A New Species of Thomasomys (Rodentia: Muridae) from Eastern Ecuador, with Remarks on Mammalian Diversity and Biogeography in the Cordillera Oriental
Author
VOSS, ROBERT S.
text
American Museum Novitates
2003
2003-12-09
3421
1
48
http://www.bioone.org/doi/abs/10.1206/0003-0082%282003%29421%3C0001%3AANSOTR%3E2.0.CO%3B2
journal article
10.1206/0003-0082(2003)421<0001:ANSOTR>2.0.CO;2
f4c2f80e-4917-4b5b-9415-0ee6377973ce
0003-0082
4734917
Thomasomys aureus
(Tomes)
Figures 11–13
SPECIMENS COLLECTED: 6.2 km (by road) W Papallacta,
11,700 ft
(AMNH 248281, 248498; UMMZ 127114, 155621–155624, 155626, 155707); Río Papallacta valley [
3– 5 km
by trail NNW Papallacta],
11,100 ft
(UMMZ 155625).
OTHER MATERIAL: None.
TAXONOMY: The
holotype
of
Thomasomys aureus
(BMNH 7.1.1.104) consists of the skin only of a specimen collected by Louis Fraser, allegedly at Pallatanga (
1°59'S
,
78°57'W
;
1500 m
above sea level) in the Ecuadorean province of
Chimborazo
(
Allen, 1914
;
Ellerman, 1941
;
Cabrera, 1961
), or at Gualaquiza (
3°24'S
,
78°33'W
;
971 m
above sea level) in the Ecuadorean province of
MoronaSantiago
(
Thomas, 1920
). Neither locality, however, is within the usual altitudinal range of this species (ca.
3000–4000 m
), and the exact provenance of Fraser’s Ecuadorean material is uncertain due to inadequate labelling and the lack of detailed field records (
Gardner, 1983
). Despite the absence of cranial material and a definite geographic datum, however, the
type
serves to establish that
aureus
is a distinctively large, shaggy rat with grizzled yellowishbrown dorsal fur; yellowwashed, graybased ventral fur; long, blackish mystacial vibrissae; dark, broad hind feet with semiopposable fifth digits; and a tail that is much longer than the combined length of headandbody. Other Ecuadorean specimens with these external characters exhibit the qualitative craniodental characters listed in
table 2
and approximate the range of morphometric variation summarized in
table 3
.
Fig. 11. Dorsal cranial views of eight
Thomasomys
species
that occur in the Cordillera Oriental of northern Ecuador. Top row (left to right):
T. aureus
(UMMZ 127114),
T. baeops
(UMMZ 155708),
T. cinnameus
(UMMZ 155671),
T. erro
(UMMZ 155713). Bottom row (left to right):
T. paramorum
(UMMZ 155737),
T. rhoadsi
(AMNH 66256),
T. silvestris
(USNM 513592),
T. ucucha
(UMMZ 155644).
Fig. 12. Ventral cranial views of eight
Thomasomys
species
from the Cordillera Oriental of northern Ecuador. Top row (left to right):
T. aureus
(UMMZ 127114),
T. baeops
(UMMZ 155708),
T. cinnameus
(UMMZ 155671),
T. erro
(UMMZ 155713). Bottom row (left to right):
T. paramorum
(UMMZ 155737),
T. rhoadsi
(AMNH 66256),
T. silvestris
(USNM 513592),
T. ucucha
(UMMZ 155644).
Among the several nominal taxa currently synonymized with
Thomasomys aureus
by
Musser and Carleton (1993)
, the same qualitative and morphometric traits are shared by
princeps
Thomas (1895a)
from the eastern Andes of
Colombia
and by
altorum
Allen (1914)
from the western Andes of
Ecuador
. Other putatively synonymous taxa, however, differ conspicuously from
aureus
in sidebyside morphological comparisons:
popayanus
Allen (1912)
from the western Andes of
Colombia
and
nicefori
Thomas (1921)
from the Colombian central Andes have substantially shorter (
33–34 mm
) hind feet and smaller (6.0 –6.6 mm) molar toothrows, whereas
praetor
Thomas (1900)
from northern
Peru
has grayish dorsal fur, palesilvery ventral fur, pale hind feet, shorter tail, narrower interorbit, and a broad, distinctively flattened braincase. These three taxa were first treated as conspecific with
T. aureus
by
Cabrera (1961)
, who (as usual) offered no explanation for his nomenclatural changes. In view of such trenchant character differences, at least four species appear to be represented in this complex:
T. aureus
(including
altorum
and
princeps
),
T. praetor
, and
T. popayanus
(possibly including
nicefori
).
Fig. 13. Lateral cranial and mandibular views of eight
Thomasomys
species
from the Cordillera Oriental of northern Ecuador. Left side (top to bottom):
T. aureus
(UMMZ 127114),
T. baeops
(UMMZ 155708),
T. cinnameus
(UMMZ 155671),
T. erro
(UMMZ 155713). Right column (top to bottom):
T. paramorum
(UMMZ 155737),
T. rhoadsi
(AMNH 66256),
T. silvestris
(USNM 513592),
T. ucucha
(UMMZ 155644).
TABLE 3
Measurements (mm) and Weights (g) of
Thomasomys aureus
FIELD OBSERVATIONS
:
The
10 specimens
of
Thomasomys aureus
that I collected near
Papallacta
in 1978 and 1980 were all taken in
Subalpine Rain Forest
at elevations ranging from
3380 to 3570 m
.
Six
were trapped in wellworn paths through mats of moss and liverworts on horizontal tree limbs, and four were trapped on the ground.
Of
the latter, two were trapped at the edge of a stream, one was trapped among tall grass in a clearing, and one was trapped in a runway through dense mats of moss
.