The Origin and Evolution of Mammals - Moodle

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(a) (c) Henkelotherium Crusafontia (b) (d) THE MESOZOIC MAMMALS 165 Leonardus Anterior Lingual Figure 5.15 Eupantotherians. (a) Lower jaw of the dryolestid Crusafontia cuencana in lateral and medial views. Length approx. 2 cm. (b) Occlusal view of one upper and two lower molars of a typical dryolestid (Both Krause 1979 from Clemens 1970). (c) Reconstruction of the skeleton and the whole animal of Henkelotherium guimarotae. Presacral length approx. 7 cm (Krebs 1991). (d) Upper molars of the South American dryolestid Leonardus cuspidatus in labial and occlusal views. Length approx. 1 cm (Bonaparte 1990).
166 THE ORIGIN AND EVOLUTION OF MAMMALS One is confirmation of the absence of a broad trough for the postdentary bones, thereby distinguishing spalacotheriids from the more primitive Kuehneotherium, although, as in the latter, there is no angular process on the dentary. The postcranial skeleton of Zhangeotherium has a very modern style of shoulder girdle, with scapula spine and large supraspinatus fossa in front of it. Sigogneau-Russell and Hahn (1995) described isolated teeth of a very peculiar, and very early possible ‘symmetrodontan’. Woutersia (Fig. 5.14(b)) is from latest Triassic, Rhaetian deposits in France. It has the obtuse-angled ‘symmetrodontan’ pattern of main cusps, but also greatly enlarged inner cingulum cusps, a single one on the upper molar, and two on the lower. Woutersia may be the earliest ‘symmetrodontan’ which would be a considerable extension backwards of the time range of the group or, equally likely, an unrelated, specialised holotherian lineage evolved from a Kuehneotherium-like ancestor. At the other end of the timescale, symmetrodontans survived far longer in South America, where isolated molar teeth of Bondesius (Fig. 5.14(c)) occur in the Late Cretaceous Los Alamitos Formation of Patagonia (Bonaparte 1990, 1994). The anterior and posterior cusps and the cingulum are all reduced in size, and their relationships are presently obscure. Shuotherium In 1982, Chow and Rich described a lower jaw of an extraordinary Upper Jurassic mammal from China, which they named Shuotherium (Fig. 5.13(e) to (g)). The jaw is slender, and very reminiscent of that of Kuehneotherium, complete with a well-developed trough that would have housed postdentary bones. There are three premolar and four molar teeth, or four and three respectively, according to Kielan- Jaworowska et al. (2004), and it is the molars that are so remarkable. Each one has a trigonid of three main cusps of normal holotherian form, but in addition there is a large basin extending from the front of the tooth. This resembles remarkably closely the talonid of the tribosphenic lower molars of advanced holotherians, except that there the development is at the back of the tooth. Wang et al (1998) subsequently found what appears to be an isolated upper molar of Shuotherium from the same locality (Fig. 5.13(f)). Not unexpectedly, it possesses a new, large, lingual cusp, which would have occluded with the basin of the corresponding lower molar. Functionally, the molar teeth of Shuotherium had a crushing mechanism between a pseudo-protocone on the upper molar against a pseudo-talonid at the front of the lower, which is analogous to the mechanism in true tribosphenic teeth, but quite independently evolved (Fig. 5.13(g)). Shuotherium teeth have also been identified in the Upper Jurassic of England (Sigogneau-Russell 1998). Few have doubted the therian affinities of Shuotherium, but within that context there has been little agreement in detail because of the combination of uniquely specialised molars with a primitive mandible. Recently, Luo et al. (2002) have raised interest in the genus by proposing that it is related to those Gondwanan tribosphenids, and monotremes that they have somewhat controversially combined as Australosphenida, an issue discussed at more length later (page 178). ‘Eupantotheria’ Traditionally, the group Eupantotheria has been used for those basal therians which had evolved a definite, but single-cusped, un-basined talonid on the back of the lower molar teeth, but lack a protocone on the uppers. As such, these teeth are structurally intermediate between the simpler Kuehneotherium and symmetrodontans on the one hand and the tribosphenids with their fully developed talonid and protocone on the other. There are also several grades within the group. As so constituted, ‘eupantotheres’ are a diverse paraphyletic group. However, as their precise interrelationships are still uncertain, it remains a useful informal taxon. The ‘eupantotheres’ with the least derived dentitions constitute the several families of the Dryolestida (Fig. 5.15(a)). The molar teeth are short from front to back and transversely widened, and the talonid is small (Fig. 5.15(b)). The family Paurodontidae includes the only described complete skeleton of a ‘eupantothere’, Henkelotherium from the Late Jurassic Guimarota mine of Portugal (Krebs 1991). It was a mouse-sized animal (Fig. 5.15(c)) with a remarkably modern postcranial skeleton. The shoulder girdle lacks a procoracoid and interclavicle, has a reduced coracoid, and there is a fully developed supraspinous fossa. In the pelvis, the
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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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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
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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
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Page 178 and 179: pubis is excluded from the acetabul
Page 180 and 181: Cretaceous, (Aptian or Albian) of M
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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
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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
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(f) (g) Wakaleo Diprotodon optatum
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fossil mammals, which might help cl
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30 40 50 60 Figure 6.13 Southern Go
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the Diprotodontia also included gen
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1. Placentalia 2. Edentata 3. Epith
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effectively absent. However, increa
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Asioryctes (a) (b) (d) Cimolestes p
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and Prokennalestes, although it doe
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(a) Leptictidium Palaeoryctidans we
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(a) Purgatorius (c) are part of the
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(a) (d) (e) (g) Protoungulatum Meso
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(a) (f) (e) Hyopsodus Phenacodus (d
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Titanoides (pantodont) (a) (c) (b)
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(a) (b) (d) Trogosus (tillodont) Es
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Mioclaenus Paulacoutoia (didolodont
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their presence. The five orders may
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Xenungulata. Only two Late Palaeoce
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(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
Page 318 and 319:
cladogenesis in dasyurid marsupials
Page 320 and 321:
(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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