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72-530: [REDACTED] Look up whelp in Wiktionary, the free dictionary. Whelp may refer to: Whelping , the birthing of carnivorous mammals any young, carnivorous mammal; most commonly a puppy Whelp (tidal bore) in an undular bore: the train of secondary waves behind the bore front HMS Whelp : the name of one ship of the Royal Navy and of another which

144-526: A 20-hour old baby whose parents chose UCNS was brought to the hospital in an agonal state, was diagnosed with sepsis and required an antibiotic treatment for 6 weeks. As the umbilical vein is directly connected to the central circulation, it can be used as a route for placement of a venous catheter for infusion and medication. The umbilical vein catheter is a reliable alternative to percutaneous peripheral or central venous catheters or intraosseous canulas and may be employed in resuscitation or intensive care of

216-403: A balanced perspective on their options for cord blood banking. In response to their constituents, state legislators across the country are introducing legislation intended to help inform physicians and expectant parents on the options for donating, discarding or banking lifesaving newborn stem cells. Currently 17 states, representing two-thirds of U.S. births, have enacted legislation recommended by

288-452: A better harvesting, and multiplication, and immunosuppressive properties that define their potential for use in transplantations. Their use would also overcome the ethical objections raised by the use of embryonic stem cells . The umbilical cord contains Wharton's jelly , a gelatinous substance made largely from mucopolysaccharides that protects the blood vessels inside. It contains one vein, which carries oxygenated, nutrient-rich blood to

360-432: A closely matching tissue type and demonstrated need. The use of cord blood from public banks is increasing. Currently it is used in place of a bone marrow transplant in the treatment of blood disorders such as leukemia, with donations released for transplant through one registry, Netcord.org, passing 1,000,000 as of January 2013. Cord blood is used when the patient cannot find a matching bone marrow donor; this "extension" of

432-432: A glistening grey balloon, with a puppy inside, is propelled through the vulva . After further contractions, the sac is expelled and the bitch breaks the membranes, releasing clear fluid and exposing the puppy. The mother chews at the umbilical cord and licks the puppy vigorously, which stimulates it to breathe. If the puppy has not taken its first breath within about six minutes, it is likely to die. Further puppies follow in

504-457: A higher rate of neonatal jaundice requiring phototherapy . Delayed clamping is not recommended as a response to cases where the newborn is not breathing well and needs resuscitation. Rather, the recommendation is instead to immediately clamp and cut the cord and perform cardiopulmonary resuscitation . The umbilical cord pulsating is not a guarantee that the baby is receiving enough oxygen. Some parents choose to omit cord severance entirely,

576-432: A multiple birth) signifies the end of stage two. The cow scrambles to her feet (if lying down at this stage), turns round and starts vigorously licking the calf. The calf takes its first few breaths and within minutes is struggling to rise to its feet. The third and final stage of labor is the delivery of the placenta , which is usually expelled within a few hours and is often eaten by the normally herbivorous cow. Birth

648-453: A plastic tissue which can easily be shifted in an axial direction and then folded into the narrowing lumen to complete the closure. The vasoconstrictive occlusion appears to be mainly mediated by serotonin and thromboxane A 2 . The artery in cords of preterm infants contracts more to angiotensin II and arachidonic acid and is more sensitive to oxytocin than in term ones. In contrast to

720-436: A practice called " lotus birth " or umbilical nonseverance. The entire intact umbilical cord is allowed to dry and separates on its own (typically on the 3rd day after birth), falling off and leaving a healed umbilicus. The Royal College of Obstetricians and Gynaecologists has warned about the risks of infection as the decomposing placenta tissue becomes a nest for infectious bacteria such as Staphylococcus . In one such case

792-465: A similar way one by one usually with less straining than the first usually at 15-60-minute intervals. If a pup has not been passed in 2 hours a veterinarian should be contacted. Stage three is the passing of the placentas. This often occurs in conjunction with stage two with the passing of each offspring. The mother will then usually eat the afterbirth. This is an adaption to keep the den clean and prevent its detection by predators. An infant marsupial

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864-448: A swelling and collapse of Wharton's jelly in response to a reduction in temperature and by vasoconstriction of the blood vessels by smooth muscle contraction. In effect, a natural clamp is created, halting the flow of blood. In air at 18 °C, this physiological clamping will take three minutes or less. In water birth , where the water temperature is close to body temperature, normal pulsation can be 5 minutes and longer. Closure of

936-406: A time, although they may have twin or multiple births on occasion. In these large animals, the birth process is similar to that of a human, though in most the offspring is precocial . This means that it is born in a more advanced state than a human baby and is able to stand, walk and run (or swim in the case of an aquatic mammal) shortly after birth. In the case of whales, dolphins and porpoises,

1008-544: A very few give birth to offspring that are miniature versions of the adult. The aphid has a complex life cycle and during the summer months is able to multiply with great rapidity. Its reproduction is typically parthenogenetic and viviparous and females produce unfertilized eggs which they retain within their bodies. The embryos develop within their mothers' ovarioles and the offspring are clones of their mothers. Female nymphs are born which grow rapidly and soon produce more female offspring themselves. In some instances,

1080-411: Is a hole in the septum dividing the right atrium and left atrium . After birth the umbilical cord is clamped and cut, the baby starts to breathe air, and blood from the right ventricle starts to flow to the lungs for gaseous exchange and oxygenated blood returns to the left atrium , which is pumped into the left ventricle , and then pumped into the main arterial system. As a result of these changes,

1152-453: Is born in a very immature state. The gestation period is usually shorter than the intervals between oestrus periods. The first sign that a birth is imminent is the mother cleaning out her pouch . When it is born, the infant is pink, blind, furless and a few centimetres long. It has nostrils in order to breathe and forelegs to cling onto its mother's hairs but its hind legs are undeveloped. It crawls through its mother's fur and makes its way into

1224-433: Is different from Wikidata All article disambiguation pages All disambiguation pages Whelping In some species, the offspring is precocial and can move around almost immediately after birth but in others, it is altricial and completely dependent on parenting. In marsupials , the fetus is born at a very immature stage after a short gestation and develops further in its mother's womb pouch . It

1296-408: Is external protrusion of the amniotic sac through the vulva, closely followed by the appearance of the calf's front hooves and head in a front presentation (or occasionally the calf's tail and rear end in a posterior presentation). During the second stage, the cow will usually lie down on her side to push and the calf progresses through the birth canal. The complete delivery of the calf (or calves in

1368-489: Is not directly connected to the mother's circulatory system, but instead joins the placenta , which transfers materials to and from the maternal blood without allowing direct mixing. The length of the umbilical cord is approximately equal to the crown-rump length of the fetus throughout pregnancy . The umbilical cord in a full term neonate is usually about 50 centimeters (20 in ) long and about 2 centimeters (0.75 in) in diameter. This diameter decreases rapidly within

1440-442: Is not only mammals that give birth. Some reptiles, amphibians, fish and invertebrates carry their developing young inside them. Some of these are ovoviviparous , with the eggs being hatched inside the mother's body, and others are viviparous , with the embryo developing inside their body, as in the case of mammals. Humans usually produce a single offspring at a time. The mother's body is prepared for birth by hormones produced by

1512-416: Is termed whelping in dogs. Among dogs , as whelping approaches, contractions become more frequent. Labour in the bitch can be divided into 3 stages. The first stage is when the cervix dilates, causing discomfort and restlessness in the dog. Common signs of this stage are panting, fasting, and/or vomiting. This may last up to 12 hours. Stage two is the passage of the offspring. The amniotic sac looking like

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1584-413: The pituitary gland , the ovary and the placenta . The total gestation period from fertilization to birth is normally about 38 weeks (birth usually occurring 40 weeks after the last menstrual period ). The normal process of childbirth takes several hours and has three stages. The first stage starts with a series of involuntary contractions of the muscular walls of the uterus and gradual dilation of

1656-417: The placenta , amniotic sac, and the remaining portion of the umbilical cord usually within a few minutes. Enormous changes take place in the newborn's circulation to enable breathing in air. In the uterus, the fetus is dependent on circulation of blood through the placenta for sustenance including gaseous exchange and the unborn baby's blood bypasses the lungs by flowing through the foramen ovale , which

1728-433: The proximal part of an umbilical cord refers to the segment closest to the embryo or fetus in embryology and fetal medicine, and closest to the placenta in placental pathology, and opposite for the distal part, respectively. The umbilical cord enters the fetus via the abdomen , at the point which (after separation) will become the umbilicus (belly button or navel). Within the fetus, the umbilical vein continues towards

1800-514: The pulmonary veins and arteries , connecting the lungs to the heart). However, this naming convention reflects the fact that the umbilical vein carries blood towards the fetus' heart, while the umbilical arteries carry blood away. The blood flow through the umbilical cord is approximately 35 ml / min at 20 weeks, and 240 ml / min at 40 weeks of gestation . Adapted to the weight of the fetus, this corresponds to 115 ml / min / kg at 20 weeks and 64 ml / min / kg at 40 weeks. For terms of location ,

1872-442: The transverse fissure of the liver , where it splits into two. One of these branches joins with the hepatic portal vein (connecting to its left branch), which carries blood into the liver. The second branch (known as the ductus venosus ) bypasses the liver and flows into the inferior vena cava , which carries blood towards the heart. The two umbilical arteries branch from the internal iliac arteries and pass on either side of

1944-475: The urinary bladder into the umbilical cord, completing the circuit back to the placenta. After birth, the umbilical cord stump will dry up and drop away by the time the baby is three weeks old. If the stump still has not separated after three weeks, it might be a sign of an underlying problem, such as an infection or immune system disorder. In absence of external interventions, the umbilical cord occludes physiologically shortly after birth, explained both by

2016-429: The uterus are not obvious externally, but the cow may be restless. She may appear agitated, alternating between standing and lying down, with her tail slightly raised and her back arched. The fetus is pushed toward the birth canal by each contraction and the cow's cervix gradually begins to dilate. Stage one may last several hours, and ends when the cervix is fully dilated. Stage two can be seen to be underway when there

2088-467: The IoM guidelines. The use of cord blood stem cells in treating conditions such as brain injury and Type 1 Diabetes is already being studied in humans, and earlier stage research is being conducted for treatments of stroke, and hearing loss. Cord blood stored with private banks is typically reserved for use of the donor child only. In contrast, cord blood stored in public banks is accessible to anyone with

2160-537: The Tarangire National Park of Tanzania, estimated to have been born in August 2017. Birthing in cattle is typical of a larger mammal. A cow goes through three stages of labor during normal delivery of a calf. During stage one, the animal seeks a quiet place away from the rest of the herd. Hormone changes cause soft tissues of the birth canal to relax as the mother's body prepares for birth. The contractions of

2232-435: The baby's umbilical blood transfer through early cord clamping and cutting, to freeze for long-term storage at a cord blood bank should the child ever require the cord blood stem cells (for example, to replace bone marrow destroyed when treating leukemia ). This practice is controversial, with critics asserting that early cord blood withdrawal at the time of birth actually increases the likelihood of childhood disease, due to

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2304-572: The blood of umbilical cords. These originate from certain plastics, computer circuit boards, fumes and synthetic fragrances among others. Over 300 chemical toxicants have been found, including bisphenol A (BPA), tetrabromobisphenol A (TBBPA), Teflon -related perfluorooctanoic acid , galaxolide and synthetic musks among others. The studies in America showed higher levels in African Americans , Hispanic Americans and Asian Americans due, it

2376-605: The blood pressure in the left atrium exceeds the pressure in the right atrium, and this pressure difference forces the foramen ovale to close separating the left and right sides of the heart. The umbilical vein , umbilical arteries , ductus venosus and ductus arteriosus are not needed for life in air and in time these vessels become ligaments (embryonic remnants). Large mammals , such as primates , cattle , horses , some antelopes , giraffes , hippopotamuses , rhinoceroses , elephants , seals , whales , dolphins , and porpoises , generally are pregnant with one offspring at

2448-586: The case of existing medical need, it also says that information about the potential benefits and limitations of cord blood banking and transplantation should be provided so that parents can make an informed decision. In the United States, cord blood education has been supported by legislators at the federal and state levels. In 2005, the National Academy of Sciences published an Institute of Medicine (IoM) report which recommended that expectant parents be given

2520-466: The cervix. The active phase of the first stage starts when the cervix is dilated more than about 4 cm in diameter and is when the contractions become stronger and regular. The head (or the buttocks in a breech birth ) of the baby is pushed against the cervix , which gradually dilates until it is fully dilated at 10 cm diameter. At some time, the amniotic sac bursts and the amniotic fluid escapes (also known as rupture of membranes or breaking

2592-421: The circulatory system. A number of abnormalities can affect the umbilical cord, which can cause problems that affect both mother and child: The cord can be clamped at different times; however, delaying the clamping of the umbilical cord until at least one minute after birth improves outcomes as long as there is the ability to treat the small risk of jaundice if it occurs. Clamping is followed by cutting of

2664-556: The conclusion that delayed cord clamping (between one and three minutes after birth) is "likely to be beneficial as long as access to treatment for jaundice requiring phototherapy is available". In this review delayed clamping, as contrasted to early, resulted in no difference in risk of severe maternal postpartum hemorrhage or neonatal mortality, and a low Apgar score . On the other hand, delayed clamping resulted in an increased birth weight of on average about 100 g, and an increased hemoglobin concentration of on average 1.5 g/dL with half

2736-441: The contribution of Wharton's jelly, cooling causes only temporary vasoconstriction. Within the child, the umbilical vein and ductus venosus close up, and degenerate into fibrous remnants known as the round ligament of the liver and the ligamentum venosum respectively. Part of each umbilical artery closes up (degenerating into what are known as the medial umbilical ligaments ), while the remaining sections are retained as part of

2808-435: The cord for three minutes following the birth of a baby improved outcomes at four years of age. A delay of three minutes or more in umbilical cord clamping after birth reduce the prevalence of anemia in infants. Negative effects of delayed cord clamping include an increased risk of polycythemia . Still, this condition appeared to be benign in studies. Infants whose cord clamping occurred later than 60 seconds after birth had

2880-536: The cord, according to the American Congress of Obstetricians and Gynecologists (ACOG) guidelines. There are umbilical cord clamps which incorporate a knife. These clamps are safer and faster, allowing one to first apply the cord clamp and then cut the umbilical cord. After the cord is clamped and cut, the newborn wears a plastic clip on the navel area until the compressed region of the cord has dried and sealed sufficiently. The length of umbilical left attached to

2952-441: The cord, which is painless due to the absence of nerves . The cord is extremely tough, like thick sinew , and so cutting it requires a suitably sharp instrument. While umbilical severance may be delayed until after the cord has stopped pulsing (1–3 minutes after birth), there is ordinarily no significant loss of either venous or arterial blood while cutting the cord. Current evidence neither supports, nor refutes, delayed cutting of

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3024-517: The donor pool has driven the expansion of public banks. The umbilical cord in some mammals, including cattle and sheep, contains two distinct umbilical veins. There is only one umbilical vein in the human umbilical cord. In some animals, the mother will gnaw through the cord, thus separating the placenta from the offspring. The cord along with the placenta is often eaten by the mother, to provide nourishment and to dispose of tissues that would otherwise attract scavengers or predators. In chimpanzees ,

3096-437: The expectation that a small number may survive to become mature individuals. Terrestrial invertebrates may also produce large numbers of eggs, a few of which may avoid predation and carry on the species. Some fish, reptiles, and amphibians have adopted a different strategy and invest their effort in producing a small number of young at a more advanced stage which are more likely to survive to adulthood. Birds care for their young in

3168-410: The fetus with oxygenated , nutrient -rich blood from the placenta . Conversely, the fetal heart pumps low-oxygen, nutrient-depleted blood through the umbilical arteries back to the placenta. The umbilical cord develops from and contains remnants of the yolk sac and allantois . It forms by the fifth week of development , replacing the yolk sac as the source of nutrients for the embryo. The cord

3240-408: The fetus, and two arteries that carry deoxygenated, nutrient-depleted blood away. Occasionally, only two vessels (one vein and one artery) are present in the umbilical cord. This is sometimes related to fetal abnormalities, but it may also occur without accompanying problems. It is unusual for a vein to carry oxygenated blood and for arteries to carry deoxygenated blood (the only other examples being

3312-520: The genera Tiliqua and Corucia , give birth to live young that develop internally, deriving their nourishment from a mammal-like placenta attached to the inside of the mother's uterus. In a recently described example, an African species, Trachylepis ivensi , has developed a purely reptilian placenta directly comparable in structure and function to a mammalian placenta. Vivipary is rare in snakes , but boas and vipers are viviparous, giving birth to live young. The majority of insects lay eggs but

3384-463: The genus Nectophrynoides are ovoviviparous, developing through the larval stage inside the mother's oviduct and eventually emerging as fully formed juveniles. A more developed form of viviparity called placental viviparity is adopted by some species of scorpions and cockroaches, certain genera of sharks , snakes and velvet worms . In these, the developing embryo is nourished by some form of placental structure. The earliest known placenta

3456-466: The high volume of blood taken (an average of 108ml) in relation to the baby's total supply (typically 300ml). The Royal College of Obstetricians and Gynaecologists stated in 2006 that "there is still insufficient evidence to recommend directed commercial cord blood collection and stem-cell storage in low-risk families". The American Academy of Pediatrics has stated that cord blood banking for self-use should be discouraged (as most conditions requiring

3528-479: The hose connecting surface-supplied divers to their surface supply of air and/or heating, or space-suited astronauts to their spacecraft. Engineers sometimes use the term to describe a complex or critical cable connecting a component, especially when composed of bundles of conductors of different colors, thickness and types, terminating in a single multi-contact disconnect. In multiple American and international studies, cancer-causing chemicals have been found in

3600-533: The mother leaves the cord in place and nurses her young with the cord and placenta attached until the cord dries out and separates naturally, within a day of birth, at which time the cord is discarded. (This was first documented by zoologists in the wild in 1974. ) Some species of shark — hammerheads , requiems and smooth-hounds —are viviparous and have an umbilical cord attached to their placenta. The term "umbilical cord" or just "umbilical" has also come to be used for other cords with similar functions, such as

3672-412: The nest and provide for their needs after hatching and it is perhaps unsurprising that internal development does not occur in birds, given their need to fly. Ovoviviparity is a mode of reproduction in which embryos develop inside eggs that remain in the mother's body until they are ready to hatch. Ovoviviparous animals are similar to viviparous species in that there is internal fertilization and

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3744-618: The newborn nymphs already have developing embryos inside them. Umbilical cord In placental mammals , the umbilical cord (also called the navel string , birth cord or funiculus umbilicalis ) is a conduit between the developing embryo or fetus and the placenta . During prenatal development , the umbilical cord is physiologically and genetically part of the fetus and (in humans) normally contains two arteries (the umbilical arteries ) and one vein (the umbilical vein ), buried within Wharton's jelly . The umbilical vein supplies

3816-535: The newborn period and improved iron stores in the first months of life, which may result in improved developmental outcomes. ACOG recognized a small increase in the incidence of jaundice in term infants with delayed cord clamping, and recommended policies be in place to monitor for and treat neonatal jaundice. ACOG also noted that delayed cord clamping is not associated with increased risk of postpartum hemorrhage. Several studies have shown benefits of delayed cord clamping: A meta-analysis showed that delaying clamping of

3888-497: The newborn varies by practice; in most hospital settings the length of cord left attached after clamping and cutting is minimal. In the United States, however, where the birth occurred outside of the hospital and an emergency medical technician (EMT) clamps and cuts the cord, a longer segment up to 18 cm (7 in) in length is left attached to the newborn. The remaining umbilical stub remains for up to 10 days as it dries and then falls off. A Cochrane review in 2013 came to

3960-610: The newborn. From 24 to 34 weeks of gestation, when the fetus is typically viable, blood can be taken from the cord in order to test for abnormalities (particularly for hereditary conditions). This diagnostic genetic test procedure is known as percutaneous umbilical cord blood sampling . The blood within the umbilical cord, known as cord blood , is a rich and readily available source of primitive, undifferentiated stem cells (of type CD34 -positive and CD38 -negative). These cord blood cells can be used for bone marrow transplant . Some parents choose to have this blood diverted from

4032-442: The placenta. The fully patent umbilical artery has two main layers: an outer layer consisting of circularly arranged smooth muscle cells and an inner layer which shows rather irregularly and loosely arranged cells embedded in abundant ground substance staining metachromatic . The smooth muscle cells of the layer are rather poorly differentiated, contain only a few tiny myofilaments and are thereby unlikely to contribute actively to

4104-417: The pouch. Here it fixes onto a teat which swells inside its mouth. It stays attached to the teat for several months until it is sufficiently developed to emerge. Joeys are born with "oral shields"; in species without pouches or with rudimentary pouches these are more developed than in forms with well-developed pouches, implying a role in maintaining the young attached to the mother's nipple. Many reptiles and

4176-423: The process of post-natal closure. Umbilical cord can be detected on ultrasound by 6 weeks of gestation and well-visualised by 8 to 9 weeks of gestation. The umbilical cord lining is a good source of mesenchymal and epithelial stem cells. Umbilical cord mesenchymal stem cells (UC-MSC) have been used clinically to treat osteoarthritis, autoimmune diseases, and multiple other conditions. Their advantages include

4248-522: The risk of being iron deficient at three and six months, but an increased risk of jaundice requiring phototherapy . In 2012, the American College of Obstetricians and Gynecologists officially endorsed delaying clamping of the umbilical cord for 30–60 seconds with the newborn held below the level of the placenta in all cases of preterm delivery based largely on evidence that it reduces the risk of intraventricular hemorrhage in these children by 50%. In

4320-400: The same committee statement, ACOG also recognize several other likely benefits for preterm infants, including "improved transitional circulation, better establishment of red blood cell volume, and decreased need for blood transfusion". In January 2017, a revised Committee Opinion extended the recommendation to term infants, citing data that term infants benefit from increased hemoglobin levels in

4392-403: The single calf is normally born tail first which minimizes the risk of drowning. The mother encourages the newborn calf to rise to the surface of the water to breathe. Large mammals which give birth to twins is much more rare, but it does occur occasionally even for mammals as large as elephants. In April 2018, approximately 8-month old elephant twins were sighted joining their mother's herd in

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4464-416: The umbilical artery by vasoconstriction consists of multiple constrictions which increase in number and degree with time. There are segments of dilations with trapped uncoagulated blood between the constrictions before complete occlusion. Both the partial constrictions and the ultimate closure are mainly produced by muscle cells of the outer circular layer. In contrast, the inner layer seems to serve mainly as

4536-474: The umbilical cord in full-term neonates for a minimum of 2 minutes following birth is beneficial to the newborn in giving improved hematocrit , iron status as measured by ferritin concentration and stored iron, as well as a reduction in the risk of anemia ( relative risk , 0.53; 95% CI, 0.40–0.70). A decrease was also found in a study from 2008. Although there is higher hemoglobin level at 2 months, this effect did not persist beyond 6 months of age. Not clamping

4608-527: The use of stem cells will already exist in the cord blood), while banking for general use should be encouraged. In the future, cord blood-derived embryonic-like stem cells (CBEs) may be banked and matched with other patients, much like blood and transplanted tissues. The use of CBEs could potentially eliminate the ethical difficulties associated with embryonic stem cells (ESCs). While the American Academy of Pediatrics discourages private banking except in

4680-441: The vast majority of invertebrates, most fish, amphibians and all birds are oviparous , that is, they lay eggs with little or no embryonic development taking place within the mother. In aquatic organisms, fertilization is nearly always external with sperm and eggs being liberated into the water (an exception is sharks and rays, which have internal fertilization ). Millions of eggs may be produced with no further parental involvement, in

4752-420: The walls of the oviduct. The Lamniforme sharks practice oophagy , where the first embryos to hatch consume the remaining eggs and sand tiger shark pups cannibalistically consume neighbouring embryos. The requiem sharks maintain a placental link to the developing young, this practice is known as viviparity . This is more analogous to mammalian gestation than to that of other fishes. In all these cases,

4824-408: The water). In stage two, starting when the cervix is fully dilated, strong contractions of the uterus and active pushing by the mother expels the baby out through the vagina , which during this stage of labour is called a birth canal as this passage contains a baby, and the baby is born with umbilical cord attached. In stage three, which begins after the birth of the baby, further contractions expel

4896-412: The young are born alive and fully functional. The majority of caecilians are ovoviviparous and give birth to already developed offspring. When the young have finished their yolk sacs they feed on nutrients secreted by cells lining the oviduct and even the cells themselves which they eat with specialist scraping teeth. The Alpine salamander ( Salamandra atra ) and several species of Tanzanian toad in

4968-416: The young are born in an advanced state, but differ in that there is no placental connection and the unborn young are nourished by egg yolk . The mother's body provides gas exchange (respiration), but that is largely necessary for oviparous animals as well. In many sharks the eggs hatch in the oviduct within the mother's body and the embryos are nourished by the egg's yolk and fluids secreted by glands in

5040-638: Was found recently in a group of extinct fishes called placoderms . A fossil from Australia's Gogo Formation , laid down in the Devonian period, 380 million years ago, was found with an embryo inside it connected by an umbilical cord to a yolk sac . The find confirmed the hypothesis that a sub-group of placoderms, called ptyctodontids , fertilized their eggs internally. Some fishes that fertilize their eggs internally also give birth to live young, as seen here. This discovery moved our knowledge of live birth back 200 million years. The fossil of another genus

5112-513: Was found with three embryos in the same position. Placoderms are a sister group of the ancestor of all living jawed fishes ( Gnathostomata ), including both chondrichthyans , the sharks & rays, and Osteichthyes , the bony fishes. Among lizards, the viviparous lizard Zootoca vivipara , the Jackson's chameleon , slow worms and many species of skink are viviparous, giving birth to live young. Some are ovoviviparous but others such as members of

5184-456: Was planned but cancelled Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title Whelp . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=Whelp&oldid=549165833 " Category : Disambiguation pages Hidden categories: Short description

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