The Origin and Evolution of Mammals - Moodle

Recommendations

Info

the first one is enlarged, often to the same size as the canine. In the lower jaw, it is the second tooth that is enlarged. Another characteristic concerns the keel on the angular bone of the lower jaw, which extends well below the jaw articulation and so appears strongly convex in outline. A number of postcranial features also characterise the group, such as weak development of the ridges for adductor (c) (d) (a) Haptodus EVOLUTION OF MAMMAL-LIKE REPTILES 25 musculature on the ventral side of the femur (Reisz et al. 1992). Haptodus (Fig. 3.6(a)) is the earliest sphenacodontian, occurring in rocks of Upper Pennsylvanian age in North America and Early Permian in Europe (Currie 1979; Laurin 1993). It is also the most primitive, having the lachrymal bone extending all the way from the orbit to the margin of the external (b) Secodontosaurus Sphenacodon Dimetrodon Figure 3.6 Sphenacodontid pelycosaurs. (a) Skull of Haptodus garnettensis in lateral view (Laurin 1993). (b) Skull of Secodontosaurus obtusidens in lateral view (Reisz et al. 1992) (c) Reconstructed skeleton of Sphenacodon ferox (Romer and Price 1940) (d) Reconstructed skeleton of Dimetrodon limbatus. (Romer and Price 1940).
26 THE ORIGIN AND EVOLUTION OF MAMMALS nostril. The keel of the angular does have the deep form characteristic of the group, but it is not reflected laterally as occurs in other sphenacodontians. The skull is relatively short snouted, and the dentary and incisor teeth only moderately enlarged. Haptodus is also a small form, with a skull length around 10 cm in most species described, although the English species Haptodus grandis may have reached about 28 cm (Paton 1974). All other sphenacodontians can be included in the family Sphenacodontidae (Reisz et al. 1992; Laurin 1993), in which there is a more powerful dentition. The snout is longer, the lachrymal bone shorter, and the maxilla has a strongly convex margin. The canines are very large and all the teeth develop anterior and posterior cutting edges. Dimetrodon (Fig. 3.6(d)) is notorious for its elongated neural spines, presumed to support a sail involved in thermo-regulation in what must be assumed to be an ectothermic animal. Several authors have attempted to model the system and calculate the effect such an increase in surface area would have had, and generally agree that it would have made a very significant difference to the rate of heat exchange with the environment. Possible functional advantages are to achieve more quickly a preferred body temperature in the morning, to lose heat during the day, or to maintain a more or less stable temperature throughout (Bennett 1996). Dimetrodon is abundantly preserved in the Early Permian of North America, and also extends into the beginning of the Late Permian in Texas. Some members of the genus achieved very large body size, with Dimetrodon grandis about 320 cm in body length and a weight estimated by Romer and Price (1940) to be around 250 kg. Sphenacodon (Fig. 3.6(c)) is similar to Dimetrodon but has less strongly developed canine teeth. It also lacks the dorsal sail, although the neural spines of the vertebrae are still quite long. Secodontosaurus (Fig. 3.6(b)) is a specialised sphenacodontid with a low skull and a long, slender snout. The anterior lower teeth are procumbent, and none of the lower teeth are enlarged. Even the upper canine is modest in size. It was long considered to be a secondarily fish-eating animal because of its generally crocodile-like skull. However, Reisz et al. (1992) showed that there was a fully developed dorsal sail which they regard as improbable in a semi-aquatic animal. They proposed instead that it was adapted for catching small tetrapods hiding in crevices and burrows. The origin and early radiation of the Therapsida The San Angelo and overlying Flower Pot Formations of Texas, along with the more or less contemporary Chickasha Formation of Oklahoma represent the final stage of the fossil-bearing Permian sequence in North America. They are dated as Guadalupian, which is equivalent to Middle Permian, and pelycosaurs still occur in the form of herbivorous caseids, Dimetrodon, and also, in the Chickasha, the varanopseid Varanodon. Olson (1962, 1986) claimed that these beds also contain the first fossil record of the more advanced synapsid group Therapsida. The specimens are in fact extremely scarce and consist only of fragments of braincases, vertebrae, and limb bones, and there is considerable doubt about whether any of them at all are actually the remains of therapsids rather than of pelycosaurs, probably caseids (Reisz 1986; King 1988; Sigogneau-Russell 1989). However, approximately contemporaneous continental sediments occur in the cis-Uralian region of Russia (Fig 2.2(a)), referred to as the Kazanian and early part of the Tatarian stages (Sigogneau-Russell 1989; Golubev 2000), and contain undisputed primitive therapsids (Ivakhnenko 2003). They belong to several taxa, existing alongside a few lingering caseid and varanopseid pelycosaurs (Modesto and Rybczynski 2000). The fossil record of therapsids in the South African Beaufort Series also extends downwards to beds equivalent to the early Kazanian, and also yields primitive members of therapsid groups (Rubidge 1995; Rubidge et al. 1995). This fauna is referred to as the Eodicynodon Assemblage Zone. A third area for very primitive therapsids comparable to the previous two has been described in northern China, the Xidagou Formation in Gansu. Although the exact age of these deposits is uncertain, they are presumably approximately the same as the Russian and South African records (Li and Cheng 1995; Li et al. 1996). Thus by about 270 Ma, a therapsid fauna had evolved and expanded its range to encompass Gondwanan as well as Laurasian parts of Pangaea.
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 20 and 21: it means that a 200 Ma igneous rock
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 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.
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 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
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 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
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
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
show all

The Origin and Evolution of Mammals - Moodle

Create successful ePaper yourself

Delete template?

Save as template?