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The first shark-like chondrichthyans appeared in the oceans 400 million years ago, [1] developing into the crown group of sharks by the Early Jurassic. [2] Listed below are extant species of shark. Sharks are spread across 512 described and 23 undescribed species in eight orders. The families and genera within the orders are listed in ...
Until the 16th century, [7] sharks were known to mariners as "sea dogs". [8] This is still evidential in several species termed "dogfish," or the porbeagle.The etymology of the word shark is uncertain, the most likely etymology states that the original sense of the word was that of "predator, one who preys on others" from the Dutch schurk, meaning 'villain, scoundrel' (cf. card shark, loan ...
Threatened species are also referred to as a red-listed species, as they are listed in the IUCN Red List of Threatened Species. [4] In a milestone decision in 2013, CITES prohibited international trade in the fins of the scalloped hammerhead (pictured) and four other shark species. [5]
Outline of sharks. A great white shark at Isla Guadalupe, Mexico. The following outline is provided as an overview of and topical guide to sharks: Sharks ( superorder Selachimorpha) are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 440 million years ago, before the ...
Common names of fish can refer to a single species; to an entire group of species, such as a genus or family; or to multiple unrelated species or groups. Ambiguous common names are accompanied by their possible meanings. Scientific names for individual species and higher taxa are included in parentheses.
This is the only known case of hybridization in sharks. [1] Class Actinopterygii. Order Acipenseriformes. In 2020 hybrids were announced from different families of fish, American paddlefish (Polyodon spathula) and Russian sturgeon (Acipenser gueldenstaedtii). Accidentally created by Hungarian scientists, they are dubbed "sturddlefish." [2]
Chondrichthyes ( / kɒnˈdrɪkθiiːz /; 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. They can be contrasted with the Osteichthyes or bony fish, which have ...
The list of organisms by chromosome count describes ploidy or numbers of chromosomes in the cells of various plants, animals, protists, and other living organisms. This number, along with the visual appearance of the chromosome, is known as the karyotype, [ 1][ 2][ 3] and can be found by looking at the chromosomes through a microscope.