Infobox Embryology Name Notochord Latin notochorda GraySubject 8 GrayPage 52 Image Gray19 with color.png ... CarnegieStage Days Precursor chordamesoderm GivesRiseTo nucleus pulposus MeshName Notochord MeshNumber A16.254.610 Code Terminologia Embryologica TE E5.0.1.1.0.0.8 The notochord is a flexible, rod ... body of the vertebral column . The notochord is found anatomical terms of location ventral ... discs . Development of the notochord Notogenesis is the development of the notochord by the epiblast ... triderm03.html Human Embryology . The notochord arises from the bilaminar embryonic disk. citation needed date January 2011 The notochord forms during gastrulation and soon after induces the formation ... of polygonal shaped cells the notochord which is then separated from the endoderm. citation needed date ... , which grows medially and surrounds it. From the mesoderm surrounding the neural tube and notochord .... citation needed date January 2011 Postembryonic vestige of the notochord is found in the nucleus ... cells usually regress entirely. In humans, by the age of 4, all notochord residue is replaced ..., may give rise to Tornwaldt s cyst . The notochord in neural development Research into the notochord ... and expressing a second notochord near the anatomical terms of location dorsal neural tube, 180 degree angle degree s opposite of the normal notochord location, one can induce the formation of motoneuron ... The notochord secretes a protein called sonic hedgehog sonic hedgehog homolog SHH , a key morphogen ... Cell doi 10.1016 0092 8674 93 90627 3 ref The secretion of SHH by the notochord establishes the ventral pole of the dorsal ventral axis in the developing embryo. Evolution of the notochord File Lungs of Protopterus dolloi.JPG thumb A dissected Protopterus lungfish showing the notochord The notochord ... as a convergence. Pikaia appears to have a proto notochord, and notochords are present in several .... Several species see list below have reverted to the primitive state, retaining the notochord ... more details
Infobox Embryology Name PAGENAME Latin GraySubject 6 GrayPage 50 Image Gray19 with color.png Caption Transverse section of a chick embryo of forty five hours incubation. BR Chordamesoderm yellow, at notochord . BR Paraxial mesoderm red, at somite . BR Intermediate mesoderm purple, near Wolffian duct . BR Lateral plate mesoderm purple, near Somatic mesoderm and Splanchic mesoderm . Image2 Caption2 System CarnegieStage Days Precursor GivesRiseTo mesoderm , notochord MeshName MeshNumber DorlandsPre c 31 DorlandsSuf 12236926 Chordamesoderm , also known as axial mesoderm , is a type of mesoderm that lies along the central axis, under the neural tube . will give rise to notochord starts as the notochordal process, whose formation finishes at day 20. important not only in forming the notochord itself but also in inducing development of the overlying ectoderm into the neural tube will eventually induce the formation of vertebral bodies. ventral floor of the notochordal process fuses with endoderm. The notochord will form the nucleus pulposus of interverterbral discs. There is some discussion as to whether these cells contributed from the notochord are replaced by others from the adjacent mesoderm. It gives rise to the notochordal process which later becomes the notochord External links http instruct1.cit.cornell.edu courses biog105 pages demos 106 unit03 17d.notochorddev.html Diagrams at cornell.edu developmental biology stub Gray s Embryology Category Embryology Category Developmental biology ... more details
unreferenced date September 2009 The stomochord is a flexible, hollow tube found in hemichordates . Stomochords were initially considered a variant of a primitive notochord , but are now recognized to not share histological composition to that of the notochord found in chordates. citation needed date September 2009 Stomochords arise in embryonic development as an outpocketing from the roof of the embryonic gut anterior to the pharynx. In adults, they extend dorsally from the pharynx into the probiscis, and serve to communicate with the oral cavity. Their walls are composed primarily of epithelial cells , but ciliated and glandular cells are also present. citation needed date September 2009 div class metadata plainlinks stub style clear both background transparent This article is a Wikipedia Stub stub . You can help Wikipedia by fullurl FULLPAGENAME action edit expanding it . div Category Endoderm Category Histology cs Stomochord ... more details
In the Embryogenesis development of Vertebrate vertebrate animals , the prechordal plate is a uniquely thickened portion of the endoderm that is in contact with ectoderm immediately Anatomical terms of location Directional terms rostral to the cephalic tip of the notochord . ref http www.mondofacto.com facts dictionary?prechordal plate Mondofacto Online Medical Dictionary ref It is the most likely origin of the rostral cranial mesoderm. ref Seifert, R et al. J Anat 1993 183 75 89 ref References Reflist Category Developmental biology ... more details
Infobox Embryology Name PAGENAME Latin discus embryonicus GraySubject 6 GrayPage 47 Image Gray11.png Caption Section through embryonic disk of Vespertilio murinus . Image2 Gray13.png Caption2 Surface view of embryo of a rabbit . After K lliker. arg. Embryonic disk. pr. Primitive streak . System CarnegieStage 4 Days Precursor GivesRiseTo MeshName MeshNumber Code Terminologia Embryologica TE E2.0.1.2.0.0.14 The floor of the amniotic cavity is formed by the embryonic disk or embryonic disc composed of a layer of prismatic cells, the embryonic ectoderm , derived from the inner cell mass and lying in apposition with the endoderm . In humans, it is the stage of development that occurs after implantation and prior to the embryonic folding eg. seen between about day 14 to day 21 post fertilization . It is derived from the epiblast layer, which lies between the hypoblast layer and the amnion . The epiblast layer is derived from the inner cell mass . Through the process of gastrulation , the bilaminar embryonic disc becomes trilaminar. The notochord forms thereafter. Through the process of neurulation , the notochord induces the formation of the neural tube in the embryonic disc. External links MUNAnatomy embryo emb2 http personalpages.manchester.ac.uk staff j.gough lectures the cell diffdev1 page11.html Diagram at manchester.ac.uk developmental biology stub Gray s Embryology Category Embryology fi Alkiolevy ... more details
Taxobox name Branchiostomidae image Branchiostoma lanceolatum.jpg image width 220px image caption Branchiostoma lanceolotum regnum Animal ia phylum Chordate Chordata subphylum Cephalochordata classis Leptocardii ordo Lancelet Amphioxiformes familia Branchiostomidae familia authority Branchiostomidae syn Branchiostomatidae is the family that includes most of the lancelet s, which are tiny chordate s without a true vertebral column spine but only a flexible notochord . Almost all lancelets belong to Branchiostoma , the one and only genus in the family Branchiostomidae. The genus was originally going to be called Amphioxus but was later changed to its current name. References http www.encyclopedia.com topic lancelet.aspx Category Chordates de Lanzettfischchen fr Branchiostomatidae pt Branchiostoma ... more details
Infobox Anatomy Name PAGENAME Latin GraySubject 17 GrayPage 82 Image Cervical vertebra english.png Caption Cervical vertebra with intervertebral disc. Nucleus pulposus labeled at center right, and is visible at center in light blue. Image2 Disc Herniation.JPG Caption2 Stages of Spinal Disc Herniation System Precursor notochord MeshName MeshNumber DorlandsPre p 41 DorlandsSuf 12679426 Nucleus pulposus is the jelly like substance in the middle of the spinal disc . It is the remnant of the notochord ref cite journal last McCann first Matthew coauthors Owen J. Tamplin, Janet Rossant and Cheryle A. S guin title Tracing notochord derived cells using a Noto cre mouse implications for intervertebral disc developmen journal Disease Models & Mechanisms date 25 year 2011 month 10 doi 10.1242 dmm.008128 url http dmm.biologists.org content early 2011 11 01 dmm.008128.long ref . It functions to distribute hydraulic pressure in all directions within each Annulus fibrosus disci intervertebralis disc under compressive loads. The nucleus pulposus consists of chondrocyte like cells, collagen fibrils, and proteoglycan aggrecan s that aggregate through Hyaluronan hyaluronic chain s. Attached to each aggrecan molecule are the glycosaminoglycan GAG chains of chondroitin sulfate and keratan sulfate . ref See Figure 1 in US patent application 2007 0003525. ref Aggrecan is negatively charged and hydrophilic. This property allows it to draw water into the Nucleus Pulposus. See also Annulus fibrosus disci intervertebralis Spinal disc herniation Additional images gallery Image Gray66.png Sagittal section through an intervertebral fibrocartilage and adjacent parts of two vertebr of an advanced sheep s embryo. gallery References ref http www.google.com patents?id csSXAAAAEBAJ&printsec abstract&zoom 4&dq 2007 0003525 PPA2,M1 Link to referenced patent application. ref references External links http www.spinesource.com images Anatomy3.jpg Image at spinesource.com http www.campoly.com documents pres ... more details
Unreferenced date December 2009 The dorsal nerve cord is one of the embryonic features unique to chordate s, along with a notochord , a post anal tail and pharyngeal slit s. The dorsal nerve cord is a hollow cord dorsal to the notochord.It is formed from a part of the germ layer Ectoderm ectoderm that rolls, forming the hollow tube, compared to other animal phyla, which have solid, ventral tubes. The dorsal nerve cord is later modified into the brain and spinal cord. Dorsal nerve cord is mainly found in phylum Vertebrata. Dorsal means the back side, as opposed to the belly side ventral . See also ventral nerve cord in arthropod s nerve net in cnidaria and echinodermata phyla DEFAULTSORT Dorsal Nerve Cord Category Embryology of nervous system Category Chordates Category Animal anatomy no Det dorsale nervesystemet ... more details
Infobox Anatomy Name Ligament of apex dentis Latin ligamentum apicis dentis GraySubject 74 GrayPage 296 Image gray308.png Caption Median sagittal section through the occipital bone and first three cervical vertebr . Apical odont. lig. labeled at center left. Image2 Caption2 System MeshName MeshNumber DorlandsPre l 09 DorlandsSuf 12491621 In the triangular interval between the alar ligaments is another fibrous cord, the ligament of apex dentis or apical odontoid ligament , which extends from the tip of the odontoid process to the anterior margin of the foramen magnum , being intimately blended with the deep portion of the anterior atlanto ccipital membrane and superior crus of the transverse ligament of the Atlas anatomy atlas . It is regarded as a rudimentary intervertebral fibrocartilage , and in it traces of the notochord may persist. External links RocheLexicon 25420.000 1 Gray s Joints of torso ligament stub Category Ligaments of the head and neck Category Vertebral column ... more details
Infobox Embryology Name PAGENAME Latin GraySubject GrayPage Image Gray14.png Caption Surface view of embryo of Hylobates concolor. The amnion has been opened to expose the embryonic disk. Primitive pit not labeled, but region is visible. Image2 Caption2 System CarnegieStage Days Precursor GivesRiseTo MeshName MeshNumber DorlandsPre DorlandsSuf The primitive pit is a depression in the center of the primitive node , connecting to the notochord . It consists of part of the primitive streak . External links http www.embryology.ch anglais hdisqueembry triderm01.html http isc.temple.edu marino embryology EMBII97 img020.GIF http cancerweb.ncl.ac.uk cgi bin omd?primitive pit http embryology.med.unsw.edu.au Medicine BGDlab3 11.htm http www.ana.ed.ac.uk database humat notes embryo ectoderm primstr.htm Gray s Anatomy stub Embryology Category Developmental biology ... more details
Unreferenced stub auto yes date December 2009 Image Swordfish skeleton.jpg thumb 200px Endoskeleton of a swordfish An endoskeleton is an internal support structure of an animal , composed of mineralized tissues mineralized tissue . Endoskeleton develops within the skin or in the deeper body tissues. The vertebrate is basically an endoskeleton made up of two types of tissues bone and cartilage . During early embryonic development the endoskeleton is composed of notochord and cartilage . The notochord in most vertebrates is replaced by vertebral column and cartilage is replaced by bone in most adults.In three phylum phyla and one Class biology subclass of animals, endoskeletons of various complexity are found Chordata , Echinoderm ata, Porifera , and Coleoidea . An endoskeleton may function purely for support as in the case of Porifera sponges , but often serves as an attachment site for muscle and a mechanism for transmitting muscular forces. A true endoskeleton is derived from germ layer Mesoderm mesodermal tissue. Such a skeleton is present in echinoderms and chordates. The poriferan skeleton consists of microscopic calcareous or siliceous spicule s or a spongin network. The Coleoidae do not have a true endoskeleton in the evolutionary sense here, a mollusc exoskeleton evolution evolved into several sorts of internal structure, the cuttlebone of cuttlefish being the best known version. Yet they do have cartilaginous tissue in their body, even if it is not mineralized, especially in the head, where it forms a primitive cranium.The endoskeleton gives shape,support and protection to the body and provides a mean of locomotion. See also Exoskeleton Hydrostatic skeleton Category Animal anatomy Category Biomechanics Category Skeletal system Category Zoology Veterinary med stub animal anatomy stub de Endoskelett es Endoesqueleto fr Endosquelette hr Unutra nji kostur ht Andosk l t ja pl Szkielet wewn trzny pt Endosqueleto ru simple Endoskeleton uk ... more details
Taxobox name Cephalochordata image Branchiostoma lanceolatum.jpg image caption A Branchiostoma lanceolatum lancelet regnum Animal ia phylum Chordate Chordata subphylum Cephalochordata subphylum authority Richard Owen Owen , 1846 Cephalochordata from Greek language Greek kephal , head and khord , chord is a chordate subphylum defined by the presence of a notochord that persists throughout life. It is represented in the modern oceans by the lancelet s also known as Amphioxus . The characteristics of Cephalochordata are that they are marine animals, segmented, and that they possess elongated bodies with a notochord that extends the length of the body and cirri surrounding the mouth for obtaining food. ref K.M. Van De Graaff and J.L. Crawley, A Photographic Atlas for the Zoology Laboratory , ref . The members of this phylum are very small and have no hard parts, making their fossils difficult to find. Fossilized species have been found in very old rocks predating vertebrates. There is famous shale fossil from the Middle Cambrian Burgess Shale of British Columbia, which has yielded Pikaia fossils. Recently a different cephalochordate fossil Yunnanozoon has been found in south China. It dates to the early Cambrian period and is the earliest known fossil of the cephalochordate lineage ref Chen, J. Y., Dzik, J., Edgecombe, G.D., Ramsk ld, L., and Zhou, G. Q. 1995. A possible Early Cambrian chordate Nature 377 720 722. ref . They have numerous gill slits, and have separate sexes. A well known example is the lancelet . References Reflist chordate stub Category Chordates az Ba xordal lar bs Bezlobanjci ca Cefalocordat cs Bezlebe n de Sch dellose et S stikkalad es Cephalochordata eo Brankiostomulo eu Anfioxo fr Cephalochordata ga Cephalochordata ko hr Svitkoglavci id Cephalochordata it Cephalochordata kk la Cephalochordata lt Bekaukoliai lij Cephalochordata hu Fejgerinch rosok nl Schedellozen ja no Lansettfisker oc Cephalochordata pl Bez ... more details
Unreferenced stub auto yes date December 2009 A Neurula is an embryo at the early stage of development in which neurulation occurs. Neurulation is the development of the nervous system in the vertebrates , at the thickened area above the notochord in ectoderms . The neural plate will fold to produce the neural tube which will develop into the brain . Remaining tissue will develop into the spinal cord . Neurula involves the formation of an internal neural tube from an external sheet of cells. The first signs of neurulation are flattening and thickening of the ectoderm overlying the notochord this thickened area forms a neural plate. The edges of the neural plate that run in an anterior posterior direction continue to thicken, forming ridges or folds. Between these neural folds, a groove forms and deepens as the fold roll over it to converge on the midline. The fold fuses, forming a cylinder the neural tube and a continuous overlying layer of epidermal ectoderm. The neural tube develops bulges at the anterior end, which become the major divisions of the brain. The remaining sections of the tube becomes the spinal cord. Health In humans, failure of the neural tube to develop normally can result in serious birth defects. If the neural folds fail to fuse in a posterior region, the result is a condition known as spina bifida . If they fail to fuse at the anterior end of an infant can develop without a forebrain a condition called anencephaly . There are genetic as well as dietary factors that cause neural tube defects. The incidence of neural tube defects used to be about 1 in 300 live births, but we now know that this incidence can be cut in half if pregnant women have an adequate amount of folic acid in their diets. Development of nervous system Category Embryology of nervous system Developmental biology stub de Neurula es N urula ka oc Neurula ru uk ... more details
dablink This article is about the structure in the developing nervous system . For other uses of the term, see Basal plate . Infobox Embryology Name Basal plate Latin lamina ventrolateralis lamina basalis GraySubject 184 GrayPage 735 Image Gray646.png Caption Diagram to illustrate the alar and basal lamin of brain vesicles. Image2 Gray642.png Caption2 The basal plate basal lamina is separated from the alar plate alar lamina by the sulcus limitans unlabeled . System Nervous system CarnegieStage Precursor Neural tube GivesRiseTo Lower motor neuron s, interneuron s MeshName MeshNumber Code Terminologia Embryologica TE E5.14.1.0.1.0.6 In the developing nervous system , the basal plate is the region of the neural tube ventral to the sulcus limitans . It extends from the rostral mesencephalon to the end of the spinal cord and contains primarily motor neuron s, whereas neurons found in the alar plate are primarily associated with sensory functions. The cell types of the basal plate include lower motor neuron s and four types of interneuron . ref name carlson cite book author Bruce M. Carlson title Human Embryology and Developmental Biology publisher Mosby location Saint Louis, MO year 2004 edition 2nd edition isbn 0 323 03649 X ref Initially the left and right sides of the basal plate are continuous, but during neurulation they become separated by the floor plate , a derivative of the notochord . Differentiation of neurons in the basal plate is under the influence of the protein Sonic hedgehog released by ventralizing structures such as the notochord and floor plate ref name carlson . References references Bibliography cite book author John A. Kiernan title Barr s the Human Nervous System An Anatomical Viewpoint publisher Lippincott Williams & Wilkins location Hagerstown, MD year 2005 edition 8th edition isbn 0 7817 5154 3 External links http isc.temple.edu neuroanatomy lab embryo new spcd 2 Overview at temple.edu BrainInfo ancil 451 Development of nervous system Category ... more details
Taxobox regnum Animal ia phylum Echinodermata classis Homalozoa subclassis Stylophora ordo Cornuta familia Cothurnocystidae subfamilia Cothurnocystinae genus Cothurnocystis genus authority Bather, 1913 species C. fellinensis Ubachs 1969 br C. elizae binomial binomial authority Cothurnocystis along with all of its relatives in Stylophora , are enigmatic organisms whose relationship with other organisms, namely the Echinodermata and the Chordata , are in a state of flux. It was boot shaped and has been suspected to have contained a primitive notochord . Some scientists consider the Stylophora to be a group of primitive chordates, calling them the Calcichordata . The notochord would have been in the tail and was very basic in its structure. The most common hypothesis is that it was related to echinoderm s, as the structure of the test biology test were similar in structure and material to echinoderms. In the top of the boot where a foot would go seems to be the feeding apparatus, with the anus opposite, but the study of these species is vague. References D.Lambert, D.Naish and E.Wyse 2001, Encyclopedia of Dinosaurs and prehistoric life , p.32, Dorling Kindersley Limited, London. ISBN 0 7513 0955 9 External links http www.geo tools.com fossils.htm Fossil Gallery http www.palaeos.com Invertebrates Deuterostomia Homalozoa Stylophora.html Stylophora from palaeos http www.fmnh.helsinki.fi users haaramo Metazoa Deuterostoma Homalozoa.htm Markkos taxonomy http www.ayrshirehistory.org.uk girvangeologists Cothurnocystis.gif image http www.geo tools.com Images Gallery Fossil Big 041.jpg image http www.webcitation.org query?url http www.geocities.com arturordoviciano ordser2 arquivos image007.jpg&date 2009 10 26 04 13 47 image Category Echinoderms Category Prehistoric invertebrates portal Paleontology paleo echinoderm stub ja ... more details
The chondrocranium or cartilaginous neurocranium is the primitive cartilage cartilaginous skeleton skeletal structure of the fetal skull that grows to envelop the rapidly growing embryo embryonic brain . ref name Salentijn Salentijn, L. Biology of Mineralized Tissues Prenatal Skull Development , Columbia University College of Dental Medicine post graduate dental lecture series, 2007 ref In human s, the chondrocranium begins forming at 28 days from mesenchyme mesenchymal condensations and is fully formed between week 7 and 9 of fetal development. While the majority of the chondrocranium is succeeded by the bony skull in most higher vertebrates , some components do persist into adulthood. ref name Salentijn In Chondrichthyes cartilaginous fishes e.g. shark s and Batoidea rays and agnatha ns e.g. lamprey s and hagfish , the chondrocranium persists throughout life. ref Kent, G.C & Miller, L. 1997 Comparative Anatomy of the Vertebrates. Wm. C. Brown Publishers. ISBN 0 697 24378 8. ref Embryology Embryologically , the chondrocranium represents the basal cranial structure, and lays the base for the formation of the endocranium in higher vertebrates. ref name VB cite book author Romer, Alfred Sherwood author2 Parsons, Thomas S. year 1977 title The Vertebrate Body publisher Holt Saunders International location Philadelphia, PA pages 216 247 isbn 0 03 910284 X ref Divisions The portion of the chondrocranium that is associated with the notochord is termed the chordal chondrocranium and is formed from mesoderm ally derived mesenchyme . The more Anatomical terms of location Directional terms rostral portion of the chondrocranium that lie anterior to the notochord constitutes the prechordal chondrocranium, and is derived primarily from neural crest derived mesenchyme. ref name Salentijn See also Dermal bone References Reflist Category Developmental biology Category Skull musculoskeletal stub es Condrocr neo ... more details
About the embryonic artery the artery in adult fish Aorta In other animals Infobox Embryology Name Dorsal aortae Latin aortae dorsales GraySubject 135 GrayPage 506 Image Gray459.png Caption Human embryo of about fourteen days, with yolk sac . Dorsal aorta labeled twice at left. Image2 Gray472.png Caption Profile view of a human embryo estimated at twenty or twenty one days old. Dorsal aorta labeled at center left. System CarnegieStage 9 Precursor GivesRiseTo MeshName MeshNumber Code Terminologia Embryologica TE E5.11.2.1.3.0.1 Each primitive aorta receives anteriorly a vein the vitelline vein from the yolk sac , and is prolonged backward on the lateral aspect of the notochord under the name of the dorsal aorta . The dorsal aort give branches to the yolk sac, and are continued backward through the body stalk as the umbilical arteries to the villi of the chorion . The two dorsal aortae combine to become the descending aorta in later development. External links EmbryologyTemple Heart98 heart97a sld017 EmbryologyUNSW Notes git EmbryologyUNC cardev 009 Development of circulatory system Category Embryology of cardiovascular system ... more details
Infobox Embryology Name PAGENAME Latin flexura mesencephalica GraySubject 184 GrayPage 737 Image Gray651.png Caption Brain of human embryo of four and a half weeks, showing interior of fore brain. Cephalic flexure visible at center top. Image2 Caption2 System CarnegieStage Days Precursor GivesRiseTo MeshName MeshNumber Code Terminologia Embryologica TE E5.14.3.3.0.0.3 The mesencephalic flexure or cephalic flexure is the first flexure, or bend, of the embryo nic brain it appears in the region of the mid brain . In human embryos it generally occurs at the end of the 3rd week beginning of 4th. By means of it the fore brain is bent in a ventral direction around the anterior end of the notochord and fore gut , with the result that the floor of the fore brain comes to lie almost parallel with that of the hind brain . This flexure causes the mid brain to become, for a time, the most prominent part of the brain, since its dorsal surface corresponds with the convexity of the curve. As a consequence, the cardiac plate, which was previously anterior to the forebrain, approximates its adult location in what will become the thoracic region. External links EmbryologyUNSW wwwpig pigg G7L http www.ncbi.nlm.nih.gov books bv.fcgi?db Books&rid neurosci.section.1465 Overview at nlm.nih.gov online book http www.ncbi.nlm.nih.gov books bv.fcgi?rid .0HWDG3XbkpBiO1Yd2dtt5ezWvcwAcNF6XNaS115T Diagram at nlm.nih.gov online book developmental biology stub neuroanatomy stub Gray s Development of nervous system Category Neuroanatomy Category Embryology of nervous system ... more details
File Tetrapod vertebrae.svg thumb right 450px Diagram showing different types of tetrapod vertebrae, with rhachitomes in blue area at left. The Rachitomi were a group of extinct Palaeozoic labyrinthodont amphibian s, according to an earlier classification system. ref name Kent & Miller Kent, G.C. & Miller, L. 1997 Comparative anatomy of the vertebrates. 8th edition. Wm. C. Brown Publishers. Dubuque. 487 pages. ISBN 0 697 24378 8 ref They are defined by the structure of the vertebrae , having large, semi circular intercentrum intercentra below the notochord and smaller paired, though prominent pleurocantrum pleurocentra on each side above and behind, forming anchoring pints for the rib s. ref name Kent & Miller This form of complex backbone was found in some crossopterygii crossopterygian fish , the Ichthyostegalia , most Temnospondyli and some Reptiliomorpha . Primitive reptiles retained the complex rachiotomous vertebrae, though with the pleurocentra being the more dominant structures. As a phylogeny phylogentic unit, the Rachitomi thus form a Paraphyly paraphyletic unit . ref name Romer & Parson Alfred Romer Romer, A.S . & Parsons, T.S. 1985 The Vertebrate Body. 6th ed. Saunders, Philadelphia. ref References Reflist Category Prehistoric amphibians paleo amphibian stub ... more details
Taxobox fossil range Fossil range Chengjiang regnum Animalia phylum Chordata subphylum Cephalochordata genus Cathaymyrus subdivision ranks Species subdivision C. diadexus br C. haikoensis Cathaymyrus is an Early Cambrian cephalochordate known from the Chengjiang locality in Yunnan Province, China. ref cite journal author Shu, D G. year 1999 doi 10.1038 46965 journal Nature volume 402 pages 42 last2 Luo first2 H L. last3 Conway Morris first3 S. last4 Zhang first4 X L. last5 Hu first5 S X. last6 Chen first6 L. last7 Han first7 J. last8 Zhu first8 M. last9 Li first9 Y. issue 6757 bibcode 1999Natur.402...42S ref It had a long segmented body with no distinctive head. The segments resemble the v shaped muscle blocks found in similar cephalochordates such as Amphioxus . A long linear impression runs along the back of the body looking something like a chordate notochord . Cathaymyrus is related to Pikaia , another cephalochordate from the Burgess Shale . See also Maotianshan shales Haikouichthys Myllokunmingia References reflist Category Cambrian animals Category Maotianshan shales fossils cs Cathaymyrus pl Cathaymyrus ... more details
of an elongate notochord , dorsal nerve cord and blocks of muscles down either side of the body all critical features for the evolution of the vertebrates . The notochord is a flexible rod that runs ... to side by the muscle blocks for swimming. In the fish and all subsequent vertebrates, the notochord ... was familiar to biologists long before the Pikaia fossil was discovered. With notochord and paired ... worms and graptolite , are more primitive. Called the hemichordates , they have only a notochord ... more details
. First, floor plate differentiation may be mediated by inductive signaling from the underlying notochord ... concentration localized in the notochord and floor plate. In vitro tissue grafting experiments ... Nervous System Polarizing Activity of the Floor Plate and Notochord. Cell, Vol. 64, 635 ... as well as genetic interaction experiments in zebrafish, it appears that notochord and floor plate ... , extended contact and interaction between notochord and fated floor plate cells causes differentiation ... more details
, when the notochord is ablated during somitogenesis in the chick embryo, the proper number ... signal produced by the notochord is mediated by Shh. Although expression of Shh pathway proteins ... more details
January 2011 The notochord plays an integral role in the development of the neural tube. Prior to neurulation ... of the neural tube. The notochord plate separates and forms the solid notochord. cn date January ... tube showing the floor plate and roof plate After Sonic hedgehog SHH from the notochord induces ... the neural tube. The notochord expresses Sonic Hedgehog Shh . The floor plate responds to Shh by producing ... out. cn date January 2011 Non neural ectoderm tissue Mesoderm surrounding the notochord at the sides ... more details
Encyclopedia
top
