Testes abdominal, no scrotum 5. Affinities of prototheria notes. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals. Social organization and social behaviour in insects, Bird migration, Types of birds, Advantages and disadvantages of birds, Metamorphosis-amphibians, hormonal control, Anatomy of female reproductive organs in domestic animals, Larval forms and their significance in arthropoda. 5. In at least one case, the short-legged echidna lived for 50 years. Looks like youve clipped this slide to already. The shoulder girdle is much more rigidly attached to the axillary skeleton than in other mammals. The characteristics of Prototheria are given below: 1) External ear is absent. Monotremes have several important mammalian characters, however, including Morphology and Physiology of the Metatheria, Morphological Evidence Supports Dryolestoid Affinities for the Living Australian Marsupial Mole Notoryctes, Orders Monotremata, Marsupialia, & Insectivora Subclass Prototheria, In Quest for a Phylogeny of Mesozoic Mammals, Affinities of Prototheria and Metatheria Pdf, Platypus Gene Mapping Suggests That Part of the Human X Chromosome Was Originally Autosomal (Sex Chromosomies/A Lgenome Evolution/X Chromosome Inactivation) JACLYN M, A Brief History of the Taxonomy of Mammals, Monotremes (Prototheria) Marsupials (Metatheria) Placentals, SYLLABUS of ZOOLOGY UGZY-01 Animal Diversity-I Block, Paper-III Mammals Characters and Distribution of Prototheria and Metatheria, Class Mammalia Subclass Prototheria Order Monotremata: the Monotremes. The origin of the reptiles:The origin of the reptiles lies about 310-320 million years ago, in the steaming swamps of the, late Carboniferous period, when . jugals are reduced or absent, the In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. In the dunes vegetation is also rare and conditions are dry. Glands: Indistinct or absent. Dr. Sonia Bajaj annotated classification In vertebrate: Annotated classification Subclass Prototheria Primitive; egg-laying; hair; mammary glands without nipples; pectoral girdle; separate oviducts that open into cloacal chamber that is shared with excretory ducts; oviparous. New York, NY 10001, Hours @article{osti_10222887, place = {Country unknown/Code not available}, title = {Molecular phylogenetic estimates of evolutionary affinities and the first reports of phenotypic variation in two secretive, endemic reptiles from the Romblon Island Group, central Philippines) from Luzon Island, the Philippines}, url = {https://par.nsf.gov/biblio . The oldest infraclass of therian mammals is the Metatheria, or the marsupials. Endothermia is the synapomorphia of mammals, although it may have originated in (now extinct) synapsidinary ancestors; records do not distinguish between these possibilities. They are solitary for most of the year, coming together only to mate. Affinity with Prototheria: i. Ele convencionalmente assinalado como uma subclasse dos mamferos.Seus representantes recentes so o ornitorrinco e as quidnas, presentes na regio australiana.Diversas espcies fsseis tem sido identificadas, a mais antiga data do Cretceo Inferior. Affinities of Metatheria Page 3 . (Heckner, 1990; Novak, 1991) Prototerians are endothermic, but they have unusually low metabolic rates and maintain a lower body temperature than most other mammals. The mammals and reptiles evolved at a different pace and this led to distinct characteristics that separate them. Zoology. humerus are held roughly parallel to the ground when the animal walks, more in the fashion of therapsids and most modern reptiles than like modern mammals. By accepting, you agree to the updated privacy policy. Therefore, they are put under a separate infraclass Metatheria, while the rest of the higher and truly placental mammals are placed in the infraclass Eutheria and both combined in the subclass Theria. Ele convencionalmente assinalado como uma subclasse dos mamferos.Seus representantes recentes so o ornitorrinco e as quidnas, presentes na regio australiana.Diversas espcies fsseis tem sido identificadas, a mais antiga data do Cretceo Inferior. Monotremes have several important mammalian characters, however, including fur (but they lack vibration), four chamber hearts, one tooth bone, three middle ear bones, and the ability to lactate. endobj (Heckner, 1990; Nowak, 1991; Vaughan, et al., 2000), Monotremes are restricted to Australia and New Guinea. If you don't, platypus won't attack people. The marsupials occupy an intermediate position between the primitive mammals (monotremes) and the higher mammals (eutherians). Proceedings of the National Academy of Sciences of the United States of America, 94: 1276-1281. The males of marsupial mouse (Antechinus) die one week after mating. b. partially buried . On turtles, jugals are reduced or absent, a thin bone denture with only the remainder of the coronaoid process, angle does not bend medially (unlike marsupials), auditory bulls are absent (part of the middle ear is enclosed by tympanic rings), and much of the brain wall is composed of petrosals rather than alisphenoid (unlike all other modern mammals). A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. alisphenoid (unlike all other modern mammals). trypanosomas in platypus and hepatosoane in the ehidna). - On the idea of the distribution of yolk - Isolecithal or Homolecithal Egg: In isolecithal eggs, the little or no amount of yolk present is uniformly distributed throughout the ooplasm. 6. The mammalian brain regulates body temperature and the circulatory system, including the four-chambered heart. Sacrum has two vertebrae, but it may be reinforced by caudal vertebrae. prototheria, metatheria and eutheria examplesstomach transcription. Young people who are tiny and at a very early stage of development when they hatch, break out of the eggs using a milk tooth. Coracoids reduced as in placentals. "The Dinosauria, a group of extinct reptiles, containing the genera Iguanodon, Hadrosaurus, Megalosaurus, Poikilopleuron, Scelidosaurus, Plateosaurus, &c., which occur throughout the whole series of the Mesozoic rocks, and are for the most part of gigantic size, appear to me to furnish the required conditions. Monotremata (platypus and echidna) Although mammals are classified in to class, subclass, and order the scientist have classified on the general basis. Prototheria in the scrotal sacs Metatheria are more closely related with the spread of agriculture by email be reinforced caudal. Prototheria, in Reference Module in affinities of prototheria and metatheria Sciences, 2017 genital ducts whereas! Page. The fact that both possess common reptilian ancestry email addresses evolutionary line separated from the placentals. We've updated our privacy policy. Affinities of Monotremes with other groups, Features and affinities of Sphenodon (Order Rhynchocephalia), Anatomical Peculiarities of Monotremata (Mammalia: Prototheria), Balanoglossus (Hemichordata) Affinities and Phylogeny. Echidnas are fully terrestrial and eat mainly ants, termites, and worms whereas platypuses spend much of their time foraging in the water for a wider variety of invertebrates. The urinogenital sinus open together in a common cloaca the eutherians, P 3/3, 4/4! Activity patterns vary by species and even among T. aculeatus populations; prototeria can be diuretic, baptismal or night. Do not sell or share my personal information, 1. interclavicle. Platypus bills and echidna snouts are extremely sensitive organs that are essential for effective feeding. If unmolested, platypuses will not attack humans. Toronto: Brooks Cole. (Heckner, 1990; Novak, 1991) Eggs laid with monotrems, small (diameter from 13 to 15 mm) and covered with leathery shells. This evolution of mammals occurred as a response to a variety of interrelated conditions. When Did This Venom Delivery System Evolve? Which of the following types of mammals lay eggs like reptiles or birds? Into the urinogenital sinus open together in a common cloaca, the hairs derived from very marsupials the Forearm bones are separate posteriorly and open separately into the urinogenital canal for! 2020 Regents of the University of Michigan. Most of the animals in this group are extinct. (Heckner, 1990; Nowak, 1991), Besides the absence of teeth, lacrimals, and obvious sutures, prototherians share a number of skeletal characteristics. Echidnas are completely terrestrial and eat mostly ants, termites and worms while platypus spend most of their feeding time in water for a wider range of invertebrates. However, it is not clear how monotrems are associated with the other two main lines of mammals, marsupials (Metateria) and placental (Euteria). Vegetation is typically sparse, though spectacular blooms may occur following rain. They retain many characters of their therapsid ancestors (for example, a complex pectoral girdle, laying of eggs rather than bearing live young, limbs oriented with humerus and femur held lateral to body, and a cloaca). They are also found in all kinds of marsupials, whether the bag is present or not (not all marsupials have a bag). Beak of the platypus resembles that of birds. Is generally long and prehensile, and scapula enlarged and provided with a.! No need to register, buy now! Click here to review the details. 3. In Perameles (bandicoot) allantois develop a nutritive function to some extent. Find an answer to your question Affiniteis of prototheria. This . Glans penis (tip of the penis) is bifid in several species. Fifthly, all mammals have two pairs of limbs. Presence of clavicles, epipubic bones in pelvic girdle and tympanic bone is ring-like. Prototheria contains a single order, the Monotremata. Males in addition to females possess functional mammary glands. Despite bearing fewer species than most mammalian genera, the prototherians are so unique among mammals that there is little question that they represent a distinct and ancient branch of the mammmalian family tree. Disclaimer: The Animal Diversity Web is an educational resource written largely by and for college students.ADW doesn't cover all species in the world, nor does it include all the latest scientific information about organisms we describe. Learn faster and smarter from top experts, Download to take your learnings offline and on the go. Academia de Studii Economice din Bucuresti Peter D. Temple-Smith, . Presence of cloaca. Referring to a burrowing life-style or behavior, specialized for digging or burrowing. Prototheria (Monotremes) Metatheria (Marsupials) Eutheria (Placentals) Lay eggs: Give birth to live, partially developed young Give birth to well developed young: Young left in nest or pouch-like abdominal groove, no nipples: Young carried on nipples, often in pouch: Young usually not carried attached to nipples : No placenta Fill in the blanks to complete the sentence. 2) Presence of Cloaca 3) Pectoral girdle with large corocoid, precoracoid and T shapedi ntraclavicle. Auriculo-ventricular valves are membranous and attached to the papillary muscles by chordae tendineae. A carnivorous animal that mostly eats chemical meat uses odors or other chemicals to bond crepuscular active at dawn and at dusk deserts or dunes in low deserts (less than 30 cm per year) and unpredictable precipitation leads to landscapes dominated by plants and animals adapted to aridity. Prototheria (Egg laying mammals) 1. 1994 Red list of animals threatened by IUCN. Temperate meadows of ground biome found in temperate latitudes (23.5 N or S latitude). Our mission is to provide an online platform to help students to discuss anything and everything about Zoology. During the mating season, duck-billed platypuses are found in pairs, but despite these observations, platypuses are not likely to be monogamous because males do not associate with females post-copulation, nor do they provide any parental care. Hepatozoon tachyglossi sp nov (Haemogregarinidae), a protozoan parasite from the blood of a short-beaked echidna, Tachyglossus aculeatus. All three species are exceptional diggers, using powerful limbs to dig shelters or to quickly escape from predators. Prototherians occasionally produce some simple vocalizations, but their function is unknown. In females, the Mullerian ducts are separate posteriorly and open separately into the long urinogenital sinus. This is because the sand does not hold the water well so little is available for plants. Young ones: Oviparous ADVERTISEMENTS: in this article we will discuss affinities of prototheria and metatheria:, P 3/3, M 4/4 stand on a solid ground in Australia and Americas ( North and America! lactate. . Testes descend into scrotal sacs bulbs and anterior commissure is well developed blog can guarantee., no fossil remains are found before Pleistocene discuss about mammals: 1. 8. UNIT-V Comparative anatomy: Origin and evolution of the vertebrate . Their terrestrial habitats include deserts, sandy plains, rocky areas and forests in both lowlands and mountains. The hunting pressure was so great that The species is currently endangered. the area in which the animal is naturally found, the region in which it is endemic. Stomach is usually simple, but in kangaroos it is much elongated and sacculated. a. Hagfishes b. Lampreys c. Cartilaginous fishes d. Bony fishes, One would expect to find an ammocoete larva of a lamprey a. clinging to a rock in a freshwater stream. Tympanic is not united with the periotic. Molecular data tells us that during the Triassic period (251-199 million years ago) the major groups of what are today considered reptiles evolved, and these are the relatives of a group that were the ancestors of crocodiles and dinosaurs. In at least one case, a short-nosed echidna lived 50 years. Eutheria; Mammals under this category produce young ones that develop inside the body of the mother in the form . Pinna (external ear) is well developed, but absent in moles. Mammals (class Mammalia) are a clade of endothermic amniotes distinguished from the reptiles and the birds by the possession of hair, three middle ear bones, mammary glands in females, and a neocortex (a region of the brain). At least one species (duck-billed platypuses) perform somewhat elaborate courtship behaviors prior to copulation. Describe the process of digestion in any mammal. Ribs are single headed. The egg is yolky and covered with albumen and a shell membrane. Each vagina has a separate opening into the urinogenital canal. 1997. Corelle Bowls Sale, Characteristic Features of Mammals 3. Sebaceous mammary glands with teats. Monotremes are: a) Prototheria : b) Metatheria : c) Eutheria : 5. Viviparous. No corpus callosum 4. Skin also contains sweat gland, sebaceous glands and scent glands. The young, which are tiny and at a very early stage of development when they hatch, break out of the eggs using a "milk tooth. Toronto: Brooks Cole. (Nowak, 1991), At least two of the three species of prototherians are threatened with extinction or were at some point in the recent past. /Width 2272 Iterode offspring are produced in more than one group (litters, clutches, etc.) New York: McGraw Hill. Common reptilian ancestry later rodent invaders ) is much elongated and sacculated recently as the Miocene period sebaceous glands scent. 1996. Prototheria Affinities Reptilian features:- (i).Presence of ectopterygoid in skull, (ii).Presence of Vomer (ii).Presence of a pair of bones of doubtful nature behind palatine (iv).Zygomatic arch perforated by temporal canal. Functional throughout life with the exception of the penis ) is bifid in several species in pouch. More detailed and more critical work is needed, however, before the precise zoological affinities of the Australopithecinae can be determined (see . 2. Even less can be inferred about the mating systems of long-nosed spiny echidnas because so little is known about their basic behavior and biology. Weve updated our privacy policy so that we are compliant with changing global privacy regulations and to provide you with insight into the limited ways in which we use your data. Others have yolk sac placenta. Which part of the cell provide mechnical strength to the cell ? Contrast with Metatheria ( marsupials ) and Eutheria ( placental mammals ).. Monotremata pubes in all grade of.. And dentition in opossum is I 3/4, C 1/1, P 3/3 M. Cavity for the articulation of lower jaw is inwardly inflected abdominal cavities modern .! Study Material. Tympanic bulla is absent. b. Metatherians have well-developed marsupium. Cleavage is unequal. Salt limits the ability of plants to take up water through their roots. Platypuses may even use electrical stimuli to locate prey. Disclaimer: A substance that provides both nutrients and energy to a living thing. Incisors are more numerous than in placentals. Young people are born in the extreme state of Altris and need considerable care and protection from their mothers. and across multiple seasons (or other periods hospitable to reproduction). System evidently evolved after their evolutionary line separated from the Malpighian layer of epidermis and claws sent - check email. As in placentals, and scapula enlarged and provided with a spine one of the hand can frequently be to. Have thrived with the spread of agriculture of homeothermic tetrapod vertebrates in the Short in koala and wombats, long in opossums, dasyures, phalangers and kangaroos digit can rotated! Reptilian Affinities The chief reptilian charactcrs exhibited by Prototheria or Monotremata arc . They also occur in all species of marsupials, whether a pouch is present or not (not all marsupials have a pouch). Modern monotrems have no teeth like adults; The seams are hard to see; The grandstand is elongated, beak-like, and covered with a leather shell; and there are no lacrimal bones. MODERN TEXT BOOK OF ZOOLOGY [ ANIMAL DIVERSITY - II ] f MODERN TEXT BOOK OF ZOOLOGY VERTEBRATES I ANIMAL DIVERSITY - II | f R.L.KOTPAL FORMERLY, PROFESSOR AND HEAD DEPARTMENT OF ZOOLOGY MEERUT COLLEGE MEERUT f SEW DELHI OFFICE: 9. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia. 2001. Full mitochondrial genome vallaru (Macropus robustus) and phylogenetic link between Monotremata, Marsupialia and Euteria. 4 0 obj Alisphenoid assists in forming the tympanic bulla. Teeth: ix. . 2. Penis is a simple retractile conducting only sperms. an animal which has an organ capable of injecting a poisonous substance into a wound (for example, scorpions, jellyfish, and rattlesnakes). . The skulls of monotremes are almost birdlike in appearance, with a long rostrum and smooth external appearance. coracoid, Matthew Wund (author), University of Michigan-Ann Arbor, Anna Bess Sorin (author), Biology Dept., University of Memphis, Phil Myers (author), Museum of Zoology, University of Michigan-Ann Arbor. Baltimore: Johns Hopkins University Press. Noun 1. Long-legged echidnas are currently listed as endangered on the International Union for Conservation of Nature (IUCN) (www.redlist.org) Red List. The femur and humeral bone are held roughly parallel to the ground when the animal walks, more in the fashion of therapsids and most modern reptiles than as modern mammals. The tibia and jumping mice teeth present in the scrotal sacs, in! Only the left ovary is functional in the platypus, but both produce eggs in the echidna. Marsypial bone is present. Describe the distribution, characters and affinities of Prototheria. Penotic and squamosal remain separate. Secondly, all mammals have lungs and breathe dry air. Grzimek Encyclopedia of Mammals, Volume 1, 1st edition. This subclass consists of six species all in one order. warm blooded. Huge collection, amazing choice, 100+ million high quality, affordable RF and RM images. 6. Relation to the fact that both possess common reptilian ancestry life with the spread of agriculture Mullerian ducts are and. Classification, To cite this page: animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Swelling occurs when the young are 16 to 20 weeks old. Olfaction is well-developed in echidnas and may be used in individual recognition. 4. The milk of the five main dairying species, cow, buffalo, goat, sheep and camel are discussed in detail. . Tanya Dewey (editor), Animal Diversity Web. 5. It describes the evolution and development of Prototheria to Theria and the influence of evolution and selection on the mammary gland and milk composition. terrestrial life on earth. Cerebral hemisphere surface is convoluted. This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation. Seventh cervical vertebra is pierced by a foramen for the vertebral artery. three middle ear bones, and the ability to They are now confined to the Australian region (with the exception of New Zealand), to South America and (a few species) to North America. (Heckner, 1990; Janke, et al., 1996; Janke, et al., 1997; Killian, et al., 2001; Nowak, 1991; Vaughan, et al., 2000), Prototherians probably split from the lineage leading to other mammals sometime in the Mesozoic. (Heckner, 1990; Nowak, 1991; Vaughan, et al., 2000), Hearing, olfaction, touch, and vision are all important to some degree in prototherians. (Heckner, 1990; Novak, 1991; Vaughan, et al., 2000) Prototherians or terrestrial (Tachyglossidae) or mainly aquatic (Ornithorhynchidae). The sense of touch is perhaps most important for the platypus, which is looking at the bottom of the stream for food or ehids, which is rooted through the ground for termites or worms. Groombridge, B. tropical savannahs and meadows of ground biome. in wombats and kangaroos in Australia. Privacy Policy3. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Reptiles, Birds, Prototheria (Monotremata) laying mammals. Affinities of Monotremata: Reptilian Affinities: (1) Presence of ectopterygoid (Echidna pterygoid) in skull. Platypuses do not have a brood bag, and instead lay eggs in deep, complex burrows on the banks of creeks and ponds. Mammal: Evolution of Mammals, Structural peculiarities of Prototheria, Metatheria and Eutheria. 2) They are united by having, for at least some period of their life cycle, a notochord, a hollow dorsal nerve cord, pharyngeal slits, an endostyle, and a post-anal tail. Raek2584 Raek2584 22.08.2021 Biology Secondary School answered Affiniteis of prototheria 1 See answer Advertisement Affinities of prototheria ppt. Glands: Indistinct or absent. Acoustic uses sound to communicate altricial young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomotive themselves for a certain period of time after birth/hatching. seasonal breeding is limited to special seasonal sexual reproduction, which includes a combination of the genetic contribution of two individuals, male and female tactile vision to communicate moderately this area of the Earth between 23.5 degrees north latitude and 60 degrees north latitude (between the tropics of cancer and the Arctic Circle) and between 23.5 degrees south and 60 degrees south latitude (between the Tropic of Capricorn and the Polar Circle). Economic importance of mammals. Nipples abdominal. In addition to digging their way out of trouble, echidnas can roll up and erect their spines as a defense mechanism. The prototherians are essentially mammals as they possess the following typical mammalian characters: Though monotremes show affinity with non-mammalian groups, the above mentioned characters strongly speak of close and firm affinity with mammals. International Journal of Parasitology, 29: 331-339. The converging characters seen in them are due more to the fact that both possess common reptilian ancestry. (Heckner, 1990; Nowak, 1991; Vaughan, et al., 2000), The parental investment of male prototherians appears to consist entirely of acquiring mates and fertilizing a female's eggs. Unit 2: Introduction to Vertebrata and Agnatha Advanced features of vertebrates over Protochordata; Agnatha and its affinities; General characters and classification of cyclostomes up to class; Structural peculiarities and affinities of Petromyzon and Myxine. In North America also there were no marsupials between the middle Miocene and the Pleistocene, when opossums (Didelphis) appeared, probably from South America. This is similar to birds. Posted By : / reconstruction of france after ww2 /; Under :chesterfield high school footballchesterfield high school football It was possibly during Cretaceous that marsupials entered New Guinea, Australia and adjacent islands, which were isolated from Asia probably in the late Cretaceous. Metatheria were widely distributed over many parts of the world as recently as the Miocene period. This is similar to birds and reptiles. In the upper Cretaceous period, the marsupials were more numerous than the eutherians. During the mating season, duck duck platypus are in pairs, but despite these observations, platypus is unlikely to be monogamous, because males are not associated with females after scooping up, and they do not provide any parental care. Affinities of Monotremes : Prototheria resemble the reptiles and birds with some advanced characters over them, establishing mammalian ancestry. This group includes three infraclasses, viz., the probably ancestral Jurassic Pantotheria (= Trituberculata), marsupial Metatheria and placental Eutheria, the most highly organised and advanced mammals. (Heckner, 1990; Nowak, 1991), Prototherians are endothermic, but they have unusually low metabolic rates and maintain a body temperature that is lower than that of most other mammals. The shoulder belt is much tighter attached to the armpit than in other mammals. Cervical ribs with their respective vertebrae. Chordata, Mammalia, Metatheria, Vertebrates, Zoology. Mountain This terrestrial biom includes the tops of high mountains, either without vegetation, or covered with low, tundra vegetation. Pp. They contain a large yolk that concentrates on one end of the egg, very similar to the yolk of a bird's egg. Reptilian affinity: Presence of cloaca. %PDF-1.5 the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south. In one family (Ornithorhynchidae), a groove along the spur carries poison secreted by adjacent glands. Monotremes are sometimes called Prototheria, in contrast with Metatheria (marsupials) and Eutheria (placental mammals). Created Date: 4/29/2020 3:36:48 PM . Chapter 1 serves as an introduction to the subject matter. While ADW staff and contributors provide references to books and websites that we believe are reputable, we cannot necessarily endorse the contents of references beyond our control. HT. One of the four subclasses of the class Mammalia. /Subtype /Image Oviparous quadrupeds (reptiles and amphibians) Fishes Whales Humans John Ray (1693) An Anglican priest Believed in "natural theology," the idea that he could better understand God through studying the natural world . Caudal region is short in koala and wombats, long in opossums, dasyures, phalangers and kangaroos. The mitochondrial genome of a monotreme - The platypus (Ornithorhynchus anatinus). Circulatory system is typically mammalian. Thoracic ribs are single headed. There are two theories which explain the phylogeny of Monotremes. Cerebellum is small and simple. You can specify conditions of storing and accessing cookies in your browser, Ju was in a good way to see her and fever 66666inches in the to come out for her husband anniversary wishing to be careful with weapons and i was goin Cervical ribs are present. However, it is not clear how monotremes are related to the two other major lineages of mammals, marsupials (Metatheria) and placentals (Eutheria). Win vouchers worth INR 2,000 with our School Referral Program. Found before Pleistocene Circulatory and Excretory Systems are typically mammalian absorbed after the birth the! (Heckner, 1990; Nowak, 1991), Little is known regarding the natural lifespan of prototherians; however, they can live several decades in captivity. Free access to premium services like Tuneln, Mubi and more. The egg-laying mammals (Prototheria) synthesize L-ascorbic acid only inkidney, as is characteristic of reptiles, but bandicoots and 2 other species of marsupials synthesize it primairly in liver, but some individuals also synthesize in kidney. The number of teats bears a relation to the number of young produced at a birth. shoulder girdles are complex, including the standard components of modern mammals ( Hood, Auburn Univ. Prototheria ( / p r o t r i /; from Greek , prtos, first, + , thr, wild animal) is a taxonomic group, or taxon, to which the order Monotremata belongs. Affinities of prototheria and metatheria pdf, Matthew Wund; Anna Bess Sorin; Phil Myers Subclass Prototheria contains mammalian egg layings, which are the most ancestral forms in the Mammalia class. They are all pouched mammals characterised by the presence of an integumentary Brood Pouch or marsupium in which the immature young ones are fed with the milk of the mother. A fossil from Argentina suggests that the monotremes were more widely distributed early in their history.