The Origin and Evolution of Mammals - Moodle

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The Late Cretaceous mammal record is extremely sparse, with the sole exceptions of North America and Mongolia, and the Garden of Eden hypothesis is that the origins and divergences of the modern placental orders occurred in a part of the world not at present adequately sampled for Cretaceous mammal fossils. The possibilities are the Gondwana continents of Australia, South America, Antarctica, and Africa, in all of which, there is extremely little in the way of Cretaceous fossil mammals. On this view, the early Cenozoic explosive appearance of the modern orders was due to their immigration into the northern continents of Laurasia. The Garden of Eden hypothesis does have some arguments in its favour, principally that the molecular dates of the major divergences within placental mammals coincide approximately with the various phases of the break up of Gondwana. Murphy et al. (2001b) suggested that while the basal placentals (eutherian ancestors) occurred in the northern continents, as indicated by the Early Cretaceous fossil record, the Placentalia origininated in Gondwana (Fig. 7.26(a)). The Afrotheria diverged when Africa separated from the rest of Gondwana about 105 Ma (Smith et al. 1994). Around 5–10 Ma later, according to the molecular dates, the Boreoeutheria differentiated, presumably as a consequence of their ancestor entering North America from South America. At this time, there may have been several small islands that would have offered a route northwards. A second possibility is that the boreoeutherians originated in India, which separated from Africa at about the same time as did South America, becoming another island continent. It is not certain when India eventually collided with Asia (Hallam 1994). Most have believed this to be Late Palaeocene (Krause and Maas 1990; Prothero 1994), but other evidence, including geomorphological and palaeontological, suggests that at least faunal interchange may have been possible a good deal earlier, around the end of the Cretaceous (Jaeger et al. 1989). This hypothesis is consistent with the difficulty of resolving the base of the supraordinal tree, which is due to the very close dates of divergence between Afrotheria, Xenarthra, and Boreoeutheria. The only palaeontological support explicitly claimed for the Garden of Eden hypothesis comes LIVING AND FOSSIL PLACENTALS 277 from Rich et al. (1999; Woodburne et al. 2003), who believe that the Early Cretaceous, 100 Ma Australian mammal jaw Ausktribosphenos is an erinaceid-like member of the Eulipotyphla, and therefore marks the area of origin of placentals. Only more material will confirm or refute this presently highly disputed identification. The Long Fuse hypothesis. The fourth possible explanation for the incongruent dates has been proposed most actively by Archibald and Deutschman (2001). The Long Fuse hypothesis is that most of the Cenozoic orders of placentals did diverge in the Late Cretaceous; that they are in fact represented by known fossils from that time; but that these have been unrecognised because they lack the diagnostic characters of the modern representatives. Rather, they remained small, unspecialised mammals with a basically insectivorous, or at most omnivorous dentition. On this view, the post-Cretaceous explosion of recognisable members of the modern orders was actually their evolution from existing, primitive, stem members. This, the hypothesis implies, occurred in many orders during a small window of time, and was possibly in response to the extinction of the dinosaurs and therefore the release of the habitats and niches from which mammals had hitherto been competitively excluded. In this light, there are several candidates for Cretaceous stemmembership of modern orders. The Leptictida have often been included with the Eulipotyphla (Novacek 1986a), and the Zalambdalestidae interpreted as stem Glires (Archibald et al. 2001). The Zhelestidae possess incipiently ungulate-like molar teeth and could conceivably include stem members of any of the numerous Cenozoic ungulate groups (Archibald 1999). The Palaeoryctida have from time to time been allied to the Carnivora, and also some of the extinct Cenozoic orders such as Creodonta, Taeniodonta, Tillodonta, and Pantodonta. The evidence for all of these putative relationships is certainly not at all strong, often being based almost completely on minor dental similarities, although of course this in itself is a prediction of the very hypothesis. Springer et al.’s (2003) molecular study already referred to (Fig. 7.25) is consistent with the Long Fuse hypothesis, insofar as it places most of the
278 THE ORIGIN AND EVOLUTION OF MAMMALS Eutheria Eutheria Eutheria Eutheria Eutheria Eutheria Placentalia (Boreoeutheria + Xenarthra + Afrotheria) Eutheria Boreoeutheria + Xenarthra Boreoeutheria Xenarthra Afrotheria Afrotheria Eutheria 170 Ma 105 Ma (a) (ii) (iv) (b) (i) Placentalia (Boreoeutheria + Xenarthra + Afrotheria) Eutheria Xenarthra Eutheria Boreoeutheria Boreoeutheria 138 Ma 95 Ma (i) (ii) Afrotheria (iii) Boreoeutheria + Xenarthra Afrotheria 130 Ma 90 Ma (iii) Boreoeutheria 70 Ma Boreoeutheria + Xenarthra Figure 7.26 Two hypotheses of the origin and divergence of placental mammals. (a) Murphy et al.’s (2001b) version of the Garden Eden hypothesis. (b) Archibald’s version of the long-fuse hypothesis. (Archibald 2003).
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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
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(d) (a) pa A Dasyuromorphia B C pr
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earing two huge claws on digits thr
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that contains the independent ances
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(b) (d) (a) Glasbius Alphadon (c) D
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elieved to be Late Cretaceous in ag
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(Fig. 6.5(c)). The dentition exhibi
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(d) Figure 6.6 (continued). Thylaco
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(a) (c) Caroloameghina and Procarol
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(a) (e) (d) Proargyrolagus Groeberi
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(a) (b) Djarthia Thylacotinga (c) (
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LIVING AND FOSSIL MARSUPIALS 211 M
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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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Page 248 and 249: (a) (f) (e) Hyopsodus Phenacodus (d
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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
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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
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Page 286 and 287: indisputably to occur prior to the
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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
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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
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Tulerpeton 14, 18 Tylopoda 264 Ukha
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