Ch.8 Flashcards
Sarcopterygii
(sarko = flesh pteron = wing)
Or lobe fined
Sarcopterygian characters
Scales and joint
• Cosmine
• Composed of dentine and enamel
• Complex pore-canal system
• Intracranial joint
• Anterior and posterior regions of the skull can move independently
Sarcopterygian characters
Fins
• Monobasic paired fins (pectoral and pelvic)
• Single skeletal element contacts limb girdle
• Muscles around fin base and within fin
Reduced fins have some muscle
Extant sarcopterygians
Actinistia
• Coelacanth characters
• Unique electroreceptive organ
• Anal fin and second dorsal fin muscularized
• Inhabit deep ocean
Extant sarcopterygians
Dipnoi
• Sister group to tetrapods
• Three living genera, all on Gondwanan continents
• Australia, Africa, South America
Dipnoi characters
Lung and heart
(di = two, pneu = lung/breath)
• Circulatory and respiratory systems share similarities with tetrapods
• Lungs with chambers for gas exchange (not super efficient tho)
• Heart has divided atrium (left and right. Deoxygenated and oxygenated blood still mixed together tho) but this is showing signs of becoming more complex
Australian lungfish
• Paired pectoral and pelvic fins have muscular bases and radial elements (may have rays)
• Gas exchange in both gills and single lung (diff in tetrapods)
Fun fact
• Largest known animal genome. Most of the genome does not code for anything
Most distantly related to others that live
African lungfish
• Narrow, reduced pectoral and pelvic fins
• Fins contain few skeletal elements (muscle reduced)
• Gas exchange in both gills and paired lungs
• Strong swimmers (axial locomotion)
• Capable of surviving droughts (seasonal ones)
- excavation —> bury self in mud and secrete mucus to retain moisture. Mud bubble.
South American lungfish
• Narrow, reduced pectoral and pelvic fins
• Fins contain few skeletal elements
• Gas exchange in both gills and paired lungs
• Males guard nests of eggs and young
• Along with African lungfish, the teeth are self-sharpening plates (don’t have continual growth of teeth)
Sister group to African lungfish
Key Concepts
• Sarcopterygii includes both fishes and tetrapods
• Sarcopterygian fishes have cosmine, an intracranial joint, and monobasic fins
• Coelacanths, once thought to be extinct, live in deep oceans and have muscular anal and second dorsal fins
• Dipnoi is the sister group to tetrapods; live in freshwater habitats and often have reduced lateral fins
Tetrapodomorpha
Tetrapodomorpha united by
1. Reduction of cosmine
2. Presence of choana (skull region)
• direct Opening (in bone and soft tissue) between nostril and oral cavity
3. One-bone -> 2-bone limb pattern ( ore organized bone structure)
Tetrapodomorph vs. tetrapod morphologies
Tetrapodomorph fish
• Conical head with eyes on sides (3D water enviro, more hydrodynamic)
• Dorsal fin(s) and large caudal fin
• Fins with rays
• more ancestral
• pectoral girdle attached to cranial skeleton and opercular region and pectoral region have direct connection
• pelvic girdle not connected to spinal column
• have no necks
Tetrapod
• Flat head with eyes on top (depressed head, more beneficial in swallow water)
• No dorsal fins, reduces caudal fin
• Limbs with digits
• pectoral girdle not attached to cranial skeleton
—> allows for evo of neck
• pelvic girdle attached to vertebral column by a sacral vertebra
• have necks
Tiktaalik roseae
Transition between fishopod and tetrapod
Mosaic evolution—> diff parts of body evolved at diff times and or rates
Anterior part seems to evolve more rapidly
Probably couldn’t walk on land well or support body weight
Tetrapod morphologies
Neck
Robust overlapping ribs
Strong zygapophyses
Strong sacral connection
Distinct thoratic and lumber vertebra in trunk
Tetrapod characters
Head mobile
• due to Loss of connection to pectoral girdle
• Connects to spine via occipital condyles (ancestral is to have 2)
Pentadactyl limb
• Limb with five digits (ancestral condition)
• 1 bone -> 2 bones configuration (holds up until get to wrists/hands)
• Great variation now
Tetrapod vertebrae characteristics
Regionalization
• Form changes along the length of the spinal column
Centrum
• Main body of vertebra
• Composed of two parts in early tetrapods (round bulky apart, provides support)
Neural arch
• Protects spinal cord
• Neural spine(expansions of neural arch) – projects dorsally (increase surface area for things to attach to)
Zygapophyses
• Anterior and posterior pairs
• Support preceding vertebra
Tetrapod limb characters
• 1 bone -> 2 bones
(Not expected to know this, just used for discussion)
• Humerus/femur
• to Radius, ulna / tibia, fibula
• to Carpals/tarsals
• These contribute to Mobile joints (support bones)
• Attachments sites for muscles (control movement)
• Digits (for support —> expanding surface area at end of limbs)
Body support and stabilization
• Zygapophyses
• Enlarged ribs
• Expanded limb girdles (bone more weight)
• Specializations in epaxial and hypaxial musculature
Tetrapod ecology: trackways
Point is animals walking around before we find animals like tetrapods
Semi-aquatic to completely aquatic
Most likely tetrapod limbs not evolved for on land but for high currents of water —> providing support against currents
Tetrapod ecology
• Why invade land?
• Less competition for food
• Protect eggs or juveniles
• Bask in sun
• Necessary due to changeable environment?
• Extreme tides
• Long dry seasons
• could have happened many times (radiation)
• sea levels could have dropped
Key Conepts tetrapods
• Tetrapods originated in freshwater to estuarine systems in an area that now spans eastern North America to northern Europe
• Tiktaalik roseae shows a combination of primitive and derived traits
• Tetrapods are characterized by the presence of a neck, jointed limbs, and pentadactyl hands/feet
• Skeletal adaptations including zygapophyses, enlarged limb girdles, and large ribs helped early tetrapods support themselves on land
• Various environmental considerations may have led tetrapods to invade land from rivers, lakes and deltas
