2004 
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: 
CUTTRASS Beetrtnagy cine 



VOSS ET AL.: BOLIVIAN MARMOSOPS 11 

Fig. 4. Dorsal views of the interorbital region in Marmosa murina (A, AMNH 267368), Marmosops 
noctivagus (B, AMNH 262402), and Gracilinanus agilis (C, MVZ 197439) illustrating generic differ- 
ences in the development of postorbital processes. Distinct postorbital processes of the frontals (ppf) 
are normally present in fully adult specimens of most Marmosa species, but they are usually absent in 
Marmosops and Gracilinanus (indistinct processes are sometimes developed in old adults). Supraorbital 
beads (b), consisting of upturned dorsally-grooved ridges, are present in some but not all species of 
Marmosops. Scale bars equal 5 mm. 
of morphological characters, Marmosops ap- 
pears to be a natural group based on recent 
phylogenetic analyses in which generic 
monophyly was tested rather than assumed 
(Jansa and Voss, 2000; Voss and Jansa, 
2003). The most taxonomically complete 
analysis to date (Voss and Jansa, 2003) in- 
cluded only five species of Marmosops, but 
among these were members of the diminu- 
tive M. parvidens complex as well as large 
Amazonian and southeastern Brazilian 
forms; generic monophyly was supported in 
separate parsimony analyses of both non- 
molecular (morphological + karyotypic) 
characters and sequences from exon | of the 
nuclear gene encoding the Interphotoreceptor 
Retinoid Binding Protein (IRBP), in a like- 
lihood analysis of the IRBP data, and in a 
parsimony analysis of a combined-data (non- 
molecular + IRBP) supermatrix. The only 
discrepant result concerning generic mono- 
phyly, Kirsch and Palma’s (1995) report that 
Gracilinanus agilis and Marmosops doro- 
thea are almost indistinguishable by thermal 
elution of scnDNA heteroduplexes, is now 
known to be an artifact of specimen mis- 
identification (see Voss and Jansa, 2003: 57). 
Several phylogenetic analyses of molecu- 
lar data (e.g., Kirsch and Palma, 1995; Jansa 
and Voss, 2000; Voss and Jansa, 2003) sug- 
gest that Marmosops belongs to a didelphine 
clade that also includes Gracilinanus, Les- 
todelphys, and Thylamys. The recently de- 
scribed genus Chacodelphys may also belong 
to this group (Voss et al., 2004). Although 
Patton et al. (1996) recovered Marmosops as 
the sister taxon of Caluromys, the cyto- 
chrome-b sequences they analyzed appear to 
be substitution-saturated at this level of tax- 
onomic comparison (Jansa and Voss, 2000: 
fig. 12), and the relationship in question 
(Marmosops + Caluromys) had only trivial 
bootstrap support in their parsimony results. 
Palma and Spotorno’s (1999) report of a sis- 
ter-group relationship between Marmosops 
and Metachirus (supported by very large 
bootstrap values in their neighbor-joining 
and parsimony trees) is an unexplained 
anomaly that is not consistent with any other 
analytic results or character data of which we 
are aware. 
Marmosops creightoni, new species 
Figure 9 
HOLOTYPE: An adult male specimen in the 
Coleccion Boliviana de Fauna (CBF 6552) 
collected by Eric Yensen (original number 
1705) on 5 August 1999 near the Saynani 
hydroelectric generating station (ca. 16°07'S, 
