NEOSCIUROMYS AFRICANUS STROMER, 1922
Synonym:
Phthinylla fracta Hopwood, 1929
This species ( Fig. 4D) has been described on the basis of material from the Lower Miocene of Langental and Plant 4 borehole, south of Lüderitz Bay ( Namibia). Stromer (1922,1924: 263; 1926: 135–136) described and illustrated as
N. africanus
two mandibular fragments with p4-m2 and a fragmentary left maxilla. Interestingly enough, the latter specimen is actually a right mandibular fragment with m2-m3 of the bathyergoidid
Bathyergoides neotertiarius
and the abnormally narrow M1 figured by Stromer (1926: pl. 42, fig. 24) as cf.
Phiomys andrewsi
belongs in fact to
N. africanus
.
Neosciuromys africanus
has been synonymized with
Paraphiomys pigotti
by Lavocat (1973). Hendey (1978: 32) mentioned the discovery of two incomplete mandibles (AD 629 and AD 1049) in the basal Middle Miocene of Arrisdrift ( Namibia). According to him ‘they are indistinguishable from that described by Stromer (1922, 1926) as
Neosciuromys africanus
’, but he attributed them to
P. pigotti
, following Lavocat (1973). However, Patterson & Wood (1982: 520) considered
N. africanus
to be a taxon distinct from
P. pigotti
, given that
Neosciuromys
has higher crowned teeth and has lower cheek teeth with three transverse crests without a trace of the metalophulid II. Like Flynn et al. (1983), Winkler (1992), Flynn & Winkler (1994), and Mein et al. (2000), we follow Patterson & Wood (1982) in accepting
N. africanus
as a valid species.
Neosciuromys africanus
mainly differs from
P. pigotti
,
P. hopwoodi
,
Paraphiomys
sp. nov. from Saudi Arabia,
P. occidentalis
,
Epiphiomys coryndoni
and
Sacaresia moyaeponsi
in lacking the metalophulid II on the lower molars.
Neosciuromys africanus
is distinct from
Gaudeamus aegyptius
, among other characters, in being larger and higher-crowned and in having the hypolophid much less obliquely directed.
Neosciuromys africanus
differs from
Apodecter stromeri
and
P. renelavocati
sp. nov. in being much larger and higher-crowned and in having the m2 much larger than the m1.
Neosciuromys africanus
differs from
Paraulacodus johanesi
,
Paraulacodus indicus
,
P. orangeus
,
P. roessneri
and
P. australis
mainly in its larger size and greater hypsodonty.
Neosciuromys africanus
differs from
P. shipmani
and from
P. afarensis
in being larger, in having greater hypsodonty, and in its hypolophid being anteriorly directed.
The holotype and unique specimen of
Phthinylla fracta
(AMNH 22539) is a maxilla briefly described and poorly illustrated by Hopwood (1929: 4, fig. 3). It comes from an unspecified locality situated south of Lüderitz Bay ( Namibia), (see map of Namibian Miocene fossil sites in Hendey, 1978: Fig. 1). According to M. Pickford (pers. comm.), the only fossils in the AMNH are from Langental on the basis of preservation. It is regarded as Early Miocene in age ( Hendey, 1978).
Lavocat (1973: 39) considered
Phthinylla fracta
as a junior synonym of
P. pigotti
, which was acknowledged by Hendey (1978). Flynn & Winkler (1994: 230) and Winkler (1994: 181) suggest that
Phthinylla fracta
represents the upper dentition of
Neosciuromys
. In effect, the type maxilla of
Phthinylla fracta
and the type mandible of
N. africanus
match: they are com- mensurate and show an equally strong hypsodonty (R. López Antoñanzas, S. Sen & P. Mein, pers. observ.). These two taxa have close (if not identical) stratigraphic and geographical origins and, interestingly enough, new excavations at Elisabethfeld carried out by one of us (P.M.) have resulted in the discovery of
Phthinylla
–like maxillary teeth along with
Neosciuromys
-like mandibles. The recurrence of this association in addition to the intrinsic correspondence between
Phthinylla fracta
and
N. africanus
strongly suggest that the former taxon is a junior synonym of the latter. They should definitely be considered as such until evidence to the contrary comes to light.
