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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).
The vertebrates make up the subphylum Vertebrata with some 65,000 species, by far the largest grouping in the phylum Chordata. The vertebrates include mammals , birds , amphibians , and various classes of fish and reptiles .
The subphyla Tunicata and Vertebrata are in the unranked Olfactores clade, while the subphylum Cephalochordata is not. Animals in Olfactores are characterized as having a more advanced olfactory system than animals not in it. The only extinct classes shown are Placodermi and Acanthodii. Note that there are many other extinct chordate groups ...
Taxonomists place lampreys and hagfish in the subphylum Vertebrata of the phylum Chordata, which also includes the invertebrate subphyla Tunicata (sea-squirts) and the fish-like Cephalochordata (lancelets or Amphioxus).
Superclass 2. Gnathostomata. Class Elasmobranchii (= Chondrichthyes) [p. 175] . Subclass 1. Selachii. Order 1. †Cladoselachii (e.g., †Cladoselache, †Goodrichia ...
Here are some of the tick species that experts worry most about from a public health perspective: Blacklegged ticks, also called deer ticks, which transmit the bacteria that causes Lyme disease ...
By species count, they dominate the subphylum Vertebrata, and constitute nearly 99% of the over 30,000 extant species of fish. [4] They are the most abundant nektonic aquatic animals and are ubiquitous throughout freshwater and marine environments from the deep sea to subterranean waters to the highest mountain streams.
Plus, symptoms and expert tips to help identify and treat insect bites. These photos of 11 common bug bites and stings can help you identify what's responsible. Plus, symptoms and expert tips to ...