The Origin and Evolution of Mammals - Moodle

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(a) (b) (d) Trogosus (tillodont) Esthonyx (tillodont) Uintatherium (dinoceratan) (c) (e) Prodinoceros (dinoceratan) Gashatostylops (arctostylopidan) Figure 7.9 Tillodonts, dinoceratans, and arctostylopidans. (a) Skull of the tillodont Trogosus. Length approx. 30 cm (Carroll 1988 after Gazin). (b) Upper dentition of the tillodont Esthonyx in occlusal view (Savage and Long 1996 after Gazin). (c) Skull of the dinoceratan Prodinoceros. Length of skull approx. 45 cm (Lucas and Schoch 1998b after Flerov). (d) Uintatherium skeleton and occlusal views of upper and lower dentition. Height at shoulder approx 1.6m (Carroll 1988 after Gregory 1957, and Romer 1966). (e) The arctostylopidan Gashatostylops skull in lateral view. Length of restored skull approx. 4 cm (Cifelli and Schaff 1998).
242 THE ORIGIN AND EVOLUTION OF MAMMALS are molarised and the cheek teeth have a welldeveloped and characteristic bilophodont form. Until quite recently (Prothero et al. 1988), dinoceratans were believed to be ungulates related to the paenungulate group of elephants, hyraxes, and sirenians, a view based on a number of ambiguous postcranial characters. Lucas (1993) has, however, argued the case for a sister-group relationship with the Pyrotheria, which is an exclusively South American, Eocene order. He notes a number of detailed similarities in the molar teeth. Dinoceratans, particularly the more advanced uintatheres, must have been browsing forms with a rhinoceros-like mode of life. The loss of the upper incisors suggests that a mobile proboscis was present. Why such apparently uniquely adapted forms should have gone extinct as early as they did is mysterious; they had no obvious direct competitors. Arctostylopida Arctostylopidans are small, rabbit-sized, and exclusively Late Palaeocene mammals. All are Asian apart from the single North American genus, Arctostylops (Fig. 7.9(e)). Little more than dentitions are known for the group, which are characterised by the even size of all the teeth, including reduced canines and molarised premolars. Lophs are developed on the molars, which develop as longitudinal shearing edges. They were, perhaps, comparable in feeding habits to the modern day hyraxes. Several authors had placed arctostylopidans as a basal group of the South American ungulate order Notoungulata, but Cifelli et al. (1989; Cifelli and Schaff 1998) have argued that the dental similarities are superficial and probably convergent. Thus their affinities are at present unclear. Meridiungulata: South American Ungulates One of the more remarkable features of the whole placental fossil record is the revelation of a great radiation of advanced ungulates in South America, from the Early Palaeocene right through until the Plio- Pleistocene, 60 million years later. Five orders are recognised, mostly restricted to that continent although their presence in the Eocene of Antarctica (Reguero et al. 2002), and the dispersal of a few into North America towards the end of their existence are recorded. All have the fundamental ungulate characteristics of large, grinding, lophodont premolar and molar teeth, and fully hoofed feet. McKenna (1975) formalised the commonly held view that all five orders constitute a monophyletic group, by creating a super-order Meridiungulata, and there has been fairly general acceptance of the concept, despite the lack of clearly defined characters supporting it. However, the issue has become complicated by Muizon and Cifelli’s (2000) cladistic analysis of dental characters that supports a relationship between the Early Palaeocene Tiupampan ‘condylarths’ such as Pucanodus, the North American mioclaenid ‘condylarths’ (Fig.7.10(a)), the South American didolodontids (Fig. 7.10(b)), which are advanced ‘condylarths’, and the Meridiungulate order Litopterna (Fig. 7.10(c) and (d)). The implication to be drawn is that a mioclaenid entered South America from the North around the start of the Palaeocene, and radiated into the somewhat more progressive didolodontids, and the fully ungulate litopterns. None of the other four Meridiungulate orders can be shown to belong to this same group, although neither is there strong evidence that they do not. They all have teeth too specialised to reveal their relationships clearly, and therefore any of them could have originated from a different ‘condylarth’ grade ancestor. Indeed, on the basis of certain details of tooth structure, Schoch and Lucas (1985; Lucas 1993) proposed that the two of the Meridiungulate orders, Pyrotheria (Fig. 7.10(g)), and Xenungulata (Fig. 7.10(h)), are related to the Dinocerata of the northern continents (Fig. 7.9(d)), and referred to this grouping as the Uintatheriomorpha. They then claimed that these uintatheriomorphs are related to the anagalidans (Fig. 7.4(a)), a group of small omnivores/herbivores from the Asian Palaeocene. If true, the relationship would imply that there was a second, independent immigration into South America from Laurasia of a progenitor of ungulate taxa, this one not even a ‘condylarth’. For the time being, the Meridiungulate hypothesis that all five orders of South American ungulates form a monophyletic group that could have been derived from a single dispersal of a mioclaenid-like ancestral ‘condylarth’ cannot be satisfactorily refuted and therefore remains the simplest explanation for
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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
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adjacent lower molars. A small exte
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(a) (b) (d) P4 P4 Plagiaulax P4 Pau
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American Morrison Formation genus C
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a self-sharpening property. As the
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near parasagittal gait (Fig. 5.11(e
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pass through the birth canal. Relat
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(a) 1 (b) (d) me (c) me.d 3 styl st
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(a) (c) Henkelotherium Crusafontia
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pubis is excluded from the acetabul
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Cretaceous, (Aptian or Albian) of M
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eautifully preserved placentals fro
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subsequent specimens revealed that
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Minimal divergence of tribosphenida
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(c) (a) M 1 M 1 M 2 Steropodon M 2
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(b) (a) (c) pa.d pr.d me.d Ambondro
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crown-group therians) is accepted b
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form of the tooth, must reflect sub
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of feasibility that a taxon of endo
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mammals, by creating environmental
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the 11 species of marsupial, of whi
Page 202 and 203: (d) (a) pa A Dasyuromorphia B C pr
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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 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
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Page 232 and 233: the Diprotodontia also included gen
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Page 236 and 237: effectively absent. However, increa
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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 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
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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
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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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