The Origin and Evolution of Mammals - Moodle

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subsequent specimens revealed that there are three premolar teeth and possibly four molar teeth (Butler and Kielan-Jaworowska 1973), which corresponds to the marsupial rather than the placental dental formula, and which led to the group being removed from the Placentalia and placed in the informal category of ‘Theria of the metatherianeutherian grade’. By 1990, Kielan-Jaworowska and Nessov (1990) had come to the conclusion on the basis of the tooth formula, and an incipient tympanic bulla formed from the alisphenoid bone that deltatheroidans are in fact the sister-group of the marsupials, and that the two together should formally constitute the taxon Metatheria. The structure of the molar teeth (Fig. 5.19(b)) does not offer strong support for this conclusion though. In the upper molars, there is a very wide stylar region and a relatively small protocone, and in the lower molars the talonid is much narrower than in typical marsupials. However, these could be specialisations superimposed on a basic marsupial structure for the enhanced shearing action of the teeth of a carnivore. Opposing Kielan-Jaworowska and Nessov’s interpretation, Cifelli (1993c) denied a relationship between Deltatheroida and Marsupialia. He suggested that not only were there no shared molar tooth characters, but also that the other similarities may be primitive for tribosphenidans. The most recent stage in the argument is based on some beautifully preserved material of Deltatheridium (Fig. 5.19(a)), in which Rougier et al. (1998) have shown that the complete dental formula is I4/3: C1/1: PM3/4: M4/4, which confirms a premolar and molar count for marsupials. A second characteristic marsupial feature is the pattern of tooth-replacement, in which only the last premolar is actually replaced after birth; one of the their specimens is a juvenile form that appears to show this was indeed the case. A third is an inflected angular process on the lower jaw, which is characteristic of marsupials. There are also one or two fine details of the anatomy of the braincase supporting the relationship. Minor tribosphenidan groups While the Placentalia, Marsupialia, and Deltatheroida are the three best known and diverse Cretaceous groups of tribosphenidan mammals, there are several other groups known only by their particular THE MESOZOIC MAMMALS 173 versions of the tribosphenic tooth whose relationships both to one another, and to the three wellcategorised groups are unclear (Fig. 5.20). Taken together, these short-lived, minor branches of the tribosphenidan tree have been informally referred to as ‘Theria of the metatherian-eutherian grade’, an expression introduced by Patterson (1956). Historically the most important are the ‘Trinity Theria’, named after the Trinity Formation in Texas, and dating from the Albian stage, at the end of the Early Cretaceous. It was comparison of the ‘Trinity Theria’ with ‘eupantotheres’ which enabled Patterson (1956) to establish that the protocone of the tribosphenic upper molar was a new structure, and not the homologue of any of the triangle of cusps of the molars of pre-tribosphenic molars. Pappotherium (Fig. 5.19(d)) is the best known, being represented by partial jaws along with isolated upper and presumed but not certainly associated lower teeth. Holoclemensia (Fig. 5.19(e)) is similar but known only from upper molars, and Kermackia (Fig. 5.19(f)) is based on a lower molar. Early attempts were made to slot the ‘Trinity Theria’ into existing taxa, notably that of Slaughter (1971), who claimed that Pappotherium was a placental and Holoclemensia a marsupial. However, all subsequent authors have rejected such a simple phylogeny and accept instead that there were several separate lineages of tribosphenidans, most very short-lived, radiating from a hypothetical metatherian-eutherian grade ancestor during the Early Cretaceous (Kielan-Jaworowska et al. 1979b; Clemens and Lillegraven 1986; Cifelli 1993c; Flynn et al. 1999). Other independently evolved molar teeth of no clear affinities are found in the Late Cretaceous, such as Falpetrus (Fig. 5.19(h)) from Wyoming and Bistius (Fig. 5.19(i)) from Mexico (Clemens and Lillegraven 1986). Clearly, the second half of the Cretaceous Period was a time of considerable evolutionary ‘experimentation’ as far as advanced, insectivorous mammals were concerned (Fig. 5.20). Australosphenida and the mystery of the Monotremata The greatest mystery of all concerning mammalian evolution stretches back for 200 years: the question of what exactly the monotreme mammals are, and
174 THE ORIGIN AND EVOLUTION OF MAMMALS how they relate phylogenetically to therians (Musser and Archer 1998). The three living genera of monotremes, Ornithorhynchus (platypus), Tachyglossus (short-beaked echidna), and Zaglossus (long-beaked echidna) of Australasia constitute a monophyletic M 1 M 4 angle (c) (d) (e) (f) Tribotherium Pappotherium (a) Holoclemensia (h) (i) Falpetrus Bistius Kermackia Deltatheridium group supported by several characters such as the low, broad skull, reduced dentition, secondary sprawling gait, and hindlimb spur. From time to time, it has been proposed that the monotremes are the living sister group of the marsupials, most (g) (b) Atokatheridium Figure 5.19 Tribosphenidans of uncertain relationships. (a) Upper and lower views of outline of specimen of Deltatheridium pretrituberculare, showing four molars, and inflected angular process of the lower jaw. Length of lower jaw approx. 3.6 cm (Rougier et al. 1998). (b) Crown views of upper and lower molars of Deltatheridium. (c) Lower molar in crown and lingual views of the basal Cretaceous Tribotherium. (d) Upper molar of Pappotherium. (e) Upper molar of Holoclemensia. (f) Lower molar of Kermackia in occlusal and lingual views. (g) Upper molar of Atokatheridium. (h) Upper molar of the late Cretaceous Falpetrus. (i) Upper molar of The late Cretaceous Bistius (c) (Sigogneau-Russell 1995, (d-g) Kielan-Jaworowska and Cifelli 2001 (h) and (i) Clemens and Lillegraven 1986).
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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
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
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
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
Page 180 and 181: Cretaceous, (Aptian or Albian) of M
Page 182 and 183: eautifully preserved placentals fro
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
Page 196 and 197: of feasibility that a taxon of endo
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
Page 204 and 205: earing two huge claws on digits thr
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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 226 and 227: (f) (g) Wakaleo Diprotodon optatum
Page 228 and 229: fossil mammals, which might help cl
Page 230 and 231: 30 40 50 60 Figure 6.13 Southern Go
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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.
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
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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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