A Cretaceous mammal from Tanzania

Abstract

We report here the discovery of a Cretaceous mammal from the "Red Sandstone Group" of southwestern Tanzania. This specimen is one of only a very few Cretaceous mammals known from Gondwana in general and Africa in particular. The specimen consists of a short, deep left dentary that bore a large, procumbent central incisor, and five single-rooted, hypsodont check-teeth. The specimen is very tentatively identified as a sudamericid, and thus may represent the first African record of an enigmatic clade of mammals, the Gondwanatheria, which is otherwise known from the Late Cretaceous and Paleogene of several other Gondwanan landmasses. Unfortunately, the precise age of the specimen could not be determined. If it is pre-Campanian and if its identity as a sudamercid is corroborated through subsequent discoveries, it represents the earliest known gondwanatherian. If the specimen is from the Campanian or Maastrichtian, and again assuming its identification is correct, it has the potential to refute a recently formulated biogeographic hypothesis predicting the absence of certain terrestrial and freshwater vertebrate taxa, including gondwanatherians, in Africa (i.e., those that evolved elsewhere on Gondwana after Africa became an isolated landmass).

Full text

A Cretaceous mammal from Tanzania
DAVID W. KRAUSE, MICHAEL D. GOTTFRIED, PATRICK M. O’CONNOR,
and ERIC M. ROBERTS
Krause, D.W., Gottfried, M.D., O’Connor, P.M., and Roberts, E.M. 2003. A Cretaceous mammal from Tanzania. Acta
Palaeontologica Polonica 48 (3): 321–330.
We report here the discovery of a Cretaceous mammal from the “Red Sandstone Group” of southwestern Tanzania. This
specimen is one of only a very few Cretaceous mammals known from Gondwana in general and Africa in particular. The
specimen consists of a short, deep left dentary that bore a large, procumbent central incisor, and five single−rooted,
hypsodont cheek−teeth. The specimen is very tentatively identified as a sudamericid, and thus may represent the first Afri−
can record of an enigmatic clade of mammals, the Gondwanatheria, which is otherwise known from the Late Cretaceous
and Paleogene of several other Gondwanan landmasses. Unfortunately, the precise age of the specimen could not be de−
termined. If it is pre−Campanian and if its identity as a sudamercid is corroborated through subsequent discoveries, it rep−
resents the earliest known gondwanatherian. If the specimen is from the Campanian or Maastrichtian, and again assuming
its identification is correct, it has the potential to refute a recently formulated biogeographic hypothesis predicting the ab−
sence of certain terrestrial and freshwater vertebrate taxa, including gondwanatherians, in Africa (i.e., those that evolved
elsewhere on Gondwana after Africa became an isolated landmass).
Key words: Mammalia, Gondwanatheria, Cretaceous, Gondwana, Africa, Tanzania.
David W. Krause [David.Krause@sunysb.edu], Department of Anatomical Sciences, Stony Brook University, Stony
Brook, New York 11794−8081, USA;
Michael D. Gottfried [gottfrie@msu.edu], Michigan State University Museum, East Lansing, Michigan 48824−1045, USA;
Patrick M. O’Connor [pmoconno@ic.sunysb.edu], Department of Anatomical Sciences, Stony Brook University, Stony
Brook, New York 11794−8081, USA; Current address: Department of Biomedical Sciences, Collegeof Osteopathic Medi−
cine, Ohio University, Athens, Ohio 45701, USA;
Eric M. Roberts [eroberts@mines.utah.edu], Department of Geology and Geophysics, University of Utah, Salt Lake City,
Utah 84112, USA.
Introduction
Controversy persists and, indeed, continues to grow as to
whether placental mammals arose before or after the Creta−
ceous/Tertiary boundary, and whether their ancestry and
earliest history is Laurasian or Gondwanan (e.g., Hedges et
al. 1996; Springer 1997; Springer et al. 1997; Kumar and
Hedges 1998; Stanhope et al. 1998; Archibald 1999;
Benton 1999a, b; Easteal 1999a, b; Foote et al. 1999a, b;
Hedges and Kumar 1999; Rich, Vickers−Rich, and Flannery
1999; Eizirik et al. 2001; Madsen et al. 2001; Murphy et al.
2001; Ji et al. 2002, Waddell et al. 2001; Yang et al. 2003).
One camp (e.g., Springer et al. 1997; Stanhope et al., 1998;
Eizirik et al. 2001; Murphy et al. 2001; Waddell et al. 2001)
has predicted that the most recent common ancestor of
crown−group eutherians will turn out to be Gondwanan, and
that members of the primitive placental clade Afrotheria
(elephants, sirenians, hyraxes, golden moles, aardvarks,
and elephant shrews) were present in Africa before the end
of the Cretaceous. A mammalian record from the Creta−
ceous, and especially the Late Cretaceous, of Africa is
clearly essential to directly test the competing hypotheses
underpinning this controversy.
Unfortunately, while Laurasian Cretaceous mammals are
relatively well−known (e.g., Clemens et al. 1979; Kielan−
Jaworowska 1992; Cifelli 2001; Luo et al. 2002), the Gond−
wanan record, particularly that of Africa, suffers from an al−
most complete lack of fossils. Early Cretaceous Gondwanan
mammals are known from Argentina (Bonaparte and
Rougier 1987; Rougier et al. 1992; Hopson and Rougier
1993), Australia (Archer et al. 1985; Rich et al. 1989, 1997,
1998, 1999, 2001; Flannery et al. 1995), Cameroon (Brunet
et al. 1988, 1990; Jacobs et al. 1988), Morocco (Sigogneau−
Russell et al. 1998, and references therein), and perhaps
South Africa (C. Forster, personal communication in Rich et
al. 1997). Late Cretaceous Gondwanan mammals are known
from South America (Marshall and Sempere 1993, and refer−
ences therein; Pascual et al. 2000; Rougier et al. 2000, 2001),
India (Prasad and Sahni 1988; Prasad et al. 1994; Prasad and
Godinot 1994; Das Sarma et al. 1995; Anantharaman and
Das Sarma 1997; Krause et al. 1997), Madagascar (Krause et
al. 1994, 1997; Krause and Grine 1996; Krause 2001, 2002,
in press), and perhaps Libya (Nessov et al. 1998). A tooth
from the Late Cretaceous of Egypt initially identified as
mammalian (Stromer and Weiler 1930) was later shown to
be from the pycnodontid fish Anomoeodus (Stromer 1936).
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Acta Palaeontol. Pol. 48 (3): 321–330, 2003

Other than the Libyan occurrence, based on an isolated cau−
dal vertebra from a Cenomanian horizon (see Rage and
Cappetta 2002), there are no previously known Late Creta−
ceous mammals from the African mainland, an interval of
some 35 million years.
Here we report the discovery of a mammalian fossil from
the Cretaceous of sub−Saharan Africa. The specimen is a par−
tial lower jaw, recovered from the “Red Sandstone Group” in
the Mbeya District of southwestern Tanzania (Fig. 1) by a re−
connaissance expedition led by MDG and PMO in July 2002.
The only other Mesozoic mammalian fossils recovered from
Tanzania include isolated jaws and teeth of haramiyids,
triconodonts, and eupantotheres from the Upper Jurassic
(Kimmeridgian–Tithonian) Tendaguru Series of southeast−
ern Tanzania (Branca 1916; Dietrich 1927; Heinrich 1991,
1998, 1999, 2001), taxa that are not closely related to the de−
rived taxon that the specimen described here represents.
Abbreviations.—Michigan State University, East Lansing
(MSU), National Museums of Tanzania, Dar Es Salam
(NMT).
Provenance
The lower jaw (NMT 02067) was collected from locality
TZ−07, situated at approximately 8° 56’ S, 33° 12’ E in the
Mbeya District of southwestern Tanzania (Fig. 1) (precise
locality coordinates are on file at the Michigan State Uni−
versity Museum). Locality TZ−07 exposes approximately
140 m of section of the “Red Sandstone Group” (Fig. 2).
The section is dominated by thick sequences of red−pink
sandstone, with trough and tabular cross−stratification as
well as planar stratification, along with minor dark red
mudstone lenses. The sediments at TZ−07 are here inter−
preted as representing deposition by axial, north−
west−trending braided fluvial systems, consistent with sedi−
ment accumulation in a half−graben rift valley setting. The
“Red Sandstone Group” at TZ−07 preserves a relatively
abundant and diverse vertebrate fauna (O’Connor et al. in
press), contrary to Westcott et al. (1991), who maintained
that the deposit was not richly fossiliferous. The fauna in−
cludes teleost fishes, turtles, crocodyliforms, titanosaurid?
sauropods (including an associated partial skeleton), non−
avian theropods, birds (a single limb element), and mam−
mals (the specimen reported here) (O’Connor et al. in
press). NMT 02067 was found in situ in a sandstone lens ap−
proximately one−fifth of the way up from the base of the
section at TZ−07 (Fig. 2); dinosaur (and other vertebrate) re−
mains were recovered below, lateral to, and above the
specimen, confirming that the mammal jaw is the same age
as the “Red Sandstone Group” dinosaurs.
The age of the “Red Sandstone Group”, originally
named by Spence (1954), is poorly constrained. A strato−
type section has not been described and the unit has not
been properly defined. Spence regarded it as Cretaceous,
based on lithostratigraphic relationships with the Malawi
Dinosaur Beds (Mwakasyunguti area, Karonga District),
which are Early Cretaceous, perhaps no younger than
Aptian (Colin and Jacobs 1990; Jacobs et al. 1990, 1992;
Gomani 1997), and which lie about 200 km to the southeast
(Fig. 1). Subsequent to Spence’s (1954) naming of the unit,
Harkin and Harpum (1957) reported the presence of “rep−
tile” bones in the “Red Sandstone Group”. Other workers
(Biyashev and Pentel’kov 1974; Pentel’kov and Voronov−
skii 1977) argued for a late Middle Jurassic age based on
molluscan and reptilian fossils, while still others (Westcott
et al. 1991; Morley et al. 1992; Damblon et al. 1998) as−
signed a Miocene age to the unit based on palynomorphs
and fossil wood.
These seemingly contradictory age assignments are rec−
oncilable, at least in part, based on our preliminary field in−
vestigations in 2002, which revealed the presence of two
presumably unconformable time−stratigraphic units in the
outcrop area explored—one containing dinosaurs and other
vertebrate remains that are indisputably Mesozoic, as at
TZ−07 where the mammal jaw was collected, and another
superficially similar unit, which crops out at a single local−
ity approximately 2 km south of TZ−07 and contains a Ter−
tiary (minimally post−Paleocene) fauna. Although direct
correlation of the two units was physically impossible, their
relative stratigraphic positions can be safely inferred based
322 ACTA PALAEONTOLOGICA POLONICA 48 (3), 2003
Fig. 1. Location of Locality TZ−07 in the Mbeya District of southwestern
Tanzania, which yielded the mammal jaw (NMT 02067) described here.
Also indicated is the location of productive vertebrate fossil localities in the
“Malawi Dinosaur Beds,” Mwakasynunguti area, Karonga District, Malawi
(Colin and Jacobs 1990; Jacobs et al. 1990, 1992; Gomani 1997).

on faunal assemblages and relationship of overlying beds
(Fig. 2).
We assign a Cretaceous age to the mammal jaw based on
its being found in the lower of these two units, and on the
overall fauna at TZ−07, which includes (probable titano−
saurid) sauropod and non−avian theropod dinosaurs, as well
as megaloolithid dinosaur eggshell (Gottfried et al. in
press). In addition, we recovered an osteoglossomorph tele−
ost fish scale at TZ−07 from exactly the same level as the
mammal jaw; osteoglossomorphs have a predominantly
(possibly entirely) Cretaceous and later fossil record (see
Arratia 1997). In its entirety, this fauna points to a Creta−
ceous age, which is also consistent with the fact that
gondwanatherians have only been found in Cretaceous and
younger sediments elsewhere.
Description
NMT 02067 is a heavily abraded partial left dentary (Figs.
3, 4). It lacks sufficient morphological information to allow
diagnosis of a new taxon. The nearly complete body of the
dentary is short and deep; the posterior aspect of the ramus
is broken away along a jagged, roughly vertical fracture
through the masseteric fossa, distal to the tooth row (Fig.
3A). Another fracture passes through the body of the denta−
ry obliquely, and is most evident in labial view (stippled in
Fig. 3A). This fracture, as revealed by X−ray radiography
(Fig. 4), passes inferiorly from the mesial border of the rim
of the alveolus for the first cheek−tooth, and posteriorly be−
tween the apices of the large roots of the central incisor and
the third cheek−tooth. Although all of the tooth crowns are
missing or incomplete, devoid of both enamel and cemen−
tum, the alveoli and dentine stumps indicate that there was a
large, procumbent, laterally compressed central incisor
mesially, and five cheek−teeth distally (assuming that all of
the cheek−teeth were single−rooted; see below). The incisor
is separated from the first cheek−tooth by a short diastema
(approximately 2.5 mm) (Fig. 3). A single, large mental fo−
ramen is situated on the labial aspect of the dentary inferior
to the diastema (Fig. 3A). The masseteric fossa (Fig. 3A)
was large and extended anteriorly to a position below the
mesial border of the fourth cheek−tooth. Although the
symphyseal surface is damaged and abraded, there is no in−
dication that the mandibular symphysis was fused. In lateral
view (Fig. 3A, B), the inferior margin of the dentary undu−
lates, being strongly convex mesially and concave distally,
with the deepest part of the body of the dentary (8.3 mm)
beneath the diastema, and the shallowest part (7.0 mm)
beneath the root of the third cheek−tooth.
The incisor is missing its extra−alveolar portion. Its root is
implanted at an angle of approximately 55 degrees relative to
the horizontal axis of the dentary and, as revealed radio−
graphically (Fig. 4), extends distally to a position below the
mesial edge of the root of the third cheek−tooth. The cross−
section of the incisor at the rim of the alveolus measures ap−
proximately 3.0 mm high and 2.1 mm wide.
The crowns of the two most mesial cheek−teeth are bro−
ken away although their roots are still embedded in the jaw.
The roots indicate that the first cheek−tooth was perhaps just
slightly smaller than the second; both, however, measure
approximately 1.5 mm in diameter. The third cheek−tooth is
large and curved (convex mesially, concave distally) and
was clearly the largest of the cheek−teeth. The crown of this
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KRAUSE ET AL.—TANZANIAN CRETACEOUS MAMMAL 323
Fig. 2. Measured stratigraphic section of the “Red Sandstone Group” in the
Mbeya District of southwestern Tanzania. Section demonstrates level of
Locality TZ−07, which yielded the mammal dentary (NMT 02067) de−
scribed in this report as well as dinosaurs, which were also found above and
below this level. Also indicated is the stratigraphic horizon of an area some
2 km to the south that yielded Tertiary vertebrate fossils.

tooth is very tall and is represented by a dentine stump,
measuring 2.3 mm mesiodistally and 1.9 mm labio−
lingually, that projects superodistally far out of its alveolus,
indicating that it was hypsodont. The tooth was firmly an−
chored in its alveolus by a large, parallel−sided, posteriorly
curving root (Fig. 4). The apex of the root terminates inferi−
orly approximately three−fourths of the way through the
depth of the dentary. The crowns of the fourth and fifth
cheek−teeth are represented by much smaller stumps, which
also project far superodistally from their alveoli, although
they appear slightly less strongly canted distally than the
third cheek−tooth. Judging from what is preserved, the
fourth cheek−tooth was about the same size as the first and
second, while the fifth is notably smaller (approximately
1.0 mm in diameter) and thus the smallest of all of the
cheek−teeth. The radiograph (Fig. 4) illustrates that the root
324 ACTA PALAEONTOLOGICA POLONICA 48 (3), 2003
1345
masseteric
fossa
mental foramen
54 31i
i
1
2
3
4
5
Fig. 3. Stereophotographs and drawings of left dentary of ?sudamericid gondwanatherian mammal (NMT 02067) from the Cretaceous of southwestern Tan−
zania in labial (A), lingual (B), and occlusal (C) views. Abbreviations: i, incisor; 1–5, cheek−teeth 1–5. Scale bar 5 mm.
i
12345
Fig. 4. X−ray radiograph of left dentary of ?sudamericid gondwanatherian
mammal (NMT 02067) from the Cretaceous of southwestern Tanzania.
A. Unaltered radiograph. B. Radiograph with outlines of tooth roots indi−
cated, and reconstructed coronal outlines of the three distal−most cheek−
teeth. Outlines of the roots were developed from several different radio−
graphs, none of which clearly revealed the outline of the root of the second
cheek−tooth, which is therefore indicated by a dashed line. Abbreviations:
i, incisor; 1–5, cheek−teeth 1–5.

of the fourth cheek−tooth, though smaller in caliber than
that of the third cheek−tooth, is also curved and very long,
extending through well over one−half of the depth of the
dentary. The fifth cheek−tooth, in keeping with its smaller
crown, has a still shorter root, which projects less than
halfway through the dentary.
Significantly, the radiograph (Fig. 4) of the dentary
clearly demonstrates that the roots of the three distal
cheek−teeth are firmly anchored in their alveoli, thus indi−
cating that they are truly hypsodont (i.e., not just appearing
to be so because they are pulled out of their alveoli). The
fact that the teeth are firmly implanted in their alveoli also
provides evidence that the three distal cheek−teeth are sin−
gle−rooted because the crowns sitting atop the roots project
far out of their alveoli and are not connected to each other.
Furthermore, there is no indication that the crown of the
third cheek−tooth was connected to that of the second. Al−
though the outlines of the root for the second cheek−tooth
cannot be discerned on the radiograph, the mesial and distal
borders of the root of the first cheek−tooth can be interpreted
and reveal that the root was obliquely oriented and therefore
most likely divergent from that for the second cheek−tooth.
This suggests that the first and second cheek−teeth were also
single−rooted.
Comparisons and preliminary
identification
NMT 02067 superficially resembles the dentaries of several
clades of Cenozoic mammals with enlarged, procumbent,
laterally compressed central incisors (e.g., rodents, lago−
morphs, wombats, the aye−aye, hyraxes, apatemyids, tillo−
donts, taeniodonts—see Koenigswald 1988). With the lim−
ited morphology available for analysis, it is impossible to
rule out the possibility that NMT 02067 is an early member
of some taxon with enlarged incisors previously known
only from Cenozoic horizons. It is not even possible to rule
out Rodentia because the possession of more than four
lower cheek−teeth is known in the bathyergid Heliophobius,
which can have as many as six (though they may not all be
in place at the same time and there is some speculation that
the increased number is the result of retained deciduous
teeth, Woods 1984; Wood 1985). Furthermore, aspects
of the anatomy of NMT 02067 are so ambiguous (e.g.,
occlusal morphology) and so little is known of Gondwanan
Cretaceous mammals that we cannot rule out the possibility
that NMT 02067 represents a new, previously unknown
taxon, possibly even one with little or no enamel on its
teeth.
Among Mesozoic mammals, however, only gondwana−
therians, and taeniolabidoid and djadochtatheroidean multi−
tuberculates, possess a large, procumbent, laterally com−
pressed lower central incisor and dentaries with the follow−
ing suite of features, also exhibited by NMT 02067: body
short and deep, unfused mandibular symphysis, distinct
diastema, and coronoid process originating far anteriorly
(see Pascual et al. 1999). Taeniolabidoid and djadochta−
therioidean multituberculates are restricted to the Late Creta−
ceous and Paleogene of Laurasia (Kielan−Jaworowska and
Hurum 2001), whereas gondwanatherians are roughly con−
temporaneous but known only from a few sites in Gond−
wana: the Late Cretaceous of Argentina (Gondwanatherium,
Ferugliotherium; Bonaparte 1986a, b, 1988, 1990; Krause et
al. 1992; Kielan−Jaworowska and Bonaparte 1996), Mada−
gascar (Lavanify; Krause et al. 1997), and India (unnamed
form; Das Sarma et al. 1995; Anantharaman and Das Sarma
1997; Krause et al. 1997); the early Paleocene of Argentina
(Sudamerica; Scillato−Yané 1984, 1985; Bonaparte et al.
1993; Pascual et al. 1999); and the Eocene of Antarctica
(unnamed form; Reguero et al. 2002). Ferugliotherium
is a member of the monotypic Ferugliotheriidae, whereas
Gondwanatherium,Sudamerica,Lavanify, and the unnamed
forms from India and Antarctica are all assigned to Sud−
americidae (Krause and Bonaparte 1993; Krause et al. 1997;
Reguero et al. 2002). Gondwanatherians were initially re−
garded as the earliest known edentates (Scillato−Yané and
Pascual 1984, 1985; Mones 1987; Bonaparte 1986a, b,
1990), then as multituberculates (Krause and Bonaparte
1990, 1993; Krause et al. 1992; Bonaparte et al. 1993;
Kielan−Jaworowska and Bonaparte 1996), and, most re−
cently, as Mammalia incertae sedis (Pascual et al. 1999;
Koenigswald et al. 1999).
We tentatively conclude that NMT 02067 is not a multi−
tuberculate and is most parsimoniously referred to the
Gondwanatheria, and more specifically to the Sudameri−
cidae (i.e., all gondwanatherians save Ferugliotherium).
This is based, in large part, on the presence of hypsodont
cheek−teeth in the specimen, and the assumption that at
least the three most distal cheek−teeth were molariform; un−
fortunately, the occlusal morphology is not preserved.
Indeed, the poor preservation of the cheek−teeth precludes
observation of synclines and islets (see terminology of
Koenigswald et al. 1999) on the crowns of the teeth, if they
existed (as they do in sudamericids to varying degrees); it
cannot be determined if such synclines and islets are absent
because NMT 02067 is in fact not a gondwanatherian, or
because NMT 02067 is a primitive gondwanatherian (see
below), or because they were once present and are simply
not preserved owing to pre− and/or postmortem wear. How−
ever, at the very least, it can be concluded, from the shape of
the dentine stump representing the third cheek−tooth, that it
was not an enlarged, laterally compressed, blade−like tooth
of the type found in almost all multituberculates. We as−
sume that it formed the core of a molariform tooth, and that
at least the three distal−most teeth of NMT 02067 were
molariform. No known multituberculate has more than two
molariform teeth in each lower jaw quadrant. Furthermore,
no known multituberculate (nor Ferugliotherium)pos
−
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KRAUSE ET AL.—TANZANIAN CRETACEOUS MAMMAL 325

sesses hypsodont cheek−teeth. The presence of hypsodont
cheek−teeth is the strongest evidence linking NMT 02067
with sudamericid gondwanatherians.
If NMT 02067 represents a gondwanatherian, the pres−
ence of five cheek−teeth indicates that it represents a less de−
rived taxon than Sudamerica. Pascual et al. (1999) recently
demonstrated the presence of four cheek−teeth, all of them
molariform, in the dentary of the sudamericid Sudamerica,
which is the only definitively identified gondwanatherian
represented by a substantial jaw fragment. NMT 02067 also
appears less derived than Sudamerica (and possibly other
sudamericids) in that the incisor is less compressed labio−
lingually (height:width ratio of 1.43, compared to 2.50 in
Sudamerica ameghinoi,2.03inGondwanatherium patago−
nicum—Krause et al. 1992; Pascual et al. 1999), the incisor
root is much shorter relative to the cheek−tooth row (extend−
ing below only the anterior cheek−teeth in the Tanzanian
form but below the entire tooth row in S. ameghinoi—
Pascual et al. 1999), and the diastema is relatively short
(presumably a function, at least in part, of the presence of
more teeth). NMT 02067 resembles the dentary of
Sudamerica in that the posterior cheek−tooth crowns (at
least the third and fourth) are curved along their height and
project superodistally. Koenigswald et al. (1999) suggested
that this distally−canted orientation of the posterior cheek−
teeth was consistent with a palinally−directed power stroke
of the masticatory cycle, which appears to have been pres−
ent in both multituberculates and gondwanatherians (e.g.,
Krause 1982; Krause and Bonaparte 1993). Finally, NMT
02067 differs from Sudamerica in at least two other charac−
ter states, the polarity of which cannot be determined at
present: a more inferiorly positioned mental foramen and an
apparently greater range of variation in the relative sizes of
its cheek−teeth.
Biogeographic implications
The following discussion is predicated on the assumption
that NMT 02067 is indeed a representative of the Gondwana−
theria, an identification that we must stress remains to be ver−
ified by more diagnostic material. If confirmed, the presence
of a gondwanatherian in the Cretaceous of Africa has impor−
tant implications for the evolutionary and biogeographic his−
tory of Gondwanan mammals. Gondwanatherians are cur−
rently regarded as Mammalia incertae sedis (Pascual et al.
1999) and, as such, they unfortunately cannot be used to re−
solve the controversy of whether or not crown−group
eutherians (i.e., placentals) arose before or after the Creta−
ceous/Tertiary boundary, or whether they originated in
Laurasia or Gondwana. However, whether from the Early or
Late Cretaceous, if our tentative identification is correct,
NMT 02067 would provide the first evidence of gondwana−
therians on the African mainland, and would be further evi−
dence of cosmopolitanism among Gondwanan mammals of
the Cretaceous (see Krause et al. 1997). If pre−Campanian,
NMT 02067 would represent the earliest known gondwana−
therian, and a substantial extension of the temporal, as well
as geographic, range of the clade (Gondwanatherium, from
the Campanian of Argentina, was previously regarded as the
earliest known gondwanatherian, see Bonaparte 1986b). If
from the Campanian or Maastrichtian, NMT 02067 has po−
tentially added utility in addressing recent hypotheses re−
garding the geographic distribution of Gondwanan mammals
and other terrestrial (and freshwater) vertebrates at the end of
the Cretaceous.
The discovery of gondwanatherians, which were ini−
tially known only from the Late Cretaceous (Campanian)
and Paleocene of Argentina, in the Late Cretaceous (Maas−
trichtian) of both Madagascar and India provided the first
evidence for cosmopolitanism among Late Cretaceous
Gondwanan mammals (Krause et al. 1997). This discovery
also led to the hypothesis that Antarctica may have served
as a biotic link between South America and Indo−Madagas−
car in the Late Cretaceous (gondwanatherians have since
been found on the Antarctic Peninsula, though from a much
later interval, the Eocene; Reguero et al. 2002). This hy−
pothesized biotic link is also supported by the presence of
sister taxa of abelisauroid theropods (Sampson et al. 1998,
2001; Carrano et al. 2002; but see Sereno et al. 2002) and
(possibly) peirosaurid and notosuchid crocodyliforms
(Buckley and Brochu 1999; Buckley et al. 2000) in the Late
Cretaceous of both South America and Indo−Madagascar,
and is consistent with Hay et al.’s (1999) recent paleo−
geographic reconstruction of Gondwana. Hay et al. postu−
lated physical connections between South America and
Indo−Madagascar through Antarctica that persisted well
into the Late Cretaceous (Krause et al. 1999). A corollary of
this hypothesis, discussed by Krause et al. (1997) and
Sampson et al. (1998), is that Africa, following its separa−
tion from South America in the Early Cretaceous, would
have an increasingly endemic fauna, and that representa−
tives of nonmarine taxa that evolved on other Gondwanan
landmasses after Africa was already isolated would likely
not be found on Africa in the last stages of the Cretaceous.
As Krause et al. (1999: 6) noted, “One of the key stum−
bling blocks for testing [these] paleobiogeographic hypoth−
eses [...] is the virtual lack of terrestrial and freshwater ver−
tebrates from the post−Cenomanian Late Cretaceous of Af−
rica.” Indeed, the record of terrestrial and freshwater verte−
brates from the Campanian and Maastrichtian of mainland
Africa is restricted to a few sites in North Africa that have
yielded scrappy material of only a few taxa (e.g., Gemmel−
laro 1921; Rauhut and Werner 1997; Churcher 1999). The
presence of a purported African Cretaceous gondwana−
therian reported here may weaken the “African endemism”
corollary outlined above; this is particularly true if the spec−
imen turns out to be from the Campanian or Maastrichtian
and if it can be demonstrated that sudamericids, which ap−
pear to be highly derived, evolved after the South America−
Africa split in the Early Cretaceous. The ultimate biogeo−
326 ACTA PALAEONTOLOGICA POLONICA 48 (3), 2003

graphic signficance of NMT 02067 cannot be realized until
it is identified with more precision, and until the phylogen−
etic interrelationships of gondwanatherians are better re−
solved. Finally, the overall inadequacy of the record of Cre−
taceous terrestrial and freshwater vertebrates from Africa,
coupled with the current controversy concerning the time
and place of origin of crown−group eutherians, strongly un−
derscore the strategic importance of continued field re−
search in the “Red Sandstone Group” to collect additional
material and to refine the age of the deposit from which
NMT 02067, and other vertebrate fossils, were recovered.
Acknowledgments
We thank the Tanzanian Commission on Science and Technology,
the Tanzanian Antiquities Unit, the National Museums of Tanzania,
and the Tanzanian Ministry of Mines and Mineral Resources, whose
cooperation made this research possible. Special thanks go to Direc−
tor Donatus Kamamba, Chediel Msuya, and Remegius Chami of the
Antiquities Unit for facilitating the fieldwork. We are also very
grateful for the help we received from government officials and resi−
dents of the Mbeya District, Ray Cox and Joe Johns and their staff at
the Utengule Country Hotel, Stephan Copes of the Utengule Coffee
Estate, Erling Johannsen, and Tim Davenport. The fieldwork was
accomplished through the dedicated efforts of participants in the
2002 reconnaissance expedition, including Yasemin Tulu (MSU),
who discovered NMT 02067, Erin Rasmusson, and Nancy Stevens.
We also thank Virginia Heisey, who skillfully prepared NMT
02067; Marylou Stewart for macrophotography; Allan Kucine for
X−ray radiography; Luci Betti−Nash for the drawings in Figs. 1–3;
Richard Cifelli, Zofia Kielan−Jaworowska, Matt Lamanna, and Josh
Smith for information on purported occurrences of Cretaceous Afri−
can mammals; and Lou Jacobs and Guillermo Rougier for helpful re−
views of the manuscript. The fieldwork aspects of this research were
supported by a faculty grant (to MDG) from the Michigan State Uni−
versity Office of the Vice−President for Research and Graduate
Studies, and by grants from the Jurassic Foundation (to PMO and
MDG) and The Paleobiological Fund (to PMO). The specimen was
prepared at the Stony Brook University Vertebrate Fossil Prepara−
tion Laboratory, funded by NSF grant EAR−0116517 (to Maureen
O’Leary and DWK). Additional support was provided by NSF grant
EAR−106477 (to DWK).
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