Echiothrix, GRAY, 1867

Musser, Guy G. & Durden, Lance A., 2014, Morphological And Geographic Definitions Of The Sulawesian Shrew Rats Echiothrix Leucura And E. Centrosa (Muridae, Murinae), And Description Of A New Species Of Sucking Louse (Phthiraptera: Anoplura), Bulletin of the American Museum of Natural History 2014 (391), pp. 1-87 : 14-17

ECHIOTHRIX GRAY, 1867

Echinothrix Alston, 1876: 83 .

Craurothrix Thomas, 1896a: 246 .

Gray (1867: 599) based his diagnostic description of Echiothrix (which he did not formally label as a diagnosis) on an intact skin and partial skull of an adult in which the molars are worn to the degree that their occlusal surfaces are basined instead of cuspidate ( fig. 3 ):

Head elongate. Nose elongate, compressed, concave on the sides; apex produced, acute; underside with short close bristles and a small central groove; nostrils apical, lateral. Fur soft, crisp, with abundance of bristles, flat and channeled at the base cylindrical and tapering at the tip; those of the under part of the body being white and more slender. Ears nakedish. Feet covered with short adpressed hairs. Tail elongate, cylindrical, nearly bald, with rings of square scales. Skull elongate; face very much produced, elongate, compressed; palate rounded in front, flat behind, with an elongated aperture in the middle of its length, more than twice as long as broad; the hinder part of palate with three equally long longitudinal grooves; nose flat above; nasal bones very long, slender. Cutting-teeth white; upper short, with two wellmarked subcentral longitudinal grooves; lower elongated, arched, rather compressed, rounded and smooth in front. Grinders [molars]… moderate-sized; the front much the largest; the hinder smallest and subcircular; the front upper rounded on the inner, and with two folds on the outer side; the second upper with one fold on the outer side, the lower front with a slight subcentral fold on the inner side. Crowns of the teeth flat; the front upper with two and the others with a single cross ridge, less distinctly marked in the hinder teeth. Hab. Australia. The skull is very much longer and more slender than in any species of Mus or of Muridae in the Museum Collection. The face is very slender, compressed, flat on the sides and above. The fissure on the side of the nose from the base of the infraorbital foramen is short and small, compared with those in the typical Muridae . The grinders [molars] are nearly erect; the crowns of the grinders are worn and concave between the ridges of the enamel.

Two other names have been proposed to replace Gray’s appellation. ‘‘The following attempt at a natural arrangement of the gnawing mammals is the result of a revision of the genera of that order,’’ wrote Alston in his ‘‘On the Classification of the Order Glires’’ published in 1876. There Alston provided a short diagnosis and emended Echiothrix to ‘‘ Echinothrix ’’ without explanation for doing so. Echiothrix is derived from the Greek echinos, referring to ‘‘hedgehog,’’ and trichos, meaning ‘‘hair,’’ and by combining the Greek words, Gray likely meant to highlight the shrew rat’s crisp, prickly coat—hair like that of a hedgehog.

Twenty years later, in a report ‘‘On Mammals from Celebes, Borneo, and Philippines recently received at the British Museum,’’ Thomas (1896a: 246) proposed Craurothrix (the Greek krauros means ‘‘brittle’’) to replace Alston’s Echinothrix , and Gray’s Echiothrix , because ‘‘ Echinothrix ’’ had already been proposed in 1853 for a group of sea urchins (the Greek echinos also means ‘‘sea urchin’’). Thomas (1896b: 1018) listed Craurothrix as the valid name in his ‘‘On the Genera of Rodents: an Attempt to bring up to Date the current Arrangement of the Order.’’ But in the next two years, Thomas (1898: 397) reverted to Echiothrix , explaining

As I have now joined those who think that names should be retained as originally spelt, whether classically right or wrong (except in the case of obvious misprints), I am now prepared to consider that Peters’s Echinothrix of 1853 does not preoccupy Gray’s Echiothrix of 1867, and therefore again recognize the latter term. Those who are not of this opinion must call it Craurothrix . That the missing out of the letter n is not a misprint is shown by Gray having written on the type skin what appears to be ‘ Echithrix,’ might be ‘ Echiothrix ,’ but is certainly not ‘ Echinothrix .’

Thomas’s acceptance of Echiothrix anticipated the rules that would come to govern original spellings of scientific names as promulgated in Article 32.2 and 32.3 of the International Code of Zoological Nomenclature (4th ed., 1999: 39): ‘‘The original spelling of a name is the ‘correct original spelling,’’’ and ‘‘The correct original spelling of a name is to be preserved unaltered ….’’ Gray’s (1867) Echiothrix is the valid generic name for the large-bodied Sulawesian shrew rat.

Gray’s (1867: 599) original characterization of Echiothrix ; Alston’s (1876: 83) brief diagnosis, which is simply a synopsis of Gray’s portrayal; and Ellerman’s (1941: 269) short account of characters in his ‘‘The Families and Genera of Living Rodents,’’ provided some diagnostic traits but lacked others so a generic emendation of those three author’s contributions is provided below.

TYPE SPECIES: Echiothrix leucura Gray, 1867: 600 (fixation by monotypy; see ICZN, 1999: 71, article 68.3) .

EMENDED DIAGNOSIS: A genus in Murinae within Muridae (as delimited by Musser and Carleton, 2005) that is distinguished from all other described murine genera by the following combination of traits: (1) species terrestrial in habitus; (2) dorsal pelage covering head and body dark gray or bluish gray, coarse and bristly, overhair coat composed mostly of wide flexible, and channeled spines intermixed with slender soft hairs; (3) ventral coat white (some individuals with russet stain), coarse but softer than dorsal pelage, demarcation between upperparts and underparts sharp and conspicuous; (4) muzzle elongate, mask encircling each eye, ears gray and large relative to body size; (5) tail typically longer than combined length of head and body (ranges of mean values for LT/ LHB are 103.8 % –116.0 % for E. leucura , and 112.8 % –126.0 % for E. centrosa ), tail scales moderately large (7–8 rows per cm), the rings of scales slightly overlapping, with one, two, or three hairs associated with each scale (tail appears scantily haired), basal onefourth to one-half dark gray to brownish gray on dorsal surface and sides, rest of tail white (ranges for dorsal white length–tail length is 47 % –67 % for E. leucura and 44 % – 73 % for E. centrosa ); (6) forearms short and slender, front feet moderately large but delicately built, claws sturdy but not elongate, digits white, dorsal surfaces of carpal regions white or speckled with patches of gray, three central digits of front foot longer than lateral digit, palmar surface adorned with three interdigital pads, a thenar, and a hypothenar; (7) hind foot elongate, digits white, dorsal surfaces of metacarpal regions white or speckled with patches of gray, three middle digits very long compared with much shorter lateral digits, plantar surface with full complement of plantar pads (four interdigitals, a thenar, and a hypothenar), but thenar and hypothenar very small relative to plantar surface; (8) two pairs of teats, both inguinal in position; (9) testes large relative to body size (16 % –23 %); (10) symphysis of mandible flexible, so tips of lower incisors can be spread apart up to 7 mm; (11) rostrum long and slender, interorbital and postorbital margins bounded by moderately high ridges, zygomatic arches moderately sturdy and flare from sides of skull, posterior zygomatic root situated low on braincase, braincase boxlike (wide and deep), occiput deep, no cranial flexion; (12) zygomatic plate moderately wide, its anterior margin projecting beyond dorsal maxillary root of zygomatic arch, its posterior edge even with the anterior margin of the first upper molar; (13) squamosal intact, not perforated by a subsquamosal foramen; (14) alisphenoid struts typically absent; (15) incisive foramina long and wide, set in middle of diastemal region; (16) molar rows parallel or bowed toward midline, bony palate long with its posterior margin projecting well beyond the molar rows to form a bony shelf, palatal surface with moderately deep palatine grooves, posterior palatine foramina at level of either second or third upper molars; (17) moderately long and wide sphenopalatine vacuities; (18) pterygoid plates appear absent but are reduced to slim and inconspicuous ridgelike vestiges, narrow platforms undefined by discrete margins, and apparently transformed into a vertical component in the outer wall of the mesopterygoid fossa in some specimens; (19) auditory bulla moderately large relative to skull size, the ectotympanic (bullar) capsule covering all but a narrow wedge of periotic, posterodorsal wall of carotid canal formed by bullar capsule; (20) large stapedial foramen, no sphenofrontal foramen or squamosal-alisphenoid groove, indicating a carotid arterial pattern widespread within Murinae (character state 2 of Carleton, 1980; pattern 2 described by Voss, 1988); (21) dentary elongate, long and narrow ramus (diastema) between incisor and molar row, very small coronoid process, large condyloid (articular) process, end of alveolar capsule forming large labial bulge just posterior to coronoid proces; (22) upper incisors typically white (dentine and enamel unpigmented), small and short relative to skull size, emerging from rostrum at a right angle (orthodont), each anterior face with two shallow grooves; (23) each lower incisor long and awl shaped with elongate wear facets, anterior faces smooth, dentine white and enamel either white or tinted pale yellow; (24) maxillary molars with three roots, mandibular molars with two; (25) molars brachydont, cusp rows forming cuspidate occlusal patterns that transform into basins with only moderate wear, third molar very small relative to others in toothrow; (26) no cusp t7 on upper molars, and no other occlusal embellishments (such as an enamel ridge projecting from anterolingual surface of cusp t8 anteriorly to posterior margin of lingual cusp t4, a labial enamel ridge connecting anterolabial margin of cusp t9 with posterolabial margin of cusp t6, or a comparable but shorter ridge projecting from the anterior surface of cusp t5 to meet the posterior margin of cusp t3 near the cingulum, all typical of some other murines with more complicated enamel occlusal patternsthe New Guinea Coccymys is an example [ Musser and Lunde, 2009]), posterior cingulum present in one species but absent in the other; (27) anteroconid formed of large anterolingual and anterolabial cusps, anterocentral cusp absent, anterolabial cusp present at low frequency or missing from second and third lower molars depending upon the species, anterior labial cusplets not present on any lower molars, but posterior labial cusplet present at a low frequency on most teeth, posterior cingulum present on first and second lower molars in one species, missing from those molars in another; (28) stomach unilocular-pouched, glandular epithelium confined to a pouch situated on the greater curvature within the lumen of the stomach; (29) sperm head long and sickle shaped, with single apical hook that lacks ventral processes, spermatozoal tail long; (30) karyotype, 2N 5 40, FNa 5 72 (total of autosomal arms) and FNt 5 75 (total number of arms, including XY), for E. centrosa .

CONTENTS: Two species are currently recognized, Echiothrix leucura and E. centrosa , both endemic to Sulawesi.

Between 1867 and 1920, Echiothrix was regarded as monotypic with E. leucura , the type species, occurring east of Gorontalo in the northeastern end of the northern peninsula ( Alston, 1876; Jentink, 1883; Thomas, 1896b; Trouessart, 1897; Meyer, 1899). In 1921, Miller and Hollister (1921: 67) described two additional species, both from the central part of Sulawesi. Echiothrix centrosa was based on samples from ‘‘the interior of Middle Celebes,’’ the Besoa region, Gimpu, Tuare, and Winatu. Echiothrix brevicula was applied to a sample from Pinedapa, ‘‘about 5 miles inland from the Gulf of Tomini, near Mapane, Middle Celebes.’’ Tate (1936), in his treatise covering some Indo-Australian Murinae , discussed E. leucura and referred to the two taxa described by Miller and Hollister as species. Subsequent rodent compendia and regional lists of species, however, demoted centrosa and brevicula to either subspecies of E. leucura ( Ellerman, 1941; Laurie and Hill, 1954) or synonyms ( Corbet and Hill, 1992; Musser and Carleton, 1993). By 2005, Musser and Carleton had recognized two species, E. leucura and E. centrosa , which are the two we define here. Geography, morphometric differences in cranial and dental variables, and different cusp patterns of maxillary and mandibular molars comprise the anatomical distinctions between the two species. The outlines of geographic range and phenetic interpretation of species diversity in Echiothrix sketched here is a hypothesis that should be tested by analyses of DNA sequences.

The first of the two accounts of species that follow consists of a description of Echiothrix leucura , the type species of the genus. Musser has not worked in the region where this species occurs and knows it only from his study of material held in museum collections. The geographic and morphological traits characteristics of E. leucura form the standard to which comparable characteristics of E. centrosa will be compared.

Musser did encounter E. centrosa in his fieldwork and the report on that species derives from material he collected (skins, skulls, rats preserved in fluid, and chromosomal preparations), descriptions of freshly trapped animals recorded in his field journals, and specimens obtained by other collectors now stored in collections of museums (skins and skulls). Information on spermatozoal and stomach morphologies, karyotype, and external characteristics of juveniles will be included—this kind of information is not available for E. leucura .

The accounts cover the following information: (1) description of the holotype and type locality; (2) emended diagnosis; (3) reference to the gazetteer where specimens are identified; (4) etymology of the scientific name (5) summary of geographic and elevational distributions; (6) description; (7) comparisons with other species; (8) geographic variation in phenetic characters; (9) allocation of a synonym (relevant to E. centrosa ).

Figures

Fig. 3. The holotype of Echiothrix leucura, a reproduction of the partial skull illustrated in Gray’s