Presentation on theme: "Mammalian trends Endothermy Sensory specializations"— Presentation transcript:
1Mammalian trends Endothermy Sensory specializations Heterodont dentitionSkeletal simplificationDentary/squamosal jaw jointLactation and increased parental careSee Table 2.2 for a longer list of diagnostic characteristics.
2Mammalian SkinAdapted from Romer, A. S., and Parsons, S. T. The Vertebrate Body. Saunders, 1977.
3Skin GlandsSweat glandsSebaceous glandsScent and musk glands
4Mammary GlandsAdapted from Hildebrand, M. Analysis of Vertebrate Structure. John Wiley & Sons, 1974.
5Mammary Glands Glandular ducts Teat, nipple, or hair tufts Under endocrine controlLactation and suckling promote social bondsMilk composition variesSeal milk has 12 times the fat and 5 times the protein of cow milk
6Hair Dead epidermal cells with keratin Outer layer of cuticular scales Deeper cortex and medulla layersColor determined by pigments (melanin)Pelage—coat of hairProvides insulationMay undergo seasonal molting
7FIGURE 03: Structure of a guard hair and cuticular scale patterns of the guard hairs of some mammals Adapted from Teerink, B. J. Hair of West-European Mammals: Atlas and Identification Key. Cambridge University Press, 1991.
9Pelage coloration Countershading Camouflage Disruptive coloration Zebra stripesWarning colorationSkunksIntraspecific communicationFIGURE 04: The pattern of postjuvenile molt in the golden mouse (Ochrotomys nuttalli)Adapted from Linzey, D. W. and Linzey, A. V., J., Mammalogy. 48 (1967):
14Fat and Energy Adipose tissue Desert or temperate zone mammals Energy storageSource of heat and waterThermal insulationDesert or temperate zone mammalsStore fat in tail or abdomenBoreal or arctic mammalsSubcutaneous layer of blubber
15Circulatory System Endothermy requires highly efficient circulation Systemic and pulmonary circuits4-chambered heartBiconcave red blood cellsHeart rate varies with:body sizeactivity state (e.g. hibernation)
16FIGURE T03: Heart Rates of Selected Mammals Circulatory SystemFIGURE T03: Heart Rates of Selected MammalsData are from Altman and Dittmer (1964: 235); names updated.
17Respiratory System Trachea—bronchi—bronchioles—aveolar ducts—alveoli Human lungs contain ~300 million alveoli or 70 m2 of respiratory surface areaMuscular diaphragm aids ventilationLimb and body movements also assist
18Reproductive System Females Both ovaries functional Ova fertilized in uterine tubesAdapted from Smith, H. M. Evolution of Chordate Structure. Holt, Rinehart, and Winston, 1960.
19FIGURE 08: Ventral view of penises of New Guinean murid rodents MalesErectile copulatory organ—penisOs penis or baculum variableTestes usually held in scrotumFIGURE 08: Ventral view of penises of New Guinean murid rodentsAdapted from Lidicker, W. Z., Jr., J. Mammalogy 49 (1968):
21FIGURE 09: Left sides of the brains of a hedgehog and a dolphin Neopallium highly developedCorpus callosum presentBrainFIGURE 09: Left sides of the brains of a hedgehog and a dolphin(Hedgehog) Adapted from Romer, A. S., and Parsons, S. T. The Vertebrate Body. Saunders, 1977; (dolphin) adapted by Norris, K. S. Whales, Dolphins and Porpoises. University of California Press, 1966.
22FIGURE 10: Cutaway view of the nasal chamber of an Abert’s squirrel Sense OrgansOlfactionOlfactory receptors distributed across the mucosal surfaces of the mesethmoid and vomeronasal organ areasFIGURE 10: Cutaway view of the nasal chamber of an Abert’s squirrel
23Hearing High acuity (especially in nocturnal mammals) Sound use in: CommunicationOrientation to environmentLocating foodAvoiding enemiesInfrasound to ultrasoundExternal pinna leads to external auditory meatusMiddle ear has three ossicles encased in bony bulla
24Middle earFIGURE 11: Lateral view of the right middle ear chamber (anterior is to the right) of Abert’s squirrel, with the auditory bulla largely removed
25Other Senses Vision Tactile Similar to other amniotes Tapetum lucidum in nocturnal mammalsRetina with photoreceptors (rods and cones)Rods enable vision in low light (grayscale)Cones enable color vision in brighter lightEyes reduced in some fossorial mammalsTactileVibrissae on muzzle (mystacial pad)
26Digestive System Salivary glands Simple esophagus Stomach simple or complexMulti-chambered in many herbivoresSite of microbial fermentation in ruminantsCaecumMay be site of microbial digestion
27FIGURE 13: The four-chambered “stomach” of a ruminant artiodactyl Digestive SystemFIGURE 13: The four-chambered “stomach” of a ruminant artiodactylAdapted from Storer, T. L., and Usinger, R. L. General Zoology. McGraw-Hill, 1965.
28Muscular System Limb muscles highly adapted to style of locomotion Trunk muscles aid postural control and breathingSuperficial muscles allow skin to moveAssist in sucklingFacial expressionEar movements
29The Skeleton Simplification of skeletal elements Metabolic savings Lighter skeleton for quicker movementsGreater ossificationWell-braced muscle attachmentsDeterminate growthEpiphysis fuses to diaphysis
30Adapted Stock, C. Rancho. La Brea: A record of Pleistocene life in California, Science Series, no. 13. Los Angeles County Museum, 1949.
34The Skull Akinetic skulls Single craniomandibular jaw joint Braincase largeSagittal and lambdoidal crest may be presentZygomatic arch usually presentSecondary palate presentTurbinal bones within nasal cavitiesForamina pass cranial nerves and vesselsThree middle ear bones transmit sound to cochleaTympanic bullaHyoid bones support tongue
35FIGURE 17A: Side view of the skull of the African wild dog (Lycaon pictus), showing the bones, foramina, and teeth
41Teeth Heterodont dentition Deciduous dentition Incisors, canines, premolars, molarsDeciduous dentitionIncisors, canines, and premolar “milk teeth” replaced by permanent dentition
42Dental formula OR (3/3, 1/1, 4/4, 2/3) × 2 = 42 Specifies number and position of teeth on one sideIncisors 3/3, Canines 1/1, Premolars 4/4, Molars 2/3OR(3/3, 1/1, 4/4, 2/3) × 2 = 42Individual teeth designated with upper case letters for upper teeth and lower case letters for lower teethP3 is upper premolar 3M2 is lower molar 2
55FIGURE 21: Molars of the Virginia opossum MasticationComplex chewing movementsInitially crush and puncture foodLater sliced by shearing surfaces of molarsFIGURE 21: Molars of the Virginia opossum(B) Adapted from Crompton, A. W., and Hiiemae, K., Discovery 5 (1969): 23.
56Carnivory vs. Herbivory CarnivoresCheek teeth become blade-like (carnassials)Adapted for slicing fleshJaw action is scissor-likeHerbivoresCheek teeth become quadrate with hypoconeJaw action is horizontal and transverse
57FIGURE 22: Comparisons of the occlusal surfaces of the right upper cheek teeth of a carnivore Adapted from Crompton, A. W., and Hiiemae, K., Discovery 5 (1969): 23.
68Tooth structure Cementum binds tooth to jaw Inner dentine Outer enamel FIGURE 23: Generalized sections of mammalian teeth, showing the internal structure
69Terminology Brachydont—short-crowned teeth Hypsodont—high-crowned teethEver-growing—grow continuouslyDiastema—space between incisors/canines and cheek teethBunodont—rounded cusps on molarsLophodont—cusps form ridgesSelenodont—cusps form crescents
70FIGURE 25: Basic cusp pattern of mammalian molars Cusp terminologyFIGURE 25: Basic cusp pattern of mammalian molarsModified from Romer, A.S. Vertebrate Paleontology. University of Chicago Press, 1966.
72FIGURE 26: Vertebrae of the gray fox Axial SkeletonRib cage and sternumVertebral columnGreater head movementDorsoventral flexion of spineFive vertebrae typesCervical, Thoracic, Lumbar, Sacral, CaudalFIGURE 26: Vertebrae of the gray fox
73Limbs and Girdles Main form of propulsion in most mammals Fore and aft movement of limbsPelvisIlium, ischium, and pubisShoulder girdleScapula and clavicle (clavicle may be reduced or absent)
74Manus and Pes Manus (hand or forefoot) Pes (foot or hindfoot) Five digits is ancestral—highly modified in several lingeagesPollex (thumb) and Hallux (big toe) have two phalanges—remaining digits have three phalanges