The Origin and Evolution of Mammals - Moodle

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Asioryctes (a) (b) (d) Cimolestes pas st prdg pa me 3 prn 3 6 prd pr 3 4 h (f) 1 med 5 6 end (c) Kennalestes Gypsonictops (e) Barunlestes (zalambdalestid) Parazhelestes Zhelestes Parazhelestes Aspanlestes Zhelestids Figure 7.2 Late Cretaceous placentals. (a) Asioryctes skull in lateral view, and occlusal views of an upper and a lower molar. Skull length approx. 5.4 cm (Kielan-Jaworowska et al. 2000, after Kielan-Jaworowska 1975). (b) Kennalestes skull in lateral view. (c) Upper and lower dentition of Gypsonictops in occlusal view. Approx. length of upper jaw fragment 1.3 cm (Kielan-Jaworowska et al. 1979, after Lillegraven 1969). (d) Cimolestes lower jaw in occlusal and labial views, and upper molars in lingual and occlusal views. Length of fragment of mandible approx. 3 cm (Kielan-Jaworowska et al. 1979, after Lillegraven 1969). (e). Upper molars in occlusal view of four zhelestids, Parazhelestes robustus, Zhelestes temirkazyx, Parazhelestes minor, and Aspanlestes aptap. Approx. width of teeth between 1.5 and 2.0 cm (Nessov et al. 1998 figure 20). (f) Barunlestes. Skull lenght approx. 8.3 cm (Kielan-Jaworowska et al. 2000, after Kielan-Jaworowska 1975).
228 THE ORIGIN AND EVOLUTION OF MAMMALS and Skutschas 2001) and the Mongolian Prokennalestes (Fig. 5.17(c) and (d)) is Aptian or Albian in age, making it perhaps 10 Ma younger still (Kielan-Jaworowska and Dashzeveg 1989). Although it is generally supposed from their early appearance in Asia that this was the area of origin of placentals, Cifelli (1999) described an associated pair of dentaries from the Cloverley Formation of Montana, which is also dated as Aptian-Albian. Montanalestes (Fig. 5.17(e)), as this specimen is named, has a submolariform last premolar followed by only three molars. However, the teeth differ in several respects from Prokennalestes (Fig. 5.17(d)), and until material of upper molars is found, a placental attribution of Montanalestes remains a biogeographically intriguing, but not totally established possibility. Another possible, though even more dubious, very early placental has been described from isolated molar teeth (Fig. 5.19(c)) from Morocco and named Tribotherium (Sigogneau-Russell 1995). It is dated as ?Berriasian, which is the very base of the Cretaceous. The teeth do have some placental characters such as the narrow labial shelf of the upper molar, but lack others such as a third talonid cusp on the lowers. Were Tribotherium actually to prove to be a stem placental, it would be important because it would put the fossil date of divergence of Placentalia from Marsupialia back to at least the start of the Cretaceous around 135 Ma. However, the information available is presently far too sparse to make such an assertion with confidence. During the Late Cretaceous, a radiation of placentals occurred. All remained small in body size, and fairly conservative in dental and, where known, cranial structure to such an extent that there is limited agreement on their classification. Relatively small differences have been used for ordinal and even higher level separation, but had they all been living today most if not all the Late Cretaceous placentals might well have been incorporated into no higher a taxon than a superfamily. At one time it was in fact customary to include them in a single suborder Proteutheria, as a constituent of the order Insectivora (e.g. Romer 1966; Kielan-Jaworowska et al. 1979a). Inevitably, the taxon Proteutheria has long since disappeared from usage due to its manifestly paraphyletic nature, based as it necessarily had to be solely on ancestral dental characters. Kennalestes and Asioryctes from Asia, and Gypsonictops and Cimolestes from North America are among the best-known representatives of the Cretaceous placentals, and the level of taxonomic uncertainty surrounding them is well illustrated by a very brief, recent history of the classification of these four forms. ● In the definitive review of the time, Kielan- Jaworowska et al. (1979a) placed Gypsonictops and possibly Kennalestes in a super-family Leptictoidea. Asioryctes and Cimolestes were placed together in a family Palaeoryctidae that was part of another super-family, Palaeoryctoidea. ● In their comprehensive classification of all mammals, McKenna and Bell (1997) placed Asioryctes into a group basal to most of the placental mammals, Kennalestes and Gypsonictops together in the same family, Gypsonictopidae, of a super-order Leptictida, and Cimolestes in an entirely separate Order Cimolesta. ● Most recently, Kielan-Jaworowska et al. (2004) have associated the two Mongolian genera Asioryctes and Kennalestes in separate families of the same super-order Asioryctitheria. Gypsonictops is classified in a different super-order Insectivora as a leptictidan, and Cimolestes in yet a third super-order Ferae. Many other less comprehensive proposals of relationships concerning these forms have been made over the years, and there have also been a number of suggestions of relationships between specified Cretaceous placentals and particular groups of living mammals, considered later. Irrespective of the disputatious details of possible interrelationships, there are five main groups of Late Cretaceous placentals, the primitive form Asioryctes and its possible relatives, the leptictidans, the zalambdalestids, the sharper-toothed palaeoryctids, and the incipiently bunodont-toothed zhelestids. Asioryctida Asioryctes has been described from about 10 skulls and several fragmentary skeletons from the Coniacian and Campanian of Mongolia and elsewhere in Asia (Fig. 7.2(a)). It has retained several primitive placental characters that are modified in all other known Late Cretaceous forms, including the five upper and four lower incisors that occur in Eomaia
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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
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
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Page 194 and 195: form of the tooth, must reflect sub
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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
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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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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
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Page 262 and 263: continuously growing, and form a gr
Page 264 and 265: navicular facet, 19 or more thoraci
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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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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
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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
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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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