The Origin and Evolution of Mammals - Moodle

Recommendations

Info

time, which suggests that it was on its shores that Cetacea originated (Thewissen 1998; Gatesy and O’Leary 2001). These early whales are referred to as the Archaeoceti, which is probably a paraphyletic group because it is based on ancestral characters. The dentition is relatively differentiated, and includes molar teeth recognisable as modified ungulate in form. Hindlimbs are still present to various degrees, which casts light on both the relationships, and the mode of evolution of these most highly specialised of mammals. The earliest specimen yet collected is of Himalayacetus, from the 53 Ma Early Eocene of northern India (Bajpai and Gingerich 1998). Unfortunately it consists only of a fragment of lower jaw with the second two molar teeth in place, and nothing at all is known of its postcranial skeleton. The 5 Ma younger pakicetids are reasonably well known and they possess the least modified and therefore the most terrestrially adapted of whale skeletons. Pakicetus (Fig. 7.21(c)) is identifiable as a cetacean from the structure of the braincase and ear region, and various features of the cheek teeth such as reduction of the paraconid and metaconid, and presence of only a single talonid cusp of the lower molars. Most spectacular, however, is the postcranial skeleton, which was still fully adapted for terrestrial life (Thewissen et al. 2001). Pakicetus was about the size of a wolf, with full length, slender limbs of terrestrial ungulate proportions and unmodified pectoral and pelvic girdles. The vertebrae are variable in size, and the zygapophyses indicate a stiff thoracic and lumbar column, as in modern cursorial ungulates. This structure of the skeleton, and the absence of fisheating adaptations of the dentition, or a specialised aquatic ear suggest that Pakicetus was no more adapted for an aquatic habitat than many terrestrial ungulates. Other archaeocetes had become adapted for an amphibious mode of life. The Middle Eocene Ambulocetus (Fig. 7.21(d)) had reduced limbs, but they were still large enough to support the body weight on land, and the pelvis was attached to the vertebral column (Thewissen et al. 1994, 1996). However, the feet were large and could probably have paddled effectively, and though there was a normal tail so could not have been a tail fluke, the LIVING AND FOSSIL PLACENTALS 265 structure of the vertebral column indicates that it was capable of extensive dorso-ventral flexion and extension. The protocetid genera Artiocetus (Fig. 7.21(a)) and Rodhocetus (Fig. 7.21(e)) had comparable sized limbs to Ambulocoetus, but larger fore and hind feet, which were probably webbed (Gingerich et al. 2001). Like Ambulocetus, they would still have been able to move on land, but very clumsily and presumably more infrequently, after the style of a modern seal. Basilosaurus (Fig. 7.21(f)) is a Middle Eocene Egyptian whale, in which a minute hindlimb is still present (Gingerich et al. 1990). The individual bones are recognisable, although several of them have fused. The tiny pelvis, like that of modern whales, has lost its attachment to the vertebral column. The forelimb is also small, and could only have functioned in the control of undulatory swimming. Thus, Basilosaurus must have possessed a tail-fluke, and the modern mode of cetacean locomotion had finally evolved. The subsequent fossil history of cetaceans is relatively uncontroversial (Uhen 1998). The radiation from the Middle Eocene onwards of the basilosaurid whales includes the origin of the two modern groups, Mysticeti (baleen whales) and Odontoceti (toothed whales). Both appear as fossils in the Oligocene, and share numerous characters indicating their monophyly. The limbs of the primitive archaeocete whales possess the artiodactyl structure (Fig. 7.21(b)). Even the highly reduced hindlimb of Basilosaurus can be seen to be paraxonic in structure, although it is too modified to reveal whether it had evolved from a fully artiodactyl form, or is consistent with an origin from the more primitive, mesonychid ankle (Gingerich et al. 1990). However, the much less reduced, and still functional ankle joints of the other genera have the trochleated facet of the astragalus for the navicular, and the unique arrangement of the astragalus–calcaneum joint that unambiguously define Artiodactyla (Rose 2001). Furthermore, the principal axes of the feet are clearly distinguishable. In the forefoot, the third digit is the largest, indicating a mesaxonic type of foot. In the hindfoot, the third and fourth digits are equally large, which is the paraxonic
(a) Artiocetus (c) (d) (e) (f) Pakicetus Ambulocetus Rodhocetus Basilosaurus (b) I II tib nav III NAV AST CALC CUB II V IV III IV V V IV III Figure 7.21 Limbed cetaceans. (a) Skull of Artiocetus. Length approx. 57 cm (Gingerich et al. 2001). (b) Astragalus of Artiocetus and complete manus and pes of Roodhocetus (Gingerich et al. 2001). (c) Skeleton of Pakicetus. Estimated presacral length 1.1 m (Thewissen et al. 2001). (d) Skeleton of Ambulocetus. Presacral length approx. 2 m (Thewissen et al. 1996). (e) Restoration of the skeleton of Rodhocetus. Maximum length approx. 2.75 m (Gingerich et al. 2001). (f) Skeleton of Basilosaurus, with enlarged view of hind limb (Gingerich et al. 1990). AST, astragalus; CALC, calcaneum; CUB, cuboid; FEM, femur; FIB, fibula; NAV, navicular; nav, articulation surface for navicular; TIB, tibia; tib, articulation surface for tibia. II TIB FEM FIB
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 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.
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 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?