Upload
faisal-ali-anwarali-khan
View
1.841
Download
1
Tags:
Embed Size (px)
Citation preview
STH 2083 Vertebrate BiologyFaisal Ali Anwarali Khan, PhD
Department of ZoologyFaculty of Resource Science and Technology
Universiti Malaysia Sarawak
This OpenCourseWare@UNIMAS and its related course materials are licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
Vertebrate BiologySTH2083
Mammalogy
By
Faisal Ali Anwarali Khan, PhD
Introduction to Mammals
Mammalian diversity
General feature of mammals
Major mammalian skull and skeleton
Mammalian classifications
Brief introduction to mammalian order
Mammals are diverse?
• 29 Extant Orders• 153 Families• 1230+ Genera• 5,500+ Species
Wilson and Reeder 2006. Mammalian Species of the World. Johns Hopkins University Press.
How about other vertebrates?• Amphibians• Reptiles• Birds• Fish
7,000 species8,950 species10,000 species25,000 species
• >350,000 described plants• >1,000,000 described insects
However…… Geographically: Mammals are the most
widespread
Morphologically diverse group of vertebrates
Largest range of body sizes Smallest: Etruscan shrew or bumblebee bat, 2 g Largest terrestrial: African elephant, 6 metric
tonnes = 6 million g Largest vertebrate: Blue whale, 103-150 tonnes
= 150,000,000 g (75 million shrews!)
Typical Terrestrial
Truly volant – True flight
Truly subterranean-Underground
Semi-aquatic
Mostly aquatic
Truly aquatic
Who came first? Mammals or Dinosaurs
Oldest dinosaur fossil
(240 MYA):
Nyasasaurus
Oldest mammals
(form) fossil (225 MYA)
Both Late Triassic
Actually, aboutthe same time....
160 million-year-old fossil—the earliest known complete skeleton of a multituberculate—named Rugosodoneurasiaticus, a fast-running, agile omnivore similar to a modern-day African dormouse. -
Relationships: Mammals and other Vertebrate
1. Mississippian, (>320 MYA) : Reptiles diverged from amphibians - development of amniotic egg
2. Early Permian, (300 MYA) : Appearance of dominantterrestrial predators, pelycosaurs
Mid Permian (270 MYA): Radiation of mammal-like reptiles lineage, Therapsids
3. Mid Permian: Reptilian lineages (crocodiles, turtles, lizards, snakes, dinosaurs) and birds 1
23
4
5
6
1
23
4
5
6
4. End of Permian : Mostly extinct except Cynodonts that give rise to earliest true mammals.
Cenozoic: “The Age of Mammals”
Mesozoic (251 MYA): Dominated by dinosaurs, modern mammals (Therians) is only one of severallines of mammaliaformes
5. Cretaceuos (125 MYA): Therians diverge intoEutherians (placentals) and Metatherians (marsupials)
6. End of Cretaceous-Tertiary boundary (66 MYA): Extinction of dinosaurs, and radiation of mammals
Permian–Triassic extinction event90% species extinct
Ordovician–Silurian extinction eventsSecond largest /Marine life lostMovement of Gondwana
Cretaceous–Paleogene (K–Pg) extinction event3/4 plant and animal extinct
Triassic-Jurassic extinction eventLand and ocean / Asteroid
Late Devonian extinction eventMarine life lost / Sea level
Mammalian Characteristics Endothermic homeothermy: produces heat
metabolically instead of absorbing it fromenvironment, regulates body temp at astable level*
Lactogenic: produces milk to feed young Viviparous: live birth* Hirsute: epidermis has hair* Three Ear bone (Incus, Malleus, Stapes)
Other too....
Selected skeletal features -cranial
What are the major changes in the skull?
How about hearing?
What are the improvement
Selected skeletal features -cranial
• Stronger jaw structure(single bony element in lower jaw = dentary; stronger, simpler jaw articulation between dentary andsquamosal bones)
• Improved hearing(3 ear ossicles = malleus, incus,stapes; tympanic bone supportstympanic membrane)
The homologous bones in mammalsReptile Mammal
Middle ear Stapes StapesQuadrate Incus
Lower jaw Articular MalleusAngular Ectotympanic
Secondary hard palate(more efficient air flow,allows breathing whileeating, suckling)
Skeletal - cranial
Specialized teeth (restricted tomargin of jaw, diphyodont,thecodont, generally heterodontand multicuspidate; process foodbetter = improved mastication)
1. Diphyodont: 2 generations (not always true!) 1 set of Deciduous and 1 set of permanent teeth
2. Heterodont: division of labour, specialized morphologies (not always true!)
3. Thecodont: sunk in sockets
Skeletal - cranial
Mammalian teeth:
Loxodonta(African elephant)
Tusks: incisors or canines?
Odobenus (walrus)
Babyrousa (babirusa)Moschus (musk deer)
• 5 zones of vertebralcolumn (cervical, thoracic, lumbar, sacral, caudal)
• Double occipitalcondyles plus atlas/axis complex (reduces stresson spinal column whilepermitting flexion and extension [atlas] androtation [axis], finer control of headmovements)
Selected skeletal features - axial
Axial skeleton• Thoracic ribs only
(no cervical orlumbar ribs; lighter skeleton, moreflexible movement ofspine)
• Zygapophyses onvertebrae (strengthensvertebral columnwhile permittingflexion/extensionand torque)
Selected skeletal features -appendicular
• Epiphyses on long bones(allows development of well-formed joints)
• General trend to decreasecomplexity and number ofbones in various functional units of skeleton (Esp. pectoral girdleand pelvis; less energy requiredfor development and maintenance of skeleton, lighterframe for quicker movement)
• 4-chambered heart (improved circulation, betteroxygen delivery)
• Enucleated red blood cells (carry moreoxygen)
• Highest concentration of mitochondria(supports higher metabolic rate)
• Large complex lungs, muscular diaphragm (enhanced breathing, gas exchange rate)
Selected non-skeletalcharacteristics
Selected non-skeletalcharacteristics• Masseter muscles associated
with jaw (new set of muscles inmammals for greater control ofjaw movements)
• Enlarged neopallium(cerebral hemispheres ofbrain, greater coordinationand learning ability = larger, more complexbrain)
Sustained energy production...all of these features did not evolve independently!
More or less related to a general trend for a greater capacity for sustained energy production (including acquisition and processing), which is essential for endothermic homeothermy at high body temperatures, and high levels of activity.
Mammals need about 10X more energy (food andoxygen) than a reptile of the same mass.