The Origin and Evolution of Mammals - Moodle

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For the recovery phase, the relatively modest iliofemoralis muscle, running between the posteriorly directed ilium and the dorsal surface of the femur, elevated the limb, while the pubo-ischio-femoralis internus was the protractor. It ran forwards from the inner face of the pubo-ischiadic plate, wrapped around the front edge of the pubis, and turned backwards to insert on the front of the femur. As in the case of the forelimb, rotation of the femur about its long axis was due to the exact points of attach- EVOLUTION OF MAMMALIAN BIOLOGY 105 (a) IL (b) il.tib il.fib il.fem (c) (d) PU art.h CALC fib F il.fem p.i.f.e p.i.f.e tr.int tr 4 tib acet isch.tr p.i.f.e il.fem tr.ext (e) p.i.f.i ISC p.i.f.i AST T il.fem p.i.f.e FIB CALC p.i.f.e T CALC. AST AST Figure 4.6 Pelycosaur-grade hindlimb, based on Dimetrodon. (a) Lateral view of the left pelvic girdle. (b) lateral view of pelvis and hindlimb, with the four major muscles reconstructed. (c) Ventral and dorsal views of left femur. (d) distal view of the femur, crus, and proximal tarsus to show rotation action of tibia and fibula. (e) Anterior view of left hindlimb. acet, acetabulum; art.h, articulating head of femur; AST, astragalus, c.f, caudi femoralis muscle; CALC, calcaneum; F, femur; FIB, fibula; fib, articulating facet for fibula; IL, ilium; il.fem, ilio.femoralis muscle; il.fib, origin for ilio-fibularis muscle; il.tib, origin for ilio-tibialis muscle; ISC, ischium; isch.tr, origin for ischio-trochantericus muscle;p.i.f.e, pubo-ischio femoralis externus muscle; p.i.f.i, pubo-ischio femoralis internus muscle; PU, pubis; T, tibia; tib, articulating surface for tibia. tr.ext, trochanter externus; tr.int, trochanter internus; tr.4, fourth trochanter (Kemp 1982). T FIB ment of these four muscles on the bone relative to the long axis. Also as in the forelimb, there were strong extensor muscles, particularly the triceps, attaching to the outer parts of the tibia and fibula. A complex of antagonistic flexor muscles attached to the flexor surfaces of these bones. Basal therapsid grade Sphenacodontine locomotion is characterised by massive limb girdles and short, heavy, sprawling c.f
106 THE ORIGIN AND EVOLUTION OF MAMMALS limbs, and was doubtless slow and clumsy by modern standards. Nevertheless it was the starting point for the evolution of what became the agile, long-limbed parasagittal gait seen in typical mammals. Indeed, one hint of the mammalian design has already been seen in pelycosaurs, namely the reduction of the lateral undulation of the vertebral column. However, even in the most basal of therapsids, numerous significant new developments in the direction of the mammals are to be found. Ideally at this point the postcranial skeleton of the biarmosuchian grade should be described and interpreted, but unfortunately it is very poorly known. Sigogneau and Chudinov (1972) and Sigogneau-Russell (1989b) have described several isolated postcranial bones of Biarmosuchus, as has Boonstra (1965) for the South African Hipposaurus. As far as it is known, it shares a general similarity to the far better understood gorgonopsian skeleton. Several complete and many partial specimens of the latter taxon have been described (Sigogneau- Russell 1989) and aspects of the functional anatomy considered (Colbert 1948; Kemp 1982; Sues 1986a). Furthermore, they are not too dissimilar from a basal, brithopian dinocephalian such as Titanophoneus. Taken together, these groups can be combined to create a general picture of the structure and functioning of the primitive therapsid-grade postcranial skeleton. Axial skeleton. Considering first the axial skeleton, the very attachment of the vertebral column to the skull was modified to increase the mobility of the head relative to the body (Kemp 1969a). The occipital condyle broadened to a kidney shape, which permitted the head to rotate about the longitudinal axis (‘shaking’) through many more degrees without the first vertebra, the atlas, damaging the spinal cord. It also increased the extent of dorso-ventral rotation of the skull about a transverse axis (‘nodding’) without undue stretching of the spinal cord because each of the paired neural arches of the atlas articulated to the side rather than directly below the foramen magnum. Behind the atlas and axis, there are five cervical vertebrae. These have broad, horizontal zygapophyses, and intercentra are retained between adjacent vertebrae, both features indicating that large lateral movements of the head were accommodated by the intervertebral joints of the neck. The dorsal region of the vertebral column between the pectoral and pelvic girdles is relatively undifferentiated at this stage (Fig. 3.16(a)). There is no significant anatomical distinction between thoracic and lumbar vertebrae, and moveably attached, ventrally directed ribs extend for the full length. The zygapophyses are close to vertically oriented, and intercentra are absent, both indicating that lateral undulation was virtually eliminated, but as yet dorso-ventral bending of the vertebral column had not evolved. Three sacral vertebrae are present, behind which the tail was probably very much reduced in length compared to pelycosaurs, although no completely preserved specimen is yet known. Forelimb. The basal therapsid shoulder girdle and forelimb (Fig. 4.7(a)) have undergone a profound change. The dermal shoulder girdle arch, formed from the interclavicle and clavicles, is far less massive and the contact between the clavicle and the scapulo-coracoid looser. The scapula blade is much narrower and the coracoid plate shorter. Significant movements of the scapulo-coracoid relative to the ribcage had evolved by this stage, adding to the total stride length of the forelimb. Although to a limited degree at this stage, the change anticipates the fuller expression of scapulo-coracoid mobility in later cynodonts and most extremely in mammals. The most remarkable evolutionary change in the forelimb concerns the shoulder joint (Fig. 4.7(a)). The glenoid no longer has the elongated screw shape found in the pelycosaurs, but is a short notch formed equally between the scapula above and the coracoid below. It faces postero-laterally, and the surface is concave from top to bottom, but convex from front to back. The corresponding articulating surface of the humerus is curiously very different, for it is in the form of a hemicylinder on the proximal surface of the head that is much longer than the glenoid. The extreme incongruity between the respective articulating surfaces of the shoulder joint can only be explained by a very subtle mechanism (Kemp 1980c, 1982). The shoulder joint must have functioned by a roller action between the two opposing articulating surfaces, analogous to a wheel passing over the ground, rather than the sliding action between the opposing surfaces found in most joints (Fig. 4.7(b)). Beginning at the start of the
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The Origin and Evolution of Mammals
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The Origin and Evolution of Mammals
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Preface This book arose from twin a
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For Mal /gosia with love and thanks
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Contents 1 Introduction The definit
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CHAPTER 1 Introduction There are ab
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transversely occluding molar teeth
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the Mesozoic mammals, is to do with
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a hierarchy of committees under the
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it means that a 200 Ma igneous rock
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een a more fundamental impact than
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Table 2.3 Classification of marsupi
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(a) (b) (c) humerus radius aquatic
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(a) Westlothiana Limnoscelis PO Wes
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the ankle bones to form an astragal
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(b) (c) (a) Casea rutena Casea broi
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(Fig. 3.2(f)), is actually an ophia
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the first one is enlarged, often to
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Even at their initial appearance in
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(a) Nikkasaurus (b) (d) Reiszia (e)
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Nikkasauridae The family Nikkasauri
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has figured large in discussions of
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(c) Figure 3.9 (continued). Syodon
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a mixture of progressively more spe
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animal with interdigitating, but no
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(e) (a) Anomocephalus Ulemica (b) S
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mandibulae musculature. This, as in
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To date the postcranial skeleton of
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ecognised four subgroups, based mai
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the presence of a deep, longitudina
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collected from the Lystrosaurus Ass
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(a) (d) (c) (b) Leontocephalus V PA
Page 66 and 67: (a) (c) Lycosuchus Oliveria (d) EVO
Page 68 and 69: separate families. Lycosuchidae (Fi
Page 70 and 71: consist of a large labial cusp and
Page 72 and 73: Procynosuchus (d) Procynosuchus (a)
Page 74 and 75: They constitute the monophyletic gr
Page 76 and 77: Although there is no mammal-like co
Page 78 and 79: Cynognathidae Cynognathus (Fig. 3.2
Page 80 and 81: (e) (f) Figure 3.22 (continued). Ma
Page 82 and 83: (c) (d) (a) (b) Kayentatherium EVOL
Page 84 and 85: Pachygenelus (e) (a) (c) Therioherp
Page 86 and 87: palatal, and orbitosphenoid bones,
Page 88 and 89: Wible and Hopson 1993). The interor
Page 90 and 91: published a cladogram based on rece
Page 92 and 93: 310-320 Ma. By this time, the great
Page 94 and 95: are forms such as Casea itself, var
Page 96 and 97: lakes and swamps in the low-lying l
Page 98 and 99: urrowing and subsisting on a diet o
Page 100 and 101: Eothyris Haptodus sphenacodontine B
Page 102 and 103: z (a) (c) a.pt.m. M B PO P P SQ P M
Page 104 and 105: (b) a.pt.m. temp.m. a.pt.m. temp.m.
Page 106 and 107: the dentary bone above the level of
Page 108 and 109: the therocephalian grade was not on
Page 110 and 111: A balance was also achieved in the
Page 112 and 113: Locomotion Ancestral amniote grade
Page 114 and 115: screw-shaped: the front part faces
Page 118 and 119: SC PRC p.i.f.i tr.min (c) dp.cr ect
Page 120 and 121: the therocephalian pelvis and hindl
Page 122 and 123: spc s.sp s.sp SC PRC (d) delt T AST
Page 124 and 125: no significant novelties to what ha
Page 126 and 127: (a) (c) (e) (g) D D ex. au.m C tym
Page 128 and 129: (a) (c) (d) PMX (f) V n.turb mx.tur
Page 130 and 131: ol.b (a) (b) cer.hem gorgonopsian t
Page 132 and 133: (a) (b) (i) (ii) (iii) (iv) (v) a g
Page 134 and 135: cold stress, the part that usually
Page 136 and 137: conducted the experiment of wrappin
Page 138 and 139: mammals themselves that the enlarge
Page 140 and 141: elevation of maximum aerobic activi
Page 142 and 143: a mammal. The difficulty with all s
Page 144 and 145: collection, ingestion, and assimila
Page 146 and 147: were edaphosaurid and caseid pelyco
Page 148 and 149: CHAPTER 5 The Mesozoic mammals The
Page 150 and 151: (a) (d) AL condylar foramina are se
Page 152 and 153: evidence to relate the haramiyidans
Page 154 and 155: postcranial skeleton, and Graybeal
Page 156 and 157: side of the head can be in action a
Page 158 and 159: the lower molars is relatively high
Page 160 and 161: morganucodontan teeth. However, des
Page 162 and 163: adjacent lower molars. A small exte
Page 164 and 165: (a) (b) (d) P4 P4 Plagiaulax P4 Pau
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American Morrison Formation genus C
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a self-sharpening property. As the
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near parasagittal gait (Fig. 5.11(e
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pass through the birth canal. Relat
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(a) 1 (b) (d) me (c) me.d 3 styl st
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(a) (c) Henkelotherium Crusafontia
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pubis is excluded from the acetabul
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Cretaceous, (Aptian or Albian) of M
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eautifully preserved placentals fro
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subsequent specimens revealed that
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Minimal divergence of tribosphenida
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(c) (a) M 1 M 1 M 2 Steropodon M 2
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(b) (a) (c) pa.d pr.d me.d Ambondro
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crown-group therians) is accepted b
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form of the tooth, must reflect sub
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of feasibility that a taxon of endo
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mammals, by creating environmental
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the 11 species of marsupial, of whi
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(d) (a) pa A Dasyuromorphia B C pr
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earing two huge claws on digits thr
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that contains the independent ances
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(b) (d) (a) Glasbius Alphadon (c) D
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elieved to be Late Cretaceous in ag
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(Fig. 6.5(c)). The dentition exhibi
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(d) Figure 6.6 (continued). Thylaco
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(a) (c) Caroloameghina and Procarol
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(a) (e) (d) Proargyrolagus Groeberi
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(a) (b) Djarthia Thylacotinga (c) (
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LIVING AND FOSSIL MARSUPIALS 211 M
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Extinct Notoryctemorphia At present
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(f) (g) Wakaleo Diprotodon optatum
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fossil mammals, which might help cl
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30 40 50 60 Figure 6.13 Southern Go
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the Diprotodontia also included gen
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1. Placentalia 2. Edentata 3. Epith
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effectively absent. However, increa
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Asioryctes (a) (b) (d) Cimolestes p
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and Prokennalestes, although it doe
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(a) Leptictidium Palaeoryctidans we
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(a) Purgatorius (c) are part of the
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(a) (d) (e) (g) Protoungulatum Meso
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(a) (f) (e) Hyopsodus Phenacodus (d
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Titanoides (pantodont) (a) (c) (b)
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(a) (b) (d) Trogosus (tillodont) Es
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Mioclaenus Paulacoutoia (didolodont
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their presence. The five orders may
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Xenungulata. Only two Late Palaeoce
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(a) (b) (d) (c) Oxyaena Patriofelis
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continuously growing, and form a gr
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navicular facet, 19 or more thoraci
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(a) (c) Phosphatherium Numidotheriu
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coexist with other characters that
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The salient feature of Widanelfasia
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1 (a) 1. Perissodactyla 2. Titanoth
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(a) (b) BUNODONTIA or SUIFORMES SUI
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time, which suggests that it was on
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condition. This particular combinat
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etween Primates, Dermoptera (colugo
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have postcranial adaptations for ar
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undoubtedly related at a supraordin
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indisputably to occur prior to the
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The Late Cretaceous mammal record i
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interordinal divergences in the Lat
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diversity on Earth (Janis 1993). Fu
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effect of the surrounding sea. Trop
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was high. It lasted from 5 to 3 Ma
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and thus remain in their preferred
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agreement about exactly when within
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References Abdala, F. Redescription
Page 304 and 305:
Ax, P. 1987. The phylogenetic syste
Page 306 and 307:
Bramble, D. M. 1978. Origin of the
Page 308 and 309:
Colbert, E.H. 1948. The mammal-like
Page 310 and 311:
Duvall, D. 1986. A new question of
Page 312 and 313:
Gow, C.E. 1980. The dentitions of t
Page 314 and 315:
Ivakhnenko, M.F. 1990. The late Pal
Page 316 and 317:
Kemp, T.S. 1988a. A note on the Mes
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cladogenesis in dasyurid marsupials
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(eds) Evolution of Tertiary mammals
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McKenna, M.C. and Bell, S.K. 1997.
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(ed) The phylogeny and classificati
Page 326 and 327:
Ray, S. 2000.Endothiodont dicynodon
Page 328 and 329:
Rubidge, B.S., Kitching, J.W., and
Page 330 and 331:
Simpson, G.G. 1970. The Argyrolagid
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Thewissen, J.G.M. 1990. Evolution o
Page 334 and 335:
Novacek, M.J., and McKenna, M.C. (e
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Index Note: Page numbers in italics
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Equoidea 262 Equus 262 Erethizon 28
Page 340 and 341:
Overkill hypothesis 289, 290 Oxyaen
Page 342:
Tulerpeton 14, 18 Tylopoda 264 Ukha
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The Origin and Evolution of Mammals - Moodle

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