SCIOPHANES, Díaz-Nieto & Jansa & Voss, 2016
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publication ID |
https://doi.org/ 10.1111/zoj.12343 |
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persistent identifier |
https://treatment.plazi.org/id/934FA525-FFDE-FF80-28B6-76DB1DC7AA4C |
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treatment provided by |
Marcus |
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scientific name |
SCIOPHANES |
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subgen. nov. |
SCIOPHANES SUBGEN. NOV.
Type species
Marmosops parvidens ( Tate, 1931) View in CoL .
Included taxa
We refer 12 nominal taxa to Sciophanes : bishopi Pine, 1981 ; carri Allen & Chapman, 1897; cracens Handley and Gordon, 1979 ; fuscatus Thomas, 1896 ; handleyi Pine, 1981 ; invictus Goldman, 1912 ; juninensis Tate, 1931 ; ojastii García et al., 2014 ; pakaraimae Voss et al., 2013 ; parvidens Tate, 1931 ; pinheiroi Pine, 1981 ; and woodalli Pine, 1981.
The nominal taxon perfuscus Thomas, 1924, was previously regarded as a synonym or subspecies of Marmosops fuscatus (e.g. by Tate, 1933; Cabrera, 1958; Gardner & Creighton, 2008), but our examination of the holotype suggests that this name is a junior synonym of Marmosops caucae (a member of the nominotypical subgenus, see below).
Diagnosis
Specimens that we refer to the subgenus Sciophanes can be distinguished morphologically from those that we refer to the nominotypical subgenus by their shared possession of an anteroposteriorly elongated subsquamosal foramen, accessory upper canine cusps, and two antebrachial vibrissae.
Of these distinguishing traits, the most consistently useful is the morphology of the subsquamosal foramen, a lateral opening in the squamosal bone that exposes the underlying petrosal just dorsal to the ear region ( Fig. 6 View Figure 6 ). In Sciophanes , the subsquamosal foramen is anteroposteriorly elongated, revealing not only the sulcus for the prootic sinus, but also a substantial strip of the relatively featureless lateral surface of the pars canalicularis behind that groove. [See Wible (2003) for a detailed description and illustrations of didelphid petrosal morphology.] By contrast, the subsquamosal foramen in the nominotypical subgenus is shorter and does not extend posteriorly much behind the sulcus for the prootic sinus. These contrasting morphologies, first described by Díaz-N et al. (2011) to distinguish Colombian exemplars of these clades, appear to provide complete discrimination amongst the tissue vouchers and examined type material that we refer to Sciophanes on the one hand and to the subgenus Marmosops on the other.
All species of Sciophanes also have accessory upper canine (C1) cusps, but there is taxonomic variation in the expression of this trait. In members of Clade A – e.g. Marmosops (S.) handleyi (see Díaz-N et al., 2011) – the accessory cusps of C1 are sexually dimorphic, usually occurring only in females. By contrast, both sexes seem to have upper-canine accessory cusps in species that belong to Clade C, in which C1 is a short and strikingly premolariform tooth ( Voss et al., 2001: fig. 23). Although the sample sizes are too small for several taxa in Clade B to be assessed for sexual dimorphism, both sexes of some species – e.g. M. (S.) bishopi – and at least some females in others have either one or two C1 accessory cusps. [ Voss et al. (2001: 48) described Marmosa (Sciophanes) juninensis as lacking distinct C1 accessory cusps, but their material consisted of mature adults with worn teeth. Subsequently examined specimens, amongst them LSU 25902 (a juvenile male) and two young adult females described by ( Peralta & Pacheco, 2014), all have distinct posterior accessory cusps on C1.] Based on the material that we examined, the upper canine lacks distinct accessory cusps in all species of the nominotypical subgenus (in which this tooth is consistently unicuspid).
In addition to these craniodental traits, all species of Sciophanes have two antebrachial vibrissae, long tactile hairs on the dorsolateral surface of the forearm, by contrast with the single antebrachial vibrissa normally found in most species of the subgenus Marmosops (Díaz-N et al., 2011: fig. 5). The only exceptional species of the latter clade known to us is Marmosops (Marmosops) ocellatus , most examined specimens of which appear to have two antebrachial vibrissae.
Remarks
Most of the nominal taxa that comprise clade A are unrevised. The unique exception is handleyi , recently redescribed by Díaz-N et al. (2011), who also documented its apparently restricted distribution in the Cordillera Central of northern Colombia; amongst other material unambiguously referable to this species, the validity of which is clearly supported by our analyses, we sequenced a paratype (FMNH 69823). Our unique sequence of invictus , one of only two species of Marmosops known to occur in Panama, was obtained from a specimen that we compared directly with Goldman’s (1912) type material, which it closely resembles in all relevant external and craniodental details; the very large CYTB distances between this taxon and all other members of clade A (10.6–17.5%, uncorrected) are obviously consistent with its currently accepted status as a valid species. Although we sequenced both the holotype (USNM 418503) and a paratype (USNM 442719) of cracens from the Caribbean coast of northern Venezuela, we provisionally treat this name as a junior synonym of fuscatus based on close morphological and sequence similarity with topotypical material of the latter taxon (e.g. BMNH 1903.1.5.2, from the Mérida Andes of western Venezuela). We use carri (previously considered to be a synonym of fuscatus ; e.g. by Gardner & Creighton, 2008) for sequences that we obtained from Trinidad (the type locality of carri) and from the adjacent Venezuelan mainland. The CYTB sequences that we refer to fuscatus (including cracens ) and carri are substantially divergent (4.9%, uncorrected), and relevant voucher material is unambiguously distinguishable by dental measurements, so we provisionally regard these taxa as valid species.
Clade B is also unrevised and contains both currently recognized species and putative species that lack available names. Our unique BRCA1 sequence of juninensis was obtained from a specimen collected near the Peruvian type locality (in Junín department), and which we compared directly with the holotype (AMNH 63864). We have not personally examined type material of ojastii , but the sequence that we associate with this name was obtained from a specimen collected near the type locality (in north-central Venezuela), and which conforms to the morphological diagnosis provided by García et al. (2014). Large CYTB differences (7.7–10.2%, uncorrected) between ojastii and other nominal taxa in clade B seem consistent with its proposed status as a valid species. Sister to ojastii is a complex of putative species that are morphologically indistinguishable from M. bishopi . These taxonomically problematic lineages differ from one another by 3.5 to 11.3% in mean uncorrected CYTB sequence comparisons ( Table S3) and, in default of available names, we distinguish them by alphabetical labels. Marmosops bishopi is based on a specimen from central Brazil that closely resembles voucher material of ‘ bishopi E’, the haplogroup to which the epithet might apply if it were to be used in a formally restricted sense. The remaining terminals belonging to clade B are two unnamed haplogroups from northern Colombia, one from either side of the Río Magdalena – an important zoogeographical barrier ( Chapman, 1917; Gutiérrez-Pinto et al., 2012) – that differ by about 5.9% at the cytochrome b locus; because they are also morphologically diagnosable (J. F. Díaz- Nieto, R. S. Voss & S. A. Jansa, unpubl. data), we regard them as valid species.
Clade C has received some revisionary attention, most recently from Voss et al. (2013), who analysed morphological data and CYTB sequences to establish pakaraimae , parvidens , and pinheiroi as valid species. Our samples from this clade are identical to theirs, and include several sequences from the type series of pakaraimae . Identifications of sequences that we assign to parvidens and pinheiroi are supported by direct comparisons of voucher specimens with type material based on external and craniodental characters described by Voss et al. (2001). Indeed, the only noteworthy issue here concerns the status of woodalli, currently treated as a subspecies ( Pine, 1981) or junior synonym ( Gardner & Creighton, 2008) of pinheiroi . The CYTB clade that we associate with woodalli, consisting of sequences from two specimens (including a paratype, USNM 545543) collected south of the Amazon, is only 3.9% divergent from typical pinheiroi (from north of the Amazon), and we are not aware of any consistent phenotypic character by which these nominal taxa can be distinguished. We are, therefore, inclined to regard pinheiroi and woodalli as conspecific.
Etymology
From the ancient Greek (σκιοφανη´ς) for shadowy or phantom-like, in reference to the elusive habits of these small forest creatures.
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