Factbites
 Where results make sense
About us   |   Why use us?   |   Reviews   |   PR   |   Contact us  

Topic: Craniates


  
  Craniata
The craniates are characterized by a skull; that is, a complex ensemble of skeletal elements which surrounds the brain and sensory capsules.
Craniates possess a unique embryonic tissue, the neural crest, that appears dorsal and lateral to the neural tube and which contributes to a great variety of adult tissues and structures including: sensory neurons (nerve cells), some skeletal and connective tissues in the skull, and some pigment containing cells and other integumentary tissues.
As chordates, all craniates develop a notochord, which is primitively large (hagfishes, lampreys), but becomes transitory in most vertebrates and is replaced by elements of the vertebral column, the centra and arcualia.
tolweb.org /tree?group=Craniata&contgroup=Chordata   (2764 words)

  
  Vertebrata - LoveToKnow 1911
Closer investigation of the anatomy and embryology of the craniate vertebrates showed that the possession of a jointed vertebral column was not a fundamental characteristic of the group.
The embryonic Craniate brain appears as three dilatations of the neural tube, respectively the posterior or hind-brain, continuous with the spinal cord, the mid-brain and the fore-brain.
The Cyclostomes, although true Craniates, present an obviously simpler type of structure: the head is less cephalized and therefore less distinct from the trunk; lower jaw, true teeth and dermal armature are absent, whilst there are other simplifications in the structural type.
www.1911encyclopedia.org /V/VE/VERTEBRATA.htm   (3868 words)

  
 Chordata
These fossils are highly significant because they imply the contemporary existence of the tunicates and craniates in the Early Cambrian during the so-called Cambrian Explosion of animal life.
Adults of most members are sessile filter feeders with an expanded pharynx and, like cephalochordates and larval lampreys, with an endostyle, a mucous food trap in the pharyngeal floor that is homologous with the thyroid gland of vertebrates.
Among the living chordates there is little doubt that lancelets are most closely related to the Craniates based on synapomorphies such as segmented axial muscles and metameric organization of the visceral (pharyngeal) arches.
tolweb.org /Chordata/2499   (1676 words)

  
 Cofrin Center for Biodiversity
All craniates are bilaterally symetrical and have a well-developed coelom, a body cavity, derived from the middle layer of embryonic tissues.
The simplest craniate animals are jaw-less fishes with cartilage skeletons.
The first craniates were jawless fishes and are first observed in the fossil record about 480 million years ago.
www.uwgb.edu /biodiversity/biota/craniata.htm   (158 words)

  
 Fossil sister group of craniates: predicted and found.
Although it is the sister group of craniates, Haikouella is skull-less and lacks an ear, but it does have neural-crest derivatives in its branchial bars.
Its craniate characters occur mostly in the head and pharynx; its widely spaced, robust branchial bars indicate it ventilated with branchiomeric muscles, not cilia.
Despite its craniate mode of ventilation, Haikouella was not a predator but a suspension feeder, as shown by its cephalochordate-like endostyle, and tentacles forming a screen across the mouth.
www.medscape.com /medline/abstract/12905532   (368 words)

  
 [No title]
Within each of the major craniate radiations (i.e., jawless fishes, chondrichthyans, actinopterygians, and sarcopterygians) early species in the radiation retain cerebral hemispheres in which the cell bodies of the neurons have not migrated far from their embryonic position close to the ventricle (Fig.
The sensory neurons from receptors for tactile discrimination on the trunk and limbs, and from proprioceptors, are an exception to this generalization because they ascend in the dorsal funiculi of the spinal cord all the way to the cuneate and gracile nuclei in the medulla.
The corticobulbar fibers decussate and terminate in the motor nuclei of cranial nerves, but the corticospinal fibers form the pyramids (which can be seen on the ventral surface of the medulla), decussate, and continue to the motor horns of the spinal cord.
www.bio.umass.edu /biology/bemis/FAOV4/Ch14.doc   (14480 words)

  
 Fred Heeren, Science Journalist
But a problem develops for creationists when their young people start using it to evaluate claims from their preachers, such as “There is no evidence that primitive hominids ever existed.” Young people equipped with PADs find themselves looking at a sequence of hominid skulls with increasing cranial capacities over time.
Chinese fossil discoveries of the earliest known craniates (from the early Cambrian period) have led scientists to question whether the evolution of human-level cognition is a rare occurrence in the universe.
The new evidence for early craniates lends support to the view that human-level cognition may be part of a developmental package, but historical contingencies pose serious problems for a strictly law-like explanation.
www.fredheeren.com   (1118 words)

  
 Craniata   (Site not responding. Last check: )
Remember all essays, cladograms, etc. are my, an armchair amateur's, opinions.They should not be taken as current scientific theory, although I do try to follow either the currently most widely accepted theory or the theory that makes the most sence to me, and certainly don't take them as fact.
The diagnostic feature of craniates is a skull, a series of cartilagenous or bony elements around the brain.
Craniates appeared at least 480Ma, during the Ordovician Period, a division of the Paleozoic Era.
homepage.mac.com /pfhreak/paleontology/clade/C/craniata.html   (160 words)

  
 Craniata - Wikipedia, the free encyclopedia
In this case Craniata might now be superfluous as a separate clade.
Craniates have skulls, like this pygmy hippopotamus skull
This page was last modified 20:47, 8 November 2006.
en.wikipedia.org /wiki/Craniata   (98 words)

  
 Highlights in the Evolution of Vertebrates
The term gnathostome is generally reserved to mean the jawed fishes, though we should not lose sight of the fact that, from a phylogenetic perspective, the gnathostomes include all the jawed craniates, specifically the tetrapods.
From a cladistic point of view, the jawed fishes are a paraphyletic group as opposed to a true clade; a pure cladist would not recognised the jawed fishes as a ‘natural’ group at all.
Critical research by Professor D. Watson at the University of London on the acanthodian placoderm, -Acanthodes, together with studies on the embryology of living fishes and the arrangement of the cranial nerves, indicates that some of the ostracoderm gill arches were lost in the evolution toward higher fish.
www.peripatus.gen.nz /Paleontology/HigEvoVer.html   (11546 words)

  
 Abstracts 49(1)
Second, modern cell and molecular biology are providing a better understanding of the many developmental processes involved in a structure's formation and will augment the number of characters available for phylogenetic analyses.
Recent work has revealed that what had been thought to be a highly conserved developmental stage, the pharyngula, the phylotypic and zootypic stage of craniates, is highly variable.
These tissues are particularly interesting from a phylogenetic standpoint because they and the structures they form contribute to key synapomorphies of craniates.
ag.arizona.edu /systbiol/SSBWeb/issues/49_1/abstracts49_1.html   (1868 words)

  
 Brain - Wikipedia, the free encyclopedia
The brain innervates the head through cranial nerves, and it communicates with the spinal cord, which innervates the body through spinal nerves.
In Egypt, from the late Middle Kingdom onwards, in preparation for mummification, the brain was regularly removed, for it was the heart that was assumed to be the seat of intelligence.
Anatomically, the majority of afferent and efferent nerves (with the exception of the cranial nerves) are connected to the spinal cord, which then transfers the signals to and from the brain.
en.wikipedia.org /wiki/Brain   (4119 words)

  
 Vertebrate Evolution - Fish
The craniates, also known as the vertebrates, have particular specialization in the region of the head, thus the name "craniata".
Well, one theory for origin of the craniates is that they were formed by phaedomorphosis, the retention of juvenile characteristics by adults.
The agnathans, jawless vertebrates, are the earliest known craniates.
www.bio.miami.edu /tom/bil160/bil160goods/19_verts1.html   (2256 words)

  
 Palaeos Vertebrates 20.000  Craniata
Characters: Neural crest cells, somites, gills with cartilagenous or bone supports (absent in Myllokunmingia?), tripartite brain and paired cranial sense organs, cranium with anterior notochord, semi-circular canal(s), 1 heart, kidneys.
(1999) of Myllokunmingia from the Lower Cambrian of South China is generally what one might have expected of a very primitive craniate.
Perhaps it is better treated as a pre-vertebrate craniate since, as Shu states, it is not part of the crown group vertebrates, defined as the LCA of lampreys and gnathostomes.
www.palaeos.com /Vertebrates/Units/020Craniata/100.html   (970 words)

  
 Lecture 3 - chordate origins
Urochordates - tunicates or "sea squirts", salps, etc. Notice that the larvae of sea squirts are motile but the adults are sessile.
This is a phylogeny based on 18S rDNA from Wada (1998), which suggests that the ancestor of euchordates (Branchiostoma + craniates) was pelagic and had a tadpole-like body morphology throughout its life history.
hagfish have traditionally been classified as vertebrates but should properly be classified with vertebrates as craniates.
www.usm.maine.edu /bio/courses/bio205/bio205_03_vertebrate_orgins.html   (1477 words)

  
 A possible Early Cambrian chordate
Segmented musculature and metameric branchial arches are shared with cephalochordates and craniates.
Yunnanozoon expands the range of cephalochordate morphology known from the younger Pikaia gracilens and crown group forms such as amphioxus.
Our identification predicts that other chordate clades (tunicates and craniates) had evolved by the Late Atdabanian, in the main burst of the Cambrian Explosion.
www.nature.com /doifinder/10.1038/377720a0   (336 words)

  
 Ch. 34
craniates are more active, have higher metabolism and much more extensive musculature,
craniate hearts have at least 2 chambers, rbcs and hemoglobin, and kidneys
Explain the fate of the neural crest cells in craniate development.
www.ltcconline.net /kloss/bio103/ch__34.htm   (1558 words)

  
 Untitled Document   (Site not responding. Last check: )
List and briefly describe 2 subphyla of animals that are considered chordates but NOT craniates or vertebrates.
List and briefly describe one class or organisms that are considered to be craniates but NOT a true chordate.
List and briefly describe one class of organisms that are considered to be true vertebrates but are agnathans.
www.tarleton.edu /~kmurray/SG34.html   (376 words)

  
 Craniates
Relationships between the chordate subphyla are hazy, but some molecular data suggests that the Craniata evolved from the early cephalochordates.
The craniates are defined by the cranium (skull), the bony braincase.
Vertebrates, such as humans and dolphins, make up the vast majority of surviving craniates.
www.stanford.edu /~dgentry/dolphin/evolution/deuter3.html   (263 words)

  
 Fred Heeren, Science Journalist
But a problem develops for creationists when their young people start using it to evaluate claims from their preachers, such as “There is no evidence that primitive hominids ever existed.” Young people equipped with PADs find themselves looking at a sequence of hominid skulls with increasing cranial capacities over time.
Chinese fossil discoveries of the earliest known craniates (from the early Cambrian period) have led scientists to question whether the evolution of human-level cognition is a rare occurrence in the universe.
The new evidence for early craniates lends support to the view that human-level cognition may be part of a developmental package, but historical contingencies pose serious problems for a strictly law-like explanation.
www.fredheeren.com /index.html   (1094 words)

  
 Understanding Vertebrate Brain Evolution -- Northcutt 42 (4): 743 -- Integrative and Comparative Biology
Brainstem neurons with descending projections to the spinal cord of two elasmobranch fishes, thornback guitarfish, Platyrhinoidis triserita, and horn shark, Heterodontus francisci.
The brain and cranial nerves of the white shark: An evolutionary perspective.
The forebrain of the Pacific hagfish: A cladistic reconstruction of the ancestral craniate forebrain.
icb.oxfordjournals.org /cgi/content/full/42/4/743   (7310 words)

  
 GEOL 331 Lectures 35-36: Vertebrate Paleontology
In terms of metabolic rate and aerobic capacity, only cephalopod mollusks and some arthropods are comparable to craniates.
Myxinoidea seem to be basal to all other craniates, living or fossil.
Myxinoids have tentacles, and (at least the living ones) have large ventrolateral slime glands, esophago-cutaneous duct on the left side, and elongate body shape.
www.geol.umd.edu /~tholtz/G331/331verts.htm   (732 words)

  
 Dr. W. Ross Ellington - Research Laboratory
The AK and CK reactions function as temporal and spatial ATP buffers, maintaining the chemical potential for ATP hydrolysis at optimal levels to mitigate temporal and spatial mismatches of ATP supply and demand.
AK is ancient; it is present in key protozoan groups and is widespread throughout the metazoa but is lacking in the craniates (hagfish and vertebrates).
CK is present in a variety of invertebrates and is the exclusive phosphagen kinase in the craniates.
www.bio.fsu.edu /ellington-lab.php   (1079 words)

  
 Sensory system evolution at the origin of craniates.
Sensory system evolution at the origin of craniates.
The multiple events at the transition from non-craniate invertebrate ancestors to craniates included the gain and/or elaboration of migratory neural crest and neurogenic placodes.
These tissues give rise to the peripherally located, bipolar neurons of all non-visual sensory systems.
www.medscape.com /medline/abstract/11079421   (235 words)

  
 The Origin and Early Evolution of the Chordata
Retain ancestral free-swimming "juvenile" form as adults of descendants
Amphioxus/Pikaia are our baselines for understanding the origins of craniates
Transition from "Protochordates" to craniates marked by a dramatic change in …
www.life.umd.edu /classroom/zool210/jensen/2Lectures/lecture20.html   (187 words)

  
 Trace Fossils
Trace fossils, or ichnofossils (from the Greek ikhnos meaning "track" or "trace"), are those structures and details preserved in rocks that provide indirect evidence of life in the past, or indeed "traces" of it.
The most familiar of these are the tracks, trails, burrows, gastroliths, coprolites, impressions, borings, etc., made by invertebrates of all phyla (Pickerill 1994), but craniates, plants, fungi, and bacteria also contribute significantly to their number.
Ichnofossils are found on and within both hard and soft substrates, especially in sandstones or between two contrasting lithologies (Allaby and Allaby 1999).
www.peripatus.gen.nz /Paleontology/TraFos.html   (6316 words)

  
 Arianit Zeka – Schwaba   (Site not responding. Last check: )
The relationships of some of the presumed fossil chordates are based on scant evidence and there is debate about the position of especially the calcichordates and conodonts.
There is strong morphological, especially embryological, evidence for monophyletic of the Urochordata, Cephalochordate and Craniates.
This is what I thought it is more important to mention about Chordates.
www.rit.edu /~mnhsch/treefiles/chordata.htm   (197 words)

  
 Amazon.com: "extant craniates": Key Phrase page
See all pages with references to "extant craniates".
This system, losing its asymmetries, evolved into the acusticolateralis system of extant craniates.
Key Phrases: Royal Society, New York, Academic Press, Zoological Journal of the Linnean Society, Philosophical Transactions, Journal of Vertebrate Paleontology, hypophysial tube, ventral otic fissure, lamellar crown tissue, mitochondrial protein data, chordate stem lineage, extant craniates (see more)
amazon.com /phrase/extant-craniates   (216 words)

  
 Structural Evolution of Otx Genes in Craniates -- Germot et al. 18 (9): 1668 -- Molecular Biology and Evolution
Structural Evolution of Otx Genes in Craniates -- Germot et al.
C-terminal domain, which appears to be a hallmark of all craniate
in craniates all derive from duplications of a single ancestral
mbe.oxfordjournals.org /cgi/content/abstract/18/9/1668   (641 words)

  
 Amazon.com: "fossil jawless craniates": Key Phrase page
See all pages with references to "fossil jawless craniates".
SKULL OF EXCLUSIVELY FOSSIL JAWLESS CRANIATES During the Ordovician, Silurian, and Devonian (i.e., over a period of nearly 120 million years), six jawless craniate groups diversified...
Key Phrases: Journal of Morphology, New York, Academic Press, Journal of Anatomy, Journal of Vertebrate Paleontology, University of Kansas, labeling see list, hypophysial tube, lamina obturans, neural crest hypothesis, dermal palate, fossil jawless craniates (see more)
amazon.com /phrase/fossil-jawless-craniates   (172 words)

Try your search on: Qwika (all wikis)

Factbites
  About us   |   Why use us?   |   Reviews   |   Press   |   Contact us  
Copyright © 2005-2007 www.factbites.com Usage implies agreement with terms.