.Paleontology and Geology of Laetoli: Human Evolution in Context.Vertebrate Paleobiology and Paleoanthropology SeriesEdited by Eric DelsonVertebrate Paleontology, American Museum of Natural History, New York, NY 10024, USA delson@amnh.orgEric J. Sar pdf

Harrison Ed., Paleontology and geology of Laetoli: Human evolution in context Fossil hominins and the associated fauna, Vol.. Harrison Ed., Paleontology and geology of Laetoli: Human

Paleontology and Geology of Laetoli: Human Evolution in Context

Vertebrate Paleobiology and Paleoanthropology Series

Edited by

Eric Delson

Vertebrate Paleontology, American Museum of Natural History,

New York, NY 10024, USA delson@amnh.org

Eric J Sargis

Anthropology, Yale University New Haven, CT 06520, USA eric.sargis@yale.edu

Focal topics for volumes in the series will include systematic paleontology of all vertebrates (from agnathans to humans), phylogeny reconstruction, functional morphology, Paleolithic archaeology, taphonomy, geochronology, historical biogeography, and biostratigraphy Other fields (e.g., paleoclimatology, paleoecology, ancient DNA, total organismal community structure) may be considered if the volume theme emphasizes paleobiology (or archaeology) Fields such as modeling of physical processes, genetic methodology, nonvertebrates or neontology are out of our scope

Volumes in the series may either be monographic treatments (including unpublished but fully revised dissertations) or edited collections, especially those focusing on problem-oriented issues, with multidisciplinary coverage where possible

Editorial Advisory Board Nicholas Conard (University of Tübingen), John G Fleagle (Stony Brook University), Jean-Jacques Hublin (Max Planck Institute for Evolutionary Anthropology), Ross D.E MacPhee (American Museum of Natural History), Peter Makovicky (The Field Museum), Sally McBrearty (University of Connecticut), Jin Meng (American Museum of Natural History), Tom Plummer (Queens College/CUNY), Mary Silcox (University of Toronto).

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Paleontology and Geology

of Laetoli: Human Evolution

Springer Dordrecht Heidelberg London New York

© Springer Science+Business Media B.V 2011

No part of this work may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission from the Publisher, with the exception of any material supplied specifically for the purpose of being entered and executed on

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Cover illustration : Photograph of the L.H 4 (lectotype) mandible of Australopithecus afarensis superimposed on a

view of Laetoli Locality 10 (© and courtesy of Terry Harrison).

Printed on acid-free paper

Springer is part of Springer Science+Business Media (www.springer.com)

To Australopithecus afarensis for being there when it mattered

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Laetoli in northern Tanzania is one of the most important paleontological and logical sites in Africa It is renowned for the recovery of early hominin fossils belonging to

paleoanthropo-A afarensis and for the discovery of remarkably well-preserved trails of footprints of hominins

Given the significance of Laetoli for understanding and interpreting the evolutionary history of early hominins the author initiated long-term geological and paleontological investigations at Laetoli and at other fossil localities on the Eyasi Plateau The overall objectives of the project were to recover additional fossil hominin specimens and to obtain more detailed contextual information on the paleontology, geology, dating, and paleoecology

The field campaigns (1998–2005) have produced important original data on the fossil inins, their associated fauna, and the paleoecological and paleoenvironmental context The work presented here is the culmination of that research It represents the combined effort of a dedicated and experienced field crew who were responsible for collecting the fossils and sam-ples described and analyzed here, and subsequent research by a multidisciplinary team of international specialists

hom-The present volume focuses on the morphology, systematics and paleobiology of the fossil hominins and the associated invertebrate and vertebrate fauna The companion volume pro-vides an interdisciplinary perspective on the geology, geochronology, paleoecology, taphon-omy, paleobotany, and modern-day Serengeti ecosystem Together, these two volumes present

a comprehensive account of the geology, paleontology and paleoecology of Laetoli It is hoped that the research presented here will provide an important building block in a broader under-standing of early hominin evolution, faunal diversity and ecological change in East Africa during the Pliocene, and provide the basis for analyzing early hominin adaptation within the context of broader macroevolutionary models of speciation, diversification and extinction

A special thanks goes to all of the dedicated team members who participated in the tions to Laetoli that contributed to the recovery of the material discussed and analyzed here (they are identified individually in the introductory chapter in Volume 1) I am especially grateful to the graduate students (current and former) who participated in the project, often under difficult conditions, and I fully acknowledge their significant contributions to the suc-cess of the project The students who accompanied me into the field were as follows: E Baker,

expedi-S Cooke, C Fellmann, K Kovarovic, A Malyango, L McHenry, K McNulty, G Mollel, C.P Msuya, T Rein, C Robinson, L Rossouw, M Seselj, D Su, M Tallman and S Worthington

Of my former graduate students, Denise Su deserves special recognition for taking on the primary role of curating and cataloguing the Leakey and Harrison Laetoli collections at the National Museum of Tanzania in Dar es Salaam, as well as for her valuable assistance with logistics at Laetoli and in Dar es Salaam

I thank the Tanzania Commission for Science and Technology and the Unit of Antiquities

in Dar es Salaam for permission to conduct research in Tanzania Special thanks go to the late Norbert Kayombo (Director General), Paul Msemwa (Director), Amandus Kweka and all of the curators and staff at the National Museum of Tanzania in Dar es Salaam for their support and assistance I thank the regional, district and ward officers in Arusha Region for their support and hospitality I am grateful to the Ngorongoro Conservation Area Authority for permission

Preface

viii Preface

to conduct research in the conservation area Emin Korcelik and Naphisa Jahazi of Hertz

International in Dar es Salaam arranged the field transportation, and H Meghji and A Esmail

helped with logistical support in Dar es Salaam

Research at Laetoli benefited from the advice, discussion, help and support from

numer-ous individuals, especially the following: P Andrews, R Blumenschine, E Delson, A Deino,

P Ditchfield, C Feibel, S Frost, C Harrison, T.S Harrison, D M K Kamamba, O Kileo,

J Kingston, A Kweka, J LeClair, M G Leakey, S Mataro, G Ole Moita, E Mbua, L McHenry,

C P Msuya, C S Msuya, G Mollel, M Muungu, O Mwebi, J Pareso, C Peters, M Pickford,

K Reed, C Saanane, W Sanders, C Swisher, and S Waane Bill Sanders deserves special

mention for applying his exceptional talents to preparing and casting some of the Laetoli

specimens, as does Jen LeClair for her tireless efforts in helping to organize the collections and

entering data in the catalogue

I thank the curators and staff at the various museums and repositories for allowing me

access to archival materials, fossils and comparative specimens in their care These include:

National Museums of Tanzania, Kenya National Museum, American Museum of Natural

History, Natural History Museum in London, Humboldt-Universität Museum für Naturkunde

in Berlin, Eberhard-Karls Universitat Tübingen Institut für Ur- und Frühgeschichte und

Archäologie des Mittelalters and Institut und Museum für Geologie and Paläontologie

The following individuals provided critical comments and advice about the research presented

in this volume and its companion: A Alexandre, P Andrews, M Anton, M Avery, M Bamford,

F Bibi, L Bishop, R, Bobe, R Bonnefille, F, Brown, P Butler, C Crumly, A Deino, P Ditchfield,

P Duringer, M Erbajeva, R Evander, C Feibel, Y Fernandez-Jalvo, B Fine-Jacobs, L Flynn,

S Frost, T, Furman, J Genise, A Gentry, D Geraads, H Gilbert, U Goehlich, J.H Harris,

K Heissig, A Hill, P Holroyd, D Iwan, N Jablonski, J Kappelman, T Kaiser, R Kay,

J Kingdon, J Kingston, W Kimbel, J Knott, K Kovarovic, N Kristensen, O Kullmer, F de

Lapparent de Broin, M Lewis, N Lopez-Martinez, S Manchester, I MacDougall, L McHenry,

S McNaughton, K Metzger, P Meylan, C Mourer-Chauviré, R Oberprieler, E O’Brien,

D Parmley, M Pavia, C Peters, M Pickford, I Poole, B Ratcliffe, D Reed, K Reed,

W.J Sanders, M Sponheimer, D Su, Z Szyndlar, R Tabuce, P Tassy, B Tiffney, J van der

Made, A Vincens, C Ward, H Wesselman, E Wheeler, and A Winkler Special thanks go to

Terri Harrison, Chris Harrison and Leahanne Sarlo for their assistance with many aspects of

the editorial process I thank Eric Delson, Eric Sargis and the Editorial and Production team at

Springer, especially Tamara Welschot and Judith Terpos Fieldwork at Laetoli and subsequent

research was supported by grants from the National Geographic Society, the Leakey Foundation,

and the National Science Foundation (Grants BCS-0216683 and BCS-0309513)

Terry HarrisonNew York

3 The Lower Third Premolar of Serengetilagus praecapensis

(Mammalia: Lagomorpha: Leporidae) from Laetoli, Tanzania 55Alisa J Winkler and Yukimitsu Tomida

4 Macroscelidea 67Alisa J Winkler

5 Galagidae (Lorisoidea, Primates) 75Terry Harrison

6 Cercopithecids (Cercopithecidae, Primates) 83Terry Harrison

7 Hominins from the Upper Laetolil and Upper Ndolanya Beds,

Elina Hernesniemi, Ioannis X Giaourtsakis, Alistair R Evans,

and Mikael Fortelius

12 Equidae 295

Miranda Armour-Chelu and Raymond L Bernor

13 Suidae 327

Laura C Bishop

16 Amphibia and Squamata 467

Jean-Claude Rage and Salvador Bailon

17 Tortoises (Chelonii, Testudinidae) 479

Terry Harrison

18 Aves 505

Antoine Louchart

19 Beetles (Insecta: Coleoptera) 535

Frank-T Krell and Wolfgang Schawaller

20 Lepidoptera, Insecta 549

Ian J Kitching and S Sadler

21 Trace Fossils Interpreted in Relation to the Extant Termite Fauna

Research Centre in Evolutionary Anthropology and Palaeoecology,

School of Natural Sciences and Psychology, Liverpool John

Moores University, Byrom St, Liverpool L3 3AF, UK

L.C.Bishop@ljmu.ac.uk

Johanna P.E.C Darlington

University Museum of Zoology, Downing Street, Cambridge, CB2 3EJ, UK

jpecd2@cam.ac.uk

Reihaneh Dehghani

Department of Palaeozoology, Swedish Museum of Natural History,

Box 50007 S-104 05, Stockholm, Sweden

reihaneh.dehghani@nrm.se

Christiane Denys

Department of Systematics and Evolution – CP51,

UMR7205 CNRS: Origine structure & évolution de la Biodiversité,

MNHN, 55 rue Buffon, 75005, Paris, France

Department of Geosciences and Geography, University of Helsinki,

P.O Box 64 FIN-00014, Helsinki, Finland

mikael.fortelius@helsinki.fi

xii Contributors

Alan W Gentry

c/o Department of Palaeontology, Natural History Museum,

Cromwell Road, London, SW7 5BD, UK

alantgentry@aol.com

Ioannis X Giaourtsakis

Department of Geo- and Environmental Sciences, Section of Paleontology,

Ludwig-Maximilians-University of Munich, Richard-Wagner-Strasse 10,

D-80333 Munich, Germany

i.giaourtsakis@lrz.uni-muenchen.de

Terry Harrison

Center for the Study of Human Origins, Department of Anthropology,

New York University, 25 Waverly Place, New York, NY 10003, USA

Terry.harrison@nyu.edu

Elina Hernesniemi

Department of Geosciences and Geography, University of Helsinki,

P.O Box 64 FIN-00014, Helsinki, Finland

Institut de Génomique Fonctionnelle de Lyon, team “Evo-devo of vertebrate dentition”,

Université de Lyon, Université Lyon 1, CNRS UMR 5242, INRA, Ecole Normale

Supérieure de Lyon, 46 Allée d’Italie, 69364 Lyon cedex 07, France

antoine.louchart@ens-lyon.fr; a222313c@yahoo.fr

Jean-Claude Rage

Département Histoire de la Terre, CNRS UMR 7207, MNHN, CP 38,

8 rue Buffon, 75231, Paris cedex 05, France

jcrage@mnhn.fr

Chris A Robinson

Department of Biology, Bronx Community College,

2155 University Avenue, Bronx, NY 10453, USA

Museum of Paleontology, The University of Michigan, 1109 Geddes Avenue,

Ann Arbor, MI 48109, USA

wsanders@umich.edu

Wolfgang Schawaller

Staatliches Museum für Naturkunde, Rosenstein 1, D-70191, Stuttgart, Germany

wolfgang.schawaller@gmns-bw.de

xiii Contributors

awinkler@smu.edu

wwwwwwwwwwwwwwwwwwww

T Harrison (ed.), Paleontology and Geology of Laetoli: Human Evolution in Context Volume 2: Fossil Hominins

and the Associated Fauna, Vertebrate Paleobiology and Paleoanthropology, DOI 10.1007/978-90-481-9962-4_1,

© Springer Science+Business Media B.V 2011

Abstract Laetoli in northern Tanzania is one of the most

important paleontological and paleoanthropological localities

in Africa In addition to fossil hominins, there is a diverse

associated fauna The Laetoli fauna is important because

it serves as a key comparative reference for other

Plio-Pleistocene sites in Africa, it samples several time periods

that are generally poorly represented at other

paleontologi-cal sites in East Africa, and it provides key insights into the

faunal and floral diversity during the Pliocene As a result

of renewed fieldwork at Laetoli (1998–2005) more than

25,000 fossils have been collected, of which more than half

are fossil mammals Most of the fossils were recovered from

the Upper Laetolil Beds (3.6–3.85 Ma), but smaller samples

came from the Lower Laetolil Beds (3.85–4.4 Ma) and Upper

Ndolanya Beds (2.66 Ma) These include new specimens of

Australopithecus afarensis from the Upper Laetolil Beds and

the first finds of fossil hominins from the Upper Ndolanya

Beds, attributable to Paranthropus aethiopicus Inferences

about the paleoecology at Laetoli are important for

under-standing the possible range of hominin habitat preferences

and ecological change in East Africa during the Pliocene

The evidence from a wide range of analyses indicates that a

mosaic of closed woodland, open woodland, shrubland and

grassland dominated the paleoecology of the Upper Laetolil

Beds The region would have been dry for most of the year,

except for the possible occurrence of permanent springs along

the margin of the Eyasi Plateau and ephemeral pools and rivers

during the rainy season The paleoecological reconstruction

of the Upper Ndolanya Beds is more problematic because of

conflicting lines of evidence, but it is very likely that

condi-tions were drier than in the Upper Laetolil Beds with a greater

proportion of grassland, but that closed and open woodlands

were still a major part of the ecosystem

Keywords Pliocene • Laetolil Beds • Ndolanya Beds • Fauna

• Paleontology • Paleoecology

Introduction

Laetoli in northern Tanzania is one of the most important paleontological and paleoanthropological localities in Africa The site is well known for the recovery of fossils of the early

hominin Australopithecus afarensis, as well as trails of

hom-inin footprints The associated fauna from Laetoli is very diverse (Leakey and Harris 1987), with over 100 species of mammals identified, along with the remains or traces of fos-sil amphibians, reptiles, birds, insects, gastropods and plants

As such, it serves as a key reference fauna, one that is ably dated, for comparisons with other Plio-Pleistocene sites

reli-in Africa Equally importantly, the Upper Laetolil Beds (3.6–3.85 Ma) and Upper Ndolanya Beds (2.66 Ma) sample time periods that are generally poorly represented at other paleontological sites in East Africa, and the fossils from these stratigraphic units provides key insights into the faunal and floral diversity during the Pliocene Detailed informa-tion on the paleontological localities and geology at Laetoli

is presented in the companion volume (Harrison 2011a), but the essential information is summarized in Figs 1.1–1.5.Laetoli is unusual among sites in East Africa in the absence of sedimentological or paleontological evidence for extensive and/or permanent bodies of water, and in having

an inferred paleoecological setting that is less extensively wooded than its penecontemporaneous sites Given these distinctive characteristics of the paleoecology at Laetoli, the site provide an important building block for inferring the possible range of hominin habitat preferences and for under-standing ecological change in East Africa during the Pliocene and its impact on early human evolution As a con-sequence, the ecological context at Laetoli has been exten-sively investigated in the past (Leakey and Harris 1987; Andrews 1989, 2006; Cerling 1992; Andrews and Humphrey

1999; Musiba 1999; Kovarovic et al 2002; Kovarovic 2004;

Su 2005; Harrison 2005; Kovarovic and Andrews 2007; Kingston and Harrison 2007; Musiba et al 2007; Su and Harrison 2007, 2008; Andrews and Bamford 2008; Peters

et al 2008), and is a special focus of renewed investigations since 1998

T Harrison (*)

Center for the Study of Human Origins Department of Anthropology,

New York University, 25 Waverly Place, New York, NY 10003, USA

e-mail: terry.harrison@nyu.edu

Chapter 1

Introduction: The Laetoli Hominins and Associated Fauna

Terry Harrison

2 T Harrison

The Laetoli Fauna

During the course of renewed fieldwork at Laetoli, between

1998 and 2005, more than 25,000 fossils have been collected

(Table 1.1) These consist mainly of fossil mammals (58.1%),

but also include the remains of birds (4.9%), reptiles and

amphibians (1.9%), invertebrates (33.3%) and plants (1.8%)

(Table 1.2) Most of the fossil mammals were recovered from

the Upper Laetolil Beds, but smaller samples came from the

Lower Laetolil Beds and Upper Ndolanya Beds

Represen-tative fossil vertebrates were also recovered from the Olpiro

and Ngaloba Beds, but no systematic collections were made

from these stratigraphic units

Renewed investigations at Laetoli have led to the recovery

of additional fossil hominins (Harrison 2011b) These include

further specimens attributable to A afarensis from the Upper

Laetolil Beds, and provide the basis, along with other

previ-ously undescribed specimens, for a reassessment of the

mor-phology and evolutionary status of the A afarensis sample

from Laetoli In addition, two hominins were recovered from

the Upper Ndolanya Beds, and these represent the first

homi-nins from this stratigraphic unit A maxilla from the Upper Ndolanya Beds at Silal Artum (EP 1500/01) is important

because it represents the only specimen of Paranthropus aethiopicus recovered from outside the Turkana basin, and it

is among the oldest securely dated specimens definitively attributable to this taxon (Harrison 2011b)

The contributions in Leakey and Harris (1987) provided the last comprehensive account of the systematics of the Laetoli fauna Since that time, however, there have been major advances in our understanding of the systematics and paleobiology of late Miocene and Plio-Pleistocene faunas of Africa, as well as many reports of new localities and faunas Renewed investigations at Laetoli have allowed a thorough revision of the systematics of the Laetoli fauna, along with a greater emphasis on understanding the paleobiology of the fauna and its paleoecological implications All of the mammalian taxa have been restudied, with the exception of the Camelidae and Chalicotheriidae (their analysis is still ongoing) The faunal list now includes nine new species of mammals and six new species of invertebrates, all of which are described in this volume In addition, one new species of

Fig 1.1 A sketch map of the Eyasi Plateau showing the major rivers and villages, as well as the three main paleontological research areas: Laetoli, Kakesio and Esere-Noiti (see Figs 1.2 – 1.4 for detail of insets) (From Harrison and Kweka 2011 )

1 Hominins and Associated Fauna

ostrich, Struthio kakesiensis, has been named previously

(Harrison and Msuya 2005), based on new collections from

the Lower and Upper Laetolil Beds

Mary Leakey’s team did recover a small sample of fossil

vertebrates from the Lower Laetolil Beds at Kakesio early

in their campaign, but the most intensive phase of research

at the site took place in 1982, and as a result most of the

fossil material and geological information obtained were

not included in the Laetoli monograph (Leakey and Harris

1987) Harris (1987) published a brief summary of the

fauna from the Lower Laetolil Beds, but most of the

speci-mens remained undescribed The specispeci-mens have been

incorporated in the current studies of the fauna The new

collection of fossil mammals from the Lower Laetolil Beds

is small (n = 251 specimens), but with more intensive

pros-pecting, especially in the areas of Kakesio and Noiti, it would

be possible to recover a much larger sample Given the age

of the Lower Laetolil Beds (3.85–4.4 Ma), the fauna from these beds could be extremely important in the study of human evolution, because it samples the time period

between the last occurrence of Ardipithecus and the first appearance of Australopithecus The Lower Laetolil fauna now

includes 27 species of mammals (up from 18 in 1987) (Table 1.3)

It is dominated by bovids, equids and proboscideans Small mammals are rare, and there is a strong taphonomic bias in favor of large mammals Most of the mammalian taxa (78%) in the Lower Laetolil Beds also occur in the Upper Laetolil Beds, implying a strong biogeographic provincial-ity, despite the time difference (Table 1.3) However, sev-eral species occur in the Lower Laetolil Beds that are not

present in the Upper Laetolil Beds These include: Anancus kenyensis, Petromus sp., Heterocephalus manthii, aff

Fig 1.2 Map of the Laetoli area showing the main outcrops of the Upper Laetolil and Upper Ndolanya Beds and the paleontological collecting localities (From Harrison and Kweka 2011 )

4 T Harrison

Proteles, Aonyxini gen et sp nov., and possibly Gazella granti (Sanders 2011; Denys 2011; Werdelin and Dehghani

2011; Gentry 2011) Most of these are very rare taxa (just

one or a few specimens), with the exception of Anancus kenyensis.

There are now 85 species of mammals recorded from the Upper Laetolil Beds (compared with 71 in 1987) (Table 1.3) Including the Harrison and Leakey collections combined there are now over 18,000 mammal specimens known from the Upper Laetolil Beds (Table 1.3) The large mammal fauna

is dominated by bovids (34% of all mammal specimens), with

Madoqua avifluminis, Parmularius pandatus and Gazella janenschi being especially common (Gentry 2011) At most East African localities Neotragini are rare, whereas at Laetoli

Madoqua is the by far the most common bovid taxon

Giraffids, with three species of different sizes represented, are also quite common (6.3% of all mammal specimens) Micromammals are well-represented in the Upper Laetolil

Beds, especially the lagomorph Serengetilagus sis, which is the commonest species, occurring ubiquitously

praecapen-throughout the unit (Denys 2011; Winkler and Tomida 2011) However, there is a high likelihood that small species of

Fig 1.3 Map of the Kakesio area showing the main outcrops of the Lower Laetolil Beds and the paleontological collecting localities (grey shaded areas) (From Harrison and Kweka 2011 )

Fig 1.4 Map of the Esere-Noiti area showing the main outcrops of the

Lower Laetolil Beds and the paleontological collecting localities (grey

shaded areas) (From Harrison and Kweka 2011 )

1 Hominins and Associated Fauna

rodents are under-represented in the collections due to nomic and collecting biases (Denys 2011; Reed and Denys

tapho-2011) Primates, including hominins, are rare, and comprise less than 1% of the mammalian fauna (Harrison 2011b, c, d; Table 1.2)

Fossil mammals are also abundant in the Upper Ndolanya Beds, which are separated in time from the Upper Laetolil Beds by a hiatus of about one million years Forty-nine species

of mammals are currently recognized (up from 38 species in 1987) (Table 1.3) Of these, just over half of the species (53%) are shared with the Upper Laetolil Beds However, there is apparently a significant faunal turnover between these two units (between 3.6 and 2.66 Ma) Among the large

mammals, Eurygnathohippus aff cornelianus replaces Eurygnathohippus aff hasumense, and Ceratotherium simum, Metridiochoerus andrewsi, Giraffa pygmaea, and Camelus sp make their first appearance in the Laetoli fauna

(Armour-Chelu and Bernor 2011; Hernesniemi et al 2011; Bishop 2011; Robinson 2011) Several bovids also appear

for the first time, including Parmularius altidens, Parmularius parvicornis, Megalotragus sp., Tragelaphus sp cf T buxtoni and Antidorcus recki (Gentry 2011) Among the micromam-

mals Gerbilliscus winkleri replaces G satimani, and Thryonomys wesselmani appears for the first time (Denys

2011) There is also an important difference in the hominins,

with Australopithecus afarensis being replaced by Paranthropus aethiopicus (Harrison 2011b) A better under-standing of the ecological differences and changes in the community structure between the Upper Laetolil Beds and the Upper Ndolanya Beds should provide important clues to

Fig 1.5 Simplified stratigraphic scheme of Laetoli sediments showing

the main stratigraphic units (left) and the chronology (right, Ma =

mega-annum) (After Hay 1987 ; Ndessokia 1990 ; Manega 1993 ; Ditchfield

and Harrison 2011 ; Deino 2011 )

Table 1.1 Number of fossils collected 1998–2005

Specimen counts do not include fossils from the Olpiro or Ngaloba Beds

LLB Lower Laetolil Beds, ULB Upper Laetolil Beds, UNB Upper

Ndolanya Beds

a For more detailed information on fossil mammals see Table 1.2

b Includes bones and eggs, except for those assigned to Struthio

c Egg shell fragments of Struthio

d Mostly the remains of tortoises, but the count does include snakes,

lizards and amphibians

e Terrestrial gastropods (For more detailed data on specimen counts see

Tattersfield 2011 )

f Mainly consists of cocoons and brood cells of solitary bees, but also

includes casts of insects, termitaries, and brood cells of dung beetles

g Includes wood, twigs, leaves, and seeds (see Bamford 2011a, b )

Table 1.2 Number of specimens and the frequency of fossil mammals collected at Laetoli and other localities on the Eyasi Plateau from 1998

to 2005

Lower Laetolil Beds

Upper Laetolil Beds

Upper Ndolanya Beds

6 T Harrison

Table 1.3 List of the fauna from the main stratigraphic units at Laetoli

Schizonychini,

sp A

X

Coprinisphaera ndolanyanus

X

Coprinisphaera laetoliensis

X

Apicotermitinae indet.

Achatina (Lissachatina)

1 Hominins and Associated Fauna

Table 1.3 (continued)

Scincomorpha indet.

X

(sp A)

X

(continued)

8 T Harrison

Table 1.3 (continued)

pliocaenicus

X

X

Elephantidae Loxodonta sp cf

Loxodonta cookei

X

Hystrix makapanensis

Xenohystrix crassidens

1 Hominins and Associated Fauna

Table 1.3 (continued)

palaeo-X

Herpestes ichneumon

X

Helogale palaeogracilis

X

Potamochoerus afarensis

X (continued)

10 T Harrison

understanding the differentiation of the Paranthropus lineage

The mammalian fauna from the Upper Ndolanya Beds is

heavily skewed towards bovids (63.8% of all specimens),

especially medium- and large-sized alcelaphines, probably

as a consequence of an unusual combination of taphonomic

factors (Table 1.2) The other common species in the Upper

Ndolanya fauna is Serengetilagus praecapensis (17.4% of all

mammal specimens) (Table 1.2)

In addition to fossil mammals, study of the non-mammalian fauna and paleobotanical remains are essential for a complete

Table 1.3 (continued)

Kolpochoerus heseloni

Metridiochoerus andrewsi

X

Sivatherium maurusium

X

Brabovus nanincisus

X Alcelaphini, larger

sp indet.

Alcelaphini, small sp.

?

Megalotragus kattwinkeli or M

1 Hominins and Associated Fauna

understanding and appreciation of the biotic diversity and

paleoecology at Laetoli during the Pliocene These

investi-gations include the first detailed studies to be undertaken of

the fossil insects, gastropods, birds, lizards and snakes from

Laetoli (Krell and Schawaller 2011; Kitching and Sadler

2011; Tattersfield 2011; Louchart 2011; Rage and Bailon

2011) Research on the fossil ostriches and birds’ eggs has

already been published (Harrison 2005; Harrison and Msuya

2005) The contributions presented in this volume provide

the basis for a major systematic revision of the Laetoli

fauna, as well as a much better appreciation of the

paleobi-ology and paleoecpaleobi-ology The fossil wood and other

paleo-botanical remains, which provide important insights into

the paleoecology of Laetoli, are described in the companion

volume (Bamford 2011a, b; Rossouw and Scott 2011)

Paleoecology

A major focus of renewed investigations at Laetoli has been

on reconstructing the paleoecology (Harrison 2011e) Study

of the paleoecology provides critical evidence for

under-standing the context of early hominin evolution It also allows

researchers to pose important questions about hominin

habi-tat preferences, ecology and paleobiology, and to include

these data in larger-scale macroevolutionary models of

spe-ciation, biogeography, diversification and extinction With

these questions in mind, renewed work at Laetoli has

attempted to reconstruct the paleoecology using information

from a wide diversity of sources (i.e., modern-day

ecosys-tems, paleobotany, phytoliths, palynology, invertebrate and

invertebrate paleontology, stable isotopes, mesowear,

eco-morphology, and community structure analyses) (Andrews

et al 2011; Bamford 2011a, b; Rossouw and Scott 2011;

Kingston 2011; Kaiser 2011; Hernesniemi et al 2011; Harrison

Su 2011; Reed 2011; Reed and Denys 2011)

The geological and sedimentological evidence indicates

that the Laetoli area had a relatively low topography during

the Pliocene, with a gently undulating terrain There is

evi-dence of rivers and streams in the Upper Laetolil Beds,

prob-ably with a greater extent and capacity than the present-day

hydrological system, but these rivers only flowed during the

wet season, and were dry for most of the year (Ditchfield and

Harrison 2011) The watercourses originated in the volcanic

highlands about 20 km to the east, and flowed southwest

across the Laetoli area, and it is likely that they drained into

the developing Eyasi basin This network of watercourses

would have supported a complex vegetational mosaic,

includ-ing dense stands of riverine woodland and bushland

(Ditchfield and Harrison 2011) Ephemeral ponds and small

lakes would have dotted the landscape during the rainy

sea-son, but these would have dried up during the dry season There is no evidence of large permanent bodies of water in the Upper Laetolil Beds or Upper Ndolanya Beds, and this is consistent with the absence of aquatic and hydrophilic verte-brates (i.e., hippopotamids, crocodiles, turtles and fishes), with the exception of rare finds of anurans (Rage and Bailon

2011; Ditchfield and Harrison 2011) The paleoenvironment

of the Lower Laetolil Beds appears to have been similar to that of the Upper Laetolil Beds and Upper Ndolanya Beds, but there is better evidence of shallow pools and lakes Aquatic vertebrates are extremely rare in the Lower Laetolil Beds, but the fauna does include an otter and there is also

single confirmed specimen of Crocodylus Harris (1987) reported the presence of fish from the Lower Laetolil Beds, but this has not been confirmed, and their record has been removed from the revised faunal list (Table 1.3)

The very common traces of termite bioturbation, burrows

of solitary hymenoptera, and the occurrence of aestivating gastropods throughout the Laetoli sequence, all point to widespread paleosols that were well drained and free from inundation for much of the year It is very likely that run-off from the volcanic highlands would have continued year-round, with water flowing below the surface even during the dry season, just as it does today Presently, springs occur along the edge of the Eyasi escarpment where the Laetolil Beds interface with the underlying impervious Precambrian basement rocks, and these provide a permanent source of water for wildlife and the local inhabitants Given that simi-lar geomorphological and topographic features were in place during the Pliocene, it is likely that springs were present in the Laetoli area, and that these offered an important source

of water during the long dry season in what would otherwise have been a relatively dry and waterless terrain

Ash fall deposits periodically blanketed the Laetoli area, forming distinctive marker tuffs in the Upper Laetolil Beds These heavy inundations of carbonatite volcanic ash would have had an adverse effect on the local ecosystem, including burial of the ground vegetation and making standing bodies

of water toxic (Peters et al 2008) The subsequent formation

of calcretes and hardpans would have led to a landscape dominated by grasslands and open woodlands However, these periods of disruption were apparent relatively short-lived, and the climax vegetation would have quickly re-established itself The ash falls in the Lower Laetolil Beds were thicker and more frequent than in the Upper Laetolil Beds, and undoubtedly would have caused more dramatic short-term disruptions to the local ecosystem However, the greater degree of fluvial reworking and bioturbation of the Lower Laetolil Beds indicates that the sediments quickly formed weakly developed paleosols that could have supported rapid re-establishment of the climax vegetation

The paleobotanical evidence provides important clues to reconstructing the paleoecology at Laetoli The fossil wood

12 T Harrison

from the Lower Laetolil Beds at Noiti suggests that woodlands

and forest covered the lower slopes of the volcanic highlands

to the east of Laetoli, and that a mosaic of woodland, bushland

and wooded grasslands occurred more distally (Bamford

sug-gest a diverse flora, with vegetation that included forest and

woodland elements (Bamford 2011b) The study of the

phyto-liths indicates that grasses were common at Laetoli during the

Pliocene, but they were probably not the dominant vegetation

type (Rossouw and Scott 2011) The Lower Laetolil Beds

appear to have been deposited in a relatively mesic habitat

dominated by C3 grasses Conditions became drier during the

lower part of the Upper Laetolil Beds and more mesic

condi-tions prevailed again during the upper part, with a shift from

C3 dominated grasses to C4 dominated grasses The phytolith

evidence indicates that the paleoecology of Upper Ndolanya

Beds was one of relatively arid grasslands, dominated by C4

grasses

Studies of the stable isotopes, mesowear, bovid

postcra-nial ecomorphology, small and large mammal community

structure, and the bird fauna provide a picture of the Laetoli

paleoecology that is largely consistent with that of the

paleo-botanical evidence (Kingston 2011; Kaiser 2011; Bishop

et al 2011; Su 2011; Denys 2011; Hernesniemi et al 2011;

Louchart 2011; Kovarovic and Andrews 2011) The ecology

during deposition of the Upper Laetolil Beds was a

vegeta-tional mosaic with woodland, bushland and

grassland-savanna The ungulate fauna was dominated by browsers and

mixed feeders Such a fauna, especially that with a large

pro-portion of very large browsers (i.e., three species of giraffids,

several large bovids and suids, chalicotheres, Ceratotherium,

deinotheres), has no modern analogs, because there are no

present-day ecosystems, beyond tropical forests, that have

such a diverse guild of browsing herbivores There is some

evidence to suggest that conditions became slightly drier,

with a greater proportion of grassland and open woodland, in

the upper part of the Upper Laetolil Beds above Tuff 7 The

evidence from the fossil mammals consistently points to a

major shift in the Upper Ndolanya Beds to an ecosystem

dominated by grassland

Further important evidence about the paleoecology is

pro-vided by the fossil gastropods (Tattersfield 2011) These

indicate an abundance of woodland habitats throughout the

Upper Laetolil Beds, but again they suggest that conditions

became somewhat drier above Tuff 7 The gastropods from

the Upper Ndolanya Beds, in contrast to the evidence from

the fossil mammals, indicate that more mesic conditions

pre-vailed, with extensive woodlands, similar to the

paleoecol-ogy from the lower part of the Upper Laetolil Beds, which

were the most mesic part of the sequence A similar

conclu-sion can be inferred from the oxygen isotope data from

ostrich eggshell, which suggests that more mesic conditions

were present in the Upper Ndolanya Beds In addition, one of

the main differences distinguishing the rodent community from the Upper Ndolanya Beds in comparison with the Upper

Laetolil Beds, is the occurrence of Thryonomys (cane rat)

(Denys 2011) The extant species of Thryonomys live in

waterlogged valley bottoms and moist areas with reliable rainfall, where they specialize in feeding on coarse grasses and reeds (Kingdon 1997) Given that gastropods are highly sensitive indicators of the local ecology compared to most mammals, I am inclined to accept that the paleoecology of the Upper Ndolanya Beds was characterized by a greater extent of woodland than is indicated by the large mammal fauna It is possible that the paleoecological signal derived from the large mammals is influenced by taphonomic factors (i.e., a bias towards larger-bodied ungulates) or that a signifi-cant part of the large mammal community may be transitory

or migratory in nature, and therefore not reflective of the local ecology

The balance of the evidence would suggest that the ecology of the Upper Laetolil Beds was dominated by a mosaic of closed woodland, open woodland, shrubland and grassland It was certainly more densely wooded than the modern-day Laetoli ecosystem, which is dominated by grass-land and open woodland (Andrews et al 2011) Water was probably more abundant during the rainy season, judging from the size and frequency of watercourses and small-scale fluvial deposits, but the region would have been dry for most

paleo-of the year, except for the possible occurrence paleo-of permanent springs along the margin of the Eyasi Plateau The paleo-ecology of the Lower Laetolil Beds was probably quite simi-lar to that of the Upper Laetolil Beds There is evidence, however, of semi-permanent bodies of water, but generally the inferred ecology is one of a dry woodland and bushland, possibly representative of an ecosystem that was disturbed

by heavy inundations of volcanic ashes The paleoecological reconstruction of the Upper Ndolanya Beds is more prob-lematic because of the conflicting evidence derived from dif-ferent proxies However, it is very likely that conditions became drier than in the Upper Laetolil Beds, with a greater proportion of grassland, but that closed and open woodlands were still a significant part of the ecosystem

Acknowledgements A special thanks to all of the dedicated and resourceful team members who participated in the expeditions to Laetoli that contributed to the recovery of the material discussed and analyzed here This volume and its companion would not have been possible without them I would especially like to single out the following indi- viduals who were critical to the success of the field project: Amandus Kweka, Michael L Mbago, Charles P Msuya, Simon Odunga, Al Deino, Carl Swisher, Peter Ditchfield, Godwin Mollel, Lindsay McHenry, Craig Feibel, Moses Lilombero, Simon Mataro, Denise Su, Peter Andrews, Terri Harrison and Bill Sanders I thank all of the authors for their excel- lent contributions to this volume For those who got their chapters in on time I am especially grateful; to those who were late with their submis- sion, I hope that I am forgiven for the persistent nagging To the senior physical anthropologist that accused me of doing stamp collecting rather

1 Hominins and Associated Fauna

than science, I will let the content of this volume speak for itself I thank

the Tanzania Commission for Science and Technology and the Unit of

Antiquities in Dar es Salaam for permission to conduct research in

Tanzania Special thanks go to Paul Msemwa (Director), Amandus

Kweka and all of the curators and staff at the National Museum of

Tanzania in Dar es Salaam for their support and assistance Fieldwork at

Laetoli was supported by grants from the National Geographic Society,

the Leakey Foundation, and the National Science Foundation (Grants

BCS-0216683 and BCS-0309513) This chapter is dedicated to the

memory of the late Norbert Kayombo (former Director General of the

National Museums of Tanzania) for his unwavering support.

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Abstract New rodent specimens collected at Laetoli between

1998 and 2005 are described here The material allows

an updating and refinement of the previously published

taxonomic lists, especially those for the Lower Laetolil Beds

and the Upper Ndolanya Beds The increased number of

well-preserved cranial specimens allows the description of

several new species and a better appreciation of the size and

morphology of some Laetoli taxa compared to their southern

and eastern African counterparts This is especially the case

for Saccostomus, for which the fossil record has recently

been much improved The new species described here include

a small sciurid, two Gerbillinae, and a thryonomyid Some

species are newly recognized at certain localities, and

Aethomys and Petromus are recorded for the first time at

Laetoli The distribution and stratigraphic range for Pedetes

laetoliensis is extended, and it is now recorded in the Upper

Ndolanya Beds Similarly, Xerus janenschi is now identified

in the Laetolil Beds As in the previous study of the Laetoli

rodents, important differences in species composition and

diversity between the Upper Laetolil Beds and the Upper

Ndolanya Beds are confirmed These probably reflect

differences in landscape Compared to other Pliocene

assemblages, the Laetolil Beds are characterized by a very

unusual diversity of sciurids and the dominance of

Saccostomus and Pedetes, but otherwise they compare well

with other East African Mio-Pliocene rodent assemblages,

such as those from the Omo Valley and Lemudong’o The

Laetoli assemblages are distinct from those of Lukeino,

Chorora and Harasib 3, but could belong to the same faunal

unit as Ibole (Manonga Valley) They also differ in some

respects from those from Hadar and Pliocene South African

sites Few species are shared in common between the Laetolil

Beds and Upper Ndolanya Beds, but it is uncertain whether

this turnover is due to taphonomic or paleoclimatic factors

This contribution highlights the importance of Laetoli for

understanding rodent evolution, as well as for its geographic position at the crossroads between East and South Africa

Keywords Mammalia • Rodentia • East Africa • Pliocene

• Pleistocene • Taxonomy

Introduction

In Africa, small mammals represent about 80% of the modern biodiversity, and rodents alone constitute about the half of it Their role as primary consumers and forest regenerators make them important in ecosystems, and they are considered good indicators of habitat Due to their relatively small size, fossil rodents occur only in localized bone concentrations, and among the Pliocene sites of Africa there are few rodent faunas known The Laetoli rodents were initially collected during the 1938–1939 Kohl-Larsen expedition to the southern Serengeti, which formed the basis for Dietrich’s (1942) initial taxonomic study Subsequent collections by Mary Leakey (1974–1979) allowed a better documentation of rodent paleodiversity (Denys 1987a; Davies 1987) and situated the faunas in a well-constrained geochronological and stratigraphic context for the first time This led to an improved knowledge of rodent evolu-tion during the Plio-Pleistocene of East Africa, including a better appreciation of their relationships with South African faunas (Denys 1999; Denys et al 2003; Winkler et al 2010).Due to the peculiar sedimentary nature of the site, Laetoli

is characterized by remarkably well-preserved material, which allows the description of cranial and postcranial char-acteristics of the rodents Laetoli provides records of the first appearance data (FAD) of several rodent genera and, being located at the southern end of the Rift Valley, it is biogeo-graphically important Moreover, rodents are known both from the Laetolil Beds (lower and upper units) and the Upper Ndolanya Beds, which allows biostratigraphical compari-sons between the main stratigraphic units

We present here the results of a systematic study of new sil rodent material recovered by Terry Harrison’s teams during

fos-C Denys (*)

Department of Systematics and Evolution – CP51,

UMR7205 CNRS: Origine structure & évolution de la

Biodiversité, MNHN, 55 rue Buffon, 75005, Paris, France

e-mail: denys@mnhn.fr

Chapter 2

Rodents

Christiane Denys

T Harrison (ed.), Paleontology and Geology of Laetoli: Human Evolution in Context Volume 2: Fossil Hominins

and the Associated Fauna, Vertebrate Paleobiology and Paleoanthropology, DOI 10.1007/978-90-481-9962-4_2,

© Springer Science+Business Media B.V 2011

16 C Denys

the 1998–2005 field seasons at Laetoli The study includes the

description of new taxa and a reinterpretation of the

evolution-ary relationships of the fossil rodents from Laetoli

Material and Methods

Specimens were examined and illustrated using a Wild

Microscope fitted with a camera lucida Cranial and dental

dimen-sions were measured with Mitutoyo calipers (0.01 mm

preci-sion) Some specimens were prepared by R Vacant (Palaeon-

tology Laboratory at the MNHN) and by the author SEM images

of the teeth were taken by C Chancogne-Weber with a JEOL

45 at the Palaeontology Laboratory Univariate statistics were

performed using XLSTAT Software version 9 (Addinsoft)

Comparisons were made with the following reference

mammal collections: Paris, France (MNHN); Natural History

Museum, London, England (NHM); Zoologische Museum,

Berlin, Germany (ZMB); Zoologishe Museum für Naturkunde,

Bonn, Germany (ZFMK); Durban Science Museum, South

Africa (DM); Namibian Museum, Windhoek, Namibia (NM)

Tooth nomenclature follows Denys (1987a), and rodent

taxonomy follows that of Wilson and Reeder (2005)

Systematics

Suborder Anomaluromorpha Bugge, 1974

Family Pedetidae Gray, 1825

Pedetes laetoliensis Davies, 1987

(Fig 2.1, Table 2.1)

Springhares are quite numerous at Laetoli, with well-preserved skeletal material The specimens collected by Mary Leakey led Davies (1987) to describe a new species Among the diag-nostic characters were its small size, enlarged infraorbital foramen and the absence of cusps on the molars (Fig 2.1) The original type description did not list the provenance of the specimens, but Davies (personal communication) listed 35

individuals of Pedetes occurring at Locs 1, 2, 3, 4, 5, 6, 7, 8,

9, 9N, 9S, 10, 10W, 10E, 11, 13, 14, 15, 16, 19, 21 and 22 Davies (1987) mentions the occurrence of Pedetes cf sur- daster from the Late Pleistocene Upper Ngaloba Beds at Loc

2, but none from the Upper Ndolanya Beds However, Harris (1987) lists the species as occurring in the Upper Ndolanya Beds.Here, 75 additional specimens add to the number of

localities at which Pedetes occurs (see Appendix 2.1) The new remains come from Locs.1, 2, 4, 5, 6, 8, 9, 10E, 11, 13,

15, 21 and 22, and are derived from all horizons throughout

Table 2.1 Upper and lower toothrow length (mm) for the new Laetolil

Beds specimens of Pedetes laetoliensis Davies, 1987, compared with

the dimensions of the holotype (after Davies 1987 ) and representatives

of the two extant species

Fig 2.1 New specimens of Pedetes from Laetoli (a) right maxilla

with DP4-M3/ of P laetoliensis (EP 1994/00, Loc 5, Upper Laetolil

Beds); (b) right mandible with DP/4-M/3 of P laetoliensis (EP 1867/00,

Loc 2, Upper Laetolil Beds); (c) mandible of Pedetes sp with

DP/4-M/2 (EP 2196/00, Loc 7E, Upper Ndolanya Beds) Scale bar

in mm

2 Rodents

the Upper Laetolil Beds The dimensions of the upper and

lower toothrows of the new specimens are close to those of

the type series, but they display a great range of variability

(Table 2.1) This may be due to the difficulty in measuring

some isolated molars that have convex crowns and because

the occlusal surface of hypsodont molars changes in

dimen-sions during the course of wear The shape of the molars is

similar to the previously recovered material described by

Davies (1987: fig 6.29, p 176) (Fig 2.1) The molars are

characterized by bilobate crowns of nearly equal size and

proportions, which makes identification of serial position

difficult They all have high crowns and flat occlusal

sur-faces No traces of cusps are visible

The only other extinct species of Pedetes, P gracilis,

comes from Taung (Broom 1934: fig 5, p 476) Pedetes

gra-cilis has a longer molar row (12 mm) and is very similar to

the modern Pedetes caffer According to Broom (1934), the

differences between the species are the smaller size of the

fossil teeth, and the plates of the infolded enamel are nearly

parallel and less deeply folded than those in modern P

caf-fer Molars of P laetoliensis display deep folds and are not

fully parallel in comparison to P gracilis A pedetid indet is

mentioned briefly as occurring at Harasib, and probably

con-stitutes a new genus of the family (Mein et al 2000a) In

addition, a single incisor from Lukeino (Mein and Pickford

2006) is attributed to an indeterminate Pedetidae

Pedetes sp.

Only one specimen has been recovered from the Upper

Ndolanya Beds at Loc 7E during renewed fieldwork, while

Davies (personal communication) recorded its presence at

Loc 14 It is represented by a mandible with DP/4-M/2 (EP

2196/00) in a poor state of preservation (Fig 2.1) The length

of the DP/4-M/2 reaches 10.06 mm in EP 2196/00, which,

based on its small size, indicates the possible presence of

P laetoliensis in the Upper Ndolanya Beds Up to now no

Pedetes has been recovered from the Upper Ndolanya Beds

at Loc 18 The molars display no link between the two lobes

of the molars, and the first lobe of the P4 shows two

well-individualized and oblique cusps, which is considered a

juvenile feature

Family Sciuridae Fischer de Waldheim, 1817

Sciurid remains are quite abundant at Laetoli From the

Laetolil Beds three different taxa of sciurid were recognized

by Denys (1987a), a small Paraxerus sp (Locs 11 and 12),

a larger Xerus sp (Loc 9S), and Xerus cf janenschi (Loc 2)

The Upper Ndolanya Beds at Locs 7E and 18 have yielded

well-preserved remains of Xerus janenschi Newly recovered

cranial material allows us to refine the taxonomy of the

Laetoli squirrels, which can be distinguished on their molar

row size and dental criteria

Genus Paraxerus Forsyth Major, 1893

This taxon is characterized by a short zygomatic plate, complex upper molars with three clear re-entrant folds, lower teeth with central depression non-isolated and well-developed ectolophid When the lower molars have strongly marked cusps and non-flattened crowns during wear, one can attribute

the molars to Paraxerus rather than to Funisciurus Both

genera have a P3/

Paraxerus meini sp nov.

(Fig 2.2)Holotype: EP 2816/00, left mandible with P/4-M/3 (Fig 2.2)

Type locality: Laetoli Loc 5, Upper Laetolil Beds between Tuffs 3 and 5, Tanzania

Fig 2.2 Paraxerus meini sp nov upper and lower molars Top, EP

881/03 (paratype) (Loc 10E, Upper Laetolil Beds), left maxillary

frag-ment with P4/M1; below, EP 1250/03 (Loc.7E, Upper Ndolanya Beds),

right mandible with P/4-M/2 and EP 2816/00 (holotype) (Loc 5, Upper Laetolil Beds)

18 C Denys

Age and Horizon: Mid-Pliocene, Upper Laetolil Beds

(between Tuffs 3 and 7) and Upper Ndolanya Beds

Paratypes: EP 881/03 (Loc 10E), maxillary fragment

with P4-M1 (Fig 2.2) EP 2815/00 (Loc 5), right

man-dibular fragment with P/4-M/2 EP 1000/01 (Loc 11),

mandible with P/4-M/3 EP 4152/00 (Loc 8), right and left

hemi-mandibles with M/1-3 EP 1250/03 (Loc 7E), right

mandible with P/4-M/2

Referred material from Laetolil Beds (previously

identi-fied as Paraxerus sp indet by Denys 1987a): LAET

76-4121A, lower P/4; LAET 74-304, upper P4-M3/ (figured

in Denys 1987a, plate 6.2-1 p 123); LAET 76-4178, lower

P/4-M/1; LAET 76-4170, right mandible fragment with

P/4- M/3 (figured in Denys 1987a: plate 6.2-2, p 123)

Distribution: Localities 5, 8, 10E, 11, and 12 of the Upper

Laetolil Beds, and Loc 7E of the Upper Ndolanya Beds

Repository: National Museum of Tanzania, Dar es Salaam

Etymology: Named in honor of Pierre Mein, who has

described many new rodent species from the Miocene of

Europe and Africa

Measurements: Tables 2.2 and 2.3

Diagnosis: One of the smallest species of the genus

compared to modern Paraxerus Smaller than extant P

ochraceus, which is the smallest East African species, but

larger than P boehmi from Central Africa Bunodont, with

many supplementary cusplets in all parts of the molars,

more than in P ochraceus Less bunodont than modern P

ochraceus, P palliatus, P flavovittis, P cepapi

Characterized by lower molars with a very rectilinear,

long ectolophid associated with a mesoconid on M/1-2

Characterized by a transverse entolophid connected

directly to the anterior part of the hypoconid Differs from

Heteroxerus karsticus in its smaller size, and the absence

of a direct link between the entoconid and hypoconulid

Differs from P ochraceus from the Omo in the larger size

of the lower molars

Description and comparisons: During Mary Leakey’s

expeditions of 1975–1976 Paraxerus was recovered only from

Locs 11 and 12, and was represented by only three mandibular fragments and one maxillary fragment Here we add and figure additional material from Locs 5, 8 and 7E This rare squirrel at Laetoli is represented by a few mandibles and incomplete maxillae, but no other cranial fragments

The P3/ occurs in all specimens, but only an alveolus is found, so that the morphology of the tooth cannot be described All the preserved upper molars are heavily worn (Fig 2.2; see Plate 6.2 in Denys 1987a), but one can distinguish an anteroloph and a small posteroloph on P4/

A paraloph and metaloph are visible with the ment of a faint metaconule on the metaloph The hypo-cone is hardly visible and no mesostyle is seen in specimen LAET 74-304, but one is found in specimen EP 881/03

develop-On the upper M1 and M2 there are two well-developed parallel lophs A small anteroloph exists, but the conules are not visible due to wear The M3/ is present only on specimen LAET 74-304, but it is worn It has a triangular shape and it is smaller than M1-2/ Two lophs are visible

on M3/; the metaloph being reduced to a cusp in son to the protoloph

compari-On P/4 the cusps are bunodont and the protoconid and metaconid are nearly the same height The two cusps are united by a small crest issuing from the posterior part of the protoconid There is an ectolophid linking the protoconid to the hypoconid, and a small posterolophid No anterolophid is observed on P/4 On M/1-2 there is a small anterolophid and posterolophid with supplementary cusps (anteroconulid and hypoconulid) The ectolophid is well developed and longitu-dinal, with a slight mesoconid on M/1-2 The entolophid is well-developed and connects the hypoconid to the entoconid transversely with a very rectilinear crest On the entolophid

of M/1-2 there is one or two supplementary cusps On M/2 the entolophid is smaller than on M/1 and the anteroconulid and hypoconulid are less visible On M/3, which is narrow and elongated, the same structures are visible and the cusps are still distinguishable The anteroconulid is low and small The hypoconulid and posterolophid is absent on M/3 The

Table 2.2 Upper (UPTR) and lower (LTR) toothrow lengths (mm) for Paraxerus meini nov sp compared to modern Paraxerus species

P meini Laetoli (this work; Denys 1987a) 2 6.63 0.53 6.25–7.00 4 6.88 0.69 5.96–7.58

Sources: P ochraceus, Omo Member B, Wesselman (1984); H karsticus, Mein et al (2000a); Paraxerus sp., Kanapoi and Lemudong’o, Manthi

( 2006, 2007) Modern species (P ochraceus, P flavovittis and P cepapi) from museum collections

entoconid is small and oblique, delimiting the distal border

of the molar

Comparisons of molar size with various modern East

and South African Paraxerus species shows that

Paraxerus meini nov sp clearly has a smaller toothrow

length compared to modern P flavovittis, P cepapi and

P ochraceus, but larger than P boehmi There is marked

individual variability of molar size in the modern species

(Tables 2.2 and 2.3)

Comparison of the morphological features of the

molars with modern P ochraceus shows that P meini

shares well-developed lophs on the upper molars, the

presence of a metaconule on P4/, and no hypocone on

M3/ Lophs are less well developed in P palliatus and

P flavovittis, especially the ectolophid On the lower

molars one can see the anteroconulid and posteroconulid

on M/1-2 of P palliatus and P ochraceus, and the M/3 is

narrow and lacks a hypoconulid and discrete entoconid

It seems that P meini can be distinguished from P palliatus

and P flavovittis in having numerous supplementary

cusplets, less bunodont molars, and a better-developed

ectolophid Compared to P ochraceus there are fewer

supplementary cusplets and a more rectilinear ectolophid

with a mesoconid Paraxerus meini differs from P vittis in the presence of a hypoconulid and entoconulid

flavo-on M/1 and M/2 From a morphological point of view the

molars of P meini display some similarities with P ceus from Tanzania, being characterized by the develop-

ochra-ment of numerous cusplets, but they are expressed to a

greater extent in P meini This group is characterized by

marked molar size and shape variability, but cusp variability is not well known From the MNHN, NHM,

ZMB and DM voucher specimens examined, P meini has upper and lower toothrows intermediate in size between P boehmi and P ochraceus (Table 2.3)

The fossil record for this taxon is poorly known Only an

isolated tooth (left P/4) of Paraxerus sp has been discovered

at Lemudong’o (~6 Ma), which displays some similarity

with P palliatus (Manthi 2007) Compared to P meini, the

Lemudong’o P/4 has the same bunodont pattern with the two anterior cusps well separated Based on the published images

of the Lemudong’o specimen there is no ectolophid, contrary

to P meini, and no evidence of a posterolophid Another lower molar attributed to Paraxerus sp was described from

Tabarin (4.5–4.4 Ma) (Winkler 2002) Manthi (2006) mentions

a single mandible of Paraxerus sp from Nzube’s mandible

20 C Denys

site at Kanapoi, which has larger molars, similar to the

specimen from Lemudong’o (Table 2.3) From Omo

Members B, C and F, Wesselman (1984) described some

molars that he attributed to modern P ochraceus They

dis-play the same pattern as P meini: longitudinal rectilinear

ectolophid, presence of an entolophid on M/1-2, and

exis-tence of an anterolophid or an anteroconulid The difference

between the Omo P ochraceus and the modern species

relates to the oblique disposition of the protoloph originating

from the protocone in the fossil, while it is more transverse

and originates from the back of the molar in the modern

form The specimens from Omo and Laetoli probably belong

to the same lineage, and may be the ancestors of modern P

ochraceus The P meini specimens have larger molars

com-pared to modern representatives of the genus (Table 2.3)

The late Miocene site of Harasib in Namibia has yielded

the remains of a sciurid that is attributed to the extinct

European genus Heteroxerus (Mein et al 2000a) The

rea-sons why the Harasib squirrel is not attributed to Paraxerus

is not well justified, except for the smaller size of the

uni-cuspid P3/ in the Harasib material However, there is

extensive variability in the modern representatives, and

such a character is not adequate to reject a close

relation-ship between P meini and H karsticus The hypocone is

absent or small in H karsticus and there is some

variabil-ity described by the authors in the metaloph orientation

and disposition Heteroxerus karsticus has larger molars

than P meini The figured holotype of H karsticus

dis-plays a very longitudinal rectilinear ectolophid and there is

an anteroconulid on M/1-2 as in P meini The entolophid

is better developed and more transverse than in the Laetoli

specimens, while it is very reduced or absent in H

karsti-cus (Mein et al 2000a) When the entolophid is figured, as

in Fig 2.3, one observes that it is oblique and joins the

posterolophid midway along its length The genus

Heteroxerus was created by Stehlin and Schaub (1951) for the Miocene European H hurzeleri based upon the exis-

tence of a direct link between the entoconid and

hypoconu-lid, a feature that we do not find in Paraxerus meini or modern Paraxerus spp., but present on H karsticus at

Harasib (Mein et al 2000a) Stehlin and Schaub (1951) also mentioned the existence of the little arm of the proto-

conid, which is also found in modern Xerus spp., but not in the Paraxerus we examined Heteroxerus karsticus, as

described by Mein et al (2000a), also displays an

antero-conulid on M/1-2 that is found in P meini and in modern P ochraceus and P cepapi The diagnostic characters pro-

vided by Mein et al (2000a) indicate some differences between the two species and they probably represent dis-

tinct lineages Further revisions of Heteroxerus and Paraxerus species composition and diagnoses are required

to answer these questions

Genus Xerus Hemprich and Ehrenberg, 1833 Xerus janenschi Dietrich, 1942

(Figs 2.3–2.6)The largest sciurid from Laetoli is found as a common taxon in the Upper Ndolanya Beds, but it is represented only by a single specimen from the Upper Laetolil Beds (Denys 1987a) Dietrich (1942) described it for the first time from Garusi, but the stratigraphic provenance and age

is not known Denys (1987a) recognized the same species from Locs 18 and 7E from the Upper Ndolanya Beds

Fig 2.3 Dorsal and ventral views of Xerus janenschi cranium, EP

219/04 from Loc 15 (Upper Ndolanya Beds)

Fig 2.4 Scatter plot of modern and fossil Xerus specimens LP4-M3/: upper tooth row length LGT: total length of the cranium (axis scales in mm) ERY: modern Xerus erythropus from East and Central Africa

INAURIS : modern X inauris from South Africa JANENSCHI: Laetoli fossils, X janenschi PRINCEPS: modern Xerus princeps from south- west Africa RUTILUS: modern X rutilus from Ethiopia SP: Laetolil

Xerus sp DAAMSI: Fossil Chad KB, X daamsi

2 Rodents

Fig 2.5 Box plots for the different modern and fossil Xerus spp for

different cranial measurements (LP4-M3/: Upper tooth row length WNAS:

Nasal width LP/4-M/3: Lower tooth row length LNAS: Nasal length

LGT : Total cranium length) in mm ERY: modern Xerus erythropus from

East and Central Africa INAURIS: modern X inauris from South Africa

JANENSCHI : Laetoli fossils, X janenschi PRINCEPS: modern Xerus

princeps from southwest Africa RUTILUS: modern X rutilus from Ethiopia SP: Laetolil Xerus sp DAAMSI: Fossil Chad KB, Xerus daamsi

22 C Denys

Lacking P3/, no ectolophid and quite bunodont cusps,

Xerus janenschi shares dental and cranial characters with

X daamsi (Denys et al 2003) from the early Pliocene KB

site in Chad and with X erythropus from the Omo

(Wesselman 1984) The absence of P3/ distinguishes the

Laetoli fossils from the late Miocene Xerus sp from Alayla

Vertebrate Locality 2 in the Middle Awash of Ethiopia

(Wesselman et al 2009) A cladistic analysis comparing

the Laetoli fossil to modern Xerini indicates that its closest

affinities are with X rutilus (Denys et al 2003)

The new Laetoli material increases the sample of X

janenschi by 37 specimens (see Appendix 2.2) and

estab-lishes its presence for the first time in the Upper Ndolanya

Beds at Loc.15 and Silal Artum, as well as in the Upper

Laetolil Beds at Loc 9S The new specimens display the

same skull characteristics previously described for X

janenschi, including a short nasal, trace of three

transbul-lae septa, rather bunodont molars, the absence of P3/,

inflated tympanic bullae, and a wide braincase (Fig 2.3)

These characters allow X janenschi to be grouped closest

to the South African X inauris and X princeps However,

X janenschi is also characterized by distinctive skull

proportions (Table 2.4, Fig 2.4) At an equivalent cranial

size to X rutilus, X janenschi has longer upper and lower molar rows It is smaller than X daamsi, X princeps, X inauris and X erythropus The nasals of Xerus janenschi

are intermediate in length-width proportions between the

smallest X rutilus and X daamsi and the other modern

species, which are larger (Table 2.4, Fig 2.5)

There is great variability within this species in terms of size, but the dental morphology of the newly collected fossils

is similar to the type material and displays a very bunodont pattern (Fig 2.6) The new material confirms that X janenschi has larger molars than X daamsi from Chad and Xerus sp from Kanapoi, and smaller molars than those of X cf inauris

from Olduvai Bed I (Table 2.5) However, they fall within the lower end of the range of variability for the Olduvai and Omo samples (Table 2.5)

Table 2.4 Skull and molar dimensions (mm) in fossil and modern

nasal length and width, LP4/-M3/ upper tooth row length, P/4-M/3,

lower tooth row length Modern X inauris, X princeps, X rutilus,

X erythropus specimens have been measured in museum collections

Data for X daamsi from Denys et al (2003 )

Fig 2.6 Lower (left) and upper (right) toothrows of Xerus janenschi

EP 292/04 (mandible with P/4-M/2) from Loc 18 (Upper Ndolanya

Beds) and EP 2356/98 (maxilla with P4-M3/) from Loc 18 (Upper

Ndolanya Beds) Scale bar indicates 1 mm

2 Rodents

Xerus sp.

(Fig 2.4, Table 2.5)

The Upper Laetolil Beds have also yielded the remains

of a smaller sciurid This species is very bunodont and

was described and figured by Denys (1987a) from Loc

9S (LAET 75-1562, Plate 6.2) and possibly includes the

Gadjingero 100 skull (from the Kohl-Larsen collection

in Berlin) New specimens from Loc 9 (EP 1089/98) and Loc 9S (EP 1215/04) can be attributed to this same spe-cies The entoconid and posterolophid are very cresti-form on P/4, M/1, and M/2, and they make a continuous distal wall on M/2 There is no prominent entoconid and the cusp relief is low These features are similar to modern

Table 2.5 Tooth dimensions (N number of specimens, SD standard deviation) for fossil and modern Xerus spp Laetoli UNB 1987 and this work relates to X janenschi

Data sources: Olduvai Bed I, X cf inauris, Denys (1990); Omo B, C, Xerus erythropus, Wesselman (1984); Omo F, Xerus sp., Wesselman (1984 );

KB-97-162, Chad, Xerus daamsi, Denys et al (2003); Kanapoi, Xerus sp., Manthi (2006 ) Abbreviations: UNB, Upper Ndolanya Beds; LB, Laetolil Beds

a Attribution to M1 or M2 is ambiguous DP/4 and P/4 have been pooled, which may explain the high variability observed for these teeth

24 C Denys

X rutilus (Denys et al 2003) The specimens display a

shorter skull length, relatively longer upper molar row

(Fig 2.4) and smaller lower molars than X janenschi

(Tables 2.4 and 2.5), although measurements of some

teeth fall in the low end of the range of X janenschi.

Family Nesomyidae Major, 1897

Subfamily Cricetomyinae Roberts, 1951

Tribe Saccostomurini Roberts, 1951

Genus Saccostomus Peters, 1846

Saccostomus major Denys, 1987

(Figs 2.7–2.12)

Many new specimens from the Upper Laetolil Beds (Locs 1, 2,

3, 4, 5, 6, 7, 8, 9S, 10, 10E, 10W, 11, 15, 17 and 22) are

attrib-uted to S major (see Appendix 2.3) They display the same

morphological characteristics of the teeth as the previously

recovered material (Fig 2.7) The initial description of the

species included nearly complete skulls, and there are no new

skeletal elements to describe here However, with the recovery

of 173 new Saccostomus individuals from the Upper Laetolil

Beds we have been able to study the population at a finer scale

M/1 length and wear stages were analyzed to assess the

vari-ability among the species and to detect biostratigraphic

differences

The following wear stages can be defined (Fig 2.8):

Stages 0–1: Presence of two isolated cusps on the prelobe of

M1/1 or M3/ unerupted

Stages 2–4: Cusps visible on all the molars, no large

longitu-dinal links between cusps visible

Stages 5–6: Wide links between the lobes and cusps hardly

visible on the M3/ and the whole tooth row

Among the newly collected material of S major one finds

a good proportion of juveniles (stages 0–1: 33.3%) and old

adults (stages 5–6: 21.6%) compared to prime adults (stages

2–4: 45.1%)

The scatter plot of M/1 length by width, organized by locality, does not provide a clear pattern of size differences (Fig 2.9) Specimens from the pooled Loc 10 complex of localities encompass the full range of variation, while it appears that specimens from Locs 1, 3, 5, 9, and 11 are slightly larger than those from Locs 6, 8 and 15 When the data are sorted by stratigraphic level (i.e., below Tuff 2, below Tuff 3, between Tuffs 3–5, between Tuffs 5–7, between Tuff 7 and the Yellow Marker Tuff) one observes a slight

Fig 2.7 Left maxillary toothrow of Saccostomus major from the

Upper Laetolil Beds EP 1738/04 from Loc 2 (left) and EP 1326/03

(right M1/) from Loc 11 (right) Scale bar indicates 1 mm

Fig 2.8 Wear stages of the M1/ and M/1 Saccostomus major from the

Upper Laetolil Beds Top row, M1/ (a) stage 1, EP 1375/00; (b) stage

2, EP 160/03; (c) stage 3, EP 3904/00; (d) stage 4, EP 998/05 Bottom

row, M/1 (e) stage 1, EP 162/03; (f) stage 2, EP 1424/03; (g) stage 3,

EP 2434/03; (h) stage 4, EP 1065/03 Scale bar indicates 1 mm

Fig 2.9 Scatterplot of the M/1 dimensions (mm) of Saccostomus

major by locality The specimens from Loc 7E (black triangles) come

from the Upper Ndolanya Beds

2 Rodents

decrease in size between the lower levels and upper levels

(Fig 2.10) However, the sample is too small to reach a

definitive conclusion about the biostratigraphic variation of

Saccostomus M/1 through the Upper Laetolil Beds

Specimens from the Upper Ndolanya Beds fall in the middle

of the distribution

We confirm the presence of S major in the Upper Laetolil

Beds and add it to the faunal list of Loc 15 However, it is

still absent from Locs 12, 13 and 21, as Denys (1987a)

pre-viously observed It is not yet found in the Lower Laetolil

Beds, although it is recorded at older eastern and southern

African sites Saccostomus major is described from the

Manonga Valley (Winkler 1997), while S geraadsi was

named by Mein et al (2004) from Ch’orora (Ethiopia) and

Harasib 3a (Namibia) Finally, Mein and Pickford (2006)

recognized S cf geraadsi based on molars from Lukeino in

Kenya, dated to around 6.1–5.8 Ma

Saccostomus major from Laetoli is similar in size to

that from the Manonga Valley (Table 2.6, Fig 2.11)

Saccostomus geraadsi from Lukeino and Harasib have

smaller molars compared to S major, and their molar

size fits within the variability of S cf mearnsi from

Olduvai Bed I (Fig 2.11)

Saccostomus cf major

(Figs 2.9–2.12)

Denys (1987a) described a single mandibular fragment

(LAET 75-862) from Loc 18 (Upper Ndolanya Beds) and

left it unattributed at the species level due to the small size of

the M/2-3 New remains of Saccostomus have been

recov-ered from the Upper Ndolanya Beds at Loc 7E and are

described here

Referred material: Loc 7E EP 1247/03 (Fig 2.12), isolated right M/1 EP 1248/03, associated mandibles EP 1249/03, left mandible fragment with M/1-2

The isolated lower molar belongs to a young individual (wear stage 2) with the two cusps of the prelobe still visible (Fig 2.12) It is comparable in size to specimens from the Upper Laetolil Beds (Fig 2.9) Because it shows dentine and enamel corrosion we cannot describe the specimen in detail, except to mention that it has a link between the prelobe and the first lobe and a tiny cingular cV5 on the labial side of the molar The mandibular fragment with M/1-2 also fits within

the size variation of other Laetoli S major specimens, and

can be attributed to wear stage 1 (Fig 2.9) The main

differ-ences distinguishing the Laetoli material from S cf mearnsi

of Olduvai are the large prelobe of M/1 and the presence of

an anterolabial crest (absent in the Olduvai Bed I specimens)

Consequently, the new Saccostomus specimens from Loc 7E can be attributed to S cf major pending additional finds

from the Upper Ndolanya Beds Because no new material

was recovered from Loc 18 we retain here Saccostomus sp

for the unique specimen from the Mary Leakey collection

Saccostomus cf major

A single mandibular fragment (EP 2075/03) with a broken M/1 (with trace of two roots) and a well-preserved M/2 is known from Emboremony 1 (Lower Laetolil Beds) This molar is of wear stage 4 and displays two relatively trans-verse lobes with fused cusps and an anterolabial cingulum Its size (1.72 × 1.81 mm) falls within the range of the M/2s of

S major from the Upper Laetolil Beds.

Family Muridae Illiger, 1811Subfamily Gerbillinae Gray, 1825The Upper Laetolil Beds have already yielded two different species of Gerbillinae (Denys 1987a) One (Gerbillinae sp.) was not attributed to any genus due to the low number of speci-mens and the limited availability of characters The other was

attributed to Gerbilliscus cf inclusa and was characterized by

wide molars, very transversely aligned cusps, and mesially open prelobe on M/1 The new collections allow a more detailed description of the Gerbillinae sp of Denys (1987a) Recent molecular revisions have changed the genus nomenclature, so

we follow Wilson and Reeder (2005) in retaining Gerbilliscus for the Laetoli specimens in place of the old name Tatera Genus Gerbilliscus Thomas, 1897

Gerbilliscus satimani sp nov.

(Figs 2.13–2.16)Holotype: EP 147/01, nearly complete cranium with associ-ated mandibles Nasal region missing (Fig 2.13)

Type locality: Loc 6, Laetoli, Tanzania

Age and horizon: Mid-Pliocene, Upper Laetolil Beds

Fig 2.10 Scatter plot of Saccostomus major M/1 grouped by

strati-graphic level: ULB, Upper Laetolil Beds; 3-5 = between Tuffs 3 and 5;

6-7 = between Tuffs 6 and 7; 7-8 = between Tuffs 7 and 8;

7-YMT = between Tuff 7 and Yellow Marker Tuff; Lower 2 = below

marker tuff 2; Lower 3 = below Tuff 3, UNB, Upper Ndolanya Beds