Crocidura caudicrassa, Esselstyn & Achmadi & Handika & Swanson & Giarla & Rowe, 2021

Esselstyn, Jacob A., Achmadi, Anang S., Handika, Heru, Swanson, Mark T., Giarla, Thomas C. & Rowe, Kevin C., 2021, Fourteen New, Endemic Species Of Shrew (Genus Crocidura) From Sulawesi Reveal A Spectacular Island Radiation, Bulletin of the American Museum of Natural History 2021 (454), pp. 1-109 : 69-71

Crocidura caudicrassa , new species

LSID: urn:lsid:zoobank.org:act:8274BDB8-B7AF-46CC-A0A8-5EC15DC347D3

HOLOTYPE: MZB 34795 , an adult female collected on 28 October 2011 by K.C. Rowe and preserved as a cleaned skull ( fig. 34B ), fluid-preserved body ( fig. 33B ), and tissue sample ( NMV Z21760 ). External measurements are 144 mm × 62 mm × 17 mm × 10 mm = 16.5g.

TYPE LOCALITY: Indonesia, West Sulawesi Province, Kabupaten Mamasa, Desa Tondok Bakaru, Kampung Rantepangko , Mt. Gandang Dewata , Post 3 ; 2.84534° S, 119.38216° E, 2580– 2640 m elevation.

ETYMOLOGY: Caudicrassa is Latin for “thick tail,” identifying this species’ most distinctive trait.

GEOGRAPHIC DISTRIBUTION: Known only from the type locality around 2600 m on Mt. Gandang Dewata and from a single specimen collected by Luis Ruedas at 2120 m elevation from an area approximately 40 km ESE of Gandang Dewata in Rindingallo, of the west-central area of endemism ( fig. 1 ; table 3 ).

DIAGNOSIS: A large ( tables 2 , 12 ), stocky shrew ( fig. 17 ) with chocolate dorsal pelage (more reddish brown in MSB 93104 from Rindingallo), slightly grayer ventral pelage, and an unusually thick tail ( fig. 33B ). The dorsal hairs are dark gray at the base, with the overall pelage color determined by the browner approximately 1 mm tip. The tips of ventral hairs are a paler brown. The tail is shorter than head-and-body length ( fig. 9 ) and holds conspicuous bristles spread along nearly its entire length ( fig. 33B ). The bristles are pigmented proximally for roughly half their length in the series from Mt. Gandang Dewata, but only for approximately 1 mm on the specimen from Rindingallo (MSB 93104). The tail varies from pale brown to dark brown dorsally and is slightly paler on the ventral surface. The overall color of the tail is largely determined by the many applied hairs that cover the tail scales. The feet are similar in color to the tail, dorsally and ventrally and both the tail and feet are slightly paler than the dorsal pelage. The feet are small relative to body mass, but not body length ( fig. 17 ). The interdigital pads are exceptionally prominent, but the thenar and hypothenar are not unusual ( fig. 33B ). The pelage is unusually thick, with hairs at the middorsum approximately 8–10 mm long. The skull is large and robust, with a broad interorbital region ( figs. 10 , 34B ). The rostrum is long relative to skull length ( fig. 10 ; table 12 ). From a dorsal view, the braincase appears narrow, largely from the effect of the broad interorbital region. In dorsal view, the anteriorly converging lines formed by the sinus canal, interorbital margin, and rostrum above the maxillary process are quite straight. In ventral view, the rostrum is

narrow relative to the broad posterior palate. The molar row is robust ( fig. 34B ).

COMPARISONS: Crocidura caudicrassa is larger (as estimated from skull length) than most other species of shrew on Sulawesi. The exceptions are C. elongata and C. quasielongata of the Elongata Subgroup, C. nigripes of the Ordinary Group, and C. rhoditis of the Rhoditis Group. Among these relatively large animals, C. caudicrassa is much stockier than C. nigripes and all members of the Long-Tailed Group ( fig. 17 ; table 2 ). Only C. rhoditis has a body form nearly as robust, but it is substantially paler in pelage and skin color, particularly on the feet, and has a longer hind foot and thinner tail than C. caudicrassa ( fig. 9 ; table 2 ). Crocidura caudicrassa could be confused with C. nigripes , despite its stockier body. However, C. caudicrassa differs by having a wider interorbital region relative to both braincase breadth and skull length and a less robust dentition than C. nigripes . Crocidura caudicrassa could also be mistaken for C. brevicauda , the only other member of the Thick-Tailed Group, but the latter has a less stocky body form, less prominent interdigital pads, shorter skull length, narrower rostrum and interorbital region, lesser braincase height, and less elongate interorbital region ( table 12 ). The most distinctive feature of C. caudicrassa is its thick tail, which has no equal among Sulawesi’s Crocidura , but is approached by the somewhat thick tail of C. brevicauda ( fig. 33 ). The pelage of C. caudicrassa is thick—only those of C. brevicauda and C. musseri , the latter of which is much smaller and does not have a particularly thick tail, are comparable.

COMMENTS: We tested species limits between the two Thick-Tailed species using BPP on a small dataset containing 13 Crocidura caudicrassa and two C. brevicauda . Twelve of the C. caudicrassa specimens lack three of the five loci in this alignment, and thus it is only 54% complete. Nevertheless, BPP delimited these two species with posterior probability of 1.0 in all replicates.

The area around Mt. Gandang Dewata is an expansive region of montane habitat that is almost entirely unexplored by mammalogists.

Although we describe Crocidura caudicrassa as a montane endemic, it may have a somewhat larger geographic range in this area. The single specimen from Rindingallo (~ 40 km from Mt. Gandang Dewata) hints at this possibility.

We inferred a sister relationship between Crocidura caudicrassa and C. brevicauda in our analyses of UCEs ( figs. 7 , 8 ) and nuclear exons (supplementary data S6), but not in our analyses of mitochondrial DNA ( figs. 4 , 5 ). These two phenotypically similar species each appear to be montane endemics restricted to neighboring areas of high elevation, and thus we suspect that our UCE inferences reflect the correct relationship. Jukes-Cantor cytochrome b distances between these two species averaged 0.12, close to the mode of interspecific divergences among Sulawesi shrews and more than twice the median of intraspecific differences ( fig. 6 ; supplementary data S4). Their morphological differences and presumed isolation by lowland habitats between Mts. Gandang Dewata and Latimojong further support their distinction.

SPECIMENS EXAMINED: Mt Gandang Dewata ( MZB 34792–34798 , 34801–34805 ), Rindingallo, Tana Toraja ( MSB 93104 ).

Figures

FIG. 34. Images showing dorsal, ventral, and lateral views of the skull and lateral and occlusal views of the dentary of the two members of the Thick-Tailed Group: A, Crocidura brevicauda, MVZ 237632; and B, C. caudicrassa, MZB 34795.

FIG. 33. Images showing the ventral surface of the hind foot and dorsal surfaces of the tail base (approximately 1 cm from rump) and tail tip from the two members of the Thick-Tailed Group: A, Crocidura brevicauda, MVZ 237632 (left hind foot); and B, C. caudicrassa, MZB 34795 (right hind foot). In B the upper scale bar applies to the foot and the lower to the tail.

FIG. 1. Maps of A, Southeast Asia and B, Sulawesi showing topographical relief and the approximate boundaries (thick black lines) between areas of endemism (sensu Evans et al., 2003). Two-letter abbreviations in dark gray typeface identify the north-east (NE), north-central (NC), north-west (NW), west-central (WC), eastcentral (EC), south-west (SW), and south-east (SE) areas of endemism. Diamonds label localities where we, or others, have collected shrew specimens since 2010 with the mountain (or locality) name. Stars indicate type localities (Temboan and Pinedapa) from Miller and Hollister (1921). The type localities for the only two Crocidura described from the island since 1921 are Mt. Rorekatimbo (west-central area of endemism) for C. musseri Ruedi (1995) and Mt. Dako (north-west area of endemism) for C. caudipilosa Esselstyn et al. (2019).

FIG. 17. Box plots showing the length of the hind foot (HF) relative to the head-and-body length (HBL) and the ratio of mass to HBL. Plots show the median, 1st and 3rd quartiles, the maximum value within 1.5 × interquartile range (distance between 1st and 3rd quartiles; IQR), the minimum value within 1.5 × IQR, and outliers (black circles). Sample sizes are shown along the x-axis. Species are ordered along the x-axis according to the species groups used in the text (Thick = Thick-Tailed Group). Lengths are in mm and mass is in grams.

FIG. 9. Box plots showing variation in external measurements from all species of Sulawesi shrew. Plots show the median, 1st and 3rd quartiles, the maximum value within 1.5 × interquartile range (distance between 1st and 3rd quartiles; IQR), the minimum value within 1.5 × IQR, and outliers (black circles). Sample sizes are shown along the x-axis. Species are grouped according to the species groups used in the text (Thick = Thick- Tailed Group). All measurements in mm. HBL = head-and-body length.

FIG. 10. Box plots of relative skull measures showing braincase breadth (BB), interorbital width (IOW), and rostral length (RL) divided by condyloincisive length (CIL) and BB divided by IOW for all species of Sulawesi shrew. Plots show the median, 1st and 3rd quartiles, the maximum value within 1.5 × interquartile range (distance between 1st and 3rd quartiles; IQR), the minimum value within 1.5 × IQR, and outliers (black circles). Sample sizes are shown along the x-axis. Species are ordered according to the species groups used in the text (Thick = Thick-Tailed Group).

FIG. 7. Estimated species tree from analysis of 3940 ultraconserved element loci in ASTRAL. Samples from Sulawesi are labeled with the species name, locality, and catalog number. Asterisks indicate type specimens from Miller and Hollister (1921). Local posterior probabilities <0.95 are shown. Tip branch lengths are arbitrary.

FIG. 8. Estimated phylogenetic relationships from a maximum likelihood analysis of 983 concatenated ultraconserved elements. Samples from Sulawesi are labeled with the species name, locality, and catalog number. Asterisks indicate type specimens from Miller and Hollister (1921). Ultrafast bootstrap values <95 are shown.

FIG. 4. Maximum-likelihood estimate of the gene tree of Sulawesi Crocidura derived from an alignment of 851 individuals and 1111 characters from the mitochondrial gene cytochrome b. Bootstrap support is shown along branches. Clades corresponding to species are collapsed for ease of presentation. Tips are labeled with the species name, the number of tips (T), and number of localities (L), as labeled in figure 1, and the maximum intraspecific (MI) Jukes-Cantor distance calculated from a reduced alignment. Two species are paraphyletic and their respective, within-clade MI values are shown separately. For species described by Miller and Hollister (1921), the holotype or paratypes are included for C. elongata, C. lea, and C. rhoditis. Branch lengths between C. nigripes and other taxa are shortened for presentation. See supplementary data S2 for the full tree.

FIG. 5. Maximum likelihood estimate of the mitochondrial gene tree derived from an analysis of 14,007 characters (representing protein-coding and rRNA genes) from 83 samples. Bootstrap support values <95 are shown at nodes. Tips are labeled with the species, locality, and voucher number.

FIG. 6. Distribution of Jukes-Cantor distances from a character matrix with 812 samples, 312 nucleotides of cytochrome b, and no missing data. Character sampling, and to a lesser extent taxon sampling, was reduced to eliminate missing data.