Post-Cranial Skeleton Axial skeleton = vertebrae, sternum, & ribs; endochondral bone. Appendicular Skeleton Pectoral skeleton supports pectoral appendages (arms); dermal and endochondral bone. Pelvic skeleton supports pelvic appendages (legs); endochondral bone.

Human Vertebra superior articular process neural arch transverse body (centrum) inferior articular process facet for head of rib tubercle of rib spinous process (neural spine)

Human Vertebrae Intervertebral discs between (annulus and nucleus) Cervical Vertebrae – 7; #1 = atlas, #2 = axis; forked neural spine on #2-#7 Thoracic Vertebrae – 12 (ribs articulate) Lumbar Vertebrae – 5 (no ribs) Sacral Vertebrae – 5; fusion begins at 16-18 and usually completed at 25 Coccygeal Vertebrae – 3-5; may become fused (= caudal vertebrae)

Human Vertebrae

Intervertebral Disc Problems

Atlas, Axis, & Other Cervical Vertebrae transverse foramen (vertebral artery)

Thoracic Vert. Articulate w/ Ribs costal cartilage

Human Ribs & Sternum Ribs – 12; on thoracic vertebrae True Ribs – 7; contact sternum directly False Ribs – 5; don’t contact sternum directly “False” / Vertebrochondral Ribs – 3; fuse to a single costal cartilage element Floating Ribs – 2; don’t contact sternum Sternum – segments fuse to form 3 bones; manubrium, body, xiphoid process (x.p. doesn’t articulate with ribs)

Human Ribs

Human Sacral/Coccygeal Vert. coccyx sacrum

Vertebral Development Sclerotome = forms vertebral elements Myotome = forms muscle Both separated into segments when the somites form. Vertical myosepta exist between segments of myotome (derived from the somite) . The myotome is also divided by a horizontal septum. Neural & hemal arches are centered on the vertical myosepta.

Vertebral Development

Vertebrate Neurula (section) somite inter- mediate meso- derm lateral plate mesoderm notochord gut

Vertebrate Embryo (section) neural crest cells dermatome sclerotome myotome splanchnic mesoderm somatic inter- mediate meso- derm gut lateral plate mesoderm

Vertebrate Embryo (section) neural crest cells dermatome sclerotome myotome splanchnic mesoderm somatic inter- mediate meso- derm gut lateral plate mesoderm

Vertebrate Embryo (section) pigment cell precursors (neural crest) ganglionic neuron dermatome sclerotome myotome dorsal & ventral mesenteries (splanchnic mesoderm) coelom gut lateral plate mesoderm

Vertebrate Embryo (section) dermatome vertebra myotome horizontal septum dorsal & ventral mesenteries (splanchnic mesoderm) coelom gut lateral plate mesoderm

Vertebrate Embryo (section) dermatome vertebra myotome horizontal septum coelom gut dorsal mesentery (splanchnic mesoderm) lateral plate mesoderm

Fish Section

Comparative Vertebra Structure Hagfishes lack vertebral structures. Neural arches dorsal to notochord surrounds dorsal nerve cord. Neural spines project above neural arch Hemal arches ventral to notochord around blood vessels in “tail” Hemal spines project below hemal arch notochord

Vertebral Centra Centrum = solid bone or cartilage vertebral “segment;” “replaces” part of notochord Intervertebral pads = separate centra; derived, in part, from the notochord Centra evolved at least three times in vertebrates (Chondrichthys, Tetrapoda, & Amia + Teleosts)

Vertebral Regionalization Non-tetrapod vertebrates Trunk (Thoracic, Abdominal) vertebrae = anterior; often bear ribs, lack hemal arches Caudal vertebrae = posterior; rarely bear ribs, have hemal arches Tetrapods Have Ant. & Post. Articulatory Processes Cervical vertebrae = neck vertebrae Thoracic vertebrae = have ribs (Lumbar vertebrae = lack ribs) Sacral vertebrae = attached to pelvic girdle

Vertebral Regionalization

Bird Vertebral Regionalization Synsacral vertebrae = vertebrae attached to pelvic girdle (homologs of sacral, lumbar, some thoracic and some caudal vertebrae)

Cervical: Atlas & Axis Atlas = first cervical vertebra in tetrapods; reduced centrum, large neural canal Axis = second cervical vertebra in amniotes (Lissamphibians have only 1 cervical vertebra, an atlas.); odontoid process (dens) for rotation of atlas, large neural canal Atlas/Occipital Condyle joint = tilting Atlas/Axis joint = rotation

Vertebral Regionalization Group Trunk Vertebrae “fish”: hagfishes, lampreys, chondrichthyans, lungfish, actinopterygiians, many trunk (number greatly variable) amphibians 1 cervical, few to many trunk, 1 sacral mammals 7 cervical, 13-27 trunk (9-20 thoracic & 4-7 lumbar), 3-5 sacral, turtles, lizards & snakes, & crocodilians 7-9 cervical, few to many trunk (especially many in snakes), 2 sacral (0 in snakes) birds 11-25 cervical, 3-10 trunk, 10-22 synsacral Caudal (“Tail”) Vertebrae vary greatly in number, even within groups.

Subphylum Vertebrata Actinopterygii Chondrichthys coelacanths amphibians hagfishes lungfishes lampreys Mammalia Reptilia R S G AT centra centra axis, >1 sacral vertebrae (Amniota) centra; atlas; sacral vertebrae; articulatory processes

Ribs Form within myosepta from cartilage. Dorsal ribs form where the myoseptum intersects the horizontal septum Ventral ribs form where the myoseptum intersects the coelom somatic mesoderm. HOMOLOGY CONTROVERSY

Vertebrate Embryo (section) dermatome vertebra myotome horizontal septum coelom gut dorsal mesentery (splanchnic mesoderm) lateral plate mesoderm

Ribs dorsal rib ventral rib

Tetrapod Ribs capitulum tuberculum dorsal rib? or ventral rib?

Sternum Sternum (midventral endochondral element) where ribs often articulate Evolved independently in most groups. Mammalian sternum composed of multiple ossified elements (stern - ebrae); manubrium = 1st; xiphisternum/xiphoid process = last

Subphylum Vertebrata Chondrichthys Actinopterygii coelacanths amphibians hagfishes lungfishes lampreys Mammalia Reptilia * ** 2 headed dorsal ribs, ventral ribs lost (Tetrapoda) Ribs (of some kind) (Gnathostomata) *segmental sternum **solid sternum

Appendicular Skeleton

Human Pectoral Skeleton

Human Pectoral Girdle Clavicle – (collar bone) large, connects acromion process of scapula and superior sternum; dermal Scapula – (shoulder blade; endochondral Acromion process – contacts clavicle Coracoid process Glenoid fossa Scapular blade Scapular spine clavicle supra- sternal notch acromion

Human Scapula acromion coracoid coracoid process process glenoid fossa scapular spine scapular blade

Human Arm Bones

Human Arm External styloid process of ulna lateral epicondyle of humerus olecranon process of ulna

Human Hand (Manus) I III II IV V pisiform

Human Hand (Manus) Bones

Human Hand External

Human Pelvic Skeleton

Human Pevic Girdle Innominate Bone – pelvis; 3 pairs bones; connects to sacral vertebrae; endochondral Ilium – fused to sacrum Ischium – posterior & inferior Pubis – anterior & inferior Obturator foramen – btw. pubis & ischium Acetabulum – femur articulates

Human Pelvic Girdle coccyx ilium sacrum pubis acetabulum obturator foramen ischium

Human Pelvis External iliac crest iliac crest (iliac spine)

Human Leg Bones

Human Leg External lateral epicondyle medial epicondyle of femur patella head of fibula tibial tuberosity tibial shaft (“shin”)

Human Pes

Human Foot (Pes) Bones

Comparative Appendicular Skeletons

--Only Gnathostomes Have-- Chondrichthyan Pectoral & Pelvic Pectoral girdle =cartilaginous scapulocoracoid Pelvic girdle = cartilaginous puboischiac bar Radials = support keratinous “fin rays” scapulocoracoid puboischiac bar radials

Osteichthyan Pectoral Girdles Scapulocoracoid (or scapula & coracoid) = endochondral; articulate(s) with radials (also endochondral) Extensive, dermal pectoral girdle Posttemporal, supracleithrum, cleithrum, clavicle, and interclavicle (median & unpaired) Fin rays = dermal bony rods (support most of fin); modified lamellar bone “scales”

Osteichthyan Pectoral Girdle Cleithrum Supracleithrum Posttemporal Clavicle Interclavicle Lepido- trichia Radials Scapulo- coracoid

Osteichthyan Pectoral Girdles Actinopterygiians - loss of ventral dermal bones (Teleosts & Amia lack clavicles & interclavicles. Gars lack interclavicles, but have clavicles.) Tetrapods - loss of dorsal dermal bones (lack posttemporal, supracleithrum, & cleithrum) Humerus = single radial articulates with “scapulocoracoid” in sarcopterygiians. (Glenoid fossa = articulation point) In Tetrapods - Humerus  Radius & Ulna  Carpals  Metacarpals  Phalanges

Tetrapod Pectoral Appendages Coracoid Scapula Clavicle Interclavicle Glenoid fossa Humerus Radius Ulna Carpals Metacarpals Phalanges

Amniote Pectoral Girdles Clavicles & interclavicle in turtle ventral shell. furcula = fused clavicles & interclavicle in birds. postcoracoid = endochondral ossification unique to mammals; fuses to scapula in therians (= coracoid process of scapula) Therian mammals lack interclavicle and coracoid.

Echidna Skeleton

Dermal Pectoral Girdle Group inter-clavicle clavicle cleithrum supra-cleithrum post- temporal reedfishes and sturgeons present gars absent teleosts & Amia lungfishes amphibians monotremes Theria turtles, birds, & lizards/snakes crocodilians

Endochondral Pectoral Girdle Group scapula coracoid postcoracoid Chondrichthys present, fused to → present, fused to ← absent reedfishes present sturgeons & paddlefish, gars, & Amia teleosts lungfishes amphibians sometimes fused to → sometimes fused to ← monotremes Theria present, fused to scapula (= coracoid process) Reptilia

Subphylum Vertebrata Actinopterygii Chondrichthys coelacanths **loss of interclavicle *loss of clavicles Actinopterygii Chondrichthys coelacanths amphibians hagfishes lungfishes lampreys Mammalia Reptilia R S G AT * ** loss of cleithrum, supracleithrum, & posttemporal (have “neck”) (Tetrapoda) dermal pec. girdle (Osteichthys) pectoral & pelvic appendages (Gnathostomata)

Subphylum Vertebrata Chondrichthys Actinopterygii coelacanths amphibians hagfishes lungfishes lampreys Mammalia Reptilia radius, ulna, metacarpals, (tibia, femur, metatarsals), phalanges (Tetrapoda) humerus, (femur) (Sarcopterygii)

Amniota lizards & snakes crocodylians montremes marsupials eutherians turtles lizards & snakes crocodylians birds posterior coracoid loss of interclavicle & anterior coracoid loss of clavicles furcula clavicles & interclavicle in ventral shell

Osteichthyan Pelvic Girdles ALL Endochondral Not in actinopts. = radials. 3 “bones” in tetrapods. Ilium = contacts sacral vert. Pubis = Anterioventral Ischium = Posterioventral Femur = single radial articulates with plvic girdle in sarcopterygiians. (Acetabulum = articulation point) turtle il is anterior pu

Tetrapod Pelvic Appendages Ilium Ischium Pubis Acetabulum Femur Fibula Tibia Tarsals Metatarsals anterior

Amniote Pelvic Girdles In Archosaurs the acetabulum is “perforated.” In birds the 3 pelvic bones fuse (innominate bone); form a synsacrum. In mammals the 3 pelvic bones often fuse (innominate bone). il pu is anterior bird

Subphylum Vertebrata Chondrichthys Actinopterygii coelacanths amphibians hagfishes lungfishes lampreys Mammalia Reptilia ilium, ischium, & pubis (Tetrapoda) pelvic girdle lost; fused basal radials pelvic girdle

Amniota Lizards & snakes crocodilians montremes marsupials eutherians turtles Lizards & snakes crocodilians birds synsacrum; tibiotarsus; tarsometatarsus perforated acetabulum (Archosauria)

Tetrapod Digit Terminology Manus = “hand” Pes = “foot” Digits numbered anterior to posterior. Ancestrally 5 digits per limb in amniotes . Pollux = “thumb;” digit I of manus Hallux = “big toe;” digit I of pes Phalangeal formula = number of phalanges in each digit starting with digit I. (e.g., 2-3-3-3-3)

Ancestral Tetrapod Manus phalanges V IV distal carpals meta- carpals ulnare radiale ulna 5 4 3 1 2 III 4 3 1 2 inter- medium radius II centrales I

Ancestral Tetrapod Pes phalanges V IV distal tarsals meta- tarsals fibulare tibiale fibula 5 4 3 1 2 III 4 3 1 2 inter- medium tibia II centrales I

Human Manus

Bird Manus & Pes Birds: much fusion of elements Only 2 free carpals Carpometacarpus = distal carpals + metacarpals of digits III & IV Tibiotarsus = tibia + proximal tarsals Tarsometatarsus = distal tarsals + metatarsals

Amniote Manus & Pes Talus = tibiale + intermedium (called Astragalus in non-mammals) Mammals - Maximum of only 1 free centrale (humans = 0 in manus, 1 in pes) Pisiform = sesamoid ossification on manus Calcaneus = fibulare with posterior process; forms heel

Genetralized Amniote Pes phalanges V IV distal tarsals meta- tarsals Calcaneus (fibulare) fibula 5 4 3 1 2 III 4 3 1 2 tibia II centrales Astragalus (tibiale + intermedium) I

Amniota lizards & snakes crocodilians monotremes marsupials eutherians turtles lizards & snakes crocodilians birds calcaneus (= “heel” on fibulare); tibia-tarsal joint (not an intratarsal joint) carpometacarpus; tibiotarsus; tarsometatarsus astragalus / talus (= tibiale + intermedium)