The Origin and Evolution of Mammals - Moodle

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it means that a 200 Ma igneous rock of, say, Upper Triassic when the first mammals appeared may be dated at plus or minus 4 Ma, a significant time in evolutionary terms. Absolute dating of an actual fossil requires that the age of the sediment containing it is assessed relative to available absolutely dated rocks that are close to it in time and space. This often demands such further error-prone procedures as measuring the thickness, and estimating the rate of deposition of the sediments separating the fossil layer and the igneous rock exposure. The International Stratigraphic Chart The relevant parts of the 2000 version of the International Stratigraphic Chart for Phanerozoic time are presented in Fig. 2.1 for reference. It is not always completely consistent with the text that follows because a lot of the literature on synapsids has not been based upon this particular timescale. One of the most prominent inconsistencies is the frequent use by synapsid palaeontologists of a twofold division of the Permian into Early and Late Epochs, compared to the threefold division now adopted, of Lower, Middle, and Upper. Another is the difference between the European-dominated use of Lower, Middle, and Upper Epochs for the Carboniferous, in contrast to the North American twofold arrangement into Mississippian and Pennsylvanian that has been adopted by the international scheme. Classification For all organisms, fossil and living, the first requirement for practically any evolutionary interpretation is a cladistic analysis of their relationships, whether expressed as a cladogram, or as a formal classification of monophyletic groups. A hypothesis of the branching pattern that connects species and taxa allows objective inferences to be made of the pattern and sequence of evolution of characters, and of the biogeographic history of the group. The battles of the 1970s and 1980s over the appropriateness and significance of cladism have long since been won and lost, and the focus has turned from the question of principle to the question of how actually to analyse the huge amounts of information about characters and taxa now available, and requiring ever-more powerful computer and statistical techniques. Morphological characters TIME AND CLASSIFICATION 9 Dealing with the morphological characters of fossils still relies primarily on parsimony, that is to say, the assumption of a model of evolution based on minimum evolutionary change. No other model, for instance one that might make assumptions about different probabilities of change in different sorts of characters, is defensible in the absence of any independent method of measuring such probabilities. Therefore, minimising the total number of inferred evolutionary changes in characters generates the simplest hypothesis of the overall pattern of evolution. Apart from the obvious incorrectness of the assumption of equal probability of change in all characters, morphological analysis suffers from the intractable problem of what constitutes a unit character. That different authors can study exactly the same fossils but then produce different cladograms, sometimes markedly different ones, is mainly due to the unit character issue. As an extreme example, a single mammalian molar tooth could be coded as a single character state such as ‘hypsodont’, or by maybe a dozen characters, one for each cusp or loph. Searching for whether proposed multiple characters are always correlated with one another, and assuming in such a case that they should be treated as a single one, potentially could remove highly informative evidence of relationships, if the characters were in fact independently evolved. This and other problems such as how to assess which characters are homologous with which, how to treat multistate characters, what to do about characters not preserved in some of the specimens, and so on are discussed at length in the literature, for example, by Kitching et al. (1998) and will not be pursued here. But the fact remains that for all the confidence some authors place in their long lists of morphological characters, their application of such programmes as PAUP, and the associated statistical tests for how well the data fits and how robust the cladogram is, there remain major outstanding disagreements between them over several critical parts of the synapsid cladogram. Molecular taxonomy The rise of molecular taxonomy based on sequences of nucleotides in genes has revolutionised the field of classification of living taxa, and nowhere has there
System CARB. PERMIAN Series Texas Leonardian Guadalupian Wolfcampian Virgil. to Desm. White horse Dog. Crk. Flowerpot San Angelo Choza Fm Vale Fm Arroyo Fm. Lueders Clyde Belle Plains Admiral Fm. Putnam Fm. Moran Fm. Pueblo Fm. Cisco Grp. Ma 25 ± 2 266 270 272 275 283 287 295 ± 5 Permian Late Early Triassic Tatarian Isheevo Mezen' Ezhovo/Ocher Kazanian Belebey Santagulova Ufimian Inta Kungurian Artinskian Sakmarian Asselian Mylva Carboniferous Vyatskian Gorizont Severodvinskian Gorizont LOWER TRIASSIC Cynognathus Assemblage Zone Lystrosaurus Assemblage Zone Dicynodon Assemblage Zone Cistecephalus Assemblage Zone Tropidostoma Assemblage Zone UPPER PERMIAN Pristerognathus Assemblage Zone Tapinocephalus Assemblage Zone Eodicynodon Assemblage Zone (a) (b) (c) Figure 2.2 (a) The Permo-Carboniferous stratigraphic sequence of North America. (b) The Permian stratigraphic sequence of Russia (after Modesto and Rybczynski 2000). (c) The Permo-Triassic sequence of Assemblage Zones of South Africa.
Page 2 and 3: The Origin and Evolution of Mammals
Page 4 and 5: The Origin and Evolution of Mammals
Page 6 and 7: Preface This book arose from twin a
Page 8 and 9: For Mal /gosia with love and thanks
Page 10 and 11: Contents 1 Introduction The definit
Page 12 and 13: CHAPTER 1 Introduction There are ab
Page 14 and 15: transversely occluding molar teeth
Page 16 and 17: the Mesozoic mammals, is to do with
Page 18 and 19: a hierarchy of committees under the
Page 22 and 23: een a more fundamental impact than
Page 24 and 25: Table 2.3 Classification of marsupi
Page 26 and 27: (a) (b) (c) humerus radius aquatic
Page 28 and 29: (a) Westlothiana Limnoscelis PO Wes
Page 30 and 31: the ankle bones to form an astragal
Page 32 and 33: (b) (c) (a) Casea rutena Casea broi
Page 34 and 35: (Fig. 3.2(f)), is actually an ophia
Page 36 and 37: the first one is enlarged, often to
Page 38 and 39: Even at their initial appearance in
Page 40 and 41: (a) Nikkasaurus (b) (d) Reiszia (e)
Page 42 and 43: Nikkasauridae The family Nikkasauri
Page 44 and 45: has figured large in discussions of
Page 46 and 47: (c) Figure 3.9 (continued). Syodon
Page 48 and 49: a mixture of progressively more spe
Page 50 and 51: animal with interdigitating, but no
Page 52 and 53: (e) (a) Anomocephalus Ulemica (b) S
Page 54 and 55: mandibulae musculature. This, as in
Page 56 and 57: To date the postcranial skeleton of
Page 58 and 59: ecognised four subgroups, based mai
Page 60 and 61: the presence of a deep, longitudina
Page 62 and 63: collected from the Lystrosaurus Ass
Page 64 and 65: (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.
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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 116 and 117:
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
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(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 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
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
Page 206 and 207:
that contains the independent ances
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) (c) Caroloameghina and Procarol
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(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
Page 262 and 263:
continuously growing, and form a gr
Page 264 and 265:
navicular facet, 19 or more thoraci
Page 266 and 267:
(a) (c) Phosphatherium Numidotheriu
Page 268 and 269:
coexist with other characters that
Page 270 and 271:
The salient feature of Widanelfasia
Page 272 and 273:
1 (a) 1. Perissodactyla 2. Titanoth
Page 274 and 275:
(a) (b) BUNODONTIA or SUIFORMES SUI
Page 276 and 277:
time, which suggests that it was on
Page 278 and 279:
condition. This particular combinat
Page 280 and 281:
etween Primates, Dermoptera (colugo
Page 282 and 283:
have postcranial adaptations for ar
Page 284 and 285:
undoubtedly related at a supraordin
Page 286 and 287:
indisputably to occur prior to the
Page 288 and 289:
The Late Cretaceous mammal record i
Page 290 and 291:
interordinal divergences in the Lat
Page 292 and 293:
diversity on Earth (Janis 1993). Fu
Page 294 and 295:
effect of the surrounding sea. Trop
Page 296 and 297:
was high. It lasted from 5 to 3 Ma
Page 298 and 299:
and thus remain in their preferred
Page 300 and 301:
agreement about exactly when within
Page 302 and 303:
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
Page 318 and 319:
cladogenesis in dasyurid marsupials
Page 320 and 321:
(eds) Evolution of Tertiary mammals
Page 322 and 323:
McKenna, M.C. and Bell, S.K. 1997.
Page 324 and 325:
(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
Page 336 and 337:
Index Note: Page numbers in italics
Page 338 and 339:
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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