The Origin and Evolution of Mammals - Moodle

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(b) (d) (a) Glasbius Alphadon (c) Didelphodon LIVING AND FOSSIL MARSUPIALS 197 Pediomys Figure 6.4 Late Cretaceous marsupials. (a) Alphadon rhaister upper molars 1–3 in labial and occlusal views; Alphadon lulli lower dentition in occlusal and labial views. (b) Glasbius intricatus upper last premolar and molars 1–3 in labial and occlusal views; lower molars 1–4 in occlusal and labial views. (c) Pediomys elegans upper molars 1–4 in labial and occlusal views; Pedimys hatcherii lower molars 2–4 in occlusal and labial views. (d) Didelphodon vorax lower dentition in occlusal and lingual views; lingual and occlusal views of an isolated 4th molar (Clemens 1979).
198 THE ORIGIN AND EVOLUTION OF MAMMALS are characterised by the lingual shift of the hypoconulid to lie close to the entoconid, the ‘twinned’ condition. Pediomyidae Forms such as Pediomys and Aquiladelphis have more specialised molar teeth (Fig. 6.4(c)), in which the upper stylar shelf is reduced and the trigon basin of the upper and talonid basin of the lower are relatively enlarged at the expense of other parts of the teeth, enhancing somewhat the crushing function at the expense of the shearing. Stagodontidae In contrast to the pediomyids, the stagodontids tended to accentuate the shearing action of the molars (Fig. 6.4(d)), indicating a more carnivorous diet. This was achieved by a definite carnassial notch in the protocristid crest between protoconid and metaconid cusps of the lower molars. The Stagodontidae are best known from Didelphodon, one of the largest of the Mesozoic tribosphenidans, with individual molars about 6 mm in length. Glasbiidae This family is based solely on the genus Glasbius, which Clemens (1966, 1979) originally thought to be a specialised didelphid. It has low, bunodont molars (Fig. 6.4(b)) suitable for a more simple crushing action, suggesting a partially herbivorous diet. They most closely resemble the teeth of the caroloameghiniids, a South American Palaeocene family (page 204). Asian Cretaceous marsupials For many years, Cretaceous marsupial fossils were believed to occur only in North and South America. However, the picture has changed radically on two counts. With one possible, but doubtful exception, the earliest South American rocks yielding marsupial fossils are now believed to be Early Palaeocene rather than Late Cretaceous in age. On the other hand, definite Late Cretaceous marsupials do occur in Asia. Trofimov and Szalay (1994; Szalay and Trofimov 1996) described a virtually complete specimen from the Campanian of Mongolia as Asiatherium (Fig. 5.18(a)). They regard it as the most plesiomorphic marsupial known, primitive in practically all its anatomy, and placed in its own order Asiadelphia. It does, however, possess the twinned entoconid and hypoconulid and other dental characters indicating that it is a more derived marsupial than Kokopellia (Cifelli and Muizon 1997). Even earlier, though far more incomplete material from Uzbekistan has also been attributed to the Asiadelphia by Averianov and Kielan-Jaworowska (1999). Marsasia is dated as Coniacian which makes it about 88 Ma, but unfortunately it is represented so far only by several toothless fragments of lower jaw and one with the fourth molar in place. Although not as old as the Northern American Kokopellia, these specimens dispel any simple view that marsupials originated in North America and were restricted to that continent during the whole of the remainder of the Cretaceous Period. Krause’s (2001) identification of a Late Cretaceous tooth from Madagascar as a marsupial is very doubtful (Averianov et al. 2003), but is a timely reminder that Late Cretaceous mammalian faunas are extremely poorly represented outside North America and Mongolia. Ameridelphia: the South American radiation In stark contrast to the situation in North America, South America was home to a major radiation of marsupials from the Palaeocene onwards, which included all the insectivorous, small omnivorous, and carnivorous mammals until the arrival of certain placental mammals in the later part of the Cenozoic. It is not yet certain exactly when the South American marsupial fossil record begins. Gayet et al. (2001) have recently reported on a Late Cretaceous site, dated as Middle Maastrichtian, from Pajcha Pata in southern Bolivia. Amongst the vertebrate microfossils collected, there are two very poorly preserved tribosphenic teeth, so incomplete that it is impossible to say to which taxa they belong, not even whether or not they are marsupials. They may prove to be australosphenidans, even monotremes, or perhaps further specimens will reveal that they are indeed marsupials, in which case they will be critical for understanding the earliest phase of marsupial history in South America. Apart from the possibility of Pajcha Pata, Laguna Umayo in Peru is the oldest marsupial bearing locality in South America. For a long time it was
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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
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SC PRC p.i.f.i tr.min (c) dp.cr ect
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the therocephalian pelvis and hindl
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spc s.sp s.sp SC PRC (d) delt T AST
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no significant novelties to what ha
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(a) (c) (e) (g) D D ex. au.m C tym
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(a) (c) (d) PMX (f) V n.turb mx.tur
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ol.b (a) (b) cer.hem gorgonopsian t
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(a) (b) (i) (ii) (iii) (iv) (v) a g
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cold stress, the part that usually
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conducted the experiment of wrappin
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mammals themselves that the enlarge
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elevation of maximum aerobic activi
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a mammal. The difficulty with all s
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collection, ingestion, and assimila
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were edaphosaurid and caseid pelyco
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CHAPTER 5 The Mesozoic mammals The
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(a) (d) AL condylar foramina are se
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evidence to relate the haramiyidans
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postcranial skeleton, and Graybeal
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side of the head can be in action a
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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 168 and 169: a self-sharpening property. As the
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
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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
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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
Page 216 and 217: (a) (c) Caroloameghina and Procarol
Page 218 and 219: (a) (e) (d) Proargyrolagus Groeberi
Page 220 and 221: (a) (b) Djarthia Thylacotinga (c) (
Page 222 and 223: LIVING AND FOSSIL MARSUPIALS 211 M
Page 224 and 225: Extinct Notoryctemorphia At present
Page 226 and 227: (f) (g) Wakaleo Diprotodon optatum
Page 228 and 229: fossil mammals, which might help cl
Page 230 and 231: 30 40 50 60 Figure 6.13 Southern Go
Page 232 and 233: the Diprotodontia also included gen
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Page 236 and 237: effectively absent. However, increa
Page 238 and 239: Asioryctes (a) (b) (d) Cimolestes p
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Page 242 and 243: (a) Leptictidium Palaeoryctidans we
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Page 246 and 247: (a) (d) (e) (g) Protoungulatum Meso
Page 248 and 249: (a) (f) (e) Hyopsodus Phenacodus (d
Page 250 and 251: Titanoides (pantodont) (a) (c) (b)
Page 252 and 253: (a) (b) (d) Trogosus (tillodont) Es
Page 254 and 255: Mioclaenus Paulacoutoia (didolodont
Page 256 and 257: 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
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
Page 320 and 321:
(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
Page 332 and 333:
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
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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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