The Origin and Evolution of Mammals - Moodle

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(f) (g) Wakaleo Diprotodon optatum (j) Figure 6.12 (continued). Thylacoleo carnifex Ilariidae. This exclusively Middle Miocene group of medium to large herbivores is poorly known (Tedford and Woodburne 1987). It has some superficial resemblances to the Koala, notably the essentially (h) Thylacoleo carnifex Thylacoleo crassidentatus protocone paracone LIVING AND FOSSIL MARSUPIALS 215 protocone Wakaleo aicootaensis protocone (i) paracone paracone Diprotodon selenodont upper molar structure (Fig. 6.12(d)). However, the lower molars in particular are very different from those of Koalas, having retained a recognisably tribosphenic form. M M� M�
216 THE ORIGIN AND EVOLUTION OF MAMMALS Ektopodontidae. Known almost exclusively by its extraordinary teeth (Fig. 6.12(b)), these small animals have at one time or another been taken for multituberculates, or for monotremes. The crown of the relatively huge molar teeth, both uppers and lowers, consists of two transverse rows of up to about nine short, longitudinal crests. Their diet was presumably soft plant material, perhaps fruit, but nothing is really known about their habits or habitat. There is no good argument for a relationship of ektopodontids with any particular diprotodont family, and nor is there anything close to an analogous living tooth structure. They survived right through from the Late Oligocene/Early Miocene into the Early Pleistocene (Woodburne 1987). Pilkipildridae. This family is also very poorly known, being represented only by a few teeth and jaw fragments from Oligocene to Middle Miocene deposits (Fig. 6.12(c)). They were small animals and their dentition combines an enlarged lower-third premolar and low-crowned, basined molars (Archer et al. 1987). The diet was perhaps hard food such as seeds and tough fruit, and a relationship with the petaurids has been tentatively proposed. Miralinidae. The final extinct family to be considered is yet another Miocene group known only from teeth and jaw fragments, from South Australia (Woodburne et al. 1987). In this case there are large, sectorial third premolars, and the molars bear transverse rows of weakly developed cusps (Fig. 6.12(e)). A possible relationship with ektopodontids, whereby miralinids are interpreted as having a primitive version of the former’s teeth, has been suggested. Living families. Of the remaining eight families of diprotodonts usually recognised, two as mentioned have no pre-Holocene fossil record: Tarsipedidae and Acrobatidae. The other six occur from the Oligocene–Miocene to the present day. These are Vombatidae (wombats), Phalangeridae (cuscuses and brush-tailed possums), Burramyidae (pygmy possums), Macropodidae (kangaroos), Petauridae (gliders and ring-tailed possums), and Phascolarctidae (koalas). An overview of marsupial evolution The history of the marsupial mammals, like that of any other large taxonomic group, involved a complex interplay between biogeographic and ecological opportunities on the one hand and the evolutionary potential to adapt to a particular variety of habitats and niches on the other. Some of these factors can be determined from the fossil record that has just been described, and others from what is known of the biology of the living members. Time and place of origin The marsupials are one of the several lineages of tribosphenidan mammals that appeared in the Early Cretaceous, most of which were short-lived. Identifying either the time or the place of origin of a taxon is notoriously difficult because of the stratigraphic and the biogeographic incompleteness of the fossil record, and because diagnostic morphological characters do not necessarily evolve at the same time as lineages separate. In most cases concerning mammals, dates of divergence based on molecular sequences are consistently much earlier than the latest dates indicated by the fossils, and until recently this case was no exception. The oldest fossil identifiable as a stem group marsupial is about 125 Ma, from the Barremian of China. Both Kumar and Hedges (1998) and Penny et al. (1999), using different molecular data, placed the marsupial– placental divergence at about 170 Ma, which is Middle Jurassic, and would imply a long ‘ghostlineage’ of missing fossils. However, a more recent analysis by Springer et al. (2003) using a far larger molecular database, estimated the divergence date between 102 and 131 Ma, which is perfectly compatible with the fossil date. From the information that is currently available, the simplest hypothesis is that marsupials arose from a stem-member that had dispersed from an ultimate Asian origin into North America in the Early Cretaceous. This would account for the existence of the stem marsupial Sinodelphys very early on in Asia, but the vastly greater diversity of Marsupialia in North America during the Late Cretaceous, compared to the one or two sporadic occurrences recorded in Asia for the whole of the Late Cretaceous. Unfortunately, Early Cretaceous
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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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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
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
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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
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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
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cladogenesis in dasyurid marsupials
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(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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