Hylomys suillus Müller, 1841

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 : 26

Hylomys suillus Müller, 1841

Hylomys suillus Müller, 1841: 25 , 50. Original description.

Holotype: Not specified in original description.

Syntypes: RMNH39016 ( Jentink 1887: 243 a; Jentink 1888: 120 a), adult male, relaxed mount and cranium with damaged zygomata and occipital collected by S. Müller in May or July/ August 1834 in Batang Singgalang at c. 2000 ft (650 m), Sumatra, Indonesia. RMNH39017 , adult female relaxed mount with in situ skull collected by S. Müller on 23 September 1831 in Kaliki , Mt. Gede at c. 1200 ft (400 m), Java, Indonesia (Smeenk et al. unpublished work, P. Kamminga personal communication).

Lectotype: Sody (1933) assumed that the specimen illustrated by Schlegel and Müller (1843) was from Java, and proposed to restrict the type locality to Java, but did not designate a lectotype. We here designate as lectotype the syntype RMNH 39017 .

Type locality: ‘ Java en het andere van Sumatra’. Restricted by Sody (1933) to ‘Java’ Indonesia.

Paratypes: Non-existent.

Emended diagnosis: A medium sized Hylomys (average HB = 129.5 mm, GLS = 34.8 mm) with an average-sized, bicoloured tail (average T = 19 mm) and a venter coloration that transitions from brown-grey (between May and November) to dark grey (December to April). Skull is characterized by the following features: acute-angled notch between premaxilla tips; posterior end of nasals does not generally extend to the level of the antorbital rim; antorbital ridge absent/vestigial; lacrimal flange poorly developed; supraorbital processes generally absent, rarely developed; I1 procumbent; P4 has a generally straight, sometimes slightly sinuous, cingulum; P4 has a prominent and sharp parastyle; posterior nasal spine present but sometimes poorly developed; occipital crest absent or vestigial in females and absent to poorly developed in males.

Comparisons: Only Hylomys species present in Java. It has a shorter upper toothrow length than H. maxi ( IM 3Sa = 16–17.9 vs. 18.3–19.7 mm; Sody 1933), an acute vs. obtuse-angled notch between premaxilla tips in H. maxi , antorbital ridge, lacrimal flange and occipital crest absent/poorly developed vs. well developed in H. maxi , generally straight and thin vs. sinuous and thick P4 cingulum in H. maxi . It can be differentiated from H. vorax based on its bicoloured vs. monocoloured tail, shorter hindfoot ( HF + nail = 23–26 vs. 25.5–27.5 mm), and relatively broader rostrum ( Fig. 6 ). It has a larger braincase ( BB = 13.8– 15.6 vs. 13.1–14 mm, BD = 8.8.–9.8 vs. 8.6 mm, MAB = 13.2– 14.5 vs. 12.2 mm) and mandible length ( LMA = 22.4–26.8 vs. 20.1–22.2 mm) than H. parvus . See H. dorsalis species account for a comparison with this species.

Distribution, habitat, and natural history: Javan endemic distributed from sea level (recorded in Jakarta) to 2200 m a.s.l, although it has also been reported to be found exclusively in the montane forests of some isolated volcanoes ( Bartels 1937), perhaps because most lowland forests have been logged in Java. Collected in forest, edge of forest, and inside a house in Cibodas ( USNM specimens NAMRU). In Cibodas, West Java, it shares its habitat with Crocidura brunnea , C. monticola , C. orientalis , Maxomys bartelsi, Niviventer cremoriventer , Niviventer sp., Rattus argentiventer, Rattus exulans , Rattus tanezumi , and Melogale orientalis (Ruedi 1995, USNM catalogue).

Conservation: Recorded in Gunung Gede-Pangrango and Mount Halimun Salak National Parks and Kawah Ijen Nature Recreation Park. While H. suillus may not face habitat loss in protected areas of West Java (Higginbottom et al. 2019), it is important to note that most of these areas primarily consist of montane forests, which are susceptible to the impacts of climate change. Thus, further research is needed to determine population trends within protected areas. Likewise, the use of habitat suitability modelling is essential to re-assess the conservation status of H. suillus , given that, even though this species is found across most of Java, its distribution is very fragmented ( Ruedi et al. 1994). In essence, the species actual current and future area of occupancy may be much smaller than its overall extent of occurrence. The designation of Gunung Slamet and Gunung Lawu as national parks would greatly benefit this species. These mountains have the second and third largest elevational ranges on Java, and their long-term protection might aid this and other montane species in tracking climate change, but also contribute to east–west population connectivity if forest restoration efforts are promoted.

Comments: This species exhibits a high degree of morphological variation, spanning about twice the morphospace compared to its relatives in the craniodental PCA ( Fig. 5 ). This variation seems somewhat geographically structured (east and west Java), although there are several outliers that break this pattern. Future studies should examine species limits within H. suillus in the light of molecular evidence and additional geographical sampling.

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.