What is the meaning of Holocephali?
The subclass Holocephali (“complete heads”) is a taxon of cartilaginous fish in the class Chondrichthyes. The earliest fossils are of teeth and come from the Devonian period. These fishes move by using sweeping movements of their large pectoral fins.
What is the common name for Chondrichthyes?
chondrichthyan, (class Chondrichthyes), also called chondrichthian, any member of the diverse group of cartilaginous fishes that includes the sharks, skates, rays, and chimaeras.
What is the special feature of Holocephali?
➢ External Features of Holocephali: Body appearance is shark-like but the head is large and compressed, having a small mouth. Operculum is formed by a fold of skin to cover the gill slits so that a single branchial aperture is found. Spiracle and cloaca are absent. Two dorsal and a ventral fin present.
What are differences between elasmobranchii and Holocephali?
What differentiates Holocephalans and Elasmobranchs? The main differences between these two subclasses are the structure of their gills and how they grow in the embryo. Holocephali has four gill slits with a gill cover (an operculum), while Elasmobranchs have five to seven external gill slits with no gill cover.
How many species of Holocephali are there?
The family Chimaeridae (Subclass Holocephali) includes 25 species within 2 genera that can be distinguished by the presence (Chimaera, 7 species) or absence (Hydrolagus, 18 species) of an anal fi n (Bigelow and Schroeder, 1953).
What is Chondrichthyes and Osteichthyes?
Definition. Chondrichthyes refers to a class of fishes that includes those with a cartilaginous skeleton while Osteichthyes refers to a class of fishes that includes those with a bony skeleton.
What does the name Chondrichthyes mean?
Chondrichthyes (/kɒnˈdrɪkθi. iːz/; from Ancient Greek: χονδρ- chondr- ‘cartilage’, ἰχθύς ichthys ‘fish’) is a class that contains the cartilaginous fishes that have skeletons primarily composed of cartilage. Within the infraphylum Gnathostomata, cartilaginous fishes are distinct from all other jawed vertebrates.
Do Holocephali have teeth?
Holocephali differ from Euselachii in respect of the number of gills (they have one gill slit compared with 5–7 in sharks, skates, and rays) and in the fact that their teeth are fused to form plates.
Is Chimera a fish?
Chimaera, ratfish, or ghost shark, strange-looking marine fish belonging to the subclass Holocephali, class Chondrichthyes and thus related to sharks and rays.
What is the definition of a Holocephali fish?
Definition of Holocephali. : a subclass of Chondrichthyes that is sometimes made a separate class, includes the recent chimaeras and certain chiefly extinct related fishes some of which date from Devonian time, and is distinguished by a cartilaginous skeleton, gill clefts covered by a fold of skin, high compressed head with small narrow mouth…
Which is the most extinct order of Holocephali?
Below is a list of the known living and extinct orders of the Holocephali: 1 † Orodontiformes 2 † Petalodontiformes 3 † Helodontiformes 4 † Iniopterygiformes 5 † Debeeriiformes 6 † Eugeneodontiformes 7 † Symmoriida 8 † Psammodontiformes * 9 † Copodontiformes 10 † Squalorajiformes
When did the fossil record of the Holocephali start?
The fossil record of the Holocephali starts during the Devonian period. The record is extensive, but most fossils have teeth, and the body forms of numerous species are not known, or at best poorly understood.
How does a Holocephali move in the sea?
These fishes move by using sweeping movements of their large pectoral fins. Extant Holocephalians have long, slender tails and live close to the seabed feeding on benthic invertebrates. They lack a stomach, their food moving directly into the intestine.