Skull Changes
These bones cover the gills in fish and are completely lost in tetrapods.
What is the opercular series?
In early tetrapods, paired fins transition from primarily being used for propulsion in water to fulfilling what biomechanical role on land?
What is weight bearing/support?
In the transition from water to land, expansion of elements in this girdle increased attachment sites for musculature, allowing early tetrapods to lift their head and bodies off of the substrate.
What is the pectoral girdle (shoulder girdle)?
The pelvic girdle later enlarged during the tetrapod transition to better support this movement.
What is terrestrial locomotion?
Morphologies of the vertebral column that decrease its flexibility are usually indicative of what kind of lifestyle?
What is a terrestrial lifestyle?
Fish jaw attachments, where the hyomandibula connects the jaw to the skull, eventually transition to an attachment where the jaw is attached directly to the braincase and the hyomandibula is no longer involved in jaw suspension. This attachment style is called what?
What is an autostylic jaw attachment style?
In the transition from fins to limbs, these skeletal elements eventually become the carpal and tarsal bones.
What are the radials?
The pectoral girdle eventually detached from this part of the skull in tetrapods, allowing for improved head mobility.
What is the opercular series?
The pelvis of modern tetrapods consists of these three elements.
What are the ilium, the ischium, and the pubis?
The development of these structures in early tetrapods vertebrae decreased the flexibility of their spines.
What are the zygapophyses?
Being the first part of the tetrapod body plan to evolve in the transition from fish to land vertebrates they allow for the flow of air from the nares into the oral cavity.
What are the internal nares?
The postaxial radials eventually change in size and give rise to what pieces of the tetrapod limbs?
What are the digits/phalanges?
As tetrapods strengthened their limbs and increased muscle attachment sites, this bone, present in fishes, was reduced and helped to detach the skull from the pectoral girdle.
What is the cleithrum?
The development of this symphysis, formed partly by the sacrum and ischia, helped to support tetrapod bodies in the shallows and out of the water by helping strengthen the supporting structures of the hip.
What is the pelvic symphysis?
This element in tetrapods evolved to help protect the main neural components of the organism and also to provide structural support for their bodies.
What is the vertebral column?
This joint in fishes allowed for a hinged brain case and was retained in many tetrapodomorphs, but was lost during the tetrapod transition, which contributed to the increased rigidity of early tetrapod skulls.
What is the intracranial joint?
Tiktaalik roseae was an intermediate between sarcopterygians and tetrapods. Tiktaalik retained paired fins with this dermal skeleton that is called what?
What is called lepidotrichia?
This anatomical feature evolved when dermal bones of the skull were reduced and shoulder girdle elements were expanded, which permitted the head to rotate independently of the neck.
What is the neck?
The pelvic girdle in tetrapods is fused at the midline, and is attached to the vertebral column via what structure?
What is the sacral rib?
This first cervical vertebrae arose during the shift from a skull-pectoral fish connection to an independent neck and allowed for movement of the head separate from the body.
What is the atlas?
These three bones during the tetrapod transition eventually give rise to what are the malleus, incus, and stapes in later tetrapods.
What are the hyomandibula, the quadrate, and the articular bones?
This homologous structure, found across all tetrapods, has been modified for different functions (flying, swimming, digging) in different tetrapod groups.
What is the Pentadactyl limb pattern?
The enlargement of and increased complexity of this bone improved stability in tetrapods and allowed for stronger forelimbs.
What is the scapulocoracoid bone?
This genus, characterized by its intermedial characteristics between fish and land vertebrates, is found to have a non weight-bearing pelvic girdle with its locomotion in shallow water often described as “front-wheel drive”.
What is the genus Panderichthys?
This structure is retained throughout the lifecycle of fish and is present only in embryonic development and is later replaced by the vertebral column in tetrapods.
What is the notochord?