Aritana's Brown Four-eyed Opossum

description

3.4 Description 3.4.1 External morphology Combined length of adult head and body ca. 230 mm on average (ranging 243 – 275 mm); adult weight ca. 380 g. Midrostral fur cream coloured with apical portion dark brown (most of the cream-coloured hairs have black tips, but there are also completely blackened or cream hairs in lesser quantities, somewhat like the dorsal coat). Dark median rostral stripe absent or inconspicuous. Dark circumocular mask present (blackened), extending posteriorly to the base of the ear, continuous with the coronal fur. Narrow dark brown dorsal line starting at the coronal spot and extending to the end of the nape. Throat gland present in adult males. Small pure cream supraocular spots present, usually in the shape of an inverted triangle, varying in size. Pure cream-coloured cheeks, of the same colour as the supraocular spots. Completely brown ears. Presence of small amounts of rust hair behind the base of the ears. General colouration light brown speckled with gold. Dorsal colour pale brown, with grey-based hairs, cream stripe over most of its length and short blackish apex, giving the back a golden speckled appearance. Dorsal hairs usually do not exceed 10 m

A new species of jupati, genus Metachirus Burmeister 1854 (Didelphimorphia, Didelphidae) for the Brazilian Amazon

diagnosis

Diagnosis: M. aritanai new species is characterized by the combination of the following characters: general colouration light brown with speckles of gold on the back; small amount of rust hair behind the ears; supra-ocular spots of cream colour; cheeks with the same colouration as supra-ocular spots; brown and gold-speckled face; absence of median stripe on the rostrum; the presence of a narrow, blackened dorsal line at the top of the head, usually extending to the nape of the neck; clear ventral surface, usually pure cream, wide interorbital region (average = 12.12 mm) and with incipient ridges; rounded and inflated cranial cavity, with large maxillopalatine (average = 24.68 mm) and fenestrae; small entoconids; absent or incipient temporal crest. Figures 5 – 7 show the mentioned characters, except for the morphology of the entoconid, which is similar to that of M. nudicaudatus and may be seen in Figure 15, page 46 in Voss et al. (2019).

A new species of jupati, genus Metachirus Burmeister 1854 (Didelphimorphia, Didelphidae) for the Brazilian Amazon

discussion

3.4.3 Morphological variation We did not observe differences in the external morphology of males and females within any of the considered age groups (young, sub-adult or adult). However, there were significant age-related morphological differences. Young and sub-adult individuals had a general greyish and darker colour than adult individuals. Yet, sub-adults also exhibit some diagnostic characters of M. aritanai new species, such as cream supra-ocular spots and cheeks of the same colour, absence of median stripe on the rostrum and cream-pure ventral surface (Table 5). 3.4.4 Comparisons M. aritanai new species differs from the nominal form, M. nudicaudatus (sensu Voss et al. 2019 and present study) and from M. myosuros from the Atlantic Forest (sensu present study) by their dorsal colouring (light brown speckled with gold in M. aritanai vs. brown speckled with black and light orange in M. nudicaudatus, vs. brown-orange to light brown in M. myosuros); ventral surface colouring (purecream in M. aritanai vs. yellow-cream in M. nudicaudatus, vs. yellowish hues in M. myosuros); colouring of the sides of the body (similar to the dorsum but slightly lighter in M. aritanai vs. orange-brown,

A new species of jupati, genus Metachirus Burmeister 1854 (Didelphimorphia, Didelphidae) for the Brazilian Amazon

distribution

Distribution: M. aritanai new species is restricted to the Xingu-Tocantins interfluve, the endemism center Xingu sensu Silva et al. (2005). As far as we know M. aritanai new species is endemic to this biogeographic region (Figure 1). The species is bounded to the north by the Amazon River, to the west by the Xingu River and to the east by the Tocantins River. The southern boundary cannot yet be clearly defined. According to the consensus topology and times of divergence presented in this study, a sister species of M. aritanai new species, M. nudicaudatus, occurs north of the Amazon River (Figures 2 and 3).

A new species of jupati, genus Metachirus Burmeister 1854 (Didelphimorphia, Didelphidae) for the Brazilian Amazon