The body surface of Scoliodon is very rough, the surface is like sandpaper, on their skin the exoskeletal structure give the roughness, on their skin placoid scales in Scoliodon are arranged in obliquely row and point backwards directions, the placoid scales are dermal denticles, also known as odontoid, these scales are hard and minute tooth … Read more
The skin of Scoliodon: The leathery skin or integument of Scoliodon have both dermis and epidermis layers, the outer layer of integument in Scoliodon is the epidermis and the skin layer below the epidermis is known as dermis or corium layer. The tissues of the epidermis are ectodermal in origin while the tissues in the … Read more
Scoliodon is a marine cartilaginous fish, Scoliodon also known as Dogfish, they are an active predator, we will discuss the aperture or pores present on their body. Scoliodon have a streamlined body shape, they have a blackish appearance on the dorsal side and white coloration on the ventral side, the body surface is rough due … Read more
Body Shape of Scoliodon: The body shape of Scoliodon is spindle-shaped, the body is much elongated and fusiform, the body laterally compressed. Dogfish or Scoliodon can swim at a very fast speed due to their streamlined body shape, the body shape gives them swiftness which helps them to chase and catch the prey. Size of … Read more
Scoliodon: A Cartilaginous Fish: Scoliodon is a cartilaginous fish, they are aquatic, the body is streamlined, the body is covered by scales(dermal denticles), they are all marine. Scoliodon is a true fish, all the fishes can be classified into two categories based on their endoskeleton, cartilaginous fish and bony fish. All the cartilaginous fish are … Read more
Who are Placodermi: Placodermi is the first jawed Vertebrate in the history of evolution before all the primitive Vertebrates were jawless. Before Placodermi all the primitive Vertebrate paired appendages was absent but the paired appendages and strong jaw make them powerful predator. Ostracoderms become extinct approximately 450 million years ago when the first time Placodermi … Read more
Placodermi is a very important group of animals for study in the field of evolution of Gnathostomata. The study on the evolution of Placodermi gives us an idea about the evolutionary history of primitive Vertebrates. Placodermi is intermediate between the primitive extinct Ostracoderms and the modern fish, the fossil evidence of Placodermi gives us knowledge … Read more
In class Placodermi, we have placed all the primitive extinct jawed fish and they are divided into different subclass based on the similarities and dissimilarity among them. Different workers tried to classify class Placodermi in different ways but only a few of them get accepted among the science community and we will discuss the most … Read more
Most of the workers believe that Placodermi evolved from the Ostracoderm because Placodermi shows very much similarity with Ostracoderms in various aspects. We can consider Placodermi as an updated version of Ostracodermi with some new advanced features which they gain during the course of evolution. In Ostracoderms, we can see the bony external heavy armour … Read more
Who Are Actually Placodermi: If we talk about the fossil evidence for the primitive Vertebrate we do not have sufficient evidence yet which can give us an exact timeframe when actually Vertebrate arrived on our earth. Now what is the reason behind the missing fossil evidence for the primitive Vertebrate, there are different types of … Read more