Entries here consist of Good and Featured articles, which meet a core set of high editorial standards.
The Galápagos tortoise (Chelonoidis niger), also called the Galápagos giant tortoise, is a very large species of tortoise in the genusChelonoidis (which also contains three smaller species from mainland South America). The species comprises 15 subspecies (12 extant and 3 extinct). It is the largest living species of tortoise, and can weigh up to 417kg (919lb). They are also the largest extant terrestrial cold-blooded animals (ectotherms).
With lifespans in the wild of over 100 years, it is one of the longest-lived vertebrates. Captive Galapagos tortoises can live up to 177 years. For example, a captive individual, Harriet, lived for at least 175years. Spanish explorers, who discovered the islands in the 16th century, named them after the Spanish galápago, meaning "tortoise". (Full article...)
The eastern grey kangaroo (Macropus giganteus) is a marsupial found in the eastern third of Australia, with a population of several million. The eastern grey kangaroo is the second largest living marsupial and native land mammal in Australia, with adult males weighing around 50 to 66kg (110 to 146lb) and females weighing around 17 to 40kg (37 to 88lb). Like all kangaroos, it is mainly nocturnal and crepuscular, and is mostly seen early in the morning, or as the light starts to fade in the evening. In the middle of the day, kangaroos rest in the cover of the woodlands and graze there. Kangaroos are the only large mammals to hop on two legs as their primary means of locomotion. This multiple exposure photograph shows an eastern grey kangaroo hopping in Mount Annan, New South Wales.
Velodona togata is the only species in the octopus genus Velodona; the genus and species names come from the large membranes that connect its arms. It was first described by Carl Chun in his book Die Cephalopoden (from which this illustration is taken) in 1915. A second subspecies was described by Guy Coburn Robson in 1924.
The golden toad (Bufo periglenes) is an extinct species of true toad that was once abundant in a small region of high-altitude cloud-covered tropical forests, about 30km2 (12sqmi) in area, above the city of Monteverde, Costa Rica. The last reported sighting of a golden toad was on 15 May 1989. Its sudden extinction may have been caused by chytrid fungus and extensive habitat loss.
Aplysina archeri is a species of sponge that has long tube-like structures of cylindrical shape. Many tubes are attached to one particular part of the organism; a single tube can grow up to 5 feet (1.5m) high and 3 inches (7.6cm) thick. These sponges mostly live in the Atlantic Ocean. These filter feeders eat food such as plankton or suspended detritus as it passes them.
The plains zebra (Equus quagga, subspecies Grant's zebra pictured) is the most common and geographically widespread species of zebra. It ranges from the south of Ethiopia through East Africa to as far south as Angola and eastern South Africa. The plains zebra is mid-sized, smaller on average than the other two zebra species, and thick-bodied with relatively short legs. Adults of both sexes can stand from 1.1 to 1.47m (3.6 to 4.8ft) high at the shoulder, are 2 to 2.5m (6.6 to 8.2ft) long (excluding the tail), and weigh 175 to 387kg (386 to 853lb), with males slightly heavier than females.
Platyhelminthes (from Ancient Greekπλατύ platy'flat' and ἕλμινς helmins'parasitic worm') is a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrates commonly called flatworms or flat worms. Being acoelomates (having no body cavity), and having no specialised circulatory and respiratoryorgans, they are restricted to having flattened shapes that allow oxygen and nutrients to pass through their bodies by diffusion. The digestive cavity has only one opening for both ingestion (intake of nutrients) and egestion (removal of undigested wastes); as a result, the food can not be processed continuously. (Full article...)
Haliotis laevigata is a species of marine mollusc in the family Haliotidae, endemic to Tasmania and the southern and western coasts of Australia. This picture shows five views of a green H.laevigata shell, 7.5 centimetres (3.0in) in length. The holes in the shell, characteristic of abalones, are respiratory apertures for venting water from the gills and for releasing sperm and eggs into the water column.
The rock hyrax (Procavia capensis), also known as the dassie, is one of four living species of the order Hyracoidea, and the only living species in its genus. Like all hyraxes, it is a medium-sized terrestrial mammal between 4kilograms (9lb) and 5kilograms (11lb) in mass, with short ears and tail. The rock hyrax is found across Africa and the Middle East, at elevations up to 4,200 metres (13,800ft). It resides in habitats with rock crevices which it uses to escape from predators. Along with the other hyrax species and the manatee, these are the animals most closely related to the elephant.
The Atlantic spadefish is a species of marine fish endemic to the shallow waters off the coast of the southeastern United States and in the Caribbean Sea. They are similar in appearance to fresh waterangelfish, but much larger, reaching up to three feet (0.9 m) in length. Due to their reputation as strong fighters, they are popular game fish, especially during the summer months when they are most active.
Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals) are a phylum of simple, aquaticinvertebrate animals, nearly all living in sedentary colonies. Typically about 0.5 millimetres (1⁄64in) long, they have a special feeding structure called a lophophore, a "crown" of tentacles used for filter feeding. The bryozoans are classified as the marine bryozoans (Stenolaemata), freshwater bryozoans (Phylactolaemata), and mostly-marine bryozoans (Gymnolaemata), a few members of which prefer brackish water. Most marine bryozoans live in tropical waters, but a few are found in oceanic trenches and polar waters. 5,869living species of bryozoa are known. Originally all of the crown group Bryozoa were colonial, but as an adaptation to a mesopsammal (interstitial spaces in marine sand) life or to deep-sea habitats, secondarily solitary forms have since evolved. Solitary species have been described in four genera: Aethozooides, Aethozoon, Franzenella, and Monobryozoon, the latter having a statocyst-like organ with a supposed excretory function. (Full article...)
A cross section of a post-clitellum segment of an annelid (ringed worm); almost all segments of an annelid contain the same set of organs and parts, a pattern called metamerism. Annelids have no lungs, but rather exchange carbon dioxide and oxygen directly through the moist skin when blood reaches the extremely fine capillaries of the body walls; a dry worm cannot breathe and will die of suffocation. The worm's red blood, which does not consist of platelets or red cells but mostly of a liquid containing suspended hemoglobin, makes a circuit up and down the animal in its closed circulatory systems.
Sexual dimorphism is the condition where the two sexes of the same species exhibit different characteristics. Differences may include secondary sex characteristics, size, weight, color, or markings, as well as behavioral and cognitive differences. In the butterfly species Colias dimera (also known as the Dimera sulphur), seen here mating in Venezuela, the male on the right is a brighter shade of yellow than the female.
An illustration of various Pulmonata (and one predator arthropod in the lower right), an informal group of snails and slugs characterized by the ability to breathe air, by virtue of having a pallial lung instead of a gill, or gills. Pulmonata was previously a formal taxon but lost its status as one in 2010. The group includes many land and freshwater families, and several marine families. Most species have a shell, but no operculum, although the group does also include several shell-less slugs. Pulmonates are hermaphroditic, and some groups possess love darts.
The sperm whale is the largest toothed animal on Earth. The species was hunted extensively by humans throughout history, until protected by a worldwide moratorium on whaling starting in 1985–86.
Brittle stars, serpent stars, or ophiuroids (from Latin ophiurus'brittle star'; from Ancient Greekὄφις (óphis)'serpent' and οὐρά (ourá)'tail'; referring to the serpent-like arms of the brittle star) are echinoderms in the class Ophiuroidea, closely related to starfish. They crawl across the sea floor using their flexible arms for locomotion. The ophiuroids generally have five long, slender, whip-like arms which may reach up to 60cm (24in) in length on the largest specimens. (Full article...)
The common clam worm (Alitta succinea) is a widely distributed species of marine polychaete worm. The photograph shows an epitoke specimen, the worm having turned into a form capable of reproduction. After releasing its sperm or eggs, the animal will die.
Felidae is a family of mammals in the orderCarnivora, colloquially referred to as cats. A member of this family is called a felid. The term "cat" refers both to felids in general and specifically to domestic cats. The characteristic features of cats have evolved to support a carnivorous lifestyle, with adaptations for ambush or stalking and short pursuit hunting. They have slender muscular bodies, strong flexible forelimbs and retractable claws for holding prey, dental and cranial adaptations for a strong bite, and often have characteristic striped or spotted coat patterns for camouflage. (Full article...)
...that Lampreys are called "nine-eyed eels" (i.e., per side) from a counting of their seven external gill slits on a side with one eye and the nostril?
Image 4A clade representation of seven dog breeds in relation to wolves. (from Zoology)
Image 5The microscopic cave snail Zospeumtholussum, found at depths of 743 to 1,392m (2,438 to 4,567ft) in the Lukina Jama–Trojama cave system of Croatia, is completely blind with a translucent shell (from Fauna)
Image 6Bright coloration of orange elephant ear sponge, Agelas clathrodes signals its bitter taste to predators (from Animal coloration)
Image 9Idealised nephrozoan body plan. With an elongated body and a direction of movement the animal has head and tail ends. Sense organs and mouth form the basis of the head. Opposed circular and longitudinal muscles enable peristaltic motion. (from Animal)
Image 12A praying mantis in deimatic or threat pose displays conspicuous patches of colour to startle potential predators. This is not warning coloration as the insect is palatable. (from Animal coloration)
Image 13The black and yellow warning colours of the cinnabar moth caterpillar, Tyria jacobaeae, are avoided by some birds. (from Animal coloration)
Image 17The bilaterian gut develops in two ways. In many protostomes, the blastopore develops into the mouth, while in deuterostomes it becomes the anus. (from Animal)
Image 43Butterfly wing at different magnifications reveals microstructured chitin acting as diffraction grating. (from Animal coloration)
Image 44A brilliantly-coloured oriental sweetlips fish (Plectorhinchus vittatus) waits while two boldly-patterned cleaner wrasse (Labroides dimidiatus) pick parasites from its skin. The spotted tail and fin pattern of the sweetlips signals sexual maturity; the behaviour and pattern of the cleaner fish signal their availability for cleaning service, rather than as prey. (from Animal coloration)
The following table lists estimated numbers of described extant species for the animal groups with the largest numbers of species,[1] along with their principal habitats (terrestrial, fresh water,[2] and marine),[3] and free-living or parasitic ways of life.[4] Species estimates shown here are based on numbers described scientifically; much larger estimates have been calculated based on various means of prediction, and these can vary wildly. For instance, around 25,000–27,000 species of nematodes have been described, while published estimates of the total number of nematode species include 10,000–20,000; 500,000; 10 million; and 100 million.[5] Using patterns within the taxonomic hierarchy, the total number of animal species—including those not yet described—was calculated to be about 7.77 million in 2011.[6][7][a]
The application of DNA barcoding to taxonomy further complicates this; a 2016 barcoding analysis estimated a total count of nearly 100,000 insect species for Canada alone, and extrapolated that the global insect fauna must be in excess of 10 million species, of which nearly 2 million are in a single fly family known as gall midges (Cecidomyiidae).[8]
Stork, Nigel E. (January 2018). "How Many Species of Insects and Other Terrestrial Arthropods Are There on Earth?". Annual Review of Entomology. 63 (1): 31–45. doi:10.1146/annurev-ento-020117-043348. PMID28938083. S2CID23755007. Stork notes that 1m insects have been named, making much larger predicted estimates.
Sluys, R. (1999). "Global diversity of land planarians (Platyhelminthes, Tricladida, Terricola): a new indicator-taxon in biodiversity and conservation studies". Biodiversity and Conservation. 8 (12): 1663–1681. doi:10.1023/A:1008994925673. S2CID38784755.
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