Some lobefin fish {fresh-water lobefin fish} {fresh-water lobe-finned fish} had adults that lived in fresh water and on land.
fresh water
Because fresh water has no salt, they had to maintain hydrogen and salt ion balance in blood and tissues and had to control water drinking. Seawater ion balance is similar to that in cells. To live in fresh water, organisms need to pump out cell water to maintain salt and protein concentrations and to prevent bursting.
hind limb
Rear lobefins became specialized for pushing. Later, they became legs.
teeth
Teeth were for grasping but not cutting or grinding. Teeth grew, fell out, and grew back, repeating as animals grew.
hearing
Eardrum amplified sound for better hearing.
lung
They breathed using lungs. They had no gill bones and began gill loss. Later, gills closed.
evolution
Land vertebrates evolved from lobe-finned bony fish.
lobe-finned fish and tetrapods {sarcopterygian}.
Lobe-finned fish one meter long developed into four-legged fish {tetrapod}| (Tetrapoda) in shallow, plant-filled, fresh or brackish water, in tropics and subtropics. Perhaps, front limbs helped lift head above water to get more oxygen.
fins
Pectoral and pelvic fins gained feet and toes. Tetrapods have no tail fins.
bone
Vertebrae became interlocking. Neck became flexible after losing bones that joined head and shoulders. Snout became longer and head flatter. Gill and neck bones {opercular bone, tetrapod} disappeared. Longer ribs appeared. Pelvis became larger.
evolution
Most early lobefin fish were not tetrapod ancestors: Kenichthys [-400000000], Osteolepidids [-394000000], Eusthenopteron [-388000000], Panderichthys [-385000000], Elpistostege [-384000000], and Livoniana [-384000000]. Most early tetrapods are extinct and were not living-tetrapod ancestors: Elginerpeton [-378000000], Ventastega [-370000000], Acanthostega [-368000000], Ichthyostega [-366000000], and Tulerpeton [-364000000].
Sarcopterygians {lung fish} {lungfish} can have one or two lungs, live in freshwater, and have lobefins.
4-Zoology-Kinds-Fish-Teleost-Lobe-Finned
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Date Modified: 2022.0225