Monodelphis sanctaerosae, Voss & Pine & Solari, 2012

Voss, Robert S., Pine, Ronald H. & Solari, Sergio, 2012, A New Species of the Didelphid Marsupial Genus Monodelphis from Eastern Bolivia, American Museum Novitates 2012 (3740), pp. 1-16 : 3-9

Monodelphis sanctaerosae , new species

HOLOTYPE: The holotype consists of the skin, skull, and postcranial skeleton of a young adult female ( AMNH 263548 , original number RHP 15068) collected on 29 June 1990 at Santa Rosa de la Roca (15°50′S, 61°27′W, 250 m above sea level) in the Bolivian department of Santa Cruz; a frozen tissue sample and a suspension of bone-marrow cells in Carnoy’s fixative (both with field preparation number NK 21048 ) are preserved in the Division of Genomic Resources at the Museum of Southwestern Biology. A partial (801 bp) cytochrome- b gene sequence from the holotype was deposited in GenBank with accession number HM 998596 by Solari (2010).

DISTRIBUTION: Known only from the type locality.

DESCRIPTION: Dorsal pelage uniformly grizzled brownish gray (near Buffy Brown) from crown to rump, indistinctly paler along the flanks than middorsally, but without distinct stripes or other sharp pigment discontinuities ( fig. 1 ). Fur on sides of head and surrounding ear pale reddish (near Cinnamon-Buff). Pinnae macroscopically naked, with pigmented skin (probably brownish gray in life). Ventral fur grayish basally but heavily washed with pale beige (near Light Buff). Hands and feet covered dorsally with short pale hairs, without any darker markings. Manual plantar epithelium unpigmented (probably pinkish in life); pedal plantar epithelium lightly pigmented (probably pale gray in life). Mammary formula unknown (teats are not visible in the single examined female specimen). Tail furred for about 10 mm at base (to about the same extent dorsally as ventrally), the unfurred remainder distinctly bicolored (dark dorsally and abruptly paler ventrally).

Skull unremarkable in general aspect, neither unusually long and narrow nor remarkably short and broad in dorsal view ( fig. 2 ) and not conspicuously flattened in lateral profile (fig. 3). Lacrimal foramina laterally exposed anterior to orbit; infraorbital foramen dorsal to P3; sagittal crest present but inconspicuous, extending from occiput to fronto-parietal sutures. Maxillopalatine fenestrae long, extending from level of P3/M1 commissure to level of M3 protocone on each side; palatine fenestrae absent; posterolateral palatal foramina very long, extending anteriorly beyond M4 protocones ( fig. 4 ). Alisphenoid tympanic process small and uninflated (not extending posteriorly to the level of the basioccipital/basisphenoid suture, leaving the hypotympanic sinus roof exposed in ventral view); secondary foramen ovale absent;

rostral tympanic process of petrosal narrow and acutely pointed, widely separated from caudal tympanic process (fenestra cochleae laterally exposed); stapes perforate and subtriangular (bicrurate, with a large foramen). Crowns of I2, I3, I4, and I5 increasing in width from front to back (such that I2 is visibly smaller than I5); upper and lower canines simple, without accessory cusps; p2 slightly taller than p3 (contra Voss and Jansa, 2009: 107). COMPARISONS: Members of the Monodelphis brevicaudata species group (sensu Solari, 2010)—including M. brevicaudata , M. domestica , M. glirina , M. maraxina , M. palliolata , and M. sanctaerosae —differ from other congeneric species by (1) lacking distinct longitudinal stripes in the dorsal pelage (versus stripes present, e.g., as in M. iheringi ); (2) having the infraorbital foramen positioned dorsal to P3 or to the P3/M1 commissure (versus dorsal to M1, e.g., as in M. scalops ); (3) by having long maxillopalatine fenestrae (versus short fenestrae, e.g., as in M. dimidiata ); (4) by having small alisphenoid bullae

FIGURE 3. Lateral cranial views of female Monodelthat do not extend posteriorly behind the phis sanctaerosae (A, AMNH 263548), M. domestica basisphenoid-basioccipital suture (versus (B, AMNH 261243), and M. glirina (C, AMNH larger bullae that extend well behind the 262398). All views about ×2. suture, e.g., as in M. emiliae ), (5) by lacking a secondary foramen ovale (versus secondary foramen ovale present, e.g., as in M. americana ), (6) by having a triangular or subtriangular stapes with a large obturator foramen (versus stapes columelliform and imperforate or microperforate, e.g., as in M. adusta ), and (7) by having the crowns of I2–5 increasing in width from front to back, such that the crown of I5 is visibly much broader than the crown of I2 (versus I2–5 crowns subequal in width, e.g., as in M. kunsi ). Monodelphis sanctaerosae differs from all other members of the Monodelphis brevicaudata species group by its small size (e.g., LM <7 mm; table 1) and long posterolateral palatal foramina. The latter perforations, which occupy the maxillary-palatine sutures, extend anteriorly beyond the protocone of M4 on each side ( fig. 4 ). This trait appears to be unique in the genus, resembling the condition otherwise seen among didelphids only in Thylamys and Lestodelphys ( Voss and Jansa, 2009: fig. 14).

Closer comparisons are warranted with two members of the Monodelphis brevicaudata group that also occur in Bolivia, and which appear to be closely related to M. sanctaerosae based on phylogenetic analyses of cytochrome- b sequence data ( Solari, 2010). As previously noted by Anderson (1997), Monodelphis sanctaerosae (“ Monodelphis sp. A ”) externally resembles M. domestica , both species having uniformly grizzled-grayish dorsal pelage. In side-by-side comparisons, however, the overall color of the dorsal pelage of M. sanctaerosae is distinctly browner (close to Ridgway’s Buffy Brown) whereas that of M. domestica is yellower in tone (closer to Citrine Drab or Deep Olive). Additionally, the fur of the cheeks and that surrounding the base of the ear is pale reddish in M. sanctaerosae , whereas the facial fur of M. domestica is grizzled grayish like the rest of the head, nape, and back. The holotype of M. sanctaerosae is smaller than any adult Bolivian M. domestica that we measured in head-and-body length and length of the hind foot ( table 1), but immature M. domestica probably have external measurements that overlap with those of adult M. sanctaerosae . Therefore, given the rather subtle pigmental differences between these species and the absence of other qualitative external differences, field identifications of small domestica -like animals are potentially problematic. Fortunately, our examination of a syntype of domestica (BMNH 87.10.25.1, an adult female collected by Johann Natterer at Cuiabá, Mato Grosso, Brazil) unequivocally associates this name with the larger of these two superficially similar species.

M. sanctae- M. glirina rosae M. domestica

AMNH UMMZ AMNH MSB UMMZ AMNH Femalesa Malesb 262398 ♀ 126683 ♀ 262399 ♂ 57005 ♂ 126682 ♂ 263548 ♀ c HBL 138 ± 19 148 ± 12 148 130 156 162 138 108 (115–176) 11 (130–171) 13

LT 75 ± 9 81 ± 6 73 83 88 87 78 60 (60–88) 11 (72–96) 13

HF 20 ± 1 21 ± 2 19 20 18 21 18 15 (18–21) 11 (18–25) 13

Ear 21 ± 2 23 ± 2 20 23 20 21 21 19 (19–25) 11 (20–28) 14

CBL 35.7 ± 2.4 38.8 ± 2.1 37.0 35.7 40.2 40.8 36.1 29.7 (33.2–40.6) 11 (35.9–42.7) 13

NL 16.5 ± 1.2 18.4 ± 1.0 18.0 16.5 19.8 20.6 16.8 13.7 (15.5–18.9) 11 (16.4–20.3) 12

NB 5.0 ± 0.4 5.4 ± 0.5 5.6 5.4 6.4 6.3 5.1 4.1 (4.3–5.8) 11 (4.7–6.4) 14

“LIB” 6.0 ± 0.2 6.0 ± 0.2 5.7 5.8 6.1 5.9 5.9 5.2 (5.8–6.3) 10 (5.6–6.5) 14

ZB 19.6 ± 1.4 21.0 ± 1.6 20.4 18.9 21.9 22.4 19.1 16.2 (18.2–22.1) 10 (18.9–23.6) 14

PL 20.3 ± 1.3 21.6 ± 1.1 21.0 19.7 22.0 22.3 20.2 16.2 (19.1–22.8) 10 (19.9–23.6) 14

PB 12.3 ± 0.6 12.9 ± 0.6 12.8 11.7 13.2 12.9 12.0 10.0 (11.6–13.7) 10 (12.1–14.3) 14

MTR 15.1 ± 0.7 15.8 ± 0.6 15.5 15.0 16.0 15.5 15.2 12.6 (14.0–16.2) 11 (14.9–16.9) 14

LM 8.0 ± 0.3 8.1 ± 0.1 8.2 8.0 8.1 8.2 8.1 6.8 (7.4–8.2) 11 (7.9–8.3) 14

M1–3 6.8 ± 0.2 6.9 ± 0.1 7.0 6.7 6.9 7.0 7.0 5.7 (6.6–7.1) 10 (6.6–7.1) 14

WM3 2.8 ± 0.1 2.9 ± 0.1 3.0 2.7 2.8 2.8 2.9 2.4 (2.5–2.9) 11 (2.7–3.0) 14

Weight 50 ± 14 70 ± 22 55 49 83 89 53 23 (33–73) 9 (44–110) 12

a The mean plus or minus one standard deviation, the observed range (in parentheses), and the sample size for measurements of the following series: AMNH 261232, 261234, 261235, 261240, 261243, 263547; MSB 55849, 55852; USNM 390566, 460728, 461347.

b The mean plus or minus one standard deviation, the observed range (in parentheses), and the sample size for measurements of the following series: AMNH 260024, 261231, 261233, 261236, 261241; FMNH 44857; MSB 55072, 55847, 55850, 55853, 63278, 67022, 67023; USNM 390567.

c Holotype.

Although Monodelphis sanctaerosae (“ Monodelphis species B ”) and M. glirina were recovered as sister taxa in Solari’s (2010) analysis of cytochrome- b sequence data, these species are externally dissimilar. Monodelphis glirina is larger in all external dimensions ( table 1), and it is an altogether gaudier species, with sharply contrasting pelage colors. Like some geographic forms of the Guianan species M. brevidaudata (see Voss et al., 2001: fig. 31), M. glirina is grizzled grayish middorsally from the crown of the head to the rump, whereas the sides of the head, legs, flanks, hips and tail base are clear reddish (near Orange Rufous); ventrally, the reddish color of the flanks grades imperceptibly to gray-based yellowish (near Pale Yellow-Orange). Because this distinctive color pattern is present even in immature specimens of M. glirina , confusion with M. sanctaerosae seems unlikely.

OTHER SPECIMENS EXAMINED: Monodelphis domestica : Bolivia — Beni, La Granja (USNM 461347), San Joaquín (FMNH 114651; USNM 364714, 364715, 460728–460731); Chuquisaca, 4.6 km E by road Carandaytí (AMNH 261234), Porvenir (AMNH 261231–261235, 261236, 261240–261243; MSB 55847, 55849, 55850, 55852, 55853), Río Limón (AMNH 263547, MSB 63278); Santa Cruz, Basilio (USNM 390568), 3.4 km S Basilio (USNM 390566, 390567), Montegrande (FMNH 44857), Río Quiser (FMNH 44856), San Ignacio de Velazco (USNM 390015), 27 km S Santa Cruz (MSB 67022, 67023), 4 km N [&] 1 km W Santiago de Chiquitos (MSB 55072), Tihumayu (USNM 290898), Tita (AMNH 260024); Tarija, Estancia Bolívar (AMNH 278252, 278253).

Monodelphis glirina : Bolivia — La Paz, 4 km by road NW Alcoche (UMMZ 126682, 127783), Guanay (AMNH 72570), 5 km SE Guanay (UMMZ 126684, 126685); Pando, Independencia (AMNH 262397), Santa Rosa (AMNH 262398, 262399; MSB 57005).

Figures

FIGURE 1. Dorsal, ventral, and lateral views of the holotype skin of Monodelphis sanctaerosae (AMNH 263548). All views about ×0.9.

FIGURE 2. Dorsal and ventral cranial views of female Monodelphis sanctaerosae (A, B; AMNH 263548), M. domestica (C, D; AMNH 261243), and M. glirina (E, F; AMNH 262398). All views about ×2.

FIGURE 4. Ventral view of posterior palate in Monodelphis sanctaerosae (A, AMNH 263548), M. domestica (B, MSB 63278), and M. glirina (C, AMNH 262398) illustrating the position of the posterolateral palatal foramen (plpf) in relation to the fourth molar (M4).