The Origin and Evolution of Mammals - Moodle

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(a) (c) (e) (g) D D ex. au.m C tym refl. lam ang. pr M I STA D ang. pr f.ov eu.tu dep. mand SA tym refl. lam art.pr rart.pr rart. pr tym Q ART coch STA rart. pr hy refl. lam (b) (d) (f) (h) QJ-notch Q-notch fossa incudis ECTO D trochlea EVOLUTION OF MAMMALIAN BIOLOGY 115 D squamosal malleus (articular) petrosal ang. pr tym I axis cr. b M man refl. lam dorsal plate l.f.pro q.r.pt a stapedial recess art.pr ART reflected lamina tympanic membrane b crista parotica tym ECTO dorsal plate stapedial process manubrium b� tympanic membrane trochlea malleus (articular) (retroarticular process) Q rart. pr M I cr. l angular (tympanic) Thrinaxodon angular (tympanic) reflected lamina Morganucodon Figure 4.9 Evolution of the mammalian middle ear. (a) Basic structure of the modern mammalian middle ear. (b) Function of the mammalian ear ossicles as a lever system. The lever arm from the axis of rotation to the manubrium of the malleus in the centre of the tympanic membrane is approximately twice the length of the lever arm from the axis to the crus longis of the incus to which the stapes attaches. (c) Reconstruction of the tympanic membrane in a primitive cynodont such as Thrinaxodon. (d) The same in a eucynodont. (e) The same in a primitive mammal such as Morganucodon. (f) The same, in principle, in a modern mammal. (g) Reconstruction of the internal view of the hind part of the dentary and the postdentary bones in a primitive mammal. (h) Comparison of the sound-conducting system of the cynodont Thrinaxodon and the primitive mammal Morganucodon, showing the basic similarity but change in orientation of the axis of rotation of the quadrate from transverse to longitudinal. ((a) and (b) after Hopson 1966; (c) to (f) after Allin 1975; (g) Allin and Hopson 1992; (h) Luo and Crompton 1994). ang.pr, angular process of the dentary; ART, articular; art.pr, articular process of the dentary; coch, cochlea; cr.b, crus brevis; cr.l, crus longis; D, dentary; dep.mand, depressor mandibuli; ECTO, ectotympanic; eu.tu, eustachian tube; ex.au.m, external auditory meatus; f.ov, fenestra ovalis; hy, hyoid; I, incus; M, malleus; man, manubrium; Q, quadrate; q.r.pt, quadrate ramus of the pterygoid; rart.pr, retroarticular process; refl.lam, reflected lamina of the angular; SA, surangular; STA, stapes; tym, tympanum.
116 THE ORIGIN AND EVOLUTION OF MAMMALS at the jaw articulation that was borne by the quadrate and articular, so allowing them even greater mobility. The great reduction in size of the reflected lamina of the angular of cynodonts, but not its actual loss was always a mystery, but can now be seen to be a reduction to a suitably delicate bone supporting the tympanum without adding excessively to its mass. In the course of a detailed review of the evolution of the quadrate in cynodonts and early mammals, Luo and Crompton (1994) have provided very detailed evidence for the supposed transition. From a primitive condition represented by Thrinaxodon, through a sequence of increasingly advanced forms to the early mammal Morganucodon, there is a reduction in size of the quadrate. This was coupled with a shift in the orientation of its contact with the squamosal, creating an increasingly effective axis for transmitting vibrations between the presumed tympanic membrane and the stapes. Indeed, a direct comparison of their reconstructions of the morphology of this region in Thrinaxodon and Morganucodon shows a remarkable similarity (Fig. 4.9(h)). The final step occurred in later mammals, where the tympanic bone and ear ossicles lost all contact with the dentary bone in the adult, being now supported only by the crista parotica, which is a small process of the periotic bone. They are protected within a partial bony housing formed from the surrounding bones, alisphenoid or periotic. The implication of Allin’s theory for pre-cynodont stages of mammal-like reptiles is that they did not possess a tympanic membrane for sound reception, and therefore had very poor impedance matching for converting air-borne sound waves to waterborne sound waves in the inner ear. In pelycosaurs, the massiveness of the stapes indicates that it still served its primitive function of mechanical support between the braincase and palate. Nevertheless, even at this stage the stapes was associated with an open fenestra ovalis so must have been involved in sound reception. There is no difficulty postulating detection of low-frequency, high-amplitude sound, received via the ground or the side of the skull. It would have been transmitted by intermolecular vibrations within the bony tissue, rather than by vibration of a light, low-inertia stapes. In the gorgonopsians the stapes is lightened by the presence of a very large stapedial foramen, suggesting that a mechanism involving vibration of the bone as a whole had evolved, a mechanism potentially capable of detecting higher-frequency sound. Even so, there is no indication of the presence of a specialised tympanic membrane, so the lower jaw as a whole was probably still the initial sound receptor. Therocephalians do not possess a stapedial foramen, an unexpected and unexplained fact, but certainly not one that suggests acute high-frequency hearing ability in this group. The reflected lamina of the angular of primitive therapsids is large and primarily a site of muscle attachment so any role it may have had as an incipient eardrum would have been at best highly inefficient. Thus the anatomical evidence points to the cynodonts, with their reduced reflected lamina, as the first to develop a dedicated tympanic membrane on the lower jaw. The cochlea of mammals is considerably longer than that of cynodonts, indicating enhanced sensitivity to a range of frequencies (Kielan-Jaworowska et al. 2004). It has become housed within a swollen promontorium on the ventral side of the skull, formed entirely from the periotic bone, a feature which, Luo et al. (1995) suggest, increased the sound insulation of the organ from the surrounding cranial structures. Olfaction Most modern mammals have a very acute sense of smell in terms of range of discrimination and acuity of reception. Little can be inferred about the sense of smell of non-mammalian synapsids, but what signs there are strongly suggest early elaboration of the faculty. In modern mammals, the nasal cavity is large and the area of the olfactory epithelium is greatly increased by thin, bony turbinals extending into it from the roof and sides (Fig. 4.10(a)). The naso-turbinals in the roof, and the ethmo-turbinals in the postero-dorsal region of the cavity are the main olfactory areas; the maxillo-turbinals lying laterally along the course of the airflow through the nasal cavity are associated with mucous epithelium related to the respired air and endothermy, as discussed elsewhere. No turbinal bones as such have been discovered in any non-mammalian synapsid, but fine ridges on the internal surfaces of the nasal and frontal bones are universally present from pelycosaurs onwards (Fig. 4.10(b)–(e)). These are
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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
Page 76 and 77: Although there is no mammal-like co
Page 78 and 79: Cynognathidae Cynognathus (Fig. 3.2
Page 80 and 81: (e) (f) Figure 3.22 (continued). Ma
Page 82 and 83: (c) (d) (a) (b) Kayentatherium EVOL
Page 84 and 85: Pachygenelus (e) (a) (c) Therioherp
Page 86 and 87: palatal, and orbitosphenoid bones,
Page 88 and 89: Wible and Hopson 1993). The interor
Page 90 and 91: published a cladogram based on rece
Page 92 and 93: 310-320 Ma. By this time, the great
Page 94 and 95: are forms such as Casea itself, var
Page 96 and 97: lakes and swamps in the low-lying l
Page 98 and 99: urrowing and subsisting on a diet o
Page 100 and 101: Eothyris Haptodus sphenacodontine B
Page 102 and 103: z (a) (c) a.pt.m. M B PO P P SQ P M
Page 104 and 105: (b) a.pt.m. temp.m. a.pt.m. temp.m.
Page 106 and 107: the dentary bone above the level of
Page 108 and 109: the therocephalian grade was not on
Page 110 and 111: A balance was also achieved in the
Page 112 and 113: Locomotion Ancestral amniote grade
Page 114 and 115: screw-shaped: the front part faces
Page 116 and 117: For the recovery phase, the relativ
Page 118 and 119: SC PRC p.i.f.i tr.min (c) dp.cr ect
Page 120 and 121: the therocephalian pelvis and hindl
Page 122 and 123: spc s.sp s.sp SC PRC (d) delt T AST
Page 124 and 125: no significant novelties to what ha
Page 128 and 129: (a) (c) (d) PMX (f) V n.turb mx.tur
Page 130 and 131: ol.b (a) (b) cer.hem gorgonopsian t
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
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
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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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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
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
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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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The Origin and Evolution of Mammals - Moodle

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