Cladogram breakdown:
Chondrichthyes which are cartilaginous fish have been traced back to a very long time in history as well as their fossils. These cartilaginous fish have been through evolution and became to what today we know as sharks, rays and other modern species. All these species fall under the Chondricthyans. Chondrichthyes has two major groups called the Euchondrocephali and the Elasmobranchii. The Euchondrochephalian name came from the greek which means, true cartilaginous head and an example is the Chimera. some attributes that differnciate this group are that they don't have placoid scales, no spiracle, no stomach, no ribs, and no cloaca. They do have teeth that can be used for crushing and gill slits covered by operculum. The species in this group also have the jaws connected to the chondrocranium. The other group under the Chindrichthyans is called the Elasmobranchii and under this goup fall the sharks, rays and flattened skates. Some characteristics that differentiate these species are that they have tooth like placoid scales, their teeth are easily replaced constantly and they have a cloaca.
Chondrichthyes which are cartilaginous fish have been traced back to a very long time in history as well as their fossils. These cartilaginous fish have been through evolution and became to what today we know as sharks, rays and other modern species. All these species fall under the Chondricthyans. Chondrichthyes has two major groups called the Euchondrocephali and the Elasmobranchii. The Euchondrochephalian name came from the greek which means, true cartilaginous head and an example is the Chimera. some attributes that differnciate this group are that they don't have placoid scales, no spiracle, no stomach, no ribs, and no cloaca. They do have teeth that can be used for crushing and gill slits covered by operculum. The species in this group also have the jaws connected to the chondrocranium. The other group under the Chindrichthyans is called the Elasmobranchii and under this goup fall the sharks, rays and flattened skates. Some characteristics that differentiate these species are that they have tooth like placoid scales, their teeth are easily replaced constantly and they have a cloaca.
Evolutionary History:
Cartilaginous fish go all they way back to devonian times and what we know as Chondrichthyans such as modern day sharks, skates and rays can be traced to the Triassic era. This group of species traced all the way back to the Triassic era are older version of the chondrichthyes. They are called Neoselachians, which might have evolved from the Ctenacanthida. The similarites between the Chondrichthyes and the Neoselachians that make them unique from the other groups are that they had a lighter and more flexible skeleton and vertebrae. They also share some properties of the jaw. Skates and rays are believed to trace all the way back to the Jurassic era and are characterized for their expanded pectoral fins that make them into a flat round form. Skates, rays and sharks are believed to have derrived such a long time ago from the Neosalachians and are still surving fine. This can show have they might have adapted while the time has been passing by and aquired adaptions to fit their changing environments over long periods of time.
Cartilaginous fish go all they way back to devonian times and what we know as Chondrichthyans such as modern day sharks, skates and rays can be traced to the Triassic era. This group of species traced all the way back to the Triassic era are older version of the chondrichthyes. They are called Neoselachians, which might have evolved from the Ctenacanthida. The similarites between the Chondrichthyes and the Neoselachians that make them unique from the other groups are that they had a lighter and more flexible skeleton and vertebrae. They also share some properties of the jaw. Skates and rays are believed to trace all the way back to the Jurassic era and are characterized for their expanded pectoral fins that make them into a flat round form. Skates, rays and sharks are believed to have derrived such a long time ago from the Neosalachians and are still surving fine. This can show have they might have adapted while the time has been passing by and aquired adaptions to fit their changing environments over long periods of time.