Eliurus danieli, Carleton & Goodman, 2007

Carleton, Michael D. & Goodman, Steven M., 2007, A New Species of the Eliurus majori Complex (Rodentia: Muroidea: Nesomyidae) from South-central Madagascar, with Remarks on Emergent Species Groupings in the Genus Eliurus, American Museum Novitates 3547 (1), pp. 1-24 : 3-13

Eliurus danieli , new species figures 1–3; table 1

HOLOTYPE: Field Museum of Natural History number 175934, an adult male prepared as skin, skull, and partial skeleton, collected 10 December 2002 by Steven M. Goodman (original number SMG 13,425 ).

The round skin and skull are in fine condition. External data recorded on the skin tag include: TOTL, 335 mm; HBL, 150 mm; TL, 179 mm; HFL, 30 mm; EL, 26 mm; and WT, 91 gm. The animal was noted as having scrotal testes (12 X 5 mm) with convoluted epididymides; tissues were preserved in EDTA (ethylene diamine tetraacetic acid).

TYPE LOCALITY: Madagascar, Fianarantsoa Province, Parc National de l’Isalo, 28 km SE Berenty-Betsileo, along Sahanafa River near foot of Bevato Mountain , 650 m; geographic coordinates: 22 ° 19.0 9 S, 45 ° 17.6 9 E .

DIAGNOSIS: A species of Eliurus characterized in combination by a gray dorsal pelage, contrasting grayish-white venter, and a distinctive bright-white tail tuft (fig. 1). Cranial size moderately large (ONL ca. 37–41 mm; figs. 2, 3), molar rows absolutely and relatively long (LM1–3 ca. 6.0– 6.5 mm), incisive foramina relatively long and wide (LIF/LD ca. 56%), and ectotympanic bullae large for the genus. Alveolus of lower incisor short, not forming a capsular process.

REFERRED SPECIMENS: Three additional specimens are known, all from the PN de l’Isalo: FMNH 175933 , a young adult male also collected by Goodman ( SMG 13,387 ) in the same month (5 Dec ) from 24 km W Ranohira bas, Andranohavo (Canyon des Rats), 700 m, 22 ° 28.9 9 S, 45 ° 22.9 9 E; UADBA 10483 , a young adult female obtained 2 April 1995, A. F. A. Hawkins ( FH 3 ), from a site within 300 m of where the holotype was obtained (Georges Rabeony, personal commun.); and UADBA 46805 obtained between 2 and 9 February 1995 ( Hawkins, 1995), by A. F. A. Hawkins ( FH 23 ) in the Canyon des Rats .

DISTRIBUTION: To date known only from the PN de l’Isalo, south-central Madagascar.

DESCRIPTION: Fur texture soft and fine. Cover hairs 9–10 mm in length over middle rump. Basal four-fifths of dorsal cover hairs bright plumbeous gray, distal one-fifth medium buff, some hairs tipped with a third band of faint dusky brown. Guard hairs dark brown to blackish, only slightly longer than the cover hairs except over the rump. General effect of upperparts a pale brownish gray; forehead, face, and lower legs a purer medium gray. Boundary of dorsal and ventral pelage clearly demarcated along sides. Ventrum variable in coverage of white hairs: entirely bright buff white (UADBA 10483); or dull buff white over the chin, throat, and chest with some basal gray thinly showing over the lower abdomen and inguinum (FMNH 175934); or wholly white hairs confined to the chin and throat, cover hairs over the chest and abdomen bicolored (basal half gray, distal half white), and the underparts overall light grayish white (FMNH 175933). Medial dusky brown band extends over the tarsus and proximal metatarsus; remainder of metatarsus and toes, as well as tops of forefeet, covered with bright white hairs; ungual tufts at base of claws well developed.

Caudal tuft prominent over distal half of tail length, tuft hairs becoming gradually longer toward the tip and measuring about 12–15 mm long over the terminal portion (fig. 1). Terminal one-third of tail length covered with pure white hairs, forming a brilliant white tuft accentuated by the intensely black hairs of the proximal tuft (distal white segment 5 35 mm in UADBA 10483, 45 mm in FMNH 175934, and 75 mm in FMNH 175933). Proximal half of tail clothed with short black hairs that do not mask the caudal scales; scalation moderately textured; epidermis pale gray to whitish toward the base of the tail, lighter underneath, but paleness visually obscured by the black hairs.

Hind feet short and broad. Six plantar pads arranged as characteristic of the genus; pads not so bulbous and crowded as in E. antsingy . Pinnae medium-sized, more rounded, not so elongate as E. tanala Major (1896) ; color pale dusky brown externally, somewhat lighter internally, and sparsely clothed with fine brown hairs inside and outside.

Cranium moderately large (ONL 5 37– 41 mm; figs. 2, 3), agreeing with largest geographic examples of E. majori (e.g., from PN de Marojejy), smaller than E. antsingy and large-bodied E. tanala (e.g., from RS d’Anjanaharibe-Sud). Dorsal profile of skull arched (fig. 3), sloping gradually toward the rostrum and more steeply toward the occiput, not so flat as in E. tanala of similar size. Rostrum proportionally long (LR/ONL 5 36.2%) for the genus, comparable to relative length in the E. tanala complex but longer than E. myoxinus or E. majori . Braincase rounded and smoothly contoured; subsquamosal fenestra patent and medium-sized, exposing the interior braincase and dorsal periotic; hamular process of the squamosal stout but well delineated. Zygomatic arches almost parallel-sided in the three specimens; zygomatic plate medium in width for the genus, forming a shallow but distinct dorsal notch, more incised than in E. penicillatus and E. majori . Incisive foramina bluntly pointed on their posterior ends, more acute at the anterior; wide and relatively long (LIF/LD 5 56%) for the genus, in proportion resembling E. antsingy and the E. majori complex (fig. 2). Posterior palatine foramina oval, situated within the maxillary-palatine suture at the level of the M1-M2; supernumerary palatal foramina occurring in the palatine bones, but minute in size and irregularly formed; slitlike palatal vacuities absent. Posterior margin of the bony palate terminates just short of the ends of the third molars; anterior expanse of mesopterygoid fossa broad and horseshoeshaped, its sides gently incurved. Alisphenoid strut present on both sides in all three individuals examined. Auditory bullae relatively large for the genus, the ectotympanic covering nearly all of the periotic in ventral view, even more so than in E. antsingy and E. myoxinus . Mandible stocky in form, ascending ramus deep.

Enamel face of upper and lower incisors dull yellowish-orange in color. Alveolus of lower incisor relatively short, terminating posteriorly at the level of the coronoid process and well below the sigmoid notch; tip of incisor root indicated by slight mound on mandibular ramus but not forming a projecting capsular process. Toothrows long (LM1-3 5 6.0– 6.5 mm) relative to cranial size, in proportion like those of E. majori and E. penicillatus ; molars robust with laminate occlusal configuration as per the genus, higher crowned than most Eliurus but again approximating E. majori and E. penicillatus in this detail; upper and lower third molars about equal in length to second molars or only slightly shorter.

Other external, cranial, and dental features as described for the genus ( Carleton, 1994; Carleton and Goodman, 1998).

MORPHOLOGICAL AND MORPHOMETRIC COM- PARISONS: The cardinal traits of E. danieli implicate the eastern species E. majori and E. penicillatus or western E. antsingy as its closest relatives. All four are relatively large species of Eliurus and possess long incisive foramina that span over half the diastema (fig. 2) and short lower incisors that lack a prominent capsular process. In combination, these qualitative features serve to distinguish the four from all other species of Eliurus (see Carleton, 1994, Carleton and Goodman, 1998, and Carleton et al., 2001, for discussion of interspecific variation in these characters).

Other character differences associate E. danieli more closely to E. majori and E. penicillatus instead of E. antsingy . Foremost, specimens of E. danieli have long, robust molar rows in proportion to cranial size (LM1-3 ca. 16–17% of ONL), a configuration that agrees with E. majori and E. penicillatus ( Carleton, 1994) . In contrast, examples of E. antsingy have shorter toothrows in relation to cranial size (LM1-3 ca. 13–14% of ONL), resembling in this regard all other species of Eliurus ( Carleton et al., 2001) . A simple bivariate plot underscores the segregation of the two groups by dental proportion (fig. 4); only one stray individual (an E. danieli ) overlaps the otherwise clearly delineated data-point constellations. The morphogenetic determination of these dental shape contrasts is such that molar variables (LM1-3, WM1) always contribute most heavily to group separation on the first factor extracted in all ordinations of our cranial measurements, whether principal component (not illustrated) or canonical variate (fig. 5, table 2). Eliurus danieli , together with E. majori and E. penicillatus , also differ from E. antsingy in fur texture (not so fine and soft), plantar pads (not as large, bulbous, and close-set), size of upper and lower third molars (not smaller than second molars), and molar hypsodonty (not as low-crowned). These impressionistic differences are not so easily quantifiable as is the disparity in toothrow proportions.

Eliurus danieli can be distinguished from E. majori and E. penicillatus by means of the following traits. Although similar in size to E. majori , specimens of E. danieli possess a conspicuous white caudal tuft. This trait is unknown in nearly all geographic samples of E. majori , in which the tuft is wholly dark brown or black to the tip ( Carleton, 1994; Goodman and Carleton, 1996). In the PN de Marojejy, however, Carleton and Goodman (2000) reported that nine of the 20 E. majori specimens collected possess a white caudal tip of variable extent. The white tail tip in those particular E. majori , however, is not accentuated by a contiguous band of dense black hairs as found in E. danieli . Furthermore, in other features and in morphometric analyses, the Marojejy sample unambiguously accords with typical E. majori ( Carleton and Goodman, 2000; also see next), not E. danieli . Although possessing a white caudal tuft as diagnostic of E. penicillatus , specimens of E. danieli are conspicuously larger in nearly all variables measured (figs. 2, 3; table 1); in view of that great size disparity, the two species are strongly circumscribed in morphometric space (fig. 5). Finally, in contrast to E. majori and E. penicillatus , E. danieli has gray dorsal pelage, bright in tone (in both eastern species, dorsum blackish gray to blackish brown and somber colored); its venter is bright buff white or grayish white and clearly delineated from the dorsum (in both eastern species, venter paler but similarly colored to the dorsum and dorsal-ventral pelage contrast less well marked); its ectotympanic bulla is absolutely larger (table 1), obscuring nearly all of the periotic in ventral view (in both eastern species, ectotympanic less inflated, exposing posteromedial wedge of the periotic); and its zygomatic plate projects forward to form a distinct dorsal notch (in both eastern species, zygomatic plate narrower and dorsal notch weakly incised).

In projections of the first three canonical variates (cumulative variation explained 5 85.5%) extracted from 13-group discriminant function analysis, the three specimens from PN de l’Isalo are wholly isolated in morphometric space from all other OTUs and species (fig. 5). As commented above, the two molar variables (LM1-3, WM1) most strongly influence separation of groups along the first canonical variate (table 2). Other dimensions that load moderately along this factor include those that reflect palatal breadth (BM1s, PPW) and interorbital width (IOB); compared with E. antsingy , the palate is relatively broader and interorbit narrower in E. danieli , E. majori , and E. penicillatus (table 1). Size as a general factor is expressed along the second canonical variate, as indicated by the positive and moderately strong correlations (Pearson’s R 5 0.6–0.8, P #.001) of most variables with this factor (table 2). In general size, specimens

TABLE 1 Selected External and Craniodental Measurements for the Type Series of E. danieli and Samples of E. majori , E. penicillatus , and E. antsingy (Sample statistics include the mean, ± 1 SD, and the observed range)

TABLE 2 Results of 13-group Discriminant Function Analysis (OTUs represented include four of E. antsingy , N 5 24; one of E. danieli , N 5 3; seven of E. majori , N 5 90; and one of E. penicillatus , N 5 13. See Materials and Methods and fig. 4)

of E. danieli match the larger samples of E. majori and E. antsingy and conspicuously exceed the diminutive E. penicillatus in most dimensions quantified (table 1). Betweengroup variation summarized by the third canonical variate conveys the morphometric association of E. danieli and E. penicillatus (fig. 5). The few cranial variables (BIF, LD, LBP, DAB, BZP) that account for this association constitute proportional subtleties that are not readily apparent in side-by-side skull comparisons of the two species due to their gross size disparity; notable among these are the relatively spacious incisive foramina

+ (BIF) and short diastema (LD). Although visually unimpressive, such proportional features nevertheless influence the phenetic pairing of the E. danieli and E. penicillatus samples among all OTUs represented, as indexed by Mahalanobis distances between group centroids (fig. 6). The multivariate level of divergence between the two (Mahalanobis D 2 5 52.3) surpasses that derived for the most strongly differentiated samples within either E. majori or E. antsingy .

ECOLOGICAL NOTES: The PN de l’Isalo is located on the Isalo Massif, a vast area of badlands composed of ruiniform Jurassic sandstone. Much of the park includes rocky habitat with sparse short scrub or completely lacking any plants. Many deep canyons found within this formation contain permanent rivers that are in part responsible for the steeply cut valley sides, and the precipitous facies have a unique rupicolous plant community. Gallery forest can be found along river margins at the base of these canyons and at their mouths. An evergreen sclerophyllous forest formation dominated by the genus Uapaca (Euphorbiaceae) covers more gently sloping hillsides. Although the region receives around 850 mm of rain per year and has a pronounced dry season ( Nicoll and Langrand, 1989), the water-fed canyons retain moist conditions and support vegetation whose floral affinity is transitional between humid and deciduous formations ( Gautier and Goodman, 2003). Within these moist canyons occur numerous animals that represent taxa or species groups otherwise known from the eastern humid forests.

Microhabitats where specimens of E. danieli were captured are noted on skin tags or in original specimen catalogs as follows: ‘‘On rocky cliff about one-half way up Bevato Mt. in zone with little woody vegetation. Trapped on ground in small hole leading into rock fall’’ (FMNH 175934, holotype); ‘‘on the rocky mountain of Sahanafa’’ [translated from the individual scores onto the first and third canonical variates extracted. The maximally inclusive polygons enclose specimen scores around an OTU’s centroid; in view of extensive overlap and visual confusion, the sample polygons for E. antsingy (4 OTUs) and E. majori (7 OTUs) were collapsed to enclose maximal dispersion around the species’ grand centroid. See table 2 for variable correlations and percent variance explained.

French] (UADBA 10483); ‘‘In canyon with vegetation at base of rock face and along river banks—sandy soil. Trap on ground under opening of large boulder at river edge and surrounded by ferns and dense rupicolous vegetation’’ (FMNH 175933); and ‘‘in the interior of the Canyon des Rats, a site of exposed rock and at a level more than 30 m above the water [5 river] level’’ [translated from the French] (UADBA 46805). This information suggests that the species is at least in part terrestrial and lives outside forest formations.

On the basis of considerable field experience with members of Eliurus, Goodman has never captured an individual in an ecological setting similar to that of the E. danieli holotype. The site at the foot of Mt. Bevato is a broad expanse of exposed pseudosteppe, on a steep rocky slope, and approximately 500 m from the nearest forest. According to M. George Rabeony, an employee of the park service who has accompanied numerous researchers in the PN de l’Isalo, this is also the locale where UADBA 10483 was trapped in April 1995. In late December 2002, Goodman returned to this site and placed thirty traps (10 Nationals and 20 Shermans) on the ground under large rock outcrops between the forest edge and the middle portion of Mt. Bevato. The individual (FMNH 175934) was captured in one of the highest-elevation traps set along the Bevato cliff face. Other mammals captured in this trap line include the introduced Rattus rattus and the large tenrecid Tenrec ecaudatus . A few individuals of E. myoxinus were trapped within the Sahanafa Forest, about 1.5 km from where the holotype of E. danieli was obtained. In the Andranohavo Forest (Canyon des Rats), E. myoxinus and R. rattus were common and captured within a short distance of E. danieli .

TAXONOMIC AND BIOGEOGRAPHIC REMA- RKS: The phenetic union of E. danieli and E. penicillatus and their joint possession of a white tail tuft, largely to the exclusion of E. majori , offer a provisional hypothesis of sistergroup relationship. Nonetheless, we are not persuaded that this cognate relationship will be necessarily sustained by other data sources, such as gene-sequence studies. First, with only four specimens at hand, the sample size of E. danieli is too small to adequately represent variational bounds in the species population. Second, as enumerated above, E. majori and E. penicillatus do share a number of morphological similarities not found in E. danieli . In view of their distribution in eastern humid forest, the possibility that E. majori and E. penicillatus form a clade vicariantly related to E. danieli in west-central Madagascar remains as viable an interpretation (and see below).

Compared with other Eliurus that have a white caudal tuft ( E. grandidieri , E. penicillatus , E. tanala ), that possessed by E. danieli is the most visually striking. As we currently understand interspecific affinities (see Discussion) and assuming that an all-dark tuft represents the primitive state, a terminal white tuft has evolved at least three times within the genus. The significance of these contradistinctive caudal flags to social behavior of the species or in interspecific encounters deserves investigation.

Although the Isalo Massif today receives only moderate amounts of rainfall per year and experiences a pronounced dry season, organisms identified from regional paleontological sites supply ample biotic evidence that local climatic conditions were distinctly more mesic during the Late Pleistocene and Holocene ( Burney, 1997; Goodman and Rakotozafy, 1997; Godfrey et al., 1999). Relicts from this more mesic phase of late Quaternary climate persist in the modern flora of the Isalo area, most notably in the deep canyons where many plants show phytogeographic affinities to the eastern humid forests. The same relictual biogeographic pattern has also emerged from the study of certain birds, reptiles, and amphibians that inhabit the Isalo Massif (e.g., Raxworthy and Nussbaum, 1996, 1997; Fjeldsa et al., 2000). Two kinds of taxonomic evidence have been identified among those vertebrate groups: (1) the same species is found in common between Isalo and sites in the eastern humid forests; or (2) closely related taxa occur in these two areas and are presumed to have originated through east-west vicariance. The presence of E. danieli in the Isalo region and its proposed sister-group relationship to E. majori and/or E. penicillatus exemplify the second line of evidence for a former east-west continuity of humid forest.

ETYMOLOGY: We name this new species to honor Professor Daniel Rakotondravony, Département de Biologie Animale, Université d’Antananarivo, especially for his contributions to our knowledge on Malagasy rodents and for helping to foster zoological research on Madagascar for numerous national and foreign scientists.