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Elasmobranchii is one of the two subclasses of cartilaginous fish in the class Chondrichthyes, the other being Holocephali . Members of the elasmobranchii subclass have no swim bladders, five to seven pairs of gill clefts opening individually to the exterior, rigid dorsal fins, and small placoid scales. The teeth are in several series; the ...
The pair then parts, the female being left with scars on her fin. [33] [12]: 46 The fertilized eggs develop within the female's oviduct. At first, they are enclosed in an egg case while the developing embryos absorb the yolk. After hatching, the pups remain in the oviduct and receive additional nutrition from milky secretions called histotroph ...
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 solidified plates of "advanced" placoderms, such as antiarchs and arthrodires. However, through comparisons of skull anatomies, rhenanids are ...
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).
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At present, it is known to exist only in the eastern Arabian Sea, parts of South Asia and Australia and Papua New Guinea. [2] The narrow sawfish is bentho-pelagic and is found at depths of about 100 meters (330 feet). The narrow sawfish prefers soft bottom-substrates, such as sand, mud, or seagrass, to rocky or coraline habitats.
WASHINGTON (Reuters) -Donald Trump has tapped Keith Kellogg, a retired lieutenant general who presented him with a plan to end the war in Ukraine, to serve as a special envoy for the conflict, the ...
One by one, diversity, equity and inclusion programs at some of the country’s biggest companies fell apart in 2024, with signs that efforts to reverse DEI initiatives will only ramp up in 2025.