The Origin and Evolution of Mammals - Moodle

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Cretaceous, (Aptian or Albian) of Mongolia. Apart from an isolated molar, Kielantherium (Fig. 5.16(c) and (d)) has been described from a partial lower jaw with the posteriormost four teeth in place. While the full dental formula cannot be determined from this specimen, the similarity of all the preserved teeth to one another suggests that they are all molars. Further forwards there are alveoli for four more teeth, all presumably premolars, and Dashzeveg and Kielan-Jaworowska (1984) argue that these are the second to fifth premolars, with the section of the jaw that housed the first premolar missing. Therefore they proposed that the basic tribosphenidan tooth formula consists of five premolars and four molars. The trigonid of the lower molars is still much the dominant part of the tooth, with a very tall protoconid and the metaconid higher than the paraconid. The relatively small talonid bears only two cusps, but unlike Peramus is in the form of a completed basin. There is a possible candidate for an even earlier tribosphenidan than these. Tribotherium (Fig. 5.19(c)) is known as isolated mammalian teeth of Berriasian age, right at the base of the Cretaceous, from Morocco (Sigogneau-Russell 1995). Aegialodon, Kielantherium, and possibly Tribotherium are placed in the family Aegialodontidae, which accordingly represents the most primitive group of the Tribosphenida, a taxon formally defined by the presence of a protocone on the lingual side of the upper molar working against a basined talonid on the posterior side of the corresponding lower molar. (Luo et al. 2001a; Kielan-Jaworowska et al. 2004) have replaced this name with a new name, Boreosphenida, on the grounds that they have removed a very small number of certain tribosphenid-like taxa and placed them in a completely different group they name Australosphenida, a move not universally accepted yet, and not very good grounds for abandoning a familiar, long-established name. The subsequent evolution of the Tribosphenida involved a complex radiation of mammals (Fig. 5.20), whose teeth show further degrees of enlargement of the protocone and talonid, the addition of minor cusps and crests to various parts of the teeth, and modifications to the primitive dental formula. The precise interrelationships of the several lineages are obscure, particularly because many are still only THE MESOZOIC MAMMALS 169 based on isolated teeth. It is clear that the best known groups of tribosphenidans, namely the placentals (eutherians) and marsupials (metatherians) respectively, represent only two of these lineages, albeit the two that eventually survived into the Tertiary to diverge into the mammalian fauna of today. Other lines evolved independently, survived briefly, and disappeared without further trace by the close of the Cretaceous (Clemens and Lillegraven 1986; Kielan-Jaworowska and Cifelli 2001). Placentalia There is some discrepancy between the use of the respective names Placentalia and Eutheria. McKenna and Bell (1997) regard them as synonyms and prefer the former. Others, particularly Kielan-Jaworowska et al. (2004) discriminate between the two, using Placentalia for the living groups and their fossil relatives, and Eutheria for the more inclusive group consisting of these plus their stem-group. The problem is that the relationships of the various early fossil members to living placentals is far from safely established, and therefore Placentalia in Kielan- Jaworowska et al’s sense may be a paraphyletic group. McKenna and Bell’s terminology is therefore adopted in the present work. Placentals are recognisable from the presence of a semi-molariform last premolar, only three molars, and the cusp pattern (e.g. Fig. 5.17(c)). As described in more detail in a later chapter (page 226), the earliest recorded placental is Eomaia from China (Fig. 5.17(a) and (b)), which is believed to be Barremian in age and therefore 125–130 Ma (Ji et al. 2002). Murtoilestes from Russia (Averianov and Skutschas 2001) is believed to be only 4 or 5 younger, occurring as it does around the Barremian–Aptian boundary. Younger Early Cretaceous placentals occur in Aptian-Albian rocks, in the form of Prokennelestes (Fig. 5.17(c) and (d)) from Mongolia, and probably Montanalestes (Fig. 5.17(e)) from North America (Cifelli 1999). Once into the Late Cretaceous, placentals started to diversify in both Asia and North America, as discussed in detail in a later chapter. Following 40 years on in the footsteps of the celebrated American Museum expeditions of the 1920s (Colbert 2000), Zofia Kielan-Jaworowska and her colleagues collected numerous skulls and skeletons of a range of
170 THE ORIGIN AND EVOLUTION OF MAMMALS (a) (b) (e) P 3 P 4 Montanalestes P 5 P 5 M 1 Eomaia M 3 M 2 M 3 (c) (d) P 4 P 5 P 5 M 1 M 1 Prokennalestes M 2 M 2 M3 Figure 5.17 Early Cretaceous placentals. Eomaia scansoria (a) Lingual and labial views of lower premolars 3–5 and molars 1–3, and internal and external views of lower jaw. Length of jaw approx. 2.3 cm. (b) Reconstruction of skeleton. Presacral length approx. 8 cm (Ji et al. 2002). (c) Occlusal and labial views of upper premolars 4–5 and molars 1–3 of Prokennalestes trofimovi. Length of illustrated tooth row aprox. 0.7 cm. (d) Occlusal and lingual views of lower last premolar and upper molars of the same (Kielan-Jaworowska and Dashzeveg 1989. (e) External and internal views of lower jaw of Montanalestes keebleri. Length of preserved jaw approx. 1.5 cm (Cifelli 1999). M 3
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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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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
Page 140 and 141: elevation of maximum aerobic activi
Page 142 and 143: a mammal. The difficulty with all s
Page 144 and 145: collection, ingestion, and assimila
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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
Page 174 and 175: (a) 1 (b) (d) me (c) me.d 3 styl st
Page 176 and 177: (a) (c) Henkelotherium Crusafontia
Page 178 and 179: pubis is excluded from the acetabul
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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
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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
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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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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
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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
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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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