Amphibians: phylas and Morphs

What is a temnospondyl (body system, envrionment)

• Ancient extinct order of amphibians 

• Larger than modern amphibians (think croc size) 

• Many were: Armored, retained well developed lateral line system, almost entirely restricted to aquatic environments 

• Their peak diversity was in triassic with lots of humidification, gradual acidification from jurassic to cretaceous led to downfall

What are dissorophoids ( size, what did they give rise to)

miniaturized temnospondyks with condensed and drastic metamorphosis and almost fult adult terrestrial stages 

• Gave rise to lissamphibia

Key adaptations of dissorophoids (skeletal mods, gas excahnge systems, metamorphosis)

• Skeletal modifications: structural changes to support terrestrial locomotion and feeding 

• Gas exchange system: physiological changes to support terrestrial respiration 

• Metamorphosis: developmental changes to support drastic ecological shifts across ontogeny

How did amphibians adapt to weight bearing on land? (3 ways)

Loose vertebral connections —> interlocking vertebrae

Pelvic, pectoral girdles fused to vertebral column 

Limb bones → stiff and light weight for bearing weight as opposed to dense for buoyancy regulation 

Explain lateral undulations

First quadricepts had a sprawing posture

gait was acomplished by rotation of pelvic and pectoral girdle

Trunk flexibility was inherited from swimming

What are the four adaptations in jumping

1. Reduced vertebral column: compact spine that goes rigid during jumping 

2. Tail → urostyle: tail vertebrae fused into single, rigid bone at base of spine to absorb shock during landing 

3. Elongated hindlimbs and pelvis: Femur and ilium are extra long to maximize propulsion; an extra joint in the ankle facilitates spring winding action 

4. Fused forelimbs: radius and ulna→ radioulna, shock absorber 

How is pulmonary respiration done by amphibians

• Adult amphibians have simple sac like lungs but no diaphragm 

• Modern amphibians evolved buccal pump mechanism to forcefully pump air into lungs 

What/ how is cutaneous respiration done

cutaneous respiration: respiration from skin

• Moist, permeable skin = primary respiratory organ 

• Some amphibians have secondarily lost lungs and rely on cutaneous respiitario 

what was development like in temnospondys

Larvae developed slowly and gaining of adukt features was gradual

What is development like now? when was it aquired? what did it result in a change in (feeding)

• Shift to drastic metamorphosis in dissorophoid lineage 

  • Transition to feeding on land 

• Aquatic suction → terrestrial tongue based feeding 

  • Requeire total rmodeling of the hypobranchial apparatus (HBA), jaw, and skull

• anurans have the most dramatic metamorphosis

what are three different metamorphosis modes?

Biphasic: ancestral mode characterized by aquatic eggs/larvae and terrestrial adults

Paedomorphosis: retention of larval traits

Direct development: Loss of larval stage, metamorphosis completes inside terrestiral egg and offspring hatch into mini adults