Gawinga aranaea
, new species
HOLOTYPE: QMF52173, isolated right m1 ( figs. 2A
View Fig
, 3A
View Fig
).
PARATYPE: QMF52174, isolated left m1 ( fig. 3B
View Fig
)
.
TYPE LOCALITY: Arachnea Ridge Site, Riversleigh World Heritage area, Lawn Hill National Park, northwestern Queensland, Australia.
REFERRED SPECIMENS:
QMF52175 ( fig. 3C
View Fig
) right m2
;
QMF52176 ( fig. 2D
View Fig
, 3I
View Fig
) left m4 from
Arachnea Ridge Site
.
QMF52177 ( fig. 2B
View Fig
, 3D
View Fig
) right m2
;
QMF52178 ( fig. 3E
View Fig
) left m2
;
QMF52179 ( fig. 3F
View Fig
) right m2
;
QMF52180 ( fig. 2C
View Fig
, 3G
View Fig
) right m3 from
Upper Site
.
QMF52181 ( fig. 3H
View Fig
) right m3 from
Wayne’s Wok Site
.
ETYMOLOGY: From the Latin aranea meaning ‘‘spider’’ or ‘‘spider’s web’’. In reference to the Riversleigh site, Arachnea Ridge.
DISTRIBUTION AND AGE: Riversleigh World Heritage Area, northwestern Queensland. Upper Site and Wayne’s Wok Site are interpreted to be part of Riversleigh’s System B strata ( Archer et al., 1995, 1997b; Creaser, 1997). Biocorrelation of the Riversleigh fossil assemblages, and of Upper Site in particular, suggests an early Miocene age for System B sites. No age has been determined for
Arachnea Ridge Site, but an early Miocene age is also possible given the presence of this new species.
DIAGNOSIS:
Gawinga aranaea
is characterized by a distinct, lower molar cusp morphology as follows: a reticulated occlusal surface of robust ridges, predominantly normal and lingual to the cristid obliqua; a hypoconid base that is enlarged posterobuccally; an anteriorly placed protoconid with respect to the metaconid on posterior molars; and a bisected posthypocristid on m1. The lower molars of
G. aranaea
are narrower and longer than in most extinct pseudocheirids, with the exception of
Marlu kutjamarpensis Woodburne et al., 1987
,
Pildra magnus Pledge, 1987
, and all species of
Pseudokoala
. It differs from known species of the other extinct genera by having a shorter, weaker, and more posteriorly oriented m1 buccal protocristid; by having a large cuspate protostylid; and a larger entostylid and ridge (entostylid completely absent in species of
Marlu
and
Pseudokoala
). Posterior molars also exhibit a prominent metaconid ridge and an elongate preentocristid that is transversely buttressed at its anterior end.
G. aranaea
differs further from
Paljara spp.
in the following features: m1 anterobuccal cingulum reduced; m1 paraconid smaller; protoconid on posterior molars buccally enlarged; metastylid progressively more complex along tooth row; narrower notch between preentocristid and metastylid; entostylid ridge forms a continuous crest with hypoconulid; larger hypoconulid on posterior molars; more lengthwise orientation of lingual cusps, particularly entoconid; wider buccal cusp angles; buccal cusp apices less lingually curved; shallower trigonid and talonid basins. Features shared with species of
Paljara
include: m2 longer than m1; reduced or absent anterior margins between paraconid and paracristid; paraconid on posterior molars positioned on lengthwise axis; elongate, blad- ed metacristids; equidistant positioning of the entostylid ridge between posthypocristid and entoconid; and lack of buccal protostylid or cingulum on posterior molars.
G. aranaea
differs further from
Pildra spp.
by the following features: stronger and broad- er anterior cingula (except
P. magnus
); anterior margins on posterior molars reduced or absent; m1 paraconid extended further anteriorly; paraconid on posterior molars positioned much closer to longitudinal axis; m1 metaconid relatively lower cusped; wider distance between apices of m1 metaconid and protoconid; narrower notch between metastylid and preentocristid; preentocristid less steep and more bladed; entoconid less conical; entostylid ridge forms a continuous crest with the hypoconulid which is separate from the postentocristid; larger hypoconulid. Features shared with species of
Pildra
include: m2 longer than m1; presence of a lingual rib extending from the m1 paraconid; lingual enlargement of the protoconid on posterior molars; progressively more complex metastylids along the tooth row; similar orientation of the posthypocristids on m1–2.
G. aranaea
differs further from
Marlu
and
Pseudokoala spp.
by the following features: stronger anterobuccal cingula; larger m1 paraconid; m1 protoconid more lingually positioned; m1 metaconid relatively larger and separated from protoconid by a deeper notch; greater distance between apices of m1 metaconid and protoconid; metastylids progressively more complex along the tooth row; larger, more distinct hypoconulid.
G. aranaea
differs further from all species of
Marlu
and
Pseudokoala
, except
M. praecursor Woodburne et al., 1987
, in the absence of an overlapping or joined metastylid and preentocristid.
G. aranaea
also differs from species of
Pseudokoala
in having relatively conical lingual cusps, with steeper cristids; shorter postprotocristid on posterior molars; posthypocristid extending further lingually and absence of a buccal protostylid or cingulum on posterior molars (except
P. curramulkensis
, originally described as
Corracheirus curramulkensis Pledge, 1992
). Features shared with
Marlu
and
Pseudokoala species
include: distinct anterolingual cingula; and broad buccal cusp angles.
G. aranaea
also shares with
Marlu
a longer m2 than m1.
In comparison with extant taxa,
G. aranaea
is smaller than all known species except
Pseudochirulus mayeri Rothschild and Dollman, 1933
View in CoL
, and
P. canescens Waterhouse, 1846
View in CoL
, and is very similar in size to
Petauroides ayamaruensis Aplin et al., 1999
. It also differs from extant taxa (species of
Pseudocheirus
View in CoL
,
Pseudochirulus
View in CoL
,
Petropseudes
View in CoL
,
Pseudochirops
View in CoL
,
Petauroides
View in CoL
, and
Hemibelideus
View in CoL
) as follows: m1 shorter than m2 (except
Petropseudes
View in CoL
); m1 precristid of the protostylid joins anterior end of the anterobuccal cingulum; m1 postcristid of the protostylid welldefined and shelflike, terminating at the cristid obliqua; distinct and strong metaconid ridge present on posterior molars; metastylid progressively more complex along the tooth row; metastylid and preentocristid do not overlap or join; posthypocristid more obliquely oriented.
G. aranaea
differs further from species of
Pseudochirops
View in CoL
and
Petropseudes
View in CoL
as follows: stronger anterior cingula (anterior cingula absent in
Pseudochirops cupreus Thomas, 1897
View in CoL
, and
Petropseudes dahli Collett, 1895
View in CoL
); anterobuccal cingulum present on posterior molars; m1 buccal protocristid shorter and weaker; flat lingual face of metastylid; hypoconulid relatively larger and more distinct from postentocristid and posthypocristid; buccal cusp apices less lingually curved; buccal protostylid or cingulum on posterior molars absent.
G. aranaea
differs further from
Pseudochirops spp.
as follows: flat lingual face on m1 protoconid; greater distance between apices of m1 metaconid and protoconid (except
P. corinna
e Thomas, 1897); m1 premetacristid not linear with very weak postprotocristid; anterior protocristid on posterior molars reduced or absent; larger entostylid and ridge, forming a continuous crest to the hypoconulid apex; entostylid ridge equidistant from entoconid and posthypocristid (except
P. archeri Collett, 1884
View in CoL
, and
P. winteri Mackness and Archer, 2001
); wider hypoconid cusp angle.
G. aranaea
differs further from
Petropseudes dahli
View in CoL
as follows: m1 metaconid much larger and separated from protoconid by a deeper notch; m1 cristid obliqua connects with metaconid; much shorter postprotocristid on posterior molars; entoconid more conical; entostylid present; less compressed lingual cristids. Features shared with
Pseudochirops
View in CoL
and
Petropseudes species
include: lingual rib extending from m1 paraconid and a cuspate protostylid on m1. It also shares with species of
Pseudochirops
View in CoL
an m1 protostylid basin.
With the exception of
Pseudocheirus stirtoni
and
P. marshalli ( Turnbull and Lundelius, 1970)
, which are compared alongside species of
Petauroides
View in CoL
and
Hemibelideus
View in CoL
,
G. aranaea
differs further from
Pseudocheirus spp.
as follows: stronger and broader anterior cingula; anterior margins of posterior molars reduced or absent; paraconid on posterior molars positioned much closer to longitudinal axis; greater distance between apices of m1 protostylid and protoconid; m1 metaconid relatively larger and separated from protoconid by a deeper notch; premetacristid on m1 does not align linearly with the very weak postprotocristid; wider protoconid cusp angles on posterior molars; protoconid on posterior molars more lingually swollen, forming a slight anterior protocristid in some specimens; much shorter postprotocristid on posterior molars that does not unite with the metastylid; entostylid present; hypoconulid on m1–2 is not ribbed posterolingually, and is perpendicular to hypoconulid cristids; cristid obliqua terminates at same height as postprotocristid; lingual cristids on posterior molars less steep; buccal cusps less lingually curved; shallower trigonid and talonid basins. Features shared with species of
Pseudocheirus
View in CoL
include: lingual rib extending from m1 paraconid; a cuspate protostylid on m1; and absence of a buccal protostylid or cingulum on posterior molars.
G. aranaea
differs further from
Pseudochirulus spp.
as follows: anterior margins of posterior molars reduced or absent; m1 paraconid smaller and less conical; paraconid on posterior molars positioned much closer to longitudinal axis; m1 metaconid larger and separated from protoconid by a deeper notch; shorter, weaker m1 buccal protocristid; anterior protocristid on posterior molars absent or very reduced; entostylid and ridge present; hypoconulid on m1–2 is not ribbed or curved on the posterolingual surface, and cristids are oriented lengthwise; posthypocristid less curved at lingual termination; lingual cusps less conical (except m1 protoconid); buccal cusp cristids higher crested (except anterior protocristid); cristids are less steep; shallower trigonid and talonid basins. Features shared with species of
Pseudochirulus
include: broad, distinct anterior cingula and a cuspate protostylid on m1.
G. aranaea
differs further from
Pseudocheirus stirtoni
,
P. marshalli
and
Petauroides
View in CoL
and
Hemibelideus spp.
as follows: anterior margins of posterior molars reduced or absent; paraconid on posterior molars positioned much closer to longitudinal axis; m1 metaconid is a more distinct, independent cuspid (except
P. marshalli
and
P. ayamaruensis
); shorter, weaker m1 postprotocristid; much shorter postprotocristid on posterior molars; entoconid buccally compressed; larger entostylid and much stronger, continuous entostylid ridge on all molars (
H. lemuroides Collett, 1884
View in CoL
, has no entostylid or ridge); hypoconulid more peaked and distinct and lacks a ribbed or curved posterolingual surface; wider hypoconid angles; cristid obliqua terminates at same height as postprotocristid (except
P. ayamaruensis
); buccal cusp apices less curved lingually; cristid obliqua and paracristid higher crested; buccal protostylid or cingulum on posterior molars absent; shallower trigonid and talonid basins. It differs further from species of
Hemibelideus
View in CoL
as follows: buccally enlarged m1 protostylid; m1 paraconid less conical, and independent of paracristid (
P. ayamaruensis
also differs in this feature). Features shared with
P. stirtoni
,
P. marshalli
and species of
Petauroides
View in CoL
and
Hemibelideus
View in CoL
include: distinct anterolingual cingula; an enlarged cuspate protostylid on
TABLE 1 Length (L), Anterior Width (AW), and Posterior Width (PW) of
Gawinga aranaea
Measurements in millimeters.
m1; and flat lingual surfaces of metaconid/ protoconid and entoconid on m1–2.