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The maar lake of Mahenge (Tanzania) - unique evidence of Eocene terrestrial environments in sub-Sahara Africa

Authors:
  • Leibniz-Institut zur Analyse des Biodiversitätswandels

Abstract and Figures

Recent excavations at the Eocene maar lake of Mahenge (Tanzania) by a German/Tanzanian team produced more than 1,900 fossil vertebrate, plant and trace fossils, among which fishes (51 %) make up the largest part, followed by plant remains (36 %). Surface outcrops of lacustrine sediments suggest that the Eocene crater lake was about 400 m in diameter. A 3.8 meter long section of lacustrine deposits has been documented, among which are 1.1 meter of basal lacustrine sediments that never before have been exposed. Despite intense and most probably early diagenetic dolomitization sedimentary fabrics are well preserved. Sediments from the central part of the basin are well-bedded and in places show a fine and distinctive lamination. The overall sedimentation rate in the lake centre is estimated at 0.93 mm/year. Plant fossils are characterized by an abundance of (mostly) unattached Leguminosae leaflets representing at least eight taxa out of the total of 22-23 leaf taxa distinguished so far. The Eocene vegetation at Mahenge obviously was structurally similar to the modern "miombo" woodlands of Tanzania, which are also dominated by caesalpinioid legumes. Combined with the sedimentological data, the fossil flora indicates an overall dry climate with pronounced seasonality. The Mahenge maar lake has provided five different groups of fishes plus others still undescribed. These comprise the oldest known cichlids which may represent an early species flock. Ecological requirements of the extant relatives indicate redundant evidence of the existence of a shallow water area at the lakes margins. Mammals are so far only represented by the type specimen of Tanzanycteris mannardi Gunnell et al. (2003). T. mannardi differs from all known comparable Eocene microbats in having a much larger cochlear diameter relative to basicranial width. The extremely enlarged cochlea indicates that this bat had already developed sophisticated echolocation abilities. It is possible that Tanzanycteris represents a relatively primitive ancestral rhinolophoid but the balance of its other character states aligns it with the middle Eocene Messel Hassianycteridae. Mahenge and related maar lake deposits represent a rarely sampled temporal and geographical window, which is expected to produce more significant new information about the evolution of Paleogene ecosystems in Africa, the origin of the Malagasy biota and the origin of several modern groups of plants and vertebrates, especially mammals. German Neue Ausgrabungen im eozänen Maarsee von Mahenge (Tansania) durch ein deutsch/tansanisches Team haben mehr als 1900 fossile Vertebraten, Pflanzen und Spurenfossilien erbracht, unter denen Fische (51 %) den größten Teil ausmachen, gefolgt von Pflanzenresten (36 %). Aufschlüsse lakustriner Sedimente belegen, dass der eozäne Kratersee ungefähr einen Durchmesser von 400 m hatte. Ein 3,8 m langes Profil in lakustrinen Sedimenten wurde dokumentiert, darunter sind 1,1 m basale lakustrine Sedimente, die noch niemals zuvor aufgeschlossen waren. Obwohl eine intensive, sehr wahrscheinlich postdiagenetische Dolomitisierung stattgefunden hat, ist das sedimentäre Gefüge gut erhalten. Sedimente aus dem zentralen Abschnitt des Beckens sind gut geschichtet und zeigen stellenweise eine feine Laminierung. Die Sedimentationsrate im Seezentrum wird auf 0,93 mm/Jahr geschätzt. Unter den pflanzlichen Fossilien sind die meist isoliert gefundenen Blattfiedern von Leguminosen am häufigsten. Sie repräsentieren mindestens acht Taxa aus der Gesamtheit von 22-23 Blatttaxa, die bislang unterschieden werden konnten. Die eozäne Vegetation von Mahenge war offensichtlich ähnlich strukturiert wie die modernen Miombowälder von Tansania, die auch von caesalpinoiden Leguminosen dominiert werden. Kombiniert mit den sedimentologischen Daten, zeigt die fossile Flora ein insgesamt trockenes Klima mit ausgeprägter Saisonalität an. Der Kratersee von Mahenge hat fünf verschiedene Gruppen von Fischen geliefert, sowie andere, die noch unbeschrieben sind. Die Fischfossilien umfassen die ältesten bekannten Cichliden, bei denen es sich um einen frühen Artenschwarm handeln könnte. Die ökologischen Anforderungen der rezenten Verwandten liefern redundante Hinweise auf die Existenz einer Flachwasserzone an den Seerändern. Säugetiere sind bislang nur durch das Typusexemplar von Tanzanycteris mannardi Gunnell et al. 2003 belegt. T. mannardi unterscheidet sich von allen bekannten vergleichbaren eozänen Kleinfledermäusen durch einen im Verhältnis zur Basicranialbreite viel größeren Durchmesser der Cochlea. Die extrem vergrößerte Cochlea belegt, dass die Fledermaus schon die komplexe Fähigkeit der Echoorientierung entwickelt hatte. Es ist möglich, dass T. mannardi eine relativ ursprüngliche Rhinolophide ist. Die Ausgewogenheit ihrer sonstigen Merkmale stellen sie jedoch in eine Reihe mit den Hassianycteridae aus dem Mitteleozän von Messel. Mahenge und assoziierte Maarseesedimente repräsentieren ein bisher selten belegtes zeitliches und geographisches Fenster, von dem weitere bedeutsame neue Informationen zur Evolution paläogener Ökosysteme in Afrika, dem Ursprung der Malagasi-Biota und dem Ursprung verschiedener moderner Gruppen von Landpflanzen und Vertebraten, insbesondere der Säugetiere, erwartet werden können.
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eschweizerbartxxx
Z. dt. Ges. Geowiss. 157/3, p. 411–431, 4 figs., 1 tab., 5 pts., Stuttgart, September 2006
Article
1860-1804/06/0157-0411 $ 9.45
DOI:
10.1127/1860-1804/2006/0157-0411
© 2006 E. Schweizerbart’sche Verlagsbuchhandlung, D-70176 Stuttgart
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The maar lake of Mahenge (Tanzania) – unique evidence of Eocene
terrestrial environments in sub-Sahara Africa
Thomas M. Kaiser, Jörg Ansorge, Gloria Arratia, Volker Bullwinkel, Gregg F. Gunnell,
Patrick S. Herendeen, Bonnie Jacobs, Jens Mingram, Charles Msuya,
Andreas Musolff, Rudolf Naumann, Ellen Schulz & Volker Wilde*
Kaiser, T.M., Ansorge, J., Arratia, G., Bullwinkel, V., Gunnell, G.F., Herendeen, P.S., Jacobs, B., Mingram, J.,
Msuya, C., Musolff, A., Naumann, R., Schulz, E. & Wilde, V. (2006): The maar lake of Mahenge (Tanzania) –
unique evidence of Eocene terrestrial environments in sub-Sahara Africa. [Der
Maarsee von Mahenge (Tansania) –
einzigartiger Beleg terrestrischer eozäner Lebensräume in Afrika südlich der Sahara.] – Z. dt. Ges. Geowiss., 157:
411–431, Stuttgart.
Abstract:
Recent excavations at the Eocene maar lake of Mahenge (Tanzania) by a German/Tanzanian team pro-
duced more than 1,900 fossil vertebrate, plant and trace fossils, among which fishes (51 %) make up the largest
part, followed by plant remains (36 %). Surface outcrops of lacustrine sediments suggest that the Eocene crater
lake was about 400 m in diameter. A 3.8 meter long section of lacustrine deposits has been documented, among
which are 1.1 meter of basal lacustrine sediments that never before have been exposed. Despite intense and most
probably early diagenetic dolomitization sedimentary fabrics are well preserved. Sediments from the central part
of the basin are well-bedded and in places show a fine and distinctive lamination. The overall sedimentation rate in
the lake centre is estimated at 0.93 mm/year. Plant fossils are characterized by an abundance of (mostly) unat-
tached Leguminosae leaflets representing at least eight taxa out of the total of 22–23 leaf taxa distinguished so far.
The Eocene vegetation at Mahenge obviously was structurally similar to the modern “miombo” woodlands of Tan-
zania, which are also dominated by caesalpinioid legumes. Combined with the sedimentological data, the fossil
flora indicates an overall dry climate with pronounced seasonality. The Mahenge maar lake has provided five dif-
ferent groups of fishes plus others still undescribed. These comprise the oldest known cichlids which may repre-
sent an early species flock. Ecological requirements of the extant relatives indicate redundant evidence of the ex-
istence of a shallow water area at the lakes margins. Mammals are so far only represented by the type specimen of
Tanzanycteris mannardi
Gunnell et al. (2003).
T. mannardi
differs from all known comparable Eocene microbats
in having a much larger cochlear diameter relative to basicranial width. The extremely enlarged cochlea indicates
that this bat had already developed sophisticated echolocation abilities. It is possible that
Tanzanycteris
represents
a relatively primitive ancestral rhinolophoid but the balance of its other character states aligns it with the middle
Eocene Messel Hassianycteridae. Mahenge and related maar lake deposits represent a rarely sampled temporal
and geographical window, which is expected to produce more significant new information about the evolution of
* Addresses of the authors: PD Dr. Thomas M. Kaiser (thomas.kaiser@uni-hamburg.de), Dipl.-Biol. Ellen Schulz, Biocentre
Grindel and Zoological Museum, University Hamburg, Martin-Luther-King-Platz 3, 20146 Hamburg, Germany; Dr. Jörg Ansor-
ge, Institut für Geologische Wissenschaften, Universität Greifswald, Jahnstraße 17a, 17487 Greifswald, Germany (ansorge@
uni-greifswald.de); Prof. Dr. Gloria Arratia, Naturhistorisches Forschungsinstitut – Museum für Naturkunde, Invalidenstr. 43,
10115 Berlin, Germany, and Biodiversity Research Center, University of Kansas, Lawrence, KS 66045-7561, USA
(garratia@ku.edu); Dr. Volker Bullwinkel, Geowissenschaftliches Zentrum der Universität Göttingen (GZG), Universität Göttin-
gen, Goldschmidtstraße 3, 37077 Göttingen, Germany (vb-public@factworld.de); Dr. Gregg F. Gunnell, Museum of Paleontolo-
gy, University of Michigan, Ann Arbor, MI 48109-1079, USA (ggunnell@umich.edu); Prof. Dr. Patrick S. Herendeen,
Department of Biological Sciences, The George Washington University, Washington, DC, 20052, USA (herenden@gwu.edu);
Prof. Dr. Bonnie Jacobs, Environmental Science Program, Southern Methodist University, P.O. Box 750395, Dallas, TX 75275-
0395, USA (bjacobs@smu.edu); Dr. Jens Mingram, Rudolf Naumann, GeoForschungsZentrum Potsdam, Telegrafenberg, 14473
Potsdam, Germany (ojemi@gfz-potsdam.de); Charles Msuya, Muhimbili University College of Health Sciences Dar-es-Salaam,
P.O. Box 65264, Dar-es-Salaam, Tanzania (cmsuya15@yahoo.com.uk); Dipl.-Geol. Andreas Musolff, Institut für Geographie und
Geologie, Universität Greifswald, Jahnstraße 17a, 17487 Greifswald, Germany (Andreas.Musolff@gmx.de); PD Dr. Volker
Wilde, Forschungsinstitut Senckenberg, Palaeobotanik, Senckenberganlage 25, 60325 Frankfurt am Main, Germany (Volker.
Wilde@senckenberg.de).
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Paleogene ecosystems in Africa, the origin of the Malagasy biota and the origin of several modern groups of plants
and vertebrates, especially mammals.
Kurzfassung:
Neue Ausgrabungen im eozänen Maarsee von Mahenge (Tansania) durch ein deutsch/tansani-
sches Team haben mehr als 1900 fossile Vertebraten, Pflanzen und Spurenfossilien erbracht, unter denen Fische
(51 %) den größten Teil ausmachen, gefolgt von Pflanzenresten (36 %). Aufschlüsse lakustriner Sedimente bele-
gen, dass der eozäne Kratersee ungefähr einen Durchmesser von 400 m hatte. Ein 3,8 m langes Profil in lakustri-
nen Sedimenten wurde dokumentiert, darunter sind 1,1 m basale lakustrine Sedimente, die noch niemals zuvor
aufgeschlossen waren. Obwohl eine intensive, sehr wahrscheinlich postdiagenetische Dolomitisierung stattge-
funden hat, ist das sedimentäre Gefüge gut erhalten. Sedimente aus dem zentralen Abschnitt des Beckens sind
gut geschichtet und zeigen stellenweise eine feine Laminierung. Die Sedimentationsrate im Seezentrum wird auf
0,93 mm/Jahr geschätzt. Unter den pflanzlichen Fossilien sind die meist isoliert gefundenen Blattfiedern von Le-
guminosen am häufigsten. Sie repräsentieren mindestens acht Taxa aus der Gesamtheit von 22–23 Blatttaxa, die
bislang unterschieden werden konnten. Die eozäne Vegetation von Mahenge war offensichtlich ähnlich struktu-
riert wie die modernen Miombowälder von Tansania, die auch von caesalpinoiden Leguminosen dominiert wer-
den. Kombiniert mit den sedimentologischen Daten, zeigt die fossile Flora ein insgesamt trockenes Klima mit
ausgeprägter Saisonalität an. Der Kratersee von Mahenge hat fünf verschiedene Gruppen von Fischen geliefert,
sowie andere, die noch unbeschrieben sind. Die Fischfossilien umfassen die ältesten bekannten Cichliden, bei
denen es sich um einen frühen Artenschwarm handeln könnte. Die ökologischen Anforderungen der rezenten
Verwandten liefern redundante Hinweise auf die Existenz einer Flachwasserzone an den Seerändern. Säugetiere
sind bislang nur durch das Typusexemplar von
Tanzanycteris mannardi
Gunnell et al. 2003 belegt.
T. mannardi
unterscheidet sich von allen bekannten vergleichbaren eozänen Kleinfledermäusen durch einen im Verhältnis zur
Basicranialbreite viel größeren Durchmesser der Cochlea. Die extrem vergrößerte Cochlea belegt, dass die Fle-
dermaus schon die komplexe Fähigkeit der Echoorientierung entwickelt hatte. Es ist möglich, dass
T. mannardi
eine relativ ursprüngliche Rhinolophide ist. Die Ausgewogenheit ihrer sonstigen Merkmale stellen sie jedoch in
eine Reihe mit den Hassianycteridae aus dem Mitteleozän von Messel. Mahenge und assoziierte Maarseesedi-
mente repräsentieren ein bisher selten belegtes zeitliches und geographisches Fenster, von dem weitere bedeutsa-
me neue Informationen zur Evolution paläogener Ökosysteme in Afrika, dem Ursprung der Malagasi-Biota und
dem Ursprung verschiedener moderner Gruppen von Landpflanzen und Vertebraten, insbesondere der Säugetie-
re, erwartet werden können.
Keywords:
Mahenge, maar lake, Eocene, Paleogene, Tanzania, terrestrial environment, palaeontology, palaeo-
ecology, palaeoclimate
Schlüsselwörter:
Mahenge, Maarsee, Eozän, Paläogen, Tansania, terrestrische Lebensräume, Paläontologie, Pa-
läoökologie, Paläoklima
1. Introduction
The Singida kimberlite field, with more than fifty kimber-
lite pipes and dykes, is located on a broad peneplain, just
to the south of the Iramba Plateau in north-central Tanza-
nia (Mannard 1962). The latter represents a large tilted
fault-block at the south-western extremity of the Gregory
Rift, with a maximum elevation of 1,680 m above sea lev-
el (Teale 1931, 1932, Eades 1936, Williams 1939). Steep
fault-scarps border the Wembere depression and Eyasi
trough to the north and west, and the Mpura-Durumo val-
ley to the east (Fig. 1). To the south, the plateau grades im-
perceptibly into the peneplain. The combination of mature
peneplanation and long-term tectonic stability south of the
Iramba Plateau has resulted in a topography of relatively
uniform relief, with elevations ranging from 1,100 m to
1,500 m, and creating a gently undulating terrain (Fig. 2).
Outcrops of granite are common (Plate 1: Fig. B), forming
small inselbergs or craggy tors that rise above the level of
the peneplain. Most parts of this peneplain can be associ-
ated with the “African Surface” (King 1962) that was
formed at the end of the Cretaceous.
The locality at Mahenge (4º 47' 50.2" S; 34º 15' 54.5"
E) is close to the village of Mwaru, 65 km west of the
town of Singida (Fig. 1) and east of the Wembere Steppe
and may be reached by car via forest trail.
Mahenge and its fossils is the subject of this contribu-
tion. Our main goal is to present the state of the art of the
present knowledge of the locality and its fossiliferous
content, and to compare our findings with those by previ-
ous authors. First, we will analyze the information and
interpretation on the locality, and second, on the fossils
and their importance.
2. Evidence for the age of the lake beds
The relationships of the fish fauna led Greenwood & Pat-
terson (1967) to favour a Paleogene (probably Oligocene)
age for the Mahenge sequence. A kimberlite near Nzega,
120 km to the west of Mahenge, has yielded U-Pb dates
of 52.2 and 53.2 Ma, and fission track dates of 54.3 +
14 Ma and 51.1 + 3.8 Ma (Davis 1977, Naeser & McCal-
lum 1977, Haggerty et al. 1983), indicating an early
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Eocene (= Ypresian) age. Harrison et al. (2001) report a
middle Eocene (Lutetian) 206Pb/238U age of 45.83 ±
0.17 Ma from a single zircon crystal which was recov-
ered from the stream bed at Mahenge in 1996. There are
several arguments linking the respective crystal to the
Mahenge diatreme. Recent catchment area of the stream
crossing the Mahenge diatreme is small (7.2 km
2
). It cov-
ers Archaean metamorphics and plutonics and no other
known diatreme. The catchment area can be expected not
to have varied much since formation of the peneplain in
the Cretaceous. Therefore, the crystal with a middle
Eocene age found in the stream bed at Mahenge can most
probably be related to the Mahenge eruptive event and
could be only slightly older than the lake at Mahenge. It
is well known from similar maar lakes in Europe and Af-
rica that accumulation of lacustrine sediments starts soon
after the formation of the crater (Lorenz 1973, Smith
1986, Rayner & McKay 1986, Rayner 1987, Giresse et
al. 1991, Cornen et al. 1992). Harrison et al. (2001) there-
fore confidently assume that the fossils recovered from
the maar sediments date to ~ 45–46 Ma.
3. Recent excavations at Mahenge
During the SSPP (Sub-Sahara-Paleogene-Project) field
campaign in July–August 2002 a total of 17 exposures
within the Mahenge crater were studied (Fig. 3) and doc-
umented in detail with respect to stratigraphy and sedi-
mentology. Most of the natural exposures are located
along the cutbank of the Luwala River (Plate 1: Figs. A,
C) crossing the crater from NE to SW (Fig. 3). During the
2002 field work the river bed was dry and largely accessi-
ble. Additional exposures were excavated along a transect
Fig. 1: The diatreme fields in North-Central Tanzania. Note the concentrations near Nzega, Singida, and Shinyanga, which are sep-
arated by the Wembere Steppe. The Mahenge diatreme is located in the far West of the Singida diatreme field.
Abb. 1: Das Diatremfeld in Nord-Zentral-Tansania. Die Konzentrationen in der Umgebung von Nzega, Singida und Shinyanga wer-
den durch die Wembere-Steppe getrennt. Der Mahenge-Diatrem liegt weit im Westen des Singida-Diatremfeldes.
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oriented NW–SE roughly perpendicular to the river bank
(Fig. 3). This transect includes pits already exploited by
Mannard (1962), which were subsequently re-activated
and substantially extended and deepened, as well as new
pits dug (e.g. pit 12; cf. Fig. 3, Plate 1: Fig. D).
The main excavation efforts were concentrated in the
putative centre of the maar (pits 5 and 6 of Mannard 1962
and Harrison et al. 2001). At pit 05 (Plate 1: Fig. D), a
section of 3.80 m of mostly well-bedded and fossiliferous
lake sediments has been exposed (Fig. 4) and constituted
the reference profile for the central part of the lake beds.
Part of a similar (shorter) section was described by Harri-
son et al. (2001) and Jacobs & Herendeen (2004), howev-
er correlation was found to be so difficult due to laterally
varying degrees of silicification and cementation, that a
new section had to be documented.
3.1. The “pit 05c” section (P5C)
The base of section P5C is formed by a homogeneous
siltstone bed (0 m to 0.20 m) which is highly solidified by
carbonate and silica. Towards the top this bed grades into
a soft and friable siltstone (0.20 m to 0.60 m). The yel-
lowish grey (5Y 8/1) sediment is homogeneous, contain-
ing a certain fraction of fine sand which is randomly dis-
tributed throughout the entire thickness of the bed.
Occasionally, fine sand is concentrated in thin horizons
and lenses. Above 0.60 m the siltstone is succeeded by a
succession about 1.90 m in thickness of calcareous mud-
stones and mudstones which are in part strongly silici-
fied. Well-consolidated calcareous mudstones are 2 cm to
8 cm thick and contrast sharply with the underlying
facies. The upper surface is also sharp. However, between
1.20 m and 2.50 m the compact mudstones typically be-
come less competent towards the top and grade into fria-
ble or finely fracturing mudstones. Despite their low
Fig. 2: Modelled surface of the Mahenge diatreme area. Altitude data base on GPS-mapping in the field. The arrow points north.
Red dots mark the diatrem’s circumference. Blue line marks the bed of the Luwala River. The diatreme itself forms a shallow de-
pression. It is surrounded by an elevated ring structure, probably consisting of remnants of the tephra-wall, related to the eruptive
event. Vertical scaling is 1:2.3; coordinate system is UTM.
Abb. 2: Oberflächenmodell des Diatremgebietes von Mahenge. Höhenwerte basieren auf GPS-Daten, die im Gelände gewonnen
wurden. Der Pfeil weist nach Norden. Rote Punkte markieren den Umfang des Diatrems. Die blaue Linie markiert das Bett des Lu-
wala Flusses. Der Diatrem selbst ist eine flache Vertiefung. Er ist von einer leicht erhöhten Ringstruktur umgeben, die wahrschein-
lich aus den Resten des ehemaligen Tephrawalles besteht. Vertikaler Maßstab: 1:2,3; Koordinatensystem: UTM.
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competence, the friable mudstones are well-bedded
showing a fine and distinctive lamination. Calcitic coat-
ings of cleavages and bedding planes are a characteristic
feature of these finely fracturing mudstone layers.
Strongly silicified mudstones are prominent within
the section due to their hardness and their conspicuous
light olive colour (5Y 7/2). However, they are not suited
for correlation since the degree of their silicification var-
ies in vertical as well as lateral direction.
The P5C section terminates in a hard but vaguely
stratified bed of a strongly lithified mudstone (2.50 m to
2.70 m). About 2 m further west of the section P5C this
top of exposed lake sediments is highly disturbed. Here
Harrison et al. (2001) describe a section of about 1 m in
thickness in which massive blocks of poorly laminated
yellowish grey mudstone occur together with slabs of
consolidated mudstones within a matrix of friable shale.
This section was re-investigated in 2003 and we find our
stratigraphic observations to be in general agreement
with Harrison et al. (2001).
3.2. Abdallah’s hole section (AHS)
The base of section P5C is an extremely hard siltstone
bed of up to 20 cm in thickness. Since section P5C is sit-
uated almost in the centre of the former maar lake, and
thus represents the deepest point that any prior excava-
tion had reached within the lacustrine succession of the
lake, the AHS section was never before exposed. It thus
represents the so far oldest known sediments from Ma-
henge, the top of which Harrison et al. (2001) considered
the base of the lacustrine series. Penetration of the hard
siltstone bed at the base of P5C was laborious, and in
honour of Mr. Abdallah, who exposed the section below
within several days of hard labour, the section is referred
to as “Abdallah’s Hole Section” (AHS).
Fig. 3: Map of the Mahenge diatreme with excavation localities and natural outcrops indicated. Note that excavation so far has only
been carried out along a transect connecting pits 05a–e, 12, and 06a–c. These localities expose well stratified laminated deposits
and all represent the central part of the former lake beds.
Abb. 3: Karte des Mahenge-Diatrems mit Grabungsstellen und natürlichen Aufschlüssen. Grabungen wurden bislang nur entlang
eines Transsekts durchgeführt, der die Grabungsstellen pit 05a–e, 12 und 06a–c miteinander verbindet. Diese Lokalitäten schließen
gut geschichtete Ablagerungen auf und repräsentieren den zentralen Teil der ehemaligen Seesedimente.
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Fig. 4: Stratigraphic section of pit 05c and the
adjacent “Abdallah’s Hole Section”. The vast
majority of fossils so far known from Mahenge
derive from a 20 cm thick section at the base of
the P05c profile at between 65 cm and 85 cm.
This section widely corresponds with the hori-
zons 3–6 of Harrison et al. (2001).
Abb. 4: Profil der Grabungsstelle pit 05c und
der sich anschließenden „Abdallah’s Hole Sec-
tion“. Die überwiegende Mehrzahl der bislang
von Mahenge bekannten Fossilien stammt von
einem etwa 20 cm mächtigen Schichtpaket an
der Basis des pit 05c-Profils zwischen 65 cm
and 85 cm. Dieses Profil entspricht weitgehend
den Horizonten 3–6 nach Harrison et al. (2001).
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This 1.10 m thick section (Fig. 4) consists mainly of
calcareous mudstones, silicified mudstones, and sandy
siltstones. The calcareous mudstones as well as the silici-
fied mudstones are lithologically comparable with the
mudstones of section P5C. These generally well-bed-
ded sediments, however, include numerous silt layers
ranging in thickness from <1 mm to 5 mm. Noteworthy is
the frequent occurrence of sandy siltstones of up to 10 cm
in thickness. Between 0.60 m and 0.70 m clasts of lami-
nated mudstones (“intraclasts”) up to 5 cm in width are
irregularly embedded within a homogeneous silt/sand
matrix. Lenticular clasts of reworked lake sediment also
occur at the base of silt/sand layers which are character-
ized by graded bedding of coarse or medium grained
sand at the base to fine sand and silt at the top.
The surface outcrops of lacustrine sediments within
the Mahenge crater area suggest that the lake had a diam-
eter of about 400 m (see also Mannard 1962, Harrison et
al. 2001). The sections of “pit 05c” and “Abdallah’s
Hole” mainly represent the fine-grained sediments which
were deposited near the centre of the lake. It can be in-
ferred that rather steep slopes bordered the crater’s lake
in its early stage. The collapse of crater walls and slump-
ing of debris repeatedly triggered transport of coarse-
grained sediment towards the centre of the lake and led to
a gradual reduction in relief. As the lake margins contin-
ued to be flattened the sediment input became finer in
grain size. This stage of lake development is documented
in the AHS profile. The 10 cm thick homogeneous silt/
sand layers as well as the clasts bearing graded layers
represent the episodic sediment input by mudflows and
turbidity currents respectively.
Compared with AHS there is little evidence of input
by bedload in section P5C. The succession between
0.60 m and 2.50 m is dominated by well-bedded, in part
distinctly laminated carbonaceous mudstones. The re-
markable quality of fossil preservation in combination
with the total lack of bioturbation provides clear evidence
of stable stratification of the water column and anoxic
conditions near the sediment surface (Herendeen &
Jacobs 2000, Harrison et al. 2001, Kaiser et al. 2003).
4. Microfacies analysis of the
lacustrine sequence in the basin
centre
A set of petrographic thin sections, comprising app.
0.5 m from different depths of the recent section has been
studied microscopically. All materials investigated have
been sampled by the SSPP. Light microscopy was en-
gaged as plane light-, polarized light-, dark field-illumi-
nation, and fluorescence in order to obtain information on
the process of sediment deposition and diagenesis. Addi-
tionally, samples were taken for X-ray diffraction analy-
ses to identify the major mineral constituents of the sedi-
ments.
Mineral phases which could be identified by X-ray
diffraction are dolomite, opal-CT, crystalline quartz, and
some palygorskite. Petrographically the sediment is a do-
lostone with some silicified horizons. In all thin sections,
micritic and micro-sparitic xenomorphic dolomite (of
app. 2–15 μm grain size) is the most common mineral
(Plate 2: Figs. A–H). Sometimes calcitic vein fillings and
coarse-grained laminae containing micro-sparitic calcite
could be observed (Plate 2: Fig. C). Despite intense and
most probably early diagenetic dolomitization sedimen-
tary fabrics are well preserved.
Most samples in thin sections exhibit sub-mm scale
lamination, which points to an at least seasonally devel-
oped oxygen deficiency of the lake’s bottom water and a
seasonal climate. Frequently occurring graded event lay-
ers (Plate 2: Figs. A–B), ranging in thickness from sub-
mm to several cm, indicate catchment erosion by heavy
rain showers.
Strong seasonal lamination sometimes is replaced by
sediments with lenticular and flaser bedding and only
faint lamination, which could be caused by climatically-
induced lake level changes and/or changing influx of a
small tributary. Graded event layers often contain re-
worked lake sediments (“intraclasts”), coated lithic
grains (quartz, feldspars, some biotite) with varying stag-
es of replacement by dolomite, dolomitic peloids, some
ooids, and indeterminate ostracode shells (Plate 2: Figs.
D, E, F), with the latter pointing to the existence of a mar-
ginal shallow-water zone, provided they represent ben-
thonic taxa.
Except for the ostracode shells no remains of aquatic
organisms could be observed. But in fact, there are some
laminations which resemble those of diatomaceous lam-
inites from recent and ancient lake sediments (Bullwinkel
2003). But if there were primary diatomaceous layers
they are already totally altered into opal-CT and/or re-
placed by dolomite (Plate 2: Figs. B, C and G, H). This is
in good accordance to the fact that diatoms are known for
fast alteration (Bullwinkel 2003).
As the Mahenge laminated sediments both in fabric
and thickness strongly resemble recent seasonally lami-
nated lake sediments (varves), an estimation of sedimen-
tation rates by varve counting has been undertaken. For a
total thickness of 492.6 mm in thin sections from differ-
ent parts of the profile (including graded event layers),
529 varves could be found, which yields an overall sedi-
mentation rate of 0.93 mm/year which is considerably
higher than previously estimated by Harrison et al.
(2001). Taking into account this rate, the recent 5.5 m
long Mahenge profile represents app. 5,000 years of the
lake’s history.
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5. The fossil record of the Mahenge
maar
During the SSPP expedition much attention was paid to
record and collect all fossils that came to our attention
during the excavation. A large bias was accepted in iso-
lated fish scales, isolated fish bones and extremely disar-
ticulated fishes, as well as plant fragments that did not al-
low any closer determination. Excavations in 2002 thus
yielded a total of 1,948 fossil specimens. This number ex-
ceeds the number of all previously known fossils from
Mahenge and is by far the largest number of specimens
ever collected from this locality (Tab. 1). Like in the col-
lections of Harrison et al. (2001) fishes are the most
abundant group (n = 993) and make up 51 % of the SSPP
specimens. Plants are the second abundant group (n =
698) and make up 36 %. However it should be men-
tioned, that we collected about two times as many fishes,
but almost ten times as many plant fossils compared to
Harrison et al. (2001). This remarkable difference is most
likely not due to taphonomy but is expected to reflect the
different sampling strategies of the two teams. In addition
the SSPP collected a fairly large number of coprolites (n
= 51, 2.6 %) and “sand nests” (n = 178, 9.1 %). These pe-
culiar small scale accumulations of fine to medium
grained sand are also common in the deposits of the Mid-
dle Eocene northern hemisphere maar lake of Messel
(Germany) where they have been interpreted as spitting
debris mainly of fishes (Schmitz 1991). At Mahenge as
also at Messel they represent the only sandy inclusions in
the central facies of the basin. Arthropods (<0.4 %) and
frogs (0.2 %; Plate 4: Fig. D) are among the most rare
taxa (see Tab. 1). This rarity has been confirmed by all
parties working at Mahenge so far.
Tab. 1: Representation of fossils recovered in the SSPP exca-
vations at Mahenge in 2002 (n-SSPP and %-SSPP) and fossils
reported by Harrison et al. (2001) in 1994 and 1996 (n-H2001
and %-H2001). Note, that fish remains are the most abundant
fossil group followed by plants. Sand nests and coprolites have
been collected for taphonomic reasons.
Tab. 1: Auflistung der im Rahmen der SSPP-Ausgrabungen in
Mahenge 2002 geborgenen Fossilien (n-SSPP und %-SSPP),
sowie von Fossilien die Harrison et al. (2001) 1994 und 1996
geborgen haben (n-H2001 and %-H2001). Fischreste stellen
die häufigste Fossilgruppe, gefolgt von Pflanzen. Sandnester
und Koprolithen wurden aus taphonomischen Gründen gebor-
gen.
n-SSPP %-SSPP n-H2001 %-H2001
Fish 993 51.0 513 81.40
Plant 698 35.8 85 13.49
Sand nest 178 9.1
Coprolite 51 2.6
17 2.70
Indeterminate
specimens
17 0.9
Invertebrates
(mostly arthropods)
7 0.4 5 0.79
Frogs 4 0.2 4 0.63
Total 1948 624
Plate 1:
Fig. A: The vegetation at Mahenge is miombo woodland, dominated by tree species like Julbernardia, Isoberlinia, and Brachyste-
gia. The Luwala River bed crosses the diatreme from NE to SW (view northward) and potholes (foreground) indicate that it may
have substantial transport energy in the rainy season.
Fig. B: Granite outcrop 39 (cf. Fig. 3) marking the NE boundary of the diatreme, the foreground being inside, the granite pitch be-
ing outside. At this place the Luwala River enters the diatreme as a cascade.
Fig. C: Massive beds of reworked pyroclastic material exposed in the river bed upstream of the crater centre. These partially graded
beds dip slightly (8˚ to 16˚) towards the former lake centre and represent the episodic input of coarse-grained sediment from the
crater slopes.
Fig. D: Excavation pits close to the centre of the former lake structure (view ESE). Foreground: pit 12, background right: pit 05d,
background left: pits 05a–c.
Tafel 1:
Fig. A: Die Vegetation von Mahenge wird von Miombowald gebildet. Es dominieren Bäume wie Julbernardia, Isoberlinia und
Brachystegia. Das Bett des Luwala-Flusses durchschneidet den Diatrem von NE nach SW (Blickrichtung Nord). Die Kolke im Vor-
dergrund zeigen an, dass er in der Regenzeit eine erhebliche Transportenergie aufweist.
Fig. B: Der Granitaufschluss 39 (s. Abb. 3) markiert die NE-Grenze des Diatrems. Der Vordergrund ist innerhalb, die Granitstufe
befindet sich außerhalb des Diatrems. Hier tritt der Fluss Luwala in einem Wasserfall in den Diatrem ein.
Fig. C: Massive Schichtenfolgen aufgearbeiteten pyroklastischen Materials sind im Flussbett stromaufwärts des Kraterzentrums
aufgeschlossen. Die teilweise gradierte Schichtenfolge fällt leicht (8° bis 16°) zum ehemaligen Seezentrum hin ein und entspricht
dem episodischen Eintrag grobkörniger Sedimente von den Hängen des Kraterwalls.
Fig. D: Grabungsstellen in der Nähe des Zentrums der ehemaligen Seestruktur (Blickrichtung ESE). Vordergrund: Grabungsstelle
pit 12; Hintergrund rechts: Grabungsstelle pit 05d; Hintergrund links: Grabungsstelle pit 05a–c.
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5.1. The flora
Plant macrofossils collected from Mahenge now number
over 1,000 specimens and are most common in the lower
stratigraphic levels of pit 05c–d (levels 7–8 of Harrison et
al. 2001 and Jacobs & Herendeen 2004). They are char-
acterized by an abundance of (mostly) unattached Legu-
minosae leaflets (Plate 3: Figs. A, C, E, Plate 4: Fig. C)
representing at least eight taxa out of the total of 22–23
leaf taxa distinguished so far. Included among these are
more complete specimens of
Acacia
mahengensis
(Plate
4: Figs. A, B),
Aphanocalyx
singidaensis
(Plate 3: Fig.
A),
Bauhinia
sp., two taxa superficially similar to
Cy-
nometra
spp. (Plate 3: Fig. D), and an unknown mi-
mosoid (Plate 3: Fig. F; Herendeen & Jacobs 2000). The
vast majority of the isolated leaflets may be assigned to
the subfamily Caesalpinioideae (Plate 3: Figs. C, D), rep-
resenting one or more of cf.
Cynometra
affinity. The re-
maining dicotyledonous taxa are represented primarily
by microphyllous, entire-margined leaves that are distin-
guished by venation patterns and overall shape, but of
still unknown affinity; only two taxa with a toothed mar-
gin have been found. Monocotyledonous remains are
common among the leaves but have yielded only faint in-
dications of epidermal cellular structure, rendering them
unidentifiable. Nevertheless, it is important to note that
plants with “graminoid” leaves were a significant part of
the lake or lake-margin ecosystem. On the basis of what
we know of the composition of the Mahenge palaeoflora,
it was structurally similar to the modern “miombo”
woodlands of Tanzania, which are also dominated by
caesalpinioid legume taxa. Regrettably, no palynomorphs
have been recovered from a number of sediment samples
which were processed.
Plate 2:
Thin sections of lacustrine deposits from Mahenge (pit 06a). All photos made with transmitted light; B and G with parallel polariz-
ers, C, D, E, F, and H with crossed polarizers.
Fig. A: Flat-bed scan, transmitted light with crossed polarizers. Note alternation of seasonal laminae and graded event layers con-
taining reworked material (intraclasts). Sample SSPP MA-2079.
Fig. B: Laminated sediment. Note intercalation of event layers and coarser allochthonous minerals (lithoclasts). Coarse layers in
the lower half of the section contain numerous peloids and ostracode shells. Thickness of one doublet of fine laminae (varve) is
250–300 μm. Sample SSPP MA-2087.
Fig. C: Detail of Fig. B. At the base note a coarse-grained event layer with altered lithoclasts and micro-sparitic calcite matrix. Dark
laminae consist of dense, micritic dolomite (grain size 2–5 μm) and some lithoclasts, whereas lighter laminae are composed of
opal-CT with minor amounts of micritic to micro-sparitic dolomite (grain size 2–10 μm).
Fig. D: Detail of a coarse-grained event layer with coated grains and peloids. Sample SSPP MA-2087.
Fig. E: Quartz and feldspar are partly replaced by micritic secondary dolomite. Same sample as D.
Fig. F: Ostracode shell in a coarse-grained event layer. Sample SSPP MA-2073.
Fig. G: Dark laminae contain more lithoclasts and indicate periodic, most probably seasonal, inwash of allochthonous material.
Sample SSPP MA-2073.
Fig. H: Detail of Fig. G. Seasonal lamination with matrix composed of opal-CT without biogenic remains. The lamination is over-
printed by micritic to micro-sparitic secondary dolomite. Thickness of one doublet of laminae (varve) is 200 μm.
Tafel 2:
Dünnschliffe lakustriner Ablagerungen von Mahenge (pit 06a). Alle Aufnahmen wurden mit Durchlicht, B und G mit parallelen
Polfiltern, C, D, E, F und H mit gekreuzten Polfiltern aufgenommen.
Fig. A: Flachbettscan im Durchlicht, mit gekreuztem Polfilter aufgenommen. Deutlich ist der Wechsel von saisonalen Laminae und
Ereignislagen, die aufgearbeitetes Material (Intraklasten) enthalten. Probe SSPP MA-2079.
Fig. B: Das laminierte Sediment zeigt Einschaltungen von Ereignislagen und gröberen allochthonen Mineralien (Lithoklasten).
Gröbere Lagen in der unteren Hälfte des Profils enthalten zahlreiche Peloide und Ostracodenschalen. Die Dicke eines Doublets
feiner Laminae (Warven) beläuft sich auf 250–300 μm (Probe SSPP MA-2087).
Fig. C: Detailansicht von Fig. B mit einer grobkörnigen Ereignislage mit alterierten Lithoklasten und micro-sparitischer Kalzitma-
trix an der Basis. Dunkle Laminae bestehen aus dichtem, mikritischem Dolomit (Korngröße 2–5 μm) und einigen Lithoklasten,
während hellere Laminae von Opal-CT und geringen Anteilen von mikritischem bis micro-sparitischem Dolomit gebildet werden
(Korngröße 2–10 μm).
Fig. D: Detail einer grobkörnigen Ereignislage mit coated grains und Peloiden (Probe SSPP MA-2087).
Fig. E: Quarz und Feldspat sind teilweise ersetzt durch mikritische Sekundärdolomite (gleiche Probe wie Fig. D).
Fig. F: Ostracodenschalen in einer grobkörnigen Ereignislage (Probe SSPP MA-2073).
Fig. G: Dunkle Laminae enthalten mehr Lithoklasten und zeigen periodische, sehr wahrscheinlich saisonale Einspülungen von al-
lochthonem Material an (Probe SSPP MA-2073).
Fig. H: Das Detail von Fig. G zeigt saisonale Lamination mit einer aus Opal-CT bestehenden Matrix, jedoch ohne biogene Reste.
Die Lamination ist überprägt von mikritischen bis mikro-sparitischen Sekundärdolomiten. Dicke eines Laminen-Doublets (Warve):
200 μm.
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Mean annual and wet months rainfall (all months with
an average of
50 mm) were estimated for Mahenge us-
ing regression formulas derived from modern tropical Af-
rican and South American leaf and climate data (Wilf et
al. 1998, Jacobs 1999, 2002, Gregory-Wodzicki 2000,
Jacobs & Herendeen 2004). Mean annual precipitation
estimates are 643 ± 32 and 776 ± 39 mm/year, or near the
modern annual average of 660 mm. The wet months pre-
cipitation estimates are 630 ± 38 and 661 ± 38 mm, or
somewhat higher than the modern 595 mm, indicating
that, although there was a dry season (or seasons), more
of the annual rainfall may have occurred during the dry
season(s) than today, and therefore the dry interval may
have been slightly less pronounced during Mahenge time.
Such a climate is consistent with the sedimentological
data which also indicate a pronounced dry season and
overall dry climate based upon the dominance of dolo-
mite in the fossil matrix.
5.2. Insects
Insect remains are some of the most rarely recorded fos-
sils at Mahenge. However when preserved, the quality of
preservation is very detailed. Therefore Mahenge is con-
sidered one of the few potential insect lagerstätten in Af-
rica, comparable to the Middle Cretaceous kimberlite di-
atreme of Orapa in Botswana (Rayner et al. 1991). Of
special interest is a rather complete beetle in dorso-ven-
tral compression, with well-preserved legs and one out-
stretched hind wing (Plate 4: Figs. E, F). On the basis of
these characters the fossil is identified as a scarabaeid
beetle [Scarabaeoidea (Lamellicornia)]. Besides an unde-
scribed Scarabaeidae from Orapa (McKay & Rayner
1986, Krell 2004) and some Miocene dung beetles from
Kenya (Paulian 1976), the Mahenge fossil is one of the
few fossil scarabaeid beetles known from Africa.
5.3. The fish fauna
Fish fossils are the most abundant animal group repre-
sented at Mahenge. The vast majority of individuals are
in articulated preservation, however also isolated scales
are to be found.
The Cenozoic freshwater fossil fishes from Africa are
little known and in many cases, represented only by frag-
ments. An initial review of the fossil record at Mahenge
was provided by Greenwood (1974) and more recently by
Murray (2000a). Among all fossil African localities bear-
ing fishes, Mahenge is probably the most important one,
because hundreds of complete and almost complete spec-
imens have been recovered here. Some of them, as for in-
stance, osteoglossomorphs (Plate 5: Fig. D) and cichlids
(Plate 5: Fig. B), are even represented as ontogenetic se-
ries in the SSPP material.
The Mahenge crater’s lake has provided five different
groups of fishes plus others still undescribed. Up to now,
two osteoglossomorphs (Plate 5: Fig. D), a clupeomorph,
a characiform, a siluriform (Plate 5: Fig. A), and five per-
comorphs (Plate 5: Fig. B) have been formally described.
As with almost all fossils from Mahenge, this sample
also was collected from the central part of the lake (pits
05 and 06) that in all probability corresponds to the deep-
est water column. The extant relatives of the clupeo-
morph, the characiform, and also all larvae and juveniles
however prefer shallow waters. The fossil community
preserved at the lake centre is therefore most likely a
Plate 3:
Fig. A: One leaflet of bifoliolate Aphanocalyx singidaensis (Herendeen & Jacobs 2000), Caesalpinioideae (Leguminosae), SSPP
MA-1956, pit 05d.
Fig. B: Leguminosae fruit (SSPP MA-274, pit 05c).
Fig. C: Single leaflet of unknown Caesalpinioideae (Leguminosae), SSPP MA-1113, pit 05d.
Fig. D: Bifoliolate leaf of “cf. Cynometra” (Herendeen & Jacobs 2000), Caesalpinioideae (Leguminosae), SSPP MA-1139, pit 05d.
Fig. E: Isolated Leguminosae leaflet, SSPP MA-1147, pit 05d.
Fig. F: Rachis with leaflets of Mimosoideae (Leguminosae), SSPP MA-1091, pit 05d.
Fig. G: A single-seeded segment of a Leguminosae fruit with insect damage (SSPP MA-258, pit 05c).
Tafel 3:
Fig. A: Einzelne Fieder eines doppelt gefiederten Blattes von Aphanocalyx singidaensis (Herendeen & Jacobs 2000), Caesalpinioi-
deae (Leguminosae), SSPP MA-1956, pit 05d.
Fig. B: Leguminosenfrucht (SSPP MA-274, pit 05c).
Fig. C: Einzelne Blattfieder eines unbekannten Vertreters der Caesalpinioideae (Leguminosae), SSPP MA-1113, pit 05d.
Fig. D: Doppelt gefiedertes Blatt von „cf. Cynometra“ (Herendeen & Jacobs 2000), Caesalpinioideae (Leguminosae), SSPP MA-
1139, pit 05d.
Fig. E: Isoliertes Leguminosen-Fiederblatt, SSPP MA-1147, pit 05d.
Fig. F: Rhachis mit Fiederblättern eines Vertreters der Mimosoideae (Leguminosae), SSPP MA-1091, pit 05d.
Fig. G: Einfrüchtiges Segment einer Leguminosenfrucht mit Fraßspuren von Insekten (SSPP MA-258, pit 05c).
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partly allochthonous taphocoenosis and the water body
above does not correspond to the habitat of all these fish-
es. The reduced number of specimens of the clupeo-
morph and of a small unnamed ostariophysan probably
reflects that they were not living in the water column, but
were transported into the central part of the lake during
their taphogenesis. This would also explain why the cich-
lids are most numerous, followed by the osteoglosso-
morphs, because the extant relatives of these taxa also in-
habit the open water column. These observations are
good evidence for the existence of a shallow water area in
the lake basin.
The first described species from Mahenge is the clu-
peomorph
Palaeodenticeps tanganikae
(Greenwood
1960).
Palaeodenticeps
is the fossil relative of extant
Denticeps clupeoides
; both are the only members of the
Denticipitidae, and of the Denticipitoidei. Due to the sim-
ilarities between the fossil and living species,
D. clupe-
oides
is regarded a living fossil. The Denticipitidae are
further interpreted as the sister group of the large subor-
der Clupeoidei. Besides the fossil specimens reported by
Greenwood (1960, 1968), the SSPP recovered a few
more that show differences to those described by Green-
wood and that are presently under description.
The second described species is the osteoglossomorph
Singida jacksonoides
, a sole member of its own family,
Singididae that was referred to the Osteoglossoidei by
Greenwood & Patterson (1967). Although recent phylo-
genetic studies placed
Singida
within the Osteoglossinae,
their sister group is still uncertain.
Singida
appears to be
the sister to the extant genera
Scleropages
and
Osteoglos-
sum
in Li et al.s (1997) cladogram, but it appears as the
sister of the extant genus
Pantodon
in Hilton’s (2003)
phylogenetic hypothesis.
Murray (2003a, b) described two ostariophysans from
Mahenge. One catfish, identified as a new species of
Chrysichthys
and a characiform, identified as a new ge-
nus and species,
Mahengecharax carrolli
. The assign-
ment to
Chrysichthys
is based, among other characters,
on the presence of long, thick pectoral and dorsal spines.
Numerous catfish specimens are represented in the new
material. Some of them have very long spines. Other
specimens with short spines (Plate 5: Fig. A), which do
not belong within
Chrysichthys
, are under study. In addi-
tion to the catfishes, the new material also comprises un-
described ostariophysans, not assignable to characiforms
or siluriforms.
Apparently, the dominant group populating the waters
at Mahenge were the cichlids (Plate 5: Fig. B). This as-
sumption is based on collections done by previous expe-
ditions (see Murray 2000a) and is confirmed by our ob-
servations based on the newly recovered material. The
Mahenge cichlids were originally identified (Greenwood
1960) as being similar to
Haplochromis bloyeti
(now in
the genus
Astatotilapia
). Later, Greenwood & Patterson
(1967) suggested that these fishes were similar to
Hemi-
haplochromis multicolor
(presently in the genus
Pseudo-
crenilabrus
). Greenwood (1974) identified these fishes as
Haplochromis
only. Recently, Murray (2000b) described
five new cichlid species from Mahenge that were includ-
ed in a new genus,
Mahengechromis
. The diagnostic
characters of the new genus are the distribution of ctenoid
and cycloid scales in certain body regions and the pres-
ence of unicuspid teeth in jaws and pharyngeal bones.
The five species are discriminated by the development
and shape of some cranial bones. Currently, they are in-
terpreted as the oldest known cichlids.
With over 1,300 extant species cichlids are distributed
in Africa, Central and South America, Madagascar, India,
Israel, Syria, Sri Lanka, and Iran (Nelson 1994). The ma-
jority have undergone radiations to form the species
flocks of the great lakes such as Lakes Victoria, Malawi,
and Tanganyika (e.g., Dominey 1984). Most previously
known fossil cichlids are represented by isolated bones or
Plate 4:
Fig. A: Leaf of Acacia mahengensis Herendeen & Jacobs 2000 (SSPP MA-1282, AHS at pit 05c).
Fig. B: Close-up of leaflet.
Fig. C: Undetermined Leguminosae (SSPP MA-2223), related to several isolated leaflets from the SSPP collection.
Fig. D: Undescribed frog of the family Pipidae (SSPP MA-753, pit 05d). The specimen shows pronounced adaptations to aquatic
life.
Figs. E, F: Scarabaeid beetle in dorso-ventral compression (SSPP MA-811, pit 05d). Note the excellent preservation of wing vena-
tion and legs.
Tafel 4:
Fig. A: Blatt von Acacia mahengensis Herendeen & Jacobs 2000 (SSPP MA-1282, AHS, pit 05c).
Fig. B: Nahaufnahme der Blattfieder.
Fig. C: Unbestimmte Leguminose (SSPP MA-2223); ähnlich verschiedenen isolierten Blattfiedern aus dem SSPP-Material.
Fig. D: Unbeschriebener Frosch aus der Familie der Pipidae (SSPP MA-753, pit 05d). Das Tier zeigt ausgeprägte Adaptationen an
das aquatische Leben.
Figuren E, F: Käfer aus der Familie der Scarabaeidae (Blatthornkäfer) in dorso-ventraler Einbettung (SSPP MA-811, pit 05d).
Außergewöhnlich ist die exzellente Erhaltung von Flügelnervationen und Beinen.
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largely incomplete specimens only (e.g., Greenwood
1957, 1960, 1972, Van Couvering 1977 for Africa, and
Casciotta & Arratia 1993 for South America). Due to the
number of species at Mahenge, Murray (2000b) proposed
that five fossil cichlid species could have been a species
flock. This hypothesis is interesting as it suggests that the
present diversity of cichlids in certain African lakes is not
a recent phenomenon, but also occurred in the oldest so
far known Cichlidae from the Eocene of Mahenge. Since
Mahenge is much smaller (0.2 km
2
proposed surface ar-
ea) than those modern African lakes containing species
flocks, e.g., Lake Victoria (app. 68,000 km
2
and 79 m
deep) and Lake Tanganyika (app. 32,800 km
2
and
1,435 m deep), we can assume that the diversity in differ-
ent habitat types in the Mahenge maar was probably
much smaller than that in the modern Rift Valley lakes.
Murray’s (2000b) hypothesis is based on the comparably
small number of described species and in the observation
that sympatric speciation also took place in small crater
lakes with limited diversity of habitat types (Schliewen et
al. 1994).
In the SSPP material there are also specimens with
ctenoid scales that differ from the typical cichlid mor-
phology. One of these has two dorsal fins separated by a
space; the anterior fin is spiny, while the posterior one is
preceded by a short spine. Another SSPP specimen has
ctenoid scales and differs from all other percomorphs col-
lected at Mahenge in its small size, moon-shaped body,
and very large scales.
In general the fishes from Mahenge represent a unique
phylogenetic puzzle bearing curious combinations of ple-
siomorphic and apomorphic characters. Traditionally,
this fauna would have been interpreted as endemic of
Mahenge. Based on the available information this inter-
pretation may be correct, but because the Eocene African
fish fauna is so poorly known yet, this hypothesis remains
to be tested, when hopefully more material from Ma-
henge and related fossil localities will be known in the
future.
5.4. The oldest known placental mammal of
Sub-Saharan Africa – a bat from Mahenge
The first Eocene Sub-Saharan mammal was discovered
July 24, 2000 at Mahenge pit 05, level 5 (stratigraphy af-
ter Harrison et al. 2001) by Mr. Charles Msuya. It is rep-
resented by the anterior half of a microbat skeleton (
Tan-
zanycteris mannardi
Gunnell et al. 2003) including skull,
lower jaws, vertebral column, both shoulder girdles and
humeri, and right ulna. The hind limbs and most of the
pelvis are missing (Plate 5: Fig. E).
T. mannardi
is a relatively small bat about the size of
Palaeochiropteryx tupaiodon
from the Middle Eocene of
Europe.
T. mannardi
retains a primitive axial skeleton
with unfused vertebrae throughout the column, has an ili-
ac blade that extends dorsally beyond the level of the ili-
osacral articulation, has a scapula with a double-faceted
infraspinous fossa, has a ventrolaterally curving coracoid
with a blunt tip, and has ribs with posterior laminae.
T.
mannardi
differs from all known comparable Eocene mi-
crobats (
Icaronycteris
,
Palaeochiropteryx
,
Archaeonyc-
teris
,
Tachypteron
, and
Hassianycteris
) in having a much
larger cochlear diameter relative to basicranial width. In
most other comparable features
T. mannardi
differs from
archaic microbats and is most similar to Old World rhino-
potamoids and rhinolophoids.
Features shared in common between rhinopotamoids
and
Tanzanycteris
include an enlarged cochlear fenestra,
a clavicle that articulates with the coracoid, and a trochit-
er that extends proximally well beyond the humeral head
(the latter two character states are shared with craseonyc-
terids only, not rhinopotamids). None of these shared
character states is exclusive to
Tanzanycteris
and rhino-
potamids suggesting that they may represent convergenc-
es or retention of plesiomorphic features. Character states
held in common between
Tanzanycteris
and rhinolo-
phoids include an extremely enlarged cochlea, having the
first rib broader than all other ribs, having a clavicle that
articulates with the coracoid, having a trochiter that ex-
Plate 5:
Fig. A: Partially disarticulated siluriform fish (SSPP MA-2222, pit 05).
Fig. B: Lateral view of a cichlid, Mahengechromis (SSPP MA-419, pit 05c).
Fig. C: A non-cichlid perciform (SSPP MA-1288, pit 05c).
Fig. D: Lateral view of an osteoglossomorph (SSPP MA-128, pit 05c).
Fig. E: The type specimen of the bat Tanzanycteris mannardi (Gunnell et al. 2003), pit 05a.
Tafel 5:
Fig. A: Teilweise disartikulierter siluriformer Fisch (SSPP MA-2222, pit 05).
Fig. B: Seitenansicht eines Cichliden, Mahengechromis (SSPP MA-419, pit 05c).
Fig. C: Ein nicht zu den Cichliden gehörender perciformer Fisch (SSPP MA-1288, pit 05c).
Fig. D: Seitenansicht eines Osteoglossomorphen (SSPP MA-128, pit 05c).
Fig. E: Das Typusexemplar der Fledermaus Tanzanycteris mannardi (Gunnell et al. 2003), pit 05a.
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tends proximally well beyond the humeral head, and in
having an iliac blade that flares dorsally resulting in a
well developed iliac fossa. Of these character states, the
presence of a broad first rib is uniquely shared between
Tanzanycteris
and rhinolophoids suggesting that
Tanzan-
ycteris
may be more closely related to this group than to
any other. Among the other characters shared in common
between
Tanzanycteris
and rhinolophoids, all but the flar-
ing iliac blade are shared with a variety of other extant
microbat groups (and several other Eocene taxa). The
flaring iliac blade with a well developed iliac fossa is
likely plesiomorphic for bats. It is possible that
Tanzan-
ycteris
represents a relatively primitive ancestral rhinolo-
phoid but the balance of its other character states aligns it
with the middle Eocene Messel Hassianycteridae.
The extremely enlarged cochlea indicates that Tan-
zanycteris had developed sophisticated echolocation abil-
ities. No other known Eocene microbat has as enlarged a
basal turn of the cochlea as Tanzanycteris. Among extant
forms only rhinolophids and one mormoopid (Pteronotus
parnellii) have comparable cochlear enlargement. These
extant bats are characterized by “High Duty Cycle Con-
stant Frequency Echolocation” in which the pulse and
echo are separated in frequency rather than time. The ma-
jority of extant microbats use low duty cycle echoloca-
tion, a system in which emitted pulses and returning ech-
oes are separated in time. Bats that use the high duty
cycle system can forage for fluttering insects in dense
forest close to vegetation or the ground. This behaviour
is beyond the limits of most low duty cycle echolocating
bats.
While the discovery of Tanzanycteris is interesting
and important for bat palaeobiogeography, the ramifica-
tions of the first mammal found in the Eocene of Sub-Sa-
haran Africa go far beyond the origin and diversification
of Chiroptera. Except for a few places, the early Cenozo-
ic mammalian fossil record of Gondwanan (southern)
continents is poor. The early Tertiary record of mammals
is almost completely unknown from the African conti-
nent except for isolated sites in Egypt, Morocco, Tunisia,
Libya, Senegal, Ethiopia, and Algeria (Arambourg &
Magnier 1961, Savage 1969, 1971, Sudre 1979, Coiffait
et al. 1984, Mahboubi et al. 1986, Sigé et al. 1990, Si-
mons 1992, 1995, Godinot & Mahboubi 1992, 1994,
Gheerbrant et al. 1993, 1998, Godinot 1994, Gheerbrant
1995, Hartenberger et al. 2001, Kappelman et al. 2003).
Other than the Fayum in Egypt, Bassin d’Quarzazate in
Morocco and recently described material from Chilga in
Ethiopia (Kappelman et al. 2003, Sanders et al. 2004),
mammal specimens from these various localities are rep-
resented only by isolated teeth and dental fragments.
The earliest known records of African Paleogene
mammals are from the late Paleocene of Morocco and
represent an interesting mix of African endemic species
with some immigrant taxa that share commonalities with
European groups. There are scarce Early Eocene faunal
samples from Chambi in Tunisia and Morocco that are
dominated by African endemic taxa. Poorly described
faunas from Algeria and Egypt represent all that is known
of Middle Eocene African faunas, while good records of
Late Eocene and Oligocene mammals are known from
several areas in northern Africa and from Chilga in Ethio-
pia. Nearly all African localities of Early Paleogene age
are in the North and were situated along the southern
shoreline of the ancient Tethys seaway. Only Mahenge
and Rukwa Valley in Tanzania and Chilga in Ethiopia of-
fer opportunities to examine what interior continental
vertebrate faunas may have been like. Much of the vast
African continent remains unsampled during the crucial
interval when archaic mammalian faunas were giving
way to more modern mammals.
The phylogenetic and geographic origins of most
modern mammalian groups remain a mystery. While Asia
and Indo-Pakistan have been suggested as possible places
of origin for many, or most, modern mammalian orders
(Krause & Maas 1990, Beard 1998), Africa remains a vi-
able alternative for the geographic origin of at least some
of these groups. In fact, it has been suggested that mod-
ern bats and anthropoid primates may both have originat-
ed in Africa. However, with the exception of the samples
from the late Paleocene in Morocco, the African mamma-
lian record is dominated by taxa already too derived to
have been ancestral to or stem taxa of most modern
groups of mammals. The lack of Paleocene and Early to
Middle Eocene samples from nearly all of Africa prohib-
its analysis of Africa’s possible role in origination of
modern mammals. The importance of discovering new
localities in Africa that represent this important interval
in mammalian evolution cannot be over-stated.
6. Temporal and biogeographic
significance of the Singida Diatremes
The maar lakes of the Singida Region (Fig. 1) offer the
first opportunity to collect an Eocene fauna and flora
from the interior of Africa. When more remains of mam-
mals are found at Mahenge and other Singida crater
lakes, they will provide evidence that may impact a
number of long-standing issues including: the origin and
diversification of several modern orders of mammals, the
extent and development of African mammalian ende-
mism, the implications of Afrotheria (Murphy et al.
2001), and the origin of anthropoid primates and modern
bat families.
A marginal aspect of discovering new Paleocene and
Eocene localities in interior Africa involves the origin of
the unique flora and fauna present on Madagascar today.
The island of Madagascar was in contact with the African
mainland until, at least, the Early Cretaceous (Krause &
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Maas 1990) and did not reach its present position until
the Late Cretaceous. During the time that Madagascar
was contiguous with the African continent it was an ex-
tension of what is now Tanzania. Therefore it is almost
certain that the mammals and cichlid fishes present on
Madagascar today shared common ancestry with groups
that would have lived in what is now Tanzania in the Late
Cretaceous. If evidence of common ancestry can be
found in the Eocene of Tanzania and surrounding areas,
the origin of some Malagasy vertebrate groups may be-
come better known.
Until recently, there was almost no strong evidence
that would indicate the potential place of origin for the
Malagasy biota, although Africa (Krause & Maas 1990)
or the Indian subcontinent (Marivaux et al. 2001) were
viewed as possible sources. Seiffert et al. (2003) reported
the discovery of the earliest known strepsirhines primates
(in this case lorises and galagos) from Bartonian (Late
Middle Eocene) sediments in Egypt. Strepsirhines still
live on the African mainland while some groups of strep-
sirhine primates only live on Madagascar today. The dis-
covery of strepsirhines from the Late Middle Eocene of
Egypt suggests that additional evidence from other local-
ities of similar age and older sediments may help to clari-
fy the ultimate origin of this group and also to elucidate
the patterns of faunal interchange that produced the con-
figuration of strepsirhine distribution now present in Afri-
ca and Madagascar.
The role that Africa played in the origin and diversifi-
cation of modern mammalian groups has been given little
serious attention, partly because only little evidence has
been available predating the Late Eocene and from areas
other than those that bordered the ancient Tethys seaway.
The expansion of the African fossil record both temporal-
ly and geographically is the only way to gather additional
evidence that will impact on origination theories. The
same significance applies to the fish fauna and the flora of
Sub-Saharan Africa. Hypothesised divergence times and
biogeographic histories based upon molecular phyloge-
netic studies can only be tested by fossils. The African
maar lakes of the Singida Region offer the potential to
provide much data on Eocene African vertebrates and
plants from interior regions of Sub-Saharan Africa. It is
probable that Africa was a source area for some modern
mammalian groups and plant taxa, but this will not be
known until the African record is much better sampled.
7. Acknowledgements
We gratefully acknowledge the community of Mwaru vil-
lage (Tanzania) in particular all those who worked with us
on the SSPP excavation at Mahenge. We also wish to thank
the local authorities of Singida Region, the Tanzanian
Commission of Science and Technology (COSTECH, Dar-
es-Salaam), the Director of Antiquities (Dar-es-Salaam),
and Mr. Ferdinand Mizambwa (Antiquities Department,
Dar-es-Salaam). We gratefully thank Gerd Alberti and Pe-
ter Michalik (Greifswald) for sharing 8 phantastic weeks
of field work with ES, CM, VB and TMK. Herbert Lutz
(Mainz) is gratefully acknowledged for his helpful com-
ments on an earlier version of this manuscript, and Chris-
toph Zahn (Hamburg) for editorial assistance. We thank
the Deutsch Forschungsgemeinschaft for funding this re-
search (KA 1525 3/1, KA 1525 3/2, AR 275/10-1) and in
particular we wish to thank our sponsors, the companies
Heraeus Kulzer (Dormagen), Carl Zeiss (Wetzlar) und
ZSP Geodätische Systeme (Jena).
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430 Thomas M. Kaiser et al.
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411_432_Kaiser.fm Seite 432 Freitag, 15. Dezember 2006 9:32 09
... Biogenic, laminated maar lake sediments may store various environmental proxies and potentially provide annual records of temperature, seasonality and rainfall. Fossil Lagerstätten associated with maars are crucial for reconstructing past terrestrial biodiversity and the biogeography and evolutionary history of plant and animal groups (Kaiser et al., 2006;Lehmann and Schaal, 2012;Lutz et al., 2010;Rasser et al., 2013). Fossils preserved in maars cover a wide range of terrestrial life forms, from microscopic algae to articulated mammals and typically preserve minute anatomical structures, cuticle, insect colour and soft tissues as the result of burial in an anoxic environment (Kaiser et al., 2006;Lehmann and Schaal, 2012;Lutz et al., 2010;Rasser et al., 2013;Wuttke et al., 2015). ...
... Fossil Lagerstätten associated with maars are crucial for reconstructing past terrestrial biodiversity and the biogeography and evolutionary history of plant and animal groups (Kaiser et al., 2006;Lehmann and Schaal, 2012;Lutz et al., 2010;Rasser et al., 2013). Fossils preserved in maars cover a wide range of terrestrial life forms, from microscopic algae to articulated mammals and typically preserve minute anatomical structures, cuticle, insect colour and soft tissues as the result of burial in an anoxic environment (Kaiser et al., 2006;Lehmann and Schaal, 2012;Lutz et al., 2010;Rasser et al., 2013;Wuttke et al., 2015). ...
Article
This paper highlights the geology, biodiversity and palaeoecology of the Hindon Maar Complex, the second Miocene Konservat-Lagerstätte to be described from New Zealand. The Lagerstätte comprises four partly eroded maar-diatreme volcanoes, with three craters filled by biogenic and highly fossiliferous lacustrine sediments. The exceptionally well-preserved and diverse biota from the site is derived from a mid-latitude Southern Hemisphere lake-forest palaeoecosystem, including many fossil taxa not previously reported from the Southern Hemisphere. The most common macrofossils are leaves of Nothofagus, but the flora also includes conifers, cycads, monocots (such as Ripogonum and palms), together with Lauraceae, Myrtaceae and Araliaceae leaves and flowers. The small maar lakes were surrounded by Nothofagus/podocarp/mixed broadleaf forest growing under humid, warm temperate to subtropical conditions. The fossil fauna comprises insects in the orders Odonata, Hemiptera, Thysanoptera, Coleoptera, Diptera, Hymenoptera and Trichoptera, and the fish assemblage includes a non-migratory species of the Southern Hemisphere Galaxias (Galaxiidae) and a significant new record of the freshwater eel Anguilla (Anguillidae). The fossil assemblage also includes the first pre-Quaternary bird feathers from New Zealand and abundant coprolites derived from fish and volant birds, presumably waterfowl. Palynomorph analysis and a ⁴⁰Ar/³⁹Ar age of 14.6 Ma obtained from basanite associated with the maar complex indicate that the Hindon Maar Complex is of mid-Miocene age (Langhian; New Zealand local stage: Lillburnian). It thus provides a new and unique perspective on Neogene terrestrial biodiversity and biogeography in the Australasian region, around the end of the mid-Miocene thermal optimum and prior to late Miocene–Pleistocene climate cooling episodes when many warm-temperate and subtropical forest components became extinct in New Zealand.
... The NLR generated precipitation values were supplemented with an additional value based on leaf area analysis derived data by Jacobs and Herendeen (2004) and Kaiser et al. (2006), also from Tanzania (from the Lutetian). In locations where the final results are in the same geographical location, the reconstructions were averaged. ...
Article
Full-text available
The early Eocene (∼56-48 million years ago) is characterised by high CO2 estimates (1200-2500 ppmv) and elevated global temperatures (∼10 to 16°C higher than modern). However, the response of the hydrological cycle during the early Eocene is poorly constrained, especially in regions with sparse data coverage (e.g. Africa). Here we present a study of African hydroclimate during the early Eocene, as simulated by an ensemble of state-of-the-art climate models in the Deep-time Model Intercomparison Project (DeepMIP). A comparison between the DeepMIP pre-industrial simulations and modern observations suggests that model biases are model- and geographically dependent, however these biases are reduced in the model ensemble mean. A comparison between the Eocene simulations and the pre-industrial suggests that there is no obvious wetting or drying trend as the CO2 increases. The results suggest that changes to the land sea mask (relative to modern) in the models may be responsible for the simulated increases in precipitation to the north of Eocene Africa. There is an increase in precipitation over equatorial and West Africa and associated drying over northern Africa as CO2 rises. There are also important dynamical changes, with evidence that anticyclonic low-level circulation is replaced by increased south-westerly flow at high CO2 levels. Lastly, a model-data comparison using newly-compiled quantitative climate estimates from palaeobotanical proxy data suggests a marginally better fit with the reconstructions at lower levels of CO2.
... The NLR generated precipitation values were supplemented with an additional value based on leaf area analysis derived data by Jacobs and Herendeen (2004) and Kaiser et al. (2006), also from Tanzania (from the Lutetian). In locations where the final results are in the same geographical location, the reconstructions were averaged. ...
Preprint
The early Eocene (~56-48 million years ago) is characterised by high CO2 estimates (1200-2500 44 ppmv) and elevated global temperatures (~10 to 16°C higher than modern). However, the response 45 of the hydrological cycle during the early Eocene is poorly constrained, especially in regions with 46 sparse data coverage (e.g. Africa). Here we present a study of African hydroclimate during the early 47 Eocene, as simulated by an ensemble of state-of-the-art climate models in the Deep-time Model 48 Intercomparison Project (DeepMIP). A comparison between the DeepMIP pre-industrial simulations 49 and modern observations suggests that model biases are model- and geographically dependent, 50 however these biases are reduced in the model ensemble mean. A comparison between the Eocene 51 simulations and the pre-industrial suggests that there is no obvious wetting or drying trend as the CO2 52 increases. The results suggest that changes to the land sea mask (relative to modern) in the models 53 may be responsible for the simulated increases in precipitation to the north of Eocene Africa, whereas 54 it is likely that changes in vegetation in the models are responsible for the simulated region of drying 55 over equatorial Eocene Africa. There is an increase in precipitation over equatorial and West Africa 56 and associated drying over northern Africa as CO2 rises. There are also important dynamical changes, 57 with evidence that anticyclonic low-level circulation is replaced by increased south-westerly flow at 58 high CO2 levels. Lastly, a model-data comparison using newly-compiled quantitative climate 59 estimates from palaeobotanical proxy data suggests a marginally better fit with the reconstructions at 60 lower levels of CO2.
... It is noteworthy that the group is absent from the rich faunas from Gour Lazib (late early or early middle Eocene, Algeria), Chambi (late early or early middle Eocene, Tunisia), and Namibia (?Lutetian-Bartonian) (e.g., Pickford et al., 2008;Adaci et al., 2016). Proboscideans are also absent from the only two unambiguous middle Eocene continental mammalian sites in Africa, the faunas of Aznag in Morocco (Tabuce et al., 2005) and Mahenge in Tanzania (Kaiser et al., 2006). By contrast, the only two ?mid-Eocene ...
Article
A long hiatus encompassing most of the Eocene (end of the Ypresian to the early Priabonian) breaks up the proboscidean evolutionary history, which is otherwise documented by a rich fossil record. Only two post-Ypresian localities from West Africa (Mali and Senegal) have yielded scarce Moeritherium -like dental remains. Here, we study one of these remains from Senegal and name a new genus and species, Saloumia gorodiskii . This taxon, confidently mid-Lutetian in age, evokes Moeritherium and elephantiforms with its wrinkled enamel, lack of centrocrista, and strong lingual cingulum. However, due to its pronounced bunodonty, which departs from the bunolophodonty of both Moeritherium and elephantiforms, we cannot exclude the possibility that Saloumia documents an early experiment in dental diversity among Paleocene–Eocene proboscideans, without direct relationships with later proboscideans. UUID: http://www.zoobank.org/0b6b83f8-817d-498c-a672-8ffa8f81a978
... Actinistia, Amiiformes, Lepisosteidae) and the nascent diversification of the Teleostei, with early records of several teleost subgroups. Freshwater-fish fossils are rare in the aftermath of the K/Pg extinction event [except for the earliest record of the Claroteidae, †Nigerium gadense White, 1935 and †Nigerium wurnoense White, 1935(Longbottom, 2010] and the earliest and most renowned palaeontological locality after this event is the Mahenge site (Tanzania) of middle Eocene age (46-45 Mya), where fish fossils are abundant, well preserved and very diversified (Murray, 2000a;Kaiser et al., 2006) (Greenwood, 1960;Murray, 2000aMurray, , 2001bMurray & Wilson, 2005;Davis et al., 2013;Lavoué, 2016). In addition, other, often more-recent, Eocene localities in North Africa, such as the late Eocene Birket Qarun Formation, Fayum, Egypt (Murray et al., 2010), the middle Eocene Dur At-Talah site from Libya (Otero et al., 2015) and the late Eocene/Oligocene Jebel Qatrani Formation, Fayum, Egypt (Murray, 2004) have revealed the presence of a gymnarchid ( †Gymnarchus sp., 37 Mya), a claroteid ( †Nigerium tamaguelense Longbottom, 2010, 56-41 Mya), an alestid ( †Hydrocynus sp., 56-41 Mya; Hammouda et al., 2016), a latid ( †Lates qatraniensis Murray & Attia, 2004, 33.9 Mya), a channid ( †Parachanna fayumensis Murray, 2006, 37-36 Mya) and a freshwater clupeid ( †Chasmoclupea aegyptica Murray, Simons & Attia, 2005, 33 Mya) that seem to have no close relationship with the Afrotropical freshwater tribe Pellonulini and, possibly, remains of the catfish families Mochokidae and Schilbeidae, and Cichlidae along with remains of older but still living freshwater lineages, such as the Protopteridae and Polypteridae. ...
Article
The Afrotropics house a diverse freshwater ichthyofauna with > 3000 species, almost all of which are endemic. Recent progress in dated phylogenetics and palaeontology of several groups of Afrotropical freshwater fishes (AFFs) has allowed the testing of palaeoecology- and palaeogeography-based hypotheses explaining their early presence in Africa. Seven hypotheses were tested for 37 most-inclusive monophyletic groups of AFFs. Results indicated that ten lineages originated from direct, but asynchronous, marine-to-freshwater shifts. These lineages contribute < 2% to the current AFF species richness. Eleven lineages colonized the Afrotropics from the Orient after the Afro-Arabian plate collided with Eurasia in the early Oligocene. These lineages contribute ~20% to the total diversity. There are seven sister relationships between Afrotropical and Neotropical taxa. For only three of them (4% of the species diversity), the continental drift vicariance hypothesis was not rejected. Distributions of the other four younger trans-Atlantic lineages are better explained by post-drifting long-distance dispersal. In those cases, I discuss the possibility of dispersal through the Northern Hemisphere as an alternative to direct trans-Atlantic dispersal. The origins of ten AFF lineages, including the most species-rich Pseudocrenilabrinae (> 1100 species), are not yet established with confidence.
... In com-parison, Denticipitoidei is a younger group, with the oldest representatives- †Paleodenticeps tanganikae Greenwood, 1960 and †Paleodenticeps sp. (Fig. 6)-known from deposits in Mahenge, Tanzania, which are assigned an Eocene age (about 46 Ma; Harrison et al., 2001;Kaiser et al., 2006). Although gonorynchiforms were well represented in the Lower Cretaceous of the Neotropical region, being very abundant in Brazilian basins (for a review see Brito, Amaral, 2008), modern forms do not inhabit the Neotropical Region, except, perhaps, for Chanos, which has an Indo-Pacific distribution that extends from California to Ecuador (although this distribution may show strong periodic changes associated with the El Niño/La Niña currents). ...
Article
Full-text available
A morphological revision is presented here on the cohort Otomorpha, a clade currently interpreted as the most primitive among the large supercohort Clupeocephala. Otomorpha is a morphologically heterogeneous group represented by clupei forms , alepocephaliforms, and ostariophysans (gonorynchiforms, cypriniforms, characiforms, siluriforms, and gymnoti forms) that inhabit various marine and freshwater environments worldwide. Otomorphs have a long (ca. 145 Ma) and diverse fossil record. They are the largest fish teleostean clade worldwide, as well as the largest of the Neotropical Region. While molecular studies strongly confirm the monophyly of Otomorpha, most potential morphological synapomorphies of the group become homoplastic largely due to the peculiar morphological character states (either losses or transformations) present in alepocephaliforms. The fusion of haemal arches with their respective vertebral centra anterior to preural centrum 2 stands as an unambiguous synapomorphy of the clade. The ankylosis or fusion of the extrascapular and parietal bones, and silvery areas associated with the gas bladder are also interpreted as synapomorphies, although they are homoplastic characters mainly due to secondary losses or further transformations of the morphological features in the alepocephaliforms.
... Testudinid radiation, in contrast, would have benefitted by more open vegetation and seasonally dry climates that appear to have existed over several African regions (e.g. eastern, southwestern and northern Africa) in the Eocene (Gagnon 1997;Jacobs 2004;Kaiser et al. 2006;Scott et al. 2006). Cowling et al. (2005) proposed that Albany Thicket, a vegetation type centred in south-eastern South Africa, originated in the Eocene and expanded from the Mid-Eocene to form part of a global semi-arid tropical belt. ...
Article
Africa, inclusive of the West Indian Ocean islands, harbours 11 of the world’s 16 extant testudinid genera. Fossil records indicate that testudinids originated in Asia and dispersed first to North America and Europe (Early Eocene) and later to Africa (Late Eocene). We used mitochondrial (1870 bp) and nuclear (1416 bp) DNA sequence data to assess whether molecular data support the late cladogenesis of Southern African testudinid lineages. Our results revealed strong support for the monophyly of a clade consisting of Kinixys, the two Malagasy genera and four Southern African genera (Psammobates, Stigmochelys, Homopus and Chersina). Kinixys diverged from this clade in the Late Palaeocene, suggesting that testudinids occupied Africa at an earlier date than indicated by fossil records. The Southern African tortoises consist of three, strongly supported clades: Psammobates + Stigmochelys; the five-toed Homopus + Chersina; and the four-toed Homopus. Due to the paraphyly of Homopus, we propose the taxonomic resurrection of Chersobius for the five-toed Homopus species (boulengeri, signatus and solus). Cladogenesis at the genus level occurred mainly in the Eocene, with Chersina and Chersobius diverging in the Oligocene. The latter divergence coincided with species-level radiations within Homopus (areolatus and femoralis) and Psammobates (oculifer, geometricus and tentorius). Our phylogeny could not resolve relationships within Psammobates, indicating rapid speciation between the Late Oligocene and Early Miocene. The Chersobius species were the last to diverge in the Early to Mid-Miocene. By the Mid-Miocene, P. tentorius started to differentiate into four lineages instead of the three recognized subspecies: P. t. tentorius, P. t. trimeni and two P. t. verroxii subclades occurring north and south of the Orange River, respectively. Terminal radiations in several taxa suggest the existence of cryptic species and a more diverse tortoise fauna than currently recognized. Factors contributing to this diversity may include the early origin of African testudinids and climatic fluctuations over a heterogeneous landscape.
... At present there are almost no quantitative terrestrial temperature records for the early Eocene from 30 • N to 30 • S latitude. We have some hints from the late Paleocene (Head et al., 2009;Huber, 2009) and earliest Eocene (Jaramillo et al., 2010) that tropical conditions were significantly hotter than modern, but in general the early Eocene terrestrial tropics are almost terra incognita (Burnham and Johnson, 2004;Jacobs and Herendeen, 2004;Kaiser et al., 2006). For our analysis, we included one flora from Africa of middle Eocene age, to have at least some tropical information, but given that the early Eocene, as indicated by marine records, was likely somewhat warmer than the middle Eocene, the one tropical estimate shown here likely underestimates the true temperature. ...
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The early Eocene "equable climate problem", i.e. warm extratropical annual mean and above-freezing winter temperatures evidenced by proxy records, has remained as one of the great unsolved problems in paleoclimate. Recent progress in modeling and in paleoclimate proxy development provides an opportunity to revisit this problem to ascertain if the current generation of models can reproduce the past climate features without extensive modification. Here we have compiled early Eocene terrestrial temperature data and compared with climate model results using a consistent and rigorous methodology. We test the hypothesis that equable climates can be explained simply as a response to increased greenhouse gas forcing within the framework of the atmospheric component of the Community Climate System Model (version 3), a climate model in common use for predicting future climate change. We find that, with suitably large radiative forcing, the model and data are in general agreement for annual mean and cold month mean temperatures, and that the pattern of high latitude amplification recorded by proxies can be largely, but not perfectly, reproduced.
... Together, these fossils provide a remarkable window into a midlatitude, lake and forest ecosystem in the early Miocene of New Zealand. The diversity of taxa and quality of preservation confirms Foulden Maar as the first terrestrial Konservat-Lagerstätten in New Zealand, comparable with the well-studied Eocene to Miocene European maars of Eckfeld, Messel, Enspel and Randeck (Schaal & Ziegler 1992, Lutz et al. 2000, Poschmann et al. 2010 Table 1) and possibly to the Eocene Mahenge Maar in Tanzania (Kaiser et al. 2006). Recent research indicates that Hindon Maar, about 25 km from Foulden, might comprise a second New Zealand example (Kaulfuss & Moulds 2015). ...
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Lee, D.E., Kaulfuss, U, Conran, J.G., Bannister, J.M. & Lindqvist, J.K., August 2016. Biodiversity and palaeoecology of Foulden Maar: an early Miocene Konservat-Lagerstätte deposit in southern New Zealand. Alcheringa 40, xxx–xxx. ISSN 0311-5518. This paper highlights the biodiversity and palaeoecology of the 23 million year old Foulden Maar, the first Konservat-Lagerstätte deposit described from New Zealand and a key site for reconstructing early Miocene Southern Hemisphere terrestrial ecosystems. The 1000-m-diameter, ca 200-m-deep Foulden Maar volcanic crater lake was a closed system with anoxic bottom waters, capturing and preserving in exquisite detail organisms from the lake and adjacent rainforest. The fossils include numerous leaves, flowers with in situ pollen, fruits, seeds, fish and arthropods. Surrounding Foulden Maar was an evergreen, Lauraceae-dominated notophyll vine forest with a diverse understorey, lianes, epiphytes and mistletoes. Diverse pollination and seed dispersal modes are evident. Fish include larval to adult stages of articulated specimens of Galaxias, some with preserved soft tissue and a species of eel resembling Anguilla. The arthropod fauna comprises ca 20 families in the orders Araneae (spiders), Plecoptera (stoneflies), Odonata (dragonflies), Isoptera (termites), Hemiptera (true bugs), Diptera (true flies), Coleoptera (beetles), Trichoptera (caddis flies) and Hymenoptera (wasps, ants and bees), representing faunas typical of soil, leaf litter, forest floor or freshwater habitats. Many fossil taxa have close relatives in the extant New Zealand biota; others are now locally extinct. Coprolites containing quartz sands sourced from outside the lake indicate the presence of volant birds, presumably waterfowl. The Foulden Maar Lagerstätte is crucial for reconstructing Miocene lake and forest ecosystems in New Zealand, particularly the terrestrial arthropod component. Daphne E. Lee [[email protected]], Department of Geology, University of Otago, PO Box 56, Dunedin, New Zealand., Uwe Kaulfuss [[email protected]] and Jon K. Lindqvist, [[email protected]], Department of Geology, University of Otago, PO Box 56, Dunedin, New Zealand; John G. Conran [[email protected]], Australian Centre for Evolutionary Biology & Biodiversity and Sprigg Geobiology Centre, School of Biological Sciences, Benham Bldg DX 650 312, The University of Adelaide, SA 5005, Australia; Jennifer M. Bannister [[email protected]], Department of Botany, University of Otago, PO Box 56, Dunedin, New Zealand. © 2016 Geological Society of Australia Inc., Australasian Palaeontologists
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Foulden Maar, Waipiata Volcanic Field, New Zealand is a partly eroded maar–diatreme formed by phreatomagmatic eruptions c. 23 Ma. Its post-eruptive evolution is reconstructed by combining outcrop, drillcore and physical core rock properties with pollen data. Facies associations in a 190 m thick composite section of the central crater sediments record four depositional stages: (1) immediate post-eruptive deposition of collapsed crater wall and tephra ring material by subaqueous gravity flows; (2) re-deposition of tephra by hyperconcentrated to turbulent gravity flows in a steep-sided lake; (3) seasonally mediated background sedimentation with recurring gravity flows in a meromictic lake; and (4) diminishing turbidity currents under decreasing relief and biogenic sedimentation over c. 130 ka. Clasts in the basal crater fill represent accidental lithic clasts of primary ejecta and indicate eruption into a mixed hard-soft rock substrate. Foulden Maar represents a ‘classical’ lacustrine maar crater sequence and confirms generally similar post-eruptive processes and sedimentation patterns in enclosed, lacustrine maar basins.
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The homologization of cranial bones of actinopterygians with those of sarcopterygians based on the bone names established in human anatomy is favored in order to permit the building of phylogenetic relationship schemes beyond the taxonomic boundaries of osteichthyans (including tetrapods). The basic criterion of homology is that of evolutionary continuity which can best be accomplished by comparing closely related taxa within groups and basal taxa in sister groups. In actinopterygians, the terms parietal and postparietal bones have to replace the commonly used terms "frontal" and "parietal" bones for the two paired bones on the skull roof. The infraor-bital bone 1 of actinopterygians is homologous with the lacrimal bone and the infraorbital bone 3 of advanced actinopterygians with the jugal bone of sarcopterygians. Infraorbital bone 6 of advanced actinopterygians is the dermosphenotic bone. Dermosphenotic and supratemporotabular bones are the two bones lateral to the parietal and postparietal bones in basal osteichthyans. In the lower jaw, the dentosplenial bone of actinopterygians represents the dentary plus splenial bones of sarcopterygians. Many bones appeared independently in actino-pterygians and sarcopterygians; they are not strictly homologous, this should be expressed either in the form of ". . ." ("premaxilla" = a neomorph in actinopterygians) or by prefix of the group where it appears (actinistian orbitosphenoid). Recognition of homologies can change with the discovery of new basal taxa or with new inter-pretations of bones and their relationships to each other.
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Using the multiple tools available to support an online collaborative environment, we surveyed 62 morphological features from the hyoid arch and gill arches of 53 species of cypriniform fishes that matched those sampled in recent molecular
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Estimates of past precipitation are of broad interest for many areas of inquiry, including reconstructions of past environments and topography, climate modeling, and ocean circulation studies. The shapes and sizes of living leaves are highly sensitive to moisture conditions, and assemblages of fossil leaves of flowering plants have great potential as paleoprecipitation indicators. Most quantitative estimates of paleoprecipitation have been based on a multivariate data set of morphological leaf characters measured from samples of living vegetation tied to climate stations. However, when tested on extant forests, this method has consistently overestimated precipitation. We present a simpler approach that uses only the mean leaf area of a vegetation sample as a predictor variable but incorporates a broad range of annual precipitation and geographic coverage into the predictor set. The significant relationship that results, in addition to having value for paleoclimatic reconstruction, refines understanding of the long-observed positive relationship between leaf area and precipitation. Seven precipitation estimates for the Eocene of the Western United States are revised as lower than previously published but remain far wetter than the same areas today. Abundant moisture may have been an important factor in maintaining warm, frost-free conditions in the Eocene because of the major role of water vapor in retaining and transporting atmospheric heat.
The osteology of the three miniaturized African freshwater gonorynchiforms Cromeria nilotica, C. occidentalis and Grasseichthys gabonensis is investigated. We show that the two species of Cromeria, long considered to be subspecies, differ significantly in a number of characters. This has some consequences because all recent studies of the relationships of Cromeria were based only on C. occidentalis. We review previous osteological accounts of Cromeria and Grasseichthys and discuss the differences that we encountered in our material. In addition we re-evaluate the characters considered of phylogenetic importance for the placement of Cromeria and Grasseichthys among kneriids. We demonstrate that a surprisingly large number of these was based on misinterpretations of anatomical characters or was applied at the wrong level of inclusiveness. Cromeria nilotica, C. occidentalis, and Grasseichthys gabonensis share numerous developmental truncations, but no derived progressive characters, which makes it difficult to place them phylogenetically among kneriid gonorynchiforms. Grasseichthys is the most developmentally truncated of the three miniature species. In addition to bones that are absent in the two species of Cromeria (suprapreopercle, symplectic, ectopterygoid, hypural 6, scales), Grasseichthys lacks the premaxilla, coronomeckelian, urohyal, posttemporal, cranial rib, epineural and epipleural intermuscular bones, and the anterior most branchiostegal ray. We discuss characters that we think will be of significance in future studies on kneriid intrarelationships. Finally, we address the general issue that taxa that have undergone extreme reduction of body size, as the three miniature kneriids, frequently show severe developmental truncations that render it difficult to determine their phylogenetic position with confidence.
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The history of ostariophysan classification is summarized and it is noted that traditional concepts of relationships have never been supported by characters found to be unique to the taxa. We present a now hypothesis of relationships among four of the five major ostariophysan lineages: Cypriniformes, Characiformes, Siluroidei, and Gymnotoidei (Otophysi). Cypriniforms are the sister-group of the remaining three (Characiphysi), and characiforms are the sister-group of siluroids plus gymnotoids (Siluriformes). Placement of the Gonorynchiformes as the sister-group of the Otophysi is supported by additional evidence. Each of the five lineages is monophyletic. Analysis was concentrated upon species thought to be the least specialized within each lineage; choices of these species are discussed. Chanos is determined to be a relatively primitive gonorynchiform morphologically and the sister-group of all other Recent members of the order. Opsariichthys and Zacco are found to be morphologically primitive cypriniforms. We propose that a monophyletic group comprising the Citharinidae and Distichodontidae forms the sister-group of all other characiforms. Within the two families, Xenocharax is the least specialized. We suggest that Hepsetus, the erythrinids, and the ctenoluciids are more derived than the distichodontids and citharinids, and may form a monophyletic group within the characiforms. The traditional hypothesis that Diplomystes is the primitive sister-group of all Recent siluroids is substantiated. Our evidence suggests that Sternopygus is the most primitive gymnotoid morphologically; but rather than being the sister-group of all other gymnotoids, it is the primitive sister-group within a lineage called the Sternopygidae by Mago-Leccia. Previous explanations of otophysan distribution have been based on notions of relationships which are unsupported by the evidence presented herein. Our own analysis of relationships serves primarily to make clear the extent of sympatry, and therefore the probability of dispersal, among the major ostariophysan lineages. The extent of sympatry, together with the widespread distribution of ostariophysans, suggests that the group is older than previously supposed, and our hypotheses of relationships among the characiforms implies that many of the extent characiform lineages evolved before the separation of Africa and South America. Further understanding of ostariophysan distribution must await phylogenetic analysis within each of the five major lineages so that distributions linked with vicariance patterns and dispersal events can be sorted out.
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Fossil floras are an important source of quantitative terrestrial paleoclimate data. Many paleoclimate estimates are based on relationships observed in modern vegetation between leaf morphology and climate, such as the increase in the percentage of entire-margined species with increasing temperature and the increase in leaf size with increasing precipitation. An important question is whether these observed relationships are universal or regional; for example, recent stud- ies suggest that significant differences exist between floras from three domains: the Northern Hemi- sphere, New Zealand/Australia, and subalpine zones. Also, debate exists over which statistical models of modern data sets, univariate or multivariate, provide the most accurate estimates of pa- leoclimate. In this study, 12 foliage samples from living Bolivian forests are compared with data sets from different regions. Models based on data sets from North America and Japan, namely the Climate-Leaf Analysis Multivariate Program (CLAMP) data set of J. A. Wolfe, and from east Asia produce reasonably accurate estimates of temperature and precipitation, suggesting that the cli- mate-leaf morphology relationships for Bolivian vegetation do not differ significantly from those for Northern Hemisphere vegetation. The mean leaf size for a given mean annual precipitation is smaller than for a data set from the Western Hemisphere and Africa, but this difference is most likely due to different sampling methods. As for estimating climate from fossil floras, these results, along with the analysis of four other regional data sets, imply that the most accurate climate es- timates will be produced by the predictor data set with the most similar climate-leaf morphology relationships. Unfortunately, our present lack of understanding of why climate-morphology rela- tionships vary between the North America/Japan, New Zealand/Australia, and subalpine domains makes it difficult to identify data sets similar to paleofloras. Until we learn more, it is probably best to compare fossil floras to predictor data sets from the same domain. The performance of the var- ious statistical methods depends on the nature of the predictor data set. Multiple regression anal- ysis tends to produce the most accurate estimates for small data sets with a narrow range of en- vironmental variation that have similar relationships to the flora, and linear regression or canonical correspondence analysis for the larger and more varied CLAMP data set. If a similar predictor data set is not available, then nearest-neighbor analysis can still produce accurate paleoclimate esti- mates.
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This paper represents the first cladistic analysis of the interrelationships of all nominal fossil and living gonorynchiform genera. Gonorynchiformes is the basal group of the superorder Ostariophysi, and is confirmed as monophyletic on the basis of 12 synapomorphies. The Gonorynchiformes is be subdivided into two monophyletic suborders, Chanoidei and Gonorynchoidei. The Chanoidei includes the family Chanidae, which in turn includes the RecentChanosplus five fossil genera, grouped in two subfamilies: Chaninae ((Chanos+ †Tharrhias) + †Parachanos+†Dastilbe) and †Rubiesichthyinae(†Rubiesichthys+ †Gordichthys). †Aethalionopsisis the sister-group to the Chanidae. Gonorynchoidei includes two families Gonorynchidae and Kneriidae. Gonorynchidae is formed by (Gonorynchus, †Notogoneus) and four fossil taxa of uncertain definition and interrelationships: †Charitosomus, †Charitopsis, †Ramallichthys, and †Judeichthys. The last four genera were previously included in the families †Charitosomidae and †Judeichthyidae, which could not be supported as monophyletic in this analysis. Kneriidae consists of two subfamilies Phractolaeminae with one genusPhractolaemus, and Kneriinae which includes ((Kneria+Parakneria) + (Grasseichthys+Cromeria)), the latter two being paedomorphic forms. The Phractolaeminae and the Kneriinae are freshwater African taxa with no known fossil record. The order Gonorynchiformes is represented herein by 18 genera, extending back to the Early Cretaceous. More work is required to clarify the interrelationships of the Gonorynchidae and the paedomorphic characters that apparently played an important role in the evolution of this morphologically diverse group of fishes.