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Chondrichthyes (/ k ɒ n ˈ d r ɪ k θ i iː z /; from Ancient Greek χόνδρος (khóndros) 'cartilage' and ἰχθύς (ikhthús) 'fish') is a class of jawed fish that contains the cartilaginous fish or chondrichthyans, which all have skeletons primarily composed of cartilage.
The olfactory lobes are very large in fish that hunt primarily by smell, such as hagfish, sharks, and catfish. Behind the olfactory lobes is the two-lobed telencephalon, the structural equivalent to the cerebrum in higher vertebrates. In fish the telencephalon is concerned mostly with olfaction. [59] Together these structures form the forebrain.
Bony fish can be further divided into those with lobe fins and those with ray fins. Lobe fins have the form of fleshy lobes supported by bony stalks which extend from the body. [16] Lobe fins evolved into the legs of the first tetrapod land vertebrates, so by extension an early ancestor of humans was a lobe-finned fish.
Lungfish are freshwater vertebrates belonging to the class Dipnoi. [1] Lungfish are best known for retaining ancestral characteristics within the Osteichthyes, including the ability to breathe air, and ancestral structures within Sarcopterygii, including the presence of lobed fins with a well-developed internal skeleton.
Major groups of fish evolved during this period, often referred to as the age of fish. [39] See Category:Devonian fish. D e v o n i a n: Early Devonian: Early Devonian (419–393 Ma): Psarolepis: Psarolepis (speckled scale) is a genus of extinct lobe-finned fish that lived around 397 to 418 Ma.
Osteichthyes (/ ˌ ɒ s t iː ˈ ɪ k θ iː z / ost-ee-IK-theez; from Ancient Greek ὀστέον (ostéon) 'bone' and ἰχθύς (ikhthús) 'fish'), [2] also known as osteichthyans or commonly referred to as the bony fish, is a diverse superclass of vertebrate animals that have endoskeletons primarily composed of bone tissue.
Rhenanida ("Rhine fish") were flattened, ray-like, bottom-dwelling predators with large, upturned mouths that lived in marine environments. The rhenanids were once presumed to be the most primitive, or at least the closest to the ancestral placoderm, as their armour was made of unfused components—a mosaic of tubercles—as opposed to the ...
While the houndfish has no spines, its dorsal fin has 21–25 soft rays, and its anal fin has 19–22. [2] They are also known to have 80–86 vertebrae. [2] A key way of distinguishing the houndfish from other members of the genus Tylosurus is that the houndfish's teeth point anteriorly when the fish is a juvenile.