A new species of the rodent genus Oecomys (Cricetidae, Sigmodontinae, Oryzomyini) from eastern Bolivia, with emended definitions of O. concolor (Wagner) and O. mamorae (Thomas)

2009·1.9 MB·English

by  Carleton, Michael D

A tamerican museum
Novitates
PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY
CENTRAL PARK WEST AT 79TH STREET, NEW YORK, NY 10024
Number 3661, 32 pp., 8 figures, 7 tables August 28, 2009
A New Species of the Rodent Genus Oecomys
(Cricetidae: Sigmodontinae: Oryzomyini) from
Eastern Bolivia, with Emended Definitions of
O. concolor (Wagner) and O. mamorae (Thomas)
MICHAEL D. CARLETON,1 LOUISE H. EMMONS,2 AND GUY G. MUSSER3
ABSTRACT
We describe a new species of Oecomys, O. sydandersoni (Cricetidae: Sigmodontinae), from the
Parque Nacional Noel Kempff Mercado in eastern Bolivia. One of its diagnostic traits, a derived
carotid circulatory plan, provides morphological evidence for its close relationship to O. concolor
and O. mamorae among the 15 species of Oecomys currently recognized. Notwithstanding this
shared trait, other morphological contrasts and morphometric analyses demonstrate the sharp
differentiation of the eastern Bolivian form from both of those species. Oecomys sydandersoni, n.
sp., is arboreal and was encountered above ground on limbs and woody vines only in densely
wooded hummocks scattered through grassland, in contrast to adjacent closed tropical deciduous
forest where three other species of Oecomys (O. bicolor, O. roberti, O. trinitatis) were obtained. The
new species represents the fourth sigmodontine rodent to be named from this restricted region
within eastern Bolivia since 1999. Its documentation served as a platform to summarize the
nomenclatural history, morphological recognition, and geographic distribution of O. concolor
(Wagner, 1845) and O. mamorae (Thomas, 1906) based on fresh examination of all type material
and museum specimens.
1 Division of Vertebrate Zoology (Mammalogy), American Museum of Natural History; Department of Vertebrate
Zoology, National Museum of Natural History, Smithsonian Institution, Washington, DC 20560-0111 (carletonm@si.
edu).
2 Division of Vertebrate Zoology (Mammalogy), American Museum of Natural History; Division of Mammals,
Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, DC
20560-0111 ([email protected]).
3 Division of Vertebrate Zoology (Mammalogy), American Museum of Natural History. Current address: 305
Clevington Way, Simpsonville, SC 29681 ([email protected]).
Copyright © American Museum of Natural History 2009 ISSN 0003-0082
2 AMERICAN MUSEUM NOVITATES NO. 3661
RESUMEN
Describimos una nueva especie de Oecomys, O. sydandersoni (Cricetidae: Sigmodontinae),
colectado en el Parque Nacional Noel Kempff Mercado al este de Bolivia. Una de las
caracteristicas diagnosticas, el plan de circulacion carotideo derivado, provee evidencia de su
relation cercana con O. concolor y O. mamorae entre las 15 especies de Oecomys reconocidas hasta
la fecha. Ademas de esta caracteristica compartida, otras caracteristicas morfologicas y analisis
morfometricos demuestran la gran differenciacion de la forma del este boliviano de las otras dos
especies. Oecomys sydandersoni, n. sp., es una especie arboricola y fue encontrada sobre el nivel del
suelo en ramas y lianas, solamente en montecillos boscosos esparcidos por la sabana, a diferencia
del bosque adyacente tropical deciduo donde las otras tres especies de Oecomys (O. bicolor, O.
roberti, O. trinitatis) fueron encontradas. Esta nueva especie es el cuarto roedor sigmodontino
descrito para esta zona del este boliviano desde 1999. Su documentacion sirve como una tribuna
para compendiar la historia natural, el reconocimiento morfologico, y la distribucion geografica de
O. concolor (Wagner, 1845) y O. mamorae (Thomas, 1906) basados en la examinacion del material
tipo y de especimenes de museo.
INTRODUCTION Carleton (2005) acknowledged 15 species of
Oecomys but urged the need for continued
Arboreal rodents of the genus Oecomys faunal survey and basic taxonomic revision
(Cricetidae: Sigmodontinae) inhabit Neo¬ to enhance understanding of its specific
tropical lowland rainforests from southern contents.
Central America, throughout the broad reach¬ During inventory of small mammals in
es of Amazonia, to the Atlantic Forest eastern Bolivia, conducted over the years
region of southeastern Brazil (Hall, 1981; 1997-2006, Emmons recovered four species
Emmons and Feer, 1997; Musser and of Oecomys in the Parque Nacional Noel
Carleton, 2005). Described as a subgenus of Kempff Mercado (Emmons et al., 2006),
Oryzomys (Thomas, 1906a), the rank of the Departamento de Santa Cruz. Valid names
taxon thereafter oscillated between subgenus could be reasonably assigned to three of the
(Goldman, 1918; Ellerman, 1941; Hersh- four morphologies—O. bicolor, O. roberti, and
kovitz, 1960; Cabrera, 1961; Hall, 1981) and O. trinitatis—based on current taxonomic
genus (Gyldenstolpe, 1932; Gardner and understanding, but the identity of the fourth
Patton, 1976; Carleton and Musser, 1984; proved to be problematic. Actually, three
Reig, 1984) until broad-scale morphological specimens of this indeterminate form had
and molecular studies secured its nomencla- been earlier collected in adjacent Departa¬
tural stature as a monophyletic genus of mento de Beni and were reported as O.
Oryzomyini (Smith and Patton, 1999; concolor based on certain characteristics of
Weksler, 2003, 2006). While phylogenetic the pelage and cranium (Musser and Carleton,
appreciation of Oecomys within the oryzo- 1993, 2005; Anderson, 1997). Additional study
myine kinship web has improved markedly, of all material has persuaded us that Emmons’
the number of valid species embraced by fourth form represents a new species of
the taxon remains uncertain. Hershkovitz Oecomys that we document herein. A key
(1960) consolidated some 25 species (e.g., diagnostic feature of the new species involves
Gyldenstolpe, 1932; Ellerman, 1941) into just its derived carotid arterial circulatory pattern,
two, bicolor and concolor, an underestimation a characteristic shared with two other
of diversity decidedly exposed by site studies Oecomys species, O. concolor (Wagner, 1845)
in Brazil and French Guiana that have and O. mamorae (Thomas, 1906b). Based on
documented four species in sympatry or close this potential synapomorphy (e.g., see
parapatry (Carleton et al., 1986, as reported Weksler, 2006), we critically differentiate the
in Voss and Emmons, 1996: appendix 8; new species in contrast to O. concolor and O.
Patton et al., 2000; Voss et al., 2001). In a mamorae and concurrently refine the defini¬
recent taxonomic compendium, Musser and tions and distributions of the latter two.
2009 CARLETON ET AL.: NEW SPECIES OF OECOMYS 3
Material and Methods MSU The Museum, Michigan State
University, East Lansing
Specimens examined consisted principally MVZ Museum of Vertebrate Zoology,
of prepared skins with their associated skulls University of California, Berkeley
housed in the following 17 natural history NMW Naturhistorisches Museum Wien,
collections, each preceded by the institutional Wien.
abbreviations adopted throughout the text, UCONN University of Connecticut, Storrs
UMMZ Museum of Zoology, University of
tables, and appendices. In addition, type
Michigan, Ann Arbor
specimens of 44 species-group taxa allocated
USNM National Museum of Natural
to Oecomys (sensu Musser and Carleton,
History, Smithsonian Institution,
2005) have been personally examined by at
Washington D.C. (formerly U.S.
least one of us, those in North American
National Museum)
collections by Carleton and Musser, those in
European museums by Musser, and one in Five external and 17 cranial dimensions
Brazil by Emmons. We lacked final catalog (values in millimeters, mm) were recorded and
numbers for some specimens now deposited in analyzed to quantify patterns of variation
the Instituto Nacional de Pesquisas da within and between population samples.
Amazonia, Manaus (INPA), or the Museo External variables were generally transcribed
de Historia Natural Noel Kempff Mercado, from original skin labels as penned by
Santa Cruz (MNK), and instead cited the collectors: total length (TOTL); length of tail
insitution’s abbreviation as hyphenated to the vertebrae (LT); length of hind foot, including
collector’s initials and field number. Latitudes the claw (HFL); length of ear (pinna) from
and longitudes used for mapping geographic notch (LE); weight in grams (WT). Length of
ranges are provided in appendix 1, along with head and body (HBL) was usually calculated
cartographic sources for determining those by subtracting the length of tail from total
coordinates. Full provenience as given by the length. The external data are presented in
collector and museum catalog numbers are tables to convey a general sense of bodily size
listed in the taxonomic accounts. and proportions but were not enlisted for
morphometric evaluations. Crania were
AMNH American Museum of Natural viewed under a dissecting microscope when
History, New York City measuring the 15 cranial and two dental
ANSP Academy of Natural Sciences,
variables to 0.1 mm by means of handheld
Philadelphia
digital calipers accurate to 0.03 mm. These
BMNH The Natural History Museum,
measurements, and their abbreviations as
London (formerly British Museum
employed in tables, follow the landmarks
of Natural History)
defined and illustrated in past oryzomyine
CAS California Academy of Sciences
CM Carnegie Museum of Natural studies (Carleton and Musser, 1995; Musser
History, Pittsburgh et al., 1998): occipitonasal length (ONL);
FMNH Field Museum of Natural History, greatest zygomatic breadth (ZB); breadth of
Chicago braincase at lateral extremes of lambdoidal
INPA Instituto Nacional de Pesquisas da ridge (BBC); depth of braincase (DBC);
Amazonia, Manaus breadth across the exoccipital condyles
MCZ Museum of Comparative Zoology, (BOC); least interorbital breadth (IOB); length
Harvard University, Cambridge
of rostrum (LR); breadth of rostrum (BR);
MN Museu Nacional da Universidade
postpalatal length (PPL); length of bony palate
Federal do Rio de Janeiro
(BPL); length of diastema (LD); length of
MNK Museo de Historia Natural Noel
incisive foramen (LIF); maximum breadth
Kempff Mercado, Santa Cruz
MSB Museum of Southwestern Biology, across the incisive foramina (BIF); breadth of
University of New Mexico, the bony palate across the first upper molars
Albuquerque (BBP); breadth of the zygomatic plate (BZP);
4 AMERICAN MUSEUM NOVITATES NO. 3661
coronal length of the maxillary toothrow RESULTS
(CLM); width of the first upper molar (WM1).
Within Muroidea, variations in the distal
Relative age was coarsely indexed by degree
branching of the stapedial artery, a major
of molar wear according to the four age-
classes (juvenile, young adult, full adult, and subdivision of the common carotid, are
old adult) recognized by Carleton and Musser especially helpful for preliminary taxonomic
(1989: 4-5). Anatomical terms follow Carleton sorting of specimens, for these arteries leave
and Musser (1989), Voss and Carleton (1993), their imprints on cleaned skulls in the pres¬
and Musser et al. (1998) for general features of ence/absence of certain cranial foramina and
the oryzomyine skull, Bugge (1970) for carotid vascular grooves. Morphological surveys of
vessels, Reig (1977) for molar cusps and muroid rodents over the past three decades
enamel folds, Wahlert (1985) for cranial have disclosed three principal themes of
foramina, and Voss (1993) for the tegmen stapedial branching that appear to be gener¬
tympani; also see Weksler (2006: appendix 2) ally conservative at the taxonomic levels of
for a useful synopsis of morphological char¬ genus to subfamily (Bugge, 1970; Carleton,
acters applied in past systematic studies of 1980; Carleton and Musser, 1984; Voss, 1988;
New World Muroidea. Steppan, 1995). The tribe Oryzomyini is
Univariate and multivariate computations exceptional in that all three circulatory plans
were restricted to specimens assigned to the are found among its different species groups
three adult cohorts (young, full, and old). and genera (Carleton and Musser, 1989; Voss
Standard descriptive parameters (mean, range, and Carleton, 1993; Musser et al., 1998;
standard deviation) were derived for the Weksler, 2006), and examples of Oecomys
species samples and are reported in table 4 exhibit two of these, here simply termed
for the larger samples. One-way analyses of “complete” and “derived.”
variance, discriminant functions, and prin¬ A complete carotid circulatory pattern (char¬
cipal components were computed using only acter state 0 of Carleton, 1980, or pattern one
the craniodental variables, all of which per Voss, 1988) characterizes most recognized
were first transformed to natural loga¬ species of Oecomys. This pattern, believed to
rithms. Principal components (PCs) and ca¬ represent the ancestral state for Muroidea
nonical variates (CVs) were extracted from the (Bugge, 1970; also see Weksler, 2006, for
variance-covariance matrix, and their loadings summary of recent studies), retains the supra¬
are expressed as Pearson product-moment orbital and infraorbital branches of the stape¬
correlations of the derived components dial artery (e.g., see Carleton and Musser, 1989:
or variates with the original variables. fig. 21B). Osteological landmarks of the supra¬
Projections of individual specimen scores orbital branch include the squamosal-alisphe-
onto principal components, or of OTU noid groove, where it crosses the inner surface
centroids onto canonical variates, are repre¬ of the squamosal and alisphenoid bones, and
sented as bivariate scatter plots, usually of the sphenofrontal foramen, where it enters the
the first two factors extracted. Similarity orbit as the opthalmic artery. The infraorbital
among the predefined geographic samples branch passes over the posterolateral corner of
was graphically summarized using general¬ the parapterygoid fossa, typically evidenced by
ized Mahalanobis distances between group a shallow depression on the pterygoid bone
(OTU) centroids, and OTUs were amalgam¬ (fig. 1), and reenters the base of the skull
ated by the unweighted pair-group method through the spacious posterior opening of the
using arithmetic averages. Type specimens alisphenoid canal; it reemerges onto the orbital
were used as cases in multivariate analyses floor through the anterior alar fissure as the
or entered as unknowns for a posteriori internal maxillary artery. The unreduced orbi-
OTU classification based on posterior proba¬ tomaxillary vessels supplied by the stapedial
bilities. All analytical procedures were pro¬ artery are reflected in the large, distinct
cessed using Systat for Windows (2002, stapedial foramen that straddles the petrotym¬
version 10.2). panic fissure (fig. 1). We could verify this
2009 CARLETON ET AL.: NEW SPECIES OF OECOMYS 5
Fig. 1. Ventromedial view of right otic capsule in two species of Oecomys illustrating osseous traits
associated with complete and derived carotid circulatory patterns (see text and table 1). Top, O. concolor
(AMNH 78073, an adult from Rio Casiquiare, Amazonas, Venezuela); bottom, O. bicolor (USNM 559396,
an adult female from Pakitza, Madre de Dios, Peru). Abbreviations: ab, auditory bulla (ectotympanic); bet,
bony eustachian tube; bo, basioccipital; cc, carotid canal; iag, groove for the infraorbital branch of the
stapedial artery; pac, posterior opening to the alisphenoid canal; pf, parapterygoid fossa; pt, pteriotic
(petrous portion of petro-mastoid); stf, stapedial foramen.
syndrome of cranial traits in the type specimens absence of the supraorbital branch; compres¬
of 41 species-group taxa assigned to Oecomys, sion or occlusion of the posterior opening to the
representing 13 currently recognized species ahsphenoid canal and absence of a posterolat¬
and their 28 attributed synonyms (table 1). eral groove on the parapterygoid plate accom¬
The derived carotid circulatory plan, char¬ pany the loss of the infraorbital branch (fig. 1).
acteristic of far fewer members of Oecomys, With reduction in its distal circulation, the
involves loss of both the supraorbital and stapedial artery is likewise extremely reduced
infraorbital branches of the stapedial artery and the stapedial foramen, if present, is minute
and attendant cranial modifications (character (fig. 1). In this condition, supply to the orbito-
state 3 of Carleton, 1980, or pattern 3 per maxillary region is assumed by a secondary
Voss, 1988). Lack of a squamosal-alisphenoid connection between the internal carotid artery
groove and sphenofrontal foramen attests the and the basally conjoined opthalmic and
6 AMERICAN MUSEUM NOVITATES NO. 3661
TABLE 1
TABLE 1
( Continued)
Character State of the Carotid Circulatory Pattern
in Species-group Taxa of Oecornys
(Arranged alphabetically by valid species and Species-group Taxa
chronologically by attributed synonyms.) Type Localities
(Holotypes) Complete® Derived13
Species-group Taxa O. concolor (Wagner, 1845) +
Type Localities Mouth of Rio Curicuriare, Brazil
(Holotypes) Complete® Derivedb (NMW B482)
0. auyentepui Tate, 1939 + marmosurus Thomas, 1899 +
Mt. Auyan-tepui, Venezuela Maipures, Colombia
(AMNH 131156) (BMNH 1899.9.11.38)
0. bicolor (Tomes, 1860) + O. flavicans (Thomas, 1894) +
Gualaquiza, Ecuador Merida, Venezuela
(BMNH 7.1.1.96) (BMNH 1894.9.25.14)
dryas Thomas, 1900 + illectus Bangs, 1898 +
Paramba, Ecuador Pueblo Viejo, Colombia
(BMNH 1899.12.5.4) (MCZ 8101)
benevolens Thomas, 1901 + mincae Allen, 1913 +
Chimate, Bolivia Minca, Colombia
(BMNH 1.2.1.14) (AMNH 15332)
rosilla Thomas, 1904 + O. mamorae (Thomas, 1906b) +
La Union, Venezuela Mosetenes, Bolivia
(BMNH 1904.5.7.37) (BMNH 1900.8.3.21)
nitedulus Thomas, 1910 + O. paricola (Thomas, 1904) +
Essequibo River, Guyana Igarape Assu, Brazil
(BMNH 1906.4.8.31) (BMNH 1904.7.4.63)
florenciae Allen, 1916 + O. phaeotis Thomas, 1901 +
Florencia, Colombia Sagrario, Peru
AMNH 33863 (BMNH 1901.1.1.23)
milleri Allen, 1916 + O. rex Thomas, 1910 +
Barao de Malgago, Brazil Supenaam River, Guyana
(AMNH 37117) (BMNH 1910.9.29.17)
trabeatus Allen and Barbour, 1923 + O. roberti (Thomas, 1904) +
Rio Jesusito, Panama Santa Anna da Chapada, Brazil
(MCZ 19837) (BMNH 1903.7.7.67)
endersi Goldman, 1933 + tapajinus Thomas, 1909 +
Barro Colorado Island, Panama Santa Rosa, Brazil
(UMMZ 64931) (BMNH 1909.3.9.9)
phelpsi Tate, 1939c + guianae Thomas, 1910 +
Mt. Auyan-Tepui, Venezuela Supenaam River, Guyana
(AMNH 131164) (BMNH 1910.5.4.23)
occidentalis Hershkovitz, 1960 + O. rutilus Anthony, 1921 +
Paramba, Ecuador Kartabo, Guyana
(BMNH 1899.12.5.4) (AMNH 42910)
O. catherinae Thomas, 1909 + O. speciosus (Allen +
Joinville, Brazil and Chapman, 1893)
(BMNH 9.11.19.24) Princes Town, Trinidad
(AMNH 5942/4672)
O. cleberi Locks, 1981 +
Fazenda Agua Limpa, Brazil
(MN 24131)
2009 CARLETON ET AL.: NEW SPECIES OF OECOMYS 7
TABLE 1 TABLE 1
( Continued) ( Continued)
Species-group Taxa Species-group Taxa
Type Localities Type Localities
(Holotypes) Complete® Derived13 (Holotypes) Complete® Derived13
trichurus Allen, 1899 + osgoodi Thomas, 1924 +
El Libano, Colombia Moyobamba, Peru
(AMNH 15328) (BMNH 1924.7.11.16)
caicarae Allen, 1913 + splendens Hayman, 1938 +
Caicara, Venezuela Mayaro, Trinidad
(AMNH 29875) (BMNH 1937.11.11.2)
0. superans Thomas, 1911 + aComplete: supraorbital and infraorbital branches of
Canelos, Ecuador the stapedial artery form major blood supply to the
(BMNH 1911.7.19.12) orbitofacial region; sphenofrontal and stapedial foramina
palmeri Thomas, 1911 + present; vascular grooves cross both the inner surface of
Canelos, Ecuador the squamosal and alisphenoid bones and the posterolat¬
(BMNH 1911.7.19.13) eral corner of the parapterygoid fossa; posterior opening
to alisphenoid canal large.
melleus Anthony, 1924 +
bDerived: supraorbital and infraorbital branches ab¬
Zamora, Ecuador
sent, distal orbitofacial circulation arising from secondary
(AMNH 36560)
anastomosis to the internal carotid; sphenofrontal fora¬
0. trinitatis (Allen and Chapman, + men absent, stapedial foramen absent or minute; no
1893) vascular grooves found on the inner surface of the
Princes Town, Trinidad squamosal and alisphenoid bones or on the posterolateral
(AMNH 5943/4673) corner of the parapterygoid fossa; posterior opening to
alisphenoid canal irregularly formed or occluded; second¬
subluteus Thomas, 1898 +
ary osseous groove internally crosses the roof of the
Cundinamarca, Colombia
parapterygoid fossa.
(BMNH 1898.7.3.2)
cBased on the type as restricted by Musser and Patton
fulviventer Allen, 1899 + (1989).
Quebrada Seca, Venezuela
(AMNH 14735) internal maxillary branches. This anastomosis is
palmarius Allen, 1899 + suggested by a groove that diagonally crosses
Quebrada Seca, Venezuela the parapterygoid plate, usually observed as a
(AMNH 14733) faint line on the translucently thin pterygoid
tectus Thomas, 1901 + bones, and connects medially with a very short
Bugaba, Panama alisphenoid canal (see Carleton and Musser,
(BMNH 1900.7.11.43) 1989: fig. 21 A); exit from the braincase into the
klagesi Allen, 1904 + orbital fossa is through the anterior alar fissure.
El Yagual, Venezuela We observed this co-occurrence of osteological
(AMNH 16966) features in only three type specimens associated
with Oecomys, those representing the species O.
frontalis Goldman, 1912 +
Corazal, Panama concolor (and its synonym marmosurus) and O.
(USNM 171531) mamorae (table 1).
All 26 specimens of the unidentified
helvolus Allen, 1913 +
Villavicencio, Colombia Oecomys from eastern Bolivia possess the
(AMNH 34578) derived carotid circulatory pattern as just
described for O. concolor and O. mamorae.
vicencianus Allen, 1913 +
Nonetheless, they differ appreciably from the
Villavicencio, Colombia
(AMNH 34584) latter two species in other aspects of external
size, chromatic and textural characteristics of
the pelage, and size and shape features of the
skull. We underscore the substantial cranial
AMERICAN MUSEUM NOVITATES NO. 3661
size and shape differences among the three in nent analyses, scatter plots of canonical
the following multivariate analyses of 17 log- variates, extracted from discriminant function
transformed, craniodental variables as mea¬ analysis of prior defined groups, predictably
sured on intact skulls of adult specimens. disclose completely nonoverlapping separa¬
Principal component comparisons of the tion of the eastern Bolivian form from both
unidentified Oecomys are employed first with O. concolor, and O. mamorae (fig. 3). Few
morphologically more similar O. concolor and variables account for the pronounced hiatus
then with geographically contiguous O. ma- along CV 1. Notable are the broader inter¬
morae, followed by discriminant function orbit (IOB) characteristic of O. concolor and
analysis of all three species samples. the sample from eastern Bolivia, as well as
Although initially allocated to O. concolor, their shorter basicranial axis (PPL), incisive
examples of the eastern Bolivian form prove foramina (LIF), and molar rows (CLM)
to be morphometrically distinct from that compared with those dimensions in O. ma¬
species. The eastern Bolivian form possesses a morae (tables 3, 4). The isolation of the
eastern Bolivian form on CV 2 issues from
generally smaller cranium, as indicated by the
its generally smaller size relative to both O.
disposition of specimens scores on the first
concolor and O. mamorae and from many of
principal component extracted (fig. 2, top)
the same cranial proportions divulged in the
and by the uniformly positive and strong
principal component comparison with O.
correlation coefficients of most original vari¬
concolor—spacious incisive foramina (BIF),
ables with PC I (r = 0.53-0.96, P < 0.001;
shorter bony palate (BPL), and shorter tooth-
table 2). Shape differences are indicated by
row (CLM). Mahalanobis distances between
significant loadings on the second principal
group centroids summarize these patterns of
component, foremost those variables that
variable covariations, revealing that the east¬
reflect size of the incisive foramina (LIF,
ern Bolivian form is phenetically closest to
BIF; table 2). The length and width of the
O. concolor and that the former two are
incisive foramina in the eastern Bolivian form
approximately equally differentiated from O.
are larger, both absolutely and relatively, than
mamorae.
the foramina in specimens of O. concolor
(table 4). Separation along PC II is also
influenced by the diminutive molars (CLM, TAXONOMY
WM1) possessed by the eastern Bolivian form
The above morphometric evidence per¬
and its relatively short hard palate (BPL)
suades us that Emmons’ fourth form from
compared with O. concolor (tables 2, 4).
eastern Bolivia represents a new species,
Comparable discrimination and pattern of
perhaps closely related to O. concolor and O.
variable loadings are apparent in the constel¬
mamorae as judged from their joint possession
lations of scores derived from principal com¬
of the derived carotid circulatory pattern. This
ponent analysis of the eastern Bolivian form
species is described next, and the taxonomic
and geographically contiguous populations of
history, morphological recognition, and geo¬
O. mamorae (fig. 2, bottom; table 2). Size again
graphic distribution of O. concolor and O.
emerges as a latent variable in the dispersion of
mamorae are then summarized based on all
scores along PC I (most correlations positive
specimens personally seen and identified by
and large), whereas shape differences involving
us. Synonymies presented below trace earliest
fewer select variables appear as important
identification and first subsequent usage of
correlations on PC II. The latter once more
other genus-group and species-group name
reflect the smaller molar rows observed in the combinations.
eastern Bolivian form and its wider incisive
foramina compared with O. mamorae; also
Oecomys sydandersoni, new species
noteworthy is the absolutely wider interorbital
region exhibited by the physically smaller Figures 4, 5; tables 4, 6
eastern Bolivian form (tables 2, 4).
Given the only marginal contact between
Oecomys concolor (part): Musser and Carleton, 1993: 716;
phenotypes apparent in the principal compo¬ Anderson (1997: 389).
2009 CARLETON ET AL.: NEW SPECIES OF OECOMYS 9
\
~1-1--1
_
0. sp. novum
ttv
▼
T ▼ A
T ▼
A aa
* t T
▼ A LAS AAA A
T A A A a A
A
A A
▼ A
▼ ▼ A AA
T
0. concolor
A A a a a
A
_1_ _J_1_1_1-
-3-2-10123
PCI (53.5%)
2
O. sp. novum f
A*
T
1
T O
T
CT>
0 °
t ▼
O O CP o oo o
□_ -1
-2 O. mamorae
-3-2-1 0 1 2 3
PC I (55.8%)
Fig. 2. Projection of specimen scores on first two factors (PC) extracted from principal component
analyses comparing samples of Oecomys: top, O. sp. nov. (N = 22) and O. concolor (N = 32); bottom, O. sp.
nov. (N = 22) and O. mamorae (N = 28). See table 2 for variable correlations and explanation of
percent variance.
10 AMERICAN MUSEUM NOVITATES NO. 3661
TABLE 2
Results of Principal Components Analyses Comparing Adult Oecomys sp. novum with O. concolor and
O. mamorae
(Based on 17 log-transformed craniodental variables; see Materials and Methods and fig. 2.)
O. sp. novum + O. concolor O. sp. novum + O. mamorae
Correlations Correlations
Variable PC I PC II PC I PC II
ONL 0.96*** 0.10 0 97*** -0.07
ZB 0.86*** 0.13 0.83*** 0.29
BBC 0.80*** 0.02 0 74*** -0.15
DBC 0 53*** 0.15 0.32 0.26
q
BOC 0.63*** -0.24 -0.28
IOB 0.54*** 0.13 -0.17 0.76***
LR 0.82*** 0.26 0.84*** -0.05
BR 0.84*** -0.04 q74*** 0.06
BZP 0.76*** 0.11 0.88*** -0.03
PPL 0 73*** 0.41** 0 9i*** -0.06
BPL 0.87*** -0.29* Q 7i*** -0.14
LD 0.84*** 0.35** 0.85*** 0.41**
LIF 0.35** 0 72*** 0.81*** -0.09
BIF -0.18 q 91*** 0.36 0.82***
BBP 0.82*** 0.11 0.78*** 0.07
CLM q 72*** -0.40** q 59*** -0.69***
WM1 0.64*** -0.37** 0.38 -0.58***
Eigenvalue 0.033 0.011 0.045 0.012
% Variance 53.5 17.5 55.8 14.9
*= P < 0.05; ** = P < 0.01; *** = P < 0.001.
Holotype: Museo de Historia Natural labels, but in 2004, they appended Huanchaca
Noel Kempff Mercado number 2679, an adult to their former designation of El Refugio. “El
male prepared as round skin and skull; Refugio,” “Huanchaca,” and the combined
collected 30 July 1997 by Louise H. Emmons form “El Refugio Huanchaca,” as applied in
(original field number LHE 1415). eastern Santa Cruz, are one and the same
External data recorded on the skin tag locality.
include: TOTL, 242 mm; TL, 124 mm; HFL, Diagnosis: A species of Oecomys (Sigmo-
23 mm; EL, 17 mm; WT, 45 g (see table 4 for dontinae: Oryzomyini) characterized by a
craniodental measurements of the type). The combination of medium size (HBL ~ 115-
animal was noted as having scrotal testes (11 135 mm, HFL - 23-25 mm, ONL - 29-
X 7 mm) and was captured “in pampa brush 31 mm), relatively short tail (TL ~ 125-
on vines.” MO mm), absolutely and relatively very wide
Type Locality: Bolivia, Departamento de incisive foramina, smaller molars (CLM ~
Santa Cruz, Provincia Velasco, El Refugio 4.4-4.7), presence of alisphenoid struts, and a
Huanchaca, 210 m; 14°46'01"S/61°02'02"W derived carotid circulatory pattern (skull
(field coordinates as given by the collector; lacking squamosal-alisphenoid groove, sphe¬
GPS, map datum WGS84). nofrontal foramen, and posterolateral groove
On older maps, the locality now known as on the parapterygoid plate; posterior opening
El Refugio Huanchaca appears only as to the alisphenoid canal compressed; stapedial
Huanchaca, a biological station with a few foramen absent; groove dorsally crossing the
buildings and an airstrip on private property parapterygoid plate present).
but now partly within the park. The present Referred Specimens: BOLIVIA: Beni,
owners of the estancia renamed it El Refugio, Rio Itenez, ca. 4 km above Costa Marques,
the place name that appears on specimen 12°29'S/64°15'W (AMNH 210023); Rio Ite-