The family tree of fishes, showing the evolution of major groups through geological time. Numerous lineages of extinct fishes are not shown. Widened areas in the lines of descent indicate periods of adaptive radiation and the relative number of species in each group. The lobe-finned fishes (sarcopterygians), for example, flourished in the Devonian period, but declined and are today represented by only four surviving genera (lungfishes and coelacanths). Sharks and rays, which radiated during the Carboniferous period, came dangerously close to extinction during the Permian period, but staged a recovery in the Mesozoic era and are a secure group today.

Photo © Hickman et al. (2003)

Insects from the family Fulgoridae are often collectively referred to as lantern bugs. They belong to the order Hemiptera, which encompasses all true bugs. Fulgorids—especially those from the tropics—are known for their oblong heads. These insects typically rest and feed during the day and fly at night. When Fulgorids lay their eggs, they also exude a frothy secretion which hardens around the eggs to protect them.
A wart-headed bug (Phrictus quinquepartitus) is shown above.

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Coming in an array of blues and greens, the green and black poison-dart frog (Dendrobates auratus) belongs to a family of nearly 180 species that includes some of the most poisonous amphibians in the world.

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Considering most cardinalfish rarely reach longer than 10 cm in length, the deep-sea black cardinalfish (Epigonus telescopus) is an enormous cousin in the same order, but a different family than typical cardinalfish. The shallow-water cardinalfish most people are familiar with are in the family Apogonidae, but deep-sea cardinalfish belong to the family Epigonidae.

Photo © Pheobe Forrester

Bullhead and horn sharks belong to the order Heterodontiformes, and are small, bottom-living sharks. The most popular species is Heterodontus portusjacksoni, the Port Jackson shark. There are only nine species within this order.

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Phylum Cnidaria (meaning nettle-like) is an interesting group of more than 9000 species. It takes its name from cells called cnidocytes, which contain the stinging organelles called nematocysts. Nematocysts are formed and used only by cnidarians. Another name for the phylum, Coelenterata (meaning hollow gut) is used less commonly than formerly, and it sometimes now refers to both radiate phyla (Cnidarians and Ctenophores), since it’s meaning is equally applicable to both.

The phylum Cnidaria includes some of nature’s strangest and loveliest creatures: branching, plantlike hydroids; flowerlike sea anemones; jellyfishes; and those architects of the ocean floor, horny corals and stony corals.

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Order Thysanura, home to silverfish and firebrats.

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This post comes to you in the form of a question. Yay, questions!

So, on a literary adventure over the summer, I read through this lovely compendium of knowledge:

Obviously I didn’t read every single entry for every single animal, but I thumbed through it and found a wildly large number of animals that I was very interested in and had never heard of before. I also took the opportunity to read more about animals I already know a lot about, such as the hagfish (pictured above).
I’ve always regarded hagfish to belong to the superclass Agnatha (jawless fishes, generally consisting of hagfish and lamprey eels), but the book stated that hagfish were recently placed in the superclass Osteichthyes (bony fishes, including most fish you can think of but not including sharks or rays).
I don’t remember the publication date of the book, and to be honest, the writing in it is TERRIBLE in both grammar and syntax, but it is from the Smithsonian Institution, so it must be somewhat credible, right?
Anynoodle, I was wondering if anyone had any knowledge on this, and if so, could you please let me know? Thanks!

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Animals in the phylum Cnidaria are often classified into four classes: Hydrozoa, Scyphozoa, Cubozoa, and Anthozoa. “Cnidaria” means “stinging nettle,” and animals are classified in this phylum for possessing stinging cells called nematocysts.

Hydrozoa - Siphonophores and Hydra (3,600 species) (Photo source)
Scyphozoa - Jellyfish (228 species) (Photo source)
Cubozoa - Box Jellies (42 species) (Photo source)
Anthozoa - Sea Anemones, Corals, and Sea Pens (6,100 species) (Photo source)

Echinodermata is a taxonomic phylum whose name means “spiny-skin.” This phylum includes six different classes of animals: Crinoidea, Asteriodea, Ophiuroidea, Echinoidea, Holothuroidea,and Concentricycloidea.

Crinoidea - Sea Lilies and Feather Stars (630 species) (Photo source)
Asteroidea - Starfish (1,500 species) (Photo source) 
Ophiuroidea - Brittlestars (2,000 species) (Photo source) 
Echinoidea - Sea Urchins (940 species) (Photo source) 
Holothuroidea - Sea Cucumbers (1,150 species) (Photo source) 
Concentricycloidea - Sea Daisies (2 species) (Photo source)