Hylomyscus thornesmithae, Kerbis Peterhans & Hutterer & Doty & Malekani & Moyer & Krásová & Bryja & Banasiak & Demos, 2020

Kerbis Peterhans, Julian C., Hutterer, Rainer, Doty, Jeffrey B., Malekani, Jean M., Moyer, David C., Krásová, Jarmila, Bryja, Josef, Banasiak, Rebecca A. & Demos, Terrence C., 2020, Four new species of the Hylomyscus anselli group (Mammalia: Rodentia: Muridae) from the Democratic Republic of Congo and Tanzania, Bonn zoological Bulletin 69 (1), pp. 55-83 : 65-69

publication ID	https://doi.org/10.20363/BZB-2020.69.1.055
publication LSID	lsid:zoobank.org:pub:1FD4D09C-D160-4159-A50D-20B6FBC7D9E9
persistent identifier	https://treatment.plazi.org/id/C54F87EA-FFB1-FFD4-60B1-F98EFDCDF9B0
treatment provided by	Felipe
scientific name	Hylomyscus thornesmithae
status	sp. nov.

Treatment

Hylomyscus thornesmithae sp. nov. Kerbis Peterhans, Hutterer & Demos

urn:lsid:zoobank.org:act:DAE95BEF-D424-42C2-8415-A1805F494ADC Hylomyscus sp. – Doty et al. (2017)

Holotype. Field Museum of Natural History , Division of Mammals number FMNH 222524 About FMNH (field number WT Stanley 11,664; CDC 746 ), collected by W. T. Stanley, 27 June 2013 (originally listed as Hylomyscus sp. ). The type specimen, consisting of an alcoholic carcass with skull removed, is an adult female with first upper molar in ear- ly wear (advanced age stage IV) and large teats (2+4). The basisphenoid-occipital suture is fused. External measurements were made in the field: TL 210, TV 124 , HF 18, EL 15, Wt 15. Specimen caught in a standard snap trap; apparently held by tail in trap as tail is broken ⅓ way down. Type specimen captured just behind camp in secondary growth forest on the edge of a forest that may occasionally be subject to flooding.

Type locality. Democratic Republic of Congo, Tshuapa Province , rt side Tshuapa River , 14 km north of Boende by road, Quatorz (0.16919° S, 20.92611° E) at an elevation of 322 m. GoogleMaps

Paratypes (n = 4). All caught in conventional trap lines from Democratic Republic of Congo, Tshuapa Province , 4 km N of Boende, Baleko (0.24127° S, 20.8833° E) at an elevation of GoogleMaps 358 m: FMNH 219611 About FMNH ( WTS 11471 , CDC 103 ), alcoholic carcass with extracted skull, old scrotal male ; FMNH 219612 About FMNH ( WTS 11592 , CDC 224 ) alcoholic carcass with extracted skull, old female, teats 2+4 ; FMNH 2119613 About FMNH ( WTS 11594 , CDC 226 ), alcoholic carcass with extracted skull, old scrotal male ; FMNH 219689 About FMNH ( WTS 11481 , CDC 113 ), skin and skull with carcass preserved in alcohol, old scrotal male, testes 10x5 .

Diagnosis. Easily differentiated within the Hylomyscus anselli group by its small size (second smallest, but still much larger than preceding species): HB 83 (mean), Wt 13.9 (mean), ONL 22.8 (mean), CLM 3.2 (mean). All are significantly smaller than all other members of the H. anselli group ( Tables 4–5), excepting the previously described species.

Comparisons. Upper incisors orthodont, contrasting with the proodont condition in Hylomyscus pygmaeus . Crown length of upper molars 3.0– 3.25 mm, much larg- er than Hylomyscus pygmaeus (under 2.6 mm). External and cranio-dental measurements smaller than all other members of the H. anselli group (excepting Hylomyscus pygmaeus ).

Description. Size very small (mean HB = 83, mean mass = 13.9). Tail 46% longer than HB, unicolor with ca. 18 annulations per cm. Ears of normal size, 18% of HB; ear color dark grey. Belly hairs 5 mm, basal 3 mm slate grey, distal 2 mm white. Dorsal hairs 7 mm, basal 5 mm slate grey, apical 2 mm orange, more bright orange towards flanks. Vibrissae up to 33 mm in length, mostly black but with 2–3 white hairs; upper lip with white fur patch behind vibrissae. Teats 2+4. The hind foot possesses the standard murine complement of 6 pads (see Ibe et al. 2014: fig. 2, II for reference); there is a single accessory pad on the 1 st and 4 th interdigital pads; the first is clear and well-defined while the 4 th is larger and more integrat- 68 Julian C. Kerbis Peterhans et al.

ed ( Fig. 9a View Fig ). The number of fleshy palatal ridges are not visible on any of the prepared skulls.

Skull small (mean ONL = 22.8, mean CRM = 3.2). Rostrum short, LN/ONL = 33.7%. Upper incisors orthodont. Incisive foramina fall well short of upper tooth row. T3 on M 2 is tiny. Braincase elongated. Hamular process of the squamosal long and thin, providing for a large subsquamosal fenestra which is about 35% the size of the post glenoid foramen (see Carleton & Stanley 2005: fig 6; Fig 6f View Fig ). Maxillo-palatal suture zig-zags through the middle of the M 1 ( Figs 6d View Fig , 8b View Fig ). Post palatal foramina large, starting at rear 3 rd of M 1 or between M 1 and M 2 and continues through to the 1 st third of M 2. Zygomatic plate slightly sinuous. In aged individuals (FMNH 219611, FMNH 219612), the incisive foramina fall even shorter of the UTR, the maxillo-palatal suture is located more forward at the first half of M 1 and the post palatal foramina are more forward at the rear half of the M 1. Frontoparietal suture broadly rounded, U-shaped. Zygomatic plate narrow (1.9 mm) and virtually orthogonal to skull profile but gently sloping forward in lower third. Mesopterygoid fossa rounded at rostral end.

As a member of the Hylomyscus anselli group (sensu Carleton et al. 2006: table 7), the following characters are relevant: 1) mammae: 2+4, 2) upper incisors orthodont ( Fig. 6f View Fig ), 3) T3 on M 1 is ‘medium’ in size (smaller than t1), the anterior chevron is moderately asymmetrical

( Fig. 7f View Fig ), 4) T9 on M 1 is distinct but reduced ( Fig. 7f View Fig ), 5) interorbital constriction is amphoral in shape ( Fig. 6b View Fig ). 6) rostral length is short, LN/ONL = 33.7% ( Fig. 6b View Fig ), 7) incisive foramen is very short, falling short of the roots of M1 ( Figs 6d View Fig , 8b View Fig ), 8) the hamular strap is short but thin and delicate and allows for a large subsquamosal foramen, which is about 25% the size of the postglenoid foramen ( Fig. 6f View Fig ).

Distribution. Known only from two locations, both are ca. 250 km S of the Congo River, off the right bank of the Tshuapa River, Tshuapa Province, Democratic Republic of Congo. In addition to the type locality (n = 1), four paratypes are from 4 km N of Boende at Baleko (0.24127° S, 20.8833° E, elevation 358 m).

Ecology. Type specimen and 3 paratypes all caught in standard mammal snap traps while the fifth was caught in a Sherman live trap. Type specimen captured in regenerating secondary forest on the edge of a seasonally flooded forest. One specimen captured in a trap line that was never flooded during heavy rain events while three came from a trap line that was prone to flooding.

Reproduction. All animals captured (n = 5) were adult. Type is adult female with swollen teats 2 + 4. A second female ( FMNH 219612 About FMNH ), despite having well-worn molars (beyond stage VII), had small teats that are difficult to decipher. Three adult males all with scrotal testes; testes of FMNH 219689 About FMNH measured 10 × 5 in the field .

Etymology. Ellen Thorne Smith was a “professional volunteer” serving 2–3 days per week, sorting and organizing the bird collections at the Field Museum, and conducting original published research from the mid 1930’s until the 1970’s. During World War II with the museum’s ornithologists away in Washington, she ran the Division of Ornithology. We recommend “Mother Ellen’s wood mouse” as an English common name.