“Evolution of Plio-Pleistocene Proboscidea from the Lower Omo Shungura Formation”

ADDIS ABABA UNIVERSITY COLLEGE OF NATURAL SCIENCES School of Graduate Studies School of Earth Sciences

Tomas Getachew

A thesis submitted to the school of Graduate Studies of Addis Ababa University in Partial fulfillment of the degree of Master of Science in Earth Sciences (Paleontology and Paleoenvironment).

Advisors Balmual Atnafu (PhD) Jean-Renaud Boisserie (PhD)

December, 2015

Addis Ababa Table of Contents

Contents Page

Approval Form ...... i

Acknowledgement ...... ii

List of tables ...... iii

List of figures ...... iv

Abstract ...... v

1. CHAPTER ONE: INTRODUCTION ...... 1

1.1. Background ...... 1

1.2. Location of the study area ...... 6

1.3. History of research in the Shungura Formation ...... 7

1.4. Statement of the problem ...... 10

1.5. Obj ectives of the study ...... 12

1.5.1. General obj ective ...... 12

1.5.2. Specific objectives ...... 12

1.6. Significance of the study ...... 12

1.7. Limitations of the study ...... 13

1.8. Organization of the study ...... 14

2. CHAPTER TWO:LITERATURE REVIEW ...... 15

2.1. Proboscidean evolution ...... 15

2.2. Geology of the area ...... 23

2.3. Fossil faunal assemblage at the Shungura Formation ...... 26

2.4. Previous works at the Shungura Formation.

30 3. CHAPTER THREE: MATERIALS AND METHODS

3.1. Materials ...... 30

3.1.1. The comparative materials ...... 32

3.2. Methods ...... 32

3.2.1. Field work ...... 32

3.2.1. Laboratory work ...... 33

3.3. Some of elephant tooth characters used for the study ...... 40

3.4. Terms and measurement procedure ...... 43

3.5. Methods of data analysis ...... 45

4. CHAPTER FOUR: RESULTS ...... 47 4.1. Morphological description of some new elephantid remains from the Shungura Formation ...... 47

4.1.1. Systematic paleontology ...... 47

4.1.2. Description and comparison ...... 49

4.2. The evolution of hypsodonty index within the five taxonomic groups ...... 54 4.3. The evolution of hypsodonty through the members of the Shungura Formation.56

4.4. The evolution of enamel thickness within the five taxonomic groups of Elephas recki 60

4.5. The evolution of lamellar frequency within the five taxonomic groups of Elephas recki 65

4.6. Comparison of enamel thickness versus hypsodonty index, and laminar frequency ...... 68

4.7. Tooth wear-based dietary analysis for the five taxonomic groups of Elephas recki ...... 70

5. CHAPTER FIVE: DISCUSSION...... 74

5.1. Discussion on the comparative description of specimens of Elephas recki from the Shungura Formation...... 74

5.2. Evolution of hypsodonty index through the Shungura Formation ...... 75

5.3. Evolution of enamel thickness through the Shungura Formation ...... 77

5.4. Evolution of lamellar frequency of the five taxonomic groups of Elephas recki lineage from the Shungura Formation ...... 78

5.5. Paleoenvironments and dietary adaptations of Elephas recki ...... 82

6. CHAPTER SIX: CONCLUSION AND RECOMMENDATIONS...... 86

6.1. Conclusion ...... 86

6.2. Recommendations ...... 88

REFERENCES ...... 90

APPENDIX ...... 100

Appendix 1: Biometric characteristics of the five taxonomic groups of Elephas recki ...... 101

Appendix 2: Measured mesowear angle of the five taxonomic groups of Elephas recki ...... 107

ADDIS ABABA UNIVERSITY COLLEGE OF NATURAL SCIENCES School of Graduate Studies School of Earth Sciences

“Evolution of Plio-Pleistocene Proboscidea from the Lower Omo Shungura Formation”

Tomas Getachew

A thesis submitted to the school of Graduate Studies of Addis Ababa University in Partial fulfillment of the degree of Master of Science in Earth Sciences (Paleontology and Paleoenvironment).

Approved by examining committee Dr. Balmual Atnafu (Advisor) ___ Dr. Jean-Renaud Boisserie (Co-Advisor) Dr. Mulugeta Fisseha (Examiner) _____ Dr. Solomon Yirga (Examiner) ______Dr. Mulugeta Alene (Chairman) ______

Acknowledgment

My deepest gratitude goes to my advisors Dr. Jean-Renaud Boisserie and Dr Balmua Atnafu for their constructive advice and suggestion to accomplish the thesis work. I would like to specially thank Dr. Jean-

Renaud Boisserie for accepting to be my advisor and for providing me some references. I thank the

ARCCH for allowing me the access of collection and laboratory facilities. I also thank Omo Group

Research Expedition for allowing me to access and study a recently finds. I thank AAU, School of Earth

Sciences for funding for my study.

I am also grateful to Dr. Zeresenay Alemseged for providing me some references. Furthermore, my gratitude extends to my family members who have always been on my side through the ups and downs, my friends working at the ARCCH for their relentless encouragement and support of my research work.

List of Tables

Page

Table 3. 2 Number of samples selected 32 57 Table 3. 2 Abbreviations of measurements and terms used in this study 57 Table 4.1 Metric data for Elephas recki molars from the eastern Africa sites

Table 4.4 Probability (p) and statistical summary for Hypsodonty Index values of the five taxonomic group of Elephas recki lineage from the Shungura Formation 58

Table 4.5 Mann-Whitney pair tests: for hypsodonty index values of the five taxonomic group of Elephas recki from the Shungura Formation 59

Table 4. 6 Probability (p) and statistical summary of enamel thickness values of subspecies of Elephas recki from the Shungura Formation 61

Table 4.7 Probability (p) and statistical summary of the Enamel Thickness values of subspecies of Elephas recki from members of the Shungura Formation 62

Table 4.8 Mann- Whitney pair tests: for enamel thickness values of the five taxonomic group of Elephas recki from the Shungura Formation 62

Table 4.9 Mann- Whitney tests: For enamel thickness values 65

Table 4.10 Probability (p) and statistical summary for lamellar frequency values of subspecies of Elephas recki from the Shungura Formation 65 Table 4. 11Probability (p) and statistical summary for the lamellar frequency values of subspecies of Elephas recki from members of the Shungura Formation 66

Table 4.12 Mann- Whitney tests: For lamellar frequency values of subspecies from the Shungura Formation 67

Table 4.13 Mann- Whitney tests: For lamellar frequency values of subspecies from Members of the Shungura Formation 68 Table 4.14 Probability (p) and statistical summary for the mesowear angle values of subspecies of Elephas recki from the Shungura Formation 71

Table 4.15 Probability (p) and statistical summary for the mesowear angle values of subspecies of Elephas recki from members of the Shungura Formation 72

List of Figures

Page

Figure 1 Spatial location of the Shungura Formation 7

Figure 2.1 Phyletic diagrams among different taxonomic families of the order Proboscidea 20

Figure 2.2 A Cladogram showing different taxonomic genera of order Proboscidea 21

Figure 2.3 Phylogeny included Stegotetrabelodon as the potential ancestor for the family 22

Figure 2.4 Phylogeny includes Primelephas as the ancestor to the Elephantidae. 25

Figure 2.5 The stratigraphic description of lower Omo Shungura Formation 25

Figure 2.6 Schematic map of the Turkana Basin 25

Figure 3.1 Activity in the field 34 Figure 3.2 Activities in the laboratory 35 Figure 3. 3. Illustrations of the measurable parameters and structural characteristics of Elephas teeth. 38

Figure 3.4 Mesowear angle measuring procedure. 39

Figure 3.5 Illustration of measures of elephantids molars. 42

Figure 3.6 Illustration measures of the height and the width of elephant tooth plate 43

Figure 4.1 Elephas recki brumpti occlusal view. 53

Figure 4.2 Recently discovered Elephas recki shungurensis occlusal view 54

Figure 4.3 Box plots of the hypsodonty index values of Elephas recki 56 Figure 4.4 Box plots of the hypsodonty index values of Elephas recki from different members of the Shungura Formation. 58 Figure 4.5 Box plots of the enamel thickness values of Elephas recki 61 Figure 4.6 Box plots of the enamel thickness values of Elephas recki subspecies from Members of the Shungura Formation. 63 Figure 4.7 Box plots of the lamellar frequency values of Elephas recki. 67

Figure 4.8 Box plots of the lamellar frequency values of Elephas recki subspecies from the Members of the Shungura Formation. 67

Figure 4.9 Linear regressions of mean hypsodonty index values and enamel thickness. 70

Firgure 4. 10 Linear regressions of mean lamellar frequency values and enamel thickness 70 Figure 4. 11

C3/C4 dietary spectrums of proboscidean 71

Figure 4.12 and 4.13Box plots of mesowear angle 72 Figure 5.1 (A) Incremental evolution of hypsodonty index in the African Plio-Pleistocene Elephas recki/iolensis lineage.and (B) Data from this study: evolution of hypsodonty index within the subspecies of Elephas recki. 76

Figure 5.2 Evolutionary change in enamel thickness: (A) of three elephant lineages and (B) Data from this study: evolution of enamel thickness 78

Figure 5.3 Evolutionary change in lamellar frequency of three elephant lineages: (A) of three elephant lineages. (B) Data from this study: evolution of lamellar frequency result from the study. 79

Figure 5.4 Mesowear angle results: 83 Figure 5.5 Linear regressions (A) between hypsodonty index values and mesowear angle and (B) between enamel thickness and mesowear angle values. 84

ABSTRACT

The Shungura Formation is a Plio-Pleistocene paleontological site found in southern

Ethiopia, in the Lower Omo Basin, and well known for its abundant mammalian fossil record as well as continuity of the stratigraphic sequence. It is one of the best sites which is radiometrically well dated. It yielded abundant mammalian fossils among these Proboscidea were common elements; there were seven proboscidean species (Anancus kenyensis, Stegodon kaisensis,

Elephas ekorensis, Deinotherium bozasi, Elephas recki, Loxodonta exoptata, and Loxodonta adaurora) that went extinct during Pleistocene.

The comparative description on old Omo collection maxillary associated right and left molars, mandibular associated left molar and the recently discovered fragmentary mandibular associated molars recovered from the Shungura was compared with complete and nearly complete molar specimens their taxa. Dental metric measurements were conducted from the original materials of Shungura and metric data were compared as illustrated in table 4.13.

Morphological observations were made both from the original and published materials from contemporaneous sites in eastern Africa such as Koobi Fora, Shungura, Allia Bay and Middle

Awash. The Morphological description and metric comparison of the dental materials from the

Shungura confirm that the relationships among the three taxa in eastern African sites changed at the same rate through their evolution.

Results from the biometric analysis indicate that, different subspecies of Elephas recki show statistically significant evolutionary changes in terms of the biometric traits. Generally, the results show that there is no clear progressive increase in crown height. Instead, some sudden changes in morphological features and no progressive trends in the lineage of Elephas recki throughout the Plio-Pleistocene of Shungura were observed.

The results from the mesowear angle analysis of this study show that, there is no significant difference in the mean mesowear angle values (ranging from 120 o to 130o) of the entire lineage of Elephas recki through Plio-Pleistocene in the Shungura. These mean mesowear angle values in general indicated that, Elephas recki adapted consistently to C4 dominated diet during their evolution.

Key Words: Shungura; Elephas; biometrics; dental morphology; mesowear; paleodiet; paleoenvironments.

Introduction

CHAPTER ONE INTRODUCTION

1.1 Background

The order Proboscidea is one of the oldest surviving and the most diverse mammalian group to have inhabited Africa (Coppens et al., 1978; Made, 2010; Kingdon, 2013) and they are represented in modern Africa. As suggested by genetic evidence, the extant African elephants should be divided into two distinct species: the savanna elephants (Loxodonta africana) and forest the elephants (Loxodonta cyclotis), currently distributed throughout the African continent south of the Sahara (Coppens et al., 1978; Made, 2010). Both Loxodonta and the Asian Elephas belong to the family Elephantidae (Maglio, 1973; Coppens et al., 1978; Kingdon, 1997; Made

2010). Starting from the Eocene all the way to Pleistocene, the proboscideans were a dominant group in Africa. Later on they reached all the continents except the isolated Australia, Antarctica and southern America (Kurten, 1968; Coppens et al., 1978; Made, 2010).

The family Elephantidae belongs to the order Proboscidea and comprises the elephants and their extinct relatives (Coppens et al, 1978; Kingdon, 1997; Made 2010). This family is subdivided into two subfamilies as Stegotetrabelodontinae and Elephantinae (Maglio, 1973;

Coppens et al., 1978). The subfamily Elephantinae consists of four genera: Elephas,

Primelephas, Loxodonta, andMammuthus (Maglio, 1973; Coppens et al., 1978; Shoshani and

Tassy, 1996), all of which arose in AfroArabia during the late Miocene and by the late Pliocene.

Except Loxodonta, which is endemic to Africa, they had been dispersed throughout the old world and into northern America (Maglio, 1973, Coppens et al., 1978).

These subfamilies have been circumscribed by a set of traits; their functional grinding cheek teeth; their low to high crown molar teeth bearing transverse seven to thirty ridges (plates) per tooth that are enveloped with cement (Maglio, 1973; Coppens et al., 1978; Made, 2010;

Introduction

Kingdon, 2013); and no more than one and half molars in use per jaw in adults. The lower tusks are present only in the early forms of the elephantids. In the more progressive forms of the species they have reduced and lost the mandibular tusks and their jaw symphysis were shortened early in their evolutionary history (Maglio, 1973; Coppens et al., 1978; Made, 2010).

Common features for the living elephants include large size (Loxodonta is the largest living terrestrial animal, reaching a height of 4 m at the shoulder and a weight of 6 tonnes); longevity (elephants can live to about 80 years); and presence of trunk or proboscis (not all extinct proboscideans had a trunk).

The proboscis is a combination of the upper lip and nose, the two nostrils continue throughout the length of the trunk; the trunk is a multi-purpose prehensile organ and is probably the most important appendage for elephant survival (Made, 2010; Kingdon 2013). The skin

(dermis and epidermis) can reach 32 mm in thickness, yet it is sensitive, movable and the body is covered with little hair and bristles (most hair is on head and tail and young elephants are more hairy than adults (Kingdon, 2013). The limbs are columnar with long proximal and short distal elements having graviportal adaptations. The sole of the forefoot is larger (used for support) and round, whereas the hind foot (used for support and propulsion) is oval (Coppens et al., 1978;

Kingdon, 2013).

The neck of the proboscideans is short and support their pneumatized (filled with air sinuses) cranium, thereby reducing the weight of the cranium (Coppens et al., 1978; Badoux,

1961 as cited in Kingdon, 2013), while providing ample attachment for the nuchal and masticatory muscles. The external nares (where the trunk begins) are elevated. A secondary acoustic meatus is present, as are the alisphenoid canal and the mandibular coronoid canal. The

Introduction

hyoid apparatus consists of five bones. Premolars and molars are composed of plates (lamellae) held together with cementum, the inside of each plate contains dentine, surrounded by enamel, lozenge shaped in Loxodonta (hence the name) and in compressed loops in Elephas ('Elephas' means huge arch). The dental formula is reduced to I 1/0 C 0/0 P 3/3/ M 3/3 in both living representatives, but was more reduced in some extinct forms (Maglio, 1973; Coppens et al.,

1978; Kingdon, 2013).

The living elephants inhabit a variety of terrain from the desert to mountain top and generally prefer high forest, forest-savanna mosaic, and open woodland (Coppens et al., 1978). In addition to these they also have exhibited nocturnal, diurnal and crepuscular acturties to avoid their predators (Seiffert, 2010; Sanders et al., 2010; Kingdon, 2013). As stated by Kingdon

(2013), these groups of animals have an excellent sense of hearing, an actual sense of smell, very good sense of touch but poor sense of vision. Elephants migrate long distance in search of food

(an adult requires 100- 250 kg of food per day). They are herbivorous (Loxodonta is more browser than grazer while Elephas is more grazer than browser) animals (Coppens et al., 1978;

Osborn, 2005; Wittemyer et al., 2007 as cited in Biru and Bekele, 2012; Kingdon, 2013).

The fossil history of the proboscideans is excellent in the sense that one can almost certainly count on finding a record if they lived in a given area where fossiliferous deposits were laid down (Kurten, 1968). Usually it is the massively built cheek teeth that will be well preserved better than the other parts (Kurten, 1968; Maglio, 1973). These teeth are very useful for classification purposes and the rapid evolution of the elephants in the geologic time particularly in the early Pliocene and late Pleistocene makes them important guide (i.e.,for biostratigraphy correlation) fossils in eastern Africa (Maglio, 1973; Coppens, 1978; Cooke, 1993).

Introduction

African upper Pliocene and lower Pleistocene deposits often exhibit limited spatial extension and significant chronological gaps, but this is not the case for a large part of the Omo

Group deposits in the Lower Omo Valley. Within the Shungura Formation, particularly extensive and continuous deposits dating between 3.6 Ma and 1.0 (Coppens, 1978; Feibel et al., 1989) are found. The Lower Omo Valley fossil records are therefore powerful tools for the investigation of the Plio-Pleistocene faunas, that is, how they evolved in the northern Turkana Basin, and allow interpreting this evolution in terms of possible environmental differences (Coppens, 1976; Bobe and Eck, 2001; Alemseged, 2003; Boisserie et al., 2008; Bobe, 2011).

The Shungura Formation is a Plio-Pleistocene paleontological site in southwestern

Ethiopia, which is one of the best studied hominid sites and one of the earliest stone tool bearing sites in Africa (Howell and Coppens, 1974; Brown et al., 1978; Feibel et al., 1989; Cooke, 1993;

Bobe, 2011). The abundant fossil records (over 55,000 different specimens of mammalian and other non-mammalian fossils) collected from Shungura and adjacent formations in different time

(in the 1933, 1967 to 1976, and 2006 to the present) by different research missions.

More than anything, from the geologic point of view the continuity of the sequence and the availability of radiometric dates for the different stratigraphic units, make the Shungura

Formation the ideal place to study changes in faunal morphology and abundance

(Coppens 1978; Bobe, 2011), as well as environmental and dietary adaptations through time (Brown et al., 1978; Bobe and Eck, 2001, Alemseged, 2003; Bobe, 2011).

Different hypothesis had been proposed regarding the change in proboscidean molar morphology. It was mainly the result of change in dietary habits and environmental change

(Maglio, 1973; Bobe, 2006; Saarinen et al., 2015). This indicates the functional significance of

Introduction

the different molar types in proboscideans. These groups of animals offer some of the best material for analysis, because they have greatly changed their molar morphology from brachyodont to hypsodont (Coppens et al., 1978; Coppens, 1978). Thus the main function of proboscidean molars are chewing, crushing and grinding (Coppens et al., 1978).

Fossil mammals are basically one of the best sources available for reconstructing past vegetation patterns and the past climate conditions as well (Fortelius, 2003; 2006; Bobe, 2011).

Thus fossil herbivore teeth are commonly used to reconstruct the diet and environment of extinct species (Fortelius and Solounias, 2000; Bobe, 2011.Using different approaches which include faunal abundance analysis, analysis of species’ first and last appearance datum (FADs and

LADs), paleobotanical studies, ecomorphological studies, and isotopic records from paleosols, tooth surface wear analysis (mesowear/ microwear) and stable carbon and oxygen isotope analysis it can be possible to investigate the paleoenvironment and paleoecology of Plio-

Pleistocene hominid sites of Africa (Coppens, 1978; Bonnefille and Dechamps, 1983; Vrba,

1984, 1995; 1999; Fortelius and Solounias, 2000; Alemseged, 2003; Alemseged et al.,2007;

Bobe, 2011; Negash et al., 2015).

To infer the ecologic characteristic of the extinct species functional morphology is an important tool (Bobe and Eck 2001). It appears that the increasing abrasiveness of the food

(achieved by more phytolith content and more exogenous grit and dust) indeed provided a selective force on the evolution of tooth crown height within the lineage of Elephas and sooner or later the increasing hypsodonty elicit the rest of the morphological changes of the molars.

Therefore fossil remains in terms of functional anatomy and its relationship to environmental conditions play a great role for these morphological changes (Kappelman, 1988; Spencer, 1997;

Bishop, 1999 as cited in Alemseged et al., 2007).

Introduction

1.2 Location of the Study Area

In southern Ethiopia [the Southern Nations Nationalities and Peoples Region State

(SNNPR)] and northern Kenya the Turkana Basin, developed in the early Pliocene all the way to

Pleistocene within the northern segment of the Kenyan Rift (Brown and McDougall, 2011;

Feible, 2011). The Shungura Formation is located in the Lower Omo Valley, which is a part of southwestern region of Ethiopia, west of the Omo River and north of Lake Turkana(Brown and

Heinzelin, 1983; Fig. 1) about 1000 km away from Capital city, Addis Ababa. It is located and extends north and south 36th degree parallel (East) between 5 and 6 degree North latitude

(Davidson et al. 1973; Wesselman, 1984) [Figure1]. The composite stratigraphic section of the formation measures nearly up to 800 m of Plio-Pleistocene sediment deposits, generally dipping less than 108W, was defined as the Omo Group by de Heinzelin (1983).

The Omo River, which is one of the largest perennial rivers in Ethiopia and flanked by forest, is the only major river in the basin. It rise in the Showa plateaus and flows down the valley in a meandering course generally southward and drains regions of western Oromia and Southern

Nations Nationalities and Peoples Region with a total length of 760 Km and eventually enters the northern end of Lake Turkana.

Introduction

Figure 1 Spatial location of the Shungura Formation, Lower OmoValley, and southwestern Ethiopia. AA: Addis Ababa; >^^^^^^IShungura

Formation. Modified from Boisserie et al., (2008).

1.3 History of research in the Shungura Formation

The history of paleontological study and the discovery of scientifically significant fossils and

artefacts in the Lower Omo Valley at the Shungura Formation go back to the beginning of 20th century (Howell and Coppens, 1974). The Omo Group deposits of the Lower

Introduction

Omo Valley, mainly the Shungura Formation, characteristic notably in the history of research on human evolution. It was one of the first palaeoanthropological research areas known in eastern

Africa, and was exploited by a multiplicity of teams with a correlated variety of methods, goals, and theoretical frameworks (Howell, 1968; Alemseged et al., 2007; Boisserie et al., 2008).

The French palaeontologist C. Arambourg was initially drawn to the Lower Omo Valley for the reason that fossils were collected (which was the first remains of fossil elephants from eastern Africa that were recovered by E. Brumpt from there in 1902) during the trans-African expedition of R.du Bourg de Bozas. By the time 1932 to 1933, C. Arambourg was the first to conduct systematic paleontological field expedition in that area (Mission Scientifique de l'Omo) through Kenya and worked and collected some of vertebrate fossils mostly on the southern part of the Lower Omo Valley fossiliferous deposits (Howell and Coppens, 1974; Coppens, et al.,

1976; Boisserie et al., 2008; Beden 1983). Thirty-three years later, in 1966 the International Omo

Research Expedition has been formed to work on the geology of sediment exposures, and the paleontology of those exposures in the Omo basin. Hence, during nine successive field seasons,

1967-1976, a diversity of scientific activities have been engaged by the group of the mission under the direction of F. C . Howell, Y. Coppens, L. Leakey and C. Arambourg (Howell and

Coppens, 1974; Coppens et al., 1976).

The International Omo Research Expedition (IORE) mission (from 1967 to 1976) that was composed of a multidisciplinary field of study have worked in the Lower Omo Valley and they have given a number of articles and publications done in general on the geology and the paleontology of the region (Howell, 1968; Howell and Coppens, 1974; Coppens, 1978). Thanks to them they forwarded vast information regarding mammalian fossils. Hominid fossils as well as archaeological records are found in the strata, more over they have disseminated data particularly

Introduction

interesting to see and understand how the environment changed during the period when our ancestors were evolving in eastern Africa (Howell and Coppens, 1974; Coppens, 1978;

Alemseged, 1996).

No fieldwork was done for 30 years between 1976 and 2006, when the Omo Group

Research Expedition was created (in 2006) with groups of interdisciplinary field of international research organized and lead by J. R. Boisserie. This team, which has been active since its creation, conducts surveys and localized excavations, along with detailed stratigraphic studies, and is engaged in revising the faunal record collected in the late 1960s and early 1970s (Boisserie et al., 2008).

The Omo Group Research Expedition reinitiated in 2006 and started field work on

Shungura Formation with renewed methods, and collected around 5200 fossil vertebrate specimens (Boisserie pers. comm.) with a particularly precise record of contextual data. These specimens include significant hominid remains dated to 2.5 Ma and slightly older (Boisserie et al., 2008). The crew recorded changes in faunal distributions and in addition, the archaeological record of that site is also reconsidered (Boisserie et al., 2008). The Omo Group Expedition is also contributing a number of articles and publications with results that are indicative of future advances in the study of biodiversity evolution and its relationship with global and regional environmental changes (Boisserie et al., 2008; Dalagne et al., 2011; Bibi et al., 2013). 1.4 Statement of the Problem

Elephas recki is one of the most common faunal elements of the Plio-Pleistocene of eastern Africa (Maglio, 1973; Coppens, 1978; Beden, 1983). It is distinguished by five evolutionary stages of E. recki, to which the following subspecific names were given: E.recki brumpti, E. recki shungurensis, E. recki atavus, E. recki ileretensis, and E. recki recki (Beden,

Introduction

1983). These five subspecies have been accepted widely as valid taxonomic units and are frequently employed in discussions of biostratigraphy for Plio-Pleistocene hominidbearing beds in eastern Africa (Saegusa and Gilbert, 2008; Sanders and Haile-Selassie, 2011).It is known that the African Elephas has been very important for faunal correlation in eastern Africa, and to some extent in Southern Africa (Beden, 1983; Kalb and Mebrate, 1993).

According to Sanders and Haile-Selassie (2011), reconsideration of subspecies of E.recki indicates that they are arbitrary lineage division tied to geochronological boundaries rather than phylogenetic entities. Previous studies on recovered subspecies of E.recki atavus and E. recki ileretensis from Koobi Fora and Ileret sits, both being in Kenya, shows the existence of teeth that are more advanced than those from Shungura Member G, but they are less progressive than those from Shungura Member K (Beden, 1983).

The tooth morphology difference are observed in the above sedimentary strata, which have similar age in the Lower Omo Valley and east Turkana, only separated by less than 50km at their closest point. For this reason, if climatic and tectonic change occurs in one of the locality it should be reflected in the other too (Beden, 1983). Therefore; the present research study is intended to clarify the transition of E. recki subspecies of Shungura and Koobi Fora, which are within the same basin. And also further analysis in the transition between E .recki atavus and E. recki ileretensis within the Shungura Formation in upper Member G and Member H.

Our understanding of the origin, diversification, and evolution of mammals is tightly linked to our knowledge of the paleo-environments in which these events took place (Vrba, 1995;

Alemseged et al, 1996; Bobe and Eck, 2001; Reed, 2007). Fossil mammals are central to

Introduction

developing our ideas about environmental change (Fortelius et al., 2003; Bobe, 2011) and fossil herbivore teeth are commonly used to reconstruct the diet and environment of extinct species

(Fortelius and Solounias 2000). Even if the paleoenvironment of the Shungura Formation has been addressed through different approaches such as paleobotanical studies, ecomorphological studies, and isotopic records from paleosols and faunal abundance (Coppens, 1978; Bonnefille,

1983; Bobe and Eck, 2001; Alemseged, 2003; Bobe, 2011), there are still questions that wait to be answered.

Therefore, this study attempts to address some of these questions using molar enamel surface mesowear analysis of elephantid fossil molar teeth. This approach has never been applied systematically to these groups of animals and the output result will help us to investigate their evolution, their intra specific variation and the shifting dietary adaptations of Elephas across each stages of evolution through the different members of the formation, and hence, will help us in understanding the change in the paleolandscape through time.

Introduction

1.5 Objectives of the study

1.5.1 General Objective

The primary objective of this study is to address the general evolutionary trends of

Elephas recki from Shungura Formation and to understand and infer the paleo-dietary adaptation of these taxa.

1.5.2 Specific Objectives

> Describe their systematic evolution;

> Refine biostratigraphic correlation of the Shungura and other east African Plio- Pleistocene

paleontologically important localities;

> Infer the paleodietary and paleohabitat preferences of the Plio-Pleistocene proboscideans

(lineage of Elephas recki).

1.6 Significance of the Proposed Study

There are important reasons for studying proboscidean fossils from the Shungura Formation.

• This study will contribute to an understanding of proboscidean evolutionary history, and

also help refine the succession of subspecies Elephas recki for correlation of Shungura

Formation and other Plio-Pleistocene sites that have paleontological and

paleoanthropological importance.

• This research work will give an understanding of the mechanisms of biological

evolutions of the tooth morphology of the species Elephas recki.

• This study will give a clue in understanding the dietary preference of the fossil elephantids,

Introduction

which have been a part of the environment of our ancestors; and assessing the change in

their dietary adaptation through time that has implications for our understanding of the

change in environmental conditions in the Shungura Formation. This in turn will

contribute to a better understanding of environments and their impact on early hominid

evolution, speciation, migration or extinction.

1.7 Limitations of the study

There are more than 1400 cranial and postcranial proboscidean remains that came from over 300 different localities spread over 75 distinct stratigraphic levels collected from the Lower

Omo Valley Formations (Shungura, Mursi and Usno) by the International Omo Research

Expedition (IORE; 1967-1976). However, the expedition did not collect fossil proboscidean, hippopotamids, and other large mammals at the same rate as primates, bovids, and carnivores

(Alemseged 2003). In addition to this collection bias all the proboscidean fossil specimens are not studied well; similar to what happenned in other Plio-Pleistocene sites (such as Hadar and some other sites of fossil proboscideans).

Correspondingly, due to the lack of specimens of E. r. ileretensis from Members K and H of the Shungura Formation, the study faced the difficulty to address the arguments raised and brought to statement of the problems for this study, that is: previous studies on recovered subspecies of E. recki atavus and E. recki ileretensis from Koobi Fora and Ileret regions, both being in Kenya, shows the existence of teeth that are more advanced than those from Shungura

Member G, but that are less progressive than those from Shungura Member K. In addition there are no enough reference materials to complete comparative works done in this study. Moreover, mesowear, one of the proposed methods, is not straight forward as in

Introduction

other taxa. Even though analysis of proboscidean teeth is believed to be an applicable method of paleoecological reconstruction there are some different ways of measurements and assumptions that deserve great care and effort because of size and morphology of proboscideas (Saarinen et al., 2015).

1.8 Organization of the study

This work is composed of six chapters. The first chapter provides background information about the study area and the study objectives, as well as the significance and the limitations of the present study. Literature review on the proboscidean evolution, the geology of the area and fossil faunal assemblage, as well as the previous work on the Shungura Formation about the paleoenvironmental context of the formation is presented the second chapter. The third chapter deals, respectively, with the materials used and the methods adopted to collect and analyze data.

Presentation and description of the results obtained by the analysis is given in the fourth chapter.

The fifth chapter discusses in detail the results obtained, the interpretations made and their implications with regard to existing evidence, hypotheses and theories. Summary of the conclusions drawn from the study and recommendations for future work based on the results and interpretations are presented in the final chapter.

Literature Review

CHAPTER TWO LITERETURE REVIEW

2.1 Proboscidean Evolution

The early history of the proboscideans is endemic to Africa, where they have their oldest

record from the Paleocene (60 to 55Ma), and the earliest known species being called Eritherium

azzouzorum. Its lower premolars have one large main cusp and the uppers have a pair of two

large cusps. The molars are bunodont and have two lobes each with a pair of main cusps, and the

third lower molar has an incipient third lobe (Gheerbrant et al., 1996; Gheerbrant, 2009).

The next oldest species Phosphatherium escuillei, at the beginning of the Eocene

(55Ma), was discovered in Sidi Chennane quarries of the Ouled Abdoun phosphate basin,

Morocco (Shoshani, 1998; Gheerbrant, 2009). Its cheek teeth (molars and premolars) show a

tendency towards more lophodonty, which means that pairs of cusps that are next to each other

are fused into a smooth transverse crest or loph (Gheerbrant et al., 1996).

According to Gheerbrant et al., (2002), the evolution towards lophodont teeth continued,

reaching perfect lophodonty among several lines of the ancestor of elephants species such as

Barytherium (Aguirre, 1969), one of the ancestors of elephants. This may be attributed to the

family Barytheriidae that is known from two localities only: the Fayum of Egypt and Dol el Talha

or Jebel Coquin in Libya (Harris, 1978). The dental evolution of these groups also includes

increase in the number of lophs or plates on premolars and molars; shift from regular tooth

replacement (deciduous teeth to permanent teeth) to horizontal displacement of premolars and

molars; and increase of tusk size (Aguirre, 1969; Kingdon, 2013).

Palaeomastodon and Phiomi are later forms (Made, 2010). They are well known from

well preserved material from northern Africa,at the Fayum in Egypt (Osborn, 1936) and also

Literature Review

some material known from eastern Africa, of Chilga (Oligocene site, 27Ma) in Ethiopia, which represent the youngest known record for this family (Kappleman et al., 2003). In these animals, trilophodonty (three lophs) was acquired; all later forms were at least trilophodont. The oldest occurrence of deinotheres was recovered from Chilga. This distinctive family of proboscideans was previously known only from the early Miocene through to the early Pleistocene epoch

(Harris, 1978).

This early Deinotheriid differs from other deinotheres, particularly in the nascent development of a third loph(id) in deciduous fourth premolars and in first molars. The occlusal morphology of its cheek teeth suggests independent derivation from a bunolophodont form such as Moeritherium rather than sharing an earlier ancestry with barytheres and numidotheres in the lophodont barytherioid group (Harris 1978). The later forms of deinotheres have fist molars with three lobes and second molars with just one lobe.

Deinotheres are the only proboscideans that lack their upper tusks, but instead they have lower tusks, which appear from the mandible in downward direction and then curve backward

(Made, 2010). Deinotheres also lost the two first premolars (P1 and P2), but still have all the permanent cheek teeth at the same moment in function. This is normal in mammals, but in the elephantids the premolars and even the anterior molars tend to disappear when the third molar is in function (Harris, 1978; Made, 2010). Deinothers have reduced nasal bones and large nasal openings, indicating that they had trunks (Harris, 1978; Made, 2010). They have long diastemata and with lack of upper tusks and one pair of upper and one pair of lower incisors and bifunctional bilophodont cheek teeth are features restricted to these groups

(Harris, 1978).

Literature Review

Another proboscidean species Gomphotherium, evolved in Africa during early Miocene

(around 18 Ma.), dispersed from Africa and reached Europe and also East Asia (Coppens et al.,

1978; Made, 2010). During the Plio- Pleistocene several lineage of elephantids evolved in Africa,

Asia and Europe, among which were the ancestors of elephants, such as Anancus, Stegodon,

Loxodonta, Mammuthus and Elephas (Aguirre, 1969; Made, 2010; Sanders and Haile-Selassie,

2011).

Shortly after its origin the order shows different major adaptive radiations (Coppens,

1978). Shoshani and Tassy (1996) introduced a recent approach, in which proboscidean taxa are described in three major radiations with corresponding plausible habitats. The first radiation involved taxa that emerged in the Paleocene-Oligocene epochs (58-24 Mya); the second involved taxa that emerged in the Miocene epoch; and the taxa of the third radiation emerged at the end of the Miocene and lived through the Holocene epoch (7 Mya to the present).

During the Late Pleistocene, the world saw a dramatic number of extinctions of very large terrestrial species. The losses of these megafauna; (such as elephants, camels, horses e.t.c) have been attributed to either of two different hypotheses. One hypothesis states that global climate changes occurring during the Pleistocene caused environmental pressures that forced the extinction of several megafaunal species. The second hypothesis proposes that the global spread of Homo sapiens and hunter-gatherer subsistence practices were responsible for these deaths.

These two theories reveal that neither climate changes nor human overkill were likely to be individually responsible for the Pleistocene extinctions. Instead, a synthetic model that includes both hypotheses appears to be the most plausible explanation for the Pleistocene losses (Gibbons, 2004; Benton, 2005).

Literature Review

Proboscidean evolution in the Pliocene (5.33 to 2.6Ma.) and all the way to the

Pleistocene (2.6Ma. to 11,000 years) is interesting because during this, time mainly in the

Pliocene (around 3.6 Ma), archaic elephant genera (Stegotetrabelodon, Primelephas,

Stegodibelodon) were completely replaced by basal members of crown elephant lineages

(Loxodonta, Elephas, Mammuthus), taxonomic diversity was high (multiple elephant species, anancine gomphotheres, stegodonts, and deinotheres), and elephants were undergoing substantial reorganization of the craniodental masticatory apparatus, presumably in response to the spread of more open habitats and greater competition for grazing resources, which is the primary reserves established by primary choice of food and as a result the beginning of adaptive radiation lies in the choice of food and of feeding habitat (Osborn, 1936; Ungar,2010; Senders and Haile-

Selassie,2011).

The living elephants are the Asian elephant (Elephas maximus) and African elephant

(Loxodonta africana); that incorporate the Savanna or African Bush Elephants, which belong to the family Elephantidae and for many specialists the informal use of the word “elephant” refers to this family. Alternatively the vernacular name could be applied to the order Proboscidea or

“trunkers”, referring to the trunk, which is the most typical character of these animals (Harris,

1978; Made, 2010; Kingdom, 2013).

In the teeth of elephantids, the cheek teeth (molars and premolars) lophs seen in mastodons (differs from elephants and mammoths in the form of molar teeth) are increased in height and number, to make a series of vertically arranged enamel plates. Each plate has a dentine core and the whole tooth is thickly enveloped in cement. In mastodons, three deciduous premolars and three permanent molars per dentition quadrant erupt in sequence through life. To

Literature Review

the opposite the elephants and mammoths, had only one to two teeth per quadrant in the mouth at a time because the cheek teeth of the Elephantidae, which were derived from the

Gomphotheriidae (Maglio, 1973), exhibit horizontal displacement, a feature also shared by non- elephantid taxa such as Gomphotheriidae ( Maglio, 1973; Shoshani and Tassy, 1996; Kingdon,

2010). See figure 2.1 Phyletic reletionships of taxonomic families of Proboscidea.

Fossil proboscideans, because of their size and abundance in superficial deposits, were the first fossils to attract human attention and their remains are often found in the various Plio-

Pleistocene deposits in eastern Africa (Simpson, 1945; Coppens et al., 1978; Cooke, 1993).

According to Maglio (1973), the genus Elephas, particularly the species E. recki, have completely replaced the genus Mammuthus in eastern Africa. Among the order Proboscidea, the most common species of the Plio-Pleistocene in eastern Africa is Elephas recki ( Maglio, 1971;

1973; Beden, 1980; Saegusa and Gilbert, 2008). According to Beden (1980; 1983; 1987a, b) this species has five distinct subspecies these are E. recki brumpti Beden, 1980; E. recki shungurensis Beden, 1980; E. recki atavus Arambourg, 1969; E. recki ileretensis Beden, 1980 and E. recki recki Dietrich, 1915. They all together represent a monophyletic lineage. See figures

2.2 Cladistic relationships of taxonomic genus of Proboscidea, and fig 2.3 and 2.4 showing the monophyletic lineage of E. recki.

Literature Review

E l e p h a n t

Fig. 2.2 A Cladogram showing the relationships among different taxonomic genera of order Proboscidea

(After Kalb and Mebrate, 1993; Shoshani, 1998)

Systematic Paleontology Order Proboscidea Illiger, 1811 Superfamily Elephantoidea Gray, 1821 Family Elephantidae Hay, 1922 Subfamily Elephantinae Hay, 1922 Genus Elephas Linnaeus, 1758 Species Elephas recki Dietrich, 1916

Literature Review

Beden 1979 Loxodonta ■HI afncana Loxodonta iPahdOModon) BUanbca MMH HPMI racta 'Pataotoxodon) rtc «au n f IHMI racw E/epnas iiere ens* [Pateotoiroaoa; MM M Loxodonta Miurwa BHMI want radc MMMH a ntrquus Loxodonta MMDCa Etophas racw HMMMI

■H ■Hi Ml BUM bfumpti burnt* Loxodcxnfa exop

Stf ■MHH

Fig. 2.3. Beden’s (1979) phylogeny included Stegotetrabelodon as the potential ancestor for the family. He also proposed several migrations of Elephas out of Africa into Eurasia. He also separated L. adaurora from the main Loxodonta lineage. He also uses Elephas and Paleoloxodon as subgenera for the African Elephas lineage.

WdWJ'LC^i maximu s vnsenmc•nVMVMSQIl IM LoxooonfoLoxcxtontaBOflURamcana LQMQQOO■MR WMMIStage■p■toISflStSMlMMOvetom&u ji IIIIVII MMMHMhysudrtcus■HM■MM Ehphas platycaphalusBMMft RMM M,K7imu0M|afncanavuscetebansssUsIMMiI ■MWIWftMcotomu mmuthos MammuthusMammuthusvnwNcMammumuspmpMiBaconStage Staoc M ta wmmElophasmm Maglio 1973) Mammuthus i RMRM u Dkoronsjsm WDRI M MMMMM

MMBMMMNM H Literature ReviewMM MM OTDUS gomphothtroidts

Sfegorefrabe/odon ■MOM

Fig. 2.4. In Maglio’s (1973) phylogeny, he includes Primelephas as the ancestor to the Elephantidae, and only one migration event of Elephas out Africa into Eurasia, where the lineage subsequently underwent an adaptive radiation.

The morphological and behavioral adaptations of early elephantids to their environment are a central theme in studies of their paleoecology. Accurate and detailed reconstructions of environments, especially of vegetation, are therefore critical for understanding early elephant’s adaptations (Coppens et al., 1978; Beden, 1987 a, b; Ungar, 2010). Progresses down the wearable tissue, exposing a set of hard enamel ridges that act like a millstone, as this goes on, the roots are resorbed and the tooth is finally lost. When this happens, the next tooth rapidly comes into wear behind (at some stages it has already started to wear).

Literature Review

Elephants must gather huge quantities of leaves, small branches and bark (Coppens et al., 1978;

Ungar, 2010), and grind them to a pulp in their efficient dental milling machine.

2.2 Geology of the area

The Turkana Basin of northern Kenya and southern Ethiopia began to develop into a large integrated depositional system in the early Pliocene. Subsidence initiated accumulation along the existing drainage networks of an erosional landscape and quickly broadened to the complex of sub-basins that would dominate the region for the next four million years. The history of the basin through the Plio-Pleistocene can be traced as a succession of flood plain systems, during which fluvial deposition dominated, and lacustrine phases during which much of the basin was inundated

(Brown and Heinzelin, 1983; Wesselman, 1984; Feibel, 2011).

The sedimentary strata that resulted from this Plio-Pleistocene episode are collectively referred to as the Omo Group, which include the Mursi, Usno, Shungura, Koobi Fora and

Nachukui Formations. The broad geographic extent of this system and the dynamic nature of its major landscape components (rivers, deltas, lakes, volcanoes) make this a complex system to characterize at any particular time. The Lower Omo Valley deposits are divided into three geological formations: the Shungura, Usno, and Mursi Formations, and by far the richest and the most continuous record of the Omo mammals are derived from the Shungura Formation (Howell and Coppens 1974; Brown and Heinzelin, 1983; Feibel et al., 1989, 2011; Bobe and Eck, 2001).

Heinzelin (1983) mapped the Shungura Formation in southern Ethiopia comprises 776 m thick of fluvial, lacustrine, and deltaic sediments where it dips c. 108W, and has been divided into

12 members on the basis of widespread volcanic ash layers, designated Tuffs (volcanic ash layers)

A through H, and J to L. Sediments below Tuff A are designated the Basal Member, followed

Literature Review

upward by Members A-L. Except for the Basal Member, a rhyolitic tuff s at the base of each member [Figure 2.2]. Each member above the Basal Member is named for the volcanic ash layer at its base, and includes that tuff and all overlying sediments up to the base of the next designated major ash layer; this Formation is also well known by its uniquely preserved Plio-Pleistocene fossil faunas (Brown and Heinzelin, 1983; Feibel et al., 1989; Bobe and Eck, 2001; McDougall &

Brown, 2008).

Literature Review

Figure 2.6. Schematic map of the Turkana Basin including Lake Turkana and the Lower Omo Valley. Gray shading indicates geological formations discussed in the text. Inset shows the basin in the context of eastern Africa adapted from Feibel (2011).

□ estimate □ magnetochronolog y I radiochronology Figure 2.5. The stratigraphic description of Plio-Pleistocene deposit of the lower Omo Shungura Formation (pers.commJ.R. Boisserie/OGRE)

Literature Review

2.3 Fossil Faunal Assemblage at Shungura Formation

A total of ca. 49,000 fossil specimens were collected from the Shungura and adjacent formations by International Omo Research Expedition (IORE) in the nine years of field work between 1967 and1976. These include 18 mammalian families, most of which are described to lower taxonomic groups. The majority of the mammalian families are herbivores, but carnivores also make up a considerable amount of the fossil record. Among the herbivores, it is known that bovids are the most abundant mammalian groups in the formation, comprising almost 42% of the faunal assemblage (Coppens, 1978; Bobe and Eck, 2001).

There were seven species of proboscideans occuring in the Omo beds, among them; the gomphothere Anancus was the only species that were recovered from strata older than 4 Ma.

(Coppens, 1978); but the rest of the species (such as Stegodon, Loxodonta, Deinotherium, and also the genus Elephas) were recovered from the strata younger than 3.6 Ma. (Coppens, 1978).

Two of these species, Deinotherium bozasi and Elephas recki, represent 98% of elephantid specimens, of the two species, Elephas is interesting because it is seen to evolve from the basal member to member L with very distinctive and recognizable evolutionary changes on the cheek teeth throughout the stratigraphic unites of the Shungura Formation (Coppens, 1978; Beden, 1980;

1983).

2.4 Previous Work at the Shungura Formation

The first fossils (including 41 elephant molar remains) were recovered from the Lower

Omo Valley by du Bourg de Bozas expedition (Beden, 1983, 1987a, b). The mission led by

Arambourg in 1933 Mission Scientifique de l’Omo, was the first to conduct systematic paleontological work in the Lower Omo Valley principally in the Shungura Formation (Coppens et al., 1976; Howell and Coppens, 1974; Howell and Coppens, 1983; Alemseged 2003; Boisserie

Literature Review

et al., 2008).

Arambourg documented the Plio-Pleistocene age and roughly described the locality stratigraphy and sedimentology. He had also sampled plentiful collection of vertebrate fossils that were recovered and had been taken to the relevant Museum for further study (at the National

Museum of Natural History, Paris, France) (Howell and Coppens, 1974). After he had studied the materials he recognized a number of new taxa of bovids, hippopotamids, and proboscideans, and described them in several publications in the 1930s and the 1940s (Boisserie et al., 2008; Beden

1983).

Later, as confirmed by Arambourg and Coppens (1967); Arambourg organized an international team of Paleontologists from France, USA and Kenya; F.C. Howell (USA) and L. S.

B. Leakey (Kenya) respectively. The second major expedition took place in 1967. Arambourg co- led the French group with Y. Coppens and they both together did a great work by describing a newly found hominid species as Australopithecus aethiopicus that was discovered from the Plio-

Pleistocene site of Shungura Formation and dated to around 2.5 Ma (Arambourg and Coppens,

1967 sited in Boisserie et al., 2008).

Various researchers (Dr. E. Brumpt, in 1902; Prof. Arambourg, in 1933; Prof. Arambourg and Dr. Y. Coppens from 1967 to 1972 and many other paleontologist and paleoanthropologist) have been worked in the lower Omo basin for different purposes because it has played a central role in our understanding of vertebrate evolution in more general sense and the evolution of our ancestors and change in their environment as well as cultural evolution of early humans in particular in the region (Howell, 1968, 1978; Coppens et, al.1976;; Alemseged, 1996; Boisserie,

2008). Among the formations of Omo Basin as stated by deHeinzelin and Haesaerts (1983), the

Literature Review

Shungura formation is the most important for its thickness, fossil content and age continuity ranging from 3.6 to 1.05 Ma years (Feibel et al., 1989).

The geology and the paleontology of the Shungura Formation are fairly well known, and its importance for the study of our ancestors (early humans) and other vertebrate evolutions as well as their environment (Alemseged et al., 1996). In this formation the existence of considerable faunal evolution and climatic changes with time has already been globally suggested by different authors (Coppens, 1975 a, b; Gentry, 1985; Beden, 1987). This was supported latter with palynological studies by Bonnefille (1976). Furthermore Geraards and Coppens (1995) have tested these global changes with a multidimensional approach in which they pointed out that these changes were neither regular nor continuous. The use of mammalian faunal assemblage as indicators of mechanism of biological evolution and paleoenvironment and, paleoecology is the most common methods used in the Plio- Pleistocene strata of Africa (Geraards and Coppens,

1995; Vrba, 1980).

Likewise, Beden (1980) worked on the Shungura fossil elephant collections to assess their evolutionary history and how their evolution had been driven by the change in the environment based on their cranial and dental characters within the genus Elephas, particularly in the species E. recki that allows distinguishing five successive stages of the sub-specific value. Also, he suggested that the contribution of Omo elephantids is therefore essential in terms of biostratigraphy of eastern Africa and in terms of the knowledge of the evolution of the family and also these are interesting mammalian groups in terms of its paleoecology ( Beden ,1987).

It is possible to relate the morphological changes in a species over time with changes in the environment such as provide the data of palynology and sedimentology hence, they put in evidence to the climate change in eastern Africa faunal evolution during the late Pliocene and

Literature Review

Pleistocene, in the sense of a gradual drying up accompanied by intense modification of landscape: the distribution of forests and wooded savanna on one hand, on the other hand dry savanna varies over time. These changes correlate with those observed in Elephantidae. In consequence tooth morphology of herbivorous mammals, both primary morphology shaped by evolutionary history and secondary morphology caused by tooth wear, reflects diet and thus vegetation, environmental conditions, and ultimately climate (Saarinen, et al., 2015). Therefore, reconstructing the dietary adaptation of fossil mammals is expected to provide important information on the adaptation of individual species and ultimately on the habitat conditions of terrestrial mammalian paleocommunities (Kaiser and Fortelius, 2003).

Materials and Methods

CHAPTER THREEMATERIALS AND METHODS

3. 1.1 Materials

This study makes use of the selected complete or nearly complete Shungura Formation

Elephantidae, Elephas reck cheek teeth. The Shungura Elephas reck material consists of isolated right and left maxillary and mandibular teeth. The comparative materials include the same dental elements, which belong to Elephas reck that were collected from other eastern Africa Plio-

Pleistocene sites that are found in Ethiopia such as Lower Awash Valley.

The samples include specimens of Plio-Pleistocene fossils of Proboscidea taxa; Elephas reck, which appears after Elephas ekorensis (Beden, 1987). The evolution of cranial and dental characters distinguishes five successive stages of subspecies E. reck brumpti, E. reck shungurensis, E. reck atavus, E. reck ileretensis, and E. reck reck (Beden, 1987). The fossil collections are well documented, and are housed in the ARCCH, Cultural Heritage Collection and

Laboratory Service Directorate in Addis Ababa where this study was conducted.

Information on taxonomic attributions, skeletal element descriptions for the selected dental remains and their stratigraphic levels were retrieved from the Omo specimens’ catalogue. The museum catalogue of the Shungura specimens indicates the locality of each specimen. Based on the available stratigraphic information for the localities (Beden, 1980, 1983, 1987), most of the specimens were assigned to a certain Member (Member B, C, up to Member L) of the Shungura

Formation. The specimens were selected from these members of the formation collected during field seasons in the late 1960s and early 1970s, by both French and American contingent of the

International Omo Research Expedition (IORE), who worked in the northern and southern parts of the Shungura Formation, respectively and also one recently discovered specimen by the Omo

Group Research Expedition (OGRE). Thus, morphological descriptions of the dentition in this study are from the detailed observation and standard measurement of the original material that

Materials and Methods

were recovered and represented in these different members of the Shungura Formation and from published reports cited in the appropriate sections.

A total of averages of 12 complete to nearly complete specimens for each taxonomic group, in each member, were selected when possible. However, in some cases fewer specimens were taken due to availability, for instance E. recki brumpti which is restricted to member B, E. recki ileretensis and E recki recki restricted to members of the upper most sequence of Shungura

Formation. For this study a total of 106 specimens were selected. It is important to note that the degree of preservation varies among different members and also among different taxonomic groups. As a result, the bulk of this study deals with morphometric description and mesowear analysis of the dentition primarily focusing on the upper and lower permanent cheek teeth and hence, a total of 76 upper and lower 1st, 2nd and 3rd molars mesowear angle have been measured. In addition to the complete dental remains, some fragmentary specimens were included when they appear to have distinctive features particularly for mesowear analysis purpose. Deciduous teeth and postcranial remains were not included in this study. This is largely because isolated deciduous teeth are difficult to assign to a species unless they are clearly associated with a taxonomically diagnostic skeletal element. Postcranial remains are also rare in the collection and have no refined taxonomic assignment. The Shungura fossil E. recki specimens considered from each of the member in this work are listed in Table 3. 1.

Materials and Methods

Table 3.1 Number of samples selected for each taxonomic group in the

different members of the Shungura formation.

E.r. E.r. E. r. atavus E.r. ileretensis E.r.recki Total brumpti shungurensis Member B 18 ------18

Member C 6 ------6

Member D 11 ------11

Member E 19 -- -- 19

Member F 7 4 -- -- 11

Member G - 28 -- -- 28

Member H ------Member J ------Member K ------

Member L - -- 5 8 13 Total 43 32 5 18 8 106

3.1.2 The Comparative Materials

Comparative specimens include both original and published fossil materials from various eastern African localities. Original specimens studied here include Middle Awash E. recki materials collected by the Rift Valley Research Mission in Ethiopia (RVRME) and from other

Lower Awash Valley sites, and published dental materials from Middle Awash, Koobi Fora,

Lothagam, and Laetoli, were included in the comparative analysis.

3.2 Methods

3.2.1 Field Work

The most important proportion of fossil vertebrates data are found in sedimentary rocks and those rocks can offer a great deal of information on the death and burial of the organisms and on the environments they inhabited, their age, and their former geographic location. These are all

Materials and Methods

aspects of geological study which are come out from the field and used in paleontological (fossil faunal) analysis and this is mainly collected from exposures of fossiliferous deposits. For these reasons it is important to conduct a field observation on the site to correlate the distribution of proboscidean remains and to estimate their number on each of the sedimentary unit that are selected for the desired study in situ with those of already collected before 40 years ago to understand the nature, distribution and preservation of mammalian fossils contained within the sedimentary rocks. Having this fact, the field work was conducted there in the Shungura

Formation with the Omo Group Research Expedition for more than ten days by demonstrating greatly on the surface survey and to some extent doing excavation. Thus, the group collected more than 400 specimens of fossils of vertebrates including the one newly discovered Elephas recki specimen that has been incorporated in this study.

3.2.2 Laboratory Work

Undertaking laboratory works is the essential part of any paleontological study to confirm their evolutionary history, revise the presence and absence of evolution within the subspecies; the fossil proboscideans have to be measured systematically in controlled manner. To do so, the following different measuring devise such as digital and manual calipers, goniomete, and contour gauge have been used. In addition to these, for some of previously discovered and undescribed specimen and recently discovered specimen of fossil elephants for the purpose of measurement and morphologic description preparation (to uncover the matrix) work in the laboratory was conducted.

Materials and Methods

A B

Figure 3.1 Activity in the field: (A) excavation of OMO 57/4-10010 (Elephas recki Shungurensis) broken lower jaw. (B) OMO 57/4-10010 after recovered from the sediment.

Materials and Methods

Figure 3.2 Activities in the laboratory: plate (C) shows working on the preparation of the specimens selected for this study (D) shows comparative description study.

The present study implements both qualitative and quantitative analysis of the Elephas recki fossil specimens that were recovered from the Shungura Formation. The morphological and metric data collected from the Shungura specimens were compared with published data for E. recki materials from other Plio- Pleistocene sites in eastern Africa. In this study, the morphological description and metric measurements of the Shungura dental specimens were taken from the original specimens.

The methods of dental morphological description, terminologies, and dental measurement techniques are adopted from Maglio (1973), supplemented with some additional methods from other authors (Beden, 1980; 1987; Kalb and Mebrate, 1993;

Materials and Methods

Shoshani and Tassy, 1996). Maglio, in his 1973 monograph, states that vast majority of systematic studies on Proboscidea have been based on the distinguishable and measurable parameters and characters on the molar teeth. The measurements that seem most useful for identification are those that show progressive change along the lineage. Features of molars relevant for the present study include the overall molar length, number of plates or loph(id)s, distribution of accessory conules in transverse valleys, hypsodonty indices [height relative to width of plates or loph(id)s], location of greatest width on the crown, enamel folding patterns, cross-sectional plate shape, configuration of enamel wear figures (including transverse offset of loph(id) or plate halves), plate spacing

(Lamellar frequency), enamel thickness, distribution of cementum, and number of conelets per plate or loph(id).

For the purpose of paleodietary analysis several methods were applicable to fossil mammal teeth and have been developed during the last decades (Cerling et al., 1997; Fortelius and

Solounias, 2000; Fortelius et al., 2003, 2006; Bobe, 2011). Mammal teeth are rich in the fossil record, and they form the basis of research concerning mammal paleocommunities (Kurrten, 1968;

Maglio, 1973; Saarinen et, al., 2015). Tooth morphology of herbivorous mammals, both primary morphology shaped by evolutionary history and secondary morphology caused by tooth wear, reflects diet and thus vegetation, environmental conditions, and ultimately climate analysis.

Reconstructing the dietary adaptation of fossil mammals is expected to provide important information on the adaptation of individual species and ultimately on habitat conditions of terrestrial mammalian paleocommunities.

The approach of reconstructing ungulate diet using, the mesowear method, was first introduced by Fortelius and Solounias (2000). It is based on facet development on the occlusal

Materials and Methods

surfaces of the teeth. The mesowear analysis method has been highly restricted and applicable only for those of mammalian groups that have selenodont (molars with anteroposteriorly elongated, crescent-shaped cusps, like those of ruminants) or ectolophodont (molars with anteroposterior buccal lophs, like those of rhinoceroses) tooth morphologies, because they have buccal ridges showing wear facets in their molars.

However, currently it is possible to extend the method to herbivorous mammals with other kinds of tooth morphology. Saarinen and his colleagues (Saarinen, et al., 2015) propose a new method similar in principle to the original mesowear method that is introduced by Fortelius and

Solounias (2000), but applicable to proboscidean molars for which the traditional mesowear method is not applicable as such. They introduce a new method of dietary analysis for proboscideans similar to the mesowear method, based on angle measurements from worn dentin valleys reflecting the relief of enamel ridges. Thus, regarding the mesowear analysis method principally the mesowear angle measurement procedures in the present study follow those of

Saarinen and his colleagues (Saarinen, et al., 2015). Figure 3.4 illustrates the technique how to measure the mesowear angle for the proboscids dentine valley by using contour gage and goniometer angle measuring device.

Height

Materials and Methods

Fig. 3. 3 Illustrations of Some of the measurable parameters and structural characteristics of Elephas teeth. (Taken from Maglio, 1972)

Materials and Methods

Fig. 3.4 Mesowear angle. A, a lower third molar of E. r. shungurensis (OMO 57/4 10010) from Shungura, Lower OMO; the mesial lamellae are in wear and dentine valleys surrounded by enamel ridges have developed as a result of wear; B, a contour gauge is used here for illustrating the mesowear angles measured from the dentine valleys (angles A and B); C. Magnified form of figure B and, E. Measuring mesowear angle using goniometer.

A C

D, occlusal view of enamel (black line) and dentine valley (grey area) of a central lamella from a lower molar of Loxodonta africana; the mesowear angle is measured from the center of the lamellae where lamellar width is relatively consistent between species (position c rather than from the narrower sides (e.g., position a), or in case of the genus Loxodonta, from the especially widened center ‘loop’ of the lamellae (position b); note that angle b > angle c > angle a (Saarinen et al., 2015).

Materials and Methods

According to Maglio (1973), from the dental characters mentioned above the most important dental criteria are the average number of plate (lamellar frequency), the relative crown height of the unworn plate or hypsodonty index and the thickness of enamel. They provide valuable statistics upon which to base systematic studies, because these characters show progressive change in every lineage and, whereas the overall length varies irregularly, reflecting changes in absolute size of the animals. Before using these measurements it is necessary to appreciate and know what they actually measure and what their limitations are. And also it is necessary to establish the functional relationships between these measured parts and the overall molar morphology.

3.3 Elephant tooth Molar characters used in this study

Plate number: It is one of the most significant features of an elephant tooth in terms of functional morphology (requirements of mastication). It is known that the elephant molar is primarily modified, not grinding one, instead it is a horizontal shearing device (Maglio, 1973). The relationship of the number of plate to functional shearing depends on adjoining changes in the overall size of the molar. Thus, the number of plates becomes an important functional feature of elephant molars, which is directly related to the shearing capacity of the tooth (see figure 3.3B).

Lamellar frequency (LF): Because of the structural limitations of the molar and the overall size requirements determined by skull and mandibular architecture, changes in plate number require correlated changes in other structural features of the tooth. Thus, in order to maintain the molar at a reasonably constant length commensurate with limitations set by the maxilla and dentary, an increase in plate number requires an increase in packing, that is a decrease in absolute spacing of the plates. The lamellar frequency measures this absolute spacing in terms of the number of plates in a standard crown length of ten centimeters (fig.3. 3B). The higher the lamellar frequency, the smaller is the absolute spacing between plates

Materials and Methods

and the greater, therefore, the packing of the plates. Changes in the lamellar frequency can different functional alterations of the molar structure and, therefore, must be considered in relation to other measurements. By itself, the value of the lamellar frequency often can be misleading (Maglio 1973), thus it is important to take care during measurement to minimize the contingency.

Enamel thickness (ET): The enamel thickness is one of the most consistently reliable characters of the elephant molar. It is, therefore, important that standard methods of measurement be applied to this character because this parameter is clearly related to the functional requirements of the elephant molar. As the number of plates increases and their spacing decreases, the enamel thickness is seen to decrease. During measurement, care must be taken to avoid source of error because as observed from the measurement the actual thickness of enamel varies from one part of the plate to another, being generally thicker toward the apex and around the sides of the plate and on median loops, hence, this study follows the measurement procedure that is suggested by Aguirre (Aguirre, 1969) which is averaging a series of measurements along the crown.

Hypsodonty index (HI): The relative crown height of an elephant molar is related to its ability to resist wear. Hence, thick enamel molars are subjected to soft vegetation and they can have lower crown than those that have thinner enamel molars which relied on highly abrasive food (Maglio 1973). When the enamel becomes thinner it results in the decrease their spacing that means the packaging of the plates increase. In the meantime, the rate of occlusal wear increases greatly. This relative crown height, or hypsodonty index, reflects the proportional molar shape by comparing height to width.

A B Materials and Methods

Fig. 3.5 Illustration of measures of elephantids molars (Beden, 1979)

Where: -

L — Length measured at mid- height of the middle Li — Length measured at the base of the plate perpendicular to it. r r r rrnwii

La — Length measured parallel to the occlusal plane.

Ls - Length measured at the apex of the first and the last plates. H — Maximum height measured parallel to middle plate

Materials and Methods

This tends to eliminate size differences that would make it impossible to compare crown height in any functionally meaningful way. Thus, it is not the absolute height which is important here, but the relative height.

Where: - H - The maximum height of the plate. l -

The maximum width of the plate.

Fig. 3.6 Illustration measures of the height and the width of elephant tooth plate (Beden, 1979).

3.4 Terms and Measurement Procedure

Terms and techniques of dental measurement illustrated in the above figures 3.3 to figure

3.6 are used in this chapter to describe proboscidean teeth follow Maglio (1973) and Kalb and

Mebrate (1993). The measurements and indices used in the present study, and the procedures used to obtain them, are taken from Maglio (1973). These are standard for quantitative evaluation of proboscidean molars (see Kalb and Mebrate, 1993), and are summarized in Table 3.2.

Materials and Methods

Table 3. 2 Abbreviations of measurements and terms used in this study Abbreviation Measurement or term

P Number of plates ( in elephants molar)

L Molar length- measured perpendicular to the average lamellar plane

W Molar width- taken across the widest plate, ridge, or loph(id), including cementum

H Maximum molar crown height - measured parallel to the vertical axis of the plate, ridge, or loph(id) from the base of the enamel covering to the apex of the tallest conelet or pillar (greatest width and height of a molar may occur on different plates, ridges, or loph(id)s)

ET Enamel thickness - averaged from a series of measurements taken on worn enamel figures of plates along the molar

HI Hypsodonty index - an index of relative molar crown height, represented as

HI = H X 100/W LF Lamellar frequency - the number of plates per 10cm, averaged from measurements taken at the base and apex along both sides of the molar

+ Indicates a missing portion of a molar

X Anterior or posterior platelets not constituting full plates (an elephant molar with six plates and a posterior platelet, but broken anteriorly, has a plate formula of “ +6x”)

P1, P2... Plates, ridges, or loph(id)s counted from the anterior end of the tooth

PI, PII.. Plates, ridges ,or loph(id)s counted from the posterior end of the tooth

M Molar - “M/” refers to an upper molar and “/M” to a lower molar

Materials and Methods

3.5 Methods of data analysis The biometric (hypsodonty index, enamel thickness, and lamellar frequency) and the mesowear angle measurement raw data were computed using a PAST (PAleontological Statistics) version 3.08 statistical software. In the results section of the biometric and the mesowear angle measurements (to assess the dietary preference of the species) for the five subspecies groups of Elephas recki (such as; E.r. brumpti, E.r. shungurensis, E.r. atavus, E.r. ileretensis and E.r. recki) are reported and presented in Box and Whisker plots, and also graphs. The Mann-Whitney and Kruskal- Wallis tests are employed to see the presence or absence of statistically significant difference in biometric values in the subspecies of Elephas recki, and in the different Members of the Shungura Formation that had records of these taxa (Member B, C, D, E, F, G and L). The hypsodonty index values of the five taxonomic groups considered have a wide range of values in these different taxa. Among the five groups sampled, E. r. ileretensis and E. r. recki show a high hypsodonty of their crown height, while E. r. brumpti, E. r. shungurensis and E. r. atavus show almost similar relatively low hypsodonty index values than other subspecies of Elephas recki (fig. 4.1). The result of the enamel thickness and lamellar frequency values of the selected five subspecies of Elephas recki were also analyzed and tested statistically. The result confirmed that there is a significant difference among these subspecies and throughout Plio-Pleistocene Members of the Shungura Formation. This study focused on comparing classification accuracies of parametric versus non-parametric procedure to see the evolutionary change of E. recki subspecies through time using characters of measurement scheme established by Maglio (1973). In addition to this, the study also gives some morphological description on newly discovered specimen and some older collections that have not been studied and described. Finally, this study introduces the same procedure to predict dietary preference of Elephas recki in general and E. recki subspecies in particular from the mesowear angle measurement result, as recently proposed by Saarinen (Saarinen et al., 2015).

Results

4 CHAPTER FOURRESULTS 4.1 Morphological Description of some new elephantid remains from the Shungura Formation

In this section, some of the proboscidean dental materials from the Shungura Formation, which have not yet been studied, are described in detail. These materials are metrically and morphologically compared with published specimens of subspecies Elephas recki materials from different localities in the region. In the morphological description, an attempt is made to document the intra-specific variation in the entire lineage of Elephas recki. Furthermore, the tempo and mode of changes in the dental morphology, particularly in relation to molar shape, molar curvature, valleys between plates, apical digitations, enamel folding and enamel figure shape of the molars, are discussed for some of the subspecies of Elephas recki.

4.1.1 Systematic Paleontology

Order Proboscidea Illiger, 1811

Super family Elephantoidea Gray, 1821

Family Elephantidae Hay, 1922

Subfamily Elephantinae Hay, 1922

Genus Elephas Linnaeus, 1758

Species Elephas recki Dietrich, 1916

E. recki brumpti Beden, 1980

Results

Table 4.1 Metric data for Elephas recki molars from the eastern Africa sites Elements Specimen number Provenience P L W H LF ET HI (Molars) (in mm) (in mm) (in mm) (in mm)

E. r. brumpti M3 L33-1 +7+ 140+ ? 6.5 2-3.3 ? 68 MA (eastern Bodo) 3 RM OMO 3/0-74-959 Shungura B-12 11 215 75 85 5 4.36 113.33 LM3 OMO 3/0-74-959 Shungura B-12 213 76 85 5 4.15 111.84 11

M3 L 1-33(holotype) Shungura B-11 222.52 82.76 83.45 5 4.22 100.83 11

RM3 KNM-ER 3193 Allia Bay (Area- 9x 178 70? ? 5.5 3.2-3.5 ? 116)

E. r. shungurensis M1 L 78-1 MA 7 177 80 77+ 4.5 1.5 96+ (Matabaietu)

RM1 OMO 57/4-10010 Shungura E-4 8 167 75 ? 5 3.4 ? LM1 OMO 57/4-10010 Shungura E-4 8 165 78 ? 5 3.3 ? RM2 OMO 57/4-10010 Shungura E-4 9+ 172 73 93.71 5.5 ? 128

MI Koobi Fora, 120 60 82 6 2.3 136 KNM-ER 8 350 Bargi Member

(Area-105)

Key for the abbreviations: P= plate number, L= length, W= width, H= height, LF= lamellar frequency, ET= enamel thickness, and HI= hypsodonty index. MA= Middle Awash

Diagnosis: Primitive molars with a small number of plates (12 to 14 to M3); side edges almost rectilinear and slightly converging with parallel faces over the greater part of their height, separated by U-shaped valleys at least as wide as their thickness; Median cylindrical pillars are the same throughout their height apical the end is free sometimes (in the first plates); with wear the median sinus strong, simple, and rounded; thick enamel, bearing a few folds of both sides of the median sinus; low lamellar frequency (close to 4); low hypsodonty index (ranging from 100 to 115 on M3) after Beden (1983). 4.1.2 Description and Comparison

Results

OMO 3/0-74-572 is a left mandible with fairly worn third molar was collected in 1974 by the IORE French contingent. According to the museum catalogue it was recovered from the strata of Member B, Unit 12. Radiometric dating for this position indicates an age of 2.914 ± 0.561Ma.

(Fig. 2.2). This specimen was identified at family level as elephantid.

Biometrically OMO 3/0-74-572 has 11 plates, 229.00 mm long, has an enamel thickness of 4.26 and a plate width of 82 mm. Because of having highly worn enamel plate, the height of its crown is very low and its hypsodonty index is around 115. The enamel fold figures are concentrated at the median digitations with irregularly and coarsely folded.

OMO 3/0-74-959 associated with maxillary right and left third molars collected in 1974 by the IORE French contingent as of the museum catalogue it was unearthed from the strata of member B, Unit 12 and identified as similar as OMO 3/0-74-572 family level Elephantidae finally these two specimens are identified as parts of a single individual.

Biometrically OMO 3/0-74-959 has displayed 11 plates, 213.00 mm long, has an enamel thickness of 4.15 mm and a plate width of 76 mm. Because of having slightly worn enamel plate the height of its crown is comparatively low and its hypsodonty index is around 111.84. Regarding its morphology, the apical digitations are few (4 in number) and the enamel foldings are concentrated at the median digitations with irregularly, coarsely (high amplitude) and loosely spaced enamel folds.

The plate morphology of OMO 3/0-74-572 has been compared with the holotype specimen of E. recki brumpti (L 1-33) and it displays morphologically similar plates. The lateral border of the plates of OMO 3/0-74-572 was also compared with the type specimen.

Likewise the type specimen and the plates of OMO 3/0-74-572 are separated by valleys that are U-

Results shaped and the separated valleys are as wide as the thickness of the plates.

The enamel loops of all plates are curvilinear and slightly concave, particularly at the lingual lateral margin and asymmetrical opposing folds (especially from plate 4 up to plate 7). The shape of the enamel figure displayed a parallel sided with medial fold with regular and high amplitude of enamel folding. The Shungura material was also compared with Allia Bay lower third molar, KNM-ER 3193. Morphologically, they display more or less similar type of enamel folding.

Biometrically the comparison of enamel thickness indicates that the Shungura material displayed thicker enamel (4.26 mm) than the Allia Bay material which has enamel thickness of 3.35 mm.

The Shungura specimen, OMO 3/0-74-572, was also compared with a right lower third molar specimen collected from Middle Awash, eastern Bodo, Sagantole Formation (L 33- 1). All the biometric characters used in this description are relatively similar. In addition, both the

Shungura and Middle Awash molars showed almost similar enamel folding figures.

OMO 3/0-74-572 was also compared with the holotype specimen of the subspecies of E. recki shungurensis (OMO 3/0-74-572 ) and some other specimens of the subspecies, to see whether there is a significant overlap between them or not. Indeed, the stratigraphic of OMO 3/0-

74-572 position could be at the transition because E. recki brumpti and E. recki shungurensis.

However, both the morphological and biometric traits show significant differences between these two individuals. Regarding the morphology, OMO 3/0-74-572 displayed more primitive feature such as enamel figure shape showing parallel sides with median loops of enamel. In addition it displayed more irregular enamel folding, with high amplitude (coarsely folded) and loosely spacing than that of the holotype specimen of Elephas recki shungurensis.

Results

All of the above comparative studies on OMO 3/0-74-572 indicate that both morphological and biometrical results demonstrate that it is comparable with other discoveries from eastern Africa sites (L 1-33, KNM-ER 3193 and L 33- 1), which are already described and known as Elephas recki brumpti. Hence, the new OMO material can be categorized under

Elephas recki brumpti. Furthermore, the stratigraphic position of the described specimen is congruent with this attribution.

Elephas recki shungurensis Beden, 1980

Diagnosis: Cheek teeth with relatively small number of plates (15 x12x to M3), plates with slightly convex lateral edges, nearly parallel throughout their height, median cylindrical pillars generally poorly developed. The mesial pillar, sometimes absent or is always smaller than the distal. Thick enamel, folded only in the central region of the wear figure. Molars relatively low lamellar frequency (close to 5 on M2 and M3) and moderately hypsodont (ranging from 113 to 138 on M3) after Beden (1983).

OMO 57/4-10010 is a mandible bearing worn first right and left molars and unerupted second molar. It was discovered recently in July 2015, during OGRE field season. It was recovered from entirely sandy sediment of Member E, Unit 4, which the adjacent tuff F radiometrically dated

2.324 Ma. ± 0.02 (Fig. 2.2), hence, Member E, Unit 4 is slightly below Member F thus, OMO

57/4-10010 is a bit older than 2.324Ma. (Fig. 2.2). This specimen has many apical digitations (6 in number), and also it displayed relatively strong distal column that results in strong distal median loop, but mesially it displayed a very reduced to no median loop; and the median edge of the enamel figures in this individual are shown separated.

Biometric characters both the right and the left first molars have 8 plates, 167mm and

Results

165mm long respectively, and have enamel thickness of 3.4 mm and 3.3mm, respectively, and both the right and left molars have equal lamellar frequency of 5, and plates width of 75mm and

78mm respectively. The unworn right M/2 has a hypsodonty index value of 128.

OMO 57/4-10010 displays some distinguishable difference from that of the OMO 3/0-

74-572 and OMO 3/0/74/959 (both are E. recki brumpti) from the point of view both of morphology (different type of enamel folding, apical digitations) and biometrics (the enamel is a little thinner, 3.3mm). Overall this specimen clearly displayed more advanced characters than E. recki brumpti, markedly in terms of morphology, and slightly in terms of measurements.

OMO 57/4-10010 has been compared with some other materials already described from eastern Africa sites. First it was compared with the only first lower molar from Koobi Fora, Upper

Burgi Member (KNM-ER 350). The Shungura molar displays more advanced median apical digitations (3-4) than the Koobi Fora (2-3), and in both cases there is no mesial sinus (loop) but the distal is well developed. The enamel is in both cases thinner than that of E. recki brumpti and the

Shungura molar does not provide enamel fold at all.

OMO 57/4-10010 was also compared with right lower first molar (L78-1) from

Matabaietu,Middle Awash. L78-1 is complete and well-worn. Morphologically, the enamel loops are irregular, wrinkled, and possess much reduced distal and mesial folds, particularly on the P 1-5.

The Shungura specimen displays a strong mesial loop rather than median folds. The enamel figure did show parallel sides with distal median loop but not folds. The two specimens have this different morphology (different type of enamel folding and figures). From the point of view of biometrics, there is a significant difference between these two specimens (table 4.13) particularly the enamel of the Shungura specimen is much thicker (3.3 mm) than the Matabaietu specimen, that has very thin enamel thickness (1 mm- 1.5 mm). Overall this specimen clearly shows significant

Results morphologic and biometric difference from that of the Matabaietu specimen.

Figure 4.1. OMO 3/0-74-959 Elephas recki brumpti occlusal view.

Results

Figure 4.2, recently discovered OMO 57/4-10010 Elephas recki shungurensis occlusal view.

4.2 The evolution of Hypsodonty Index within the five taxonomic groups

What do the hypsodonty index values within paired subspecies and the entire subspecies of Elephas recki lineage indicates about the evolutionary pattern of these taxa? The hypothesis drawn in this study is that the high hypsodonty index values in Elephas recki lineage molars shown in the youngest subspecies of the lineage than the oldest subspecies.

The Chi-Squared tests were used to determine whether the presence or absence of evolutionary change based on the change in hypsodonty index values over time or were constant within the lineage of subspecies Elephas recki. A statistically significant result from the Kruskal-

Wallis probability test (Table 4.2) which is much less than 0.05 indicates that the observed

Results distribution of hypsodonty index in the entire group of subspecies of Elephas recki result departs from a uniform (even) distribution that indicates there is statistically significant difference among the values of their hypsodonty index.

In order to test whether or not hypsodonty index variables experienced monotonic trends within the entire, and each subspecies through time, two non-parametric statistics were employed:

Kruskal-Wallis and Mann-Whitney pair-wise tests. Both of these correlations tests are determining whether or not the dependent (hypsodonty index) variable is a monotonic function of the independent variable (subspecies of the lineage), in the analyses here being examined.

Overall it can be concluded that E. r. brumpti, E. r. shungurensis and E. r. atavus had displayed relatively low hypsodonty index through their evolution, on the contrary, the other two subspecies of this lineage such as E. r. ileretensis and E. r. recki had displayed extremely high hypsodonty index compared to the others (Fig. 4.3).

Results

Figure 4.3 Box plots of the

hypsodonty index values of

Elephas recki subspecies from Shungura Formation.

Each box represents 50% of

the data with the median

values and the whiskers representing 25% of the data.

4.3 The Evolution of Hypsodonty through the Members of the Shungura Formation

In this section, the hypsodonty index values of the five taxonomic groups were computed to see whether there is a significant difference hypsodonty among them or not. As compared and tested, Kruskal-Wallis: chi-square test (table 4.2) indicates that there is a significant difference in hypsodonty index values of the entire five taxonomic group of subspecies of Elephas recki lineage from members of the Shungura Formation.

Results

Table 4.2 Probability (p) and statistical summary for Hypsodonty Index values of the five

E.r. brumpti E. r. shungurensis E. r. atavus E . r. ileretensis E. r. recki

N 14 38 28 6 6 Min 100.83 101.2 102.04 132.94 176.04 Max 147.52 164.42 169.45 193.94 210 Mean 125.3186 126.3989 137.3693 165.2883 197.68 Var. 223.3745 241.5829 471.9013 475.6347 187.7962 SD 14.94572 15.54294 21.72329 21.80905 13.70388 Median 127.485 125.825 139.55 171.06 201.985 2 Chi = 29.89, p<<0.0001 taxonomic group of Elephas recki lineage from the Shungura Formation:

Table 4.3 Mann-Whitney pair tests: for hypsodonty index values of the five taxonomic group of

Elephas recki from the Shungura Formation:

E r brumpti E r shungurensis E r atavus E r ileretensis E r recki

E r brumpti 0.9015 0.09806 0.0006197 0.002608 E r shungurensis 0.9015 0.05086 0.0006669 0.0001038

E r atavus 0.09806 0.05086 0.009388 0.0001618 E r ileretensis 0.0006669 0.009388 0.01307 0.002608 E r recki 0.0006197 0.0001038 0.01307 0.0001618

Results

Memb Memb Memb Memb E Memb F Memb Memb Memb B C D G LL UL N 14 5 9 17 11 24 5 8 Min 100.83 117.44 101.2 107.94 102.82 102.04 132.94 123.08 Max 147.52 159.63 130.6 143.52 167.36 169.45 193.94 210 Mean 125.318 132.454 114.325 128.260 134.535 137.415 164.842 180.107

6 6 6 5 8 Figure 4.45 Box plots of the Varianc 223.374 259.288 134.283 104.512 674.209 405.593 593.049hypsodonty 1198.16 index values of e 5 4 7 5 4 3 Elephas 6recki from different SD 14.9457 16.1024 11.5880 10.2231 25.9655 20.1393 24.3526members 34.6145 of the Shungura 4 5 5 5 5 3 2 Formation. Each box Median 127.485 129.53 111.11 126.61 129.48 139.55 174.6 192.335 represents 50% of the data Chi 2 = 27.87, p= 0.0002 with the median values and the whiskers representing

25% of the data.

Table 4.4 Probability (p) and statistical summary of Hypsodonty Index values of subspecies of

Elephas recki from members of the Shungura Formation:

Results

Table 4.5 Mann- Whitney pair tests: for hypsodonty index values of subspecies of Elephas recki from Members of the Shungura Formation: Memb Memb Memb Memb Memb Memb G MembLL MembUL

B C D E F

Memb B 0.08889 0.7964 0.4938 0.08453 0.006311 0.004619 0.6106 Memb C 0.06195 0.8142 0.665 0.03671 0.03379 0.6106 1 Memb D 0.08889 0.06195 0.0152 0.09464 0.0043 0.003353 0.001764

Memb E 0.7964 0.8142 0.0152 0.7778 0.1492 0.006105 0.004723

Memb F 0.4938 0.0946 0.7778 0.7899 0.04143 0.007283 1 Memb G 0.0845 0.665 0.0043 0.1492 0.7899 0.02623 0.004365

MembLL 0.0063 0.0367 0.00335 0.0414 0.02623 0.2723 0.0061 MembUL 0.0046 0.0337 0.00176 0.0047 0.0072 0.00436 0.2723

However, the results of hypsodonty index values of the five taxonomic groups were evaluated accordingly with the Mann-Whitney pair-wise tests to examine if there is a significant difference value of hypsodonty index between subspecies within paired Members of the Shungura

Formation. Hence, the raw data has been calculated and shown by Box and Whisker plot (fig. 4.4) and statistical summary shown in (table 4.4). As can be seen from the hypsodonty index values of

Elephas recki subspecies starting from Member B (2.91 Ma.) all the way to Member G (2.27 - 1.91

Ma.) except as of the result the significant difference seen between materials from Members D and E

[E. r. shungurensis (Mann-Whitney: p= 0.015)], and also materials from Members D and G [E. r. shungurensis and E. r. atavus (Mann- Whitney: p= 0.004)] there is no significant difference in the values of hypsodonty index and in addition to this and exceptionally the average hypsodonty index value in the subspecies from Member D is relatively very low among the subspecies evolved during the Plio- Pleistocene. On the other hand, the result of the hypsodonty index value of youngest

Results materials from Member L (E.r. ileretensis and E. r. recki) considered and compared with oldest materials from Member B all the way to Member G the Mann- Whitney test shows that the difference is statistically significant (table 4.5).

Thus, among the selected materials from the entire members for this study, materials from

Member L (E.r. ileretensis and E. r. recki) show exceptionally higher hypsodonty index values than materials from the rest of the Members. However, as mentioned earlier the average hypsodonty index value of materials from Member D is very low. Therefore, if high hypsodonty index values in the youngest member (Member L) in the Shungura Formation indicate an evolution of molars toward greater hypsodonty through time (in E. r. ileretensis andE. r. recki), this does not appear as a gradual, progressive trend (like Member D).

4.4 The evolution of Enamel Thickness within the five taxonomic groups of Elephas recki

The enamel thickness values of the five taxonomic groups of Elephas recki were evaluated.

To assess if there is statistically significant difference among the values of enamel thickness these taxonomic groups of Elephas recki the same statistical methods employed for the hypsodonty index are applied in this section as well.

As evaluated using Kruskal-Wallis: Chi square probability value test given in table

4.5, Mann-Whitney tests for paired subspecies and paired Members of subspecies were evaluated and compiled, and presented in Box and Whisker plot (Fig.4.5 and Fig. 4.6 respectively). There are statistically significant differences in the values of enamel thickness of the entire subspecies (Table

4.4) and also subspecies of Elephas recki from individual Members of the Shungura Formation

(Table 4.5).

Results

Table 4. 6 Probability (p) and statistical summary of enamel thickness values of subspecies of Elephas recki from the Shungura Formation: E. r. E. r. E. r. atavus E. r. E. r. recki brumpti shungurensis ileretensis

N 18 41 31 5 8

Min 3.32 2.38 2.9 2.5 2.6 Max 4.52 3.66 3.95 3.31 3.01 Mean 4.016667 3.165854 3.273548 3.078 2.73625 Variance 0.1170235 0.08489988 0.136697 0.03397 0.03242679 SD 0.342087 0.2913758 0.3697256 0.1843095 0.1800744 Median 4.03 3.2 3.33 2.99 2.775 2 Chi = 47.27; p<<<0.001

E r recti

E r ilenet

E r atavus Figure 4.5 Box plots of the enamel thickness values of Elephas recki E r shungc subspecies from the Shungura Formation. Each box represents 50% of the data with E r brum pi: the median values and the whiskers

representing 25% of the data.

2.1 2.4 2.7 3.0 3.3 3.6 3S 4.2 4.5 4.3

Enamel thickness (in mm)

Results

Table 4.7 Probability (p) and statistical summary of the Enamel Thickness values of subspecies of Elephas recki from members of the Shungura Formation: Memb B Memb C Memb D Memb E Memb F Memb G Memb LL Memb UL N 18 6 11 17 7 31 5 8 Min 3.32 2.9 2.84 2.6 2.64 2.38 2.9 2.5 Max 4.52 3.47 3.49 3.66 3.54 3.95 3.31 3.01 Mean 4.016667 3.246667 3.285455 3.092941 3.08571 3.27354 3.078 2.73625 Var 0.117023 0.048786 0.051247 0.097784 0.12386 0.13669 0.03397 0.032426 SD 0.342087 0.220877 0.226378 0.312705 0.35194 0.36972 0.18430 0.180074 Median 4.03 3.3 3.4 3 3.2 3.33 2.99 2.775

Chi = 49.7, p<<<0.0001

Table 4.8 Mann- Whitney pair tests: for enamel thickness values of the five taxonomic group of Elephas recki from the Shungura Formation:

E r brumpti E r shungurensis E r atavus E r E r recki ileretensis E r brumpti 2.823E-08 7.902E-07 0.0008945 6.979E-05

E r 2.823E-08 0.1703 0.349 0.0009994 shungurensis E r atavus 7.902E-07 0.1703 0.156 0.001008 E r ileretensis 0.0008945 0.349 0.156 0.01884

E r recki 6.979E-05 0.0009994 0.001008 0.01884

Results

Memb UL Memb LL Memb G Memb F Memb E

Memb D Memb C Memb B

2.1 2.4 2.7 3.0 3,3 3,6 3,9 4,2 4,5 4.3 Enamel thickness (in mm)

What do the enamel thickness values within paired subspecies and the entire subspecies of Elephas recki lineage indicate about the evolutionary trend of these taxonomic groups? My hypothesis in this regard is that the enamel thickness is seen to decrease or become thinner progressively in Elephas recki lineage during the Plio-Pleistocene: older subspecies have thicker enamel than younger ones through time.

As can be seen from the result of enamel thickness values on the statistical summary illustrated in (table 4.4) and Box plot in (figure 4.5), the oldest subspecies in the lineage Elephas

Results recki brumpti has shown evidence of exceptionally thicker enamel thickness values than the rest of the subspecies following chronologically in the lineage. On the other hand, the youngest subspecies in the lineage, E .r. recki displayed remarkably thinner enamel thickness than the rest of the subspecies in the lineage.

Results

The Mann-Whitney enamel thickness values tests from Members of the Shungura

Formation as illustrated in (table 4.6) there is a significant difference in enamel thickness values within subspecies from paired Members of the Shungura Formation. Since it can be seen from the result the enamel thickness values in Member B and Member UL show statistically significant difference between subspecies from the corresponding Members that are shaded in similar color, and also the enamel thickness values of subspecies in the upper most Member L (UL) except subspecies in Member F, all the subspecies from the rest of the Members show statistically significant difference between subspecies from corresponding Members that have indicated with bold texts.

In general, from the results it can be concluded that subspecies from the oldest Member B records thicker enamel thickness than the rest of subspecies in all Members (such as, Member C all the way to Upper- Member L). However, in contrast to the above result, subspecies from the youngest Member that is; the upper most Member L (UL) has recorded thinner enamel thickness.

While, some of the subspecies in the intermediate Members (between Members B and C and also Members LL and UL) clearly displayed and showed remarkable sudden evolutionary decrease in enamel thickness. In this regard, the results indicate that there is no clear progression of evolutionary trend. Nevertheless, the results indicate that a decrease in enamel thickness is a tendency to become more advanced subspecies in the Elephas recki lineage throughout the Plio-

Pleistocene (Fig. 4.5 and table 4.6)

Results

Table 4.9 Mann- Whitney tests: For enamel thickness values of subspecies from Members of the Shungura Formation: Memb. B Memb. C Memb. D Memb. E Memb. F Memb. G Memb. LL Memb. UL Memb B 0.00152 0.000109 2E-06 0.0003931 7.9E-07 0.0008945 6.97E-05 Memb C 0.00152 0.5797 0.2306 0.5672 0.8047 0.2722 0.00442

Memb D 0.000109 0.5797 0.08056 0.2388 0.9886 0.08902 0.000816 Memb E 2E-06 0.2306 0.08056 0.949 0.09224 0.6359 0.01391 Memb F 0.0003931 0.5672 0.2388 0.949 0.1938 0.871 0.07259

Memb G 7.90E-07 0.8047 0.9886 0.09224 0.1938 0.156 0.001008 Memb LL 0.0008945 0.2722 0.08902 0.6359 0.871 0.156 0.01884

Memb UL 0.00442 0.000816 0.01391 0.07259 0.001008 0.01884

4.5 The evolution of Lamellar Frequency within the five taxonomic groups of Elephas recki

The other parameter which this study evaluates is values of lamellar frequency. The values of lamellar frequency of the Shungura Elphas recki lineage were compared by Kruskal-

Wellis test as illustrated below in table 4.10. There is a significant difference among the values of the lamellar frequency of the five taxonomic groups. Table 4.10 Probability (p) and statistical summary for lamellar frequency values of subspecies of Elephas recki from the Shungura Formation: E. r. brumpti E. r. shungurensis E. r. atavus E. r. ileretensis E.r. recki N 18 37 31 5 8 Min 4 4 4.5 5.5 6 Max 5 6.5 6.5 6 6.5 Mean 4.666667 5.432432 5.435484 5.7 6.1875 Variance 0.1764706 0.3216967 0.2790323 0.075 0.06696429 SD 0.420084 0.5671831 0.528235 0.2738613 0.2587746 Median 5 5.5 5.5 5.5 6 Chi2 = 36.15, p <<<0.0001

As confirmed by Mann-Whitney paired tests for the lamellar frequency values of

Results subspecies of Elephas recki lineage as illustrated in table 4.10 and Box plot in figure 4.7, there is a significant difference in lamellar frequency values within subspecies for paired samples of

Elephas recki lineage from the Shungura Formation. As it can be seen from the result, the lamellar frequency values in Elephas recki brumpti shows statistically significant difference between subspecies from paired Members of the Shungura Formation, and also the lamellar frequency values of Elephas recki recki in the lineage displayed statistically significant different values of lamellar frequency with all of the subspecies older than E. r. recki subspecies (table 4. 10).

Table 4. 11Probability (p) and statistical summary for the lamellar frequency values of subspecies of Elephas recki from members of the Shungura Formation: Memb B Memb C Memb D Memb E Memb F Memb G Memb Memb LL UL

N 18 6 11 17 11 27 5 8 Min 4 4.5 4.5 4 5 4.5 5.5 6 Max 5 6.5 6 6 6 6.5 6 6.5 Mean 4.666667 5.416667 5.272727 5.617647 5.409091 5.462963 5.7 6.1875

Var. 0.17647 0.541666 0.36029 0.140909 0.306267 0.075 0.06696 0.218181 4 SD 0.42008 0.73598 0.467099 0.600245 0.375378 0.55341 0.273 0.25877 6 Med 5 5.25 5.5 5.5 5.5 5.5 6 6 Chi2= 43.61, p<<< 0.0001

Results

Table 4.12 Mann- Whitney tests: For lamellar frequency values of subspecies from the Shungura Formation:

E r brumpti E r shungurensis E r atavus E r ileretensis E r recki E r brumpti 1.656E-05 1.343E-05 0.0004932 3.752E-05

E r 1.656E-05 0.8175 0.3387 0.0004633 shungurensis E r atavus 1.343E-05 0.8175 0.2295 0.000604 E r ileretensis 0.0004932 0.3387 0.2295 0.01938

E r recki 3.752E-05 0.0004633 0.000604 0.01938

Figure 4.7 Box plots of the lamellar frequency Figure 4.8 Box plots of the lamellar frequency values of Elephas recki subspecies from the values of Elephas recki subspecies from the Members of the Shungura Formation. Each box Shungura Formation. Each box represents 50% of represents 50% of the samples with the median

the samples with the median values and the values and the whiskers representing 25% of the data. whiskers representing 25% of the data.

Results

Table 4.13 Mann- Whitney tests: For lamellar frequency values of subspecies from Members of the Shungura Formation: Memb B Memb C Memb D Memb E Memb F Memb G Mem LL Mem UL

Memb B 0.02376 0.002371 4.701E-05 0.00016 2.41E-05 0.0004932 3.752E-05 Memb C 0.02376 0.8334 0.4552 0.9161 0.8095 0.4493 0.04834 Memb D 0.002371 0.8334 0.03226 0.6187 0.3618 0.07889 0.0004578

Memb E 4.701E-05 0.4552 0.03226 0.08882 0.1777 0.7936 0.005036

Memb F 0.00016 0.9161 0.6187 0.08882 0.7359 0.1569 0.00092

Memb G 2.41E-05 0.8095 0.3618 0.1777 0.7359 0.3276 0.00126 Mem UL 0.0004932 0.4493 0.07889 0.7936 0.1569 0.3276 0.01938

Mem UL 3.752E-05 0.04834 0.0004578 0.005036 0.00092 0.00126 0.01938

The Mann-Whitney lamellar frequency values tests for Members of the Shungura Formation as illustrated in table 4.10, there is a significant difference in lamellar frequency values within subspecies from paired Members of the Shungura Formation. Provided that it can be seen from the result the lamellar frequency values in the oldest Member B and in the youngest Member UL shows statistically significant difference and also there is a significant difference in lamellar frequency values between subspecies from Member D and Member E. In addition to these, the lamellar frequency values of subspecies in the upper most Member L (UL) and all the lamellar frequency values of subspecies from the paired Members show statistically significant difference between subspecies from paired Members that were indicated with bold-texts. Thus, the average lamellar frequency values that have been evaluated in both subspecies and Member wise indicate that to some extent there is a tendency to increase gradually in the values of lamellar frequency within the subspecies of Elephas recki through Plio-Pleistocene of Lower Omo Shungura Formation.

Results

4.6 Comparison of enamel thickness versus hypsodonty index, and lamellar frequency

In addition to evaluation of individual biometric characteristics, the study must also consider some of dependent comparable traits, which vary in the history of evolution of proboscideans in more or less the same way, but with the different tempo; that is there are some biometrical trends in the different evolutionary trends of these animals. These comparable traits include the linear regression between the average values of hypsodonty index and enamel thickness, and also between the average values of lamellar frequency and enamel thickness, in both cases the comparisons are illustrated below to see their correlation with the help of figures (Fig. 4.9 and 4.10) respectively.

This study calculated using linear regression between the average values of enamel thickness corresponding to the averaged values hypsodonty index and also the average enamel thickness values corresponding to the average lamellar frequency values of the five taxonomic groups of Elephas recki lineage from the Shungura Formation, in both cases as illustrated in figures (Fig.4.7 and Fig. 4.8) respectively the results show a weak but statistically significant negative correlation.

Results Hypsodonty index

Figure 4.9 Linear regressions (Ordinary Least Squares Regression) of mean hypsodonty index values and enamel

thickness for the molars (M2 and M3) Enamel thickness sampled from Elephas recki lineage from Shungura populations. The 95% confidence limits are shown as blue colored solid lines. R2=0.1463, p = 0.0001 and.

Enamel thickness

Lamellar frequency Figure 4.10 Linear regressions (Ordinary Least Squares Regression) of enamel thickness values and lamellar frequency for the molars (M2 and M3) sampled from Elephas recki lineage from Shungura populations. The 95% confidence limits are shown as blue colored solid lines. R2=0.2127, p << 0.0001 and slop = -0.36.

4.7 Tooth wear-based dietary analysis for the five taxonomic groups of Elephas recki

This study also compared the average mesowear angle in the entire Elephas recki lineage to see and understand their paleodietary preference both in subspecies wise and member wise as well.

Results

Figure 4. 11. C3/C4 dietary spectrums of proboscideans from tropical Africa and Asia with boundary values of S13C and the corresponding (mean) mesowear angles.

The result shows that there is no statistically significant difference in the average mesowear angle values both in subspecies and member wise (except the pair-wise comparison of average mesowear angle values difference which can be seen only between Member D and E,

Mann-Whitney: p= 0.046) of the five taxonomic groups of proboscideans (Elephas recki lineage) from the Shungura Formation (Fig. 4.14 and 4.15) respectively.

Table 4.14 Probability (p) and statistical summary for the mesowear angle values of subspecies of Elephas recki from the Shungura Formation:

E r brumpti E r shungurensis E r atavus E r ileretensis E r recki N 9 31 28 4 4 Min 113.5 108.7 112 120 120.7 Max 130 139.5 152.3 126.7 126 Mean 123.0778 124.8365 127.7261 123.675 123.525 Var. 40.62444 99.39992 108.8818 7.6225 7.389167 SD 6.373731 9.969951 10.43464 2.760888 2.718302 Med. 126 124 127.65 124 123.7

Chi2= 1.729, p = 0.7854

Table 4.15 Probability (p) and statistical summary for the mesowear angle values of subspecies of Elephas recki from members of the Shungura Formation:

Results

Memb B Memb C Memb D Memb E Memb F Memb G Memb L N 9 6 9 12 4 28 8 Min 113.5 116.3 109.2 108.7 109.7 112 120 Max 130 138.3 135 139.5 129.3 152.3 126.7 Mean 123.0778 125.405 120.17 129.519 120.85 127.665 123.6 Var. 40.62444 86.80295 89.843 289.7422 94.6233 4110.4994 6.44 SD 6.373731 9.31681 9.478 9.4732 9.7274 10.5118 2.5377 Med. 126 123.25 119.7 133.2 122.2 127.65 124 2 Chi =7.62, p = 0.2671

Figure 4.12 Box plots of mesowear angle values of Figure 4. 13 Box plots of mesowear angle values of

Elephas recki subspecies from the Shungura Elephas recki lineage from Members of the

Formation. Each box represents 50% of the samples Shungura Formation. Each box represents 50% of

with the median values and the whiskers the samples with the median values and the

representing 25% of the data. whiskers representing 25% of the data.

The analyzed average mesowear angle values for the five taxonomic groups of Elephas recki lineage both in subspecies wise (table 4.13) and in Member wise (table 4.14) result which is indicating a dietary adaptation that range from a slightly mixed C3/C4 to a more C4 dominated diet. Overall it can be concluded that the entire lineage of Elephas recki from the Shungura Formation had a more C4 grass- dominated diet throughout the Plio- Pleistocene; however, there is some fluctuation in the mean mesowear angle values in the

Results different members of the formation and the values range from 130o [(n= 12; Member E)] to 120.17 o [(n= 9;

Member D)]. In Members B, D and F the mean mesowear angle values 123.1 o, 120.17 o and 120.85 o respectively indicated that mixed C3/C4 diet (Fig. 4.9). On the other hand, subspecies in Members C, G and

o o L the mesowear angle values 125.4 , 127.7 o, and 124 respectively indicated that a more C4 dominated diet whereas, the subspecies in Member E with the mean mesowear angle value of 130o indicated that slightly pure C4 diet (Fig. 4.11).

Discussion

DISCUSSION CHAPTER FIVE

5.1 Discussion on the comparative description of specimens of Elephas recki from the Shungura Formatiom

The comparative morphological description between the Shungura (OMO 3/0-74959); as of the comparative results attributed as Elephas recki brumpti and Middle Awash Elephas recki brumpti indicates that the molars from both sites displayed similar morphologic and biometric characters except the lamellar frequency of the Middle Awash molar demonstrated 6 and a half plates (table 4.1) whereas, the Allia Bay molar demonstrated almost similar in morphologic and biometric characters except that the enamel thickness of the Shungura material is relatively thicker than that of the Allia Bay specimens.

The other morphologic and biometric comparison made in this study is that the Shungura mandibular associated molars are attributed to Elephas recki shungurensis with the other eastern

Africa localities. Regarding the morphologic characters it shows some advanced features such as, unfolded enamel figures, very reduced or has no median folds while concerning the biometric characters it retains the primitive feature like the enamel thickness (3.4 mm) thicker than the

Metabaietu molar which has provided remarkable thinner enamel thickness of 1.5 mm.

Furthermore, the Koobi Fora first molar was compared with the Shungura specimens, morphologically the Shungura specimen provide more advanced apical digitations (4 apical digitations) than the Koobi Fora specimen (2 to 3 apical digitations) . Generally, the dentitions of the two sites (Shungura and Koobi Fora) have shown morphologic and biometric overlaps in some of the characters. Therefore, the combination of both morphologic and biometric data resembled and had to be categorized into the same taxonomic unit as Elephas recki shungurensis.

Discussion

5.2 Evolution of Hypsodonty Index through the Shungura Formation

The first hypothesis examined in this study is that, of a significant difference in the mean values of hypsodonty index between the subspecies of Elephas recki through time in the Shungura

Formation. The results from the analyses of the hypsodonty index mean values in the previous chapter

(Table 4.2) largely confirm that there is a significant change in the mean values of the hypsodonty index that is; the molars of the youngest subspecies became more hypsodonty molars through time than that of the older forms of the subspecies of Elephas recki in the Shungura Formation. Thus, this hypothesis was strongly supported by the analysis of the result presented in the previous chapter particularly the two youngest subspecies of the lineage; E. recki ileretensis and E. recki recki have provided a strong support for the hypothesis because they both displayed high hypsodonty molars than the other three subspecies of the lineage (Table 4.3).

There is also statistically significant difference among mean hypsodonty index values of subspecies of Elephas recki from Members of the Shungura Formation. In this study generally subspecies (E. r. ileretensis and E. r. recki) from Upper and Lower Member L (1.3 to 1.0 Ma) show that remarkable high hypsodonty molars than subspecies coming from the rest of the Members (i.e. E. r. brumpti, E. r. shungurensis and E. r. atavus). The results of this study indicate that the subspecies has relatively low hypsodonty index molars in the lower members of the formation, which later evolved to principally high hypsodonty index molars in the upper members.

From previous literature, the initial hypothesis was that the evolution of high hypsodont molars in this lineage followed a monotonic trend of progressive increase of the crown height.

Overall, the results support the notion that there was significant increase in crown height (more hypsodont molars) in the basin throughout the period sampled by the Shungura Elephas recki. Lister

(2013) pointed out from his study on evolution of hypsodonty index in the family Elephantidae

Discussion

(particularly in Elephas recki) a remarkable progressive incremental transformation through their evolutionary history (Fig. 5.1A). However, in the present study, even though there is a remarkable increment in the hypsodonty index values in the lineage, there is no progressive increase. Instead it shows a relative stasis between 3 Ma and 2 Ma, then a sudden increase in the latest subspecies (Fig.

5.1B).

A Figure 5.1 (A) Incremental evolution of hypsodonty index in the African Plio-Pleistocene Elephas recki/iolensis lineage. (Circles) E. recki/iolensis from North Africa (squares) and southern Africa (diamonds); Taken from (Lister, 2013), and (B) Data from this study: evolution of hypsodonty index within the subspecies lineage of Elephas recki.

Discussion

5.3 Evolution of Enamel thickness through the Shungura Formation

Another major trend in the evolution of elephant’s molars in general was a decrease in the enamel covering of the molar crown, the second hypothesis examined in this study was that, the enamel thickness progressively became thinner through the lineage during the Plio-

Pleistocene. The analyses presented in the result section generally support this hypothesis, but with major differences in the two extremity subspecies of the lineage that is; E. r. brumpti (3.0

Ma), oldest and E. r. recki (1.0Ma) youngest in the lineage in both the analysis of subspecies and member wise. The average enamel thickness results of Elephas recki for each of the subspecies from the Shungura Formation more or less tends toward thinning from about 4.0 mm in E. r. brumpti to a significant reduction was achieved by E. r. recki in which enamel is about 2.7 mm in thickness.

Among the rest of the lineage in both the analysis of subspecies and member wise however, the differences in the mean values of the enamel thickness were not statistically significant, and they were comparable between E. r. shungurensis, E. r. atavus, and E. r. ileretensis (table 4.3). This indicates that there is a very strong overlap in biometric characters for the three subspecies and enamel thickness is relatively comparable between E. r. shungurensis,

E. r. atavus, and E. r. ileretensis.

In general, the pattern of enamel thickness change through time in the Shungura Elephas recki is complex, and my results for the entire lineage do not provide strong support for a progressive directional shift in enamel thickness values through time (table 4.8).

It is important to remember here that the number of samples selected for the present study is small and the values are not significantly different in some members as mentioned earlier to have concrete evidence. It is therefore, necessary to incorporate more data from the Shungura to confirm the enamel evolution of the group. Yet, the following figure (fig. 5.2),

Discussion

which has been done by Maglio (1972), showed the significant evolutionary change in the enamel thickness through time among the three genera of elephants. Enamel thickness 2.5 3 3.5 4

H ♦ ♦ 4# ♦♦

♦ »♦ # Ml—W> M ♦»# ♦ in millions of years of millions in

* 4

♦♦♦ AtC ♦ *♦ Age ♦ ♦ ♦ ♦♦

O mm 3.0 tnom#l True knot A B

Fig. 5.2 Evolutionary change in enamel thickness: (A) of three elephant lineages. Maglio, 1972. And (B)

Data from this study: evolution of enamel thickness within the subspecies lineage of Elephas recki

5.4 Evolution of lamellar frequency of the five taxonomic groups of

Elephas recki lineage from the Shungura Formation

The results of lamellar frequency in this study demonstrate that there is statistically significant difference within the subspecies that are selected for this study (Table 4.10 and 4.11). The result confirms that there is a significant change in lamellar number, i.e., the molars of the youngest subspecies recorded more lamellar number through time than that of the oldest ones in Elephas recki lineage from the Shungura Formation. The following figure (fig. 5.3) which has been done by Maglio (1972), showed the significant evolutionary change in the lamellar frequency through time among the three genera of elephants.

Discussion

A B

Fig. 5.3 Evolutionary change in lamellar frequency of three elephant lineages: (A) of three elephant lineages.

Maglio, 1972. And (B) Data from this study: evolution of lamellar frequency within the subspecies lineage of

Elephas recki.

Thus, the evolution of lamellar frequency in the Elephas recki lineage also represents a slightly incremental transformation particularly in the youngest subspecies of the lineage. E. recki recki have provided an evidence for slightly incremental evolution of lamellar frequency. However, as a result, in some of the species the relative packing of plates per unit molar length increased drastically as the number of plates increased, for instance, in Loxodonta the lamellar frequency (3 to

4 plates) change little whereas in Mammuthus reached up to 9 plates in 10 cm unit length during the

Discussion same period of time (Maglio, 1972; Beden, 1983). In this study the trend in the evolution of lamellar frequency holds true for the Elephas recki lineage from the Shungura Formation.

From linear regression analysis results of the average values of enamel thickness corresponding to the averaged values hypsodonty index and also the average enamel thickness values corresponding to the average lamellar frequency values of the five taxonomic groups of

Elephas recki lineage from the Shungura Formation, in both cases as illustrated in figures (Fig.4.9 and Fig. 4.10) respectively the results show a weak but statistically significant negative correlation.

From these results even though there are some significant overlaps values within the subspecies clearly show that there is a general trend that follows an increase in one trait brings a decrease on the other trait.

More specifically, from the hypsodonty index, the thicker the enamel thickness the lower the hypsodonty index value, this indicated that the older the species the thicker the enamel that is E. r. brumpti demonstrated a lower hypsodonty index value, but a thicker enamel in contrast to this E. r. recki which is the youngest subspecies in the lineage displayed remarkable high hypsodonty index value with remarkable thinner enamel thickness.

The situation holds true for the relation between enamel thickness and lamellar frequency the younger subspecies in the lineage; E. r. recki recorded thinner enamel thickness than the older individual this can confirm that the evolution of large numbered lamellar frequency has been derived by the thickness of the enamel younger subspecies displayed thinner enamel with more number of lamellar frequency E. r. recki older subspecies in the lineage displayed lesser number of lamellar frequency. 5.5 Paleoenvironments and dietary adaptations of Elephas recki

As can be referred from the paper by Coppens (1978), there were seven proboscidean species represented in the Shungura; Anancus kenyensis, Stegodon kaisensis (both occurred below tuff C), as

Discussion well as Loxodonta adaurora and other two Loxodonta species occurred possibly below tuff E. Two other species, Deinotherium bozasi and Elephas recki, were found everywhere in this formation, and comprised 98 per cent of the specimens (Coppens, 1978). Therefore, the two species are the most abundant proboscidean species in the Shungura Formation, even though their abundance varies from member to member.

The modern representatives of elephants (Elephas maximus) are browsers (Saarinen et al.,

2015), with hypsodont teeth (Maglio, 1972, 1973). An isotopic study of modern Elephas; E. maximus also shows that their diets are characterized by C3-dominated diet (Saarinen et al., 2015).

The subspecies Elephas recki from the Shungura are interesting to study the paleodiet because they are seen to evolve from the lower Member B to upper Member L in its stratigraphic section; as can be seen from the discussion section in the above they significantly modified their molars morphologic and biometric features; these modifications probably associated with their diet preferences through time may derived by environmental pressure (Maglio, 1972, 1973; Coppens, 1978; Williams and Kay, 2001;

Todd, 2006).

Dietary analyses of E. recki are also important for paleoecological reconstruction. As the methods adopted from the work of Saarinen and his colleagues (2015), the results of this study show that the average mesowear angle values of Elephas recki lineage from the Shungura Formation statistically have no significant difference (table 4.14) within the subspecies of the lineage with time. Their mesowear angle values with no significant change show a consistent C4 dominated diet during the Plio-

Pleistocene, table 4.15.

Nevertheless, even though there is no statistically significant change in their mesowear angle values within the entire subspecies from each member, some of the subspecies from the group has varied with time, there is some fluctuation in the mean mesowear angle values in the different members of the formation and the average values range from 130o [(n= 12; Member E)] to 120.17 o

Discussion

[(n= 9; Member D)]. Species in Members

B, D and F respectively, indicated mixed C3/C4 diet. On the other hand, species in Members

C, G and L respectively, indicated that a more C4 dominated diet whereas, the species in Member E

o with the mean mesowear angle value of 130 indicated that slightly pure C4 diet. In conclusion as can be seen from the above result the average mesowear angle values for subspecies Elephas recki shungurensis shows a dietary adaptation that range from a mixed C3/C4 to a pure C4 diet through its evolutionary time period than the other four taxonomic groups of the lineage (Fig. 4.12 and 13).

The results of the mesowear angles in this study that are plotted as Box and Whisker plot in the previous chapter, are plotted here also to compare them side by side with other mesowear angle results of Elephas recki from the other paleontological sites in the region, as well as mesowear angle results from modern representatives (Fig 5.4A).

Figure 5.4 Mesowear angle results: (A) Linear regression of mean 813C values from tooth enamel and mean

mesowear angles in the molars sampled from proboscidean populations. The 95% confidence limits are shown

as dashed lines.( Taken from Saarinene, et al., 2015) ; (B) Box and Whisker mesowear angle values of Elephas

recki subspecies from the Shungura Formation that shows ll the subspecies have consistently C4 dominant

grazers.

Discussion

The comparison of the mean mesowear angle results in Elephas recki from Shungura support the results from the previous studies by Saarinen and his colleagues from other eastern

African sites (Saarinen et al., 2015). As the results of Saarinen and his group the extinct species of elephants from the Plio-Pleistocene of eastern Africa except Deinotherium bozasi all the species

(Elephas ekorensis, Elephas recki, Loxodonta exoptata, and Loxodonta adaurora) similarly to each other have registered significantly larger average mesowear angle than the living representatives of African and Asian elephants, which indicating grass dominating diet.

In conclusion all those modifications observed in this study (changes of molar morphologic and biometric characters) were derived by environmental pressure (Maglio, 1972,

1973; Coppens, 1978; Williams and Kay, 2001; Todd, 2006). The results from this study clearly show that diet and environmental changes play a great role in shaping the evolution of tooth molars morphology; crown height, average plate numbers (lamellar frequency), and also enamel thickness more over the wear pattern of the enamel crown

(mesowear angle) observed here could imply that the environment of the Shungura was under a continuous climatic and environmental influence and therefore, it was in a state of continuous change.

Discussion

Figure 5.5 Linear regressions (Ordinary Least Squares Regression) (A) between hypsodonty index values and mesowear angle and (B) [r = 0.06, p= 0.1and slope= 0.01] between enamel thickness and mesowear angle values for the molars (M2 and M3) sampled from Elephas recki lineage from Shungura populations. The 95% confidence limits are shown as blue colored solid lines.

As can be seen from the linear regression results there is no correlation between the hypsodonty index and the mesowear angle values and the linear regression result between the enamel thickness and the mesowear angle values also shows very weak correlation. The initial hypothesis on elephantid molar morphology was that a hypsodonty increase should be correlated with a decrease in enamel thickness, in relation with an increasing proportion of abrasive food in the diet, i.e., grass (Maglio, 1972). This is not the case in my results, where diet appears to be already and constantly dominated by grass between 3 Ma and 1 Ma. In this case we should observe conservation of the morphological features during this time period.

Instead, I observed some sudden changes in morphological features (in hypsodonty and in enamel thickness), and no progressive evolutionary trends. If this is the case, we should consider alternate hypotheses.

A first hypothesis is that of a delay between the acquisition of the observed diet and the morphological changes (Lister, 2013). One possibility could be that elephantids are

Discussion reproducing at a slow rate, requiring more time for natural selection to work. Yet, we see some relatively sudden changes in the elephant tooth morphology. Another possibility could be that the acquisition of higher-crown teeth with more abundant and thinner enamel bands required that other features change first, notably in the general structure of the cranium and mandible. For this, we need to observe changes in craniomandibular morphology, which is unfortunately poorly documented to date.

A second hypothesis is that other factors are involved in the observed morphological changes. This could be for example the case with grit increasing with the drying of eastern

African landscapes through the Plio-Pleistocene. This could explain for an increased abrasion of elephantid teeth even after they adopted a grazing diet. This could be checked in other groups than elephantids, to see if grit peaks could have had the same effect on all grazing taxa, as well as by observing the geology in order to reconstruct the evolution of grit/dust concentration.

Conclusion and Recommendations

CHAPTER SIX CONCLUSION AND RECOMMENDATIONS

6.1. Conclusion

The Shungura Formation is a Plio-Pleistocene paleontological site found in southern

Elephas recki, Loxodonta exoptata, and Loxodonta adaurora) which all went extinct during

Pleistocene.

The comparative description on International Omo Research Expedition (IORE) collection, OMO 3/0-74-959 maxillary associated right and left molars, OMO 3/0-74-572 mandibular associated left molar and the Omo Group Research Expedition (OGR) collection fragmentary mandibular associated molars; OMO 57/4-10010 recovered from the Shungura was compared with complete and nearly complete molar specimens of E. r brumpti and E. r. shungurensis.

Dental metric measurements were conducted from the original materials of Shungura and metric data were compared as illustrated in table 4.13. Whereas morphological observations were made both from the original and published materials from contemporaneous sites in eastern

Africa such as Koobi Fora, Shungura, Allia Bay and Middle Awash. The Morphological description and metric comparison of the dental materials from the Shungura, confirm that the relationships among the three taxa in eastern African sites changed at the same rate through their evolution, which is their evolution did not affected by the different basins.

Results from the biometric analysis indicate that, different subspecies in Elephas recki

Conclusion and Recommendations lineage show statistically significant evolutionary changes in terms of the biometric traits. The oldest subspecies (Elephas recki brumpti) in the lineage has provided remarkable significant changes in all biometric characters such as high hypsodonty index, relatively thicker enamel thickness and fairly low lamellar frequency than all of the younger subspecies (E .r shungurensis

, E. r. atavus, E. r. ileretensis and E. r. recki) in the lineage. However, the three intermediate subspecies (E. r. shungurensis, E. r. atavus, and E. r. ileretensis) did provide insignificant changes particularly in terms of biometric characters. Generally, the results show that there is no clear progressive increase in crown height (more hypsodont molars) Fig. 5.1B. Instead, I observed some sudden changes in morphological features (in hypsodonty and enamel thickness) Fig. 5.1B and 5.2B, and no progressive evolutionary trends in the basin throughout the Plio-Pleistocene in the Shungura fossil Elephas recki.

In addition to these particularly to infer the paleoenvironment only the paleodiet analysis could not be enough. Therefore, it would be important to discusses some other multiple approaches from the literature these includes, analysis of the faunal assemblage, study of the depositional environment, ecomorphological analysis, paleobotanical studies and recently, stable carbon and oxygen isotopes and isotopic paleosols studies. Despite the consensus on a general trend of decreasing in vegetation cover and the development of a drier environment, detailed reconstruction of the paleoenvironments and the paleolandscape across

Conclusion and Recommendations the different members of the formation, this would allow for a better understanding of the pattern of evolution of early mammals and a change in their environment.

6.2. Recommendations

♦ The number of samples taken for this study is relatively small and the differences

between values are not statistically significant in most cases. Hence, sampling and

analyzing more specimens from each Elephas recki lineage in every member, if

possible, will provide a better insight about their evolutionary trends.

♦ Due to the lack specimens of Elephas recki from Members K and H of the Shungura

Formation, to address the arguments raised and brought to statement of the problems

for this study, fossil Elephas of this time frame must be recover for the future to meet

and address the issue raised in the statement of the problem in this study.

♦ It is advisable to incorporate some cranial parts to have a better understanding about

their evolutionary trends through the specified time period. Studying the dental

element only results in partial information.

♦ Since different species within a group can have different dietary adaptations, sampling

and analyzing specimens that are identified to the lowest taxonomic level possible will

help in assigning the dietary adaptations to a specific group.

♦ If possible, studying the mesowear analysis of the whole proboscidean assemblage will

offer good information regarding the paleoenvironmental and paleoclimatic

conditions and will provide a better picture to a better understanding of the

paleolandscape of the region.

♦ Analyzing additional mesowear angle samples from other Miocene and Plio-

Pliestocene sites and compiling the results will provide a better understanding of

Conclusion and Recommendations

the dietary evolution of the different taxonomic groups.

♦♦♦ Combining different approaches of studying diet (such as, stable isotopes,

microwear) and integrating the results will also contribute to a better understanding

of the dietary adaptation of different taxonomic groups.

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100

Appendix Annex 1: Biometric Characteristics ofMb.& the five taxonomic groups of Elephas recki E. r. brumptiMolar type Sp.No unit P L W (l) H LF ET HI Mandibular 11 222.52 82.76 ?? 5 4.22 ?? 1 accociated M3 L 1- 33 B 11 7x 158.97 92.3 ?? 5 4.22 ?? 2 UM3 L 1-57 B 11 x5 120+ 75.5 ?? 4 4.3 ?? 3 LM3 L 2-3 B10 x5 89+ 5 3.9 80 ?? ?? 4 RLM3 L 2- 4 B10 x5 115.5+ 4.5 80 ?? ?? ?? 5 LM3 L 2-12 B10 x5x 98+ 5 66 ?? ?? ?? 6 LLM3 L 2-14 B10 X4 74+ 76 ?? 4.5 ?? ?? 7 RUM2 L 2-5 B10 x3x 59+ 72.5 ?? 4 ?? ?? 8 UM2 L 1-48 B11 x7 129+ 83 ?? 5 ?? ?? 9 LUM3 OMO20-3-1039 B0 90 5 11 220 ?? ?? ?? 10 LUM3 OMO20-3-3094 B0 X4 89+ 77 ?? 4.5 ?? ?? 11 LM3 OMO 28- 204 B10 x3x 66+ 72 ?? 4 ?? ?? 12 LM3 OMO 3/0 -213 B12 229 72 5 11 ?? ?? ?? 13 LLM3 OMO 3/0- 572 B12 x4 71+ 68.31 ?? 4.5 ?? ?? 14 RUM2 L 2- 11 B10 x5 94+ 58.47 83.24 4 3.35 142.36 15 RUM1 OMO 28 -190 B10 11 215 75 85 5 4.36 113.33

16 RUM3 OMO 3/0-959 B12

101

Appendix 213 76 85 5 4.15 111.84 Annex 1: Biometric Characteristics of the five taxonomic11 groups of Elephas recki 17E. r. LUM3brumpti OMO 3/0-959 B12 229 74 83 5 4.26 RLM3 OMO 3/0-960 B12 11 112.16

102

AppendixMolar I E. r. typshungurensise Sp. No Mb. & unit P L W (l) H LF ET HI

1 RUM3 OMO 54-463 D 2 11 190 74 93.47 5.5 3.44 126.31

2 RLM3 OMO 3- 2-920 C 4 13 194.5 66.5 86.14 6.5 3.47 129.53

3 LM3 OMO 18 - 1046 C 8 7x 117.96 66 104.7 6.5 2.9 159.63

4 UM3 OMO 10 A - 736 D 4 5 85.51+ 79 94 5.5 3.42 118.99

5 RUM3 OMO 58 - 134 E 5 10 215 92 117.44 5.5 3 127.65

6 UM2 OMO 40 - 171 C 5 7 137 64 ?? 5.5 3.41 ??

7 LM2 OMO 40 - 3029 C 5 10 170 77 90.43 7 3.4 117.44

8 RUM3 OMO 57/4- 2002 E 4 14 277 103 136.49 4 3.18 134.46

9 LM2 OMO 71 - 3030 E 1 6 129 79.5 77.86 6 2.7 97.94 MAN 10 M3 OMO 73 - 3179 E 1 9x 185+ 73 88.19 4.5 3 120.81 MAX 11 M3 OMO 148 - 7 D1 x10 191 84.5 108.11 6 2.91 127.2 MAX 12 M2 OMO 148 - 7 D 1 8 163 82.5 71.81+ 5.5 3.16 87+ LMAN 13 M2 OMO 160 - 2571 B C 5 10 182 68 84.68 6 3.2 124.52 MAN 14 M2 OMO 57 - 3203 E 3 10 207 69 80.6 5 3.66 116.81 RMAN 15 M2 OMO 160 - 2571 A C5 10 182 69 90.5 6 3.1 131.15

16 RUM3 L 114- 11 E4 x7 119 83.92 101.22 5.5 3 120.61

17 RLM3 L 348 - 1c D1 11 217.5 87.5 92.28 5.5 3.4 105.46

18 LUM3 L 170 - 2 D5 11 242 102 113.34 5.5 3.49 111.11

19 LUM3 L 22 - 1 D3 11 184.71 70.25 44+ 6 3.47 62+

20 LLM2 L 26 - 49 E2 10 183 66 94.72 6 2.6 143.52

21 LLM3 L 76 - 1 D4 x9 163.5 69 72.88 5 2.84 105.62

103

Appendix I 22 LUM2 L 19 - 2 D4 8 151 83 84 5.5 3.44 101.2 E. r. shungurensis 23 RUM3 OMO 57/5 - 367 E5 5 86.3+ 68 ?? 6 3.4 ??

24 LUM3 L 570 - 3 D5 7 131+ 82 ?? 4.5 ?? ??

25 LUM3 L 788 - 1b D1 x7x 120 85 ?? 5 ?? ??

26 RUM3 OMO 58 - 124 E 5 x6x 112+ 89.5 ?? 5.5 ?? ??

27 LM3 OMO 76 - 3028 F 1 8 138+ 47 ?? 6 ?? ??

28 LUM3 L 204 - 5 F1 12 216 89 ?? 5.5 ?? ??

29 LLM3 L 3- 7b F3 x7x 153+ 79 ?? 5 ?? ??

30 RLM2 L 396 - 3 F1 x6 130+ 79 ?? 5 ?? ??

31 RLM3 L 467-49 F1 x5 83+ 68 ?? 5.5 ?? ??

32 RLM3 L 465-60 F1 x6 100+ 54 ?? 6 ?? ??

33 LLM2 L 88- 14 E4 10 168 62 ?? 5.5 ?? ??

34 LUM2 L 186- 1a E1 10 179 80 ?? 6 ?? ??

35 RLM2 L 186-1b E1 x9 173.5 82 ?? 6 ?? ??

36 RUM3 L 267- 1 E1 x9 137+ 71 ?? 6 ?? ??

37 LLM3 L 26-45 E2 14 219 65 ?? 6 ?? ??

38 LLM3 L 26-47 A E2 x12 142+ 71 ?? 6.5 ?? ??

39 RLM3 L 26 - 47 B E2 x10 114+ 67 ?? 7 ?? ??

40 LLM2 L 10 - 2A E2 x7x 117 73.5 101 6.5 3.2 137.41

41 RUM2 L 874- 1 F3 x7 144 76 85.25 5.5 2.88 112.17

104

Appendix I E.r. atavus

Elements Sp. No. Mem&unit P L W(l) H LF ET HI RUM3 OMO 1E- 712 F - 3 x8 142+ 78 130.54 5.5 3.12 ?? 1 2 LLM3 L 74- 20 G 4 x13 249 ?? 139 4.5 3.65 ?? 3 LLM3 L 7 - 111 G 5 x5x ?? ?? 99.5 ?? 3.35 ?? 4 RLM3 OMO 75 s - 3003 G 1 x8 186+ ?? 122.85 5.5 ?? ?? 5 RLM3 OMO 75s - 839 G 1 x6 122+ ?? 106.53 5 ?? ?? 6 LLM3 L16-168 G 4 x6 ?? ?? 109.84 6 ?? ?? 7 LM3 L16-169 G 4 x7 125+ ?? 116.13 5.5 ?? ?? 8 RLM3 L 16-170 G4 X12 208+ ?? 111.84 6 ?? ?? 9 RUM2 L 776-1a G5 10 190 ?? 109.37 5.5 ?? ?? 10 LUM3 OMO 75-3052 G4 14 245 ?? 106.87 5 ?? ?? 11 LUM3 OMO 29-187 G1 11 193.75 ?? 116 5 ?? ?? 12 LLM3 OMO 75 S 2005 G1 11 250 ?? 100 4.5 ?? ?? 13 UM2 OMO 29/ 1-3054 G6 11 199 ?? 129.92 6 ?? ?? 14 LLM3 OMO 75 s- 1279 G1 11 195 ?? 99.96 5 ?? ?? 15 LLM2 OMO 27/3 - 940 A G27 10 160 ?? 111.85 5.5 ?? ?? 16 LLM3 OMO 6 - 398 G4 12 224 ?? 107.84 5.5 ?? ?? 17 RLM3 OMO 6- 399 G4 10 223 ?? 62.60+ 4.5 ?? 64.53+ 18 LLM3 OMO 6-400 G4 10 226 ?? 67.46+ 4.5 ?? 72.93+ 19 LLM2 OMO 29-1382 G1 10 187 69.5 100 5.5 ?? 143.88 20 LLM3 OMO 75- 3063 G4 12 176.32 70 95.97 6.5 ?? 137.1 21 LLM3 OMO 75- 3065 G4 14 224 77 85.53 6 3.27 111.1 22 RUM3 OMO 75- 3051 G 4 12 210 91 98 6.5 3.35 107.69 23 LLM3 OMO 75- 3196 G4 4x 73.6+ 77.6 115.48 ?? 3.44 148.43

24 RUM2 OMO 75- 826 G4 9 165 72 86.76 6 2.98 120.5

105

Appendix I E.r. atavus 25 LUM2 OMO 75- 826 G4 9 165 73 84.5 6 3 ?? 26 ULM3 OMO 72- 3150 F3 x6 90+ 68.94 72.65 ?? 3.65 ?? 27 URM3 OMO 72 - 3000 F3 x6 90+ 70.45 77.86 ?? 3.55 ?? 28 LUM2 OMO1C- 4523 F x6 103+ 69.18 114.22 5.5 ?? ?? 29 RUM3 OMO 100- 1932 G28 x6x 109.04 73 115.12 5.5 ?? ?? 30 RLM3 OMO 47-1737 G8 x6 121+ 79.5 104.73 5.5 ?? 131.74 31 RLM3 OMO 29- 3189 G7 11 224 82 81+ 5 ?? 98+ ?? 32 RLM3 OMO 310- 606 G8 12 21'9 61.5 83.73 5 136.14

106

Appendix I

E. r. ileretensis

Molar Mb. & type(Element) Sp. No unit P L W (l) H LF ET HI 1 RUM3 P 997-1b L 2 13 264 87 152.52 5 2.99 175.3 2 LLM1 F 225-3 L 4 x5 78.26+ ?? 119.04 6.5 3.24 ?? 3 LLM1 F 250- 1 L 4 x5 70.75+ ?? 101.27 ?? ?? ?? 4 LLM2 OMO 266 - 141a L or K x7 130.5+ ?? 103.34 6 ?? ?? ?? 5 RUM3 P994-2 J 6 x7 168+ 69 91.73 4.5 132.94

E. r recki

Mb. Molar type Sp. No Unit P L W (l) H LF ET HI 1 RUM3 OMO k/7- 3204 L 9 17 305 91 191.1 6 ?? ?? 2 LUM3 OMO k/7- 3205 L 9 18 322 91 ?? 6 ?? ?? 3 RUM3 OMOK/7- 3001 L9 x10 144+ 72 ?? 6.5 ?? ?? 4 LUM3 OMOK/7-3012 L9 x3 ?? 66.57 ?? ?? ?? ?? 5 RUM3 OMOK/7- 3014 L9 x3 ?? 69.26 ?? ?? ?? ?? 6 LLM3 OMOK/7- 3009 L9 13 230 69.23 ?? 6.5 ?? ?? 7 LUM3 OMOK/7- 111 L 11 185+ 78 ?? ?? 2.5 ?? ?? 8 RLM3 OMOK/7- 3013 L9 x4x 66+ 71 74+ ?? 2.75

107

Appendix Annex 2: Measured Mesowear angle of the five taxonomic group of SPElephas NO. recki lineage Mb&un Sub sp. Element MWA OMO 3.0-959 (r) B12 1 UM3 OMO 3.0-959 (l) B12 1 UM3 L 2 - 8 B10 1 UM2 L 2 - 10 B10 1 UM2 L2-6 B10 1 UM1 OMO 28- 476 B10 1 UM1 OMO 3/0 - 572 B12 1 Lm3 OMO 3/0 - 960 B12 1 Lm3 L 1 - 33 B11 1 Lm2 L348- 1c D1 2 UM3 L570 - 3 D5 2 UM3 OMO 57/4 - 2002 E4 2 UM3 L 204 - 5 F1 2 UM3 OMO 148 -7 D1 2 UM2 L 21 - 1 D1 2 UM2 L 19 - 2 D4 2 UM2 OMO 40 - 171 C5 2 UM2 L874-1 F3 2 UM2 OMO 151 - 184 E3 2 UM1 OMO 151 - 185 E3 2 UM1 OMO 71 - 3079 E1 2 UM1 OMO 3/2 - 920 C4 2 Lm3 OMO 40 - 3029 C5 2 Lm3 OMO 18 - 1046 D1 2 Lm3 L 22 - 1 D3 2 Lm3 L 76 - 1 D4 2 Lm3 OMO K/2 -3199 E 2 Lm3 L 26-45 E2 2 Lm3 OMO 40 - 3030 C5 2 Lm2 OMO 75 - 3066 G4 2 Lm2 OMO 160 - 2571A C5 2 Lm2 OMO 160 - 2571B C5 2 Lm2 L 26-49 E2 2 Lm2 OMO 71 - 3030 E1 2 Lm2 OMO 73 - 3179 E1 2 Lm2 OMO 57 - 3203 E3 2 Lm2 OMO 76 - 3049 F1 2 Lm1 L113 - 1 D5 2 Lm1 OMO 57/4 10010(r) E4 2 Lm1

OMO 57/4 10010(1) E4 2 Lm1

108

Appendix Annex 2: Measured Mesowear angle of the five taxonomic group of LElephas 74 - 20 recki lineage G4 3 UM3 OMO 75 - 3051 G4 3 UM3 OMO 72- 3150 G3 3 UM3 OMO 72- 3000 F3 3 UM3 OMO 75i - 1122 G3 3 UM2 OMO 75 - 826 r G4 3 UM2 OMO 75 - 826 l G4 3 UM2 OMO 29-1164 G1 3 UM2 OMO29- 3075 G1 3 UM2 L776- 1a G5 3 UM1 OMO 75 s - 2005 G1 3 Lm3 OMO 75 - 3065 G8 3 Lm3 L 7 - 112 G5 3 Lm3 L 74 - 23 G4 3 Lm3 L7 -109 G5 3 Lm3 OMO 6 - 399 G4 3 Lm3 OMO 75- 3052 G4 3 Lm3 OMO 6 - 400 G4 3 Lm3 OMO29- 187 G1 3 Lm3 OMO 75s- 1279 G1 3 Lm3 OMO6- 398 G4 3 Lm3 OMO29- 3189 G1 3 Lm3 OMO 75- 3196 G4 3 Lm2 OMO 29- 1382 G1 3 Lm2 OMO 75-sb- 562 G4 3 Lm2 OMO 47-2014 G8 3 Lm2 L577- 1b G12 3 Lm1 OMO75i- 2158 G3 3 Lm1 P 997 - 1 b L2 4 UM3 OMO 266-141a K 4 UM2 OMO266-140 K 4 UM1 F 8 - 6 L0 4 Lm2 OMO K/7 - 3204 L9 5 UM3 OMO K/7 - 3205 L9 5 UM3 OMOK/7 - 3001 L9 5 UM3

OMOK/7- 3013 L9 5 Lm3

119

Declaration I hereby declare that the thesis entitled “Evolution of Plio-Pleistocene Proboscidea from the Lower Omo Shungura Formation” is my original work and has not been presented for a degree in any other university, and that all sources of material used for the thesis have been duly acknowledged.

Name: Tomas Getachew

Signature: December, 2015 Addis Ababa.