Search results
Results from the WOW.Com Content Network
Regions of a Chondrichthyes brain colored and labeled on dissected skate. The rostral end of the skate is to the right. In chondrichthyans, the nervous system is composed of a small brain, 8–10 pairs of cranial nerves, and a spinal cord with spinal nerves. [11] They have several sensory organs which provide information to be processed.
Specimen of "Hybodus" fraasi from the Late Jurassic of Germany, which some studies have included in Egertonodus Skeletal diagram of Hybodus sp.The largest hybodonts reached lengths of 2–3 metres (6.6–9.8 ft), [4] while some other hybodonts were much smaller, with adult body lengths of around 25 centimetres (0.82 ft). [5]
Several synapomorphies support this hypothesis, such as the presence of: sclerotic ossicles, paired pectoral fins, a dermal skeleton with three layers (a basal layer of isopedin, a middle layer of spongy bone, and a superficial layer of dentin), and perichondral bone. [10] Other groups Other groups † Pteraspido-morphi (extinct)
The skate belongs to the class Chondrichthyes. This class consists of all the cartilaginous fishes, including sharks and stingrays. Chondrichthyes is divided into two subclasses; of which Elasmobranchii includes skates, rays, and sharks. Skates are the most diverse elasmobranch group, comprising over 20% of the known species.
The following is the full list of the extant species in Class Chondrichthyes, or the cartilaginous fish. Members of this class have a backbone , gills , no swim bladder , jaws , and a skeleton made of cartilage , a soft, strong material as a replacement for bone .
The anatomy of Cladoselache shows a mixture of derived and ancestral characteristics. The skeleton is composed of tessellated cartilage , a complex tissue unique to chondrichthyans. Tessellated cartilage combines flexible cartilage fibers with a loose mosaic of irregular calcified plates, known as tesserae.
Fishes are a paraphyletic group and for this reason, the class Pisces seen in older reference works is no longer used in formal taxonomy.Traditional classification divides fish into three extant classes (Agnatha, Chondrichthyes, and Osteichthyes), and with extinct forms sometimes classified within those groups, sometimes as their own classes: [1]
Chondrichthyes is a monophyletic group characterized by the development of endoskeletal tesserae (mineralized blocks of cartilage) and internal fertilization. [23] Chondrichthyes is further divided into two subclasses: Elasmobranchii and Holocephali. Stethacanthids have been classified as a member of the group Paleoselachii, which is a ...