Rôle des cellules mésectodermiques issues des crêtes neurales céphaliques dans la formation des arcs branchiaux et du squelette viscéral

Development ◽  
1974 ◽  
Vol 31 (2) ◽  
pp. 453-477
Author(s):  
C. Le Lievre
Keyword(s):  
Anterior Part ◽  
Branchial Arch ◽  
Interphase Nuclei ◽  
Somite Stage ◽  
Lower Jaw ◽  
Branchial Arches ◽  
Neural Axis ◽  
Aortic Arches ◽  
Cellular Markers ◽  
The Stability

The participation of neural crest cells in the formation of the branchial arches and especially of the hypobranchial skeleton has been studied with heterospecific grafts of quail neural tube into the chick embryo. According to the labelling technique devised by Le Douarin, the differences between quail and chick interphase nuclei make it possible to use quail cells as cellular markers in this system. The excision of the mesencephalo-rhombencephalic primordium of 4- to 12-somite chick embryos results in the atrophy of the branchial arches, and in important deficiencies of the hypobranchial skeleton. Nevertheless, the nearly complete absence of the branchial mesenchyme does not prevent the visceral pouches and clefts from forming. The isotopic and isochronic graft of quail neural primordium into the chick shows that the mesenchymal component of the branchial arches is of neurectodermal origin, except for the muscle plates and the endothelium of the aortic arches, which derive from the mesoderm. The mesencephalic neural crests give rise to the totality of the mesenchyme of the first branchial arch and partially to that of the second one, while the rhombencephalon contributes to the formation of the second, third and fourth arches. The stability of the marker system produced by quail cells implanted into the chick makes it possible to follow the migrating cells until they have reached their definitive localization in the various structures of the hypobranchial skeleton, which thus appears to be entirely of neurectodermal origin. The cells arising from the mesencephalic neural primordium constitute the lower jaw skeleton (Meckel's cartilage and bones) and are all still in the process of migration at the 6-somite stage. Cells originating from the rhombencephalon have left the neural axis at the 9- to 10-somite stage for the anterior part (in front of the first somite) and at the 11- to 12-somite stage for the posterior rhombencephalon. Differentiation of mesectodermal cells into chondrocytes and osteocytes has been observed during the morphogenesis of the visceral skeleton.

Mesenchymal derivatives of the neural crest: analysis of chimaeric quail and chick embryos

Development ◽  
1975 ◽  
Vol 34 (1) ◽  
pp. 125-154
Author(s):  
C. S. Le Lièvre ◽  
N. M. Le Douarin
Keyword(s):  
Neural Crest ◽  
Carotid Arteries ◽  
Secretory Cells ◽  
Chick Embryos ◽  
Digestive Tube ◽  
Enteric Ganglia ◽  
Lower Jaw ◽  
Branchial Arches ◽  
Neural Axis ◽  
Common Carotid Arteries

Interspecific grafts of neural tube and associated neural crest (NC) have been made between quail and chick embryos. Structural differences of the interphase nucleus in the two species make it possible to identify quail from chick cells in the chimaeras after Feulgen—Rossenbeck's staining and at the electron microscope level. Owing to the stability of the natural quail nuclear marker labelling, migration pattern and developmental fate of the grafted NC cells could be followed in the host embryo. In previous work it has been demonstrated that the visceral skeleton derives entirely from NC mesenchyme and the various levels of the neural axis from which visceral cartilages and bones originate have been established. In the present work, the contribution to the lower jaw and pharynx of NC mesenchymal derivatives other than bones and cartilages has been studied. It is shown that the dermis in the face and ventrolateral side of the neck has a neural origin. The wall of the large arteries deriving from the branchial arches (systemic aorta, pulmonary arteries, brachiocephalic trunks and common carotid arteries) are entirely made up of mesectodermal cells except for the endothelial epithelium which is mesodermal in origin. The presence in the wall of the common carotid arteries of fiuorogenic monoamines-containing cells is demonstrated using the formol-induced-fiuorescence technique. Like the secretory cells of the carotid body, the fluorescent cells of the carotid artery wall originate from the rhombencephalic NC. Connective tissue of the lower jaw, tongue and ventrolateral part of the neck originate from the neural crest. Mesectoderm participate in the formation of the glands associated with the tongue and pharynx (lingual gland, thymus, thyroid, parathyroids) giving their mesenchymal component. On the other hand, as demonstrated previously by our group, NC cells are the main cellular component of the UB since they give rise to the calcitoninproducing cells. The wall of the oesophagus and trachea is of mesodermal origin, but adipose tissue around the trachea and parasympathetic enteric ganglia of the digestive tube derives from NC. NC cells participate in the formation of striated muscles of the branchial arches and differentiate there into connective and muscle cells. It appears from this study that the differentiating capabilities are similar in mesenchymal and mesectodermal cells with the exception of blood vessel endothelia which in our experiments are always of host origin in mesectoderm-derived tissues. The capacity of the NC to give rise to mesenchymal derivatives is restricted to the cephalic neural axis down to the level of the 5th somite in both chick and quail embryos.

MyoD and Myf-5 define the specification of musculature of distinct embryonic origin

1998 ◽  
Vol 76 (6) ◽  
pp. 1079-1091 ◽  
Author(s):  
Boris Kablar ◽  
Atsushi Asakura ◽  
Kirsten Krastel ◽  
Chuyan Ying ◽  
Linda L May ◽  
...  
Keyword(s):  
Abdominal Wall ◽  
Expression Pattern ◽  
Branchial Arch ◽  
Precursor Cells ◽  
Mouse Development ◽  
Unique Role ◽  
Branchial Arches ◽  
Embryonic Origin ◽  
Body Wall Muscles ◽  
Myogenic Precursor

Mounting evidence supports the notion that Myf-5 and MyoD play unique roles in the development of epaxial (originating in the dorso-medial half of the somite, e.g. back muscles) and hypaxial (originating in the ventro-lateral half of the somite, e.g. limb and body wall muscles) musculature. To further understand how Myf-5 and MyoD genes co-operate during skeletal muscle specification, we examined and compared the expression pattern of MyoD-lacZ (258/-2.5lacZ and MD6.0-lacZ) transgenes in wild-type, Myf-5, and MyoD mutant embryos. We found that the delayed onset of muscle differentiation in the branchial arches, tongue, limbs, and diaphragm of MyoD-/- embryos was a consequence of a reduced ability of myogenic precursor cells to progress through their normal developmental program and not because of a defect in migration of muscle progenitor cells into these regions. We also found that myogenic precursor cells for back, intercostal, and abdominal wall musculature in Myf-5-/-embryos failed to undergo normal translocation or differentiation. By contrast, the myogenic precursors of intercostal and abdominal wall musculature in MyoD-/- embryos underwent normal translocation but failed to undergo timely differentiation. In conclusion, these observations strongly support the hypothesis that Myf-5 plays a unique role in the development of muscles arising after translocation of epithelial dermamyotome cells along the medial edge of the somite to the subjacent myotome (e.g., back or epaxial muscle) and that MyoD plays a unique role in the development of muscles arising from migratory precursor cells (e.g., limb and branchial arch muscles, tongue, and diaphragm). In addition, the expression pattern of MyoD-lacZ transgenes in the intercostal and abdominal wall muscles of Myf-5-/- and MyoD-/- embryos suggests that appropriate development of these muscles is dependent on both genes and, therefore, these muscles have a dual embryonic origin (epaxial and hypaxial).Key words: epaxial and hypaxial muscle, Myf-5, MyoD, mouse development, somite.

Jaw and branchial arch mutants in zebrafish I: branchial arches

Development ◽  
1996 ◽  
Vol 123 (1) ◽  
pp. 329-344 ◽  
Author(s):  
T.F. Schilling ◽  
T. Piotrowski ◽  
H. Grandel ◽  
M. Brand ◽  
C.P. Heisenberg ◽  
...  
Keyword(s):  
Neural Crest ◽  
Zebrafish Embryo ◽  
Neural Crest Cells ◽  
Branchial Arch ◽  
Pigment Cells ◽  
Pharyngeal Arches ◽  
Pectoral Fins ◽  
Branchial Arches ◽  
Group Members ◽  
The Brain

Jaws and branchial arches together are a basic, segmented feature of the vertebrate head. Seven arches develop in the zebrafish embryo (Danio rerio), derived largely from neural crest cells that form the cartilaginous skeleton. In this and the following paper we describe the phenotypes of 109 arch mutants, focusing here on three classes that affect the posterior pharyngeal arches, including the hyoid and five gill-bearing arches. In lockjaw, the hyoid arch is strongly reduced and subsets of branchial arches do not develop. Mutants of a large second class, designated the flathead group, lack several adjacent branchial arches and their associated cartilages. Five alleles at the flathead locus all lead to larvae that lack arches 4–6. Among 34 other flathead group members complementation tests are incomplete, but at least six unique phenotypes can be distinguished. These all delete continuous stretches of adjacent branchial arches and unpaired cartilages in the ventral midline. Many show cell death in the midbrain, from which some neural crest precursors of the arches originate. lockjaw and a few mutants in the flathead group, including pistachio, affect both jaw cartilage and pigmentation, reflecting essential functions of these genes in at least two neural crest lineages. Mutants of a third class, including boxer, dackel and pincher, affect pectoral fins and axonal trajectories in the brain, as well as the arches. Their skeletal phenotypes suggest that they disrupt cartilage morphogenesis in all arches. Our results suggest that there are sets of genes that: (1) specify neural crest cells in groups of adjacent head segments, and (2) function in common genetic pathways in a variety of tissues including the brain, pectoral fins and pigment cells as well as pharyngeal arches.

The branchial arches and HGF are growth-promoting and chemoattractant for cranial motor axons

Development ◽  
2000 ◽  
Vol 127 (8) ◽  
pp. 1751-1766 ◽  
Author(s):  
A. Caton ◽  
A. Hacker ◽  
A. Naeem ◽  
J. Livet ◽  
F. Maina ◽  
...  
Keyword(s):  
Growth Factor ◽  
Hepatocyte Growth Factor ◽  
Motor Neurons ◽  
Branchial Arch ◽  
Sensory Ganglia ◽  
Motor Axons ◽  
Collagen Gels ◽  
Branchial Arches ◽  
Growth Promoting ◽  
Hepatocyte Growth

During development, cranial motor neurons extend their axons along distinct pathways into the periphery. For example, branchiomotor axons extend dorsally to leave the hindbrain via large dorsal exit points. They then grow in association with sensory ganglia, to their targets, the muscles of the branchial arches. We have investigated the possibility that pathway tissues might secrete diffusible chemorepellents or chemoattractants that guide cranial motor axons, using co-cultures in collagen gels. We found that explants of dorsal neural tube or hindbrain roof plate chemorepelled cranial motor axons, while explants of cranial sensory ganglia were weakly chemoattractive. Explants of branchial arch mesenchyme were strongly growth-promoting and chemoattractive for cranial motor axons. Enhanced and oriented axon outgrowth was also elicited by beads loaded with Hepatocyte Growth Factor (HGF); antibodies to this protein largely blocked the outgrowth and orientation effects of the branchial arch on motor axons. HGF was expressed in the branchial arches, whilst Met, which encodes an HGF receptor, was expressed by subpopulations of cranial motor neurons. Mice with targetted disruptions of HGF or Met showed defects in the navigation of hypoglossal motor axons into the branchial region. Branchial arch tissue may thus act as a target-derived factor that guides motor axons during development. This influence is likely to be mediated partly by Hepatocyte Growth Factor, although a component of branchial arch-mediated growth promotion and chemoattraction was not blocked by anti-HGF antibodies.

Pax3 is required for cardiac neural crest migration in the mouse: evidence from the splotch (Sp2H) mutant

Development ◽  
1997 ◽  
Vol 124 (2) ◽  
pp. 505-514 ◽  
Author(s):  
S.J. Conway ◽  
D.J. Henderson ◽  
A.J. Copp
Keyword(s):  
Neural Crest ◽  
Neural Tube ◽  
Neural Crest Cells ◽  
Outflow Tract ◽  
Avian Embryo ◽  
Cardiac Neural Crest ◽  
Branchial Arches ◽  
Aortic Arches ◽  
Cardiac Outflow

Neural crest cells originating in the occipital region of the avian embryo are known to play a vital role in formation of the septum of the cardiac outflow tract and to contribute cells to the aortic arches, thymus, thyroid and parathyroids. This ‘cardiac’ neural crest sub-population is assumed to exist in mammals, but without direct evidence. In this paper we demonstrate, using RT-PCR and in situ hybridisation, that Pax3 expression can serve as a marker of cardiac neural crest cells in the mouse embryo. Cells of this lineage were traced from the occipital neural tube, via branchial arches 3, 4 and 6, into the aortic sac and aorto-pulmonary outflow tract. Confirmation that these Pax3-positive cells are indeed cardiac neural crest is provided by experiments in which hearts were deprived of a source of colonising neural crest, by organ culture in vitro, with consequent lack of up-regulation of Pax3. Occipital neural crest cell outgrowths in vitro were also shown to express Pax3. Mutation of Pax3, as occurs in the splotch (Sp2H) mouse, results in development of conotruncal heart defects including persistent truncus arteriosus. Homozygotes also exhibit defects of the aortic arches, thymus, thyroid and parathyroids. Pax3-positive neural crest cells were found to emigrate from the occipital neural tube of Sp2H/Sp2H embryos in a relatively normal fashion, but there was a marked deficiency or absence of neural crest cells traversing branchial arches 3, 4 and 6, and entering the cardiac outflow tract. This decreased expression of Pax3 in Sp2H/Sp2H embryos was not due to down-regulation of Pax3 in neural crest cells, as use of independent neural crest markers, Hoxa-3, CrabpI, Prx1, Prx2 and c-met also revealed a deficiency of migrating cardiac neural crest cells in homozygous embryos. This work demonstrates the essential role of the cardiac neural crest in formation of the heart and great vessels in the mouse and, furthermore, shows that Pax3 function is required for the cardiac neural crest to complete its migration to the developing heart.

Fgf-8 determines rostral-caudal polarity in the first branchial arch

Development ◽  
1999 ◽  
Vol 126 (1) ◽  
pp. 51-61 ◽  
Author(s):  
A.S. Tucker ◽  
G. Yamada ◽  
M. Grigoriou ◽  
V. Pachnis ◽  
P.T. Sharpe
Keyword(s):  
Neural Crest ◽  
Branchial Arch ◽  
Cell Fates ◽  
Spatial Expression ◽  
Mandibular Arch ◽  
Endothelin 1 ◽  
Lower Jaw ◽  
Cell Competence ◽  
Mesenchyme Cells

In mammals, rostral ectomesenchyme cells of the mandibular arch give rise to odontogenic cells, while more caudal cells form the distal skeletal elements of the lower jaw. Signals from the epithelium are required for the development of odontogenic and skeletogenic mesenchyme cells. We show that rostral-caudal polarity is first established in mandibular branchial arch ectomesenchymal cells by a signal, Fgf-8, from the rostral epithelium. All neural crest-derived ectomesenchymal cells are equicompetent to respond to Fgf-8. The restriction into rostral (Lhx-7-expressing) and caudal (Gsc-expressing) domains is achieved by cells responding differently according to their proximity to the source of the signal. Once established, spatial expression domains and cell fates are fixed and maintained by Fgf-8 in conjunction with another epithelial signal, endothelin-1, and by positional changes in ectomesenchymal cell competence to respond to the signal.

Hoxa-2 restricts the chondrogenic domain and inhibits bone formation during development of the branchial area

Development ◽  
1998 ◽  
Vol 125 (14) ◽  
pp. 2587-2597 ◽  
Author(s):  
B. Kanzler ◽  
S.J. Kuschert ◽  
Y.H. Liu ◽  
M. Mallo
Keyword(s):  
Bone Formation ◽  
Branchial Arch ◽  
Intramembranous Ossification ◽  
Expression Domain ◽  
Sox9 Expression ◽  
Molecular Analyses ◽  
Early Stages ◽  
Branchial Arches ◽  
Skeletal Formation ◽  
Dermal Bone

In Hoxa-2(−/−)embryos, the normal skeletal elements of the second branchial arch are replaced by a duplicated set of first arch elements. We show here that Hoxa-2 directs proper skeletal formation in the second arch by preventing chondrogenesis and intramembranous ossification. In normal embryos, Hoxa-2 is expressed throughout the second arch mesenchyme, but is excluded from the chondrogenic condensations. In the absence of Hoxa-2, chondrogenesis is activated ectopically within the rostral Hoxa-2 expression domain to form the mutant set of cartilages. In Hoxa-2(−/−)embryos the Sox9 expression domain is shifted into the normal Hoxa-2 domain. Misexpression of Sox9 in this area produces a phenotype resembling that of the Hoxa-2 mutants. These results indicate that Hoxa-2 acts at early stages of the chondrogenic pathway, upstream of Sox9 induction. We also show that Hoxa-2 inhibits dermal bone formation when misexpressed in its precursors. Furthermore, molecular analyses indicate that Cbfa1 is upregulated in the second branchial arches of Hoxa-2 mutant embryos suggesting that prevention of Cbfa1 induction might mediate Hoxa-2 inhibition of dermal bone formation during normal second arch development. The implications of these results on the patterning of the branchial area are discussed.

Embryology of the head and neck

2013 ◽  
Author(s):  
Martin E. Atkinson
Keyword(s):  
Head And Neck ◽  
Neural Tube ◽  
Neck Region ◽  
Branchial Arch ◽  
Paraxial Mesoderm ◽  
Pharyngeal Arches ◽  
Branchial Arches ◽  
Aquatic Vertebrates ◽  
History Of ◽  
Further Development

Embryology and development have been covered after the main anatomical descriptions in the previous sections, but it is going to precede them in this section. The reason for this departure is that the embryonic development of the head and neck explains much of the mature anatomy which can seem illogical without its developmental history. The development of the head, face, and neck is an area of embryology where significant strides in our understanding have been made in the last few years. The development of the head is intimately related to the development of the brain outlined in Chapter 19 and its effects on shaping the head will be described in Chapters 32 and 33. The major thrust of this chapter is the description of the formation of structures called the pharyngeal (or branchial) arches and the fate of the tissues that contribute to them. All four embryonic germ layers contribute to the pharyngeal arches and their derivatives, hence to further development of the head and neck. Figure 21.1 is a cross section through the neck region of a 3-week old embryo after neurulation and folding described in Chapter 8. It shows the structures and tissues that contribute to the formation of the head and neck: • The neural tube situated posteriorly and the ectomesenchymal neural crest cells that arise as the tube closes; • The paraxial mesoderm anterolateral to the neural tube; • The endodermal foregut tube anteriorly; • The investing layer of ectoderm. The development of all these tissues is intimately interrelated. The pharyngeal arches are very ancient structures in the evolutionary history of vertebrates. The arches and their individual components have undergone many modifications during their long history. In ancestral aquatic vertebrates, as in modern fishes, water was drawn in through the mouth and expelled through a series of gill slits (or branchiae, hence the term ‘branchial arch’) in the sides of the pharynx. Oxygen was extracted as the water was passed over a gill apparatus supported by a branchial arch skeleton moved by branchial muscles controlled by branchial nerves. Although ventilation and respiration is now a function of the lungs in land vertebrates, the pharyngeal arches persist during vertebrate development.

scholarly journals An account of the devonian fish, Palæospondylus Gunni , traquair

1904 ◽  
Vol 72 (477-486) ◽  
pp. 98-99
Keyword(s):  
Ventral Surface ◽  
Dorsal Side ◽  
Serial Sections ◽  
Cranial Cavity ◽  
Larval Amphibians ◽  
Lower Jaw ◽  
Branchial Arches ◽  
Vertical Walls

This fossil, which has been variously referred to an alliance with Lampreys, Tadpoles, and Lung-fish, has been successfully studied by means of serial sections. The ventral surface of the head bears four pairs of branchial bars, with the last of which two post-branchial plates, the so-called “post-occipital” plates, are associated; in front of the branchial bars are two pairs of structures, which are regarded as representing the lower jaw and hyoid; they are supported by a suspensory apparatus, which may represent the palato-quadrate and hyo-mandibular elements. The branchial arches are wholly unlike anything seen in Marsipobranchs, but call to mind the similar structures in the Dipnoi and larval Amphibians. The dorsal side of the skull shows a large cranial cavity with thin vertical walls, but no complete roof, a pair of auditory and a pair of nasal capsules.

scholarly journals On the systematic relationships of Cearadactylus atrox, an enigmatic Early Cretaceous pterosaur from the Santana Formation of Brazil

Fossil Record ◽  
2002 ◽  
Vol 5 (1) ◽  
pp. 239-263
Author(s):  
D. M. Unwin
Keyword(s):  
Prey Capture ◽  
Anterior Part ◽  
Cervical Vertebrae ◽  
Valid Species ◽  
Basal Diameter ◽  
Diagnostic Characters ◽  
Lower Jaw ◽  
History Of ◽  
Mandibular Teeth ◽  
Santana Formation

<i>Cearadactylus atrox</i>, a large pterodactyloid pterosaur represented by an incomplete skull and lower jaw from the Lower Cretaceous Santana Formation of Brazil, is a valid species. Diagnostic characters include a mandibular symphysis with a transversely expanded "spatulate" anterior end that is considerably wider than the rostral spatula, and a third rostral tooth that has a basal diameter more than three times that of the fifth tooth. Additional diagnostic characters, contingent upon assignment of <i>Cearadactylus atrox</i> to the Ctenochasmatidae, include: anterior ends of jaws divaricate and containing 7 pairs of rostral teeth and 6 pairs of mandibular teeth; marked dimorphodonty, with an abrupt change in tooth morphology; and a "high check". "<i>Cearadactylus? ligabuei</i>" Dalla Vecchia, 1993, based on an incomplete skull, also from the Santana Formation, is not related to <i>Cearadactylus atrox</i>, exhibits several ornithocheirid synapomorphies and is referred, tentatively, to <i>Anhanguera. Cearadactylus atrox</i> exhibits various synapomorphies of the Ctenochasmatidae (rostrum anterior to nasoantorbital fenestra greater than half total skull length, teeth in anterior part of dentition relatively elongate and pencil-shaped, premaxilla has at least 7 pairs of teeth), the defining synapomorphy of the Gnathosaurinae (rostrum with dorsoventrally compressed laterally expanded spatulate anterior expansion), and shares two synapomorphies with the Chinese gnathosaurine <i>Huanhepterus quingyangensis</i> (anterior tips of jaws divaricate, teeth restricted to anterior half of mandible). Two elongate cervical vertebrae, also from the Santana Formation and previously assigned to "<i>Santanadactylus brasilensis</i>", are tentatively referred to <i>Cearadactylus</i>. Reconstruction of the temporal history of the Ctenochasmatidae suggests that while ctenochasmatines became increasingly specialised for filter feeding, gnathosaurines changed from sieve feeding to piscivory, acquiring several cranial characters that are similar to those of ornithocheirids, a group that also includes large aerial piscivores that used a terminal tooth grab for prey capture. <br><br> Cearadactylus atrox aus der Santana-Formation (Unterkreide, NO-Brasilien) ist eine valide Art. Eine Revision des Taxons, von dem ein unvollständiger Schädel mit Unterkiefer vorliegt, ergab folgende diagnostische (autapomorphe) Merkmale. Die Symphyse hat ein transversal verbreitertes spatelförmiges Vorderende, das deutlich breiter ist als das Schnauzenende. Der dritte rostrale Zahn erreicht einen basalen Durchmesser, der jenen des fünften Zahns um das Dreifache übertrifft. Hinzu kommen Merkmale, die <i>C. atrox</i> mit der Ctenochasmatidae gemein hat, darunter die vorn auseinanderklaffenden Kieferränder, sieben rostrale Zahnpaare, sechs Unterkieferzahnpaare, eine ausgeprägte Dimorphodontie sowie eine hohe Wangenregion. "<i>Cearadactylus ? ligabuei</i>" Dalla Vecchia 1993, ebenfalls mit einem unvollständigen Schädel belegt, ist nicht näher mit <i>C. atrox</i> verwandt. Im Gegensatz zu letzterem zeigt "<i>C. ? ligabuei</i>" signifikante Ähnlichkeiten mit den Ornithocheiridae. Unter Vorbehalt wird er hier der Gattung <i>Anhanguera</i> zugeordnet. <i>C. atrox</i> hat neben eindeutigen Synapomorphien der Ctenochasmatidae, z. B. erreicht das Rostrum anterior des nasoantorbitalen Fensters mehr als die halbe Schädellänge, die vordersten Zähne sind verlängert und stiftförmig und die das Prämaxillare trägt mindestens sieben Zahnpaare. Daneben besitzt <i>C. atrox</i> auch noch die entscheidende Synapomorphie der Gnathosaurinae, nämlich ein Rostrum mit dorsoventral komprimierter vorderem Auswuchs. Außerdem ist <i>C. atrox</i> gekennzeichnet durch zwei Autapomorphien des Gnathosaurinen <i>Huanhepterus quingyangensis</i> aus China: divergierende Schnauzenenden und Zähne begrenzt auf vordere Kieferhälfte. Schließlich werden zwei lange Halswirbel, die auch aus der Santana Formation stammen und bislang zu <i>Santanadactylus brasiliensis</i> gerechnet wurden, unter Vorbehalt zu <i>Cearadactylus</i> gestellt. Die Evolutionsgeschichte der Ctenochasmatidae ist durch eine zunehmende Spezialisierung auf filternde Ernährungsweise gekennzeichnet. Die Gnathosaurinen dagegen stellten sich von der filternden auf eine piscivore Ernährung um, wobei sie eine Reihe von Schädelmerkmalen erworben haben, die den Ornithocheiriden konvergent ähnlich ist. <br><br> doi:<a href="http://dx.doi.org/10.1002/mmng.20020050114" target="_blank">10.1002/mmng.20020050114</a>

Sign in / Sign up

Export Citation Format

Share Document