The Origin and Evolution of Mammals - Moodle

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(Fig. 6.5(c)). The dentition exhibits the characteristics of the family Didelphidae, including a fully expressed V-shaped centrocrista. Pucadelphys was part of an extensive radiation of small didelphid opossums well under way during the Palaeocene; there are four or five Tiupampan genera, and Itaboraí has yielded nine (Marshall et al. 1997). During the Eocene and Oligocene there was a marked decline in didelphid diversity although this is due at least in part to the relatively few fossil-bearing localities yet unearthed for this period of time (Flynn and Wyss 1998). From the mid-Miocene onwards, the known diversity increased, reaching its maximum at the present day. Didelphids have also been reported from Antarctica, in the Eocene La Meseta Formation of Seymour Island (Reguero et al. 2002). Furthermore, they are the only marsupials to have appeared in the northern continents and Africa during the Cenozoic. The very generalised Peradectes, and various closely related genera, occur sporadically until the Miocene in deposits in North America, Europe, Asia, and Africa, although never diversifying, or contributing a particularly significant part of the mammalian faunas of those areas. One noteworthy European occurrence is in the Eocene Lagerstätten of Messel in Germany of completely preserved specimens (Koenigswald and Storsch 1992). Shortly afterwards they disappeared from the Old World (Zeigler 1999) and didelphids remained exclusive to South America until the secondary invasion of Central and North America during the Plio- Pleistocene, when they participated in the northern dispersion during the Great American Biotic Interchange (page 285). The Sparassocynidae is the only other family of didelphimorphs usually recognised, and it consists solely of the genus Sparassocynus, a Miocene and Pliocene taxon (Reig et al. 1987). While the molar teeth are basically similar to those of typical didelphids, including the V-shaped centrocrista, they have been modified for more specialised carnivory (Fig. 6.5(d) and (e)). Both the protocone and the talonid are reduced and carnassial crests have evolved. Sparassocynids possess a curiously specialised ear region with a highly expanded tympanic bulla and a very large ectotympanic sinus above the middle ear, of unknown functional LIVING AND FOSSIL MARSUPIALS 201 significance. The palatal vacuities are lost. The relationships of Sparassocynus have long been debated, including the suggestion at one time that they are related to borhyaenoids. However, they are now generally regarded as aberrant didelphimorphs with certain features converging on those of the borhyaenids (Reig et al. 1987), and worthy of their own family status. Sparassodontia (Borhyaenoidea) This is an entirely extinct order containing the specialised carnivorous marsupials of South America, some of which achieved the size and extremes of adaptation found in the larger placental felids. The molar teeth are specialised for shearing. In the upper molars, the centrocrista is straight, in contrast to the dilambdodont V-shape of the didelphimorphs. The protocone and the stylar region are reduced, while the metacone and postmetacrista expanded, which tends to create a longitudinal, carnassial cutting edge. In the lower molars, the posterior part of the tooth, metaconid and talonid, are reduced. There are also well-defined sparassodont cranial characters, such as the absence of a palatal vacuity, and postcranial skeletal characters such as reduced epipubic bones, and details of the ankle structure (Marshall 1978). Discovering the origin and relationships of this group has been made difficult by the convergent development of carnivorous adaptations of the teeth in other predominantly carnivorous marsupial taxa. At one time it was believed that sparassodonts were related to the thylacines of Australia, despite the fairly obvious superficiality of the similarities in tooth and limb structure. Another, more carefully considered view was that sparassodonts were the sister group of the Cretaceous North American stagodontids (page 198), but this was necessarily based solely on details of molar morphology, since no skull or postcranial skeleton of a stagodontid has yet been found. One of the most interesting possibilities is the view of Marshall and Kielan-Jaworowska (1992) that sparassodonts are the most basal group of marsupials, with plesiomorphic similarities to the deltatheroidans. As described earlier (page 171), Deltatheroida is a Late Cretaceous group of Asian and North American tribosphenidans that may be the sister group of all marsupials. Others disagree.
202 THE ORIGIN AND EVOLUTION OF MAMMALS (b) (c) Callistoe Figure 6.6 Sparassodontians (borhyaenoids). (a) Mayulestes skull in dorsal, ventral, and lateral views, postcranial skeleton, upper molar in occlusal view and lower molars in occlusal and lingual views (Muizon 1998). (b) Skull and lower jaw of Callistoe vincei. Length of skull approx. 24 cm (Babot et al. 2002). (c) Cladosictis skull. Length approx. 13 cm (Savage and Long 1986, after Sinclair). (d) Thylacosmilus skull. Length approx. 20 cm (Carroll 1988, after Riggs). (e) Skeleton and reconstruction of Prothylacinus patagonius. Body length approx. 65 cm (Carroll 1988, after Sinclair, and Marshall 1980). (a) Mayulestes Cladosictis
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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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the lower molars is relatively high
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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
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 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
Page 234 and 235: 1. Placentalia 2. Edentata 3. Epith
Page 236 and 237: effectively absent. However, increa
Page 238 and 239: Asioryctes (a) (b) (d) Cimolestes p
Page 240 and 241: and Prokennalestes, although it doe
Page 242 and 243: (a) Leptictidium Palaeoryctidans we
Page 244 and 245: (a) Purgatorius (c) are part of the
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
Page 258 and 259: Xenungulata. Only two Late Palaeoce
Page 260 and 261: (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
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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
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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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