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33-484: 1st row: Dvinia prima , Trirachodon berryi ; 2nd row: Brasilitherium riograndensis , Megazostrodon rudnerae ; 3rd row: Ornithorhynchus anatinus ( platypus ), Loxodonta africana ( African bush elephant ). Cynodontia ( lit.   ' dog-teeth ' ) is a clade of eutheriodont therapsids that first appeared in the Late Permian (approximately 260 mya ), and extensively diversified after

66-664: A family. Robert Broom (1913) reranked Cynodontia as an infraorder, since retained by others, including Colbert and Kitching (1977), Carroll (1988), Gauthier et al. (1989), and Rubidge and Cristian Sidor (2001). Olson (1966) assigned Cynodontia to Theriodontia , Colbert and Kitching (1977) to Theriodontia, and Rubridge and Sidor (2001) to Eutheriodontia . William King Gregory (1910), Broom (1913), Carroll (1988), Gauthier et al. (1989), Hopson and Kitching (2001) and Botha et al. (2007) all considered Cynodontia as belonging to Therapsida. Botha et al. (2007) seems to have followed Owen (1861), but without specifying taxonomic rank. Below

99-448: A fundamentally marsupial-like reproductive style, but produced much higher litters at around 38 perinates or possibly eggs. Cynodonts are the only known synapsid lineage to have produced aerial locomotors, with gliding being known in haramiyidans and various mammal groups, and placental mammals having developed flight. The largest known non-mammalian cynodont is Scalenodontoides , a traversodontid , which has been estimated to have

132-471: A length of time. Altricial birds include hawks , herons , woodpeckers , owls , cuckoos and most passerines . Among mammals, marsupials and most rodents are altricial. Domestic cats , dogs , and primates , such as humans , are some of the best-known altricial organisms. For example, newborn domestic cats cannot see, hear, maintain their own body temperature, or gag , and require external stimulation in order to defecate and urinate. The giant panda

165-548: A maximum skull length of approximately 617 millimetres (24.3 in) based on a fragmentary specimen. The closest relatives of cynodonts are therocephalians , with which they form the clade Eutheriodontia . The earliest cynodonts are known early Lopingian (early Wuchiapingian ) aged sediments of the Tropidostoma Assemblage Zone , in the Karoo Supergroup of South Africa, belonging to

198-451: A muscular, mobile face is necessary to perform whisking movements and to avoid damage to whiskers , it is unlikely that early cynodonts had whiskers. In prozostrodontian cynodonts, the group that includes mammals, the foramina are replaced by a single large infraorbital foramen, which indicates that the face had become muscular and that whiskers would have been present. Derived cynodonts developed epipubic bones. These served to strengthen

231-529: A way similar to that of megapodes, being able to fly soon after birth. It has been speculated that superprecociality prevented enantiornithines from acquiring specialized toe anatomy seen in modern altricial birds. In birds and mammals altricial species are those whose newly hatched or born young are relatively immobile, lack hair or down , are not able to obtain food on their own, and must be cared for by adults; closed eyes are common, though not ubiquitous. Altricial young are born helpless and require care for

264-399: A week old. Black mambas are highly precocial; as hatchlings, they are fully independent, and are capable of hunting prey the size of a small rat . Precociality is thought to be ancestral in birds. Thus, altricial birds tend to be found in the most derived groups. There is some evidence for precociality in protobirds and troodontids . Enantiornithes at least were superprecocial in

297-843: Is a cladogram from Ruta, Botha-Brink, Mitchell and Benton (2013) showing one hypothesis of cynodont relationships: † Charassognathus † Dvinia † Procynosuchus † Cynosaurus † Galesaurus † Progalesaurus † Nanictosaurus † Thrinaxodon † Platycraniellus † Cynognathus † Diademodon † Beishanodon † Sinognathus † Trirachodon † Cricodon † Langbergia † Andescynodon † Pascualgnathus † Scalenodon † Luangwa † Traversodon † "Scalenodon" attridgei † Mandagomphodon † Nanogomphodon † Arctotraversodon † Boreogomphodon † Massetognathus † Dadadon † Santacruzodon † Menadon † Gomphodontosuchus † Protuberum † Exaeretodon Dvinia prima Too Many Requests If you report this error to

330-451: Is derived from the Latin root praecox, the same root as in precocious , meaning early maturity. Extremely precocial species are called "superprecocial". Examples are the megapode birds, which have full-flight feathers at hatching and which, in some species, can fly on the same day. Enantiornithes and pterosaurs were also capable of flight soon after hatching. Another example is

363-559: Is hypothesized to occur so that exposure to predators during the nestling stage of development can be minimized. In the case of mammals, it has been suggested that large, hearty adult body sizes favor the production of large, precocious young, which develop with a longer gestation period. Large young may be associated with migratory behavior, extended reproductive period, and reduced litter size. It may be that altricial strategies in mammals, in contrast, develop in species with less migratory and more territorial lifestyles, such as Carnivorans ,

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396-411: Is notably the largest placental mammal to have altricial, hairless young upon birth. The larval stage of insect development is considered by some to be a form of altricial development, but it more accurately depicts, especially amongst eusocial animals, an independent phase of development, as the larvae of bees, ants, and many arachnids are completely physically different from their developed forms, and

429-461: Is only brief amongst primates; their offspring soon develop stronger bones, grow in spurts, and quickly mature in features. This unique growth pattern allows for the hasty adaptivity of most simians, as anything learned by children in between their infancy and adolescence is memorized as instinct; this pattern is also in contrast to more prominently altricial mammals, such as many rodents , which remain largely immobile and undeveloped until grown to near

462-529: The Permian–Triassic extinction event . Mammals are cynodonts, as are their extinct ancestors and close relatives ( Mammaliaformes ), having evolved from advanced probainognathian cynodonts during the Late Triassic. Non-mammalian cynodonts occupied a variety of ecological niches , both as carnivores and as herbivores. Following the emergence of mammals, most other cynodont lines went extinct, with

495-694: The blue wildebeest , the calves of which can stand within an average of six minutes from birth and walk within thirty minutes; they can outrun a hyena within a day. Such behavior gives them an advantage over other herbivore species and they are 100 times more abundant in the Serengeti ecosystem than hartebeests , their closest taxonomic relative. Hartebeest calves are not as precocial as wildebeest calves and take up to thirty minutes or more before they stand, and as long as forty-five minutes before they can follow their mothers for short distances. They are unable to keep up with their mothers until they are more than

528-530: The Carnian and in the middle Norian. Post-Early Triassic cynodonts were dominated by members of the advanced clade Eucynodontia , which has two main subdivisions, the predominantly herbivorous Cynognathia and the predominantly carnivorous Probainognathia . During the Early and Middle Triassic, cynodont diversity was dominated by members of Cynognathia, and members of Probainognathia would not become prominent until

561-667: The Jurassic, predominantly in the Northern Hemisphere, persisted into the Early Cretaceous ( Barremian - Aptian ) in Asia, at least until around 120 million years ago, as represented by Fossiomanus from China. During their evolution , the number of cynodont jaw bones reduced. This move towards a single bone for the mandible paved the way for other bones in the jaw, the articular and angular , to migrate to

594-494: The Late Triassic (early Norian ). Almost all Middle Triassic cynodonts are known from Gondwana, with only one genus ( Nanogomphodon ) having been found in the Northern Hemisphere. Among the most dominant groups of Middle and Late Triassic cynodonts is the herbivorous Traversodontidae , predominantly in Gondwana, which reached a peak diversity in the Late Triassic. Mammaliaformes originated from probainognathian cynodonts during

627-542: The Late Triassic. Early Mammaliaformes were small bodied insectivores. Only two groups of non-mammaliaform cynodonts existed beyond the end of the Triassic, both belonging to Probainognathia. The first is the insectivorous Tritheledontidae , which briefly lasted into the Early Jurassic. The second is the herbivorous Tritylodontidae , which first appeared in the latest Triassic, which were abundant and diverse during

660-520: The Wikimedia System Administrators, please include the details below. Request from 172.68.168.237 via cp1104 cp1104, Varnish XID 180024985 Upstream caches: cp1104 int Error: 429, Too Many Requests at Thu, 28 Nov 2024 07:48:50 GMT Altricial In fish , this often refers to the presence or absence of a stomach : precocial larvae have one at the onset of first feeding whereas altricial fish do not. Depending on

693-455: The basal family Charassognathidae . Fossils of Permian cynodonts are relatively rare outside of South Africa, with the most widely distributed genus being Procynosuchus , which is known from South Africa, Germany, Tanzania, Zambia, and possibly Russia. Cynodonts expanded rapidly in diversity after the Permian–Triassic extinction event . Peak disparity in cynodonts occurred from the Induan to

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726-453: The cranium, where they function as parts of the mammalian hearing system. Cynodonts also developed a secondary palate in the roof of the mouth. This caused air flow from the nostrils to travel to a position in the back of the mouth instead of directly through it, allowing cynodonts to chew and breathe at the same time. This characteristic is present in all mammals. Richard Owen named Cynodontia in 1861, which he assigned to Anomodontia as

759-637: The domestic chicken , many species of ducks and geese , waders , rails , and the hoatzin . Precocial birds can provide protein-rich eggs and thus their young hatch in the fledgling stage – able to protect themselves from predators and the females have less post-natal involvement. Altricial birds are less able to contribute nutrients in the pre-natal stage; their eggs are smaller and their young are still in need of much attention and protection from predators. This may be related to r/K selection ; however, this association fails in some cases. In birds, altricial young usually grow faster than precocial young. This

792-590: The last known non-mammaliaform cynodont group, the Tritylodontidae , having its youngest records in the Early Cretaceous . Early cynodonts have many of the skeletal characteristics of mammals . The teeth were fully differentiated and the braincase bulged at the back of the head. Outside of some crown-group mammals (notably the therians ), all cynodonts probably laid eggs. The temporal fenestrae were much larger than those of their ancestors, and

825-559: The mothers of which are capable of bearing a fetus in the early stages of development and focusing closely and personally upon its raising, as opposed to precocial animals which provide their youths with a bare minimum of aid and otherwise leave them to instinct. Human children, and those of other primates, exemplify a unique combination of altricial and precocial development. Infants are born with minimal eyesight, compact and fleshy bodies, and "fresh" features (thinner skin, small noses and ears, and scarce hair if any). However, this stage

858-403: The nest in a short period of time following hatching (e.g. 24 hours). Many precocial chicks are not independent in thermoregulation (the ability to regulate their body temperatures), and they depend on the attending parent(s) to brood them with body heat for a short time. Precocial birds find their own food, sometimes with help or instruction from their parents. Examples of precocial birds include

891-686: The pre-pupal stages of insect life might be regarded as equivalent to vertebrate embryonic development. The word “altriciality” is derived from the Latin root alere , meaning "to nurse, to rear, or to nourish", and indicates the need for young to be fed and taken care of for a long duration. The span between precocial and altricial species is particularly broad in the biology of birds . Precocial birds hatch with their eyes open and are covered with downy feathers that are soon replaced by adult-type feathers. Birds of this kind can also swim and run much sooner after hatching than altricial young, such as songbirds. Very precocial birds can be ready to leave

924-530: The species, the larvae may develop a functional stomach during metamorphosis (gastric) or remain stomachless (agastric). Precocial young have open eyes, hair or down, large brains, and are immediately mobile and somewhat able to flee from or defend themselves against predators. For example, with ground-nesting birds such as ducks or turkeys , the young are ready to leave the nest in one or two days. Among mammals, most ungulates are precocial, being able to walk almost immediately after birth. The word "precocial"

957-450: The stature of their parents. In birds, the terms Aves altrices and Aves precoces were introduced by Carl Jakob Sundevall (1836), and the terms nidifugous and nidicolous by Lorenz Oken in 1816. The two classifications were considered identical in early times, but the meanings are slightly different, in that "altricial" and "precocial" refer to developmental stages, while "nidifugous" and "nidicolous" refer to leaving or staying at

990-591: The telltale imprint of this structure is only found from the primitive mammal Morganucodon and onwards. Nonetheless, recent studies on Permian synapsid coprolites show that more basal therapsids may have had fur, and at any rate fur was already present in Mammaliaformes such as Castorocauda and Megaconus . Early cynodonts had numerous small foramina on their snout bones, similar to reptiles. This suggests that they had immobile, non-muscular lips like those of lizards, and lacked muscular cheeks. As

1023-475: The therocephalians primarily comprises the maxillae and the vomer .) The dentary was the largest bone in their lower jaw. The cynodonts probably had some form of warm-blooded metabolism. This has led to many reconstructions of cynodonts as having fur . Being endothermic they may have needed it for thermoregulation , but fossil evidence of their fur (or lack thereof) has been elusive. Modern mammals have Harderian glands secreting lipids to coat their fur, but

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1056-446: The torso and support abdominal and hindlimb musculature, aiding them in the development of an erect gait, but at the expense of prolonged pregnancy, forcing these animals to give birth to highly altricial young as in modern marsupials and monotremes . Only placentals , and perhaps Megazostrodon and Erythrotherium , would lose these. A specimen of Kayentatherium does indeed demonstrate that at least tritylodontids already had

1089-413: The widening of the zygomatic arch in a more mammal-like skull would have allowed for more robust jaw musculature. They also have the secondary palate that other primitive therapsids lacked, except the therocephalians , who were the closest relatives of cynodonts. (However, the secondary palate of cynodonts primarily comprises the maxillae and palatines as in mammals, whereas the secondary palate of

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