W11 L1 Flashcards
When did the earliest paired pectoral fins show up?
in the Late Silurian through the Early Devonian in the Ostracoderm
Which group did paired pelvic fins first arise?
placoderms
What is the advantage to paired appendages?
allows for an energy efficient way to drive through incompressible liquid in three dimensions
Fins can help to adjust what in a 3D environment?
attitude and direction
What are the symplesiomorphies of tiktaalik?
- well developed gills
- poorly ossified vertebrae
- elongated body
- fin rays
what is the synapomorphies of tiktaalik?
- no operculum
- strong overlapping ribs
- wrist bones
- rotation of pectoral fins
What is the common pattern of limbs?
- Basal stylopod
- Distal zeugopod
- Distal radials (auto pod)
Tetrapod auto pods have genetic homologies with what structures?
structures in fish fins
How did hands and feet emerge?
as a property of differential expression of hox genes
What does digit formation start with? How are digits added?
starts with the 4th digit
added towards the thumb
What type of posture did early tetrapods have?
sprawling posture
How did the movement of limbs under the body shift forces?
shifted forces to be vertical
with vertical forces, what did this lead to?
- reduction of medial elements
- increase in scapula prominence
when did posture shift?
at the end of the permian, 252 million years ago
