Presentation on theme: "Pectoral Girdle A pectoral girdle is a skeletal complex in the body wall immediately behind the head that articulates with the anterior fins or limbs."— Presentation transcript:
1Pectoral GirdleA pectoral girdle is a skeletal complex in the body wall immediately behind the head that articulates with the anterior fins or limbs.This is a picture of the ray-finned fish Polypterus, which exemplifies the basic pattern of all pectoral girdles.Components:Scapula & Coracoid: receives force generated by fins.Posttemporal: braces the girdle against the skull.Clavicle: braced against the opposite clavicle.Cleithrum: a major bone.
2Pectoral GirdleIn modern bony fishes the clavicle has been lost but the other bones remain.Cartilaginous fishes have only the endoskeletal components that do not ossify (shown in black) and have none of the dermal components (shown in red).
3Pectoral GirdleDermal bones predominate in the pectoral girdle of bony fishes, whereas replacement bones predominate in tetrapods.TetrapodsEarly tetrapods are only different in that they gained the interclavicle and lost the posttemporal.Tetrapods either need clavicles, coracoids or both to brace the scapula against the sternum.CoracoidDevelops from embryonic coracoid plate: anterior ossification centers give rise to procoracoids and posterior centers give rise to coracoids.ClavicleAbsent: urodeles, apodans, and most nonavian reptiles.Present in most mammals.
4Pectoral Girdle Scapula Present in all tetrapods with vestiges of anterior limbs.Contains the glenoid fossa for articulation with the humeral head.
5Pectoral Girdle Mammalian scapula Mammalian clavicle The scapular spine divides the scapula into supraspinous and infraspinous fossae, where arm muscles originate.Muscles also attach to the acromion process near the glenoid fossa.Mammalian clavicleLarge in mammals with strong forelimbs used in digging, climbing, or flying.In cats the clavicle is a vestigial splinter.No connections between scapula and the sternum.Allows cats to withstand the shock of landing upright on forelimbs.
6Test QuestionsWhat is the purpose of the posttemporal bone in the Polypterus fish?T/F Cartilaginous fish have both dermal and endoskeletal components to their pectoral girdle._________ bones predominate in the pectoral girdle of bony fishes, whereas __________ bones predominate in tetrapods.What is the purpose of the scapula in tetrapods with anterior limbs?The _________ divides the scapula into the supraspinous and infraspinous fossae.
7AnswersThe posttemporal bone braces the pectoral girdle against the skull.False, they lack dermal components.Dermal; replacementContains the glenoid fossa for articulation with the humeral head.Scapular spine
8Pelvic Girdle (Fish)Consist of cartilaginous or bony pair pelvic Plates that meet in a midventral pelvic symphysis.No dermal bones in the pelvic girdle of fishes or tetrapods.
9Pelvic Girdle (Tetrapods) Tetrapod embryos develop cartilginous pelvic plates.Each plate ossifies at two centers to form a pubis and a more posterior ischium.At the junction of the pubis, ischium, and ilium, a socket, the acetabulum, accomodates the head of the femur.
10Pelvic Girdle (Tetrapods) Reptiles:The structure of the pelvic girdles of reptiles is correlated with their diverse body structure and with their mode of locomotion.In most reptiles, the pubis is directed away from the ischium, resulting in a triradiate girdle.An epipubic and hypoischial bone frequently develops in association with the pelvic girdle of reptiles.
11Pelvic Girdle (Birds)The ilia and ischia of modern birds are enormously expanded and united with the synsacrum.There is no ischial or pubic symphysis.Absence of these provide a wide outlet for laying eggs.
12Pelvic Girdle (Mammals) Ilium, ischium, and pubis ankylose early in postnatal life to form a left and right innominate (coxal) bone.Sacroiliac jointIschiopubic symphysisSince mammalian young are delivered through the pelvic outlet, the fibrocartilage is softened by ovarian hormone relaxin, which expands the pelvic outlet for delivery.
13QuestionsThere are dermal bones in the pelvic girdle of tetrapods and fish. -T or F (False)What is the junction of the pubis, ischium, and ilium in tetrapods called? (acetabulum)In reptiles, the pubis is directed away from the ischium. What does this create? (triradiate girdle)Why do birds not have an ischial or pubic symphysis? (Wide outlet for laying eggs)What is the ovarian hormone that promotes expansion of the pelvic outlet? (relaxin)
14Girdles, Fins, Limbs & Locomotion Steering devices,brakes, and provideforward thrust(for some)Rays: located in dermis2 varieties: lepidotrichia, in bony fish, jointed bony dermal scales, aligned end to end.Ceratotrichia, in cartilaginous fish, long horny rays.
15Girdles, Fins, Limbs & Locomotion Fin rays generate from a row of cartilaginous or bony basalia and one or more rays of radialia.Striated muscle mass extends into the base of the fin and inserts onto available skeletal elements.Different taxa exhibit wide variety in morphology, making identification of ancestral fin type (archipterygium) highly unlikely.
16Girdles, Fins, Limbs & Locomotion Fishes have 1, 2, or a series of dorsal fins, and may have an anal fin. Act as keels keeping fish from rolling left to right.
17Girdles, Fins, Limbs & Locomotion Paired fins:Lobed-fleshy proximal lobe containing fin skeleton and muscles, membranous distal portion stiffened by raysFin fold- broad baseRay fins- very flexible fins, lost components of basal skeleton, some have no pelvic fins.Spiny fins- all extinct.
18Tetrapod Limbs Tetrapods typically have four limbs. Some limbs have been modified as wings or paddles while others have been lost all together.Early tetrapods had short limbs.In transition from water to land a shift from horizontal structure to vertical was seen.Later a shift from sprawling stance to upright occurred.Tetrapod limbs consist of three segments.PropdiumEpipodiumAutopodium
19Propodium and Epipodium The epipodium (forearm) is composed of the ulna and radius.The radius bears most of the weight.The ulna is longer than the radius.The ulna sometimes fuses with the radius or may be vestigial.The humerus is the single bone located in the propodium (upper arm).The humerus of all tetrapods is very similar, any variations are adaptive modifications.
20Thigh and Lower Leg Bones The thigh bone is the femur, the tibia and fibula are bones of the lower leg. There is little difference in these bones from one tetrapod to another (see picture).The patella (kneecap), which developed in birds and mammals, protects the joint from abrasive from the tendon.When the fibula unites with the tibia the tibiofibula is formed (frogs).In birds the tibia and the proximal row of tarsals fuse to form the tibiotarsus.
21Manus: The Hand Made up of wrist, palm, and digits Very similar among speciesDigits range in number; dominantis pentadactyl (five-digit) limbCarpus (wrist): Three regular rows of carpal bonesProximal row: radiale, ulnare, intermediumUlnar end in most reptiles and mammals, sesamoid bone- pisiformMiddle row: centraliaDistal row: distal carpals 1-5MetacarpalsPrimitively, as many metacarpals as digits
22Digits: Consist of phalanges Early formula for pentadactylhand:Modern mammals almostuniversallyModifications of the manusReduction in number of bonesby evolutionary loss or fusionCentralia commonly unite with proximal carpals or disappear; some reptiles and mammals have single centraleFusion of distal carpals 4 & 5 = hamate bonePhalanges or entire digits may be lost (metacarpal becomes vestigial or lost)Disproportionate lengthening or shortening (less common)
23Amphibians Nonavian reptiles and mammals Most have 5 digits on hindlimb,4 on forelimb, some have lessNumber of wrist bones issmaller in modern than inlabyrinthodontsLine of descent is conjectural,so no way to tell homologiesNonavian reptiles andmammalsGenerally pentadactyl, with five metacarpalsCrocodiles: wrist is five bonesBirds: entire manus is reducedModifications for various environments
24QUIZ What is the formula for the phalanges of most modern mammals? A) B) C) D)True or False: In birds, the proximal row of tarsals fuse to form the tibiofibulaName the three regions of tetrapod limbsChoose all the bones that are part of the manus:Radius, phalanges, radiale, ulna, metacarpals, intermedium, ulnareThe epipodium is composed of which two bones?:A) Radius, humerusB) Tibia, fibulaC) Ulna, radiusD) Ulna, femur
26Flight Carpometacarpus- fusion of 3 metacarpals and 3 distal carpals 3 fingers present…1st finger called alula (elongated, prominent, independent)Songbirds – broad short wingsCarnivorous – long, broad wingsHummingbird – hand is longer than its armHands exert a strong breaking force for landing
27Flight Unlike birds, the hand is the main part of the wings in bats Normal thumb w/ claw, but elongated fingers- both metacarpals and phalangesMovement of the hand responsible for takeoff and true flight
28Girdles, Fins, Limbs & Locomotion Adaptations for Life in the WaterThe “hands” have becomePaddlelike Flippers in well adapted marine amniotesFlippers are generallyflattened and stoutIn several taxa,the number of phalangeshas greatly increasedIn some Ichthyosaursthere were as many as 26 phalangesper digit and more than 100 in a single hand!
29Girdles, Fins, Limbs & Locomotion Most other swimmers have skeletons that conform closely to the tetrapod patternSome aquatic animals have lost their hind limbs…Use flipperlike “wings” for thrust, webbed feet for rudders (ie. Penguins)Others don’t use foreflippers for swimming….hind limbs
30Questions:1. Carpometacarpus is the fusion of ____ metacarpals and ____ carpalsA) 2, B) 3, 3C) 4, D) 2, 42. The first digit in birds that is elongated, prominent, and independently movable…A) ulnare B) radialeC) alula D) manus
31Questions continued3. True or False: In the fingers of a bat, both the metacarpals and phalanges are elongated.TrueWhat adaptation has been vital for aquatic marine amniotes, and what do they look like (shape)?Paddlelike flippers; flattened and stoutTrue or False: Penguins obtain thrust for swimming solely from their foreflippers?true
32Running and GraspingPlantigrade- Digits, wrist, and ankle rest on ground. ie. Monotremes, marsupials, primatesDigitigrade- Weight borne on digital arches with wrist and ankle elevated. ie. Rabbits, rodents and carnivoresUnguligrade- Walk on four, three, two or one digit with wrist and ankle elevated on elongated metatarsals ie. Ungulates
33Running and GraspingArtiodactyles are paraxonic meaning their bodyweight is borne evenly on two parallel axes.Perissodactyles are mesaxonic meaning weight tends to be distributed to the middle digit
34Running and GraspingTibiotarsus- Found in birds; fused proximal tarsals and tibia.Tarsometatarsus- fused distal tarsals along with three fused metatarsals.Joint between tarsometatarsus and toes allows the bird to be poised for flight.
35Running and GraspingIn homonoids the metatarsal arch allows distribution of weight over four solid bases; the heel and the ball of each foot.Hallux- the great toe; opposable in most primates but not humans, aids in grasping.
36Running and Grasping 1 - Perissodactyl 2 – Canine foot structure 3 – Opposable in primates4 - Artiodactyl5 – Human foot structureA plantigradeB digitigradeC paraxonicD mesaxonicE hallux
37Hind Feet (Amphibians and Reptiles) Comparable with manus except for pisiformBasal amphibians display a prehalluxReptiles have fused tarsal bones known as the astragalocalcaneusLabyrinthodonts and anurans have a prehallux, which may be a vestige of a tarsal or metatarsal that has been lost.Anurans have less ankle bones than urodeles. Long webbed metatarsals adapted for pushing off when leaping and swimming.Most reptiles have 5 toes, and intratarsal joint helps the Jesus lizards run rapidly.
38Hind Feet (Birds and Mammals) Bird feet are highly modified, with a tibiotarsus and fusion of the distal tarsals with the metatarsalsMammals have no intratarsal joint, but a hinge joint at the ankle.Birds also have an intratarsal joint, which helps them be ready for takeoffMost have 4 toes, ostriches have 2.3 forward radially, one posteriorly (same as tuatara’s first four toes)Some have 2 in the back (woodpeckers)In mammals, the tibia or tibiale is the principal weight bearing boneIn hominoids, a metatarsal arch distributes weight over 4 solid bases, the heel and ball of each foot (absorb shock)Opposable hallux in many primates, but not humans
39Marine Movement Sculling Anterior flippers only for maneuveringLateral undulations of posterior trunk and flippers keyNeck elongatedCetaceans thrust forward by dorsal and ventral undulations with stiff tail“Legless gallop”Sculling and galloping have been shown to be very kinematically efficientSirenians (dorsoventral undulation) but they are poor swimmers
40Terrestrial TrekkingHind flippers switch from swimming position into a tetrapod stanceFlexible wrist joint further helps locomotion on landWriggling seals’ hind limbs are permanently bound to the tailFlippers rotate beneath the body for swimming position (fur seals, sea lions, walruses)Young fur seals have disproportionately large flippers which help them run faster when they are young (fleeing predators)
41Questions Name one similarity between reptile hind feet and bird feet Name one difference between amphibian feet and reptile feetWhich group of animals lacks an intratarsal joint?What pedal feature is exclusively a hominoid characteristic?Name the primary difference in locomotion between wriggling and fur seals
42Answers Intratarsal joint Fusion of the tarsal bones Mammals Metatarsal archWriggling seals have a hind limb permanently bound to the tail, while fur seals can switch their hind flippers into a tetrapod stance.
43Origin of Tetrapod Limbs Two hypotheses:Modification of pre-existing structures orFormation of new featuresCommon to both hypotheses are the origin of proximal elements of the limbSome necessary modifications for limb development are:Elongation of the two bones of the epodium (limb bones immediately above the hand or foot.).Rotation of long axes of humerus and femur to parallel the vertebral column.Formation of hinge jointsEmergence of definitive manus (hand) and pes (foot).Fig comparison of Devonian rhipidistian fish’s pectoral fin and early tetrapod’s forelimb.Tetrapod forelimbRhipidistian pectoral fin
44Origin of Tetrapod Limbs It is possible that early Rhipidistian fins were used for resting on the water bottom. Minor modifications could have led to “walking” on the muddy floor; and later venturing onto land.Some type of pressure(s) drove craniates onto land – so it was inevitable that a more suitable limb would evolve.(Some fish today use pectoral fins to move on land, example: the Australian lungfish)
45Locomotion with no Limbs Snakes often combine several methods of locomotionLimbless amphibians on land use lateral undulation of the body and tail (like a fish) to move.Marine sea snakes have a flattened tail that they use like an oar to propel them through the water.All movements are made possible by modifications in:- the skin- body wall musculature- ribs- the vertebral column
46Locomotion with no Limbs The different types of locomotion used by snakes and other limbless tetrapods are:Serpentine – uses irregular loops propped against any stationary object that allow snake to push off from. Uses waves of muscle contraction from head to tail.Also referred to as lateral undulation, but there are slight differencesRectilinear locomotion – the snake moves in a straight line. It relies on friction between the ventral skin and substrate. The ventral skin acts like a conveyor belt. Belly scutes alternate pressing and sliding forward on the substrate to create movement.Sidewinding – Enables snakes (like rattlesnakes) to inhabit sandy deserts. Useful when the other methods would be clumsy or ineffective. Snakes propel themselves with modified serpentine movements while thrusting their anterior portion forward.Concertina – Similar to sidewinding. Movement similar to an accordian.Serpentine is the most common method of locomotion used by snakes and lizards.
47Review QuestionsMatch the following types of limbless locomotion to the diagram.SerpentineRectilinear LocomotionSidewindingConcertinaWhat is the most common method of locomotion used by limbless creatures?True or False. It is believed that tetrapod limbs evolved from fins.Limbless locomotion is made possible by modifications in:22.214.171.124.the skinbody wall musculatureRibsd. the vertebral columne. all of the above
48Which of the following is not necessary for limb development Elongation of the two bones of the epodium (limb bones immediately above the hand or foot.).Rotation of long axes of humerus and femur to parallel the vertebral column.Formation of hinge jointsEmergence of definitive manus (hand) and pes (foot).All are necessary