Comparative Vertebrate Anatomy 1/9/2019

The Vertebrate Skeleton

·         Bones account for about 14% of your weight

·         54 Bones in our hands

·         Astonishingly Strong

o   Can deal with a lot of stress

§  Ex. Femur – Bones supported an increased amount of weight

·         Human Skeleton

o   Reflects lifestyle and health (e.g Teeth)

§  Breaks, injury, etc.

§  206 Bones in a human skeleton

·         Number is not always the same, when we are young we have close to 300 at birth, due to fusion we have approximately 206 bones.

o   Osteologist

§  Study Human skeletons and bones.

o   Most bones appear to be connected except...

§  One “free floating bone” – the hyoid (under lower jaw, at root of tongue)

o   Is used in forensic Osteology, Archeology


·         Major Functions of Skeletal System:

o   1. Stability

o   2. Movement

o   3. Protection

o   4. Produce blood cells

o   5. Serves as Storage for minerals


·         Skeletal Materials

o   Cartilage

§  Chondrocytes

§  Avascular

§  70% water

§  Flexible/elastic

§  Types of Cartilage:

·         Hyaline cartilage (Joints)

·         Fibrous Cartilage (discs)

·         Elastic Cartilage (nose, ears)

·         Calcified Cartilage (Sharks)

§  Bone

·         Osteocytes

·         Vascular

·         Rigid skeletal Material

·         Types of Bone:

o   Membrane bone

o   Endochondral Bone

·         Periosteum

o   Covers our bones. Fibrous tissue that also contains blood vessels, nerves, bone-building cells, etc.

o   Skeleton Consists of:

§  Mineralized tissues

·         Bone

·         Dentin

·         Enamel

·         Cartilage

·         Ossification/Osteogenesis (i.e Bone growth) depends on 4 types of cells:

o   1. Osteoprogenitor cells:

§  Non-specialized cells in endosteum, periosteum, etc.

o   2. Osteoblasts:

§  Form bone develop from (1)).

§  Secrete calcium matrix

o   3. Osteocytes:

§  Former osteoblasts

§  Surrounded by calcium matrix

o   4. Osteoclasts:

§  Tear down old bone

§   help in remodeling

§  move calcium and phosphate around into blood.

·         Osteological terminology – Surface Features

o   Epiphysis – Ends of long bones

o   Diaphysis – Shaft

o   Condyles – Rounded projection

o   Crests – Also known as ridge

o   Head - (e.g., head of femur)

o   Process – (Well-defined projection)

o   Trochanter – Femoral Projection

o   Foramen – Passageway for nerves, blood

o   Fossa – Shallow depression

·         Types of Bones:

o   Long Bones

§  Part of the appendicular skeleton

§  Femur, humorous, radius

o   Short Bones

§  Wrist

§  Ankle

o   Flat Bones:

§  Sternum

§  Scapula

§  Shoulder blade

o   Irregular Bones:

§  Vertebrae – Have many shallow depressions

·         Types of Bone Tissue:

o   Compact Bone:

§  Dense

§  Found in long bones

§  Contains osteons/haversian systems

o   Spongy Bone:

§  Lighter

§  Made up of plate-like trabeculae lined with endosteum

·         Medullary Cavity

o   Stored Bone Marrow:

§  Red Bone marrow

·         Produces red blood cells (erythrocytes, ~3 million per second) and White blood cells (Leukocytes).

§  Yellow Marrow:

·         Mostly Fat

·         Can be turned into red marrow if required

§  Most blood cells in childhood produced in long bones (red marrow later replaced with yellow).

·         Later in pelvis, skull, vertebrae

·         The skeletal and muscular systems include the following parts: 3 divisions

o   Skull: Cranium

§  Lower Jaw

·         Humans = 1 bone (Dentary)

§  Gill arches

§  Associated Muscles

o   Axial:

§  Vertebrae (+ribs)

§  Sternum

§  Gastralia (“Belly ribs”)

§  Associated muscles

o   Appendicular

§  Limb

§  Girdle elements

§  Associated muscles.

·         Vertebrae Skeleton is very Conservative

·         Analogous (also homoplasy): Different structures, Same function

·         Homologous: Same Structure

·         Joints & Sutures

o   Suture:

§  No movement (e.g frontal suture)

§  Fontanel: Young humans have this

·         Soft Spots – bone has not calcified

o   Ex. Soft spots on baby’s head

·         Skull must be flexible during child birth

o   Joints: 3 Major Categories

§  Synarthroses: “With Joint”

·         Bone-to-bone junction by ligaments

·         Restricted movement

·         Includes sutures (e.g skulls)

§  Synchondroses: “With Cartilage”

·         Bone-cartilage sandwich

·         Restricted movement

·         Includes Symphyses

·         Intervertebral joints between centra (e.g joints between vertebrae)

§  Synovial joints: “with capsule”

·         Joint in a lubricated capsule

·         More movement (e.g shoulder, knee, wrist, joints.)

·         Sinuses

o   To humidify and warm air we breathe in

o   Sinus infection:

§  Buildup of mucus and fluid in cavities.

·         Middle ear bones:

o   Amplify sound vibrations which are then received in inner ear(cochlea)

§  Evolved from jaw bones of reptilian ancestors.

·         Teeth:

o   Materials that are like bone:

§  Dentin (softer than bone) and enamel (harder than bone)

o   Heterodont: Most animals = different types of teeth

o   Incisors: Chisel shaped cutting teeth

o   Canine Teeth: Pointed for piercing, tearing

o   Premolars: Grinding teeth with 1-2 roots

o   Molars: grinding teeth with 3 roots


Evolution of Vertebrates (I) 1/11/19


·         99.9 % of all organisms and all ecosystems are extinct.

·         Vertebrae skeleton and evolution; you must look back in time

·         Early signs of life

o   Stromatolites (3.5 Billion years old).

§   Microbial Mats formed in warm shallow seas.

o   3.5-Billion-year-old microfossils.

o   Some geological evidence for life about 3.85 billion years ago

o   C12 AND C13 Values suggest life was present (less C13 typical when biological processes occur)

o   More complex life only much later

o   Early life possibly began in conditions similar to deep sea vents.

o   3.5 Billion year old prokaryotic cell fossils from Australia

o   After another billion years…

§  Early Eukaryotes

·         A group which includes most complex life and typically requires oxygen. Appear about 2.1 billion years ago.

§  Cambrian Explosion

·         Lots of new forms

·         About 540 million years ago.

·         First explosion of life

·         Cambrian:

o   Around 521 mya animals evolve hard parts (exoskeleton), sexual reproduction.

o   Complex Systems like gills, compound eyes, advanced circulatory systems etc. appear.

o   Burgess Shale Fauna (~505 million years ago).

§  Bizarre animals, some of which may represent groups no longer around today.

·         Ordovician ~485-443 mya:

o   Awe-inspiring diversity of invertebrates in the oceans.

o   Plants colonize land long before animals do.

o   Ordovician seas

§  Primitive fish

§  1st paired appendages (fins)

§  Would have been an “alien world”

·         Silurian (~443-419 mya)

o   Forests of moss-like plants

o   Emergence of bony fish

o   Moveable jaws

o   Warm tropical seas

o   Early sharks

·         The Devonian (419-358 mya): “The age of Fishes”

o   New fish groups, including ferocious placoderms, many arthropods on land, land plants become common.

o   Recording 20:36

·         Carboniferous (358-298mya): Compressed carboniferous forests became coal.

o   Dense swampy forests.

o   Giant Inverts (e.g centipedes, cockroaches, 2.75 ft wsp dragonflies)

o   Lage amphibians

o   Africa & N.America collide:

§  Appalachians

·         Permian (~299-251 mya):

o   Synapsids, “mammal-like reptiles” appear on the scene.

§  Dimetrodon – Predatory synapsid from the Permian (Giant sale on its back)

§  Permian Ratfish Helicoprion – Coiled tooth whirl (Spiral Saw)

o   At end of Permian… Life experienced a massive extinction:

§  Massive event, Life nearly died (~95% of all species). Volcanism the most likely culprit, massive volcanic gas release, acid rain. Other hypotheses include asteroid impact.

·         Triassic (~251-199 mya):

o   First mammals and dinosaurs appear on the scene.

o   Pangaea a supercontinent with arid interior, No ice on the poles.

o   Morganucodon – member of Mammaliaforms (Mammals + their closest extinct relatives)

o   Smilosuchus – which means “chisel crocodile”

§  Because a highly successful apex predator when it evolved in the late Triassic.

o   Early Dionosaurs – Herrerasaurs

·         Jurassic (199-145 mya):

o   Dinosaurs, pterosaurs, marine reptiles dominant. Mammals live in the shadows of the dinosaurs.

o   The supercontinent Pangaea continues to break apart.

·         Cretaceous (~145 – 66 mya)

o   Dinosaurs continue to dominate

o   Giant flying reptiles push the limits of vertebrate flight

o   Atlantic Ocean Appears

o   Massive Asteroid struck the earth.

o   Volcanism was also occurring covering India

·         Paleogene (~65 – 23 mya): Mammals take over

o   Giant “Terror Birds” evolve

o   Birth of the Himalayas

o   Evolution of whales

·         Neogene (23 – 2.6 mya)

o   North and South America Merge (Great Faunal Interchange), Forests diminish, grasslands and grazers common, First Hominids appear.

·         Quaternary (~2.6 mya to present):

o   Pattern of ice ages and warmer interglacials retreating ice gives rise to Great Lakes.

o   Homo erectus appears in Africa, anatomically humans spread across the globe.

Late Ordovician, Late Devonian, Late Permian (where life nearly died), Late Triassic, Late Cretaceous (Not as severe as Permian) : These are all mass extinction events in life.


Comparative 1/14/19

·         Vertebrates Include:

o   Jawless Fish (e.g Lamprey)

o   Jawed cartilaginous fish (e.g sharks)

o   Jawed Bony fish (e.g salmon)

o   Amphibians (e.g frogs)

o   Reptiles (e.g Lizards)

o   Birds (e.g eagles)

o   Mammals (e.g elephants)

·         Conodonts

o   At one point was a Mysterious Fossils

o   Notochord, mid-caudal fin, paired sensory organs

o   Conodonts and other vertebrates independently evolved a mineralized skeleton.

·         Ostracoderms (“Shell-skinned” fish)

o   Informal term, no phylogenetic meaning.

o   Bony Jawless fish.

o   Heterostracans and cephalaspids. The former are more Basal

o   Mineralized dermal skeleton, appearance of pelvic appendages, mineralized vertebrae.

·         Anterior gill arches may have developed into simple jaws, Going from pumping water to clamping down on prey.

·         Gnathostomes (Jawed fish)

o   Gnathostomes give rise to:

§  Chondrichthyes (cartilaginous fish)

§  Osteichthyes (actinopterygians and sarcopterygians)

§  Enlarged forebrain, paired pelvic appendages

§  Two early groups:

·         Placoderms

o   Extinct with no descendants

§  Heavy bone armor, no denticles, strong axial column. No teeth. Relatively short-lived group an early “experiment”. Silurian to Devonian.

·         Acanthodians (Silurian to Permian)

o   Erectable spines supporting soft tissue

o   Share some features with both cartilaginous and bony fish

o   Highly distinct scales, can be used to date rocks

o   Paraphyletic group

§  (Paraphyletic = groups that are not closely related)

·         Chondrichthyans (Silurian to present)

o   Sharks and rays (elasmobranches) and chimaeras

o   Cartilaginous Skeleton (Secondary loss), Pelvic claspers (2 paired male reproductive organs due to paired fin (distinctive in sharks))

o   Chimeras found in relatively deep waters

o   Live Birth and Egg-laying in sharks

o   Sharks have a large oily liver to maintain buoyancy

o   Teeth not fused to jaw  

·         Ray finned fish, Actinopterygii (420 mya, Silurain to present)

o   Bony “Spines” (or rays) support fins.

§  Over 27000 species

§  Basal forms (polypterids), Several small-mid sized groups, as well as the teleosts, which account for the vast majority of species.

§  Teleosts include eels, salmon, seahorses, carps etc.

§  In early forms scales were relatively thick and a notochord with ossified support

§  In later forms ossified vertebrates

·         Lobed Finned fish, Sarcopterygia (Devonian to present)

o   Modern Forms

§  Coelacanth (Actinistia)

§  Lungfish (Dipnoi)

o   Top predators in dome Devonian and Carboniferous envts

o   Fleshy, well-developed fins that articulate directly with humorous or femur

o   Cosmoid Scales (Consisting of cosmine)

o   Lungfish have paired lungs, a largely cartilaginous skeleton, and a well-developed notochord.

§  More closely related to us than “ray finned fish”

·         Tiktaalik – An extinct sacropterygian (~375 mya)

o   Fins, gills like a fish

o   Flat head and neck like a tetrapod

o   Functional wrist

o   Ribs like in tetrapods

o   Animals like this gave rise to lands first vertebrates

o   Tiktaalik lies in the middle: is considered to be a transitional creature

·         From Fins to Limbs – Sarcopterygians

o   Paired fleshy fins

o   Living forms:

§  Latimeria (Coelacanth)

§  Neoceratodus (Lung fish)

o   Sarcopterygians give rise to Tetrapods in the Paleozoic

·         Tetrapoda

o   Limbed vertebrates with joints and digits, Secondary loss in some groups (e.g snakes)

·         Labyrinthodontia (Late Devonian – most groups extinct in Triassic)

o   Amphibians. Replaced by reptiles in the Mesozoic, but 1 group found in Cretaceous of Australia. Paraphyletic, Informal Name.

o   Small and large forms, aquatic and terrestrial forms (sometimes changes in ontogeny)

o   Early forms include:

§  Acanthostega (gin rays and a tail fin, but also digits, weight-bearing girdles)

o   More advanced forms:

§  E.g Temnospondyls resembled reptiles but is not; Large heavily built amphibian.

·         Lissamphibia

o   Includes salamanders, caecilians, frogs. Over 7000 living sp.

o   Can be traced back to Jurassic (Salamanders) and Triassic (Frogs)

o   Eggs lack shells and amniotic membranes.

o   Anura (Frogs “Without tail”) undergo impressive metamorphosis

o   Temnospondyls might be their ancestors. Pedomorphosis would explain size differences + reduced ossification in modern Sp.

§  Humans are Paedomorphic in way.

·         Amniota

o   Amniotes (Tetrapods excluding amphibians)

o   Embryo protected by special membranes, often protected by hard or leathery shell.

o   Two major Lineages:

§  Synapsids (e.g mammals)

·         *Make sketch of synapsid and Diapsid skull*

·         1 Fenestra (window) in posterior part of skull (Synapsids)

o   2 Fenestra in Diapsid skull

§  Sauropsids (e.g birds, “reptiles”)

·         Diaspids: Sauropsids


o   Lepidosauria (sister taxon to Archosauria)

§  Reptiles with overlapping scales

§  Important subgroup:

·         Squamata (Snakes, Lizards, Mosasaurs)

o   Ichthyosaurs and Plesiosaurs

§  Marine Reptiles – NOT dinosaurs

§  Ichthyosaurs:

·         Live birth and dolphin like shape

·         Tail first during birth so it doesn’t drown.

o   Turtles

§  Diapsids and Archosauropmorpha?

§  Date from Triassic

§  Shell develops form ribs

§  Papochelys, “proto-turtle” early ancestor form (“proto-turtle”)


1/16/19 Lecture 5

·         Diaspids: Sauropsids

o   Pterosaurs (Trissaic-Cretaceous)

§  Arachosaurs

§  Not Birds, or bats

§  Spectacular Flyers

§  Include the largest flying vertebrates ever to evolve

o   Dinosauria

§  Archosaurs with erect limbs

§  Include small and giant forms

§  Word is derived from the Greek words (deinos – “terrible”, or “formidable”) and (saura = “reptile”, or “lizards”)

§  Wide range of feeding strategies. (some Homodont some heterodont)

§  Herding behavior documented in some taxa

o   Feathered dinosaurs and birds

§  Birds are living dinosaurs

§  Avian(birds) brooding and integument in predatory dinosaurs

§  More bird species than mammal species (10,000 vs 5,400)!

·         Synapsids:

o   Pelycosaurs

§  Early synapsids, appear in the carboniferous

§  “Mammal-like reptiles”. In fact, they are not reptiles (mammals)

o   Therapsids (evolved from Pelycosaurs)

§  Include cynodonts, which gave rise to mammals.

§  Appear in Permian

o   Mammals (the only surviving synapsids) – selected group

§  Chriroptera (Bats – about 25% of all mammal species)

§  Cetacea (Whales and dolphin)

§  Perissodactlya (odd-toes, e.g., rhinos, horses)

§  Artiodactyla (even-toed, e.g., sheep, giraffes, deer)

§  Carniovra (e.g., wolves, seals, bears, cats, hyaenas)

§  Primates (e.g., lemurs, chimpanzees, humans, gorillas)

·         Mammals are:

o   Vertebrata i.e animals with a  backbone

o   Gnathostomata which have hinged, opposable jaws

o   Tetrapods: (they have four limbs with digits)

o   Amniota (animals with an amniotic egg membrane)

o   Synapsida (one temporal opening in the skull)

·         Artificial groupings such as “Reptiles” and “Birds” are classified as Diapsida

·         “Fish” include several groups. Not that the “fleshy-finned” Sarcoptyergia, are more closely related to terrestrial tetrapods than they are close to other “fish”.

Summary I:

·         Agnathans:

o   Vertebral Column. Earliest vertebrates include animals like Haikouichthys

·         Ostracoderms:

o   Armored fish

·         Cyclostomes:

o   Hagfish and lampreys are the only surviving agnathans

Summary II

·         Early Gnathostomes (acanthodians, placoderms): Jawed and paired fish

o   Gnathostomes give rise to Chondrichthyes (cartilaginous fish) and Osteichthyes (actinopterygians and sarcopterygians)

§  Sarcopterygians give rise to Tetrapods in the Paleozoic

·         Amniotes (tetrapods excluding ambjibians) arise from tetrapods


The Skeletal System and muscular systems include the following parts:

1.       Skull: Cranium and lower jaw, Gill arches and associated muscles

2.       Axial: Vertebrae (+ribs)


Skull Morphology:

1.       Braincase: encases the brain

2.       Foramen Magnum: opening for spinal cord

3.       Upper jaw vs lower jaw

4.       Lower jaw in mammals: only one bone (dermal dentary)

Give rise to sauropsids (reptiles and birds) and synapsids (therapsids, modern mammals.)



Lecture 6 1/23/19


·         Skull Divisions

o   Each one has a different evolutionary origin

·         Neurocranium/Chondrocranium:

o   Also known as chondrocranium. It means “Brain skull” . Encloses the brain.

o   Basal cranial structure

o   Typically an embryonic structure, later ossified

o   In some taxa (e.g. sharks, agnathans)it persists and protexts the brain

o   Forms after about 28 days in humans

·         Splanchnocranium (or visceral skeleton):

o   Associated with filter-feeding in early chordates. Often supports the gills in vertebrates. Parts of the splanchonocranium contribute to jaws and hyoids in jawed vertebrates. The word means “Gut” skull.

o   Derived from pharyngeal arches

o   In mammals, the ear ossicles (incus, malleus, stapes) are part of the splanchnocranium.

o   In reptiles the equivalent bones are part of the jaw apparatus (e.g. quadrate, articular)

·         Dermatocranium:

o   Dermal bones that contribute to the skull. The dermatocranium is derived from the bony armor of early fishes, forms part of the skull in ostracoderms. The word means “skin” skull.

o   Typically includes facial skeleton (e.g premax, maxilla, nasals), the orbital series (e.g. lacrimal, jugal), temporal series (e.g. supratermporal), vault series (e.g. frontal), palatal series (e.g. palatine), mandibular series (e.g. angular)


Axial Skeleton

·         Key Vertebral Terms

o   Neural arch

o   Neural spine

o   Centrum

o   Postzygapophysis (back)

o   Prezygapohysis (front)

Listen to Recording @: 20:00

·         Cervical Vertebrae: In humans and many other mammals cervical ribs are rare birth defects. The last mammoths may have suffered from a very high percentage of birth defects (Cervical ribs)

o   Neck Vertebrae

§  Most mammals have 7 (even giraffes)

§  Amphibians only have 1 cervical, little movement

§  Birds can have over 20 (swans), and some dinosaurs got close (19 in Mamenchisaurus)

o   Atlas

§  The “Cradle” that allows the head to rock back and forth (nodding joint)

§  It is the first Cervical (C1)

§  In amniotes (reptiles, birds and mammals) C1 and C2 are heavily modified and known as atlas and axis.

o   Axis

§  Second cervical vertebra (C2)

o   Massive-looking dinosaurs bones are often 90% air..

§  Pneumatic bones

§  Avian-style breathing + weight reduction

§  Avian-style airsacks and breathing in dinosaurs. Better than in mammals, which don’t have unidirectional airflow.

·         Dorsal Vertebrae

o   Often divided into thoracic (with ribs) and lumbar (without ribs) vertebrae.

o   In snakes both bear ribs with total vert. Number >500 in some species.

o   Ligaments from neural spines to cervicals and skull help support the massive head of this bison.

o   Ribs:

§  Articulate or fuse with vertebrae. Stability, respiration

§  In fish often two sets of ribs (ventral and dorsal)

§  In basal tetrapods two heads:

·         Tuberculum (dorsal head)

·         Capitulum (ventral head)

·         They articulate with diapophysis and parapophysis respectively.

§  Modified ribs in a cobra hood

·         Straighter than any other vertebrae


o   Sternum

§  Site of origin for chest muscles

§  Consists of varying numbers of elements in different groups

§  Absent in fishes and early tetrapods

§  In birds massive keel on sternum (the carina) anchors even stronger muscles.

o   Ribs and vertebrae fuse to form a turtle’s carapace.

o   Scapula in turtles move inside the rib cage in early development

Writing a popular article assignment:

Research a topic by reading well-researches resources (books, articles, etc.)

Model your article on a popular science format (e.g. Discover Magazine)

Write a 1.5 to 2 page article, images or graphs optional (Do not count toward total written)

Start researching your topic on January 25th (no lecture)

Submission: February 5th, no extensions! Print your article and bring it to my office (LS 305)

5 major themes: Pick one

1.       Dinosaurs and birds

2.       Aquatic Mammals (whales etc.)

3.       Venom use in vertebrates

4.       Sonar and echolocation

5.       From Fins to Limbs (fish tetrapod transition)



Sacral Vertebrae

·         Amphibians have one sacral vertebra

·         Living reptiles (e.g., crocs, lizards) and most birds have two.

·         Most mammals have 3 (e.g. cat) to 5 (human)

·         Fused sacral vertebrae in a single complex: known as sacrum

Caudal Vertebrae

·         Large number of caudals in some extinct tetrapods, as well as some extant taxa (E.g crocs, kangaroo)

·         Coccyx

o   In great Apes ( which includes humans) fused tail bones from this structure. Vestigial tail

o   In modern birds the tail is fused into the pygostyle.

o   Caudal vertebrae are simpler the more distal they are.

·         Caudal autotomy

o   In some lizards

o   To escape predators or other dangers

o   Costly for the individual, rarely used strategy. (Lizards break off their own tails to avoid predators)

·         In birds trunk vertebrae, sacral, proximal caudal vertebrae form the synsacrum

o   Provides stability in bipedal locomotion

·         Last caudals are fused to form pygostyle

Gastralia (Belly Ribs)

·         Found in crocodiles, dinosaurs, plesiosaurs etc.

·         Might be similar to the turtle plastron

·         Provide support for abdomen and associated muscles.

Next page begins Appendicular Skeleton 




·         Appendicular Skeleton

o   Pectoral girdle

o   Pelvic girdle

o   Appendages (fins/limbs)

o   Some vertebrates have no appendicular skeleton (e.g., snakes, agnathans).

o   Key Terms:

§  Pectoral Girdle (shoulder girdle)

§  Pelvic Girdle (Hip)

§  Chiridium: limb

§  Stylopodium (or propodium): Humerus/femur

§  Zeugopodium (Epipodium): radius + ulna/fibula/tibia

§  Autopodium: Manus/pes

§  Carpals, Metacarpals: wrist and finger bones of the hand (manus)

§  Tarsals, metatarsals: wrist and toe bones of the foot (pes)

§  Humerus (upper arm bone)

§  Radius and ulna (lower arm bones)

§  Femus: Thigh Bone

§  Tibia and fibula (lower leg bones)

§  Scapula (shoulder blade)

§  Ilium, pubis, ischium: Hip bones

§  Pes: Foot

§  Manus: Hand

·         Pectoral Girdle

o   Supports a pectoral fin or limb

o   Membrane (forms in skin) and replacement (forms by replacing embryonic cartilage) bones

o   Early fish:

§  Coracoid, scapula, Scapulacoracoid (replacement bones)

§  Clavicle, Cleithrum, supracelithrum, Posttemporal (memprane bones)

o   Extant bony fish: Cleithrum and supraceleithrum enlarged.

o   Posttemporal bone braces pectoral girdle against skull in fish. Lost in early tetrapods.

o   Clavicle absent in some groups (e.g. felines, cetaceans, ungulates)

·         Shoulder girdle in tetrapods not connected to skull (unlike fish)

o   This results in loss of posttemporal, supraclethrum etc.

·         Pelvic Girdle

o   Supports pelvic fin or limb

o   Llium, pubis, and ischium in tetrapods

o   Mammals: innominate bone (fusion of ilium, pubis and ischium)

o   Ovarian hormone (relaxin) expands pelvic opening for birth

o   Large, expanded ilium and ischium for bipedal walking in birds.

o   Epipubic bones in marsupials, for pouch support

o   In fish, Two simple pelvic plates (meet at pelvic symphysis)

o   Acetabulum: head/socket of the femur fits here.

·         Fins

o   Fin rays support find

o   Paired Fins:

§  Pectoral and pelvis fins (others are single)

§  Evolved for stability and maneuverability

o   Fins with symmetrical axis: archipterygial fin

o   Fins with asymmetrical axis: metapterygial fin

o   Heterocercal Fin:

o   Protocercal Fin:

o   Diphycercal Fin:

o   Homocercal Fin:



·         Fin skeleton gets progressively smaller on the tetrapod line

·         Fossils document this transition, but what about the genes involved?

·         Spanish scientists have identified candidate genes, such as 5’Hoxd

·         Genetic and developmental data shows that distal elements of fish fin correspond to tetrapod wrist bones

·         Paired fin cartilages ‘segment’ in development

·         Limb cartilages ‘segment’ in development

·         Manus – Carpals

o   Proximal (articulate with ulna and radius) and distal (articulate with metacarpals) carpals

o   Proximal carpals in basal forms known as Ulnare, radiale, intermedium and, less often cetrale 4.

o   8 carpal bones in humans

o   Dinosaurs had up to 9, modern birds retain only 4.

·         Manus – metacarpals and phalanges

o   Metacarpals, located between carpal bones and phalanges

o   Phalanges, distal-most portion of the manus skeleton. Phalanges are numbered from proximal to distal.

·         Pes

o   Proximal (articulate with tibia and fibula) and distal (articulate with metatarsals) tarsals

o   Consists of metatarsals and pedal phalanges

·         Modifications of the limb skeleton

o   Manus reduced in birds (carpometacarpus consists of 3 metacarpals and 3 carpals). Also: tarsometatarsus (metatarsals and distal tarsals)

o   Tibiotarsus in birds (fusion of proximal tarsus with tibia)

o   Tibiofibula a in frogs



Vertebrate Muscles

·         Record Breaking muscles

o   Distribution of “fast” muscle fibers in cheetah allows top speeds with “rear-wheel drive”

o   100+ ton blue whale: 40 tons of muscles.

§  Tongue weighs as much as elephant

§  (Elephant largest terrestrial vertebrae alive today)

·         From Latin musculus. Perhaps refers to mouse-like appearance of muscles moving under skin.

o   Myology: study of muscular system

o   Muscles derived from the mesoderm (embryonic germ layer)

o   Evolutionary origin of muscle cells debated.

·         Skeletal muscle (striated)

·         Smooth muscle

·         Cardiac muscle (striated)

·         Key roles of muscles:

o   Muscles produce body movements

o   Muscles generate heat (shivering, contracting)

o   Muscles move substances through the body (heart, digestive muscles)

o   Muscles enable us to stand (posture)

·         Key properties of muscle tissue:

o   Excitability (respond to stimuli)

o   Contractility (contract when stimulated)

o   Elasticity (return to original shape)

o   Extensibility (stretching)

·         Muscles account for 40% of body weight

o   At age 80, almost half of muscle mass lost

o   650 Different muscles (Homo sapiens)

o   Elephants trunk: about 40,000 muscles

o   Smallest muscles are in ear

o   Largest muscle: Gluteus Maximus

·         “Strongest” human muscle: masseter (~890N)

o   Saltwater croc bite: 16,490 N

o   Tyrannosaurus rex bite: 36,000 N

·         Skeletal Muscles

o   Voluntary muscles

o   Fibers are striped (striated)

o   Long and cylindrical

o   Attach to bones (---tendons)

·         Smooth Muscle

o   Involuntary muscles

o   Not striated

o   Found in organs, airways etc.

o   Movement of food

o   Movement of blood (vasoconstriction and vasodilation)

·         Cardiac Muscles:

o   Only found in heart

o   Striated

o   Involuntary muscle

o   Contractions pump blood through the body

o   Intercalated discs ensure synchronized contraction of cardiac tissue

·         Muscle attachement

o   Tendons (fibrous tissue) attach muscle to bone

o   Some muscle (e.g facial) attach directly to bone via aponeuroses (connective tissue)

o   Point of origin: Part of the muscle attached to stationary bone

o   Point of insertion: Part of muscle attached to moving bone



2/6/2019 (Missing previous lecture)

·         Orbicularis Oris

o   Muscle complex enclosing the mouth, inserts directly into the lips. Moves lips together, closes mouth. Main muscle used in kissing.

·         Zygomaticus

o   Facial expression muscle. Allows humans to smile. Variability in morphology causes “dimples” 

·         Levator Labii superioris

o   Elevates the upper lip

·         Tongue

o   Very important in food processing, speech.

o   Genioglossus muscles retract tongue.

o   Styloglossus muscles elevate/retract tongue

o   Palatoglossus muscles elevate posterior region of tongue.

·         In mammals (Vibrissal capsular muscles)

o   Important to move whiskers (Vibrissae)

o   Vestigial remnants still present in some humans.

·         Auricular muscles in dogs

o   In humans these are pretty much vestigial, with minimal function

o   Turning, raising of ears in many other mammals, including dogs

o   4 major groups

§  Caudal

§  Dorsal

§  Ventral

§  Rostral

·         Sternocleidomastoid

o   Rotates the head and flexes the neck. Originates from sternum and clavicle

·         Splenius Capitis

o   Moves Head (e.g. shaking head)

·         Over 40,000 muscles in the trunk (fusion of nose and upper lip) of an elephant. Eight major muscles

o   Can pick up a coin or lift a huge tree log.

o   Tip of trunk of Asian elephant has one tip to pic things up and African elephant has two.

Axial and Appendicular Muscles

·         Axial muscles in fish very important in locomotion

o   Contraction alternates from side to side when spreading through muscles à undulation

o   Lateral thrusts move fish forward

o   Some fish are actually functionally warm blooded. (Sharks generate a lot of heat via deep red muscles and are effectively “warm blooded”

·         Hypaxial Muscles

o   Innervated by the ventral ramus (branch) of the spinal nerves

o   Prominent hypaxia muscle groups in reptiles; dorsomedial muscles (beneath vertebral series), medial musculature (inside of rib cage), lateral musculature (outside of rib cage)

·         Epaxial Muscles

o   Are innervated by the dorsal Ramus

o   Three major divisions:

§  Transcersopinallis group

§  Longissimus Group

§  Lliocostalis group

·         Axial musculature remains important in locomotion in some tetrapods (e.g. salamanders, snakes)

·         In others axial musculature greatly reduced and appendicular muscles more prominent (e.g. frogs)

·         Hypaxial musculature associated with rib cage aids in breathing in reptiles.

·         In Humans: Appendicular Skeleton

o   Moves ribcage, but no role for appendicular elements

o   Major Groups

§  Muscles of the vertebral series

·         Muscles associated with the vertebral series are very complex

·         Often overlap. Covered by superficial muscles – trapezius and latissimus dorsi

·         Axial muscles are also important in respiration

·         Some muscles contract and expand volume of thoracic cavity à inhalation

·         Some muscles contract/relax and force air out/recue volume à exhalation

·         Diaphram à separates thoracic and abdominal cavities. Very important for breathing: when it contracts, volume of thorax increases à air comes in

·         True diaphragm found in mammals. Other groups have accessory muscles. Some (birds, air sac system) have more efficient breathing.

§  Oblique and rectus muscles

·         Oblique muscles can rotate vertebral series or compress underlying structures.

§  Muscles of the pelvic floor

·         Pelvic floor (also known as pelvic diaphragm) muscles support pelvic cavity structures, move waste materials through urethra and anus. Also support intestines, bladder etc.

§  (Muscles of head and neck sometimes included)

§  Appendicular Muscles:

·         These muscles insert on girdles, limbs or fins.

·         In fish appendages (fins) essentially unjointed. Axial muscles far more important for fish

·         In tetrapods appendicular muscles very complex. Creating movement across joints.

·         Tetrapod musculature of the limbs has phylogenetic contributions from other regions: axial muscles and branchiomeric muscles (derived from branchial musculature in fishes)

·         Pectoral girdle typically attached to skull in fish. Freeing of the girdle meant that axial and branchiomeric muscles had to play new roles.

§  Appendicular muscles in humans:

·         Move forelimbs and hind limbs, also control pectoral and pelvic girdles.

·         Important in posture.

·         Muscles moving the pectoral girdle originate on the axial skeleton. Insert on clavicle and scapula.

·         Movement of scapula increase the angle of movements for the forelimb. Muscles also stabilize scapula.

§  Pectoral muscles in birds. Impressive “lever and pulley system” of supracoracoideus and pectoralis

§  Frogs do not have alternating limb movements

·         Instead use saltation (jumping)- Powerful muscles are located in hind limb

·         Simultaneously activated. Pectoral girdle and forelimb then absorb shock.


·         The tensile strength of typical bone is about 150 megapascals.

·         Godzilla’ bones would have to be able to handle pressures like those found 100 kilometers below surface of our planet.

·         There is a reason why large animals look very different from small animals: An elephants proportions and Bauplan (bodyplan) are different from those we see in a mouse

·         The main reason: allometric scaling. The bones of the elephant are much larger.

o   As you increase size, volume increases much faster than surface area.

·         So mathematic tells us that an organisms’ mass would increase cubically (i.e by a power of three)

o   But by the same ratio of size increases, the width would merely increase by a power of two. (body width, bones, muscles, etc.)

o   Note that as they get bigger, animals have to dedicate an increasingly larger proportion of their body mass to  simply supporting their bulk.

·         As weight increases, limb bones must become thicker and longer to hand the weight.

·         Blood must be pumped through the body. The pressure needed to move the huge amount of blood in Godzilla’s body would burst the arteries…

·         JBS. Haldane – talked about a mouse falling and nothing happening.

·         The rules are different in water. Buoyancy helps support the weight of a giant whale, like this Bryde Whale.

Predators and Prey (I of II)

·         Predation: Interspecies population interaction

·         Predators consume Prey

·         Predators play a key role in controlling population numbers in many ecosystems.

·         Carnivore: Meat eater (e.g lion)

·         Herbivore: Plants (e.g. Elephant)

·         Omnivore: Eats items from animal + plant origin (e.g. brown bear)

·         Piscivore: Fish-eater (e.g. gharial -narrow snouted croc)

·         Insectivore: Insect eater (e.g. sloth bear; chameleon)

·         Frugivore: Fruit eater (e.g. fruit bat; toucan)

·         Avivore: Bird eater (e.g. falcon)

·         Durophage: Feeding on hard-shelled organisms (e.g. horn shark)

·         Hematophage: feeding on blood (e.g vampire bat)

·         Is herbivory also predation?

o   Herbivory Is consumption of plant material by a herbivore. This process is often not fatal and can even be advantageous for the plant or the wider floral community. Does not really fit common definitions of predation. It is still sometimes used as an example of predation.

o   Note however that herbivore-plant relationship can also evolve into fierce “arms races”. Plants have evolved thorns, spines, toxicity etc. to defend themselves from herbivores.

·         Simple model:

o   Prey population increases in size, followed by increase in predator numbers. Predation then causes prey population decline, which then affects predator numbers

o   Reality often far more complex (food webs highly complex)

·         Predator-prey relationships also affect other parts of an ecosystem.

o   Ex.

§  Herbivore eats twigs

§  More herbivores = more damage to trees.

§  More predators = fewer herbivores and less damage to trees.

·         Predators will avoid prey items that are too dangerous, too large, or too fast. Typically target young, old, or injured individuals.

·         Put simply, predators avoid prey that is energetically expensive to process or might result in injury.

·         Predator/prey relationships are often evolutionary “arms races”. Natural selection pushes predators toward greater hunting success and efficiency. Prey animals evolve traits that help them escape predation.

·         Claws

o   Claws can be used in many different ways

o   Example include:

§  To stabilize prey, inflict severe injures, to climb onto prey, or to dig prey out of the ground.

·         Teeth

o   Likewise, teeth have many different functions.

o   Chewing plant material, catching slipper prey (e.g. fish), tearing through flesh or crunching bones.

o   Teeth and jaw can be highly specialized

§  Flexible quadrate bone in python allows a lot of rotational flexibility.

o   Left and right lower jaws can move independently so the snake can “walk” its jaws along the prey when engulfing it.

·         Predator strategies:

o   Camouflage cryptic coloration/camouflage

o   Sit and wait predation (here crocodile fish) sometimes coupled with camouflage

o   Some predators inject venom.

§  Example. Horned desert viper (Cerates cerates)

o   Unusual strategies: Snapping turtle Macrochelys temminckii. Worm-like projection used to lure prey.

Missing 2/13/19, 2/8/19, 2/4/19