Apart from this website, there does not seem to be any comprehensive list of images of extant animal species anywhere on the internet. There are lists of species and lists of photos, but not both together. For reptiles, amphibians and fishes there are more complete lists, but there are several large gaps in the number of images. Birds on the other hand are better served with images, but not all together in one site.
Scientists differ as to the number of extant animal species there are on the planet, so I have made lists compiled from several sources, and found 6,033 mammals (of which 1,413 are bats), 10,270 reptiles, 9,564 birds, 7,133 amphibians and no fewer than 34,068 fishes. When it comes to crustaceans, molluscs and echinoderms there are so many different species known to science that it is only practical to list every genus (9,701 crustaceans, 8,189 molluscs and 1,245 echinoderms on my lists) with a selected species and image (where available) for each one. Insects, arachnids, annelids, other arthropds, cnidarians, parasitic worms, sponges and tunicates are even more numerous so I have only shown every family (subfamilies for ants and butterflies) with a selected genus and species. On my lists there are 1,184 insect families, 712 arachnid families, 236 other arthropod families, 146 annelid families, 456 cnidarian families, 723 parasitic worm families, 350 sponge families and 35 tunicate families.
The purpose of this website is to put in one place an image of as many of these species as can be found on the internet. (Obviously most of the images of gastropods and bivalves are of their shells). In doing this we have to take on trust the identification of the species by the photographer (or by the website that published them), so it is wise to treat them with a certain amount of caution. Additionally many of the photos on the internet are copyrighted in some way, so I have just presented a thumbnail 60 pixels high. The crustacean, mollusc and echinoderm images are nearly all of the selected species and are certainly of the relevant genus.
The main sources for the list of mammals are "Mammal Species of the World" (MSW) maintained by the Smithsonian, The "Animal Diversity Web" (ADW) maintained by the University of Michigan and of course Wikipedia. For reptiles the most authoritative source is "The Reptile Database" (RDB), now maintained in the Czech Republic. For birds I have used the Wikipedia bird list (WBL) which is constantly being kept up to date. For amphibians I have used "Amphibiaweb" (AMP), which appears to be the most authoritative (although for common or "vernacular" names Wikispecies is more thorough). Fishes are a great deal more complicated. Most of them are classed as Actinopterygii or Ray-finned fishes, but there are over 1,000 Cartilaginous fishes classed as Condrichthyes (mostly sharks and rays), Holocephali (Chimaeras), a few Lobe-finned fishes classed as Sarcopterygii (lung-fishes and coelacanths) and several primitive fishes or fish-like creatures such as Hagfishes, Lampreys and Lancelets, classed as Myxini, Cephalaspidomorphi and Leptocardii. I have used "Fishbase" (FBS), where the only weaknesses appear to be some strange anomalies and gaps in the lists of common names. For the crustaceans, molluscs and echinoderms I have used Wikipedia and Wikispecies, but the main source is the "World Register of Marine Species" (WoRMS). For insects I have used The Royal Entomology Society (RES) for the basic classification as well as Wikipedia, which is also a main source for arachnids and annelids. Final checklists for all animals are "The Catalogue of Life" (CoL) and the "Integrated Taxanomic Information System"(ITIS).
I have ignored most of the sub-divisions beloved of taxonomists, such as sub-orders, clades, tribes etc - I have just listed the species alphabetically by Order, Family, Genus and Species. (This means, among other things, that the poor old aardvark comes last instead of first in the list of mammals). One exception to this is the order Squamata of reptiles, which I have split into Amphisbaenia (Worm Lizards), Sauria (Lizards) and Serpentes (Snakes). Another exception is crustaceans, where I have listed them not by Order but by commonly used English name (Barnacles, Crabs, Lobsters etc). For convenience I have included comb jellies with the cnidarians, sipuncula with the annelids, brachypods with the crustaceans, several microscopic creatures such as wheel animals and water bears with the parasitic worms and bryozoans and entoprocts with the sponges.There are many sources for the images themselves, and also many museums, zoos and specialized societies maintain their own lists of images. There does not seem to be a single source - maybe this website fills a small gap.
The main groups of animals are:
The Orders and families on this website are: