Question

20. How are rayfinned fishes different from fleshy finned fishes? What were distal phalanges probably first used for?

Answer 1

Ray finned fish :-

The ray-finned fish have fin rays, with fins supported by bony spines known as rays. The ray-finned fish are the dominant class of vertebrates, with nearly 99% of fish falling into this category. They live in all aquatic environments, from freshwater and marine environments from the deep sea to the highest mountain streams.

Ray-finned fishes are so called because they possess lepidotrichia or "fin rays", their fins being webs of skin supported by bony or horny spines ("rays"), as opposed to the fleshy, lobed fins that characterize the class Sarcopterygii. These actinopterygian fin rays attach directly to the proximal or basal skeletal elements, the radials, which represent the link or connection between these fins and the internal skeleton.

Fleshy finned fish :-

The lobe-finned fish are characterized by fleshy lobed fins, as opposed to the bony fins of the ray-finned fish. There are two types of living lobe-finned fish: the coelacanths and the lungfish. The pectoral and pelvic fins have joints resembling those of tetrapod (four-limbed land vertebrates) limbs. These fins evolved into legs of amphibians, the first tetrapod land vertebrates. They also possess two dorsal fins with separate bases, as opposed to the single dorsal fin of ray-finned fish. All lobe-finned fishes possess teeth covered with true enamel. The lungfish also possess both gills and lungs, solidifying this class as the ancestors of amphibians.

They are bony fish with fleshy-, lobed-paired fins, which are joined to the body by a single bone . These fins evolved into legs of the first tetrapod land vertebrates, amphibians. The braincase of sarcoptergygians primitively has a hinge line, but this is lost in tetrapods and lungfish. Many early sarcopts have a symmetrical tail.

What were distal phalanges probably first used for :-

The distal phalanges are one of three types of finger bones. The human hand and wrist are comprised of three different bone groups. The carpals are the base of the hand and wrist, and consist of eight small bones with differing names. Above them, the metacarpals form the base of the fingers, while the phalanges are the fingers themselves. The phalanges are comprised of the proximal, middle, and distal groups. The proximal bones are located just below the knuckle, while the middle bones are located above the knuckle. The distal phalanges are the fingertips. This is why the term terminal phalanges may be interchangeable with distal phalanges. These bones are unlike their counterparts in the finger. Their main purpose involves supporting the sensitive flesh of the fingertip, where a high number of nerve endings are situated. These nerve endings translate sensory feelings of touch into nerve impulses that are transmitted back to the brain. These bones also feature apical tufts, which are flat expansions of bone. The tufts support the fingernails on the dorsal side of the fingers, and the fleshy pad of skin on the palmar side of the fingers.