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57-460: The fennec fox ( Vulpes zerda ) is a small crepuscular fox native to the deserts of North Africa, ranging from Western Sahara and Mauritania to the Sinai Peninsula . Its most distinctive feature is its unusually large ears, which serve to dissipate heat and listen for underground prey. The fennec is the smallest fox species. Its coat, ears, and kidney functions have adapted to

114-549: A backbone or spine, consisting of vertebrae and intervertebral discs . The vertebrae are irregular bones , and the intervertebral discs are of fibrocartilage . The vertebral column surrounds and protects the spinal cord . The other feature unique to vertebrates is the presence of a cranium , or skull. The vertebrates make up the subphylum Vertebrata with some 65,000 species in the phylum Chordata . The vertebrates include mammals , birds , amphibians , and various classes of reptiles and fish . Classes of fish include

171-427: A jaw , hyoid and/or the middle ear ossicles . An iodine-concentrating organ called the endostyle , which functions as a filter feeding organ in aquatic animals has evolved into the thyroid in most vertebrates. Vertebrates vary in body length ranging from the frog species Brachycephalus pulex , a Brazilian flea toad, with a minimum adult snout–vent length of 6.45 millimetres (0.254 in) to

228-417: A central nervous system arising from a single nerve cord dorsal to the gut tube , headed by a series of (typically paired) brain vesicles, is unique to vertebrates. This is in stark contrast to invertebrates with well-developed central nervous systems such as arthropods and cephalopods , which have an often ladder-like ventral nerve cord made of paired segmental ganglia on the opposite ( ventral ) side of

285-525: A hollow neural tube ) running along the dorsal aspect of the notochord . Of particular importance and unique to vertebrates is the presence of neural crest cells, which are progenitor cells critical to coordinating the functions of cellular components. Neural crest cells migrate through the body from the dorsal nerve cord during development, initiate the formation of neuronal ganglia and various special sense organs. The peripheral nervous system forms when neural crest cells branch out laterally from

342-589: A protein related to ubiquitin carboxyl-terminal hydrolase are exclusively shared by all vertebrates and reliably distinguish them from all other animals. A specific relationship between vertebrates and tunicates is strongly supported by two CSIs found in the proteins Rrp44 (associated with the exosome complex ) and serine palmitoyltransferase . These are exclusively shared by species from these two subphyla, but not cephalochordates . This indicates hat vertebrates are more closely related to tunicates than cephalochordates. The "Notochordata hypothesis" suggested that

399-606: A series of crescentic openings from the pharynx to the outside. Each gill is supported by a cartilaginous or bony gill arch , which develop embryonically from pharyngeal arches . Bony fish have three pairs of gill arches, cartilaginous fish have five to seven pairs, while the primitive jawless fish have seven pairs. The ancestral vertebrates likely had more arches than seven, as some of their chordate relatives have more than 50 pairs of gill opens, although most, if not all, of these openings are actually involved in filter feeding rather than respiration . In jawed vertebrates ,

456-456: A single chamber. Captive individuals reside in family groups consisting of several members. Fennec foxes exhibit playful behavior, especially among younger individuals. The fennec fox is omnivorous, feeding on small rodents , lizards ( geckos and skinks ), small birds and their eggs, insects, fruits, leaves , roots and also some tubers . It relies on the moisture content of prey, but drinks water when available. It hunts alone and digs in

513-909: Is distributed throughout the Sahara, from Morocco and Mauritania to northern Sudan , through Egypt and its Sinai Peninsula . It inhabits small sand dunes and vast treeless sand areas with sparse vegetation such as grasses, sedges and small shrubs. Fennec foxes are primarily nocturnal, displaying heightened activity during the cooler nighttime hours. This behaviour helps them escape the extreme Saharan heat and reduces water loss through panting. A fennec fox digs its den in sand, either in open areas or places sheltered by plants with stable sand dunes . In compacted soils, dens are up to 120 m (1,300 sq ft) large, with up to 15 different entrances. In some cases, different families interconnect their dens, or locate them close together. In soft, looser sand, dens tend to be simpler with only one entrance leading to

570-440: Is found in invertebrate chordates such as lancelets (a sister subphylum known as the cephalochordates ), though it lacks eyes and other complex special sense organs comparable to those of vertebrates. Other chordates do not show any trends towards cephalization. The rostral end of the neural tube is expanded by a thickening of the walls and expansion of the central canal of spinal cord into three primary brain vesicles :

627-581: Is normally active during the day, but on islands like Santa Cruz that are home to the Galapagos hawk , the owl is crepuscular. Apart from the relevance to predation, crepuscular activity in hot regions also may be the most effective way of avoiding heat stress while capitalizing on available light. Crepuscular flight activity is preferred by some animals, such as the walnut twig beetle , due to warmer temperatures, moderate wind speeds, and low barometric pressure. Crepuscular activity can be influenced by

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684-509: Is the smallest canid species. Females range in head-to-body size from 34.5 to 39.5 cm (13.6 to 15.6 in) with a 23–25 cm (9.1–9.8 in) long tail and 9–9.5 cm (3.5–3.7 in) long ears, and weigh 1–1.9 kg (2.2–4.2 lb). Males are slightly larger, ranging in head-to-body size from 39 to 39.5 cm (15.4 to 15.6 in) with a 23–25 cm (9.1–9.8 in) long tail and 10 cm (3.9 in) long ears, weighing at least 1.3 kg (2.9 lb). The fennec fox

741-635: The Cephalochordata is the sister taxon to Craniata (Vertebrata). This group, called the Notochordata, was placed as sister group to the Tunicata (Urochordata). Studies since 2006 analyzing large sequencing datasets however strongly support Olfactores (tunicates + vertebrates) as a clade, and hence the placement of Cephalochordata as sister-group to Olfactores (known as the " Olfactores hypothesis "). The following cladogram summarizes

798-559: The Chengjiang biota and lived about 518 million years ago. These include Haikouichthys , Myllokunmingia , Zhongjianichthys , and probably Haikouella . Unlike the other fauna that dominated the Cambrian, these groups had the basic vertebrate body plan: a notochord, rudimentary vertebrae, and a well-defined head and tail. All of these early vertebrates lacked jaws in the common sense and relied on filter feeding close to

855-474: The Izu–Ogasawara Trench at a depth of 8,336 metres (27,349 feet). Many fish varieties are the main predators in most of the world's freshwater and marine water bodies . The rest of the vertebrate species are tetrapods, a single lineage that includes amphibians (with roughly 7,000 species); mammals (with approximately 5,500 species); and reptiles and birds (with about 20,000 species divided evenly between

912-633: The Jurassic . The Cenozoic world saw great diversification of bony fishes, amphibians, reptiles, birds and mammals. Over half of all living vertebrate species (about 32,000 species) are fish (non-tetrapod craniates), a diverse set of lineages that inhabit all the world's aquatic ecosystems, from the Tibetan stone loach ( Triplophysa stolickai ) in western Tibetan hot springs near Longmu Lake at an elevation of 5,200 metres (17,100 feet) to an unknown species of snailfish (genus Pseudoliparis ) in

969-464: The Latin vertebratus ("jointed"), from vertebra meaning "joint", in turn from Latin vertere to turn. All vertebrates are built along the basic chordate body plan of five synapomorphies . These are a rigid axial skeleton that includes a vertebral column developed around an elastic notochord . The notochord becomes the intervertebral discs , and runs dorsally to the gut tube along

1026-462: The Latin crepusculum ("twilight"). Its sense accordingly differs from diurnal and nocturnal behavior, which respectively peak during hours of daytime and night. The distinction is not absolute, because crepuscular animals may also be active on a bright moonlit night or on a dull day. Some animals casually described as nocturnal are in fact crepuscular. Special classes of crepuscular behaviour include matutinal, or "matinal", animals active only in

1083-574: The Placodermi and the Acanthodii , both considered paraphyletic . Other ways of classifying the vertebrates have been devised, particularly with emphasis on the phylogeny of early amphibians and reptiles. An example based on Janvier (1981, 1997), Shu et al. (2003), and Benton (2004) is given here († = extinct ): While this traditional classification is orderly, most of the groups are paraphyletic , i.e. do not contain all descendants of

1140-399: The blue whale , at up to 33 m (108 ft). With only one exception, the defining characteristic of all vertebrates is the vertebral column , in which the embryonic notochord found in all chordates is replaced by a segmented series of mineralized elements called vertebrae separated by fibrocartilaginous intervertebral discs , which are embryonic and evolutionary remnants of

1197-541: The common nighthawk , barn owl , owlet-nightjar , chimney swift , American woodcock , spotted crake , white-breasted waterhen , European nightjars , and common buzzards . Many moths , beetles , flies , and other insects are crepuscular and vespertine. For example, Coprophanaeus ensifer , a South American necrophagous beetle, is most active during at dusk and dawn. Vertebrate Ossea Batsch, 1788 Vertebrates ( / ˈ v ɜːr t ə b r ɪ t s , - ˌ b r eɪ t s / ) are animals with

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1254-420: The copulation tie lasts up to two hours and 45 minutes. Gestation usually lasts between 50 and 52 days, though sometimes up to 63 days. After mating, the male becomes very aggressive and protects the female, and provides her with food during pregnancy and lactation . Females give birth between March and June to a litter of one to four pups that open their eyes after 8 to 11 days. Both female and male care for

1311-499: The desert environment with high temperatures and little water. It mainly eats insects , small mammals and birds . The fennec has a life span of up to 14 years in captivity and about 10 years in the wild. Its main predators are the Verreaux's eagle-owl , jackals and other large mammals. Fennec families dig out burrows in the sand for habitation and protection, which can be as large as 120 m (1,300 sq ft) and adjoin

1368-565: The genetics of organisms. Phylogenetic classification is based solely on phylogeny . Evolutionary systematics gives an overview; phylogenetic systematics gives detail. The two systems are thus complementary rather than opposed. Conventional classification has extant vertebrates grouped into seven classes based on traditional interpretations of gross anatomical and physiological traits. The commonly held classification lists three classes of fish and four of tetrapods . In addition to these, there are two classes of extinct armoured fishes,

1425-401: The lunar cycle due to the change in nocturnal light. This creates changes in animal sleep , reproduction , and foraging behaviours, often becoming less active during periods of low light. Animal patterns of activity sometimes change during migration due to changes in environmental conditions. Mule deer are crepuscular, but they are only active at dusk before and during migration. In

1482-410: The prosencephalon ( forebrain ), mesencephalon ( midbrain ) and rhombencephalon ( hindbrain ), which are further differentiated in the various vertebrate groups. Two laterally placed retinas and optical nerves form around outgrowths from the midbrain, except in hagfish which may have secondarily lost the structures. The forebrain is more well-developed in most tetrapods and subdivided into

1539-614: The spring they are only active at dawn because the snow is at its hardest , so it is easier for the deer to move without sinking in the snow. During migration, some types of swallow are active primarily during daytime hours with some activity during twilight hours. Crepuscular animal activity is affected by human activity , because humans are diurnal. Crepuscular animals are less likely to participate in typical foraging or reproductive behaviors and deal with increased stress and mortality rates when humans are present. Animals may change their usual activity patterns in response to

1596-432: The telencephalon and diencephalon , while the midbrain dominates in fish and some salamanders . In vertebrates with paired appendages, especially tetrapods, a pair of secondary enlargements of the hindbrain become the cerebella , which modulate complex motor coordinations . The brain vesicles are usually bilaterally symmetrical , giving rise to the paired cerebral hemispheres in mammals . The resultant anatomy of

1653-723: The United States to avoid any problems associated with inbreeding. The fennec fox is the national animal of Algeria . It also serves as the nickname for the Algeria national football team "Les Fennecs". Crepuscular animal A number of factors affect the time of day an animal is active. Predators hunt when their prey is available, and prey try to avoid the times when their principal predators are at large. The temperature may be too high at midday or too low at night. Some creatures may adjust their activities depending on local competition. The word crepuscular derives from

1710-418: The axial endoskeleton (enclosed by protective skeletal extensions known as neural arches ), with a fore-end enlargement that is contained within a distinct skeletonized braincase (hence the alternative name for vertebrates, the craniates ). All vertebrate embryos develop transient pharyngeal arches , which in fish develop into the branchial arches that support the gills . Other vertebrate features are

1767-427: The brain (which itself is a fused cluster of segmental ganglia from the rostral metameres ). Molecular markers known as conserved signature indels (CSIs) in protein sequences have been identified and provide distinguishing criteria for the vertebrate subphylum. Specifically, 5 CSIs in the following proteins: protein synthesis elongation factor-2 , eukaryotic translation initiation factor 3 , adenosine kinase and

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1824-410: The burrows of other families. Precise population figures are not known but are estimated from the frequency of sightings; these indicate that the fennec is currently not threatened by extinction. Knowledge of social interactions is limited to information gathered from captive animals. The fennec's fur is prized by the indigenous peoples of North Africa, and it is considered an exotic pet in some parts of

1881-642: The causes. African horned owl species such as the Pharaoh eagle-owl prey on fennec fox pups. Anecdotal reports exist about caracals , jackals , and striped hyenas also preying on the fennec fox. But according to nomads, the fennec fox is fast and changes directions so well that even their Salukis are hardly ever able to capture it. In North Africa, the fennec fox is commonly trapped for exhibition or sale to tourists. Expansion of permanent human settlements in southern Morocco caused its disappearance in these areas and restricted it to marginal areas. As of 2015,

1938-409: The class's common ancestor. For instance, descendants of the first reptiles include modern reptiles, mammals and birds; the agnathans have given rise to the jawed vertebrates ; the bony fishes have given rise to the land vertebrates ; the traditional " amphibians " have given rise to the reptiles (traditionally including the synapsids or mammal-like "reptiles"), which in turn have given rise to

1995-479: The crepuscular populations, and offer better foraging opportunities to predators that increasingly focus their attention on crepuscular prey until a new balance is struck. Such shifting states of balance are often found in ecology. Some predatory species adjust their habits in response to competition from other predators. For example, the subspecies of short-eared owl that lives on the Galápagos Islands

2052-449: The dawn, and vespertine, only in the dusk. Those active during both times are said to have a bimodal activity pattern. The various patterns of activity are thought to be mainly antipredator adaptations , though some could equally well be predatory adaptations . Many predators forage most intensively at night, whereas others are active at midday and see best in full sun. The crepuscular habit may both reduce predation pressure, increasing

2109-556: The demise of virtually all jawless fishes save for lampreys and hagfishes, as well as the Placodermi , a group of armoured fish that dominated the entirety of that period since the late Silurian as well as the eurypterids , dominant animals of the preceding Silurian , and the anomalocarids . By the middle of the Devonian, several droughts, anoxic events and oceanic competition led a lineage of sarcopterygii to leave water, eventually establishing themselves as terrestrial tetrapods in

2166-408: The dorsal nerve cord and migrate together with the mesodermal somites to innervate the various different structures that develop in the body. The vertebrates are the only chordate group with neural cephalization , and their neural functions are centralized towards a series of enlarged clusters in the head , which give rise to a brain . A slight swelling of the anterior end of the nerve cord

2223-477: The ears are whitish, but darker on the back. The ear to body ratio is the greatest in the canid family and likely helps in dissipating heat and locating vertebrates . It has dark streaks running from the inner eye to either side of the slender muzzle. Its large eyes are dark. The dental formula is 3.1.4.2 3.1.4.3  × 2 = 42 with small and narrow canines . The pads of its paws are covered with dense fur, which facilitates walking on hot, sandy soil. The fennec fox

2280-564: The endangered Amazon river dolphin , some species of bats , hamsters , housecats , stray dogs , rabbits , ferrets , rats , jaguars , ocelots , bobcats , servals , strepsirrhines , red pandas , bears , deer , moose , sitatunga , capybaras , chinchillas , the common mouse , skunks , squirrels , foxes , wombats , wallabies , quolls , possums and marsupial gliders , tenrecs , and spotted hyenas . Snakes , lizards , and frogs , especially those in desert environments, may be crepuscular. Crepuscular birds include

2337-629: The fennec fox is classified as Least concern on the IUCN Red List . It is listed in CITES Appendix II and is protected in Morocco and Western Sahara, Algeria, Tunisia and Egypt, where it has been documented in several protected areas. The fennec fox is bred commercially as an exotic pet . Commercial breeders remove the pups from their mother to hand-raise them, as tame foxes are more valuable. A breeders' registry has been set up in

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2394-483: The first gill arch pair evolved into the jointed jaws and form an additional oral cavity ahead of the pharynx . Research also suggests that the sixth branchial arch contributed to the formation of the vertebrate shoulder, which separated the head as a distinct part of the body. In amphibians and some primitive bony fishes, the larvae bear external gills , branching off from the gill arches. These are reduced in adulthood, their respiratory function taken over by

2451-421: The gill arches form during fetal development , and form the basis of essential structures such as jaws , the thyroid gland , the larynx , the columella (corresponding to the stapes in mammals ) and, in mammals, the malleus and incus . The central nervous system of vertebrates is based on the embryonic dorsal nerve cord (which then flattens into a neural plate before folding and fusing over into

2508-400: The gut tube, with a split brain stem circumventing the foregut around each side to form a brain on the dorsal side of the mouth . The higher functions of the vertebrate CNS are highly centralized towards the brain (particularly the forebrain), while the invertebrate CNS is significantly more decentralized with the segmental ganglia having substantial neural autonomy independent of

2565-443: The internal gills proper in fishes and by cutaneous respiration in most amphibians. While some amphibians such as axolotl retain the external gills into adulthood, the complex internal gill system as seen in fish apparently being irrevocably lost very early in the evolution of tetrapods , who evolved lungs (which are homologous to swim bladders ) to breathe air. While the more specialized terrestrial vertebrates lack gills,

2622-407: The jawless Agnatha , and the jawed Gnathostomata . The jawed fish include both the cartilaginous fish and the bony fish . Bony fish include the lobe-finned fish , which gave rise to the tetrapods , the animals with four limbs. Vertebrates make up less than five percent of all described animal species ; the rest are all invertebrates , that lack a backbone. The word 'vertebrate' derives from

2679-432: The length of an animal, hence the common name of backbone. The axial endoskeleton typically continues beyond the anus / cloaca to form an elongated tail . Some vertebrates evolved to become tailless with only a vestigial coccyx . A dorsal nerve cord , which folds and fuses into a hollow neural tube during embryonic development and eventually gives rise to the brain and spinal cord , runs more dorsally to

2736-460: The mammals and birds. Most scientists working with vertebrates use a classification based purely on phylogeny , organized by their known evolutionary history and sometimes disregarding the conventional interpretations of their anatomy and physiology. In phylogenetics , the relationships between animals are illustrated as a hierarchy known as a phylogenetic tree . The cladogram below is based on studies compiled by Philippe Janvier and others for

2793-411: The notochord. Hagfish are the only extant vertebrate whose notochord persists and is not integrated/ replaced by the vertebral column. A few vertebrates have secondarily lost this feature and retain the notochord into adulthood, such as the sturgeon . Most vertebrates are aquatic and carry out gas exchange via gills . The gills are carried right behind the head, bordering the posterior margins of

2850-414: The presence of humans. For example, Asian black bears may avoid areas with high human activity during the day, but go to these locations during twilight or nighttime hours. Light pollution impacts crepuscular behaviour because it mimics natural light conditions, leading crepuscular animals to behave as they would on nights with more moonlight. Many familiar mammal species are crepuscular, including

2907-649: The pups. They communicate by barking, purring, yapping and squeaking. Pups remain in the family even after a new litter is born. The pups are weaned at the age of 61 to 70 days. Adults rear pups until they are around 16 to 17 weeks old. The oldest captive male fennec fox was 14 years old, and the oldest female 13 years. Captive fennec foxes are susceptible to canine distemper virus , displaying fever, mucopurulent ocular discharge, diarrhea , severe emaciation , seizures, generalized ataxia , severe dehydration , brain congestion, gastric ulcers and death. Stress because of capture and long-distance transportation are thought to be

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2964-609: The relationships between the Olfactores (vertebrates and tunicates) and the Cephalochordata.   Amphioxiformes (lancelets)  [REDACTED]   Tunicata /Urochordata ( sea squirts , salps , larvaceans )  [REDACTED]   Vertebrata   [REDACTED] Vertebrates originated during the Cambrian explosion , which saw a rise in organism diversity. The earliest known vertebrates belongs to

3021-677: The sand for small vertebrates and insects . Some individuals were observed to bury prey for later consumption and searching for food in the vicinity of human settlements. In the Algerian Sahara, 114 scat samples were collected that contained more than 400 insects, plant fragments and date palm ( Phoenix dactylifera ) fruits, remains of birds, mammals, squamata and insects. Fennec foxes mate for life. Captive fennec foxes reach sexual maturity at around nine months and mate between January and April. Female fennec foxes are in estrus for an average of 24 hours and usually breed once per year;

3078-661: The seabed. A vertebrate group of uncertain phylogeny, small eel-like conodonts , are known from microfossils of their paired tooth segments from the late Cambrian to the end of the Triassic. The first jawed vertebrates may have appeared in the late Ordovician (~445 mya) and became common in the Devonian period , often known as the "Age of Fishes". The two groups of bony fishes , the Actinopterygii and Sarcopterygii , evolved and became common. The Devonian also saw

3135-650: The succeeding Carboniferous . Amniotes branched from amphibious tetrapods early in the Carboniferous period. The synapsid amniotes were dominant during the late Paleozoic, the Permian , while diapsid amniotes became dominant during the Mesozoic . In the sea, the teleosts and sharks became dominant. Mesothermic synapsids called cynodonts gave rise to endothermic mammals and diapsids called dinosaurs eventually gave rise to endothermic birds , both in

3192-402: The two classes). Tetrapods comprise the dominant megafauna of most terrestrial environments and also include many partially or fully aquatic groups (e.g., sea snakes , penguins , cetaceans). There are several ways of classifying animals. Evolutionary systematics relies on anatomy , physiology and evolutionary history, which is determined through similarities in anatomy and, if possible,

3249-405: The world. Its name comes from the species' Arabic name: fanak ( فَنَك ). The fennec fox has sand-colored fur which reflects sunlight during the day and helps keep it warm at night. Its nose is black and its tapering tail has a black tip. Its long ears have longitudinal reddish stripes on the back and are so densely haired inside that the external auditory meatus is not visible. The edges of

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