Named for its pale coloration, it is closely related to the more common shovelnose sturgeon (Scaphirhynchus platorynchus), but is much larger, averaging between 30 and 60 inches (76 and 152cm) in length and 85 pounds (39kg) in weight at maturity. This species takes 15years to mature and spawns infrequently, but can live up to a century. A member of the sturgeon family, Acipenseridae, which originated during the Cretaceous period 70million years ago, the pallid sturgeon has changed little since then. (Full article...)
Platyhelminthes (fromAncient Greekπλατύ (platy)'flat'andἕλμινς (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...)
Representative dinosaurs of the Hadrosauroideasuperfamily. The familyHadrosauridae contains the dinosaurs commonly known as "duck-billed" dinosaurs. They were ubiquitous herbivores during the Cretaceous period, and prey to theropoda such as Tyrannosaurus. The individual drawings represent typical genera. All these groups were alive in the late Cretaceous, and are generally known only from a single fossil site. Animals are shown to scale.
The 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 bryozoa are classified as the marine bryozoa (Stenolaemata), freshwater bryozoa (Phylactolaemata), and mostly-marine bryozoa (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. Five genera are solitary: Aethozooides, Aethozoon, Franzenella, Solella, which together make up the family Aethozoidae, and Monobryozoon, which has a statocyst-like organ with a supposed excretory function. (Full article...)
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.
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.
A lateral (left side) anatomical diagram of an adult-stage nematode hermaphroditeCaenorhabditis elegans (full size) with emphasis on the digestive and reproductive systems. C. elegans is a free-living, transparent nematode (roundworm) which measures about 1 millimetre (0.039in) in length. The hermaphrodite form, as seen here, is the most common, although a male form is also found. When self-inseminated, the species will lay about 300 eggs, but when the hermaphrodite is inseminated by a male, the number of progeny can exceed 1,000.
The Peacock flounder (Bothus mancus) is a species of lefteye flounder found widely in relatively shallow waters in the Indo-Pacific. This photomontage shows four separate views of the same fish, each several minutes apart, starting from the top left. Over the course of the photos, the fish changes its colors to match its new surroundings, and then finally (bottom right) buries itself in the sand, leaving only the eyes protruding.
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.
A caterpillar of Lymantria dispar dispar, also known as the gypsy moth. First described by Carl Linnaeus in 1758, the gypsy moth is found throughout Eurasia, where it is considered a pest. The larvae emerge from egg masses in the spring, and then are dispersed by the wind and begin feeding on leaves. They are initially diurnal, but become nocturnal after their fourth molting.
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.
Bolinus cornutus is a predatory species of sea snail, a marine gastropodmollusk in the familyMuricidae. This species is common along the west coast of Africa, where it prefers moderately shallow waters. The shell of the snail is distinctively large, spiny, and club-shaped, usually pale brown or tan in colour, with an elongated and straight siphonal canal.
This list's taxonomic treatment (designation and sequence of orders, families and species) and nomenclature (common and scientific names) follow the conventions of The Clements Checklist of Birds of the World, 2022 edition. All of the birds below are included in the total bird count for Egypt. (Full article...)
...that Caecillians, an order of amphibians resembling snakes or worms, possess a pair of tentacles, located between their eyes and nostrils which are probably used for olfaction?
Image 3A 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)
Image 4A 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 5Linnaeus's table of the animal kingdom from the first edition of Systema Naturae (1735) (from Zoology)
Image 6Non-bilaterian animals include sponges (centre) and corals (background). (from Animal)
Image 21Butterfly wing at different magnifications reveals microstructured chitin acting as diffraction grating. (from Animal coloration)
Image 22Idealised 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 23Fish and frog melanophores are cells that can change colour by dispersing or aggregating pigment-containing bodies. (from Animal coloration)
Image 33The 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)
The following table lists estimated numbers of described extant species for the animal groups with the largest numbers of species, along with their principal habitats (terrestrial, fresh water, and marine), and free-living or parasitic ways of life. 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. 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.
↑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).
↑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.
1234Nicol, David (June 1969). "The Number of Living Species of Molluscs". Systematic Zoology. 18 (2): 251–254. doi:10.2307/2412618. JSTOR2412618.
↑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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