The Origin and Evolution of Mammals - Moodle

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a self-sharpening property. As the dentine wears away at a higher rate than the enamel, the latter remains as a sharp, cutting edge at the front of the tooth. The glenoid fossa of the jaw articulation in these forms is extended forwards increasing the maximum anterior shift of the lower jaw. Their upper and lower incisors could therefore come into direct contact for active biting, unlike those of Ptilodus. The lower premolar teeth are smaller than those of ptilodontoids, confirming that the premolars had to some extent given way to the incisors in the initial preparation of the food, possibly indicating a diet of seeds that required de-husking prior to mastication. Several practically complete and many partial postcranial skeletons and isolated bones of multituberculates are known (Fig. 5.11). The skeleton shows a number of similarities to that of modern therian mammals, but at the same time there are several quite different features. This has led to a divergence of views both about the functional anatomy, and about how far the postcranial skeleton does or does not support a relationship between multituberculates and therian mammals. In the forelimb, the scapula is narrow with an outturned anterior spine which, as interpreted by Sereno and McKenna (1995), means there was no development of a supraspinous fossa. However, Kielan-Jaworowska and Gambaryan (1994) regard the antero-medial face of the spine as an incipient supraspinous fossa, onto which the equivalent of the supraspinatus muscle already attached. The coracoid is very reduced as in therians, but remains as a distinctive, pointed process. The glenoid cavity faces more ventrally than laterally, and is only about half the diameter of the bulbous, upturned head of the humerus. Clavicles and interclavicles are present. According to Sereno and McKenna (1995) the elbow joint has a trochlea form similar to that seen in modern therians, and which restricts movements to a hinge action about a single axis. In Nemegtbaatar, by contrast, Kielan-Jaworowska and Gambaryan (1994) described the condyles on the end of the humerus for both the radius and the ulna as convexities, and the radial condyle as spherical. From this they infer that the elbow was capable of a wider variety of movements than just strictly hinging about one axis. THE MESOZOIC MAMMALS 157 The pelvis and hindlimb are also distinct from other mammals in several respects (Krause and Jenkins 1983; Kielan-Jaworowska and Gambaryan 1994). The narrow iliac blade attaches at a relatively very high angle to the line of the sacral vertebrae, while the pubo-ischiadic plate extends deeply below the acetabulum. The acetabulum itself is open dorsally. A pair of epipubic bones is present, although this may be a primitive feature of mammals generally. The articulating head of the femur is on the end of a distinct neck that is set at an angle to the shaft of the bone. A very prominent trochanter major extends well proximal to the head, and a smaller trochanter minor lies on the underside, where the neck and trochanter major meet. There is no sign of a third trochanter. The tibia is unusual in being wider from lateral to medial surfaces than from anterior to posterior, and both tibia and fibula possess a hook-like lateral process on the proximal end of the bone. There are considerable differences in the interpretation of locomotor function in multituberculates. Jenkins and Krause (1983) argued for an arboreal mode of life in Ptilodus, on the basis of the structure of the pes, and the tail (Fig. 5.11(c)). Within the ankle, the joint between the calcaneum and the astragalus permitted extensive flexionextension. The joint between the distal end of the tibia and the calcaneum consisted of a pair of facets, which permitted the calcaneum to abduct, causing rotation of the distal end of the pes laterally and then posteriorly to the extent that the foot could point almost backwards. They also recognised the possibility of extensive, independent movement of the first digit. Together, these movements would have allowed the foot to be turned backwards and to gain purchase while the animal descended head first down a tree. The tail is very long, possesses well-developed haemal arches on the caudal vertebrae, and there are long neural spines on the sacral vertebrae from which powerful tail muscles could have originated, all of which indicate a prehensile tail. A second proposed mode of locomotion in multituberculates arises from Sereno and McKenna’s (1995) description of a complete, articulated forelimb of the djadochtatherioid Bulganbaatar. They argued that its structure indicates a fully therian
158 THE ORIGIN AND EVOLUTION OF MAMMALS (c) (a) Ptilodus (iii) (ii) (e) (b) (d) (i) Nemegtbaatar dorsal view Lambdopsalis lateral view Figure 5.11 Multituberculate locomotion. (a) Postcranial skeleton of Nemegtbaatar gobiensis. Presacral length approx. 12.0 cm (Kielan-Jaworowska and Gambaryan 1994). (b) Interpretation of hindlimb function in lateral and anterior views (Kielan-Jaworwska and Gambaryan 1994). (c) Ptilodus hindfoot in posteriorly directed and in forwardly directed positions, and whole skeleton descending tree (Jenkins and Krause 1983). (d) Humerus of the presumed burrowing multituberculate Lambdopsalis bulla. Length approx. 3.6 cm. (e) Relatively parasagittal action of multituberculate forelimb in dorsal and lateral views, according to Sereno and McKenna (Gambaryan and Kielan-Jaworowska 1997, after Sereno and McKenna 1995). (iii) (i)
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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
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(a) (c) Lycosuchus Oliveria (d) EVO
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separate families. Lycosuchidae (Fi
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consist of a large labial cusp and
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Procynosuchus (d) Procynosuchus (a)
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They constitute the monophyletic gr
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Although there is no mammal-like co
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Cynognathidae Cynognathus (Fig. 3.2
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(e) (f) Figure 3.22 (continued). Ma
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(c) (d) (a) (b) Kayentatherium EVOL
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Pachygenelus (e) (a) (c) Therioherp
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palatal, and orbitosphenoid bones,
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Wible and Hopson 1993). The interor
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published a cladogram based on rece
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310-320 Ma. By this time, the great
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are forms such as Casea itself, var
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lakes and swamps in the low-lying l
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urrowing and subsisting on a diet o
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Eothyris Haptodus sphenacodontine B
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z (a) (c) a.pt.m. M B PO P P SQ P M
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(b) a.pt.m. temp.m. a.pt.m. temp.m.
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the dentary bone above the level of
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the therocephalian grade was not on
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A balance was also achieved in the
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Locomotion Ancestral amniote grade
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screw-shaped: the front part faces
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For the recovery phase, the relativ
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
Page 166 and 167: American Morrison Formation genus C
Page 170 and 171: near parasagittal gait (Fig. 5.11(e
Page 172 and 173: pass through the birth canal. Relat
Page 174 and 175: (a) 1 (b) (d) me (c) me.d 3 styl st
Page 176 and 177: (a) (c) Henkelotherium Crusafontia
Page 178 and 179: pubis is excluded from the acetabul
Page 180 and 181: Cretaceous, (Aptian or Albian) of M
Page 182 and 183: eautifully preserved placentals fro
Page 184 and 185: subsequent specimens revealed that
Page 186 and 187: Minimal divergence of tribosphenida
Page 188 and 189: (c) (a) M 1 M 1 M 2 Steropodon M 2
Page 190 and 191: (b) (a) (c) pa.d pr.d me.d Ambondro
Page 192 and 193: crown-group therians) is accepted b
Page 194 and 195: form of the tooth, must reflect sub
Page 196 and 197: of feasibility that a taxon of endo
Page 198 and 199: mammals, by creating environmental
Page 200 and 201: the 11 species of marsupial, of whi
Page 202 and 203: (d) (a) pa A Dasyuromorphia B C pr
Page 204 and 205: earing two huge claws on digits thr
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Page 208 and 209: (b) (d) (a) Glasbius Alphadon (c) D
Page 210 and 211: elieved to be Late Cretaceous in ag
Page 212 and 213: (Fig. 6.5(c)). The dentition exhibi
Page 214 and 215: (d) Figure 6.6 (continued). Thylaco
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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
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Ax, P. 1987. The phylogenetic syste
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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
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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
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Overkill hypothesis 289, 290 Oxyaen
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Tulerpeton 14, 18 Tylopoda 264 Ukha
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The Origin and Evolution of Mammals - Moodle

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