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The origins and evolutionary relationships between the three main groups of amphibians (apodans, urodeles and anurans) is a matter of debate.A 2005 molecular phylogeny, based on rDNA analysis, suggested that the first divergence between these three groups took place soon after they had branched from the lobe-finned fish in the Devonian (around 360 million years ago), and before the breakup of ...
Agnatha (/ ˈ æ ɡ n ə θ ə, æ ɡ ˈ n eɪ θ ə /; [3] from Ancient Greek ἀ-(a-) 'without' and γνάθος (gnáthos) 'jaws') is a paraphyletic infraphylum [4] of non-gnathostome vertebrates, or jawless fish, in the phylum Chordata, subphylum Vertebrata, consisting of both living (cyclostomes) and extinct (conodonts, anaspids, and ostracoderms, among others).
[14] [15] The fish lived in both freshwater and marine environments, first appearing during the Ordovician, and perishing during the Frasnian–Famennian extinction event of the Late Devonian. They were predominantly deposit-feeding bottom dwellers, although there is evidence to suggest that some species took to the water column to be free ...
The vertebrates include mammals, birds, amphibians, and various classes of fish and reptiles. The fish include the jawless Agnatha, and the jawed Gnathostomata. The jawed fish include both the cartilaginous fish and the bony fish. Bony fish include the lobe-finned fish, which gave rise to the tetrapods, the animals with four
The smallest amphibian (and vertebrate) in the world is a frog from New Guinea (Paedophryne amauensis) with a length of just 7.7 mm (0.30 in). The largest living amphibian is the 1.8 m (5 ft 11 in) South China giant salamander ( Andrias sligoi ), but this is dwarfed by prehistoric temnospondyls such as Mastodonsaurus which could reach up to 6 m ...
Hagfish form a class of about 20 species of eel-shaped, slime-producing marine fish. They are the only known living animals that have a skull but no vertebral column. Lampreys form a superclass containing 38 known extant species of jawless fish. [3] The adult lamprey is characterized by a toothed, funnel-like sucking mouth.
China, by far the world's largest shark market, and Japan, which battles all attempts to extend the convention to marine species, led the opposition. [ 179 ] [ 180 ] In March 2013, three endangered commercially valuable sharks, the hammerheads , the oceanic whitetip and porbeagle were added to Appendix 2 of CITES , bringing shark fishing and ...
Bryozoa, also known as moss animals or sea mats; Chaetognatha, commonly known as arrow worms, are a phylum of predatory marine worms that are a major component of plankton; Cephalochordata represented in the modern oceans by the lancelets (also known as Amphioxus); Cnidaria, such as jellyfish, sea anemones, and corals;