A new species of Aepeomys Thomas, 1898 (Rodentia: Muridae) from the Andes of Venezuela

10 Pages·2001·5.9 MB·English

by  J Ochoa

226 M. P. Heide-Jorgensen etal.
jectively based. The age for change from Acknowledgements
grey to white as reported from other areas
is fairly similar to what we have seen in This study was supported financially by the Fish-
West Greenland (Sergeant 1973; Ognetov eries Directorate of the Greenland Home Rule
1981), but detailed comparisons are not Government and it was conducted by the Green-
land Fisheries Research Institute. The beluga
possible because the Statistical methods hunters in West Greenland are thanked for pro-
used for deriving the mean age at change viding the samples of their harvest. We thank
of colour are not specified. However, for Royal Greenland and Greenland Trade Depart-
belugas in East Baffin, Brodie (1971) re- ment for help with collection of samples. J.Jen-
ported that whitening occurs after 6 and sen, J.Teilmann, F.Thomsen, and RBarner
7 yr in females and males respectively, Neve did the age determinations and the data
which is also evident from this study. entry. G.N. Ognetov (SEV-Pinro, Arkhangelsk)
kindlymadehisdataonwhitewhaleagefrequen-
ciesintheWhite andKaraseasavailable. R M0L-
ler Lund and U. Siebert are gratefully acknowl-
edged for making tne map and the German
translationofthe abstract.
Zusammenfassung
Alters- und Geschlechtsverteilungvon Belugafängen, Delphinapterus leucas,
in Westgrönland und Westrußland
Alter und Geschlechtwurden von Belugas oderWeißwalen Delphinapterus teucas, bestimmt, die von
1985-86 und 1989-97 von Eskimos in Westgrönland erlegt wurden. Der Probenumfang umfaßte
712 Weibchen und 596 Männchen. Es gab eine klare Trennung der Wale in der Jagdfischerei, die
während des Herbstes in Qaanaaq (früher als Avenersuaq bekannt) und Upernavik, das nördlich
des 74°N Breitengrades liegt, stattfindet. Vor allem nicht geschlechtsreife Wale beider Geschlech-
ter wurden zusammen mit geschlechtsreifen Weibchen gefangen. Zähne dienten der Altersbestim-
mung. Das Alter wurde an Jahreszuwachsringen (GLGs) im Dentin ermittelt unter der Annahme,
daß zwei Zuwachsringe pro Jahr entstehen. Mittelwert und Median für Alter nahmen bei beiden
Geschlechtern aus Upernavikvon 1985 bis 1994 langsam zu. Sowohl nichtgeschlechtsreife als auch
geschlechtsreife Wale wurden in den Überwinterungsgebieten der Disko Bucht und südlich des 70°N
Breitengrades entnommen. Die Überlebensrate wurde nach zwei Methoden bestimmt: nach Robson
und Chapman (1961) und über den natürlichen Logarithmus des negativen Exponenten einer an
die Altersfrequenz angepaßten Kurve. Die Abschätzung der Überlebensrate wurde erschwert durch
eine große Anzahlvon Walen, denen bedingt durch eine Abnutzung der Zahnkrone nurein Minima-
lalter zugeordnet werden konnte (d.h. keine Neonatlinie im Dentin). Die offensichtliche Überle-
bensrate von Belugas vor Westgrönlands wurde auf 0,81 und 0,79 für Weibchen bzw. Männchen
geschätzt. Korrekturen dieser Abschätzung für eine beobachtete Bestandsabnahme von 4,7% pro
Jahr ergaben eine tatsächliche Überlebensrate von 0,85 und 0,82 für Weibchen bzw. Männchen.
Die Schätzwerte dertatsächlichen Überlebensrate sind geringerals die, welche fürdie Belugapopu-
lation im Weißen Meer und der Karasee ermittelt wurden, fiirdie Altersdaten aus den 70er und frü-
hen 80er Jahren zur Verfügung standen, sowie publizierten Raten für Belugas aus Alaska (1977-
83) miteinervergleichbaren Alterszusammensetzung. Da der Grad der Bejagung in diesen Gebieten
wesentlich niedrigerist, bestätigt die geringere Überlebensrate vor Westgrönland deutlich eine Ab-
nahme der Population. Der Wechsel in der Hautfärbung von Grau zu Weiß tritt im mittleren Alter
von 8,5 und 9,1 Jahren und bei einer mittleren Länge von 367 cm und 445 cm bei Weibchen bzw.
Männchen auf.
Age and sex distributionsin the catches ofbeLugas 227
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Mamm. bioi. 66 (2001) 228-237 $St Mammalian Biology
© Urban & FischerVerlag v
http://www.urbanfischer.de/journals/mammbiol ^SfF Zeitschriftfür Säugetierkunde
Original investigation
A new species of Aepeomys Thomas, 1898
(Rodentia: Muridae) from the Andes of Venezuela
ByJ. Ochoa G., MarisolAguilera, V. Pacheco, and P. J. Soriano
Asociaciön Venezolana para La Conservaciön de Areas Naturales Caracas, Venezuela; Departamento de Estudios
Ambientales, Universidad Simon Bolivar, Caracas, Venezuela; Department of Mammalogy, American Museum of
NaturalHistory, NewYork, USA; Departamento de Biologia, Universidadde LosAndes, Merida,Venezuela.
ReceiptofMs. 25. 04. 2000
AcceptanceofMs. 20. 09. 2000
Abstract
A new species of Neotropical rodent of the genus Aepeomys is described based on 24 specimens
collected in the Andean region ofVenezuela (Lara and Trujillo States). Among the diagnostic char-
acters are: large size; firstand fifth digits ofpes notextending beyondthe commissure ofdigits 2-
3 and the first interphalangeal of digit four, respectively; posterior margin of zygomatic ramus of
the maxilla with a distinctive notch; palate extending to the posterior border of M3 or behind this
molar; and paraflexus of M1 and M2 divided by an enamel bridge. In addition, the new species
shows the following karyological features: 22 chromosomal pairs (2n =44); 46 autosomal arms
(FN =46); a low proportion oftwo-armed elements; automosal chromosomes with abundant hete-
rochromatin around the pericentromeric areas; and short arms of chromosomes X and Y entirely
heterochromatic. According to the most recent systematic revision ofthe species assigned to Aepe-
omys, only two forms could be considered as members ofthis genus: A. lugens (the type species)
and the taxon described herein. Both have geographic distributions restricted to highlands from
the northern Andes, where the new species inhabits primary cloud forests and päramos located in
the northeastern extreme ofthe Venezuelan Andean Cordillera.
Key words: Aepeomys, Thomasomyine, Taxonomy, Andes, Venezuela
Introduction
Neotropical sigmodontine rodents of the Laverde et al. 1997; Musser and Carleton
genus Aepeomys are members of the tho- 1993; Reig 1986; Voss 1993). After the ori-
masomyine group, together with six addi- ginal description of Aepeomys by Thomas
tional genera whose systematic and phylo- (1898), some authors have considered this
genetic relationships remain unclear: taxon as a synonym of Thomasomys (e.g.,
Delomys Thomas, 1917; Phaenomys Tho- Cabrera 1961; Ellerman 1941; Handley
mas, 1917; Rhagomys Thomas, 1917; Rhi- 1976). Nevertheless, the results of the most
pidomys Tschudi, 1844; Thomasomys recent systematic revision of these Andean
Coues, 1884; and Wilfredomys Avila-Pires, genera (Pacheco unpubl. data) and several
1960 (Aguilera et al. 1994, 2000; Gömez- previous publications (e.g.. Aguilera et al.
1616-5047/01/66/04-228 $15.00/0.
Newspecies ofAepeomysfrom Venezuela 229
1994; Gardner and Patton 1976; Musser taciön Biolögica de Rancho Grande (EBRG),
and Carleton 1993; Reig 1986; Soriano Maracay,Venezuela;theColecciöndeVertebrados
and Ochoa 1997; Soriano et al. 1998) are delaUniversidadde LosAndes(CVULA),Meri-
coincident in considering them as differen- da, Venezuela; and the Colecciön de Vertebrados
delaUniversidadSimonBolfvar(CVUSB), Cara-
tiated taxa.
cas, Venezuela. Species, individuals and localities
Four nominal species of Aepeomys have correspondingtothismaterialareasfollows:Aepe-
been described (Cabrera 1961; Musser omysfuscatus (1; holotype). Colombia: Valle del
and Carleton 1993), although at the pre- Cauca, San Antonio, near Cali, 2135m (AMNH-
sent time only two of them are recognized 32230). Aepeomys lugens (21, including two topo-
basutviaolnisdrteasxtari(cbtoetdhtohahvieghgleaongdrsapihnitchaelndoisrttrhi-- nteyjpoess,).2V4eknemzuWelaM-eMreirdiad,a2S9ta2t8e:mP(äArMamNoH-L9o6s16C9o;-
ern Andes): Aepeomys lugens (Thomas, holotype of A. ottlevi); 5.5km E+2km S Tabay
w1e89s6t)e,rnreVceonredezduelina steoverAanldleoacanlitEiecsuafdroorm; 21(50M5i27d00d)ml;e1(RkEemBfuRgNGi-o+1)5,25k72m160W0anmdMer(1i5E5dB7aR2)G(;-S1aEn5lt5a6M9Roorsarano)d,,
andA.fuscatus (Allen, 1912), known from 9kmSSWMeridaCity,2160m(EBRG-22009and
the western and central Andes of Colom- 22010; topotypes). Tachira State: Päramo Los Co-
bia. However, the highly differentiated cra- lorados (Parque Nacional Päramos Batallön y La
nial morphology shown by A.fuscatus with Negra), 12km SSE El Cobre, 3200m (EBRG-
respect to A. lugens (the type species of 21513 to 21523; CVULA-5747, 5751, and 5753).
the genus) and other related forms, has Aepeomys reigi (15). Venezuela-Lara State: El
beenused among the arguments toconsider YBlaacnaqmubitüo,, 11670k0mmS(ECVSUaLnAar-e2,73P8a;rquEeBRGNa-c4i2o0n8a,l
A.fuscatus as representative of a neglected
21735, 21440, and 22580to22582); RoadEl Blan-
taxon whose evolutionary lineage could be quito-Sanare, km 6, Parque Nacional Yacambü,
more related with the oryzomyine tribe, re- 1700m (EBRG-10621);ElAvileno,nearElBlan-
presenting perhaps an undescribed genus quito, 9km SE Sanare, Parque Nacional (Yacam-
(Pacheco and Voss unpubl. data). bü, 1600m (CVULA-2710 and 2718). Trujillo
As part ofthe results ofa field study on the State: Macizo de Guaramacal, 9 kmESE Boconö,
smallmammalcommunitiesinhabitinghigh- Parque Nacional Guaramacal, 3100m (CVULA-
land ecosystems from the Andean region of 3350);Guaramacal,5kmEBoconö,ParqueNacio-
Venezuela (Lara and Trujillo States), we TnaolrnGau,a7rakmmacEalB,oc2o2n3ö0,mPar(qCuVeULNaAc-i3o1n3a9l)G;uaPircaamLaa-
caught a series of thomasomyine specimens cal,2300m(EBRG-22714);14to15kmETrujillo,
whose general morphology corresponds to near Hacienda Misisi, 2225 to 2350m (EBRG-
Ateerpnaelo,mcyrasni(asle,nasundstkraicrtyoo)l,oaglictahloufgehattuhreeisraerxe- n1e5z5u6e7laa:nd3515k5m68)S.+T2h2okmamsWomySsanhyClroipshtiolbuasl((5B).ueVnea-
not referable to previously known species Vista), Tachira State, 2395m (EBRG-15597 to
assigned to this genus. Apparently, they re- 15601). Thomasomys laniger (5) Venezuela: 4km
present a new species that we describe be- S+6.5 kmETabay(LaCoromoto), MeridaState,
low. Some ofthese specimens, in addition to T3a1b7a0ym(n(eEaBrRLGa-1C5or2o2m7ottoo)1,52M3e0)r;id5akSmtatSe,+372k5m1mE
others collected in the Venezuelan Andes (EBRG-15231). Thomasomys vestitus. (1) Vene-
and cited herein as representatives of the zuela: El Baho, 3km SE Santo Domingo, Merida
newtaxon,wereformerlyrecordedasAepe- State,3010m(EBRG-32012).
omys lugens or Aepeomys sp. by Handley Age criteriafollowVoss (1991). Cranialmeasure-
(1976), Soriano et al. (1990), and Aguilera mentswere takenaccordingtoVoss (1988, 1991).
et al. (1994, 2000). Nomenclature ofthe occlusal components ofmo-
lar teeth follows Reig (1977). Karyological ana-
lyses were carned out on 13 specimens of A. lu-
gens and nine specimens representing the new
Material and methods taxon(fivefromLaraState andfourfromTrujillo
State), including the sample described by Agui-
Specimens examined (all adults) are deposited in leraet al. (2000). Bone marrowmetaphase chro-
the following institutions: American Museum of mosomes were obtained by a modification of
NaturalHistory(AMNH);the ColecciöndelaEs- Ford and Hamerton's (1956) in vivo colchicine
230 OcHOAetaL
technique. C- and G-banding patterns were ob- pelage, fused sphenoccipital suture, and the
tained as described by Barros and Patton (1985) third molar erupted (age class IV). Col-
manodsoCmheiarneolmleinceltatalu.re(19f72o)l,lorweesdpecLteivvealny. eCthroal-. gleucstted19b8y6 aMtaErlisBollanqAugiutiol,ePraarqeutealN.acinioAnua-l
m(1a9l64a)r.mFnuunmdbaemresn.tal numbers (FN) are autoso- Yacambü, 17 km SE Sanare, Lara State,Ve-
m
nezuela, 1600 (approx. 9°40' N; 69°37'W;
Fig. 1).
Results Paratypes: Seven specimens (6 as dry skins
Aepeomysreiginewspecies and skulls; one in alcohol) with karyotype
analysis: Lara State, Parque Nacional Ya-
Holotyoe: A female (dry skin, skull, and cambü, El Blanquito, 17 km SE Sanare,
karyotype analysis; CVUSB-928) with adult 1600m; 3 males and 1 female collected by
Newspecies ofAepeomysfrom Venezuela 231
M. Aguilera et al. (CVUSB-927, 1365, education and encouragement of many La-
1419, and 1420). Trujillo State, Parque Na- tin American mammalogists.
cional Guaramacal (approx. 9°15'N; Distribution: Known only in highlands
70°12'W), Pica La Torna, 7 km E Boconö, (1600-3230m) from the northeastern ex-
2300m; 1 male and 2 females collected by treme of the Venezuelan Andes (Lara and
J. Ochoa et al. (EBRG-22715 to 22717). Trujillo States).
Etymology: The epithet reigi honors the Diagnosis: Size large for the genus as indi-
memory of Dr. Oswaldo Reig, who de- cated by external andcranialmeasurements
voted his life to the study ofthe systematics (Tab. 1), in addition to postcranial skeleton
and evolution of South American rodents, development; first and fifth digits of pes
and made important contributions to the not extendingbeyond the commissure ofdi-
Table 1. Selected externaland cranial measurements (in millimeters) ofadult specimens ofAepeomys reigiand
Aepeomystugens(ageclasses2-4)from Venezuela. Dataare: Mean±SD, (ränge), andsamplesize.
1Sampleincludestwotopotypesandthe holotypeofAepeomys(seespecimensexamined).
Measurement A. reigi A. Lugens1
Lengthofheadand body 113.6±5.88 110.1±7.54
(104-125)15 (100-119)7
Lengthoftail 127.1±8.29 121.7+4.15
(116-142)15 (114-127)7
Lengthofhindfoot 27.9±1.30 27.0±3.96
(25-30)15 (20-30)7
Condylo-incisivelength 27.8±0.84 26.6±0.58
(26.6-29.3)16 (25.8-27.6)17
Lengthofdiastema 8.6±0.31 8.2±0.25
(8.0-9.0)18 (7.7-8.7)18
Lengthofmolars 4.5±0.11 4.3±0.12
(4.3-4.8)18 (4.0-4.4)18
Lengthofincisiveforamen 5.6±0.22 5.5±0.20
(5.2-6.0)16 (5.1-5.9)18
Breadthofincisiveforamen 2.4±0.18 2.3±0.14
(2.2-2.7)16 (2.0-2.5)18
Breadthofrostrum 5.0±0.23 4.5±0.27
(4.6-5.3)14 (4.0-5.1)16
Breadth ofpalatalbridge 3.8±0.16 3.5±0.25
(3.5-4.0)17 (3.0-4.0)17
Breadthofzygomaticplate 1.8±0.13 1.8±0.14
(1.6-2.1)18 (1.5-2.0)18
Leastinterorbitalbreadth 6.1±0.17 6.0±0.26
(5.9-6.4)17 (5.6-6.4)18
Breadth ofbraincase 13.3±0.22 13.1±0.35
(12.9-13.7)17 (12.4-13.8)18
Zygomaticbreadth 14.8±0.37 14.1±0.38
(14.2-15.6)15 (13.6-14.9)17
Depthofincisors 1.3±0.11 1.2±0.11
(1.0-1.4)17 (1.0-1.4)18
Lengthoforbitalfossa 9.1±0.24 8.4±0.21
(8.6-9.6)17 (8.0-8.8)17
232 OchoaetaL
gits 2-3 and the first interphalangeal ofdig- averages approximately 50% of their re-
it four, respectively; posterior margin of spective toothrows). Upper molars with
zygomatic ramus of the maxilla with a dis- rounded protocone and hypocone, and the
tinct notch; palate extending to the poster- paracone and metacone antero-posteriorly
iorborderofM3 orbehind this molar; inter- sharp. Paraflexus of M1 and M2 divided by
parietal length (along an antero-posterior an enamel bridge that crosses from the
axis) near half of parietal length; and para- paracone tothe base ofthe anteroloph,pro-
fiexus of M1 and M2 divided by an enamel ducing an internal fosseta. M3 with triangu-
bridge that crosses from the paracone to lär shape in dorsal view. Mi with a distinc-
the base of the anteroloph. Karyotype with tive protolophid in most specimens. which
22 chromosomal pairs (2n = 44), 46 autoso- reaches the cingulum.
mal arms (FN = 46). a low proportion of Skull with general appearance resembling a
two-armed elements, the automosal chro- typicalAepeomys (see Fig. 2 and 3 for com-
mosomes with abundant heterochromatin parisons with A. lugens). Rostrum narrow
around the pericentromeric areas, and the and elongated (approx. 1/3 of the greatest
short arms of the chromosomes X and Y length of skull), with acute profile and only
entirely heterochromatic. the external capsule of the nasolacrimal
Description: Length of head and body 104- foramen exposed in dorsal view; nasal and
125 mm. Tail approximately as long as body premaxillary bones extending beyond the
(Tab. 1), sparsely covered by short dark- anterior surface of incisors and the gnathic
brown hairs and unicolored (dark above process to form a distinct rostral tube. Na-
and below). Legs, heels, and dorsal surface sals laterally concave and flat in dorsal pro-
of pes sparsely covered by brown hairs. file, forming a continuous surface with the
Body pelage dense and soft (longer in spe- premaxillae; posterior border extending to
cimens from the highest altitudes). Dorsal thelevelofthezygomaticplate. Interorbital
coloration ranging from dark gray-brown constriction relatively broad« without con-
to reddish gray-brown, with moderately to cealing (in dorsal view) the labial ridge of
intensively hoary appearance. Dorsal für maxillary and the molars. Braincase moder-
consisting of shorter hairs (approx. 9- ately inflated and slightly concave in dorsal
12 mm) with golden tips and scattered long- profile; the posterior surface concealing the
er hairs (approx. 12-15 mm) with dark occipital condyles in dorsal view. Interpari-
brown tips (in afewcaseswithwhitishtips); etal length (along an antero-posterior axis)
both having the basal 75% gray. Ventral near half of parietal length. Lambdoidal
pelage shorter (approx. 7 mm) and paler ridges scarcely developed. Zygomatic
than dorsum. ranging from moderately to arches completely ossified. filamentous and
intensively hoary (hairs with golden tips fragile. Zygomatic plate relatively narrow
and the basal 75% gray). Pinnae 18-21 mm (Tab. 1; Fig. 3), with the posterior edge ex-
long and furred on both sides: inside part tending to the first molar (Fig. 2). Posterior
yellowish, contrasting in color with the dor- margin of zygomatic ramus of the maxilla
sal für. Manus cream-colored and paler with a distinct notch. Lumen of the infraor-
than hind feet. Pes narrow and long bital foramen compressed laterally and ex-
(adapted for terrestrial life; Tab. 1); first panded dorso-ventrally. Gnathic process
and fifth digits not extending beyond the scarcely developed. Masseteric tubercle
commissure of digits 2-3 and the first inter- large. Palatal bridge moderately long
pInhcailsaonrgseanlarorfodwigaitndfomuro,derresapteecltiyvedleyv.eloped b(Toarbd.er1;oFfigM. 32).orebxethenidnidngthitsomtohlearp.osPtoesrtieor-r
(not robust), with sharp tips. Upper incisors iormargin ofpalate without medial process
with the anterior surface slightly concave. in most specimens; therefore, the anterior
Maxillary and mandibular toothrows margin of the mesopterygoid fossa has a
relatively short (Tab. 1; Fig. 2); first shallow shape. Incisive foramina extending
molars antero-posteriorly elongated (length posteriorly beyond the masseteric tubercle.
Newspecies ofAepeomysfrom Venezuela 233
Fig. 2. Dorsaland ventralviews ofcrania ofAepeomys iugens (topotype; a, b), Aepeomysreigi(holotype; c, d),
and Thomasomyslaninger(e, f).Approx.XI.9.
withoutreachingthe level ofthe first molar; Comparisons: Among the thomasomine
margins of the anterior half strongly con- group, the genus most closelyrelated toAe-
vergent anteriorly. Postglenoid foramen peomys is believed to be Thomasomys
compressed dorso-ventrally and expanded (Aguilera et al. 2000; Gardner and Pat-
antero-posteriorly. Foramen magnum with ton 1976), whose cranial morphology is
the inferior border almost reaching the lev- clearly differentiated from A. reigi and
el of the auditory bulla. Auditory bulla A. Iugens in the following features (Fig. 2
moderately inflated. Mandible with the tip and 3): shorter rostrum; zygomatic arches
of the condylar process behind the angular more expanded laterally; narrower interor-
process. bitalregion; braincase lessinflated atthe le-
Karyotype with 22chromosomal pairs vel oflambdoidal ridges; broaderzygomatic
(2n=44), 46 autosomal arms (FN=46), plate; larger incisive foramina (almost
and low proportion of two-armed elements reaching the first molars); and shorter pal-
(Aguilera et al. 1994). Automosal chromo- ate (posterior border not extending beyond
somes with abundant heterochromatin the third molar). In addition, Venezuelan
around the pericentromeric areas. Short species of Thomasomys are larger (7^ aur-
arms of chromosomes X and Y entirely eus, T hylophilus, and T. vestitus) and/or
heterochromatic (Aguilera et al. 2000). have much paler brownish für (T. hylophi-
234 Ochoaetal.
M
a (near or before the posterior border of 3
in A. Iugens): posterior margin of palate
without medial process in most specimens
(therefore the anterior margin of the me-
sopterygoid fossa is shallow rather than in-
cipiently biconcave as in A. Iugens): maxil-
M
lary toothrow relatively longer; 3 larger
and triangulär in dorsal view (rounded in
A. Iugens); M1 and M2 with paraflexus di-
vided by an enamel bridge (continuous in
most specimens of A. Iugens): coronoid
and condylar processes broader and larger.
producing deeper sigmoid and angular
notches. respectively. Mi with a distinctive
protolophid in most specimens. which
reaches the cingulum (reduced or absent in
A. Iugens). Some ofthese features (particu-
larly those related with cranial and dental
morphology) show the maximun diver-
gence in specimens of A. reigi from Lara
State. In addition. A. Iugens has a very dif-
ferent karyotype, with fewer chromosomal
pairs (2n = 28 vs 2n = 44). more autosomal
arms (FN = 48 vs FN =46), and a lower
concentration of heterochromatin (espe-
pFiogt.yp3e.;Laa)t,erAaelpveioemwyssofrecigrian(ihaoLooftAyepep;eobm),ysanidugTehnosm(atso-- caiuatlolysocmoanlspipaciurosusanindtthheeshYortcharrommsoosfomtew:o
omyslaniger(c). Approx. XI.8. Aguilera et al. 1994, 2000). These chromo-
somal variations were consistent when we
Ins. T. vestitus and T. laninger) than Aepe- compared A. reigi with specimens ofA. Iu-
omys Iugens andA. reigi. gens from two localities in Venezuela: the
With respect to the species previously in- type locality (El Morro, Merida State) and
cluded withinAepeomys.A. reigi resembles Päramo Los Colorados. Tächira State
the external and cranial morphology of (Aguilera et al. 2000).
A. Iugens, except for the following differ- Regarding A.fuscatus the external and cra-
ences: size larger (Tab. 1): für on head and nial features ofthis species show a high de-
body shorter and rougher: manus and pes gree of differentiation withA. reigi, reveal-
broader; legs, heels. and dorsal surface of ing a morphological pattern that appears to
pessparcelyhaired (denselyhairedinA. Iu- be taxonomically separated from the tho-
gens): first and fifth digits of pes shorter; masomyine group and perhaps corresponds
posterior margin ofzygomatic ramus ofthe to a taxon whose evolutionary lineage is
maxilla with a distinct notch. rather than more relatedwith the oryzomyine tribe (Pa-
shallow as in A. Iugens (as consequence. in checo and Voss unpubl. data). Among the
A. reigi the orbital fossa is larger. Tab. 1): most conspicuous characteristics in A.fus-
incisive foramina broader. with margins catus supporting this assessment are: darker
showing a more convergent position ante- für coloration: shorter and broader rostrum
riorly: interparietal longer in most speci- (without the acute profile shown byA. reigi
mens (antero-posterior midline near halfof and A. Iugens): anterior portion of zygo-
the parietal length, rather than 30^-0% as matic arches more expanded and broader:
in A. Iugens): palate extending to the pos- broader zygomatic plate: narrower interor-
terior border of 1VT or behind this molar bital breadth: braincase less inflated: short-
Newspecies ofAepeomysfrom Venezuela 235
er incisive foramina and palate; and broad- with a primitive condition in eukariotic
er mandibular branches. These features, in chromosomal evolution (Imai 1991).
addition to the extremely high number of The geographic distribution of A. reigi
chromosomal pairs (2n= 54) and autosomal seems to be allopatric with respect toA. lu-
arms (FN = 62) reported by Gardner and gens, at least in the northeastern extreme of
Patton (1976) for A.fuscatus are clear evi- the Venezuelan Andean Cordillera. How-
dences of a differentiated evolutionary pat- ever, we donotrejectthe possibilityofsym-
tern with respect toAepeomys. patric distribution in highlands (>1500m)
near to the border of Merida and Trujillo
States. Future karyological studies, in a
Discussion more extensive area, are required to pro-
vide a further diagnosis on the biogeo-
The morphological Variation between graphic patterns of these taxa. Other non-
A. reigi and A. lugens, in addition to the volant small mammals recorded at Yacam-
high degree of differentiation in the num- bü and Guaramacal are: Coluromysphilan-
ber and structure of chromosomes, support der, Didelphis albiventris, Didelphis marsu-
the hypothesis of evolutionary divergences pialis, Gracilinanus dryas, Marmosops
in both species, such as it has been pro- fuscatus, Micoureus demerarae, Cryptotis
posed for other thomasomyine rodents meridensis, Mustela frenata, Sciurus grana-
(Gardner and Patton 1976; Gömez-La- tensis, Heteromys anomalus, Akodon urichi,
verde et al. 1997). Despite the higher di- Ichthyomys hydrobates, Microryzomys mi-
ploid number in A. reigi with respect to nutus, Neacomys tenuipes, Oecomys flavi-
A. lugens (44 vs 28), and based on their si- cans, Oligoryzomys fulvescens, Oryzomys
milarities in fundamental numbers (46 vs meridensis, Rhipidomys venustus, Rhipid-
48, respectively), we postulate that karyolo- omys venezuelae and Thomasomys laninger
gical differences found in these species (Soriano et al. 1990).
could be reached by chromosomal rearran- TheknownecologicaldistributionofA. reigi
gements evolving principally robertsonian correspondstoprimarycloudforests (humid
changes (Aguilera et al. 2000). montane forest according to Huber and
An important aspect within the evolution- Alarcön 1988) and small patches of pära-
ary context of Aepeomys species, is the di- mos surrounded by continuous masses of
rection of chromosomal transformation in cloud forests; these ecosystems, in addition
A. reigi and A. lugens. According to Gard- toseasonalforestsandevergreendryforests,
ner and Patton (1976), thomasomyine kar- have been previously recorded among the
yotypes are characterized by a generalized ecological conditions used by A. lugens
condition of diploid number of 42 or 44, in (Handley 1976; Sorianoet al. 1990).A. rei-
addition to a predominantly acrocentric giappears to be arelativelyuncommonspe-
autosomal complement. This generalized cies along its ecological ränge. Even though
condition is present in A. reigi and allows field data for päramos are insufficient, sam-
to consider it as a primitive form. This fact, plingeffortsof3724trap-nightsincloudfor-
together with the great proportion of two- ests, accumulated during inventories con-
armed elements shown by the karyotype of ducted by the authors, allowed to catch
A. lugens, are arguments to postulate this 27individuals of A. reigi that represented
last species as a derived form (Aguilera et 10.6% of total non-volant small mammals
al. 2000). Some complementary evidences trappedinthisecosystem(Oryzomysalbigu-
supporting this hypothesis are the differ- laris and Heteromys anomalus were the
ences in quantity and distribution of the dominant species). Collected specimens
constitutive heterochromatin: low and chro- have been found on the ground in densely
mosomal restricted in A. lugens vs abun- forested sites (beside logs, at the base of
dant and distributed in chromosomes of trees, in rocky places, along trails, or near
A. regi; the last pattern has been associated smallstreams) orin open areas (close to the