2011 Harrison - Laetoli galagids

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Abstract An additional specimen of a fossil galagid was recently recovered from the Upper Laetolil Beds at Laetoli in northern Tanzania. This new find represents the most complete specimen of a galagid known from Laetoli, and comprises asso-ciated partial right and left mandibular corpora. The galagid material from Laetoli can all be attributed to a single species, previously referred to as Galago sadimanensis. However, the taxon is sufficiently distinct from all extant galagids, as well as stem galagids from the Miocene of East Africa, to be placed in its own genus, Laetolia. The fossil record of galagids from the Pliocene of Africa is exceedingly poor, and Laetolia sadimanensis represents the best-known form. Laetolia can be distinguished from other galagids by its unique suite of morpho-logical features. The stout and vertical implantation of P

2, the

steeply inclined and robust symphysis, and the relatively deep corpus are all specialized features that are probably functionally linked. However, Laetolia has a less molariform P

4 than extant

galagids, and it can be inferred to represents their primitive sis-ter taxon. Based on molecular clock estimates, extant galagids shared a last common ancestor during the late Oligocene. It is interesting, therefore, to discover a sister taxon of extant galagids surviving in East Africa until at least the Pliocene, con-temporary with more advanced crown members of the clade. From a paleoecological perspective, the occurrence of fossil galagids at Laetoli implies the presence of habitats with at least a sparse coverage of trees and/or thorn bush.

Keywords Galagids • Laetoli • Mabaget Formation • Pliocene • Phylogeny

Introduction

A single species of galagid, Galago sadimanensis, is repre-sented by a number of partial mandibles from the Upper Laetolil Beds (3.63–3.85 Ma) at Laetoli (Walker 1987;

Harrison 2010). A mandibular fragment from the Mabaget Formation (~5 Ma), in the Tugen Hills of Kenya, collected earlier, has been referred to the same species (Walker 1987). Renewed investigations at Laetoli have yielded an additional galagid specimen (EP 1064/03). The specimen was discovered by Chris Robinson in 2003 at Loc. 10W in the Upper Laetolil Beds between Tuffs 1 and 3 (~3.8 Ma). It consists of associ-ated right and left mandibular fragments with P

2-M

3 and P

2,

P4-M

1 respectively, and it represents the most complete speci-

men of Galago sadimanensis known. The aim of this chapter is to describe briefly the new specimen, to present an updated account of the morphology of G. sadimanensis to highlight its distinctive features, and to clarify its taxonomic and phyloge-netic relationships. As discussed below, the species is consid-ered to be sufficiently distinct from extant galagids and from other fossil genera to be placed in its own genus.

The fossil record of galagids from the Plio-Pleistocene is exceedingly poor (Harrison 2010). Apart from Galago sadimanensis, the only other extinct species formally described is Otolemur howelli, based on a fragmentary maxilla, an iso-lated M

2, and an edentulous mandible from the lower part of

the Shungura Formation (~3.0–3.2 Ma) in the Omo Valley, Ethiopia (Wesselman 1984). Fragmentary finds of other fos-sil galagids are known from localities in East Africa, some of which probably belong to extant taxa. Several mandibular fragments, isolated teeth, and postcranial elements from Bed I (~1.8 Ma), Olduvai Gorge, northern Tanzania, can be referred to the extant species, Galago senegalensis (Simpson 1965; Szalay and Delson 1979; Gebo 1986; Harrison 2010). Wesselman (1984) described a fragmentary M

2 from lower

Member G (~2.0 Ma) of the Shungura Formation, Omo, Ethiopia, which he referred to Galago senegalensis, but the tooth is smaller than those of the modern taxon and it is best considered an indeterminate species (Harrison 2010). Wesselman (1984) also described an isolated M

2 from upper

Member B of the Shungura Formation (~3.0 Ma), which is very similar to Galagoides zanzibaricus, except that the crown is slightly narrower. Denys (1987) reported an iso-lated upper canine of a galagid from the Humbu Formation (~1.3–1.7 Ma) at Peninj, Tanzania, which is consistent in

T. Harrison (*) Center for the Study of Human Origins, Department of Anthropology, New York University, 25 Waverly Place, New York, NY 10003, USA e-mail: [email protected]

Chapter 5Galagidae (Lorisoidea, Primates)

Terry Harrison

T. Harrison (ed.), Paleontology and Geology of Laetoli: Human Evolution in Context. Volume 2: Fossil Hominins and the Associated Fauna, Vertebrate Paleobiology and Paleoanthropology, DOI 10.1007/978-90-481-9962-4_5, © Springer Science+Business Media B.V. 2011

76 T. Harrison

morphology and only slightly smaller than that of extant Galago senegalensis. Finally, Harris et al. (2003) described a mandibular fragment with M

2 of a diminutive galagid from

Kanapoi in Kenya (~4.1–4.2 Ma).Fossil galagids are also known from the late Miocene of

Africa. These include an isolated upper molar from Harasib 3a (~9–10 Ma) in Namibia (Conroy et al. 1993, 1996; Rasmussen and Nekaris 1998), several isolated teeth and postcranials of a small galagid, Galago farafraensis, from Sheikh Abdallah (~10–11 Ma) in Egypt (Pickford et al. 2006), and an undescribed mandible of a galagid from Kapsomin, in the Lukeino Formation (~6 Ma) in Kenya (Mein and Pickford 2006).

Extant galagos are included together in a single family, the Galagidae, which is restricted to sub-Saharan Africa. There are at least 24 species currently recognized, belonging to five genera - Galago, Galagoides, Otolemur, Euoticus, and Sciurocheirus (Kingdon 1997; Bearder 1999; Masters and Bragg 2000; Groves 2001; Grubb et al. 2003). A further genus name might be required to accommodate the Galagoides orinus group (sensu Grubb et al. 2003) if the Galagoides demidovii group proves not to be its sister taxon (see Fabre et al. 2009). The extant members of the family are characterized by the following cranio-dental features: molar-iform upper and lower P4; upper molars with large hypocone on an expanded distolingual lobe, well-developed prehypocone crista, deeply notched distal margin, long and distobuccally directed postmetacrista; lower molars with, elongated subtri-angular trigonid with beak-like mesial margin; relatively lightly constructed cranium; orbits lacking strong frontation and raised margins; shallow mandible and lower face; very inflated auditory bulla with pneumatization extending into the mastoid region (Harrison 2010).

Systematics

Order Primates Linnaeus, 1758Suborder Strepsirrhini Geoffroy, 1812Infraorder Lorisiformes Gregory, 1915Superfamily Lorisoidea Gray, 1821Family Galagidae Gray, 1825Subfamily Galaginae Gray, 1825Genus Laetolia gen. nov.

Diagnosis: A galagid similar in overall dental dimensions to the extant Galago senegalensis. It differs from extant genera of galagids (i.e., Galago, Euoticus, Galagoides, Sciurocheirus and Otolemur) in the following features: relatively deeper and more robust mandibular corpus; mandibular symphysis more vertical, with a relatively greater cross-sectional area, and an inverted tear-drop (rather than oval) sagittal section;

P2 stouter, lower-crowned, and more vertically implanted;

P2 larger in occlusal area than P

4; P

3 and P

4 relatively small

in relation to M1; P

4 less molarized with shorter and more

ovoid crown, rounded mesial margin, less well-developed metaconid, shorter and narrower talonid basin, and weakly developed entoconid and hypoconid; lower molars relatively narrower (Emended from Walker 1987; Harrison 2010). It differs from Komba (early and middle Miocene of East Africa) in the following respects: relatively thicker mandibu-lar corpus; mandibular symphysis more vertical, with a rela-tively greater cross-sectional area, and an inverted tear-drop sagittal section; P

2 relatively larger; P

4 relatively shorter, with

a less pronounced mesial beak, a less well-developed metaconid, relatively smaller distal cuspules, a shorter, broader and shallower talonid basin; P

4 slightly larger in

occlusal area relative to M1. Differs from Progalago (early

Miocene of East Africa) in having a relatively shallower mandibular corpus that does not increase in depth posteri-orly, and lacks a flange-like inferior margin; mandibular symphysis steeper and more robust; P

2 relatively larger; P

4

relatively shorter, with more pronounced distal cuspules, and a smaller talonid basin; P

4 slightly larger in occlusal area

relative to M1; lower molars narrower, with less-pronounced

buccal flare, longer and more triangular trigonid, more pro-nounced mesial beak, greater height differential between the trigonid and talonid, narrower and shallower talonid basin, more voluminous cusps, weaker occlusal crests, and more obliquely oriented distal margin (Walker 1987; Phillips and Walker 2002; Harrison 2010).

Type species: Laetolia sadimanensis (Walker 1987).Included species: L. sadimanensis (Walker 1987).Holotype: LAET 74-294, right mandibular fragment with P

2-M

2. Laetoli, Tanzania.

Hypodigm: Specimens listed in Table 5.1, plus KNM-BC 1646 from the Mabaget Formation, Kenya.

Table 5.1 List of galagid specimens from the Upper Laetolil Beds, Laetoli

Specimen Locality Element

LAET 74-294 Loc. 5 Left mandibular fragment with P

2-M

2

LAET 75-2433 Loc. 10W Right mandibular corpus and much of the ramus with P

2-M

2

LAET 75-2880 Loc. 10W Left mandibular fragment with P

2-P

3

LAET 76-4144 Loc. 11 Left mandibular fragment with base of P

2

LAET 78-4702 Loc. 7 Right mandibular fragment with M

2-M

3

EP 1064/03 Loc. 10W Right mandibular corpus with P

2-M

3 and left mandibular

corpus with P2, P

4-M

1

775 Laetoli Galagids

Distribution: Pliocene, ~3.6–5.0 Ma. Upper Laetolil Beds, Laetoli, Tanzania and Mabaget Formation, Kapchebrit, Baringo Basin, Kenya.Diagnosis: Same as genus.

Description of EP 1064/03

The specimen consists of two associated mandibular frag-ments comprising the right mandibular corpus with P

2-M

3

and the left mandibular corpus with P2 and P

4-M

1 (Fig. 5.1).

The right mandibular fragment comprises the entire corpus and the anterior and inferior aspects of the ramus. The corpus is preserved anteriorly as far as the symphysis, but the alveoli for the canine and incisors are poorly preserved, and the symphysis is incomplete superiorly. The rest of the corpus is entire and well-preserved, except for some faint pitting caused by weathering. On the lateral side of the corpus below P

4

there is single large elliptical mental foramen. A tiny accessory foramen is located vertically below P

3. The ramus is broken

obliquely and abraded, preserving only the root of the ante-rior margin of the ramus and the inferior border, extending posteriorly 8.3 mm beyond M

3. The dentition is lightly worn

and generally well-preserved, except for some minor weath-ering and abrasion. P

2 is missing the tip of the crown.

The left mandibular fragment consists of the symphyseal region and the corpus as far posteriorly as the alveolus for the anterior root of M

2. The symphysis and alveoli for the

canine and incisors are better preserved than on the right side and are almost complete. A large mental foramen is located below P

3/P

4, and a minute accessory foramen is positioned

below P2. There is a fresh break through the corpus behind

M1, indicating that the posterior portion of the corpus was

detached after the specimen eroded out onto the surface. The preserved teeth are complete, but their enamel surfaces are slightly weathered. P

3 is represented by the roots only.

Morphology of Laetolia sadimanensis

Only the lower dentition and mandibles of Laetolia sadiman-ensis are known (see Table 5.1). The mandibular corpus is relatively deep and more robust than in modern galagids. It maintains a constant depth below the cheek teeth or shallows slightly posteriorly. There is a single mental foramen posi-tioned vertically below P

3 or P

4 (Table 5.2), and located just

below mid-height (40–45% up from the inferior margin). A tiny accessory foramen is commonly located just anterior to the main foramen. The symphysis is stout, with an antero-posterior thickness of 65–75% of its height, compared with

Fig. 5.1 EP 1064/03, right and left mandibular fragments of Laetolia sadimanensis. (a) right mandibular fragment with P

2-M

3, lateral view;

(b) right mandibular fragment with P2-M

3, medial view; (c) right

mandibular fragment with P2-M

3, occlusal view; (d) left mandibular

fragment with P2, P

4-M

1, lateral view; (e) left mandibular fragment with

P2, P

4-M

1, medial view; (f) left mandibular fragment with P

2, P

4-M

1,

occlusal view. All to the same scale

78 T. Harrison

55–65% in extant galagids. The symphysis was unfused with no indication of synostosis. In section, the symphysis forms the shape of an apostrophe, with an almost circular superior portion and a smaller inferior torus that projects posteriorly. In modern galagids, the symphysis forms a flat ellipse, with no development of an inferior torus. The symphysis is more steeply inclined than in modern galagids, as well as in Miocene taxa, with a mean angle of the long-axis at 66° to the alveolar plane. The incisors and canines are not preserved in any of the specimens, so it is not possible to determine the degree of procumbency of the toothcomb. The average mini-mum width between the P

2s can be estimated to be 3.2 mm

(range 3.0–3.6 mm). This is comparable in breadth to the similar-sized Galago senegalensis, and implies that the Laetoli galagid had a narrow toothcomb as in extant taxa.

Parts of the ramus are preserved in LAET 75-2433, LAET 78-4702 and EP 1064/03. The anterior margin of the ramus is set far back from M

3 and inclined posteriorly at angle of

about 125° relative to the alveolar plane as in extant galagids. The coronoid process is not preserved. The base of the con-dyle is preserved in LAET 75-2433, and appears to have been slightly lower than in extant galagids, being situated just above the level of the occlusal plane of the molars. The ramus is antero-posteriorly quite long, being 185% the length of the molar row. This exceeds the relative length in extant

galagids, and more closely approximates the condition seen in some lorisids, such as Perodicticus. The posterior angle of the mandible is not preserved, but judging from the strongly downturned inferior margin behind M

3 it was quite expanded.

A similar pattern is seen in Otolemur, but is less pronounced in the smaller extant galagids.

Dimensions of the lower cheek teeth of Laetolia sadi-manensis are presented in Table 5.3. P

2 is a robust canini-

form tooth, relatively vertically implanted, with a single stout root. It has a convex mesial face and a longer concave distal face, with a short distal heel. The lingual face is bor-dered basally by a narrow cingulum. The P

2 is more robust

than the similar-sized tooth in Galago senegalensis, and contrasts with the more procumbent sectorial tooth seen in all extant galagids. Even accounting for the variability in the form of P

2 in modern galagids, in which the larger species

tend to have the most vertical and caniniform teeth, the degree of procumbency in the Laetoli galagid is much less marked even than in Otolemur. In the robusticity and orien-tation of the P

2 Laetolia sadimanensis approaches the spe-

cialized condition in extant lorisids. P2 is larger than P

4, with

the average occlusal area 117% of that of P4. In Miocene

and extant galagids, the occlusal area of P2 is typically

smaller than P4 (e.g., Progalago dorae, 97%; Komba robus-

tus, 88%; Komba winamensis, 67%; Galago senegalensis,

Table 5.2 Mandibular dimensions (mm) of Laetolia sadimanensis

LAET 294

LAET 2433

LAET 2880

LAET 4144

LAET 4702

KNM-BC 1646

EP 1064/03 (right)

EP 1064/03 (left)

Angle of symphysisa 64° 64° 71° 63° 70° 62°Depth at symphysisb 5.2 5.7 5.5 5.2Thickness at symphysisc 3.4 4.2 3.6 3.6 3.3Depth at M1d 5.1 5.2 5.1 4.0 4.9 4.7Depth at M2d 4.9 4.9 5.0 4.4Depth at M3d 5.4 5.2 4.5Position of foramene mid P4 mes P4 dist P3 mid P4 mes P4 mes P4 P3/P4a Angle of the symphysis midline axis relative to the alveolar plane of the mandibular corpusb Maximum length of the symphyseal face measured along the midline of its long-axisc Maximum breadth of the symphyseal face measured perpendicular to the midline long-axisd Infero-superior depth of the mandibular corpus below the lower molarse Vertical position of the main mental foramen below the cheek teeth: dist P3, below the distal moiety of P

3; P3/P4, below the contact between P

3

and P4; mes P4, below the mesial moiety of P

4; mid P4, below the transverse midline of P

4

Table 5.3 Dental dimensions (mm) of Laetolia sadimanensis

Specimen

P2

P3

P4

M1

M2

M3

MD BL MD BL MD BL MD BL MD BL MD BL

LAET 74-294 2.1 1.4 1.8 0.9 2.0 1.3 2.0 1.8LAET 75-2433 2.4 1.6 2.0 1.0 2.0 1.5 2.0 1.9 2.0LAET 75-2880 2.2 1.4 1.9 1.0LAET 76-4144 2.2 1.3LAET 78-4702 2.3 2.0 2.8 1.8KNM-BC 1646 2.4 1.3 1.8 1.1 1.8 1.5EP 1064/03 (right) 2.0 1.3 1.8 1.0 1.7 1.4 2.2 1.8 2.1 1.7 2.2 1.4EP 1064/03 (left) 2.3 1.4 1.7 2.1 1.8Mean 2.2 1.4 1.9 1.0 1.9 1.4 2.0 1.8 2.2 1.8 2.5 1.6

795 Laetoli Galagids

68%; Otolemur crassicaudatus, 96%; Galagoides zanzi-baricus, 68%). In this respect, Laetolia sadimanensis begins to approach the more specialized condition in extant lorisids (e.g., Loris tardigradus, 137%; Perodicticus potto, 136%; Nycticebus coucang, 181%).

P3 is a long, slender sectorial tooth with a single main

cusp, the protoconid, situated in the midline one-third back from the mesial margin of the crown. The mesial and distal crests are sharp. The distolingual crest is more rounded. There is a weakly developed lingual cingulum. There are two roots. The tooth is similar in overall morphology to that of G. senegalensis, but differs in being relatively smaller in relation to M

1. The average occlusal area of P

3 is 53% of that

of M1 (compared with 63% in Galago senegalensis).

P4 is a short, ovoid tooth with an elevated protoconid and

a poorly developed metaconid. The talonid basin is short, and bordered distally by a pair of low, rounded tubercles, the entoconid and hypoconid. There are two roots. P

4 is rela-

tively small in relation to M1. The occlusal area averages

70% of that of M1, slightly greater than in early Miocene

galagids (e.g., Progalago dorae, 64%; Komba robustus, 63%), but smaller than in extant taxa (e.g., Otolemur crassi-caudatus, 74%; Galago senegalensis, 77%). In sum, the P

4 is

less molarized than in extant galagids, with a shorter, more ovoid crown, less well-developed metaconid, shorter and narrower talonid basin, and weakly developed entoconid and hypoconid. Laetolia also differs from extant galagids in having a less pronounced prow-like mesial beak at the front of the tooth. The P

4 of Laetolia is more derived than Komba

from the Miocene of East Africa, in having a broader talonid basin and in being relatively larger in comparison to the occlusal area of M

1. Both of these features presage the greater

degree of molarization seen in extant galagids. The P4 of

Progalago, a possible stem galagid from the early Miocene of East Africa, differs in having a longer crown, with a more voluminous talonid basin, and weaker distal cuspules.

M1 has four main cusps. The protoconid and metaconid

are subequal in height, relatively low, and positioned quite close together. The protoconid is situated slightly more mesially than the metaconid, so that the transverse crest connecting them is slightly oblique. There is a slight trace of a buccal cingulum around the protoconid. The mesial fovea is quite short, with a convex mesial margin. The hypoconid and ento-conid are less elevated than the trigonid cusps and are spaced further apart than the protoconid and metaconid. The cristid obliqua, passing mesially from the hypoconid, is long and obliquely directed. The metaconid and entoconid are sepa-rated by a shallow lingual notch. The talonid basin is quite broad, but shallow. The distal margin of the tooth is obliquely oriented to the transverse axis of the crown. M

2 is subequal

in size to M1 and morphologically very similar. It differs in

being broader mesially, with the mesial cusps set further apart, and having a more oblique distal margin. M

3 is rela-

tively narrower than M2, but variable in overall relative size

(see Table 5.3). In LAET 78-4702 its occlusal area is slightly larger than that of M

2 (110%), whereas in EP 1064/03 it is

smaller (86%). The crown narrows distally. It has five cusps, with a variably developed hypoconulid. The hypoconulid heel is well-developed in LAET 78-4702 and relatively weak in LAET 1064/03. The hypoconid and entoconid are reduced in size relative to the trigonid cusps.

Taxonomic and Phylogenetic Relationships

Laetolia sadimanensis can be distinguished from all extant galagids by its unique combination of morphological fea-tures. These include a relatively deeper and more robust mandibular corpus, a more vertical mandibular symphysis with a greater cross-sectional area and an inverted tear-drop sagittal section, a more robust, lower-crowned, relatively larger and more vertically implanted P

2, posterior premolars

relatively small in relation to the molars, P4 less molarized,

with a shorter and more ovoid crown, a rounded mesial mar-gin, a less prominent metaconid, a shorter and narrower talo-nid basin, and more weakly developed entoconid and hypoconid, and relatively narrower lower molars. The extent of these difference necessitate including the Laetoli galagid in a separate genus. The distinctive features of the mandible and P

2 are best interpreted as autapomorphies (see Walker

1987; Harrison 2010). The hypertrophy and vertical implan-tation of the P

2, the steep inclined and robust symphysis, and

the relatively deep corpus are probably functionally linked, and exhibit some degree of convergence on the morphology seen in extant lorisids. However, as noted above, Laetolia sadimanensis appears to be more primitive than all extant galagids in having a less molariform P

4. This condition is

most closely approximated by Galago spp. among extant galagids, although the latter do have a relatively larger P

4

with a more expanded talonid basin. Compared to Miocene galagids, such as Progalago and Komba, Laetolia is more derived in having a greater degree of P

4 molarization, with a

relatively larger crown, more expansive talonid (compared with Komba) and better-developed distal cuspules (compared with Progalago). Thus, based on this evidence, Laetolia can be inferred to be the sister taxon of all extant galagids (see Fig. 5.2).

Conclusions

An additional specimen of a fossil galagid, comprising asso-ciated partial right and left mandibular corpora (EP 1064/03), was recovered from the Upper Laetolil Beds at Loc. 10W in 2003.

80 T. Harrison

This specimen now represents the most complete specimen of a Pliocene galagid. The material from Laetoli can all be attributed to a single species, previously known as Galago sadimanensis. However, the taxon is considered to be suffi-ciently distinct from extant and Miocene galagids to be placed in its own genus, Laetolia nov. gen. The fossil record of galagids from the late Miocene and Pliocene is relatively poor, and Laetolia sadimanensis represents the best-known form.

Laetolia sadimanensis is distinguished from all extant galagids by its unique combination of features. The stout and vertical implantation of the P

2, the steeply inclined and robust

symphysis, and the relatively deep corpus are all specialized features and probably functionally linked. However, Laetolia sadimanensis has a less molariform P

4 than extant galagids,

and it probably represents the primitive sister taxon to crown galagids (see Fig. 5.2). Given that crown galagids are esti-mated to have shared a last common ancestor during the late Oligocene (Fabre et al. 2009), based on molecular evidence, it is interesting to discover that a rather specialized sister taxon of extant galagids survived in East Africa until at least the mid-Pliocene contemporary with more advanced crown members.

Not much can be deduced about the paleoecology at Laetoli based on the rare occurrence of fossil galagids. Modern-day species have a wide distribution throughout sub-Saharan Africa, ranging from tropical forests and dry forests, to acacia woodland, savanna and thorn scrub (Kingdon 1997). Galago senegalensis is found today at

Laetoli, occurring in riverine and open acacia woodland. Given that all extant galagids are arboreal, and need trees or thorn bushes for feeding and as sleeping sites, we can infer that the vegetation at Laetoli during the Pliocene included at least open woodland or thorn scrub.

Acknowledgements The author is grateful to the Tanzania Commission for Science and Technology and the Unit of Antiquities in Dar es Salaam for permission to conduct research in Tanzania. Special thanks go to Paul Msemwa (Director) and Amandus Kweka, as well as to all of the staff at the National Museum of Tanzania in Dar es Salaam, for their support and assistance. The Government of Kenya and the National Museums of Kenya are thanked for permission to study the collections in Nairobi. Thanks to Emma Mbua, Mary Muungu, Meave Leakey (Kenya National Museum), Jerry Hooker, Peter Andrews, Paula Jenkins, Daphne Hills (Natural History Museum, London), Nancy Simmons, Ross MacPhee, and Eileen Westwig (American Museum of Natural History, New York) for access to specimens in their care. For their advice, discussion, and help I gratefully acknowledge the following individuals: P. Andrews, E. Delson, C. Jolly, D.M.K. Kamamba, M.G. Leakey, C.S. Msuya, S. Odunga, M. Pickford, L. Pozzi, and D. Su. I am especially grateful to R. Kay and H. Wesselman for their feed-back on the manuscript. Research on the Laetoli galagids was supported by grants from the National Geographic Society, the Leakey Foundation, and NSF (grants BCS-9903434 and BCS-0309513).

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Fig. 5.2 Cladogram showing the inferred phylogenetic relationships of Laetolia with Miocene galagids (i.e., Komba and Progalago) and extant galagids (i.e., Galagoides, Otolemur, Sciurocheirus, Galago, Euoticus). Relationships between extant galagids are based on data from Fabre et al. (2009). Morphological features used to place Laetolia as the sister taxon to extant galagids are described in the text

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