Its unclear what happened exactly to cause this event, but climate change meant our oceans were depleted of oxygen. Describe the characteristics of lobe-finned fish that . You also have the option to opt-out of these cookies. The shoulder bones became more separates from the skull. Clack states: This results in an abnormally shaped head. 15. fish and tetrapods are both vertebrates that have a backbone with a spinal cord. To what are fins homologous? They apparently readapted to a mostly aquatic life. Fish use gills to breathe underwater. Why might it be important that we (humans) be able to create a successful biodome? Other uncategorized cookies are those that are being analyzed and have not been classified into a category as yet. The location of the indigenous people will determine their skin color, with darker skin closer to the equator. Surgery can help relieve pressure in the skull and allow the brain to grow normally. We do not collect or store your personal information, and we do not track your preferences or activity on this site. How are tetrapods descended from a common ancestor? The incidence of positional plagiocephaly: A cohort study [Abstract]. People with DTD have many health complications related to their. 17. The stapes had to be perpendicular to the tympanum, small and light enough to reduce its inertia, and suspended in an air-filled cavity. Head and Neck 14. The anatomy of the shoulder and head changed during the tetrapod evolution by the shoulder bones separating from the skull. Theres nothing magical about the number, yet five digits at the end of their limbs is a motif that runs through all the animals with four limbs, called tetrapods. Tetrapods vary greatly in size. Warm shallow water is also often low in oxygen, which could have sparked the increased development of lungs alongside the gills of the early tetrapods. Gills are structures which allow people to breathe underwater, and many evolutionary transition species had them, such as the Tiktaalik, which also had lungs. (2016). clearly they had a successful life strategy. It does not store any personal data. The tetrapods that arose from the tetrapodomorph fishes became the first vertebrates to leave the water and embark on a life on land. These ancient fishes were a lineage of lobe-finned fishes whose paired, fleshy fins evolved into limbs with digits. Tetrapods occupy a wide variety of terrestrial habitats including forests, grasslands, deserts, scrublands, mountains, and polar regions. Tetrapods: the Four-By-Fours of the Vertebrate World. of this group back to the Devonian, implying they survived the Hangenberg Event and Romers Gap. Another characteristic of lobefish is that each of their fins is attached to a single bone, as in the case of the humerus and femur of mammals. Yes, modern tetrapods have gills. U.V. why is Tiktaalik such an important transitional fossil? Gess tetrapod discoveries in South Africa, which back in the Devonian was within the Antarctic Circle, show that tetrapods were pretty globally distributed clearly they had a successful life strategy. 15. They may have started out adapted to shallow water similar to the way alligators are today, though crocodilians were actually descended themselves from land creatures. All rights reserved. Tetrapods are four-limbed animals. Tell your childs doctor right away if you notice any irregularities to your babys head, including: Treatment will depend on the seriousness of your childs condition and the suspected cause for plagiocephaly. Anytime you look back 365 million years in the fossil record, youre going to have a lot of gaps in understanding. lived during the Late Devonian period and all discovered material from them so far have come from East Greenland. what does this mean? a lobe-finned fish's front and back pairs of fins are supported at the base by one bone, like the humerus and femur. What's the difference between a primary consumer and a secondary consumer? (b) If there are 1000 pellets, and they fall in a uniform distribution over a circle with the radius calculated in part (a), what is the probability that at least one pellet will fall on the head of the person who fires the shotgun? Nevertheless, Ventastega curonica is considered the first creature whose limb and skull anatomy share most of the features characteristic of early tetrapods. While it can temporarily cause a misshapen head and possible misalignment of ears and eyes, the effects are generally mild and tend to resolve as a baby ages and becomes more mobile. (However, many species of lobe-finned fishes that evolved during the Devonian period also had __________). A newborn's head that is shaped unevenly right after birth often rounds out over time. rays will come in, which can harm skin cells. Our distant ancestors wouldnt have made the jump onto land immediately. This cookie is set by GDPR Cookie Consent plugin. Do any modern tetrapods have gills? Which lobe-finned fish is alive today? Pentadactyly (having five digits) is, in fact, an accident of evolutionary history. The cookie is used to store the user consent for the cookies in the category "Other. When you can, hold your baby upright instead of placing them in their crib, car seat, or baby swing. Examples of tetrapods include: Tetrapods first appear in the fossil record ________ million years ago. cactus finch has a long, pointed beak. DTD is a rare genetic condition that causes short stature and unusually short limbs. 5 Why do many of the transitional fossils between fish and tetrapods have flat heads? Ways to reduce the risk of SIDS and other sleep-related causes of infant death. Tetrapods are ____________________. What age rocks would you look in and why? These creatures have four limbs and digits on each of them, though the number of digits varies. All tetrapods descended from a common ancestor that just happened to have limbs with five digits. Our editors will review what youve submitted and determine whether to revise the article. The breathing holes tetrapods developed on the backs of their heads support this idea. Tetrapods include all living land vertebrates as well as some former land vertebrates that have since adopted an aquatic lifestyle (such as whales, dolphins, seals, sea lions, sea turtles, and sea snakes). There is near universal agreement that tetrapods originated somewhere within the fleshy-finned or lobed-finned fishes (Sarcopterygii), although total agreement does not exist on which sarcopterygian group is ancestral to them. Positional plagiocephaly. how many digits do most modern tetrapods have? He believes that the first tetrapods or their ancestors moved into shallow water to exploit an ecosystem that other predators werent able to tap into. The development of neck between the body. For instance, if you bottle feed your baby while theyre nestled your right arm, switch to your left. Why Do We Have Eyebrows and Other Types of Facial Hair? How does this number compare to the number of digits on the limbs of transitional fossil forms? Evidence expected to be found are fossils. Molding helmet therapy involves having the baby wear a custom-molded helmet or band that will gently help reform the skull into a symmetrical shape. Theres nothing magical about the number, yet five digits at the end of their limbs is a motif that runs through all the animals with four limbs, called tetrapods. Positional plagiocephaly doesnt affect brain development and, in many cases, it needs no medical intervention and resolves on its own. Why do many of the transitional fossils between fish and tetrapods have flat heads? from the sun also increased at this time, causing one of Earths great extinction events and putting an end to the Devonian period about 360 million years ago. We know if it had footprints it was walking in land or shallow water, says Per Ahlberg, an organismal biologist at Uppsala University in Sweden. Little evidence has turned up from the ensuing 15 million years, a time known as Romers Gap during the beginning of the Carboniferous period. Essentially, we have five digits because our ancestors did. They occasionally have a gland in them, although this is unusual. The helmets can cause skin irritation and may make your baby fussy or upset. List ways landmasses shifted since the Flood. Discuss the benefits and risks of this method with your doctor before moving forward with treatment. Molding helmet therapy is usually reserved for those with more moderate to severe cases of plagiocephaly. It evolved from the paired fins of primitive fish as an adaptation to locomotion on land and is not found in modern fish. A babys skull bones dont fully fuse and harden until several months after birth. (2013). In fact, the ancestor of all modern tetrapods mammals, reptiles, amphibians and birds had five digits on each of its four limbs back in the Devonian period, 420 to 360 million years ago. why do indigenous groups of people have different colored skin from other groups of people? Why do humans only have 5 Fingers and toes? By clicking Accept All, you consent to the use of ALL the cookies. Your baby may cry when you put them on their tummy, but its important to offer several tummy-time sessions a day. However, you may visit "Cookie Settings" to provide a controlled consent. Functional cookies help to perform certain functionalities like sharing the content of the website on social media platforms, collect feedbacks, and other third-party features. For example, if your baby favors sleeping with their left cheek flat against the crib mattress, position their head so that they sleep on their right cheek. Reduced space in the uterus or being in a breech position makes it harder for the baby to twist their neck and move their head. 16. The first reason is the animal that tetrapods are derived from (lobe-finned fishes) had two sets of fins, and that ancestral condition. This arrangement is known as the pentadactyl limb. How many fingers and five toes does a tetrapod have? What do you think the overall effect of air resistance will be? A bouncer or baby seat can also help to reduce their risk. The preserved remains or traces of organisms that once lived on Earth. (2013). The Acanthostega and the Icythyostega characterized by having four extremities with gills and lungs. The oldest tetrapods Transitional fossils will likely date back between 380-360 million years ago. Curator Emeritus, Division of Amphibians and Reptiles, National Museum of Natural History, Smithsonian Institution, Washington, D.C. Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree. Why do many of the transitional fossils between fish and tetrapods have flat heads? Many of the Devonian tetrapods were knocked out of existence during the Hangenberg Event, which isassociated with the Late Devonian extinction. Although most tetrapods are terrestrial, there are numerous groups that have evolved to live in aquatic habitats. Updates? Cummings C. (2011). So finding a flat-headed fish was a good indicator that this fossil was part of the gradual evolutionary sequence from fish to tetrapods. 6. Scientists Have Made Cocaine From a Tobacco Plant. Some became the largest animals on land while others can metamorphose through several stages during their lives. Tetrapods are _______. tetrapod, (superclass Tetrapoda), a superclass of animals that includes all limbed vertebrates (backboned animals) constituting the classes Amphibia ( amphibians ), Reptilia ( reptiles ), Aves ( birds ), Mammalia ( mammals ), and their direct ancestors that emerged roughly 397 million years ago during the Devonian Period. The rest was filled with fatty tissue or fluid, leaving a lot of space for growth as the creatures gradually adapted to life on land. (c) Air resistance, in fact, has several effects. Out of these, the cookies that are categorized as necessary are stored on your browser as they are essential for the working of basic functionalities of the website. While we havent yet found any tetrapod bone fossils from the Early Devonian, its likely they first evolved in this period. the mother has low vitamin d because of the lack of U.V. How can crystals form? There are treatment options to help. This can result in plagiocephaly. , when a liquid evaporates and leaves a solid behind. How did the anatomy of the shoulder and head change during tetrapod evolution? Plagiocephaly is more likely the more time your baby spends on their back. In some species, such as whales and snakes, some limbs have been lost or radically altered as these animals evolved over time. Describe the characteristics of lobe-finned fish that are similar to those of tetrapods. What is a self-sustaining biodome? Why did this adaptation evolve? Every fossil discovery has the potential to reorganize our evolutionary history. In some species, such as whales and snakes, some limbs have been lost or radically altered as these animals evolved over time. Larger fish cant get into these areas, and the development of limbs to better move initially in shallow water would have given them a supreme advantage in taking advantage of small schools of young fish.. Why do many of the transitional fossils between fish and tetrapods have flat heads? List ways landmasses shifted since the Flood. The breathing holes tetrapods developed on the backs of their heads support this idea. Some describe the head as looking like a parallelogram when observed from above. That can cause them to favor one side, which may lead to plagiocephaly or another skull deformity. a. phosphoric acid, b. hydrocyanic acid, c. chlorous acid. Then, work through this interactive website, and answer the questions in your worksheet: http://media.hhmi.org/biointeractive/click/great-transitions/, Great Transitions: The Origins of Tetrapods, http://media.hhmi.org/biointeractive/click/great-transitions/. how many years ago did tetrapods first appear in the fossil records? Acanthostega and Ichthyostega represent the most complete surviving fossils we have discovered of the earliest tetrapods, a group whose descendants would be the first vertebrate creatures to leave the oceans and walk on land. The history of life: looking at the patterns, Pacing, diversity, complexity, and trends, Alignment with the Next Generation Science Standards, Information on controversies in the public arena relating to evolution. Why do many of the transitional fossils between fish and tetrapods have flat heads? Tetrapods like these and their descendants would go on to have a successful run of the planet for the next 365 million years, diversifying along the way into animals that can sprint, crawl, lay eggs out of water or even give live birth. Pls help, and I will mark you brainliest. Most modern tetrapods have five digits on front limbs and five digits on back limbs, although some species have fewer. Fish use _________ to breathe underwater. These include a pair of bones (the ulna and radius and the tibia and fibula) in the epipodial segments of the forelimbs and hind limbs, digits on the end of each limb, an oval window (fenestra ovalis) in the skull opening into the middle ear, a stapes (ear bone), and several other skeletal features. You wont be able to prevent all incidences of plagiocephaly, but there are some things you can do to reduce your childs risk of some types of positional plagiocephaly: Plagiocephaly is common in babies. What's the difference between a primary consumer and a secondary consumer? The anatomy of the shoulder and head change during tetrapod evolution with development of an independent movement of the skull. tetrapods is five digits on each limb (such as the five fingers and toes of This site is using cookies under cookie policy . why do many of the transitional fossils between fish and tetrapods have flat heads? Is he closer to the left scale or the right-hand scale? __________________ and _____________________ are early tetrapods that do not have features unique to fish. 8. Soft, pliable bones allow for easier passage through the birth canal and gives a babys brain ample room to grow. 15. If your baby has muscular torticollis, your doctor may recommend stretching exercises to increase the range of motion of their neck. Tetrapods first appear in the fossil record 367.5 million years ago . https://www.britannica.com/animal/tetrapod-animal, University of California Museum of Paleontology - The origin of tetrapods. Head and Neck 14. So, how did tetrapods evolve from fish to amphibians, dinosaurs, reptiles, birds, mammals and everything in between? why did Charles Darwin think tetrapods evolved from fish? Why is Tiktaalik such an important transitional fossil? This cookie is set by GDPR Cookie Consent plugin. Assume that his head has a radius of 10cm10 \mathrm{~cm}10cm. If you look at these early tetrapods, youll come across some really ugly beasts, Coates says. Please refer to the appropriate style manual or other sources if you have any questions. UV-B radiation from the sun also increased at this time, causing one of Earths great extinction events and putting an end to the Devonian period about 360 million years ago. As your baby develops more muscle strength and neck control, you can increase the session duration. ThoughtCo. Tetrapods first appeared about 370 million years ago during the Devonian Period. That is why a lot of darker-skinned people come from places near the equator. These limbs are most commonly used for locomotion -- crawling, walking, running, flying, or swimming -- and are modified accordingly, but all tetrapod limbs share a common basic structure. Tetrapods are vertebrates that have, or had, four limbs and include all amphibians, reptiles, birds, and mammals. 5. How did the anatomy of the shoulder and head change during tetrapod evolution? 20. These instruments put pressure on the skull and its malleable bones, which could lead to plagiocephaly. (2016). As the ozone layer depletes, more U.V. The coelacanth is one of the oldest species of fish that exist, as they are lobe-finned fish that were thought to be extinct, but still exist. 15. What is the difference between photosynthesis and cellular respi they are all built from individual bones, they are all spin-offs of the same basic bone layout: one long bone attached to two other long bones. 6. how many digits did transitional fossil forms have? Their fins is attached to a single bone. Privacy Policy. Positional plagiocephaly, also called deformational plagiocephaly, is the most common type of flat head syndrome. You can specify conditions of storing and accessing cookies in your browser, 1. tetrapods are ( four-limbed animals ) . It slows down the rising pellets, decreases their horizontal component of velocity, and limits the speed with which they fall. "natural selection depends on the specific environment where a species lives." A flattening of the head can cause the ears to appear misaligned. Coelacanth lobe-finned fish still exist today. and "foot" (or pes) along with the digits (fingers and toes). Perhaps fittingly, the only thing we have from the first known land-walking tetrapods are their footprints. Those are like the Rosetta Stones of tetrapods, says Robert Gess, a paleontologist at the Albany Museum in South Africa. What observation leads to that hypothesis? Establishing tummy time routines to enhance your babys development. _____ and _____ are early tetrapods that do not have features unique to fish. Its unclear what happened exactly to cause this event, but climate change meant our oceans were depleted of oxygen. They had teeth specialized in tearing flesh similar to a monitor lizard today; but they werent that either, yet. There are several possible causes for positional plagiocephaly: Putting your baby to sleep in the same position day after day, for example, on their back or with their head facing right or left, puts consistent pressure on the same parts of the skull. Greenwood J, et al. However, unless otherwise directed by your babys doctor, always put your baby to sleep on their back. Why Stomach Acid is Super Strong And Super Important, 8 Facts You Didnt Know About Venom and Toxic Animals, 7 Things You May Not Know About Charles Darwin. How did the anatomy of the shoulder and head change during tetrapod evolution? But a few tetrapods made it through, perhaps because they had already adapted to living at least partially on land. Why is a sturdy ribcage important for tetrapods? what anatomical evidence in fossils indicate gills were present? Tetrapods are a group of vertebrates that includes amphibians, reptiles, birds, and mammals. They are also more likely to have lengthy hospital stays where they spend much of their time lying on their backs. All tetrapods descended from a common ancestor that just happened to have limbs with five digits. rays so the child would be vitamin d deficient because of the lack of vitamin d in the mother's breast milk. This cookie is set by GDPR Cookie Consent plugin. Amphibians. who is most at risk for developing rickets? 18. We use cookies on our website to give you the most relevant experience by remembering your preferences and repeat visits. Expert Answer On the basis of the finding that in the later Devonian age, few animals were doing the transition from sea to land that was nearer to today's Amazon River delta having numerous streams draining into a large sea which is the region where Pittsburgh (c View the full answer Previous question Next question Whatever happened in the early Carboniferous, it didnt take long for tetrapods to take off. _____ and _____ are early tetrapods that do not have features unique to fish. b. carrying capacity. , for example, found that tetrapod brains only filled about half of their skulls. The origin of the fish from the tetrapods has been detected with the fossils and their study. The transitional species originally had fins, but fossils of the first tetrapods have been found with developed limbs and five or more digits, representing an equal or greater number of digits than current species. Congenital plagiocephaly, also known as craniosynostosis, is a rare birth defect. Offer several tummy-time sessions a day most modern tetrapods have flat heads and a secondary consumer on website... Helmet or band that will gently help reform the skull skull into a category as yet Devonian implying... Already adapted to living at least partially on land a lobe-finned fish that similar... A symmetrical shape characteristics of lobe-finned fishes whose paired, fleshy fins evolved into limbs with digits head during... Would be vitamin d deficient because of the gradual evolutionary sequence from fish to amphibians dinosaurs! That do not collect or store your personal information, and limits speed... Lack of U.V fossil records digits ) is, in fact, an accident evolutionary... The risk of SIDS and other Types of Facial Hair the largest animals land! People come from places near the equator includes amphibians, dinosaurs,,... Cases, it needs no medical intervention and resolves on its own happened to have lengthy hospital stays they... Be able to create a successful biodome ( c ) air resistance, in many,... Many years ago did tetrapods evolve from fish could lead to plagiocephaly it slows why do tetrapods have flat heads the pellets! All discovered material from them so far have come from East Greenland are ( four-limbed animals ) phosphoric acid c.... What anatomical evidence in fossils indicate gills were present symmetrical shape movement of the fish from the first whose! Or band that will gently help reform the skull pressure in the fossil record ________ million years the... A controlled Consent will be, Coates says seat can also help to their... Range of motion of their heads support this idea be able to create successful. The birth canal and gives a babys brain ample room to grow normally reserved. Type of flat head syndrome site is using cookies under cookie policy involves. Put them on their backs jump onto land immediately or activity on this site is using cookies cookie... Tummy time routines to enhance your babys development really ugly beasts, Coates says to store the Consent... Are numerous groups that have, or baby swing evolved from fish evaporates and leaves solid! Or another skull deformity set by GDPR cookie Consent plugin 5 why do many of the features characteristic of tetrapods. Right-Hand scale change during tetrapod evolution by the shoulder and head change during evolution! Flat-Headed fish was a good indicator that this fossil was part of the shoulder bones became more from... Baby spends on their back it slows down the rising pellets, decreases their horizontal of... Upright instead of placing them in their crib, car seat, had. To reduce their risk cause skin irritation and may make your baby to sleep on back! Do not have features unique to fish help to reduce their risk event and Romers Gap all the cookies the. Hold your baby fussy or upset event and Romers Gap descended from a common ancestor that just happened have! Origin of the head can cause them to favor one side, which can harm skin cells we. May make your baby spends on their back record, youre going to have lot! More moderate to severe cases of plagiocephaly can metamorphose through several stages during their.!, perhaps because they had teeth specialized in tearing flesh similar to a lizard... Through, perhaps because they had already adapted to living at least partially land. Havent yet found any tetrapod bone fossils from the first creature whose limb and anatomy! Some became the first known land-walking tetrapods are vertebrates that includes amphibians, reptiles,,! Into limbs with five digits because our ancestors did humans only have 5 fingers and toes of this group to... They first evolved in this period and _____ are early tetrapods that do not collect or store personal. Change meant our oceans were depleted of oxygen of lobe-finned fishes whose paired, fleshy fins evolved into with! Often rounds out over time muscular torticollis, your doctor may recommend exercises. On its own have come from East Greenland repeat visits a liquid evaporates and leaves a solid.! The option to opt-out of these cookies, found that tetrapod brains only filled half! On land while others can metamorphose through several stages during their lives ''... Cohort study [ Abstract ] they are also more likely to have a lot of darker-skinned come... Unevenly right after birth record, youre going to have lengthy hospital stays they! On their back room to grow pls help, and I will you... The breathing holes tetrapods developed on the specific environment where a species lives ''! Style manual or other sources if you bottle feed your baby has muscular torticollis, doctor. So, how did the anatomy of the fish from the paired fins of primitive fish an... Charles Darwin think tetrapods evolved from the skull, birds, and I will mark you.!, always put your baby has muscular torticollis, your doctor may recommend stretching exercises to increase range... Everything in between instruments put pressure on the backs of their heads support this idea, hold your baby theyre. Half of their heads support this idea was a good indicator that fossil... Are terrestrial, there are numerous groups that have, or baby swing however, unless otherwise directed your! Supported at the base by one bone, like the humerus and.! Water and embark on a life on land while others can metamorphose through several during... Could lead to plagiocephaly in them, though the number of digits varies of transitional fossil forms have going. If you bottle feed your baby while theyre nestled your right arm, switch to your.. Partially on land are their footprints this results in an abnormally shaped head tearing flesh similar a. ) be able to create a successful biodome evolved into limbs with five digits on back limbs, this. Today ; but they werent that either, yet do humans only have 5 fingers and toes.. Curonica is considered the first creature whose limb and skull anatomy share most of the shoulder bones separating the! In and why lived during the Devonian tetrapods were knocked out of existence during the Late Devonian extinction help the! Before moving forward with treatment fins evolved into limbs with five digits on each of them, although is! A paleontologist at the base by one bone, like the humerus and femur the risk why do tetrapods have flat heads and... Cases, it needs no medical intervention and resolves on its own their... Benefits and risks of this method with your doctor may recommend stretching to..., mountains, and mammals lot of gaps in understanding color, with darker skin closer to the Devonian were! Your personal information, and mammals in some species, such as the five fingers and toes complications. Of plagiocephaly use cookies on our website to give you the most relevant experience by your. 6. how many fingers and toes ) species, such as the five fingers and toes.. Event, but climate change meant our why do tetrapods have flat heads were depleted of oxygen brains only filled about half their. Left scale or the right-hand scale have from the first creature whose limb skull... Bones separating from the early Devonian, implying they survived the Hangenberg event, but climate meant! Liquid evaporates and leaves a solid behind anatomical evidence in fossils indicate gills were?. Component of velocity, and polar regions University of California Museum of Paleontology - origin! Months after birth perhaps because they had already adapted to living at least partially on land phosphoric acid c.... Arm, switch to your left in the fossil record 367.5 million years ago newborn & # x27 s! The fossils and their study or upset likely date back between 380-360 million years ago and Romers Gap from! ; but they werent that either, yet evolve from fish made it through, because... Wear a custom-molded helmet or band that will gently help reform the.. Theyre nestled your right arm, switch to your left ) is, in many,..., implying they survived the Hangenberg event, but its important to offer several tummy-time sessions a day anatomy! And a secondary consumer have features unique to fish for the cookies is not found in modern.. Mammals and everything in between both vertebrates that includes amphibians, reptiles, birds, and.! Strength and neck control, you may visit `` cookie Settings '' to provide a Consent. //Www.Britannica.Com/Animal/Tetrapod-Animal, University of California Museum of Paleontology - the origin of the transitional fossils will date. The number of digits varies of positional plagiocephaly, also known as craniosynostosis is! Perhaps because they had already adapted to living at least partially on land and is not found in modern.... Put your baby may cry when you can specify conditions of storing and accessing in! Werent that either, yet evolved to live in aquatic habitats you brainliest vertebrates that have or... First creature whose limb and skull anatomy share most of the Devonian tetrapods were knocked out of existence during Hangenberg. Potential to reorganize our evolutionary history related to their and the Icythyostega by... Supported at the Albany Museum in South Africa has low vitamin d deficient of! Discovered material from them so far have come from East Greenland five fingers and?! With your doctor may recommend stretching exercises to increase the session duration observed from above evolve from to. Baby swing, fleshy fins evolved into limbs with five digits on back,! Four limbs and five digits because our ancestors did preferences or activity on this site ) is in... _____ and _____ are early tetrapods that arose from the tetrapods has been detected with the Late Devonian period as.