, habitat, and natural history: Currently known from forests between c. 100 and 2000 m a.s.l. on Sumatra and 600 and 1700 m a.s.l. on the Malay peninsula, possibly extending north up to the Kangar Pattani Line (K-P) vegetation transition, which cuts across the Thailand–Malaysia border (see comments on the following species account). Hylomys maxi seems more abundant in hill and montane forests and was not recorded in dipterocarp forest in surveys on Northern Sumatra and Peninsular Malaysia ( Langham 1983, Boubli et al. 2004). This species has been collected in ‘jungle filled hollow surrounded by grasslands’ (Fred Ulmer field notes, ANSP archives) and in secondary vegetation on the edge of mountain forests, in highly anthropized areas (gardens, golf courses, etc.; authors’ unpublished data). Robinson and Kloss (1918) stated that the species was ‘quite numerous at dusk, running about in a patch of sweet potato ( Ipomoea batatas ) planted in a flat place among rocks at the edge of a torrent’. In Peninsular Malaysia it shares habitat with Crocidura fuliginosa , Crocidura cf. neglecta , Crocidura malayana , Suncus malayanus , Euroscaptor malayanus , Tupaia glis , Berylmys bowersi , Leopoldamys sabanus , Leopoldamys ciliatus , Maxomys surifer , Maxomys rajah , Maxomys whiteheadi , Maxomys inas, Niviventer cremoriventer , Niviventer cameroni, Sundamys muelleri , Sundamys annandalei , Rattus exulans , Callosciurus caniceps , Dremomys rufigenis , Lariscus insignis , and Sundasciurus tahan ( Robinson 1911, Harrison and Traub 1950, Rudd 1965, Langham 1983, Ruedi 1995, Omar et al. 2011, 2013, authors’ unpublished data). In Sumatra, H. maxi shares its habitat with Crocidura beccari , Crocidura lepidura , Crocidura aequicauda , Tupaia javanica , Tupaia ferruginea , Tupaia tana , Maxomys inflatus , Maxomys rajah , Maxomys surifer , Mus caroli, Niviventer fraternus , Lariscus niobe , and Sundasciurus altitudinis ( Robinson and Kloss 1918, Miller 1942, Ruedi 1995, authors’ unpublished data).

Hylomys maxi is omnivorous. In Peninsular Malaysia stomach contents contained tapioca bait and several crickets (N = 1; Harrison 1961). In Sumatra, stomachs contained insects of various orders, principally small beetles (N = 2–3). In captivity they feed on fish, shrimp, insects (cockroaches, mealworms, grasshoppers), raw meat, and soft fruit, showing less interest in the latter ( Davis 1965, Medway 1969, Genoud and Ruedi 1996). In Selangor, a pregnant individual with two embryos was recorded in March and females with enlarged mammae were recorded from May to November ( Medway 1969; USNM specimens). Hylomys maxi is cathemeral and found alone or in small groups (2–3 individuals; Fred Ulmer field notes, Medway 1969). In West Malaysia, average densities in favourable habitats are estimated at 3–4 individuals/ha. Home ranges are c. 30–40 m in diameter ( Rudd 1980).

Conservation: Recorded in Taman Negara, Kerinci Seblat and Leuser national parks, Pulau Tioman Wildlife Reserve, and Ulu Gombak, Ulu Langat, and Temengor forest reserves. Temengor has been selectively logged since 2001 and captures of H. maxi have not changed between sites with and without logging residues ( Yamada et al. 2016). It is unclear how ongoing deforestation in Kerinci Seblat and Leuser National Parks (see H. vorax and H. parvus accounts) is affecting H. maxi , nor the degree of deforestation in Malaysian protected areas. Hylomys maxi has been recorded in anthropized habitats such as gardens and sweet potato patches, but not in palm oil plantations. To assess the conservation status of H. maxi , further research is required to determine population trends within protected areas and to evaluate whether this species can adapt to palm oil plantations, considering much of the regional habitat is undergoing land-use change. Likewise, additional field campaigns combined with habitat suitability modelling seem pivotal to evaluate the species area of occupancy. Conservation planning must also acknowledge that H. maxi contains two divergent lineages that, pending additional research, may deserve species-level recognition (see below), and an altered conservation status. In the meantime, we suggest these two lineages are treated independently by regional government agencies and NGOs.

Comments: Sumatran populations seem to be smaller on average than Peninsular Malaysia populations and are somewhat differentiated in the craniodental PCA but do overlap, although this could be due to ontogenetical sampling biases. Sumatran populations also differ from Peninsular Malaysia populations with cytochrome b p -distances of c. 6% and have a private allele for the BDNF fragment, but not for GHR. Further geographical and nuclear loci sampling, particularly across Sumatra (which is poorly represented in museums), will be required to assess whether Sumatran and Peninsular Malaysia’s populations represent two different species. Abd Wahab et al. (2022) retained Tioman Island populations as a subspecies of H. suillus (H. s. tionis), but our results suggest it is found within the diversity of H. maxi . We do not believe this population deserves subspecieslevel recognition given that this taxon was described based on pelage coloration, which we now know, after looking at a much larger series than Chasen (1940), that it is highly prone to ecophenotypic, ontogenetic, and seasonal variation.

Figures

Figure 5. Morphometric variation in Hylomys. A, first and second principal components from an analysis of 16 cranial dimensions, computed with Dataset 4 (with the exclusion of external measurements); B, second and third principal components of the same analysis.Asterisks denote undamaged holotype or neotype specimens that could be included in this analysis.

Figure 6. Bivariate plot of rostrum length (ROL) and rostrum breadth (ROB) measurements.