Paleoecology of the Freshwater Ampullariidae from the Late Oligocene Nsungwe

Formation of Tanzania

A thesis presented to

the faculty of

the College of Arts and Sciences of Ohio University

In partial fulfillment

of the requirements for the degree

Master of Science

Yuwan Ranjeev Epa

April 2017

© 2017 Yuwan Ranjeev Epa. All Rights Reserved.

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This thesis titled

Paleoecology of the Freshwater Ampullariidae from the Late Oligocene Nsungwe

Formation of Tanzania

by

YUWAN RANJEEV EPA

has been approved for

the Department of Geological Sciences

and the College of Arts and Sciences by

Alycia L. Stigall

Professor of Geological Sciences

Robert Frank

Dean, College of Arts and Sciences 3

ABSTRACT

EPA, YUWAN RANJEEV, M.S., April 2017, Geological Sciences

Paleoecology of the Freshwater Ampullariidae from the Late Oligocene Nsungwe

Formation of Tanzania

Director of Thesis: Alycia L. Stigall

This study examines morphological diversification of the late Oligocene ampullariid species from the Rukwa Rift Basin of Tanzania. Six new species of ampullariids are described, including five species of Lanistes and one species of

Carnevalea. The high-spired Lanistes species described record the earliest appearance of this morphotype in the fossil record. Carnevalea santiapillai records the first appearance of this genus outside the Eocene of Oman. Paleoecological interpretations suggest a paludal to lacustrine ecology for C. santiapillai and a lacustrine ecology for L. nsungwensis. Lanistes songwensis and L. songweellipticus were interpreted as fluviate species whereas L. microovum and L. songweeovum were capable of inhabiting both lentic and lotic habitats. Morphological variations among paleoenvironments provide evidence for tectonically induced local radiation of Lanistes. Overall, this study provides valuable insight onto the taxonomy, evolution and the biogeographic affinities of the

Paleogene freshwater gastropods of Afro-Arabia, and thus contributes significantly to closing the “African Gap.”

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DEDICATION

I dedicate this thesis to my wife, Nilmani, and my family for their constant support,

encouragement and especially for always believing in me.

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ACKNOWLEDGMENTS

I would like to thank my advisor, Professor Alycia Stigall for her patience, guidance and constant encouragement. I would also like to thank my thesis committee:

Professor Nancy Stevens, Dr. Daniel Hembree, Dr. Gregory Springer and the late

Professor Elizabeth Gierlowski-Kordesch for their generous advice and guidance. My sincere gratitude to Dr. Jonathan Hendricks, Dr. Haley O’ Brien and Dr. Gregory Nadon for their kind and helpful suggestions. I thank Dr. Matthew Borths, Karie Whitman, Eric

Lund and all members of the Rukwa Rift Basin Project for providing me with an excellent collection of fossils for this thesis. I also thank The Academy of Natural

Sciences, Drexel University and The University of California Museum of Paleontology,

Berkeley, for providing comparative specimens for this project. I extend my appreciation to The Paleontological Society and the Ohio University Geological Sciences Alumni

Graduate Research Grant Committee for funding this research. Finally, I would like to thank all members of the Department of Geological Sciences, Ohio University and to the staff at the Department of Zoology, University of Peradeniya, Sri Lanka, for their encouragement, which helped me achieve my lifelong goal of becoming a Paleobiologist.

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TABLE OF CONTENTS

Page

Abstract ...... 3 Dedication ...... 4 Acknowledgments...... 5 List of Tables ...... 8 List of Figures ...... 10 Chapter 1: Introduction ...... 12 Objectives and the Scope of the Present Investigation ...... 12 Adaptive Radiations and the Fossil Record ...... 12 Chapter 2: Evolutionary History and Morphological Variation within the Family Ampullariidae ...... 16 Morphological Variation within the Family Ampullariidae ...... 16 Evolutionary History of the Ampullariidae ...... 17 Morphological Disparity within the Genus Lanistes ...... 19 Fossil Record of Lanistes and Carnevalea ...... 20 Chapter 3: Geologic Setting ...... 26 The Rukwa Rift Basin ...... 26 Sedimentology of the Nsungwe Formation ...... 29 Chapter 4: Materials and Methods ...... 33 Material Examined ...... 33 Morphological Data Collection...... 34 Data Analyses ...... 38 Interpreting the Paleoecology of Nsungwe Ampullariidae ...... 39 Chapter 5: Results of Morphometric Analyses ...... 40 Morphometric Analyses of Modern Lanistes Species ...... 40 Implications ...... 44 Morphometric Analyses of Nsungwe Ampullariids ...... 45 Implications ...... 50 Morphometric Analyses of Fossil Ampullariid Specimens ...... 50 Implications ...... 54 7

Combined Morphometric Analyses of Fossil and Modern Ampullariid Specimens ..... 54 Implications ...... 58 Taxonomic Composition of Nsungwe Ampullariids ...... 62 Chapter 6: Systematic Paleontology ...... 63 Chapter 7. Discussion ...... 103 New Ampullariid Fauna from the Late Oligocene Nsungwe Formation ...... 103 Paleoecology of Nsungwe Ampullariids ...... 104 Ecophenotypic Variation within the Nsungwe Ampullariids ...... 106 Paleoenvironment of the Late Oligocene Rukwa Rift Basin ...... 109 Evidence for Adaptive Radiation of Nsungwe Lanistes ...... 112 Closing the African Gap ...... 113 Chapter 8: Conclusions ...... 115 References ...... 119 Appendix A: All Nsungwe Fossils Examined ...... 135 Appendix B: Modern and Fossil Museum Specimens Examined ...... 142 Appendix C: Fossil Specimens Included in Morphometric Analyses ...... 146 Appendix D: Modern Specimens Included in Morphometric Analyses ...... 150 Appendix E: Fossil Specimens Loaned from Natural History Museums Included in Morphometric Analyses ...... 157

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LIST OF TABLES

Page

Table 1: Morphometric analysis of modern Lanistes species: Percent variation explained by principle components ...... 42

Table 2: Morphometric analysis of modern Lanistes species: Loadings for individual variables ...... 42

Table 3: Morphometric analysis of Nsungwe ampullariid species: Percent variation explained by principle components ...... 48

Table 4: Morphometric analysis of Nsungwe ampullariids species: Loadings for individual variables ...... 48

Table 5: Morphometric analysis of all fossil ampullariid species: Percent variation explained by principle components ...... 52

Table 6: Morphometric analysis of all fossil ampullariid species: Loadings for individual variables ...... 52

Table 7: Morphometric analysis of all modern and fossil ampullariid species: Percent variation explained by principle components ...... 57

Table 8: Morphometric analysis of all modern and fossil ampullariid species: Loadings for individual variables ...... 57

Table 9: Morphological characteristics of Carnevalea santiapillai ...... 68

Table 10: Morphological characteristics of Lanistes microovum ...... 74

Table 11: Morphological characteristics of Lanistes nsungwensis ...... 80

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Table 12: Morphological characteristics of Lanistes songweellipticus ...... 86

Table 13: Morphological characteristics of Lanistes songweeovum ...... 92

Table 14: Morphological characteristics of Lanistes songwensis ...... 99

Table 15: Paleoenvironmental distribution of Nsungwe ampullariid species ...... 105

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LIST OF FIGURES

Page

Figure 1: Geologic map of the Songwe Valley of the Rukwa Rift Basin…………….. 27

Figure 2: Stratigraphic profile of the Nsungwe Formation ...... 28

Figure 3: Counting whorls of Nsungwe ampullariids ...... 35

Figure 4: Linear shell measurements for modern and fossil ampullariids ...... 36

Figure 5: Alignment of fossil and modern ampullariids for photography and morphometric data acquisition ...... 37

Figure 6: Principle Component Analysis plot for modern Lanistes species ...... 41

Figure 7: Dendogram from Cluster Analysis for modern Lanistes species ...... 43

Figure 8: Principle Component Analysis plot for Nsungwe ampullariid species ...... 47

Figure 9: Dendogram from Cluster Analysis for Nsungwe ampullariid species ...... 49

Figure 10: Principle Component Analysis plot for all fossil ampullariid species ...... 51

Figure 11: Dendogram from Cluster Analysis for all fossil ampullariid species ...... 53

Figure 12: Principle Component Analysis plot for all modern and fossil ampullariid species ...... 56

Figure 13: Dendogram from Cluster Analysis for all modern and fossil ampullariid species ...... 61

Figure 14: New fossil ampullariids from the Nsungwe Formation: Carnevalea santiapillai ...... 64

Figure 15: Comparable material for Carnevalea santiapillai: Eocene specimens of

Carnevalea thaytinitiensis ...... 67 11

Figure 16: New fossil ampullariids from the Nsungwe Formation: Lanistes microovum...... 70

Figure 17: Modern Lanistes species of the high-spired Meladomus morphotype ...... 72

Figure 18: New fossil ampullariids from the Nsungwe Formation: Lanistes nsungwensis ...... 75

Figure 19: Comparable fossil species for Lanistes nsungwensis ...... 79

Figure 20: New fossil ampullariids from the Nsungwe Formation: Lanistes songweellipticus ...... 81

Figure 21: Comparable modern species for Lanistes songweellipticus ...... 85

Figure 22: Comparable fossil species for Lanistes songweellipticus...... 86

Figure 23: New fossil ampullariids from the Nsungwe Formation: Lanistes songweeovum ...... 87

Figure 24: Comparable fossil species for Lanistes songweeovum ...... 91

Figure 25: New fossil ampullariids from the Nsungwe Formation: Lanistes songwensis ...... 93

Figure 26: Comparable modern species for Lanistes songwensis ...... 98

Figure 27: Comparable fossil species for Lanistes songwensis ...... 99

Figure 28: Fossil Lanistes cf. songwensis preserved in a burrow ...... 111

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CHAPTER 1: INTRODUCTION

Local biotic radiations provide excellent opportunities to test a myriad of evolutionary hypotheses. Collectively, these events contribute immensely to our understanding of the generation of disparate morphologies, high species richness and the mechanisms involved in the rapid evolution of specific lineages. In this thesis, the evolutionary radiation of a new ampullariid fauna from the late Oligocene Nsungwe

Formation is examined. This unique fauna provides valuable insight on the radiation to novel ecosystems generated by rifting related changes in the landscape.

Objectives and the Scope of the Present Investigation

Present study examines the freshwater ampullariids in the context of three research questions: (1) What taxa comprise the late Oligocene Rukwa Rift Basin freshwater gastropod fauna? (2) Do faunal composition and shell morphology differ among paleoenvironments? (3) Are such differences correlated with rifting–related changes in landscape?

Adaptive Radiations and the Fossil Record

Although not all evolutionary diversifications are adaptive per se (see Simões et al. 2016), adaptive radiation is cited as one of the most important processes that contributes to biological, ecological and morphological diversity of the past and the present (Gavrilets and Losos, 2009; Muschick et al., 2014). This occurs when a single ancestral lineage diversifies into an array of species that accompanied by acquisition of disparate morphological and physiological characters and subsequently exploit different environments and resources (Schluter, 2000; Muschick et al., 2014). Numerous examples 13 of adaptive radiation and consequent proliferation of disparate taxa have been described.

Some of the best documented examples include the radiation of Darwin Finches from the

Galapagos, Anolis lizards from the Caribbean and Hawaiian silverswords (Schluter, 2000;

Gavrilets and Losos, 2009; Muschick et al., 2014). However, the radiation of cichlids of the African Great Lakes is perhaps the most spectacular of all, encompassing approximately 2000 species exhibiting diverse morphologies that have evolved within the last 10 million years (Kocher, 2004; Seehausen, 2006; Brawand et al., 2014).

Schluter (2000) describes three main processes in the ecological theory of adaptive radiation. The first process involves generation of phenotypic differentiation by divergent natural selection between different environments. In this process, each environment exerts unique selection pressures that result in differential phenotypic divergences among populations and species that occupy each environment. The second process produces phenotypic divergence through competition and ecological opportunity.

In this context, phenotypic differentiation occurs due to competitive interactions for limited shared resources. As individuals prospect for new resources and environments, taxa are subjected to differential selective pressures. Ecological opportunity as defined by

Schluter (2000) is the “wealth of evolutionarily accessible resources little used by competing taxa.” Thus, this second style of divergence encompasses diversification of a lineage via colonizing an uninhabited area, surviving a mass extinction event which eliminated the dominant predecessor and/or development of novel characters which exposes resources that was previously inaccessible. The third process, termed ecological 14 speciation, refers to the development of reproductive isolation among populations with the generation of ecological and phenotypic divergence.

Four empirical modes are available to explore adaptive radiation (Gavrilets and

Losos, 2009). These include: use of fossil data; phylogenetic comparative methods; microevolutionary studies of extant taxa; and manipulations of adaptive radiation in the laboratory (Gavrilets and Losos, 2009). It is often difficult to identify integral components of adaptive radiation in the fossil record (Lieberman, 2012; Neubauer et al.,

2013). Constraints include the incompleteness of the record, difficulties in deciphering the adaptive significance of morphological variations and a lack of ecological, behavioral and physiological data (Gavrilets and Losos, 2009; Neubauer et al., 2013). However, when compelling data are available, the fossil record can offer a powerful framework for analyzing adaptive radiation (Lieberman, 2012).

Several studies utilizing fossil data have explored morphological variations and its link with adaptive radiation in gastropods. Neubauer et al. (2013) used geometric morphometrics to analyze whether phenotypic evolution of the freshwater gastropod

Melanopsis from the ancient Lake Pannon was a product of adaptive radiation. Neubauer et al. (2013) were able to document all three biological processes described by Schluter

(2000) and to confirm the adaptive nature of the divergence. Van Damme and Pickford

(1995), working on the Miocene gastropods of the Albertine Rift, demonstrated a dramatic radiation of Lanistes. In that case, ecological opportunity to diversify was generated by tectonic induced habitat heterogeneity, predation and the extinction of a previously dominant taxon (Van Damme and Pickford, 1995). Notably, Lanistes senuti 15 exhibited development of thalassinoid characters (i.e., marine like forms with prominent shell ornamentations, see Van Damme and Pickford, 2003), which suggests that there is an inherent capacity within the genus Lanistes to develop such morphotypes when faced by predation pressure.

Several lines of paleontological and neontological evidences support the ability of

Lanistes to undergo adaptive radiation under novel ecological opportunities. Berthold

(1991a, b) suggested that the origin of the endemic ampullariids of Malawi was a result of interlacustrine adaptive radiation in response to predation, wave action and food resources. The ecological and behavioral segregation of Malawian Lanistes possibly led to accumulation of genetic variation and hence is the precursor for ecological speciation

(see Schluter, 2000; Hayes et al., 2009a). Hayes et al. (2009a) mentions a second radiation within the fluviate Congo River basin associated with L. bicarinatus, L. congicus, L. intortus and L. nsendweensis. Additionally, fossil data also support the premise of adaptive radiation in Lanistes (see Van Damme and Pickford, 1995).

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CHAPTER 2: EVOLUTIONARY HISTORY AND MORPHOLOGICAL VARIATION

WITHIN THE FAMILY AMPULLARIIDAE

Morphological Variation within the Family Ampullariidae

The gastropod fossils analyzed in this thesis belong to the family Ampullariidae.

Species of the freshwater operculate family Ampullariidae are commonly referred to as apple snails. Members of the family have a constrained overall shell morphology (Hayes et al., 2009a, b) with a majority characterized by large globose shells (Hayes et al.,

2015). However, significant inter- and intra-generic variations occur. For example, the extant genus Marisa Gray, 1824 and the extinct genus Carnevalea Harzhauser et al.2016, both have discoid morphologies. Additionally, the extinct Pseudoceratodus Wenz 1928, which is tentatively placed within the Ampullariidae (Hayes et al., 2015), has a more planorbid morphology; whereas, Sudanistes Harzhauser et al., 2017, has concave to weakly conical spires (see Harzhauser et al., 2017). Further, all ampullariid genera are dextrally coiled apart from Lanistes, Carnevalea and Pseudoceratodus, which exhibit sinistral shells. Also, species of the genus Lanistes exhibit a wide range of morphologies ranging from wide depressed shells to conical and elongate shells, thus further adding to the morphological disparity of the family.

In addition to these intergeneric and interspecific variations, extensive intraspecific disparity attributable to sexual dimorphism, ontogeny and ecophenotypic plasticity has been documented (see Hayes et al., 2009 a,b; Hayes et al., 2015). Tamburi and Martín (2012) described morphological variations between males and females of

Pomacea canaliculata in which shells of females are more globose with broader body 17 whorls compared to shells of males. Furthermore, Estebenet and Martín (2003) demonstrated the presence of heritable and ecophenotypic shell variations among three different populations of Pomacea canaliculata from southwestern Buenos Aires,

Argentina through field and lab studies. Ontogenic changes also affect the morphology of apple snails (see Hayes et al., 2015; Hayes et al., 2009b). For example, Estebenet (1998) demonstrated the presence of allometric growth in Pomacea canaliculata from Paseo del

Bosque pond, La Plata city. Although such variations confound ampullariid systematics, they also have the potential to provide valuable information that can be used in ecological and paleoecological interpretations.

Evolutionary History of the Ampullariidae

The Ampullariidae are currently distributed across humid tropical and sub- tropical habitats of Africa, Asia and South and Central America with highest diversity in

South America (Hayes et al., 2009a, b; Cowie et al., 2015). Currently, nine extant genera are recognized as valid. These include the New World Asolene d’Orbigny 1838,

Felipponea Dall 1919, Marisa Gray 1824, Pomacea Perry 1810 and the Old World

Afropomus Pilsbry and Bequaert 1927, Lanistes Montfort 1810, Saulea Gray 1868, Pila

Röding 1798, and Forbesopomus Bequaert and Clench, 1937 (Cowie et al., 2015). In addition, there are three extinct genera: Carnevalea Harzhauser et al. 2017 from the

Eocene of Oman, Sudanistes Harzhauser et al. 2017 from the Paleogene of Sudan and

Pseudoceratodes Wenz 1928 from the Oligocene of Egypt (see Harzhauser et al. 2016;

2017). 18

Numerous phylogenetic and morphological analyses have been performed to constrain relationships between and amongst the ampullariid taxa (see Hayes et al., 2015;

Hayes et al., 2009b). The most recent analysis performed by Hayes et al. (2009b) indicates that both Old World and New World ampullariids are reciprocally monophyletic with Lanistes and Pila robustly supported as reciprocally monophyletic sister groups. Resolving the ampullariid phylogeny permits testing for the origin and dispersion of these taxa. Recent phylogenetic consensus corroborates a Gondwanan, specifically African origin for the Ampullariidae as the most basal genera Afropomus and

Saulea are found today in Sierra Leone and Liberia and the remaining two Old World genera Lanistes and Pila are also found in Africa (see Hayes et al., 2015). Because Pila includes both African and Asian species, this poses an interesting question of whether this genus dispersed from Africa to Asia via rafting on the Indo-Madagascar land mass

(out of India hypothesis) or whether they followed a North African and Middle Eastern route (Hayes et al., 2009b; Hayes et al., 2015). Conversely, the discovery of a 160 Ma old ampullariid operculum from China may suggest an Asian origin for Pila followed by subsequent dispersal to Africa (Hayes et al., 2015). The diversification of New World ampullariids are thought to have initiated earlier than 90 Ma in Central and South

America subsequent to the splitting of Africa and South America (Hayes et al., 2009b).

Melchor et al. (2002) estimated the initial occurrence of Neotropical ampullariids to about 50 million years ago based on fossils of Pomacea from the early Eocene Gran

Salitral Formation. 19

Morphological Disparity within the Genus Lanistes

Species of the extant genus Lanistes are set apart from other ampullariids by their hyperstrophic sinistral shells. Fossils of this Old World taxon have been documented since the Eocene with the oldest record being that of L. grabhami from Hudi Chert

Formation of Sudan (see below). Presently, 43 nominally valid species are known (see

Cowie et al., 2015) and are distributed across Africa and Madagascar (Brown, 1994).

Lanistes occupy both lentic and lotic systems and is found inhabiting a diverse range of niches from lake margins to submerged habitats with water depths of 35 m in the case of

Lanistes nyassanus and up to 90 m in Lanistes nasutus (Berthold, 1990a,b). A wide range of disparate morphologies accompany their diverse habitats.

Traditionally, three subgenera of Lanistes were recognized based on conchological characters: Lanistes sensu stricto, Lanistes (Meladomus) and Lanistes

(Leroya) (Thiele, 1992; Brown 1994). Although Cowie et al. (2015) indicated that these subgenera do not form monophyletic groups and should no longer be used as formal taxonomic units, they remain useful as morphotype descriptors as they provide a framework for categorizing taxa based on diagnostic conchological characters.

 Lanistes sensu stricto morphotype: shells are characterized by having broad whorls

with a depressed to ovate profile. Shells typically have a large umbilicus, prominent

whorl angulations and may contain carinations.

 Meladomus morphotype: shells are characterized by having a high spire with no

whorl angulations or carinations. Umbilicus typically narrow or closed. 20

 Leroya morphotype: shells are smaller in size than the other morphotypes and are

typified by having thick shells with a closed umbilicus (see Thiele, 1992; Brown

1994).

Further, within distinct species, considerable morphological variations attributable to ecophenotypic plasticity are also present and have great potential in paleoecological studies.

Fossil Record of Lanistes and Carnevalea

There are approximately 4000 species of extant freshwater gastropods described occurring on all major continents (excluding Antarctica) and inhabit a wide range of habitats (Strong et al., 2008). Although diverse and widespread, the fossil record of freshwater gastropods remains poor compared with their marine counterparts (Strong et al., 2008). Because freshwater environments are lower in calcium than marine settings, a majority of freshwater gastropod shells are thin and have poor fossilization potential (see

Strong et al., 2008). This is further exacerbated by dissolution of shells in acidic environments like marshes where gastropod fauna tend to be abundant (Strong et al.,

2008; Neubert and Van Damme, 2012). Additionally, fossil preservation tends to be biased towards lowlands and lake deposits, thus underrepresenting a significant portion of habitats occupied by freshwater gastropods (Strong et al., 2008).

Modern species of Lanistes are restricted to Africa and Madagascar, but fossils of this taxon are found on both Africa and Arabian Peninsula. The oldest fossils of Lanistes,

Lanistes grabhami is described from the Eocene of Sudan by Cox (1933) which was re- described by Gautier (1973) and revised by Harzhauser et al. (2017). Lanistes grabhami 21 represent the Lanistes sensu stricto morphotype (i.e., broad, depressed shells typically with large umbilicus, whorl angulations and carinae). Cox (1933) and Gautier (1973) differentiated this highly disparate species from Lanistes antiquus Blanckenhorn 1901 from the Lutetian of Egypt and the modern Lanistes carinatus by the slower rate of whorl widening (see also Harzhauser et al., 2016; 2017). Blanckenhorn (1901) described

Lanistes antiquus as having a weak medial angulation, deep umbilicus and a more angulated last whorl (also see Harzhauser et al., 2016). An extremely large internal cast, measuring 50 mm high and 85 mm wide, of Lanistes antiquus from Fayum province near

Qasr el Sagha, Egypt was described by Newton (1912). Lanistes bartonianus was described by Blanckenhorn (1901) from the younger fluvio-marine Bartonian beds of the

Fayum, Egypt. Lanistes bartonianus differs from L. antiquus by having a more rounded body whorl (see Harzhauser et al., 2016) and from Lanistes carinatus by having a higher last whorl and a less convex periphery (Cox, 1933). The Oligocene Lanistes irregularis from the Gebel Ahmar Formation, is more depressed and planorbid than L. subcarinatus

(=L. antiquus) (see Oppenheim, 1906). The lower Oligocene Lanistes sandbergeri from the Sandberger Hill, west of the great pyramids is even more depressed than Lanistes irregularis (see Oppenheim, 1906). Cox (1933) stated that this specimen was probably based on an immature and poorly preserved specimen whose early whorl resembles that of L. grabhami. Lanistes tricarinatus Neubert and Van Damme 2012, from the Eocene

(late Priabonian) Zalumah Formation of Oman is a large depressed form with distinct shell ornamentation that includes two sharp keels at the base and top of the periphery of the second whorl, a double keel on the top and a single keel at the base of the third whorl 22 and a faint central keel on the rounded fourth whorl (see Neubert and Van Damme 2012;

Harzhauser et al., 2016). However, in the material examined by Harzhauser et al. (2016) this diagnostic sculpture tended to be rarely preserved or developed thus Harzhauser et al.

(2016) suggest that the higher spire of L. tricarinatus is a diagnostic feature distinguishing it over L. antiquus. Abbass described four depressed forms of Lanistes: L. shantili from the Oligocene Wadi Fatima Formation of Saudi Arabia (Abbass, 1971),

Lanistes mahmoudi from the Helvetian-Tortonian (?) of the upper Hommath Member,

Ramlyia, Egypt (Abbass, 1977), Lanistes sodaensis from the upper Eocene Garet El Soda

Locality, Egypt (Abbass, 1967) and Lanistes abbassiensis from the Oligocene of Cairo,

Egypt (Abbass, 1962; see Harzhauser et al., 2017). Lanistes shantili differs from L. grabhami by having a lower shell and less elevated whorls (Abbass, 1971). Lanistes abbassiensis differs from the modern L. carinatus by having its shell apex at the same height as the adapical side of the body whorl (Abbas, 1962) and from L. grabhami by having evenly rounded and broader last whorl (Harzhauser et al., 2017). Abbass (1977) stated that Lanistes mahmoudi can be distinguished over the type species of Lanistes, by its lower spire, lower last whorl and wider umbilicus. However, in his description,

Abbass (1977) mentioned the presence of three spiral chords on the body whorl and secondary chords in between. The former divides the shell into four equal parts (Abbass,

1977). This ornamentation pattern should also be considered as distinguishing features as only Lanistes tricarinatus possess a similar trait. Lanistes sodaensis differs from the modern L. carinatus by having a proportionally lower spire (Abbass, 1967). 23

Fossils of the extant Lanistes solidus were described by Newton (1910) from the

Quaternary deposits from Chiwondo Beds of Malawi. Further, Connolly (1927) described a poorly preserved specimen of this species from Lake Nyasa that he considered to be either L. solidus or L. ovum (also see Adam, 1959). Gautier (1970) described Lanistes bishopi, a depressed Lanistes with a sunken spire from the Kazinga Site C of Lake

Edward, Uganda. Van Damme and Pickford (1995) described additional specimens of

Lanistes bishopi from Nkondo Formation, giving this species a time constraint of approximately between 6-4.5 Ma (see Van Damme and Pickford, 1995). Additionally,

Van Damme and Pickford (1995) described eight species of Lanistes representing the depressed morphotype from the Albertine Rift Valley of Uganda and Zaire. These include Lanistes heynderycxi from the Mohari Formation, Ongoliba Beds and Oluka

Formations (time span approximately 9 to 6.5 Ma); L. hadotoi from the Nkodo, lower part of the Warwire and upper Nyaburogo Formations (time span approximately 6 to 4.4

Ma); Lanistes asellus from the Nkodo and upper Nyaburogo Formations and Kazinga

(time span approximately 6 to 4.5 Ma); Lanistes senuti from the Nkodo Formation (time span approximately 6 to 4.5 Ma); Lanistes nkondoensis from the Nkodo and Nyaburogo

Formations (time span approximately 6 to 4.5 Ma); Lanistes gautieri from the Nkodo and upper Oluka Formations (time span approximately 6.5 to 6 Ma); Lanistes trochiformis from the Nkodo Formation (time span approximately 6 to 4.5 Ma) and

Lanistes gigas from the Nkodo Formations (time span approximately 6 to 4.5 Ma) (see

Van Damme and Pickford, 1995). 24

Lanistes carinatus is probably the best-represented fossil of the genus Lanistes with fossils of this species dating back to the Oligocene (Pickford et al., 2010).

Numerous occurrences of L. carinatus have been recorded. These include, late Miocene

El Ris Limestone, Western Desert, Egypt (Pickford et al., 2010); Middle Miocene

Nachola Formation (Pickford et al., 1987); Early Miocene Kalodirr locality, Northern

Kenya (Leakey and Leakey, 1986); Miocene (Burdigalian) Karungu Bay, Lake Victoria

(Newton, 1914); Miocene Muruarot Hill Locality, Turkana Distract, Kenya (Van Damme and Gautier, 1972); Miocene of Kenya (Verdcourt, 1963); late post-Pliocene Beds of

Egypt (Newton, 1912; 1914) and Pleistocene of Lake Albert and Semaliki (Adam, 1959)

(also see Van Damme, 1984 for additional occurrences from the late Pleistocene and the

Holocene). Van Damme and Pickford (1995) states that all Miocene and Pliocene fossils of Lanistes carinatus described from the Albertine Basin belong to other (endemic)

Lanistes species, thus, their records are not included here.

Several high-spired morphotypes have been previously described. Reck and

Dietrich (1923) described Lanistes recki, which they consider to be a sub recent fauna.

However, Connolly (1928) suggests a late Tertiary age for L. recki (see Adam, 1959).

According to Reck and Dietrich (1923), Lanistes recki resemble the modern Lanistes stuhlmanni but Adam (1959) suggested that it represents a form of L. ovum. Van Damme and Gautier (1997) described several Miocene and Pliocene fossils of Lanistes ovum from the Wembere-Manonga Formation of Tanzania. Van Damme and Pickford (1995) and

Van Damme and Gautier (1997), stated the presence of a Lanistes ovum like form from a lower middle Miocene Maboko Island in Lake Victoria. Apart from these, two additional 25 records of late Pleistocene and Holocene L. ovum is mentioned from Chad (see Van

Damme, 1984). Stidham (2004) stated the presence of Lanistes ellipticus from the Plio-

Pleistocene (3.75-1.8 Ma) Chiwondo beds of Malawi (see Kullmer, 2008 for the age of the deposit). Van Damme and Pickford (1995) described Lanistes olukaensis from the lower Oluka Formation (age range approximately 8-6.5 Ma) from the Albertine Rift.

Carnevalea a discoid ampullariid was initially included within the genus Lanistes and was described as Lanistes thaytinitiensis (see Neubert and Van Damme, 2012).

However, Harzhauser et al. (2016), considering its unique shape elevated it to a unique genus. Previous records for fossils of Carnevalea have been restricted to the late

Priabonian Paludal biomicritic limestones of the Zalumah Formation, of Thaytiniti,

Dhofar, Oman (Neubert and Van Damme, 2012; Harzhauser et al., 2016).

26

CHAPTER 3: GEOLOGIC SETTING

The Rukwa Rift Basin

The Rukwa Rift Basin (RRB) is part of the western branch of the East African Rift

System (Fig. 1). This northwest-trending half-graben contains sedimentary fill greater than eight kilometers in thickness (Roberts et al., 2012). Four tectonic phases of basin development and sedimentation of the Rukwa Rift Basin are described by Roberts et al.

(2012). The deposition of the basal Karoo Supergroup was initiated during the late

Paleozoic (Roberts et al., 2012). Isolated exposures of the Permo-Carboniferous Karoo

Supergroup strata occur in the RRB and are composed of a series of glacial, lacustrine, and fluvial deposits (Roberts et al., 2010). The Galula Formation is a middle Cretaceous

(Aptian–Cenomanian) unit composed of the Mtuka and Namba Members (Roberts et al.,

2010, 2012; Gorscak et al., 2014), which overlies the Karoo strata. The Galula Formation contains fossils of non-avian dinosaurs, mammal-like notosuchian crocodyliformes, and dinosaurs (O’Connor et al., 2010; Roberts et al., 2012; Gorscak et al., 2014). The Nsungwe

Formation occurs next and is overlain by the uppermost unit of the Rukwa Rift Basin, the

Pliocene to Recent Lake Beds sequence (Roberts et al., 2012).

27

Figure 1. Geologic map of the Songwe Valley in the southern end of the Rukwa Rift Basin, showing stratigraphy and age of fossil localities (modified from Roberts et al., 2010). Specimens examined in this thesis were collected from localities 1 (Nsungwe River Section) and 2 (Songwe River Section), marked with stars.

The Nsungwe Formation comprises two members: The lower Utengule Member and the upper Songwe Member (Fig. 2). The Utengule Member is characterized by a coarsening upward sequence from a basal white sandstone/conglomerate unit with well- rounded quartz pebbles to poorly sorted deep-red to orange sandstones to clast-supported conglomerates with metamorphic/vein quartz clasts and pedogenic calcium carbonate nodules (Roberts et al., 2010). In contrast, the finer grained Songwe Member transitions from a thin, green cross-bedded/ripple-laminated sandstone to fossiliferous red, orange, 28 and gray–green siltstones, mudstones, laminated claystones, lenticular sandstones, and devitrified bentonitic tuffs (Roberts et al., 2010).

Figure 2. Stratigraphic columns and magnetic stratigraphy through the Nsungwe Formation Type Section modified from Roberts et al. (2010, 2012) Abbreviations. GPTS. Global Polarity Time Scale, VGP lat. Virtual Geomagnetic Pole Latitude for Palaeomagnetic Samples. 29

Isotopic dating of volcanic tuffs, paleomagnetic investigations and biostratigraphy indicate that the Songwe Member is late Oligocene in age, providing age constraint for deposition between 26 and 24 million years (Stevens et al., 2009; 2013 Roberts et al., 2010;

2012; 2016; McCartney et al., 2014; Stevens et al., 2016).

Sedimentology of the Nsungwe Formation

Roberts et al. (2010) analyzed the sedimentology of the Galula and Nsungwe

Formations based on internal and external geometry and bounding surfaces, architectural element analysis, and fossils. Based on these criteria, Roberts et al. (2010) recognized five facies associations (FA) between the two formations. Four of these facies associations occur within Nsungwe Formation: major conglomerate facies association (FA1), major tabular to lenticular sandstone facies association (FA3), minor tabular to lenticular mudstone/muddy sandstone facies association (FA4), and laminated siltstone and claystone facies association (FA5).

Roberts et al. (2010) defined the major conglomerate facies association (FA1) as thick, laterally persistent, matrix-clast-supported conglomeratic units, the majority of which were sourced from outside the depositional basin. Units are composed of multiple thin beds that are stacked and dominated by either clast-supported extraformational conglomerate or matrix supported conglomerate (Roberts et al., 2010). FA1 is interpreted as a major braided fluvial pediment surface or as proximal–medial debris flow dominated alluvial fans. FA1 occurs most commonly in the lower Utengule Member, and uncommonly in the Songwe Member (Roberts et al., 2010). 30

In contrast, the major tabular and lenticular sandstone facies association (FA3) is found only in the Songwe Member and consists of 2–10 m thick isolated lenticular sandstone bodies with trough cross-bedded sandstone, planar cross-bedded sandstone, horizontally stratified sandstone, massive sandstone, crudely stratified sandstone, clast- supported intraformational conglomerate, clast-supported intraformational conglomerate and clast-supported extraformational conglomerate (Roberts et al., 2010). Sandstones are composed primarily of medium to coarse-grained textures with abundant clay and silt matrix and minor calcite cement with fining upward sequences (Roberts et al., 2010).

Fossil content is dominated by microvertebrates (fishes, frogs, turtles, crocodiles and mammals) and invertebrates (gastropods, bivalves and crabs) and also root traces

(Feldmann et al., 2007; Stevens et al., 2008; Roberts et al., 2010). This facies association is interpreted as a fluvial channel deposit.

The minor tabular to lenticular mudstones/muddy sandstones facies association

(FA 4) is highly variable in composition within the Songwe Member (Roberts et al., 2010).

Beds generally range from 10-70 cm in thickness and consist of extensive, tabular units and spatially restricted lenticular beds. Beds in the Songwe Member vary from tabular units with massive sandstone, horizontally stratified sandstone, and ripple cross laminated sandstone that fine upward to massive fine-grained beds, finely laminated or rooted siltstone and claystone layers and variants of these two end members (Roberts et al., 2010).

Bioturbation was observed throughout the association; root traces and indistinct burrows are the most common trace fossils (Roberts et al., 2010). Additionally, the authors observed meniscate backfilled burrows and a termite nest trace (Termitichnus) (Roberts et al., 2010; 31

2016). Compared to trace fossils, body fossils are rare and are dominated by dense accumulations of gastropods and few microvertebrate bone and teeth. This facies association was interpreted to represent portions of abandoned channels and overbank depositional environments (Roberts et al., 2010). Tabular lithofacies containing massive sandstone, horizontally stratified sandstone, and ripple cross-laminated sandstone are interpreted as crevasse splay deposits; whereas units having fine-grained facies were inferred to represent ephemeral floodplain ponds and paleosols (Roberts et al., 2010).

Additionally the inter-bedding of coarse and finer units was interpreted as cyclic overbank flooding, ponding, drying, and peadogenesis (Roberts et al., 2010).

Like FA3 and FA4, the laminated siltstone and claystone facies association (FA5) is restricted to the Songwe Member (Roberts et al., 2010). This facies association represents approximately 30-35% of the stratotype section and consists of maroon, red, orange, gray, and white beds of finely laminated siltstone and claystone and bentonitic and tuffaceous claystone (Roberts et al., 2010). A typical FA5 association includes an interbedded sequence of mottled, bioturbated, sandy siltstones, laminated mudstones (Fl) and thin ultrapure claystone beds (Fb) (Roberts et al., 2010). Fossil preservation tends to be poorer than other FA, but gastropods and crab element are found in large local aggregations within siltstones (Roberts et al., 2010). Microvertebrates including isolated fish, frog, turtle and mammalian elements also occur (Stevens et al., 2008; Roberts et al.,

2010). The distinguishing sedimentological feature in this facies association is the presence of ultrapure claystone beds of bentonitic and tuffaceous claystone which range from 5- 250 cm in thickness (Roberts et al., 2010). FA5 is interpreted as a subaqueous deposition in 32 floodbasin lakes and wetlands, which consist of numerous ecosystems including low- energy central lake, delta-marsh and a marginal sandy delta and shoreline regions. The genesis of FA5 has been linked to rifting related volcanism, which is corroborated by several lines of sedimentary evidence (Roberts et al., 2010, 2012). The presence of pure laminated to brecciated claystones and calcite pebble breccias are interpreted as airfall ash and airflow tuffs and the presence and elevated concentrations of euhedral phenocrysts of phlogopite, pyrochlore, magnetite, andradite, titanite, apatite, calcite tephra clasts, relic glassy textures and elevated trace element concentrations such as niobium link FA5 to a volcanic origin (Roberts et al., 2010). Notably, the unique mineral assemblage and increased levels of niobium and other trace elements suggest an alkaline volcanic source, inferred to be a carbonatite volcano (Roberts et al., 2010). The input of carbonates into this system has important biological and taphonomical implications, as discussed later.

33

CHAPTER 4: MATERIALS AND METHODS

Material Examined

This study incorporates 175 specimens of fossil gastropods collected from the

Songwe Member of the Nsungwe Formation from the Rukwa Rift Basin, Tanzania

(Appendix A). The Rukwa Rift Basin Project (RRBP) participants collected the fossil material from eight different localities over a period of 15 field seasons since 2002

(indicated in Fig. 2). These include fossils from fluvial deposits of TZ01, TZ01 south, and TZP-2, fossils from Nsungwe 2, Nsungwe Gastropod Location, Bigwall (Nsungwe

2B) and Nsungwe 3 which are interpreted as lacustrine deposits and Nsungwe 1 which represents a lacustrine to fluvio-deltaic deposit (McCartney et al., 2014; Roberts et al.,

2010). Specimens are housed at Ohio University.

Nsungwe fossils were compared with species described in the literature and with modern and fossil specimens loaned from other natural history museums (Appendix B).

The modern Lanistes species comparison set loaned from the Academy of Natural

Sciences, Philadelphia (ANSP) included 75 specimens of 17 species and subspecies native to Africa and Madagascar: Lanistes ovum Troschel 1845; Lanistes ovum adansoni

Kobelt 1911; L. ovum elongata Troschel 1845; L. ellipticus Martens 1866; L. grasseti

Morlet 1863; L. purpureus Jonas 1839; L. carinatus Olivier 1804; L. intortus Lamarck

1816; L. bicarinatus Germain 1907; L. congicus O. Boettger 1891; L. nsendweensis

Dupuis and Putzeys 1901; L. neavei Melvill and Standen 1907; L. varicus Müller 1774;

L. libycus Morelet 1848; L. solidus Smith 1878; Lanistes sinistrosus Pea 1838 and L. graueri Thiele 1911. Seven fossil specimens examined were loaned from The University 34 of California Museum of Paleontology (UCMP) and included L. carinatus Olivier1804 from the Miocene Muruarot Hill, Turkana, Kenya and L. ellipticus Martens 1866 from the Plio-Pleistocene Chiwondo beds of Malawi.

Morphological Data Collection

Qualitative terms for shell sizes (small, medium and large), overall shell shape, aperture shape and shell ornamentation terminology follow Burch (1989). Whorls were counted following a modified version of Janssen’s (2007) method (Fig. 3). Whorl counts are complicated by erosion of apical whorls, apical deformation and moldic preservation.

Thus, whorl numbers are expressed as an approximate in a majority of shells, which is indicated adjacent to the value in data tables.

Following Salvador and De Simone (2013), four linear shell measurements were obtained. These measurements are: Total shell height (H); Total shell width (D), Aperture height (h) and Spire height (S) (Fig. 4). Total shell height is defined as the maximum vertical distance from the base of the lip to the highest adapical point of the preserved apex. Total shell width is defined as the maximum horizontal distance from the widest point of the outer lip of the aperture to widest point of the body whorl. Aperture height is defined as the vertical distance from the base of the apertural lip to the highest adapical point of the aperture lip. Spire height is defined as the vertical distance from the highest adapical point of the aperture lip to the highest adapical point of the preserved apex.

35

Figure 3. Counting whorls (modified from Janssen, 2007). A horizontal line is drawn to separate the first semicircular part of the initial whorl. In this example of Lanistes songwensis (RRBP 5492B), the start of whorl 1 is indicated by the blue arrow and the whorl is completed when it meets the horizontal separator line. Whorl 2 begins at the green arrow and completes at the horizontal line. The third whorl begins at the pink arrow, but is incomplete. The value for the last incomplete whorl is calculated by measuring the angle (ϴ) between the horizontal line and the line that connects the adapical most preserved part of the last whorl (red line). This angle is then divided by 3600 and expressed as a single decimal point. Thus, this exemplar is counted as 2.3 whorls (scale bar 10 mm). 36

Figure 4. Example linear measurements for morphometric analysis following Salvador and De Simone (2013) on Lanistes songwensis (RRBP 9265B). Total shell height (H); Total shell width (D), Aperture height (h) and Spire height (S) (scale bar 10 mm)

Of the fossil material examined, 36 of the best-preserved specimens were used for detailed morphometric analysis (Appendix C). Each of these specimens had a minimum total shell height of 10 mm, included at least two complete whorls, had been subjected to minimal taphonomic deformation, and preserves conchological features permitting accurate identification. Morphometric measurements were also obtained for 75 comparative specimens (Appendix D) and seven fossil specimens loaned from natural history museums (Appendix E).

All measurements were obtained digitally using the software ImageJ version 1.50i

(Rasband, 2016). To provide consistent measurements, shells were photographed in apertural view using a Nikon D2x digital camera with a Nikon AF Micro-NIKKOR 37

60mm f/2.8D Lens. Fossil and modern shells were aligned such that a vertical line extending from the apex connects with the columellar margin of the shell (Fig. 5).

However, shell shapes may vary as a result of ontogeny, ecophenotypic plasticity and taphonomy, hence the line does not always form a perfect connection. In such instances, shells were aligned such that the best possible connection is obtained. Uniform distances between the lens and the specimen were maintained at all times. For fossils, a distance of

38 ± 1 cm was maintained whereas for modern shells, images were obtained at a distance of 43 ± 1 cm.

Figure 5. Shell alignment in apertural view of Lanistes songwensis (RRBP 9265B). Note that the apex and columnar lip does not form a perfect connection. (Scale bar 10 mm). 38

Data Analyses

To visualize fields of morphospace occupied by modern Lanistes species, a

Principle component Analysis (PCA) was performed on log-transformed measurements of modern taxa using PAST (PAleontological STatistics software package version 3.14)

(Hammer et al., 2001). The analysis of 71 specimens of 17 modern Lanistes species and two subspecies (see Appendix D) was used as a control to test whether taxon/morphotype specific regions can be identified using standardized linear data on shells whose taxonomic identities are known. A second PCA was performed on log-transformed linear measurements of Nsungwe fossils to recognize morphospace occupied by the late

Oligocene taxa. To compare morphospace distribution between Nsungwe specimens and other Cenozoic species, a third PCA was performed on log-transformed linear data of

Nsungwe specimens and Lanistes carinatus Olivier 1804 from the Miocene Muruarot

Hill, Turkana, Kenya and L. ellipticus Martens 1866 from the Plio-Pleistocene Chiwando beds, Malawi. A fourth PCA was performed on log-transformed linear measurements of all fossil and modern samples to interpret how morphospace fields compare among modern and fossil taxa.

In order to recover morphological groupings based on morphometric data, log- transformed linear measurement data were subjected to a non-constrained hierarchical cluster analysis using PAST 3.14 (Hammer et al., 2001). Clusters were produced using the Ward’s Method algorithm and Euclidean similarity index. Bootstrap resampling of columns was performed 10,000 times. Cluster analyses were performed for (1) modern specimens, (2) Nsungwe gastropod specimens, (3) Nsungwe and other fossil specimens 39 and (4) all fossil and modern specimens combined. The analysis of modern Lanistes specimens was used as a control to test whether groupings can be identified using standardized linear data on shells whose taxonomic identities are known.

Interpreting the Paleoecology of Nsungwe Ampullariidae

Paleoecology of the Nsungwe gastropod species was interpreted based on ecological data published for extant related taxa that share similar morphologies (ex.,

Pilsbry and Bequaert, 1927; Louda and McKaye, 1982; Louda et al., 1984; Berthold,

1990a,b; Brown, 1994). The presence of ecophenotypic plasticity was investigated by analyzing shell variations observed in modern Lanistes and variations recoded by non- ampullariid gastropods. Furthermore, sedimentological data for the Songwe Member of the

Nsungwe Formation published by Roberts et al. (2010; 2012) were also incorporated to inform paleoecological inferences.

40

CHAPTER 5: RESULTS OF MORPHOMETRIC ANALYSES

Morphometric Analyses of Modern Lanistes Species

Principle Component Analysis (PCA) demonstrated clear separation among specimens consistent with species assignments (Fig. 6). The first two principle components (PC1 and PC2) generated using log-transformed linear measurements of modern specimens, described 99.2% of total variation with PC1 describing 90.2% and

PC2 representing 9.0% (Table 1). PC1 was strongly positively influenced by spire height

(S) and PC2 was strongly positively influenced by total shell width (D) (Table 2). Taxa analyzed show a clear separation between high-spired morphotypes (L. ovum, L. ellipticus, L. purpureus, L. ovum elongata and L. grasseti), which group on the right side of the plot, and the depressed forms (L. nsendweensis, L. neavei, L. graueri, L. congicus and L. carinatus), which plot on the left (Fig. 6). There is an overlap between the high- spired and depressed forms where Lanistes ovum adansoni overlaps with the morphospace cluster formed by L. nsendweensis. Further, L. bicarinatus, L. solidus, L. libycus, L. intortus and L. varicus plot to the right side of axis 1 in proximity with L. ellipticus. There is also considerable overlap with L. nsendweensis, L. neavei, L. graueri,

L. congicus and L. sinistrosus. The wide shelled, low spired L. carinatus group towards the top of the plot.

41

Figure 6. Principle Component Analysis (PCA) of 71 specimens of 17 modern Lanistes species. Polygons indicate the morphospace boundary for individual species. Green lines indicates the biplot of the PCA which represent projections of the original axes. 42

Table 1.

Morphometric analysis of modern Lanistes species: Percent variation explained by principle components (PC) PC Eigenvalue Variance

1 0.1298 90.20%

2 0.0130 9.03%

3 0.0011 0.74%

4 <0.0001 0.03%

Table 2.

Morphometric analysis of modern Lanistes species: Loadings for individual variables (Abbreviations. H. Total shell height; D. Total shell width; h. Aperture height and S. Spire height) PC 1 PC 2 PC 3 PC 4

H 0.5002 0.0728 0.3598 -0.7842

D 0.3632 0.6568 -0.6608 -0.0105

h 0.4111 0.3833 0.5976 0.5720

S 0.6699 -0.6455 -0.2771 0.2403

The dendogram generated by the cluster analysis performed on these 71 specimens includes two main clusters (Fig. 7). Cluster 1 which is supported by 65% in bootstrap iterations contain a majority of the high-spired morphotypes excluding L. grasseti, L. ovum adansoni and a single poorly preserved L. ovum specimen. Cluster 2 supported by 31% of bootstrap iterations, is dominated by depressed morphotypes (Fig. 43

7). Specimens assigned to the same species mostly group together, although specimens attributed to L. graueri and L. nsendweensis shows considerable scattering within Cluster

2.

Figure 7. Dendrogram produced from analysis of 71 specimens of 17 modern Lanistes species. Numbers at nodes indicate percentages supported by 10000 bootstrap iterations. 44

Implications

Principle Component Analyses provides a clear visualization of morphospace utilization of modern Lanistes. Overall, the high-spired morphotypes plot to the right side of PC1 axis. However, several taxa including L. bicarinatus, L. solidus, L. varicus, L. libycus and L. intortus occur close to high-spired morphotypes. These taxa, although sharing dimensional traits, can be clearly differentiated by conchological characters like carination and whorl angulation, which are not coded with linear measures and thus do not contribute to the PCA analyses. Similarly, the overlap among L. nsendweensis L. neavei,

L. congicus, L. graueri and L. sinistrosus can be resolved using shell characters that are not represented in dimensional measurements. The morphospace occupied by Lanistes ovum adansoni overlaps with that of L. nsendweensis. It should be noted that all analyzed specimens of Lanistes ovum adansoni have considerable portions of their spires missing, thus spire measures does not represent the true spire height. Therefore poor preservation, even in modern shells may result in spurious placement in PCA plots. Hence, it is important to consider both morphological and morphometric criteria when making interpretations. It is evident that this analysis provides a justification that within the genus Lanistes, PCA is an effective tool for discerning both morphospace occupancy as well as hypothesizing group membership of an unknown taxon; however, morphological attributes should also incorporated with the latter.

The presence of distinct high-spired and depressed groups is further corroborated by the cluster analysis. However, Lanistes ovum adansoni and L. grasseti, both of which belong to the high-spired morphotype, cluster with depressed forms. The clustering of the 45 former can be attributed to the poor preservation of its spire. However, the position of L. grasseti reiterates the importance of using both morphological and morphometric attributes prior to interpretation. Considerable morphological variation is observed in the analyzed specimens of L. nsendweensis, which probably gave rise to the scattering within the clusters and the broad morphospace occupancy in the PCA. Overall, within the genus Lanistes, cluster analysis proves to be effective in distinguishing morphotypes at a broader scale, however it is essential to have morphological attributes considered in the final interpretation.

Morphometric Analyses of Nsungwe Ampullariids

Principle Component Analysis (PCA) results of fossil ampullariids from Rukwa

Rift Basin shows clear separation of five morphotypes (Fig. 8). These are labeled as six species on Figure 8 because additional shell characters support the separtion of two species within the central morphospace polygon (discussed more fully below). The first two principle components describes 98.5% of total variance with PC1 representing 88.2% and PC2 accounting for 10.3% (Table 3). PC1 was strongly positively correlated with spire height; whereas PC2 was strongly positively correlated with total shell width (Table

4). These loadings and parameters attributions are similar to those observed for modern

Lanistes species (Tables 2 and 3).

Like the PCA of modern Lanistes, high-spired taxa occur to the right and depressed species to the left along Axis 1. Both L. songweeovum and L. songweellipticus which possess high spires are found to the bottom right of the plot. Carnevalea santiapillai with its very low spire, tall aperture and wide shell is found towards the upper 46 left of the PCA (Fig. 8). Lanistes songwensis is characterized by high variability and plots towards the center of morphospace with L. nsungwensis morphospace overlapping with that of L. songwensis (Fig. 8).

47

Figure 8. Principle Component Analysis (PCA) of 36 specimens of fossil ampullariids from the Songwe Member of the Nsungwe Formation. Polygons indicate the morphospace boundary for individual species. Green lines indicates biplot of the PCA which represent projections of the original axes. 48

Table 3.

Morphometric analysis on Nsungwe ampullariids: Percent variation described by principle components PC Eigenvalue Variance

1 0.0901 88.16%

2 0.0106 10.34%

3 0.0015 1.42%

4 <0.0001 0.08%

Table 4.

Morphometric analysis on Nsungwe ampullariids: Loadings for individual variables (Abbreviations. H. Total shell height; D. Total shell width; h. Aperture height and S. Spire height) PC 1 PC 2 PC 3 PC 4

H 0.4689 0.1718 0.3802 -0.7785

D 0.4297 0.5051 -0.7485 0.0047

h 0.3920 0.4526 0.5342 0.5968

S 0.6647 -0.7145 -0.0993 0.1942

The denogram genrated by cluster analysis indicates the presence of two groups

(Fig. 9). Bootstrap iterations support the presence of Cluster 1 by 45% and Cluster 2 with

32%. Cluster 1 is dominated by high-spired taxa, including both L. songweeovum and L. songweellipticus. Additionally, this group contains specimens of L. songwensis with comparatively high spires and also a single specimen of L. nsungwensis (RRBP 9515). 49

The second cluster include two smaller groups. The first group includes L. microovum, L. nsungwensis and specimens of L.. songwensis. The other group includes Carnevalea santiapillai, a single specimen of L. nsungwensis , and additional specimens of L. songwensis. Carnevalea santiapillai clusters out independently from the rest of the taxa in this group. Specimens of Lanites songwensis occur in both clusters whereas L. nsungwensis occurs mainly in Cluster 2.

Figure 9. Dendrogram produced from cluster analysis of 36 specimens of fossil ampullariids from the Songwe Member of the Nsungwe Formation. Numbers at nodes indicate percentages supported by 10000 bootstrap iterations 50

Implications

As with the PCA for modern specimens, high-spired forms and depressed forms generally occupy different regions of morphospace and produce relatively discreet groups in cluster analysis. Considerable morphospace is occupied by L.songwensis, which shows high variability in all four shell of the parameters on which the morphometric analyses were based (see Systematic Paleontology). The overlap of L. nsungwensis with L. songwensis can be differentiated where the former has a lower rate of whorl increase.

Thus, comparing two specimens at the same growth stage (whorl number), L. nsungwensis will possess a wider shell than L. songwensis .PCA performed on Nsungwe ampullariids clearly shows distinct morphospace occupancy of L. microovum and

Carnevalea santiapillai. Although effective in identifying morphotypes, the clustering of depressed forms with the two high-spired morphotypes and exclusion of L. microovum from Cluster 1 reiterates the importance of using both morphological and morphometric data when making taxonomic interpretations.

Morphometric Analyses of Fossil Ampullariid Specimens

PCA of the Nsungwe gastropods and two additional species of fossil Lanistes, L. ellipticus and L. carinatus, demonstrates clear separation specimens into multiple taxonomic groups (Fig. 10). All of the patterns recoved from PCA analysis of Nsungwe gastropods (Fig. 8) alone are preserved in this expanded analysis. In addition, the expanded data set indicates close grouping of L. ellipticus with L. songweellipticus.

Notably, no close grouping was observed between Nsungwe fossils and L. carinatus.

Similar to the PCA performed on Nsungwe specimens alone, 98.9% of total variation was 51 described by the first two principle components with PC1 attributing to 92.1% and PC2 describing 6.8% of the variation (Table 5). PC1 was strongly positively influenced by spire height whereas PC2 was strongly positively influenced by total shell width (Table

6).

Figure 10. Principle Component Analysis (PCA) performed on fossils from Nsungwe and other fossil ampulariids. Polygons indicate the morphospace boundary for individual species. Green lines indicates biplot of the PCA which represent projections of the original axes.

52

Table 5.

Morphometric analysis on all fossil ampullariids examined: Percent variation described by principle components PC Eigenvalue variance

1 0.1403 92.09%

2 0.0103 6.78%

3 0.0016 1.08%

4 <0.0001 0.05%

Table 6.

Morphometric analysis on all fossil ampullariids examined: Loadings for individual variables (Abbreviations. H. Total shell height; D. Total shell width; h. Aperture height and S. Spire height). PC 1 PC 2 PC 3 PC 4

H 0.4859 0.1502 -0.3677 -0.7786

D 0.4039 0.5139 0.7568 -0.0062 h 0.4170 0.4486 -0.5223 0.5934

S 0.6534 -0.7156 0.1389 0.2041

Like the analysis of Nsungwe fossils alone, cluster analysis of the expanded fossil data set recovered two groups (Fig. 11). Bootstrap iterations support the presence of

Cluster 1 and 2 equally by 48% each. The first cluster, which includes the high-spired specimens, is divided into two subgroups. In one of these subgroups, fossils of L. songweellipticus cluster with L. ellipticus. The other subgroup includes L. carinatus, L. 53 songweeovum, and several larger specimens of L.songwensis with comparatively high spires and a single specimen of L. nsungwensis RRBP 9515. The second cluster also birfucates into two subgroups. These match the subgroups described in Figure 8.

Figure 11. Dendrogram produced from cluster analysis of fossil ampullariids from Nsungwe and other fossil ampulariids. Numbers at nodes indicate percentages supported by 10000 bootstrap iterations.

54

Implications

Close grouping of L. ellipticus with L. songweellipticus suggested by both the

PCA and cluster analysis confirms the morphometric affinity of the two taxa. This is further corroborated by the presence of similar morphological characters as described in

Systematic Paleontology below. The lack of grouping of Nsungwe specimens with

Miocene L. carinatus in the PCA indicates the absence of this taxon among the fossil material collected from Tanzania. Although a single specimen of L. songwensis (RRBP

5282) clusters with the Miocene L. carinatus, their shell shapes differ. The specimen

RRBP 5282 has a more narrower shell with a higher spire. Thus different shapes may have comparable metrics and interpretations should be made with caution. Both the PCA and cluster analysis provides insight on to the morphological similarities between L. songweellipticus and Plio-Pleistocene L. ellipticus and distinctness of Carnevalea santiapillai.

Combined Morphometric Analyses of Fossil and Modern Ampullariid Specimens

PCA results of the data from all measured specimens combined indicate a clear separation between shells of different morphotypes (Fig. 12). In this analysis the first two principle components account for 99.1%of total variation with PC1 representing 92.0% and PC2 of 7.1% (Table 7). PC1 was strongly positively influenced by Spire height (S) whereas PC2 was strongly positively influenced by total shell width (D) (Table 8). These weightings have been consistent across all data treatments, indicating that these components exert primary control on partitioning of morphospace among the ampullariid species. Compared with morphospace occupied by modern species, L. songweeovum is 55 found in close proximity to Lanistes ovum adansoni and L. grasseti. Lanistes songweellipticus plots near Plio-Pleistocene specimens of L. ellipticus. The morphospace occupied by Lanistes songwensis overlaps with that of the Oligocene L. nsungwensis and modern L. nsendweensis, L. neavei, L. congicus, L. graueri and L. sinistrosus. Carnevalea santiapillai and L. microovum occupy unique regions in morphospace, plotting near the top and bottom of axis 2, respectively.

56

Figure 12. Principle Component Analysis (PCA) performed on fossil and modern ampullariid specimens. Polygons indicate the morphospace boundary for individual species. Green lines indicates biplot of the PCA which represent projections of the original axes. 57

Table 7.

Morphometric analysis on fossil and modern ampullariids: Percent variation described by principle components (Abbreviations. H. Total shell height; D. Total shell width; h. Aperture height and S. Spire height). PC Eigenvalue variance

1 0.1542 91.95%

2 0.0119 7.10%

3 0.0015 0.90%

4 <0.0001 0.04%

Table 8.

Morphometric analysis on fossil and modern ampullariids: Loadings for individual variables PC 1 PC 2 PC 3 PC 4

H 0.4990 0.0911 -0.3638 -0.7812

D 0.3757 0.6066 0.7005 -0.0154 h 0.4253 0.4031 -0.5645 0.5815

S 0.6550 -0.6791 0.2419 0.2265

Cluster analysis indicates the presence of two major groups (Fig. 13). Bootstrap iterations provide week support with Cluster 1 at 16% and Cluster 2 at 11% recovery.

Cluster 1 groups the majority of the depressed forms as well as L. microovum. Cluster 2 includes two subgroups. One subgroup includes the majority of the high-spired modern specimens of L. ovum, L. ovum elongata, L. ellipticus and L. purpureus. The second 58 subgroup further bifurcates. The first of these groups modern shells of L. ovum adansoni,

L. grasseti, L. bicarinatus, L. solidus, L. varicus L. libycus, L. intortus, two specimens of

L. nsendweensis, a poorly preserved form of L. ovum, and the Plio-Pleistocene L. ellipticus.

Single specimens of L. songwensis, Lanistes songweeovum and L. songweellipticus also occur in this cluster. Lanistes songweeovum clusters with L. grasseti; whereas L. songweellipticus clusters with Plio-Pleistocene L. ellipticus. Notably, none of the Plio-

Pleistocene material clusters with the modern representatives of the same species. Lanistes songwensis occurs scattered within both groups but occurs mainly with the depressed forms. Three out of the four specimens of L. nsungwensis groups in Cluster 1 with one optimizing in the high-spired group. Additionally, adult specimens of L. songwensis with comparatively high spires also cluster with the other high-spired specimens. Carnevalea santiapillai is found within the depressed cluster but does not cluster closely with any other taxa.

Implications

The PCA supports the taxonomic recognition of L. microovum and Carnevalea santiapillai as discrete species translated by their unique morphometrics. However, in the

PCA, L. microovum groups in the region with depressed morphotypes in PC1 axis and in the cluster analysis it groups within the Cluster 1. Morphologically, it is clearly distinct form depressed forms and is considered to be part of the high-spired morphotype (see

Systematic Paleontology). Carnevalea santiapillai occupies a unique region in morphospace and relatedly clusters independently on the dendogram. The distinct discoid shape gives it unique dimensions that are not comparable with any living forms of 59 ampullariids analyzed. These differences are elaborated further in Systematic

Paleontology

Although clustering as sister taxon to L. grasseti, L. songweeovum is distinctly different and can be differentiated from the former based on morphological characters

(see Systematic Paleontology). Both the dendogram and the PCA suggest that L. songweellipticus is more akin to Plio-Pleistocene material of L. ellipticus than with their modern specimens. Lanistes songwensis shows high disparity, as described earlier, and thus shows scattering in the dendogram and overlaps morphospace of multiple depressed species in the PCA. Lanistes nsungwensis does overlap with several modern depressed species but is clearly distinct from them due to its higher whorl expansion rate.

Both PCA and cluster analysis provides a good visualization of taxonomic affinity of Songwe fossils with modern and other Cenozoic material examined and proves to be effective as a precursor for taxon identification. It also provides understanding of the degree of variation that can be observed within a taxon. However, when making interpretations, it is important to consider morphological characters that are not reflected in linear measurements.

A significant feature of PCA analysis is that the Nsungwe specimens occupy a similar footprint in morphospace to the modern species. This is particularly notable because the Nsungwe specimens occupy an extremely limited geographic and temporal distribution (~10 km2 over less than 1 million years). The fact that these Oligocene fossils occupy a similar morphospace to modern species distributed over three continents with millions of years of divergence from their common ancestor is strong support for 60 recognition of an evolutionary radiation in the Nsungwe Ampullariidae that coincides with the timing of rift initiation as discussed more fully below.

61

Figure 13. Cluster analysis performed on fossils and modern ampullariids. Numbers at nodes indicate percentages supported by 10000 bootstrap iterations. 62

Taxonomic Composition of Nsungwe Ampullariids

Combined morphological and morphometric analyses yielded identification of five species of Lanistes and a single species of Carnevalea from the late Oligocene

Songwe Member, all of which are new to science. Apart from being novel taxa, these taxa also record the earliest appearance of high-spired Meladomus morphotypes (see

Systematic Paleontology) in the fossil record, which include L. songweeovum, L. songweellipticus and L. microovum. This is also the first record of the discoid genus

Carnevalea from Africa.

63

CHAPTER 6: SYSTEMATIC PALEONTOLOGY

Institutional abbreviations. ANSP, Academy of Natural Sciences, Drexel University,

Philadelphia; RRBP, Rukwa Rift Basin Project, specimens housed at Ohio University;

UCMP, University of California Museum of Paleontology.

Class GASTROPODA Cuvier, 1797

Subclass CAENOGASTROPODA Cox, 1960

Order ARCHITAENIOGLOSSA Haller, 1890

Superfamily AMPULLARIOIDEA Grey, 1824

Family AMPULLARIIDAE Gray, 1824

Genus CARNEVALEA Harzhauser et al., 2016

Type species. Lanistes thaytinitiensis Neubert and Van Damme, 2012 from the Zalumah

Formation (Eocene Series, Priobonian Stage) of Oman.

Emended diagnosis. A highly depressed discoidal shell. Body whorl angulate, adapically curved to horizontal, medially keeled and abapically convex. Early whorls weakly convex. Spire ranges from flat to slightly exsert. Apex pointed. Outer margin of aperture convex and adapical margin horizontal to slightly curved. Basal lip curved to pointed.

Umbilicus wide, margins carinated (modified from Neubert and Van Damme, 2012;

Harzhauser et al., 2016).

Occurrence. Eocene of Oman (Harzhauser et al., 2016) to late Oligocene of Tanzania

(present study).

Remarks. The ampullariid genus Carnevalea, which represents an entirely extinct clade, was introduced by Harzhauser et al. (2016) to describe the unique characters of a discoid 64 species, C. thaytinitiensis, formerly assigned to Lanistes by Neubert and Van Damme

(2012). This discoid ampullariid previously been documented only from the Eocene of

Oman. This material, is thus, the first recorded occurrence from Africa.

Carnevalea santiapillai sp. nov.

Fig. 14

Figure. 14. Carnevalea santiapillai (RRBP 16151C, Holotype). A. Apertural view; B. Apical view; C. Umbilical view. Top and bottom arrows on A point to the adapical portion of the outer lip and the basal lip respectively. Arrow on B points to the medial keel. Note that both adapical part of the outer lip and basal lip are curved. Scale bar 10 mm. 65

Derivation of name: Named in recognition of the services of world-renowned conservation biologist and zoologist, the late Professor Charles Santiapillai of the

University of Peradeniya, Sri Lanka, who truly exemplified excellence in teaching.

Holotype. RRBP 16151C, (Fig. 14), a well-preserved mold with a clearly detailed spire from the Nsungwe 3 locality within the Songwe Member of the Nsungwe Formation,

Tanzania. Specimen belongs to Antiquities Unit at the National Museum of Tanzania,

Dar es Salaam, Tanzania.

Additional material. None. Species represented only by the type specimen.

Diagnosis. Highly depressed, nearly planispiral shell with a slightly raised spire. Body whorl strongly angulate, adapically slightly convex, medially keeled, abapically convex.

Aperture large, broadly ovate in shape, oblique in position. Outer lip convex, adapically slightly curved, basal lip curved. Umbilicus open and deep.

Description. Medium-sized nearly planispiral shell with approximately 2.6 whorls. Body whorl broad (Total shell height [H]: Total shell width [D] 56.1%, see Table 9), adapically slightly convex, medially angulate and keeled, abapically convex (Fig. 14). Spire short, barely exsert and with a pointed apex. Shell spire represents 11% of the total shell length.

Early whorls convex, no ornamentation visible. Aperture large, broadly ovate in shape and obliquely positioned. Aperture height and width represents 89% and 50% of total shell height and width respectively. Aperture lips partially preserved, outer lip convex, adapically slightly curved (indicated by the top arrow in Fig. 14 A), parietal and collumelar lips poorly preserved, possibly concave and straight respectively. Basal lip 66 curved (indicated by the lower arrow in Fig. 14A). Umbilicus deep pit-like with an angulated margin.

Comparisons.—There are no modern ampullariids comparable to the morphology of

Carnevalea santiapillai. Carnevalea santiapillai shares a shell profile similar to C. thaytinitiensis (Neubert and Van Damme 2012) but differs in having an evenly convex outer lip which is a result of the slight curvature on the adapical portion of the outer lip

(see Fig. 14A). In C. thaytinitiensis the adapical segment of the outer lip is horizontal (see

Fig. 15). Furthermore, the basal lip of C. santiapillai is curved whereas in C. thaytinitiensis it is pointed (compare Figs. 14 and 15 and Neubert and Van Damme, 2012;

Harzhauser et al., 2016).

Due to keeled discoid morphology, Carnevalea santiapillai is distinct from all other ampullariids from the Nsungwe Formation.

Paleoecology. — There are no extant ampullariids comparable with the morphology of

Carnevalea. Hence, inferring the paleoecology of Carnevalea santiapillai is restricted to the information gleaned from sedimentological data. Prior this study, the only known occurrence of Carnevalea was from the Eocene Zalumah Formation in Thaytiniti, Oman

(see Neubert and Van Damme, 2012; Harzhauser et al., 2016). According to Neubert and

Van Damme (2012), the depositional environment of this setting comprised freshwater swamp, an interpretation corroborated by Harzhauser et al. (2016). Carnevalea santiapillai, however, was collected from Nsungwe 3 locality, which is interpreted as a lacustrine environment (Roberts, et al., 2010). Therefore, Carnevalea santiapillai is interpreted a paludal to lacustrine adapted ampullariid species. This interpretation fits 67 well with characters expected from shells adapted to live under stagnant flow (i.e., shells with lower spires, robustly calcified shells, carinated, shouldered, convex whorls, inflated whorls, see Van Damme and Pickford, 2003).

Occurrence. Nsungwe 3 locality (lacustrine facies), the Songwe Member of the Nsungwe

Formation, Rukwa Rift Basin, Tanzania (see Roberts et al., 2010). This locality is approximately 8° 56’ S latitude and 33° 12’ E longitude (Precise coordinates are on file at

Ohio University).

Figure 15: A-C. Eocene specimens of Carnevalea thaytinitiensis. A-C. NMBE 5018966 (Holotype). A. Apical view; B. Apertural view; C. Umbilical view. Plate modified from Neubert and Van Damme (2012), scale bar equals 10 mm. D-L. Carnevalea thaytinitiensis. Plate modified from Harzhauser et al. (2016). D. E. and I. TN15b; ONHM/TN/0009; F and J. TN8; ONHM/TN/0007. G and K. TN8; ONHM/TN/0008; H and L. TN15b; ONHM/TN/0010. Scale bars 5 mm. Note that in all specimens here, the adapical portion of the outer lip is horizontal and the basal lip is pointed. 68

Table 9.

Morphological characteristics of Carnevalea santiapillai (Measurements are in mm, abbreviations: H, Total shell height; D, Total shell width; h, Aperture height; S, Spire height; W. Number of whorls). Specimen W H D h S H/D h/H S/H Number

16151C ~2.6 15.1 27.0 13.4 1.7 0.56 0.89 0.11

Genus LANISTES Montfort, 1810

Type species. Lanistes olivierii Montfort, 1810; [=Lanistes boltenianus (Röding, 1798) = syn. Lanistes carinatus (Olivier, 1804)]; Recent, Egypt.

Emended Diagnosis. Hyperstropic sinistral shells with depressed to conic profiles, whorls range from evenly convex to angulate, umbilicus open or closed, umbilical margin and whorls may be smooth or carinate. (Modified from Thiele, 1992; Brown, 1994).

Occurrence. Eocene-Recent. Modern species of Lanistes are found in Africa (Nile Delta to Natal) and Madagascar (Brown, 1994; Neubert and Van Damme, 2012), but fossil species occur in Arabia (Saudi Arabia and Oman) and Africa.

Remarks. Species attributed to Lanistes exhibit a diverse array of morphologies ranging from high-spired elongated forms to depressed shells with spires sunken below the body whorl. Traditionally, three subgenera of Lanistes were recognized based on conchological characters: Lanistes sensu stricto, Lanistes (Meladomus) and Lanistes (Leroya). In this study, Total Shell Height: Total Shell Width (H:D) and Spire Height :Total Shell Height

(S:H) ratios were combined with qualitative characters to differentiate between these morphotypes. The Lanistes sensu stricto morphotype is characterized by shells with broad 69 whorls with a depressed to ovate profile. Shells typically have a large umbilicus, prominent whorl angulations and may contain carinations. Quantitatively, H:D ratios less than 1 and S:H ratios less than 0.32. The Meladomus morphotype is characterized by a narrow umbilical opening, absence of whorl angulation or carinations, H:D ratios greater than or equal to 1 and S:H ratios greater than or equal to 0.32. For the purpose of this study, the Leroya morphotype is characterized by shells with either Total Shell Height or

Total Shell Width equal or less than 25 mm that have a closed umbilicus and smooth, angulated or carinated whorls. However, it should be noted that species attributed to

Leroya can sometimes exceed this maximum dimensional value (see Brown, 1994).

Cowie et al. (2015) recognized 43 species of Lanistes. However, comparisons in this study are based on the 21 modern species described in Brown (1994) as this is the most comprehensive publication with detailed morphological descriptions of modern Lanistes species.

Species attributable to Lanistes from the Songwe Member include both high- spired (=Meladomus morphotype) and depressed (=Lanistes sensu stricto morphotype) morphotypes. Apart from describing six novel taxa, this study also record the oldest high-spired Meladomus morphotype specimens recorded.

70

Lanistes microovum sp. nov.

Fig. 16

Figure 16. Lanistes microovum. Holotype specimen RRBP 11167. A. Apertural view; D. apical view. Paratype specimens RRPB 9196. B. Apertural view; E. Apical view. 7445C.C. Apertural view; F. Apical view. Scale bar 10 mm. 71

Derivation of name. Named to reflect the diminutive size of the new species and its resemblance to the modern Lanistes ovum.

Holotype. RRBP 11167 (Fig. 16A and D), a well-preserved mold with a clearly detailed spire. Specimens belong to the Antiquities Unit at the National Museum of Tanzania, Dar es Salaam, Tanzania.

Paratypes. RRBP 9196A (Fig. 16 B and E) and 7445C (Fig. 16 C and F)

Diagnosis. Globose, high-spired Lanistes (H:D ≥1; S:H≥0.32), whorl angulations and carinae lacking, aperture ovate and obliquely positioned, outer lip and columellar lips evenly curved.

Description. Medium sized globose shells with approximately 2.6 whorls in holotype and approximately 2.7 whorls preserved in paratypes. Body whorl evenly convex. Early whorls lacking angulations. Spire long, ranging from 32-38% (average 35%, standard deviation 3%; see Table 10) of total shell height. Apex pointed. Aperture broadly ovate in shape and oblique in position. Aperture height comprises 63-68% (average 65%, standard deviation 2%; see Table 10) of total shell height. Outer margin evenly convex, collumelar margin slightly curved. Parietal margin poorly preserved in all specimens, possibly angled to slightly convex. Umbilicus open (see Fig. 16).

Comparisons.—Lanistes microovum closely resembles Lanistes ovum Troschel 1845 by having curved columellar margin, which can also be used to distinguish over Lanistes ellipticus Martens 1866. This species can be differentiated from Lanistes grasseti Morlet

1863 by lacking ribs and from L. purpureus Jonas 1839 by having an open umbilicus (see

Fig. 17). 72

Figure 17. Modern Lanistes species of the high-spired Meladomus morphotype. A. Lanistes ovum ANSP176674-3; B. L. purpureus ANSP120161-1; C. L. ovum elongata ANSP448411-2; D. L. grasseti; ANSP 63044; E. L. ovum adansoni ANSP146190-8; F. L. ellipticus 156766-2. Scale bar 10 mm.

Lanistes microovum differs from similar Nsungwe species L. songweeovum by its convex body whorl and from L. songweellipticus by having a comparatively curved 73 columellar margin. This species can be distinguished from the Miocene Lanistes olukaensis Van Damme and Pickford 1995 by having an open umbilicus and evenly convex whorls and from L. recki Reck and Dietrich 1923 by its open umbilicus. Reck and

Dietrich 1923 consider this specimen as a sub recent fauna. However, Connolly (1928) suggest a late tertiary age for L. recki (see Adam, 1959).

Remarks. This species represents a juvenile stage of a high-spired Lanistes. The preservation of 2.6-2.7 body whorls, however, indicates that these specimens represent adult ontogenetic stages, albeit of small size. Consequently, L. microovum may have evolved via paedomorphosis.

Lanistes microovum together with Lanistes songweeovum and L. songweellipticus

(see below) represents the oldest fossils of the high-spired Meladomus morphotypes found to date.

Paleoecology.—Lanistes microovum exhibits a phenotype comparable with the modern

Lanistes ovum, which is known to inhabit standing and slow flowing waters with muddy substratum and vegetation, floodplains settings with soft marginal mud, seasonal pans and rain pools (Appleton, 1977; Betterton, 1984; Brown, 1994). Two of the three specimens of Lanistes microovum (RRBP 9196, RRBP 11167) were collected from

Nsungwe 2, which is interpreted as a lacustrine setting; whereas RRBP 7445C was collected from TZ01, which is interpreted as a fluvial environment (Roberts et al., 2010).

Based on the habitats occupied by the extant analog Lanistes ovum, Lanistes microovum was probably capable of inhabiting both lacustrine and fluviate settings. 74

Occurrence. Nsungwe 2 locality (lacustrine facies) and TZ01 locality (fluvial facies),

Songwe Member of the Nsungwe Formation, Rukwa Rift Basin, Tanzania (see Roberts et al., 2010). These localities are approximately 8° 56’ S latitude and 33° 12’ E longitude

(Precise coordinates are on file at Ohio University).

Table 10.

Morphological characteristics of Lanistes microovum (Measurements are in mm, abbreviations: H, Total shell height; D, Total shell width; h, Aperture height; S, Spire height; W. Number of whorls). Specimen Locality W H D h S H/D h/H S/H Number RRBP 11167 Nsungwe 2 ~2.6 11.7 11.8 7.4 4.4 0.99 0.63 0.38 (Holotype) RRBP 9196 Nsungwe 2 ~2.7 10.2 9.6 6.6 3.5 1.06 0.65 0.34 (Paratype) RRBP 7445C TZ01 ~2.7 9.3 9.3 6.3 3.0 1.00 0.68 0.32 (Paratype) Average 1.02 0.65 0.35 Standard 0.04 0.02 0.03

Deviation

75

Lanistes nsungwensis s sp. nov.

Fig. 18

Figure 18. Lanistes nsungwensis. Holotype RRBP 16081. A. Apertural view; C. Apical view. Medial carination indicated by the arrow. Paratype 13311B. B. Apertural view; D. Apical view. E. F. and G. Comparison between whorl expansion rates. E. Apical view of L. nsungwensis (RRBP16081), F. Apical view of L. songwensis (RRBP 5492B). RRBP16081 comprise of approximately 2.2 whorls whereas RRBP 5492B has 2.3 whorls. Note that although both specimens have approximately equal number of whorls, L. nsungwensis has a much wider shell. G. Apical view of a modern Lanistes carinatus (ANSP 367298-11) 76

Derivation of name. Named after the Nsungwe River where fossils of this species were exposed

Holotype. RRBP 16081, (Fig. 18) a well-preserved mold with partially preserved spire.

Specimens belong to the Antiquities Unit at the National Museum of Tanzania, Dar es

Salaam, Tanzania.

Paratypes. RRBP 13311B; RRBP 12346

Additional material. RRBP 9515

Diagnosis. Depressed shell (H:D <1; S:H <0.32), body whorl convex, wider and more angulated, whorls sunken adapically near sutures forming a slight angulation. Medial carination maybe present. Early whorls convex, spire exsert, apex flat. Aperture broadly ovate, obliquely positioned, aperture lips poorly preserved in all specimens. Umbilicus deep, carinate in holotype.

Description. A medium-sized depressed shell with H:D ratios ranging from 0.88 to 0.73

(average 0.79, standard deviation 0.06. see Table 11). Body whorl convex and angulated.

Body whorl sunken adapically near sutures forming a slight angulation. Medial carination present in holotype (Fig. 18A). Early whorls convex. Spire exsert, spire height represents

22-37% (average 29% standard deviation 6%) of total shell height. Apex flat. Aperture ovate in shape, obliquely positioned, aperture height represents 63-78% (average 71%, standard deviation 6%) of total shell height. Aperture lips poorly preserved in all specimens. Umbilicus deep pit-like. Umbilical margin preserved only in holotype, which is carinated. 77

Comparisons. Amongst the extant Lanistes species, Lanistes nsungwensis is most comparable with L. carinatus Olivier 1804 (Cyclostoma Olivier 1804) in shell shape, low

H:D ratios (average 0.76, standard deviation 0.03, See Appendix D), high whorl expansion rate, deep pit-like umbilicus and presence of a medial carination. However, the initial whorls appear to be much wider than in L. carinatus (see Fig. 18 E and G), which suggests a greater whorl expansion rate in Lanistes nsungwensis.

Among previously described fossils, L. nsungwensis resembles L. grabhami and

L. antiquus. However, L. nsungwensis is characterized by a higher spire than both L. grabhami and L. antiquus (see Fig. 19)

Lanistes nsungwensis differs from the other depressed morphotype from

Nsungwe, L. songwensis, by having a higher rate of whorl expansion, resulting in a low spired and broader shell. Further, L. nsungwensis has a more pronounced medial body whorl angulation than L. songwensis. Lanistes nsungwensis is clearly distinct from

Carnevalea santiapillai which has a keeled discoid morphology and from the high spired non angulated Meladomus morphotypes.

Remarks. All fossils of L. nsungwensis are poorly preserved especially the spire whorls and the aperture. Although this hinders comparative species analyses between Nsungwe fossils and other comparable Paleogene/Neogene morphotypes, the high whorl expansion rate makes this species unique among all Lanistes investigated from the Nsungwe

Formation. Furthermore, the poor preservation of aperture lips produces a more conservative measure for shell diameter and may result in lower values for H:D ratios.

This in turn may result in erroneous assignment of Lanistes nsungwensis among Lanistes 78 songwensis. This reiterates the importance of both morphological and morphometric data in species assignment.

Paleoecology. — Lanistes nsungwensis closely resemble Lanistes carinatus which is found in both standing and slow flowing waters with vegetation (Brown. 1994).

Considering fossils, Lanistes nsungwensis is comparable with Lanistes antiquus from the

Lutetian of Egypt and Lanistes grabhami from the Eocene Hudi Chert Formation, Sudan.

Newton (1912), states that Lanistes antiquus was collected from an estuarine to brackish water depositional environment which does not agree with the late Oligocene depositional environments of the Rukwa Rift Basin. Depositional setting for Lanistes grabhami is interpreted as extensive freshwater swamps, ponds with rich vegetation

(Harzhauser et al., 2017). Fossils of Lanistes nsungwensis were collected from Nsungwe

2, Nsungwe 3 and Bigwall (Nsungwe 2B) which are lacustrine settings, thus, Lanistes nsungwensis is interpreted as a lacustrine adapted species.

Occurrence. Nsungwe 2 (lacustrine facies), Nsungwe 3 locality (lacustrine facies),

Bigwall/Nsungwe 2B (lacustrine facies), Songwe Member of the Nsungwe Formation,

Rukwa Rift Basin, Tanzania (see Roberts et al., 2010). These localities are approximately 8° 56’ S latitude and 33° 12’ E longitude (Precise coordinates are on file at

Ohio University).

79

Figure 19. Fossil material comparable with Lanistes nsungwensis. Lanistes antiquus from the Lutetian of Egypt. A. Apertural view, B. Umbilical view. Shell height 31 mm, shell width 45 mm (images from Blanckenhorn, 1901). C-I. Lanistes grabhami from Eocene Hudi Chert Formation C. Apical view, D. Umbilical view of NHMW 2016/0219/0002; E. Apical view, F Apertural view, G. Side view of NHMW 2016/0219/0001 (images from Harzhauser et al., 2017) H. Apertural view, I. Apical view of Lanistes grabhami (Holotype- G. 54985) from Eocene Hudi Chert Formation. Shell height 38 mm, shell width 49 mm (images from Cox, 1933).

80

Table 11.

Morphological characteristics of Lanistes nsungwensis (Measurements are in mm, abbreviations: H. Total shell height; D. Total shell width; h. Aperture height; S. Spire height; W. Number of whorls; C. Carinae; Y. Carination present; N. Carination absent). Specimen Locality W H D h S C H/D h/H S/H Number RRBP Nsungwe 3 ~2.2 12.6 14.4 9.8 2.8 Y 0.88 0.78 0.22 16081 (Holotype) RRBP Bigwall ~2.8 13.8 18.1 9.8 4.0 N 0.76 0.71 0.29 13311B (Nsungwe (Paratype) 2B) RRBP Bigwall ~2.1 11.5 14.6 8.5 3.0 N 0.79 0.74 0.26 12346 (Nsungwe (Paratype) 2B) RRBP Nsungwe 2 NA 19.8 27.2 12.4 7.3 N 0.73 0.63 0.37 9515 Average 0.79 0.71 0.29 Stranded 0.06 0.06 0.06 Deviation

81

Lanistes songweellipticus sp. nov.

Fig. 20

Figure 20. Lanistes songweellipticus (Holotype, RRBP8284). A. Apertural view; B. Apical view. Scale bar 10 mm. Note that the columnar margin is straighter than in L. songweeovum.

Derivation of name. Name reflects the occurrence of this species along the Songwe

River, where the collection site is exposed, and its resemblance to the modern species

Lanistes ellipticus Martens 1866.

Holotype. RRBP 8284 (Fig. 20) a well-preserved shell with clearly detailed spire.

Specimen belongs to the Antiquities Unit at the National Museum of Tanzania, Dar es

Salaam, Tanzania.

Additional material. None. Species represented only by the type specimen. 82

Diagnosis. Globose, high-spired Lanistes (H:D ≥1; S:H≥0.32), spire 37% of total shell height, whorl angulation and carinae lacking, aperture ovate and obliquely positioned, outer lip evenly convex, columellar lip straighter, umbilicus open.

Description. Large, globose shell with approximately 4.8 whorls preserved. Body whorl evenly convex. Surface of body whorl devoid of ornamentation except for growth lines.

Early whorls lack angulations. Spire long, represents 37% of total shell height. Apex pointed (see Fig. 20). Aperture broadly ovate in shape and obliquely oriented. Aperture height represents 63% of total shell height. The outer margin is evenly convex, collumelar margin nearly straight. Parietal margin poorly preserved, possibly slightly curved. Umbilicus open.

Comparisons.—Lanistes songweellipticus is placed within Meladomus morphotype based on the presence of a long spire and evenly convex whorls. Considering extant species,

Lanistes songweellipticus most closely resemble Lanistes ellipticus (Fig. 21). Modern L. ellipticus has a straighter columellar margin than in L. ovum (Brown, 1984), a characteristic which is also evident in Lanistes songweellipticus (see Fig. 20). Lanistes songweellipticus is distinguished from L. grasseti due to the absence of strong ribs and from L. purpureus by having an open umbilicus (see Fig. 17 and Brown, 1994). The present distribution of Lanistes ellipticus Martens 1866 includes the Democratic Republic of Congo, Malawi, Mozambique and Tanzania (Jørgensen et al., 2010a).

Morphometrically, Plio-Pleistocene specimens of L. ellipticus from the Chiwondo beds (Fig. 22) exhibit an average total shell height to total shell width ratio of 1.19

(standard deviation 0.08) and an average spire height to total shell height ratio of 0.39 83

(standard deviation 0.05), (see Appendix E) whereas modern specimens show an average total shell height to total shell width ratio of 1.21 (standard deviation 0.04) and an average spire height to total shell height ratio of 0.37 (standard deviation 0.04).

Measurements of Lanistes songweellipticus (H:D. 1.12, S:H. 0.37) falls closely amongst the Plio-Pleistocene specimens than with modern specimens. This results in the close placement of Lanistes songweellipticus with Plio-Pleistocene material of Lanistes ellipticus (see Appendix D and E; Figs. 10, 11, 12 and 13).

Lanistes songweellipticus is distinct from the other Meladomus morphotypes from the Nsungwe Formation. Lanistes songweellipticus is distinguished from Lanistes microovum by having a comparatively straighter columellar lips and from L. songweeovum, by having a comparatively straighter columellar lips and more evenly convex whorls. The authors consider Lanistes songweellipticus distinct from both the

Plio-Pleistocene and the modern based on the age gap separating the Plio-Pleistocene and modern species with Nsungwe fossils. Numerous studies have demonstrated that snails that do not produce planktonic larvae have a lower species longevity (see Hansen, 1978;

Gill and Martinell, 1994). Hansen (1978) showed that volutes that produce planktonic larvae have a mean species duration of 4.4 million years whereas volutes that lack planktonic larval forms have a mean species longevity of 2.2 million years. Similarly,

Gill and Martinell (1994), demonstrated that species of the genus Nassarius that develop non-plantotrophic larvae have an absolute species duration ranging from 1.1-4.5 million years. Based on these studies, it is reasonable to assume a maximum species longevity for non-planktonic snails of approximately 4.5 million years. However, it should be noted 84 that above mentioned taxa are marine, hence are generally subjected to less environmental perturbation than freshwater forms. Furthermore, the genus Lanistes is geographically constrained and experience greater environmental adversities (i.e., desiccation) hence should have a much lower species longevity.

Lanistes songweellipticus, together with Lanistes songweeovum and L. microovum, represent the oldest fossils of the high-spired Meladomus morphotypes found to date.

Paleoecology. — Lanistes songweellipticus is morphologically similar to the modern Lanistes ellipticus. The latter is found in clear fluviate waters around a depth of

0.75 m and above with gravel substratum (Pilsbry and Bequaert, 1927) and marshes around Lake Malawi and in the Zambezi River (Berthold, 1990a,b; Brown, 1994; Köhler and Glaubrecht, 2006). However, in the molecular phylogenetic analysis performed by

Schultheiß et al. (2009), specimens of Lanistes ellipticus collected from the Malawi Rift did not cluster with Lanistes ellipticus collected from their type locality. Thus, suggesting the presence for an endemic species that resembles Lanistes ellipticus in the Malawi Rift

(see Schultheiß et al., 2009). However, for the purpose of this study, the presence of ellipticus-like form in the swamps and lagoons in the vicinity of the lake justifies these as potential habitats for Lanistes songweellipticus. Within the Songwe Member, Lanistes songweellipticus was collected from TZ01 South, which is interpreted as a fluvial depositional environment (Roberts et al., 2010). The high-spired streamlined shell, sedimentological interpretation and the ability of extant analog L. ellipticus to occupy fluvial settings suggest that Lanistes songweellipticus was a fluvial adapted species. 85

Occurrence. TZ01 South Locality (fluvial facies), Songwe Member of the Nsungwe

Formation, Rukwa Rift Basin, Tanzania (see Roberts et al., 2010). This locality is approximately 8° 56’ S latitude and 33° 12’ E longitude (Precise coordinates are on file at

Ohio University).

Figure 21. Modern specimens of Lanistes ellipticus. A. ANSP 156766-3; B. ANSP 156766-5; C, ANSP 156766-1. Scale bar 10 mm.

86

Figure 22. Plio-Pleistocene- fossils of Lanistes ellipticus from Chiwondo Beds of Malawi. A. UCMP 154228; B. UCMP 154227; C. UCMP 154226; D. UCMP 154225; E. UCMP 154224. Scale bar 10 mm.

Table 12.

Morphological characteristics of Lanistes songweellipticus (Measurements are in mm, abbreviations: H, Total shell height; D, Total shell width; h, Aperture height; S, Spire height; W. Number of whorls). Specimen W H D h S H/D h/H S/H Number RRBP 8284 ~4.8 35.3 31.4 22.1 13.1 1.12 0.63 0.37 (Holotype)

87

Lanistes songweeovum sp. nov.

Fig. 23

Figure 23. Lanistes songweeovum (Holotype, RRBP11122). A. Apertural view; B. Apical view. White arrow points to the abaxial malleated whorl surface. Scale bar 10 mm 88

Derivation of name. Name reflects the occurrence of this species in the Songwe Member of the Nsungwe Formation and its resemblance to the modern species Lanistes ovum

Troschel 1845.

Holotype. RRBP 11122, (Fig.23) a well-preserved internal mold with clearly detailed spire, from the Nsungwe Gastropod Locality within the Songwe Member of the Nsungwe

Formation, Tanzania. The specimen belongs to the Antiquities Unit at the National

Museum of Tanzania, Dar es Salaam, Tanzania.

Additional material. None. Species represented only by the type specimen.

Diagnosis. Globose high-spired Lanistes, spire 45% of total shell height, lacking whorl angulations and carinae, body whorl slightly malleated abaxially towards aperture, aperture ovate and obliquely positioned, outer lips evenly convex, columellar lip slightly curved, umbilicus open.

Description. Medium-sized, globose shell with approximately 3.7 whorls preserved.

Body whorl evenly convex but flattened abaxially towards aperture (Fig 23A). Body whorl devoid of surface ornamentation. Early whorls lacking angulation. Spire long, represents 45% of total shell height. Apex pointed. Aperture broadly ovate in shape and oblique in position. Aperture height represents 55% of total shell height. The outer margin is evenly convex, collumelar margin slightly curved. Parietal margin poorly preserved, possibly angled to slightly convex. Umbilicus open.

Comparisons.—The high-spired Meladomus type Lanistes songweeovum most closely resembles Lanistes ovum Troschel, 1845 (Fig. 17). Within the L. ovum clade, modern taxa with malleated whorls have also identified (Brown, 1994). Lanistes songweeovum 89 can be distinguished over Lanistes ellipticus and Lanistes grasseti by having curved columellar margins and lacking ribs on whorls respectively. Additionally, Lanistes songweeovum is distinct over Lanistes purpureus by having an open umbilicus (see Figs.

17 and 23). The present distribution of L. ovum is extensive and includes Angola,

Botswana; Burundi, Cameroon, Chad, Democratic Republic of Congo, Kenya, Malawi,

Mozambique, Namibia, Niger, Nigeria, Somalia, South Africa, South Sudan, Sudan,

Zambia and Zimbabwe (Jørgensen et al., 2010b). The biological distinctiveness of

Lanistes songweeovum over the modern Lanistes ovum is based on the time gap between modern fauna and Nsungwe fossils (i.e., exceeds the normal species longevity for gastropods, see Comparison section for Lanistes songweellipticus).

Lanistes songweeovum differs from Lanistes sensu stricto forms (L. songwensis, L. nsungwensis) from the Nsungwe Formation by its more elongated shell profile, higher spire length, lack of whorl angulations and carination. It resembles Lanistes songweellipticus which shares all Meladomus traits, but differs from Lanistes songweeovum by its lower spire length (37% of total shell height), more convex body whorl and straighter columellar lip. Columellar lips of both L. songweeovum and L. songweellipticus are poorly preserved.

However, it is evident that in L. songweeovum, the lip tends to be slightly convex (see Figs.

20 and 23). Lanistes songweeovum differs from Lanistes microovum which lacks malleated whorls. Van Damme and Pickford (1995) described the high-spired Lanistes olukaensis from the Miocene Lower Oluka Formation, of the Albertine Rift (Fig. 24A and B). This species resembles Lanistes songweeovum in lacking whorl angulation, flattened whorls and slightly curved columellar margin but differs by having a closed umbilicus and the presence 90 of an acuminate ovate aperture. Lanistes songweeovum can be distinguished over Lanistes recki Reck and Dietrich 1923, which appears to have a closed umbilicus in the original illustration (Fig. 24C).This is further corroborated by Reck and Dietrich (1923) indicating that that L. recki resembles L. stuhlmanni Martens 1897, a Leroya morphotype (see Reck and Dietrich 1923; Adam, 1959; Connolly, 1928; Brown, 1994).

Lanistes songweeovum, in conjunction with Lanistes songweellipticus and Lanistes microovum represents the oldest fossils of the high-spired morphotype of Lanistes identified to date. Younger fossils of high-spired Lanistes have been described. These include L. ovum from Miocene and Pliocene deposits of Manonga Valley, Tanzania, (Van

Damme and Gautier, 1997), Miocene L. olukaensis from Lower Oluka Formation, Toro

District, Uganda (Van Damme and Pickford Van Damme and Pickford, 1995), and the

Tanzanina Lanistes recki which is either Pleistocene or sub-recent in age (see Reck and

Dietrich, 1923; Adam, 1959). In addition, Connolly, 1927, mentioned the presence of a poorly preserved Quaternary specimen belonging either to L. solidus or L. ovum from Lake

Nyasa. Furthermore, Van Damme and Pickford (1995) and Van Damme and Gauitier

(1997) mention the presence of a L. ovum-like form in the lower middle Miocene of

Maboko Island in Lake Victoria and Schultheiß et al. (2009) states the presence of a

Lanistes ellipticus like form in Unit 3A of the Chiwondo Beds.

Paleoecology.— Lanistes songweeovum resembles the modern Lanistes ovum, which inhabit standing and slow flowing waters with muddy substratum and vegetation, floodplains settings with soft marginal mud, seasonal pans and rain pools (Appleton,

1977; Betterton, 1984; Brown, 1994). The single specimen of Lanistes songweeovum was 91 collected from Nsungwe Gastropod Locality, which is interpreted as a low energy seasonal pool setting (Roberts et al., 2010). Based on the habitats occupied by the extant analog Lanistes ovum, Lanistes songweeovum may have been capable of inhabiting both lacustrine and fluviate settings.

Occurrence. Nsungwe Gastropod Locality (lacustrine facies), Songwe Member of the

Nsungwe Formation, Rukwa Rift Basin, Tanzania (see Roberts et al., 2010). This locality is approximately 8° 56’ S latitude and 33° 12’ E longitude (Precise coordinates are on file at Ohio University).

Figure 24. A-B. Lanistes olukaensis (Holotype, NY 92'92). A. Diagrammatic sketch of the holotype. B. Actual holotype specimen. Total shell height 28.5 mm, shell width 28.0 mm (images from Van Damme and Pickford, 1995). C. Apertural view of Lanistes recki from Tanzania. Shell height 30 mm, Shell width 28 mm, height of last whorl 22 mm (image from Reck and Dietrich, 1923).

92

Table 13.

Morphological characteristics of Lanistes songweeovum (Measurements are in mm, abbreviations: H, Total shell height; D, Total shell width; h, Aperture height; S, Spire height; W. Number of whorls). Specimen W H D h S H/D h/H S/H Number

RRBP 11122 ~3.7 25.5 21.9 14.1 11.4 1.16 0.55 0.45 (holotype)

93

Lanistes songwensis sp. nov.

Fig. 25

Figure 25. Lanistes songwensis. Holotype RRBP9265B A. Apertural view; E. Apical view. Paratypes RRBP 9265A. B. Apertural view; F. Apical view. RRBP8571AB C. Apertural view; G. Apical view. Note the medial carination indicated by the white arrow. D. Large adult specimen of L. songwensis (RRBP7677A). H. Three lirae indicated by arrow on the second whorl of RRBP 4008. I. Three lirae indicated by arrow on the second whorl of RRBP 10053. J. umbilical carination indicated by arrow on RRBP 8349. K. Two basal carinae indicated by arrows around the umbilical region of RRBP 9475A. Scale bar 10 mm. 94

Derivation of name. Named for the Songwe River, where the specimens were collected.

Holotype. RRBP 9265B (Fig. 25 A and E), a well-preserved shell with clearly detailed spire. Specimens belong to the Antiquities Unit at the National Museum of Tanzania, Dar es Salaam.

Paratypes. RRBP 9265A; RRBP 9234, RRBP 8571AB, RRBP 5492A, RRBP 5492B,

RRBP 4008, RRBP 8349B, RRBP 7677A RRBP 4455, RRBP 10002, RRBP 11120G.

Additional material. RRBP 11120A, RRBP 11120F, RRBP 11120H, RRBP 11120B,

RRBP 11120K, RRBP 11120J, RRBP 5676, RRBP 4199, RRBP 5435, RRBP 9066A,

RRBP 5068A, RRBP 3052, RRBP 10053, RRBP 6125, RRBP 9475B, RRBP 5436,

RRBP 6186, RRBP 5209, RRBP 7046, RRBP 5540, RRBP 7111, RRBP 5282

Diagnosis. Shell depressed (H:D <1; S:H <0.32), body whorl convex, bulges out, sunken adapically near sutures forming an angulation. Juveniles may possess medial carination.

Early whorls convex, show similar angulation near sutures. Spire exsert may be either pointed or flattened. Aperture broadly ovate, obliquely positioned, columellar margin curved, parietal margin poorly preserved in all specimens, possibly angled or slightly concave. Umbilicus deep and pit like, umbilical margin ranges from moderately angulate to carinate.

Description. A depressed shell with a H:D ratios ranging from 0.80-1.08 (average 0.90, standard deviation 0.06, see Table 14). Body whorl wide, evenly convex and sunken adapically near sutures forming a strong angulation in juveniles (indicated by white arrow in Fig. 25 E), angulations lesser in adults. Medial carination present in several juvenile specimens (indicated by white arrow in Fig. 25 C). Early whorls convex with angulation 95 near suture. Spire exsert, range from 16-38% of total shell length (average 28%, standard deviation 5%). Apex typically pointed (Fig. 25 A, B and I) but is nearly flat in some specimens (Fig. 25 C and H). Aperture ovate, obliquely positioned, ranges from 62-84% of total shell height (average 71%, standard deviation 5%), collumelar margin curved.

Parietals poorly preserved, possibly angled or slightly convex. Umbilicus deep and pit- like. Umbilical margin ranges from moderately angulated to carinate (Fig. 25 J).

Accessory ornamentation also occurs on particularly well-preserved specimens. Two specimens, RRBP 4008 (Fig. 25 H) and RRBP 10053 (Fig 25 I) additionally exhibit three fine lirae on the second whorl adjacent to the suture line (see arrows in Fig. 25 H and I).

In addition, RRBP 9475A has two basal carinae, which appear to be continuous around the base (indicated by the arrows in Fig. 25 K).

Comparisons—Lanistes songwensis falls within the Lanistes sensu stricto morphotype based on the depressed shell profile, whorl angulation and presence of carinae. This species possess a highly variable morphology in terms of spire profile and carination.

Brown (1994) described 13 species that were initially part of the Lanistes sensu stricto subgenus. These include L. carinatus, L. intortus, L. bicarinatus, L. congicus, L. nsendweensis, L. neavei, L. varicus, L. libycus, L. ciliatus, L. alexandri, L. solidus, L. nyassanus and L. nasutus. Considering the modern specimens, Lanistes songwensis is most comparable with L. carinatus, L. nsendweensis and L. neavei. Lanistes songwensis resemble L. carinatus by having a similar shell profile, deep pit like umbilicus and medial carination in early whorls (which is comparable with carinated juveniles of the former)

(Fig. 26A). However, Lanistes songwensis differs from L. carinatus which has a lower 96

H:D ratio (average 0.76, standard deviation 0.03, See Appendix D). Lanistes songwensis resembles L. nsendweensis in overall shape (Fig. 26B). However, juvenile specimens of

L. nsendweensis have flattened whorl surfaces adapically extending from the suture, which is not seen in L. songwensis. Further, adults of L. songwensis reach a greater size than those of L. nsendweensis. No medial carination was observed in any of the museum specimens of L. nsendweensis examined by the authors. Lanistes songwensis also resembles L. neavei in overall shape (See Fig. 26C). However, whorls are not as sunken in juveniles of Lanistes songwensis but tends to flatten out near the suture.

Numerous fossil Lanistes species have assigned to the subgenus Lanistes sensu stricto. These include: L. tricarinatus Neubert and Van Damme 2012; Lanistes heynderycxi Van Damme and Pickford 1995; Lanistes hadotoi Van Damme and Pickford

1995; Lanistes asellus Van Damme and Pickford; Lanistes senuti Van Damme and

Pickford 1995; Lanistes nkondoensis Van Damme and Pickford 1995; Lanistes gautieri

Van Damme and Pickford; Lanistes trochiformis Van Damme and Pickford; Lanistes gigas Van Damme and Pickford 1995; L. shantili Abbas 1971; Lanistes bishopi Gautier

1970; Lanistes sodaensis Abbass 1967; L. abbassiensis Abbass 1962; L. mahmoudi

Abbass 1977; L grabhami Cox 1933; L bartonianus Blanckenhorn 1901; L. irregularis

Blanckenhorn1901; L. antiquus Blanckenhorn, 1901; L. solidus Smith 1877; L. carinatus

Olivier 1804 (Cyclostoma Olivier 1804).

Of the fossil taxa mentioned above, Lanistes songwensis is most comparable with

Lanistes heynderycxi (Fig. 27) from the Cenozoic Albertine Rift. The two species have comparable H:D ratios (Average 0.89, standard deviation 0.04 for Lanistes heynderycxi, 97 see Van Damme and Pickford, 1995), neratoid shape, curved columellar margin and open umbilicus with angulate margins. Van Damme and Pickford (1995) do not refer to the spire height numerically, but indicate that it is low. Illustrated specimens of L. heynderycxi (see Fig. 27) appears to have proportionally lower spire heights than specimens of Lanistes songwensis (see Fig. 25). Further L. heynderycxi lacks angulations adjacent to sutures. Thus, on the basis of lower spire height and potential lack of whorl angulation, Lanistes songwensis is considered to be distinct from L. heynderycxi.

Compared to other Nsungwe Lanistes species, L. songwensis is distinct from L. nsungwensis by having a lower rate of whorl expansion, thus a higher H:D ratio and from

Carnevalea santiapillai which is discoid in shape and has a medial keel. Further, L. songwensis is distinct over L. songweellipticus, L. microovum and L. songweeovum by lacking characters defining the Meladomus morphotype.

Paleoecology.—The high morphological disparity associated with this taxon is possibly due to a combination of allometry and ecophenotypic plasticity. Presence of both allometry and ecophenotypic plasticity is known to occur within the ampullariids (see

Estebenet, 1998; Hayes et al., 2009a,b; Hayes et al., 2015). Lanistes songwensis is most comparable with the modern Lanistes nsendweensis, Lanistes neavei and the Miocene

Lanistes heynderycxi. Lanistes nsendweensis is found in fluvial settings (rocky portions below the falls in the Congo River near Stanleyille plus the forest affluent and swampy habitats near the river) (see Pilsbry and Bequaert, 1927, Brown and Berthold, 1990,

Brown, 1994); whereas Lanistes neavei inhabits seasonal pools (Brown, 1994). Lanistes heynderycxi is interpreted to occupy shallow lakes, swamps and slow flowing rivers (Van 98

Damme and Pickford, 1995). In the Songwe Member, fossils of Lanistes songwensis are found in lacustrine-fluvio-deltaic deposits (Nsungwe 1) and lacustrine (Nsungwe 2,

Nsungwe Gastropod Location) settings. However, a majority of fossils of this species are found in fluvial settings (TZ01, TZ01South, and TZP2). Based on its streamlined neritoid body shape, Lanistes songwensis is interpreted as capable of occupying lacustrine settings but better adapted to fluvial environments.

Occurrence. Nsungwe 1(lacustrine and fluvio-deltaic facies), Nsungwe Gastropod

Locality (lacustrine facies), Nsungwe 2 (lacustrine facies), TZP2 (fluvial facies), TZ01

(fluvial facies) and TZ01 south (fluvial facies), Songwe Member, Nsungwe Formation,

Rukwa Rift Basin. Tanzania (see Roberts et al., 2010). This locality is approximately 8°

56’ S latitude and 33° 12’ E longitude (Precise coordinates are on file at Ohio

University).

Figure 26. Comparable modern species to Lanistes songwensis A. Lanistes carinatus (ANSP 367298-6), arrow indicates the medial carination. B. Lanistes nsendweensis (ANSP131955-6); C. Lanistes neavei (ANSP 448402-4) Scale bar 10 mm.

99

Figure 27. Images of Lanistes heynderycxi (Holotype, RG 2518) from Van Damme and Pickford (1995). A Diagrammatic sketch; B. Apertural view; C. Side view. Shell length 17.5 mm, width 20.3 mm.

Table 14.

Morphological characteristics of Lanistes songwensis (Measurements are in mm, abbreviations: H. Total shell height; D. Total shell width; h. Aperture height; S. Spire height; W. Number of whorls; C. Carinae; Y. Carination present; N. Carination absent; Nsungwe G.L. Nsungwe Gastropod Locality; NA. No data; Sp. No. Specimen Number). *poorly preserved specimens not included in summary statistics Sp. No. Locality W H D h S C H/D h/H S/H

RRBP 9265B Nsungwe 2 2.9 11.7 12.3 8.7 3.0 N 0.95 0.74 0.26

(Holotype)

RRBP 9265A Nsungwe 2 3.7 18.3 20.5 12.8 5.4 N 0.89 0.70 0.30

(Paratype)

RRBP 9234 Nsungwe 2 2.5 8.0 8.5 5.7 2.5 N 0.94 0.71 0.31

(Paratype)

RRBP 5492B TZ01 2.3 5.5 6.3 4.2 1.3 N 0.87 0.76 0.24

(Paratype)

RRBP 5492A TZ01 2.4 7.1 7.3 5.0 2.0 N 0.97 0.70 0.28

(Paratype) 100

Table 14: continued

Sp. No. Locality W H D h S C H/D h/H S/H

RRBP 10002 TZ01 ~2.8 10.3 11.2 7.5 2.8 N 0.92 0.73 0.27

(Paratype)

RRBP Nsungwe1 ~2.6 9.2 11.4 7.3 1.9 Y 0.81 0.79 0.21

8571AB

(Paratype)

RRBP 4008 TZ01 4.1 24.0 25.9 16.5 7.5 N 0.93 0.69 0.31

(Paratype)

RRBP 8349B TZ01 2.5 7.3 9.0 5.1 2.1 Y 0.81 0.70 0.29

(Paratype) South

RRBP 7677A TZP2 NA 23.2 24.8 16.1 7.0 N 0.94 0.69 0.30

(Paratype)

RRBP 4455 TZ01 ~2.5 10.1 11.9 7.3 2.8 N 0.85 0.72 0.28

(Paratype)

RRBP Nsungwe ~3.3 16.7 17.2 11.0 5.8 N 0.97 0.66 0.35

11120G G.L

(Paratype)

RRBP 10053 TZ01 ~3.9 21.2 22.2 13.9 7.3 N 0.95 0.66 0.34

RRBP Nsungwe ~3.1 11.8 14.7 9.3 2.5 N 0.80 0.79 0.21

11120A G.L

RRBP 3052 TZ01 ~3.4 22.2 23.7 15.0 7.1 N 0.94 0.68 0.32 101

Table 14: continued

Sp. No. Locality W H D h S C H/D h/H S/H

RRBP Nsungwe ~2.9 18.2 20.6 12.3 5.9 N 0.88 0.68 0.32

11120B G.L

RRBP Nsungwe ~2.6 15.3 16.0 11.5 3.8 N 0.96 0.75 0.25

11120F G.L

RRBP Nsungwe ~2.5 16.6 15.4 11.0 3.6 N 1.08 0.66 0.22

11120J G.L

RRBP Nsungwe ~3.3 14.9 15.4 10.7 4.2 N 0.97 0.72 0.28

11120K G.L

RRBP 4199 TZ01 ~2.4 16.7 17.4 12.5 4.2 N 0.96 0.75 0.25

RRBP 5068A TZ01 ~3.1 10.0 12.1 6.9 3.0 Y 0.83 0.69 0.30

RRBP 5209 TZP2 ~2.8 17.3 20.9 12.9 4.4 N 0.83 0.75 0.25

RRBP 5282 TZP2 NA 27.5 30.5 18.0 9.4 N 0.90 0.65 0.34

RRBP 5435 TZ01 ~2.5 6.7 7.8 5.6 1.1 N 0.86 0.84 0.16

RRBP 5436 TZ01 south ~3.1 13.4 14.9 9.3 4.1 Y 0.90 0.69 0.31

RRBP 5540 TZP2 ~3.3 13.1 15.6 8.9 4.2 N 0.84 0.68 0.32

RRBP 5676 TZ01 ~2.2 6.1 6.4 4.7 1.4 N 0.95 0.77 0.23

RRBP 6125 TZ01 3+ 23.6 26.6 16.4 7.2 N 0.89 0.69 0.31

RRBP 6186 TZ01 south NA 10.5 11.8 8.6 1.9 Y 0.89 0.82 0.18

RRBP 7046 TZP2 ~3 19.5 23.6 12.0 7.5 N 0.83 0.62 0.38

RRBP 9066A TZ01 ~3 16.8 19.3 11.3 5.6 N 0.87 0.67 0.33 102

Table 14: continued

Sp. No. Locality W H D h S C H/D h/H S/H

RRBP 9475B TZ01 south ~2.8 11.0 12.5 7.3 3.7 N 0.88 0.66 0.34

RRBP 7111 TZP2 ~4.1 20.0 24.0 12.9 7.0 N 0.83 0.65 0.35

RRBP Nsungwe ~2.8 11.3 11.2 8.9 2.4 N 1.01 0.79 0.21

11120H G.L.

RRBP Nsungwe 1 ~3.6 24.4 27.0 15.8 8.5 N 0.90 0.65 0.35

8571AA*

RRBP 5574* TZ01 ~2.6 12.4 12.4 9.0 3.4 Y 1.00 0.73 0.27

RRBP TZ01 NA 17.6 21.8 NA NA Y 0.81 NA NA

9475A* South

RRBP 4475* TZP2 ~3.1 9.3 11.3 7.4 2.0 N 0.82 0.80 0.22

RRBP 5249* TZP2 NA 15.1 15.3 11.6 3.4 Y 0.99 0.77 0.23

Average 0.90 0.71 0.28

Standard 0.06 0.05 0.05

Deviation

103

CHAPTER 7. DISCUSSION

New Ampullariid Fauna from the Late Oligocene Nsungwe Formation

The ampullariid fauna of the late Oligocene deposits of Tanzania comprises six species, including five new species of Lanistes and one new species of Carnevalea. In addition to describing a new fauna, this study also records the earliest appearance of the high-spired Meladomus morphotype of Lanistes and the first appearance of Carnevalea outside of the Eocene Zalumah Formation of Oman.

These new species provide insights into patterns of and controls on morphological variation within both Lanistes and Carnevalea. The fossil record of Lanistes is dominated by depressed Lanistes sensu stricto morphotypes with the high-spired Meladomus morphotype forms first appearing as late as only eight million years ago in the form of the late Miocene Lanistes olukaensis (see Van Damme and Pickford, 1995). However, the

Nsungwe species Lanistes songweeovum, L. songweellipticus and L. microovum push back the first appearance of high-spired forms by 16 million years, to the late Oligocene. Pilsbry and Bequaert (1927) suggest a planorbid ancestor to Lanistes, which suggests that Lanistes sensu stricto morphotype may be the ancestral morphotype for the genus, which was followed by Meladomus-type and Leroya-type species later in the evolutionary history of the lineage. Since Lanistes from the Nsungwe Formation contains both Lanistes sensu stricto and Meladomus morphotypes but not Leroya forms, it is reasonable to hypothesize that Nsungwe Lanistes may represent an early diversification stage in the evolution of the genus, producing high-spired forms for the very first time. In addition, morphological variation in Carnevalea, which was previously restricted to the degree of protrusion of the 104 peripheral keel and the spire height (Neubert and Van Damme, 2012; Harzhauser et al.,

2016), is supplemented by the additional variation in the aperture in Carnevalea santiapillai.

Paleoecology of Nsungwe Ampullariids

Extant Lanistes species generally inhabit lentic and lotic systems with the majority able to occupy both environments (see Brown, 1994). However, several species like Lanistes nyassanus, Lanistes solidus and Lanistes nasutus occupy specific niches

(see Pilsbry and Bequaert, 1927; Louda and McKay, 1982; Louda et al., 1984; Berthold,

1990a, b; Brown, 1994). Their unique ecologies are often translated by their distinct morphologies. Thus, species adapted to each setting should exhibit distinct morphologies.

In general, fluvial gastropod species are characterized by streamlined shells adapted to minimize tow and drag of currents; whereas lacustrine forms are characterized by having a few or a combination of the following: shells with lower spires, robustly calcified shells, carinations or shouldered, whorls convex whorls, and inflated whorls (see Van

Damme and Pickford, 2003).

Localities within the Nsungwe Formation where the present gastropod specimens were collected consist of three main depositional environments: lacustrine, fluvial and fluvio-deltaic (Roberts et al., 2010). Overall, within the Nsungwe Formation, the fluvial settings are dominated by Lanistes songwensis; whereas Lanistes nsungwensis is the most common species in lacustrine environments (see Table 15).

105

Table 15.

Paleoenvironmental distribution of Nsungwe ampullariid species. Dominant ecology indicated by bolded letters. Species Fluvial (lotic) Lacustrine (lentic) Paludal

C. santiapillai X X

L. nsungwensis X

L. songwensis X X

L. songweellipticus X

L. microovum X X X

L. songweeovum X X

Lanistes songwensis and Lanistes songweellipticus represent the true fluviate species and are characterized by the expected morphology of streamlined shells.

Carnevalea santiapillai, which occurs within the lacustrine facies of Nsungwe 3, and

Lanistes nsungwensis , which is found in lacustrine layers at Nsungwe 2, Nsungwe 3 and

Bigwall (Nsungwe 2B), represent the true lacustrine (lentic) forms among the Nsungwe ampullariids. Both of these taxa possess the typical morphologies expected from a lacustrine morphotype (see Van Damme and Pickford, 2003).

Lanistes microovum and Lanistes songweeovum, which possess higher spires and more streamlined morphology than C. santiapillai and L. nsungwensis, also co-occur within the lacustrine facies. Morphologically, it is counterintuitive to a lacustrine facies, which suggests either transport of specimens away from their living environment or adaptation to a different environment, such a paludal or marshy habitat. Similar to their 106 extant analog, Lanistes ovum, L. microovum and L. songweeovum were likely capable of inhabiting lentic systems as well as a different microhabitat than the obligate lake forms.

Indirect evidence for this hypothesis can be inferred by considering habitat utilization of

Malawian “Lanistes ellipticus.” In Lake Malawi, high-spired ellipticus-like forms are known to occupy marshes (the paludal facies) around the lake (Berthold, 1990a, b;

Brown, 1994; Schultheiß et al., 2009). Thus, it is reasonable to suggest that Lanistes microovum and Lanistes songweeovum may also have occupied a similar vegetated area around the lacustrine settings of Nsungwe 2 and Nsungwe Gastropod Location (i.e., indicative of habitat partitioning). However, the reappearance of Lanistes microovum from the fluviate TZ01 locality (RRBP7445C) possibly represents a truly fluvially adapted species that was transported post-mortem as their streamlined shell more typical of gastropods within a lotic than a lentic system.

Ecophenotypic Variation within the Nsungwe Ampullariids

Modern Lanistes species exhibit a high degree of shell plasticity due to ecophenotypic effects. Together with allometric influences (which is also known amongst the ampullariids, see Estebenet, 1998), the intraspecific disparity has proven to be a major challenge in identifying distinct species based on conchological attributes alone. Similar challenges exist in distinguishing species in the fossil record. Additionally, some fossil species designations are based on shell ornamentation. Instances where shell ornamentation like carination, is poorly developed, poorly preserved or shared between different species, confounds species designation (see Harzhauser et al., 2016). 107

In general, freshwater snails show plastic responses to both abiotic and biotic cues, particularly, flow conditions, substrate and predation (Whelan et al., 2012).

Limitation in the availability of calcium carbonate in freshwater environments generally results in the production of subtle architectural modifications compared to the range of modifications exhibited by marine taxa (DeWitt et al., 2000). However, amongst

Nsungwe ampullariids, constraints for shell material would not have been a significant factor as carbonate volcanics within the region (see Roberts et al., 2010; 2012) would have produced adequate carbonates for shell metabolism. Predation and flow rate; however, may have had an effect on shell morphology of the Nsungwe ampullariids.

Considering the latter, channel deposits of Nsungwe Formation are generally interpreted as part of a meandering or anastomosing river system (Roberts et al., 2010). Both these systems, especially anastomosed rivers, have high habitat heterogeneity but comparatively low flow rates, so the ability of such a system to induce plasticity is a question. A comparative analysis on aperture sizes of Lanistes songwensis from lacustrine and fluvial deposits may provide insight in to this. However, only two lacustrine fossils that meet analytical criteria are available for comparison, so such an analysis cannot be conducted at the present time.

Predatory induced changes are, thus, the most likely ecophenotypic responses expected with the Nsungwe ampullariids. Potential predators of ampullariids described from Songwe Member include frogs (ex. Ptychadenidae); crocodiles, fishes (ex.

Ceratodontidae, Actinopterygii), birds and crabs (ex. Tanzanonautes tuerkayi) (Feldmann et al., 2007; Stevens et al., 2008; Roberts et al., 2010; 2016 Blackburn et al., 2015). The 108 prominent medial shell carination observed in some Nsungwe Lanistes species (i.e.,

Lanistes songwensis and L. nsungwensis), would have functioned to increase shell strength against crushing predation and thus could have been function of predator induced plasticity (Berthold, 1990b). However, there is debate on whether carination is purely ecophenotypic or if there is a genetic basis. Whelan et al. (2012) demonstrated that shell carination in Leptoxis ampla Anthony, 1855 was genetically controlled but suggested that data was lacking for other taxa. The lack of a clear pattern of carinated shells between Nsungwe localities confounds inferring the genetic or plastic nature of this character for Songwe species. However, considering the ability of ampullariids in general to produce plastic shells, the carination of Nsungwe Lanistes songwensis and L. nsungwensis is interpreted as a plastic response. Similar ornamentation in related species is known to have an anti-predatory function (see Urabe, 2000; Minton et al., 2008). It is, therefore, reasonable to suggest that shell carinae served a similar function where crushing forces exerted by durophagus predators are spread throughout the shell reducing damage to the shell (see Berthold, 1990b; Whelan et al., 2012). Interestingly, carination in Lanistes songwensis and L. nsungwensis is most often observed in smaller shells. In fact, the largest carinated shell (RRBP 5249A) is only 15.1 mm high and 15.3 mm wide, respectively. This size-based appearance in shell carinae may suggest that this is a form of anti-predatory response shown by juvenile snails and once they reach a size refugia, the requirement of such traits are insignificant. This hypothesis is further supported by

Hayes et al. (2015) who reported very few predators can prey on Asian ampullariids greater than 20 mm in size. 109

In addition to plastic responses, heritable adaptive traits evolved in Lanistes to minimize predation (Louda and McKay, 1982; Louda et al., 1984; Berthold, 1990a, b). In

Malawi, the thick shelled Lanistes solidus and Lanistes nyassanus are nocturnal and burrow during daytime providing protection from cichlids, which are diurnal visual hunters (Louda and McKay 1982; Louda et al., 1984; Berthold, 1990a,b; Brown, 1994).

Lanistes nyassanus also exhibits differential growth rates between juveniles and adults.

Juvenile snails are vulnerable to predation, thus the juvenile phase is characterized by rapid growth but the adult phase continues at a slower pace producing thicker shells

(Louda and McKay, 1982; Berthold, 1990a, b). The role of crab as predators offers an interesting question relating predator effectiveness versus snail handedness. It has been shown by Dietl and Hendricks (2006) that right handed crabs (i.e., larger right chelae adapted for crushing or peeling see Shigemiya, 2003) are less effective as predators on sinistral snails as opposed to dextral forms of the same species (see Vermeij, 2015).

Tanzanian crab material described from the Nsungwe Formation represents a single species, Tanzanonautes tuerkayi which exhibits heterochely, with the right claw being more robust than the left (see Feldmann et al., 2007). Thus, it is doubtful whether these right handed crabs were able to influence the morphology or ecology of either Lanistes or

Carnevalea, which are both sinistral.

Paleoenvironment of the Late Oligocene Rukwa Rift Basin

Overall, the Songwe Member is characterized as a quiet water lake and wetland succession with fluvio-deltaic, fluvial (meandering or anastomosed) and lacustrine habitats (Roberts et al., 2010; 2012). Based on preservation of well-laminated claystones, 110 abundant aquatic fauna, and geochemical data, Roberts et al. (2010) interpret the Songwe facies as recording a mosaic of environments with perennially available surface water within a regionally semi-arid climate. One partially preserved specimen of Lanistes which resemble Lanistes songwensis from TZ01 (RRBP 5568) was preserved in a burrow within a rooted mudstone (Fig. 28). This occurrence suggests that the gastropods may have burrowed during drier periods as some of the fluvial localities (such as TZ01) experienced seasonal desiccation. Furthermore, the presence of large concentrations of essentially monotypic achitinid land snails in certain localities (ex. TZ01, TZ01 South,

Nsungwe 1) may also suggest the presence of a periodic wet and dry seasons (see

Neubert and Van Damme, 2012).

111

Figure 28. Fossil Lanistes cf. songwensis (RRBP 5568) preserved in an aestivating burrow. Dashed lines indicate potential borders of the burrow. Reduced zones appear white in the light brown matrix. Fossil snail indicated by the medial arrow. Scale bar 10 mm.

Generally, freshwater snails have a poor preservation potential compared with their marine counterparts (Strong et al., 2008). However, diverse and abundant preservation of fossil gastropods in the Nsungwe Formation may be a function of the active carbonatite volcanism that occurred during the rifting of the basin. Decaying plant matter results in swampy environments, like those that characterize the Songwe Member, are highly acidic and corrosive to the aragonite of gastropod shells (Neubert and Van

Damme, 2012). Thus, these environments often provide little opportunity for carbonate shells to preserve. However, the active carbonatite volcanoes in the Rukwa Rift Basin 112 may have produced adequate carbonates that essentially neutralized the acidity and facilitated preservation of fossils in the Songwe Member.

Evidence for Adaptive Radiation of Nsungwe Lanistes

Schluter (2000) describes four features required for recognition of an adaptive radiation: common ancestry, phenotype-environment correlation, trait utility and rapid speciation. All four features are recognized within the Nsungwe ampullariid fauna. The initial deposits of Nsungwe1, Nsungwe Gastropod Location and Nsungwe 2 contains fossils of Lanistes songwensis, which can be considered as the ancestral population of

Lanistes within the basin. The tectonic induced transition from a lacustrine-fluvio-deltaic to a true lacustrine environment in the Nsungwe River Section (see Fig. 2) generated novel ecological opportunities for the ancestral population to diversify. The divergence produced a wide-bodied, low-spired true lacustrine form, Lanistes nsungwensis. The high expansion rate of whorls, which produced this morphology, was possibly induced by durophagus predatory cues in the lacustrine setting where the taxon needed to increase its size rapidly to achieve a size refugium. Fluvial adapted Lanistes songwensis and high- spired Lanistes microovum and Lanistes songweeovum co-occur within the lacustrine facies of Nsungwe Gastropod Location and Nsungwe 2. However, no such high-spired forms were found within Bigwall (Nsungwe 2B) or the subsequent Nsungwe 3 deposit, which includes only true lacustrine forms. This indicates a shift in morphologies as selective regimes keep the population of fluvial forms at a very low density.

The Songwe River Section (see Fig. 2) preserves TZP-2, TZ01 and TZ01 South deposits. These fluvial deposits preserves an abundance of the ancestral Lanistes 113 songwensis, which dominates the gastropod assemblage collected from the three sites mentioned above. Also a single occurrence of Lanistes microovum and a new species of high-spired Lanistes songweellipticus also occurs. All three species have morphologies typical of fluviate snails (see Van Damme and Pickford, 2003). No true lacustrine species were recovered from these sites.

The limited number of gastropod fossils in localities like Nsungwe 1 and Bigwall

(Nsungwe 2B) and the lack of direct predator-prey information on lacustrine settings provides a considerable constraint on interpretations. However, with the capacity of

Lanistes to diversify in response to the changes in the abiotic and biotic settings (ex. diversification in Malawi, and Albertine Rift), the hypotheses generated in the present study provides a reasonable evolutionary framework that can be built upon with further collections and resolution of paleoenvionmental data.

Closing the African Gap

Nsungwe ampullariids provide information about a temporal interval during which paleontological data about the faunas of continental sub-equatorial Africa are scarce (Roberts et al., 2010). This paucity, referred to as the “African Gap” is a combined result of masking vegetative cover, inaccessibility, limited economic resources and poor preservation of fossils (Roberts et al., 2010). This scarcity of data has hampered comparative studies aimed at understanding biological and geological relationships between regions of Africa and Gondwana in general (Roberts et al., 2010). However, fossils from the Songwe Member of the Rukwa Rift Basin provide excellent opportunities to fill this gap in paleobiological knowledge. Notably, the Songwe Member is the only 114 known Oligocene terrestrial/freshwater fossiliferous deposit from subequatorial Africa, and thus provide much needed information on African endemism prior to the faunal exchange between Africa, Arabia and Eurasia (Roberts et al., 2012).

These fossils provide valuable insights on the taxonomic composition of the

Paleogene freshwater molluscs of Africa. Prior to this study, the Paleogene composition of African Lanistes was limited to Lanistes grabhami from Sudan and Lanistes antiquus,

Lanistes bartonianus, Lanistes irregularis, Lanistes sandbergeri, Lanistes sodaensis and

Lanistes abbassiensis from Egypt. Thus, the addition of six new species greatly expands on the poorly known ampullariid fauna from this period of Africa. From an evolutionary standpoint, this study provides a robust time frame and geographic position for the evolution of the first high-spired Lanistes and also provides potential factors that could have lead to its diversification. Biogeographically, several ampullariids described in the present study show faunistic relationships with other ampullariids described from the

Paleogene Afro-Arabia. The genus Carnevalea was formally known only from the

Eocene deposits of Oman (Neubert and Van Damme, 2012; Harzhauser et al., 2016).

However, Carnevalea santiapillai described in the present study indicates that species of this genus might have been more commonly distributed than a point endemic as suggested by the previously explored fossil record. Further, Lanistes nsungwensis, which is comparable with Lanistes grabhami, indicates faunistic relationships between the late

Oligocene Nsungwe fauna and the Eocene Sudanese Fauna. Also, Lanistes songwensis, which resemble Lanistes heynderycxi suggests faunistic affinities between rift fauna of the Western Branch of the East African Rift System. 115

CHAPTER 8: CONCLUSIONS

In this study of the freshwater ampullariids from the late Oligocene Nsungwe

Formation, six species new to science are identified. The ampullariids described herein help to fill a significant gap in the continental African fossil record. The described taxa include five species of Lanistes: L. microovum, L. songwensis, L. songweellipticus, L. nsungwensis and L. songweeovum and a new species of the genus Carnevalea, C. santiapillai. Lanistes songwensis and Lanistes nsungwensis represents the depressed

Lanistes sensu stricto morphotype and Lanistes songweellipticus, Lanistes songweeovum and Lanistes microovum represents the high-spired Meladomus morphotype.

Morphometric analyses were performed on log-transformed linear data (total shell height, total shell width, aperture height and spire height) on modern ampullariid specimens, Nsungwe fossil material, combined Nsungwe fossils and other Cenozoic ampullariid fossils (Lanistes carinatus and Lanistes ellipticus) and for all modern and fossil ampullariid specimens combined. Two sets of morphometric analyses were performed: Principle Component Analysis and Cluster Analysis. PCA and cluster analysis performed on modern specimens indicate the presence of two morphotypes; the high-spired and depressed forms. Overlap between and among morphotypes are resolvable using morphological traits not encoded within the linear measurements. These quantitative analyses provided justification of using both analytical techniques as a precursor for taxonomic/morphotype identification and visualizing morphospace utilization. PCA and cluster analyses performed on Nsungwe fossils indicates the presence of the two morphotypes. Additionally, the divergent morphologies of Lanistes 116 microovum and Carnevalea santiapillai, places them within unique regions in morphospace. Morphometric analyses on combined fossil data indicates the close affinity of Lanistes songweellipticus with that of the Plio-Pleistocene fossils of Lanistes ellipticus. PCA performed on combined fossil and modern data suggested the morphological distinction of Carnevalea santiapillai and Lanistes microovum. However,

Lanistes microovum clustered consistently with depressed morphotypes among all dendograms suggesting caution of over interpretation based solely on morphometric data.

Distinguishing Lanistes songwensis over Lanistes nsungwensis, which is based on the higher whorl expansion rate of the latter, also reiterates the importance of using combined morphological and morphometric criteria in distinguishing taxonomic identities and in morphotype designation.

Paleoecological interpretations produced by combining ecologies of related extant taxa and available sedimentological data suggests the presence of two fluvial and two lacustrine adapted species. Carnevalea santiapillai is inferred to be a paludal to lacustrine adapted species; whereas Lanistes nsungwensis, is inferred to be a true lacustrine form.

Lanistes songwensis, which resembles the modern Lanistes nsweendensis, Lanistes neavei and the Miocene Lanistes heynderycxi, is interpreted as a true fluvial adapted species. Lanistes songweellipticus represents a second true fluviate species. Lanistes microovum and Lanistes songweeovum, which occur within lacustrine facies and resemble the modern Lanistes ovum, were probably capable of inhabiting both fluvial and lacustrine settings. 117

Overall, the Songwe Member is interpreted as a quiet water lake and wetland succession with fluvio-deltaic, fluvial (meandering or anastomosed) and lacustrine habitats within a semi-arid climate. The presence of a specimen of Lanistes cf. songwensis preserved in a burrow within a rooted mudstone indicates periods of desiccation where the snails may have responded by aestivating. Additionally, the presence of wet-dry periods are also indicated by the large aggregations of almost monotypic land snails in selected localities.

The tectonic induced transitions of the late Oligocene Nsungwe Formation also provides insight on to the adaptive radiation of the ampullariid lineage within the basin.

Transition to a lacustrine environment in the Nsungwe River Section resulted in the divergence of the ancestral Lanistes songwensis to a wide-bodied, low-spired true lacustrine form, Lanistes nsungwensis. The high whorl expansion rate was possibly triggered by durophagus predators in the lacustrine setting, which required Lanistes nsungwensis to increase its size rapidly to achieve a size refugium. Overall, the fluvial paleoenvironment is dominated by Lanistes songwensis whereas the lacustrine settings are dominated by Lanistes nsungwensis.

Apart from its potential role in inducing the evolutionary radiation of this gastropod clade, active carbonate volcanism possibly resulted in the excellent preservation of freshwater gastropod fauna within the basin. The carbonates generated potentially neutralized the acidity commonly associated with swampy environment.

This study present valuable insight into the taxonomy, evolution and biogeography of the Paleogene freshwater gastropod fauna of Africa. The new species 118 greatly expands the existing record of African ampullariids and provides additional information on morphological variations within both Lanistes and Carnevalea. The presence of high-spired Lanistes expands the record of the Meladomus morphotype by 16 million years and also provides potential factors that may have led to its evolution. The diversification of Lanistes within the basin provides an evolutionary framework to test for an adaptive evolutionary radiation induced by tectonically generated ecological opportunity.

In a biogeographic context, this new material suggests a more widespread distribution for the genus Carnevalea. Furthermore, morphological similarities among taxa suggest faunal affinities between the late Oligocene Nsungwe Formation, and the

Miocene deposits of Albertine Rift and Eocene deposits of Hudi Chert Formation.

119

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APPENDIX A: ALL NSUNGWE FOSSILS EXAMINED

Sp. No Locality No. of specimens RRBP NA NA 1

RRBP NA NA 1

RRBP 7053 NA 1

RRBP 7116 NA 1

RRBP 12346 Bigwall (Nsungwe 2B) 1

RRBP 12533 Bigwall (Nsungwe 2B) 1

RRBP 13311A Bigwall (Nsungwe 2B) 1

RRBP 13311B Bigwall (Nsungwe 2B) 1

RRBP 11167 Nsungwe 2 1

RRBP 11524B Nsungwe 2 1

RRBP 12331B Nsungwe 2 1

RRBP 13212B Nsungwe 2 1

RRBP 7462B Nsungwe 2 1

RRBP 7482 Nsungwe 2 1

RRBP 7511 Nsungwe 2 1

RRBP 7522 Nsungwe 2 1

RRBP 7574 Nsungwe 2 2

RRBP 7616A Nsungwe 2 1

RRBP 7616B Nsungwe 2 1

RRBP 8097 Nsungwe 2 1 136

Sp. No Locality No. of specimens

RRBP 8129 Nsungwe 2 1

RRBP 8161 Nsungwe 2 14

RRBP 8194 Nsungwe 2 1

RRBP 8224 Nsungwe 2 27

RRBP 8258 Nsungwe 2 1

RRBP 8282 Nsungwe 2 1

RRBP 8317 Nsungwe 2 6

RRBP 9015 Nsungwe 2 1

RRBP 9019 Nsungwe 2 1

RRBP 9097 Nsungwe 2 1

RRBP 9160 Nsungwe 2 1

RRBP 9163 A Nsungwe 2 1

RRBP 9196A Nsungwe 2 1

RRBP 9196B Nsungwe 2 1

RRBP 9228 Nsungwe 2 1

RRBP 9234 Nsungwe 2 1

RRBP 9235 Nsungwe 2 2

RRBP 9265A Nsungwe 2 1

RRBP 9265B Nsungwe 2 1

RRBP 9440 Nsungwe 2 1

RRBP 12112 Nsungwe 2 1 137

Sp. No Locality No. of specimens

RRBP 12262 Nsungwe 2 1

RRBP 12319 Nsungwe 3 3

RRBP 16081 Nsungwe 3 1

RRBP 16151C Nsungwe 3 1

RRBP 12156 Nsungwe 2 1

RRBP 16111 Nsungwe 3 1

RRBP 11120B Nsungwe G.P. 1

RRBP 11120C Nsungwe G.P. 1

RRBP 11120F Nsungwe G.P. 1

RRBP 11120G Nsungwe G.P. 1

RRBP 11120J Nsungwe G.P. 1

RRBP 11120K Nsungwe G.P. 1

RRBP 11122 Nsungwe G.P. 1

RRBP 8571AA Nsungwe1 1

RRBP 8571AB Nsungwe1 1

RRBP 10002 TZ01 1

RRBP 10053 TZ01 1

RRBP 11007 TZ01 1

RRBP 3012A TZ01 1

RRBP 3012B TZ01 1

RRBP 3114 TZ01 1 138

Sp. No Locality No. of specimens

RRBP 4004 TZ01 1

RRBP 4008 TZ01 1

RRBP 4024 TZ01 1

RRBP 4075 TZ01 1

RRBP 4182 TZ01 1

RRBP 4199 TZ01 1

RRBP 4206 TZ01 1

RRBP 4207 TZ01 1

RRBP 4455 TZ01 1

RRBP 5068A TZ01 1

RRBP 5345 TZ01 1

RRBP 5435 TZ01 1

RRBP 5492A TZ01 1

RRBP 5492B TZ01 1

RRBP 5568 TZ01 1

RRBP 5574 TZ01 1

RRBP 5672 TZ01 1

RRBP 5676 TZ01 1

RRBP 6125 TZ01 1

RRBP 7442A TZ01 1

RRBP 7442B TZ01 1 139

Sp. No Locality No. of specimens

RRBP 7445C TZ01 1

RRBP 9010 TZ01 1

RRBP 9066A TZ01 1

RRBP 11393 TZ01 south 1

RRBP 5068C TZ01 south 1

RRBP 5068D TZ01 south 1

RRBP 5372 TZ01 south 1

RRBP 5436 TZ01 south 1

RRBP 6170 TZ01 south 1

RRBP 6172A TZ01 south 1

RRBP 6172B TZ01 south 1

RRBP 6186 TZ01 south 1

RRBP 7029 TZ01 south 1

RRBP 7150 TZ01 south 1

RRBP 7215 TZ01 south 1

RRBP 7267 TZ01 south 1

RRBP 7671 TZ01 south 1

RRBP 8284 TZ01 south 1

RRBP 8349A TZ01 south 1

RRBP 8349B TZ01 south 1

RRBP 8523 TZ01 south 1 140

Sp. No Locality No. of specimens

RRBP 9475B TZ01 south 1

RRBP 4264 TZP2 1

RRBP 4282 TZP2 1

RRBP 4387 TZP2 1

RRBP 4472 TZP2 1

RRBP 4475 TZP2 1

RRBP 5209 TZP2 1

RRBP 5249A TZP2 1

RRBP 5249B TZP2 1

RRBP 5282 TZP2 1

RRBP 5540 TZP2 1

RRBP 5558 TZP2 1

RRBP 5586 TZP2 1

RRBP 6027 TZP2 1

RRBP 6034 TZP2 1

RRBP 6134B TZP2 1

RRBP 6138 TZP2 1

RRBP 7046 TZP2 1

RRBP 5217 TZP2 1

RRBP 7085 TZP2 1

RRBP 7090 TZP2 1 141

Sp. No Locality No. of specimens

RRBP 7111 TZP2 1

RRBP 7677A TZP2 1

(Abbreviations. Nsungwe G.L. Nsungwe Gastropod Locality; NA. Not available; Sp. No. Specimen number).

142

APPENDIX B: MODERN AND FOSSIL MUSEUM SPECIMENS EXAMINED

Specimen No. Museum Species name Geologic age

14091 UCMP L. carinatus Miocene

14092 UCMP L. carinatus Miocene

154224 UCMP L. ellipticus Plio-Pleistocene

154225 UCMP L. ellipticus Plio-Pleistocene

154226 UCMP L. ellipticus Plio-Pleistocene

154227 UCMP L. ellipticus Plio-Pleistocene

154228 UCMP L. ellipticus Plio-Pleistocene

146190-1 ANSP L. ovum adansoni Recent

146190-2 ANSP L. ovum adansoni Recent

146190-3 ANSP L. ovum adansoni Recent

146190-4 ANSP L. ovum adansoni Recent

146190-5 ANSP L. ovum adansoni Recent

146190-6 ANSP L. ovum adansoni Recent

146190-7 ANSP L. ovum adansoni Recent

146190-8 ANSP L. ovum adansoni Recent

146190-9 ANSP L. ovum adansoni Recent

146190-11 ANSP L. ovum adansoni Recent

146190-12 ANSP L. ovum adansoni Recent

146190-13 ANSP L. ovum adansoni Recent

133874-1 ANSP L. bicarinatus Recent 143

Specimen No. Museum Species name Geologic age

438051-1 ANSP L. carinatus Recent

367298-1 ANSP L. carinatus Recent

367298-2 ANSP L. carinatus Recent

367298-3 ANSP L. carinatus Recent

367298-4 ANSP L. carinatus Recent

367298-6 ANSP L. carinatus Recent

367298-7 ANSP L. carinatus Recent

367298-8 ANSP L. carinatus Recent

367298-9 ANSP L. carinatus Recent

367298-10 ANSP L. carinatus Recent

367298-11 ANSP L. carinatus Recent

367298-12 ANSP L. carinatus Recent

367298-14 ANSP L. carinatus Recent

131953-1 ANSP L. congicus Recent

156766-1 ANSP L. ellipticus Recent

156766-2 ANSP L. ellipticus Recent

156766-3 ANSP L. ellipticus Recent

156766-4 ANSP L. ellipticus Recent

156766-5 ANSP L. ellipticus Recent

156766-6 ANSP L. ellipticus Recent

448411-1 ANSP L. ovum elongata Recent 144

Specimen No. Museum Species name Geologic age

448411-2 ANSP L. ovum elongata Recent

63044-1 ANSP L. grasseti Recent

251433-1 ANSP L. graueri Recent

251433-2 ANSP L. graueri Recent

251433-3 ANSP L. graueri Recent

251433-4 ANSP L. graueri Recent

251433-5 ANSP L. graueri Recent

221671-1 ANSP L. intortus Recent

221671-2 ANSP L. intortus Recent

156569-1 ANSP L. libycus Recent

448402-1 ANSP L. neavei Recent

448402-2 ANSP L. neavei Recent

448402-3 ANSP L. neavei Recent

448402-4 ANSP L. neavei Recent

131955-1 ANSP L. nsendweensis Recent

131955-2 ANSP L. nsendweensis Recent

131955-3 ANSP L. nsendweensis Recent

131955-4 ANSP L. nsendweensis Recent

131955-5 ANSP L. nsendweensis Recent

131955-6 ANSP L. nsendweensis Recent

131955-7 ANSP L. nsendweensis Recent 145

Specimen No. Museum Species name Geologic age

131955-8 ANSP L. nsendweensis Recent

131955-9 ANSP L. nsendweensis Recent

131955-10 ANSP L. nsendweensis Recent

131955-11 ANSP L. nsendweensis Recent

131955-12 ANSP L. nsendweensis Recent

131955-13 ANSP L. nsendweensis Recent

131955-14 ANSP L. nsendweensis Recent

131955-15 ANSP L. nsendweensis Recent

131955-16 ANSP L. nsendweensis Recent

131955-17 ANSP L. nsendweensis Recent

131946-1 ANSP L. ovum Recent

176674-1 ANSP L. ovum Recent

176674-2 ANSP L. ovum Recent

176674-3 ANSP L. ovum Recent

120161-1 ANSP L. purpureus Recent

217293-1 ANSP L. sinistrosus Recent

217293-2 ANSP L. sinistrosus Recent

439028-1 ANSP L. solidus Recent

439028-2 ANSP L. solidus Recent

120397-1 ANSP L. varicus Recent

(Abbreviations. UCMP. University of California Museum of Paleontology; ANSP. Academy of Natural Sciences, Philadelphia) 146

APPENDIX C: FOSSIL SPECIMENS INCLUDED IN MORPHOMETRIC ANALYSES

Specimen Location Species. W H D h S

Number

RRBP Nsungwe 3 Carnevalea ~2.6 15.1 27.0 13.4 1.7

16151C santiapillai

RRBP Nsungwe 2 Lanistes ~2.7 10.2 9.6 6.6 3.5

9196 microovum

RRBP Nsungwe 2 Lanistes ~2.6 11.7 11.8 7.4 4.4

11167 microovum

RRBP Nsungwe 2 Lanistes 2.9 11.7 12.3 8.7 3.0

9265B songwensis

RRBP Nsungwe 2 Lanistes 3.7 18.3 20.5 12.8 5.4

9265A songwensis

RRBP Nsungwe G. L. Lanistes ~2.8 11.3 11.2 8.9 2.4

11120H songwensis

RRBP Nsungwe G. L. Lanistes ~3.1 11.8 14.7 9.3 2.5

11120A songwensis

RRBP Nsungwe G. L. Lanistes ~2.6 15.3 16.0 11.5 3.8

11120F songwensis

RRBP Nsungwe G. L. Lanistes ~3.3 14.9 15.4 10.7 4.2

11120K songwensis 147

Specimen Location Species. W H D h S

Number

RRBP Nsungwe G. L. Lanistes ~2.5 16.6 15.4 11.0 3.6

11120J songwensis

RRBP Nsungwe G. L. Lanistes ~3.3 16.7 17.2 11.0 5.8

11120G songwensis

RRBP Nsungwe G. L. Lanistes ~2.9 18.2 20.6 12.3 5.9

11120B songwensis

RRBP TZ01 Lanistes ~3.1 10.0 12.1 6.9 3.0

5068A songwensis

RRBP TZ01 Lanistes ~2.5 10.1 11.9 7.3 2.8

4455 songwensis

RRBP TZ01 Lanistes ~2.8 10.3 11.2 7.5 2.8

10002 songwensis

RRBP TZ01 Lanistes ~2.4 16.7 17.4 12.5 4.2

4199 songwensis

RRBP TZ01 Lanistes ~3.0 16.8 19.3 11.3 5.6

9066A songwensis

RRBP TZ01 Lanistes ~3.9 21.2 22.2 13.9 7.3

10053 songwensis

RRBP TZ01 Lanistes ~3.4 22.2 23.7 15.0 7.1

3052 songwensis 148

Specimen Location Species. W H D h S

Number

RRBP TZ01 Lanistes 3+ 23.6 26.6 16.4 7.2

6125 songwensis

RRBP TZ01 Lanistes ~4.1 24.0 25.9 16.5 7.5

4008 songwensis

RRBP TZ01 south Lanistes NA 10.5 11.8 8.6 1.9

6186 songwensis

RRBP TZ01 south Lanistes ~2.8 11.0 12.5 7.3 3.7

9475B songwensis

RRBP TZ01 south Lanistes ~3.1 13.4 14.9 9.3 4.1

5436 songwensis

RRBP TZP2 Lanistes ~3.3 13.1 15.6 8.9 4.2

5540 songwensis

RRBP TZP2 Lanistes ~2.8 17.3 20.9 12.9 4.4

5209 songwensis

RRBP TZP2 Lanistes ~3.0 19.5 23.6 12.0 7.5

7046 songwensis

RRBP TZP2 Lanistes ~4.1 20.0 24.0 12.9 7.0

7111 songwensis

RRBP TZP2 Lanistes NA 27.5 30.5 18.0 9.4

5282 songwensis 149

Specimen Location Species. W H D h S

Number

RRBP TZP2 Lanistes NA 23.2 24.8 16.1 7.0

7677A songwensis

RRBP TZ01 south Lanistes ~4.8 35.3 31.4 22.1 13.1

8284 songweellipticus

RRBP Bigwall Lanistes ~2.1 11.5 14.6 8.5 3.0

12346 (Nsungwe 2B) nsungwensis

RRBP Bigwall Lanistes ~2.8 13.8 18.1 9.8 4.0

13311B (Nsungwe 2B) nsungwensis

RRBP Nsungwe 2 Lanistes NA 19.8 27.2 12.4 7.3

9515 nsungwensis

RRBP Nsungwe 3 Lanistes ~2.2 12.6 14.4 9.8 2.8

16081 nsungwensis

RRBP Nsungwe G. L. Lanistes ~3.7 25.5 21.9 14.1 11.4

11222 songweeovum

(Abbreviations. W. number of whorls; H. Total shell height; D. Total shell width; h. aperture height; S. Spire height; Nsungwe G.L. Nsungwe Gastropod Locality; NA. Not available; all measurements are in mm). 150

APPENDIX D: MODERN SPECIMENS INCLUDED IN MORPHOMETRIC

ANALYSES

Sp. No. Species H D h S S/H h/H H/D 133874-1 L. bicarinatus 38.4 37.8 25.7 12.6 0.33 0.67 1.02

438051-1 L. carinatus 24.3 32.1 17.7 6.6 0.27 0.73 0.76

367298-1 L. carinatus 31.5 42.6 25.3 6.2 0.20 0.80 0.74

367298- L. carinatus 19.7 29.0 14.4 5.3 0.27 0.73 0.68

10

367298- L. carinatus 23.6 29.8 16.6 7.1 0.30 0.70 0.79

11

367298- L. carinatus 24.4 31.1 18.1 6.4 0.26 0.74 0.78

12

367298- L. carinatus 24.1 32.1 17.7 6.4 0.27 0.73 0.75

14

367298-2 L. carinatus 26.4 35.7 23.3 3.2 0.12 0.88 0.74

367298-3 L. carinatus 25.4 32.9 19.3 6.1 0.24 0.76 0.77

367298-4 L. carinatus 24.7 33.3 19.2 5.5 0.22 0.78 0.74

367298-6 L. carinatus 25.6 32.5 20.5 5.1 0.20 0.80 0.79

367298-7 L. carinatus 19.9 25.6 15.3 4.6 0.23 0.77 0.78

367298-8 L. carinatus 20.0 25.2 14.1 5.8 0.29 0.71 0.79

367298-9 L. carinatus 19.4 26.0 14.7 4.7 0.24 0.76 0.75

151

Sp. No. Species H D h S S/H h/H H/D

Average 0.24 0.76 0.76

Std. Dev 0.05 0.05 0.03

131953-1 L. congicus 19.8 21.0 13.9 5.9 0.30 0.70 0.94

156766-1 L. ellipticus 50.9 41.7 33.2 17.7 0.35 0.65 1.22

156766-2 L. ellipticus 54.7 47.0 36.9 17.8 0.33 0.67 1.16

156766-3 L. ellipticus 45.9 39.2 28.8 17.1 0.37 0.63 1.17

156766-4 L. ellipticus 49.1 40.0 28.2 20.9 0.43 0.57 1.23

156766-5 L. ellipticus 52.9 41.4 31.7 21.2 0.40 0.60 1.28

156766-6 L. ellipticus 46.1 39.2 31.7 16.1 0.35 0.69 1.18

Average 0.37 0.64 1.21

Std. Dev 0.04 0.04 0.04

63044-1 L. grasseti 25.4 22.7 14.4 10.9 0.43 0.57 1.12

251433-1 L. graueri 21.2 21.9 14.9 6.3 0.30 0.70 0.97

251433-2 L. graueri 24.6 25.0 17.1 7.5 0.30 0.70 0.98

251433-3 L. graueri 18.5 17.7 13.7 4.9 0.26 0.74 1.05

251433-4 L. graueri 17.0 17.8 12.5 4.6 0.27 0.74 0.96

251433-5 L. graueri 15.8 17.1 11.6 4.2 0.27 0.73 0.92

Average 0.28 0.72 0.98

Std. Dev 0.02 0.02 0.04 152

Sp. No. Species H D h S S/H h/H H/D

221671-1 L. intortus 31.4 28.2 21.0 10.3 0.33 0.67 1.11

221671-2 L. intortus 32.9 27.5 21.4 11.5 0.35 0.65 1.20

Average 0.34 0.66 1.15

Std. Dev 0.02 0.01 0.06

156569-1 L. libycus 29.4 27.0 20.3 9.0 0.31 0.69 1.09

448402-1 L. neavei 16.0 16.6 12.0 4.0 0.25 0.75 0.96

448402-2 L. neavei 15.6 15.9 11.3 4.3 0.28 0.72 0.98

448402-3 L. neavei 11.2 11.9 8.1 3.2 0.29 0.72 0.94

448402-4 L. neavei 14.2 14.5 10.0 4.1 0.29 0.70 0.98

Average 0.28 0.73 0.97

Std. Dev 0.02 0.02 0.02

131955-1 L. nsendweensis 21.0 20.4 14.2 6.7 0.32 0.68 1.03

131955- L. nsendweensis 13.8 13.4 10.2 3.7 0.27 0.74 1.03

10

131955- L. nsendweensis 15.2 14.9 10.5 4.7 0.31 0.69 1.02

11

131955- L. nsendweensis 14.3 14.4 10.6 3.7 0.26 0.74 0.99

12

131955- L. nsendweensis 10.1 10.0 7.6 2.5 0.25 0.75 1.01

13 153

Sp. No. Species H D h S S/H h/H H/D

131955-2 L. nsendweensis 16.3 15.8 12.0 4.3 0.26 0.74 1.03

131955-3 L. nsendweensis 17.2 16.8 12.4 4.9 0.28 0.72 1.02

131955-4 L. nsendweensis 22.4 24.1 15.5 6.8 0.30 0.69 0.93

131955-5 L. nsendweensis 26.4 27.0 16.8 9.6 0.36 0.64 0.98

131955-7 L. nsendweensis 18.6 21.1 13.6 5.0 0.27 0.73 0.88

131955-8 L. nsendweensis 19.0 18.3 12.9 6.1 0.32 0.68 1.04

131955-9 L. nsendweensis 16.8 16.2 12.2 4.6 0.27 0.73 1.04

131955-6 L. nsendweensis 28.4 27.2 18.1 10.3 0.36 0.64 1.04

131955- L. nsendweensis 9.4 9.1 7.2 2.2 0.24 0.76 1.04

14*

131955- L. nsendweensis 7.7 7.7 5.9 1.8 0.23 0.76 1.00

15*

131955- L. nsendweensis 8.3 8.0 5.8 2.5 0.30 0.70 1.03

16*

131955- L. nsendweensis 7.1 7.2 5.6 1.5 0.21 0.79 0.99

17*

Average 0.28 0.72 1.01

Std. Dev 0.04 0.04 0.04

131946-1 L. ovum 38.4 20.6 22.8 15.5 0.40 0.59 1.86

176674-1 L. ovum 47.9 33.6 26.6 21.3 0.44 0.56 1.43

176674-2 L. ovum 44.7 33.4 26.1 18.6 0.42 0.58 1.34 154

Sp. No. Species H D h S S/H h/H H/D

176674-3 L. ovum 56.6 37.6 28.3 28.3 0.50 0.50 1.51

Average 0.44 0.56 1.53

Std. Dev 0.04 0.04 0.23

146190-1 L. ovum 26.2 21.7 16.3 9.8 0.37 0.62 1.21

adansoni

146190-2 L. ovum 33.8 27.1 21.5 12.3 0.36 0.64 1.25

adansoni

146190-3 L. ovum 25.0 20.6 14.3 10.7 0.43 0.57 1.21

adansoni

146190- L. ovum 22.0 19.1 13.2 8.8 0.40 0.60 1.15

11 adansoni

146190- L. ovum 24.1 19.7 15.4 8.7 0.36 0.64 1.22

12 adansoni

146190- L. ovum 23.4 19.7 14.5 9.0 0.38 0.62 1.19

13 adansoni

146190-4 L. ovum 30.1 25.6 19.0 11.1 0.37 0.63 1.18

adansoni

146190-5 L. ovum 22.6 19.5 13.8 8.9 0.39 0.61 1.16

adansoni

146190-6 L. ovum 23.8 21.5 16.2 7.6 0.32 0.68 1.11

adansoni 155

Sp. No. Species H D h S S/H h/H H/D

146190-7 L. ovum 26.4 22.1 15.8 10.6 0.40 0.60 1.19

adansoni

146190-8 L. ovum 27.0 22.6 16.3 10.6 0.39 0.60 1.19

adansoni

146190-9 L. ovum 25.1 20.6 15.7 9.4 0.37 0.63 1.22

adansoni

Average 0.38 0.62 1.19

Std. Dev 0.03 0.03 0.04

448411-1 L. ovum 71.6 47.4 37.0 34.5 0.48 0.52 1.51

elongata

448411-2 L. ovum 45.5 30.3 24.5 21.0 0.46 0.54 1.50

elongata

Average 0.47 0.53 1.51

Std. Dev 0.01 0.02 0.01

120161-1 L. purpureus 54.7 33.4 27.8 26.9 0.49 0.51 1.64

217293-1 L. sinistrosus 21.8 20.8 14.6 7.1 0.33 0.67 1.05

217293-2 L. sinistrosus 22.5 21.3 15.1 7.4 0.33 0.67 1.06

Average 0.33 0.67 1.05

Std. Dev 0.00 0.00 0.01

439028-1 L. solidus 36.1 32.4 25.5 10.7 0.30 0.71 1.11 156

Sp. No. Species H D h S S/H h/H H/D

439028-2 L. solidus 39.5 39.0 28.5 11.0 0.28 0.72 1.01

Average 0.29 0.71 1.06

Std. Dev 0.01 0.01 0.07

120397-1 L. varicus 35.6 38.5 25.1 10.4 0.29 0.71 0.92

(Abbreviations. Sp. No. Specimen Number; H. Total shell height; D. Total shell width; h. aperture height; S. Spire height; Std. Dev. Standard Deviation; NA. Not available; all measurements are in mm). Average and standard deviation for each species presented beneath the specimen data for each species.

Note: Four specimens of Lanistes nsendweensis indicated by asterisks were not included in the morphometric analyses, but included in generating summary statistics (i.e., average, standard deviation) 157

APPENDIX E: FOSSIL SPECIMENS LOANED FROM NATURAL HISTORY

MUSEUMS INCLUDED IN MORPHOMETRIC ANALYSES

Specimen Species H D h S S/H h/H H/D

Number

UCMP14091 Lanistes carinatus 25.1 31.7 17.7 7.3 0.29 0.71 0.79

UCMP14092 Lanistes carinatus 30.8 35.7 22.8 8.0 0.26 0.74 0.86

Average 0.28 0.72 0.83

Std. Dev 0.02 0.02 0.05

UCMP154224 Lanistes ellipticus 36.7 32.5 20.6 16.1 0.44 0.56 1.13

UCMP154225 Lanistes ellipticus 41.4 34.7 27.6 13.8 0.33 0.67 1.19

UCMP154226 Lanistes ellipticus 35.5 26.8 20.4 15.1 0.42 0.57 1.32

UCMP154227 Lanistes ellipticus 31.9 27.7 19.2 12.7 0.40 0.60 1.15

UCMP154228 Lanistes ellipticus 41.8 36.5 27.0 14.7 0.35 0.65 1.15

Average 0.39 0.61 1.19

Std. Dev 0.05 0.05 0.08

(Abbreviations. H. Total shell height; D. Total shell width; h. aperture height; S. Spire height; Std. Dev. Standard Deviation; all measurements are in mm). Average and standard deviation for each species presented beneath the specimen data for each species

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