What are examples of Cephalaspidomorphi?
lampreys. Petromyzontiformes. rays, sharks, and relatives. Chondrichthyes.
What are the basic characteristics of the class Cephalaspidomorphi?
Cephalaspidomorphi were, like most contemporary fishes, very well armoured. The head shield was particularly well developed, protecting the head, gills and the anterior section of the viscera. The body was in most forms well armoured as well.
Does Cephalaspidomorphi have jaws?
Lamprey are by far some of the most primitive fish, along with hagfish. They are called cyclostomes, meaning ’round mouths’ which refers to their lack of jaws.
Do Cephalaspidomorphi have bones?
PHYSICAL CHARACTERISTICS Lampreys (LAM-prees) are scaleless, eel-like fishes that have skeletons of cartilage (KAR-teh-lej) instead of bone.
What are the characteristics of Agnatha?
Key Features of Agnatha
- Jaws are absent.
- Paired fins are generally absent.
- Early species had heavy bony scales and plates in their skin, but these are not present in living species.
- In most cases the skeleton is cartilaginous.
- The embryonic notochord persists in the adult.
- Seven or more paired gill pouches are present.
Do Agnatha lay eggs?
After migrating upstream the males build a rock nest-like structure, the females lay the eggs then the males release their sperm over the nest. Lampreys die shortly after spawning. Lamprey eggs hatch into small larvae (ammocoetes) which are not predators.
Do Petromyzontida have heads?
Most bilaterally symmetrical animals have a head; of these, those that have a cranium comprise the clade Craniata/Vertebrata, which includes the primitively jawless Myxini (hagfishes), Petromyzontida (lampreys), and all of the organisms called “vertebrates.” (We should note that the Myxini have a cranium but lack a …
How big is a hagfish?
16 to 40 inches
Eel-like in shape, hagfishes are scaleless, soft-skinned creatures with paired thick barbels on the end of the snout. Depending on the species, they grow to about 40 to 100 cm (16 to 40 inches) long. Primitive vertebrates, hagfishes have a tail fin (but no paired fins) and no jaws or bones.
Which of the following is an Agnatha?
Agnatha are jawless fish. Lampreys and hagfish are in this class. Members of the agnatha class are probably the earliest vertebrates. Scientists have found fossils of agnathan species from the late Cambrian Period that occurred 500 million years ago.
What is the morphology of Agnatha?
Morphology. In addition to the absence of jaws, modern agnathans are characterised by absence of paired fins; the presence of a notochord both in larvae and adults; and seven or more paired gill pouches. Lampreys have a light sensitive pineal eye (homologous to the pineal gland in mammals).
How do Agnatha breathe?
“Water breathing” through gills which are modified pharyngeal slits. (gas exchange between water and blood). Gills can absorb lower concentrations of available oxygen.
What type of body covering do Agnatha have?
skin
The internal skeleton is made from cartilage and their body covering is skin. They also do not have a proper stomach, but have a long gut which is the same for its entire length.
What kind of body does a Cephalaspidomorphi have?
Cephalaspidomorphi were, like most contemporary fishes, very well armoured. The head shield was particularly well developed, protecting the head, gills and the anterior section of the viscera. The body was in most forms well armoured as well.
Where did the Cephalaspis ostracoderms come from?
Cephalaspis (meaning ‘head shield’) is a genus of armoured fish in the early Devonian about 400 million years ago (mya). It was one of the jawless fishes, or ostracoderms, which were common at the time. They were discovered in the first half of the 19th century in the Old Red Sandstone of Britain.
How are the osteostracans related to the Cephalaspidomorphi?
In the 1920s, the biologists Johan Kiær and Erik Stensiö first recognized the Cephalaspidomorphi as including the osteostracans, anaspids, and lampreys, because all three groups share a single dorsal “nostril”, now known as a nasohypophysial opening. Since then, opinions on the relations among jawless vertebrates have varied.
How are cephalaspidomorphs related to the lampreys?
Jump to navigation Jump to search. Cephalaspidomorphs are a group of jawless fishes named for Cephalaspis of the osteostracans. Most biologists regard this taxon as extinct, but the name is sometimes used in the classification of lampreys, because lampreys were once thought to be related to cephalaspids.