Presentation 9: Appendicular Skeleton Flashcards
Appendicular Skeleton Components + Function
Pelvic Girdle (i.e. the hips)
Pectoral Girdle (i.e. the shoulders/collar bone)
Anterior/posterior limbs
Gives support to anterior limbs (connected to axial skeleton by muscular attatchment
Scapulocoracoid bar
In sharks pectoral components fuse to form scapulocoracoid bar
(ancestral condition = cartilaginous bar)
Osteichtyes Pectoral Girdle
Ancestral condition = 2 endochondral bones
1. Scapula
2. Coracoid
Other bony elements:
1. variable dermal bones (ex. clavicle, cleitrum, supracleitrum, etc.)
2. Opercular bones (located behind skull) where skull connects to pectoral girdle
Tetrapod Pectoral Girdle (Monotrema, Therian, Amphibians, Gymnophiona/Snakes, Crocodylia, Birds, Carnivores, and Cursorial mammals and Ungulates)
Ancestral condition:
- coracoid and scapula fuse into single element and loss of posttemporal bone
- Monotrema aka egg-laying mammals-> 2 coracoids and retain interclavical (anterior and posterior)
- Therian mammals lose anterior coracoid bone
- Interclavical is independently lost in amphibians and most mammals
- Pectoral girdle completely lost in gymnophiona, snakes, and legless lizards
- Crocodylia lost clavicle
- Birds: clavicles fuse to form single bone = furcula
- Carnivores: clavicles reduced
- Cursorial mammals and ungulates: clavicles lost (may allow for faster movement)
Sacroilial join
Where the pelvic girdle connects to the vertebral column in tetrapods
Sacrum
Triangular bone made up of 5 fused vertebrae which form the posterior section of the pelvis in tetrapods
Pelvic Girdle Ossification (3 major)
Ischium (ventral to the ilium and posterior to pubis
Ilium (located dorsal to Ischium and pubis and articulates w/ sacral vertebrae)
Pubis (Ventral to the ilium and anterior to the ischium)
Ischium
Ventral to ilium and posterior to pubis
Illium
Articulates w/ sacral vertebrae and located dorsal to Ischium and pubis
Pubis
Ventral to ilium and anterior to ischium
Acetabulum
rounded section of the pelvic girdle (between Ischium and Ilium) that allows for articulation of the femur
Amphibian Pelvic Girdle
Pubis remains cartilaginous (calcified) and Ilium elongated
Urostyle = fusion of Caudal vetebrae
Bird Pelvic Girdle
fusion of pelvic girdle into the synasacrum
Mammal Pelvic Girdle
Ilium, Iscium, and Pubis normally fused
Marsupials have epipubic bones called marsupium (which provide support during offspring care
Types of Fins (5)
- Dorsal
- Tail
- Anal
- Pelvic
- Pectoral
Fin Rays
Supported by pterygiophores
1. condrocythyes aka cartilaginous fish have ceratotrichia (keratin fin rays)
2. Osteicthyes (bony fish) have segmented bone including the lepidotrichia
Pterygiophores (3)
Support medial fins on dorsal side by anchoring the fin to the body via the distal, middle, and proximal bones
Type of Caudal Fin (4)
- Homocercal (vertebral column doesn’t enter the fin, present in majority of bony fishes)
- Diphycercal (vertebral column enters tail and divides it into 2 equal parts, present in lungfish)
- Heterocercal (vertebral column invades tail at slightly dorsal angle which gives a more developed upper half, sharks)
- Hypocercal (vertebral column invades tail at slightly ventral angle which gives a more developed lower half)
Homocercal
(vertebral column doesn’t enter the fin, present in majority of bony fishes)
Diphycercal
(vertebral column enters tail and divides it into 2 equal parts, present in lungfish)
Heterocercal
(vertebral column invades tail at slightly dorsal angle which gives a more developed upper half, sharks)
Hypocercal
(vertebral column invades tail at slightly ventral angle which gives a more developed lower half)
Caudal Fin Support
Epurals (modified neural arches and spines)
Hypurals (modified hemal arches and spines)
Epurals
Type of Caudal Fin Support
modified neural arches and spines
Hypurals
Type of Caudal Fin Support
modified hemal arches and spines
Paired fins
pectoral and pelvic fins (homologous to limbs of tetrapods)
Sarcoptyerygia vs crossopterygium
Sarcoptyerygia lobed fins
- present in lungfishes
- Axial elements running straight down with post axial (towards head) and pre-axial (away from head) radiating outwards
- biserial fin
Crossopterygium lobed fins
evolved independantly from sarcoptyerygia fins but contain the same lobed muscle articulation (only differences are the enlarged lobe and a lack of a post-axial element)`
Coelacanth
fins are homologous to tetrapod limbs b/c they contain the same bones (i.e. radius, ulna, and humerus) likely the source of these bones
Limbs Primitive -> Modern
Ancestral -> forelimb(s) and hindlimb(s)
Propodium -> Humerus and Femur
Epipodium -> Radius/Ulna and Tibia/Fibula
Mesopodium -> Carpals (4/5) and Tarsals (4/5)
Metapodium -> Metacarpals (5) and Metatarsals (5)
Phalanges -> Phalanges (5) and Phalanges (5)
Amphibian vs Amniota Digits
Amphibians have 4 while Amniota have 5 digits:
Odd numbers better because you have a central point to balance around. Fewer digits = better because easier to run
Amphibians have 4 in front and 5 in back to aid in jumping
Pteradactyl Evolution of Flight
- Large membranes attatched to side of body
- Membranes supported by arm and enlarged 4th digit
Chiroptera (Bats) Evolution of Flight
- Membrane supported by last 4 elongated fingers
- 1st digit is free from wing and modified to form a hook
Aves (Birds) Evolution of Flight
- Wing surface formed by feathers
- 3 digits present in anterior limbs
- only 2 carpals present (radial and ulnar)
- other carpals fused to metacarpals into a carpometacarpus
Types of Walking
- Plantigrade (soles of feet)
- Digitigrade (ankle + heel off ground i.e. w/ digits)
- Unguligrade (on end of digits)
Plantigrade
(soles of feet) i.e. primates and rodents
Digitigrade
(ankle + heel off ground i.e. w/ digits) i.e. cat and dog
Unguligrade
(on end of digits) i.e. horse and deer
Hyperphalangy
Digits increased in size (i.e. whale fin)
Hyperdactyly
Digits increased in number (i.e. extra fingers or toes)
