scholarly journals Diverse stem-chondrichthyan oral structures and evidence for an independently acquired acanthodid dentition

2021 ◽  
Vol 8 (11) ◽  
Author(s):  
Richard P. Dearden ◽  
Sam Giles
Keyword(s):  
Conveyor Belt ◽  
Major Obstacle ◽  
Site Specific ◽  
Meckel's Cartilage ◽  
Jaw Bones ◽  
Lateral Edge ◽  
Meckel’S Cartilage ◽  
Independent Origin ◽  
Bony Fishes ◽  
Dermal Bone

The teeth of sharks famously form a series of transversely organized files with a conveyor-belt replacement that are borne directly on the jaw cartilages, in contrast to the dermal plate-borne dentition of bony fishes that undergoes site-specific replacement. A major obstacle in understanding how this system evolved is the poorly understood relationships of the earliest chondrichthyans and the profusion of morphologically and terminologically diverse bones, cartilages, splints and whorls that they possess. Here, we use tomographic methods to investigate mandibular structures in several early branching ‘acanthodian’-grade stem-chondrichthyans. We show that the dentigerous jaw bones of disparate genera of ischnacanthids are united by a common construction, being growing bones with non-shedding dentition. Mandibular splints, which support the ventro-lateral edge of the Meckel's cartilage in some taxa, are formed from dermal bone and may be an acanthodid synapomorphy. We demonstrate that the teeth of Acanthodopsis are borne directly on the mandibular cartilage and that this taxon is deeply nested within an edentulous radiation, representing an unexpected independent origin of teeth. Many or even all of the range of unusual oral structures may be apomorphic, but they should nonetheless be considered when building hypotheses of tooth and jaw evolution, both in chondrichthyans and more broadly.

scholarly journals New osteichthyans (bony fishes) from the Devonian of Central Australia

Fossil Record ◽  
2005 ◽  
Vol 8 (1) ◽  
pp. 13-35 ◽  
Author(s):  
G. C. Young ◽  
H.-P. Schultze
Keyword(s):  
Middle Devonian ◽  
Line System ◽  
Meckel's Cartilage ◽  
Small Form ◽  
Skull Roof ◽  
Meckel’S Cartilage ◽  
Lower Jaw ◽  
Bony Fishes ◽  
New Type ◽  
Central Australia

Abstract. Osteichthyan remains described from two localities in Central Australia (Mount Winter, Amadeus Basin, and southern Toomba Range, Georgina Basin) include the dipnoan Amadeodipterus kencampbelli n. gen., n. sp., the osteolepidid Muranjilepis winterensis n. gen., n. sp., and the onychodontid Luckeus abudda n. gen., n. sp., as well as indeterminate holoptychiid scales, osteolepidid scales of a new type from the Georgina Basin locality, and indeterminate onychodontid remains from both localities. Amadeodipterus n. gen. is a short-headed dipterid dipnoan with bones A and H enclosed into the skull roof; Muranjilepis n. gen. is a small form with short postparietal and parietoethmoidal shields, large orbits, and large pores of the sensory line system. It is closest to Thursius, and some Chinese osteolepidid material. Luckeus n. gen. is based on an onychodontid lower jaw with Meckel’s cartilage separately ossified perichondrally from the dentary and infradentary, and carrying the parasymphysial tooth whorl. Different osteichthyan taxa at the two localities indicate a difference in age and/or palaeoenvironment within the Early-Middle Devonian. Knochenfischreste aus zwei Fundorten Zentralaustraliens (Mount Winter, Amadeus Becken und südlicher Toomba Rücken, Georgina Becken) umfassen den Lungenfisch Amadeodipterus kencampbelli n. gen., n. sp., den osteolepididen Sarcopterygier Muranjilepiswinterensis n. gen., n. sp., und den onychodontiden Sarcopterygier Luckeus abudda n. gen., n. sp., sowie unbestimmte holoptychiide und osteolepidide Schuppen eines neuen Typs aus dem Fundort im Georgina Becken und unbestimmte onychodontide Reste von beiden Fundorten. Amadeodipterus n. gen. ist ein kurz-schädeliger Lungenfisch, bei dem die Knochen A und H in das Schädeldach miteingeschlossen sind. Bei Muranjilepis n. gen. handelt es sich um einen kleinen Osteolepididen mit kurzem Postparietal- und Parietoethmoidal-Schild, großen Augenhöhlen und großen Poren des Sinneskanalsystems; er ist am nächsten mit Thursius und einigen chinesischen Osteolepididen verwandt. Ein unbestimmter onychodontider Unterkiefer zeigt ein wahrscheinlich primitives Merkmal in der perichondralen Verknöcherung des Meckelschen Knorpels getrennt von Dentale und Infradentale, der die Unterlage der parasymphysialen Zahnspirale bildet. Verschiedene Knochenfischtaxa treten an den beiden Lokalitäten auf; das deutet auf unterschiedliches Alter und/oder Palaeoenviroment an der Unter-Mitteldevongrenze zwischen beiden Lokalitäten hin. doi:10.1002/mmng.200410002

Biological Significance of Site-specific Transformation of Chondrocytes in Mouse Meckel’s Cartilage

2010 ◽  
Vol 52 (2) ◽  
pp. 136-142
Author(s):  
Kiyoto Ishizeki ◽  
Tadayoshi Kagiya ◽  
Naoki Fujiwara ◽  
Keishi Otsu ◽  
Hidemitsu Harada
Keyword(s):  
Biological Significance ◽  
Site Specific ◽  
Meckel's Cartilage ◽  
Meckel’S Cartilage

Memoirs: The Posterior End of Meckel's Cartilage and Related Ossifications in Bony Fishes

1937 ◽  
Vol s2-80 (317) ◽  
pp. 1-38
Author(s):  
R. WHEELER HAINES
Keyword(s):  
Joint Surface ◽  
Connective Tissues ◽  
Endochondral Bone ◽  
Meckel's Cartilage ◽  
Articular Process ◽  
Meckel’S Cartilage ◽  
Bony Fishes ◽  
Growth Zones ◽  
Special Growth ◽  
And Cartilage

1. In modern Dipnoi (Protopterus) the membrane bones are separated by connective tissue from Meekel's cartilage, and there is no endochondral or perichondral bone. The cartilage grows evenly over its whole extent. 2. In Polypterus a large articular ossifies the posterior end of the cartilage, including the retro-articular process, and spreads into the neighbouring connective tissues. 3. In Elops the joint surface is carried partly by the articular, and partly by the retro-articular, a special ossification of the retro-articular process. 4. In most teleosts (Mugil, Sardina, Trigla) the articular is absent and the angular invades the perichondrium and cartilage to form the joint surface. Special growth zones of flattened cells are formed in the cartilage which by their growth carry the retro-articular, angular, and dentary away from one another, stability of the jaw being maintained by new growth of the membranous parts of the bones. 5. Endochondral bone is reduced or absent in some specialized fishes (Tetrodon, Notopogon). 6. The sesamoid articular of teleosts is a separated part of the angular which gives insertion to the adductor mandibulae muscle. 7. An attempt is made to follow the evolution of Meckel's cartilage and the related ossifications by a comparison of the early Dipnoi, Crossopterygii, and Amphibia described in the literature with modern forms.

Biological Significance of Site-specific Transformation of Chondrocytes in Mouse Meckel's Cartilage

2010 ◽  
Vol 52 (2) ◽  
pp. 136-142 ◽  
Author(s):  
Kiyoto Ishizeki ◽  
Tadayoshi Kagiya ◽  
Naoki Fujiwara ◽  
Keishi Otsu ◽  
Hidemitsu Harada
Keyword(s):  
Biological Significance ◽  
Site Specific ◽  
Meckel's Cartilage ◽  
Meckel’S Cartilage

scholarly journals Dental diversity in early chondrichthyans and the multiple origins of shedding teeth

2020 ◽  
Author(s):  
Richard P. Dearden ◽  
Sam Giles
Keyword(s):  
Site Specific ◽  
Total Group ◽  
Multiple Origins ◽  
Bony Fishes ◽  
Dermal Bone

AbstractThe teeth of sharks famously form a series of parallel, continuously replacing files borne directly on the mandibular cartilages. In contrast, bony fishes possess site-specific shedding dentition borne on dermal plates. Understanding how these disparate systems evolved is challenging, not least because of poorly understood relationships and the profusion of morphologically and terminologically diverse bones, splints and whorls seen in the earliest chondrichthyans. Here we use tomographic methods to investigate the nature of mandibular structures in several early branching ‘acanthodian’-grade stem-chondrichthyans. We characterise the gnathal plates of ischnacanthids as growing bones, and draw similarities between early chondrichthyan and stem gnathostome teeth and jaws. We further build the case for Acanthodopsis, a Carboniferous taxon, as an acanthodid, and show that, unexpectedly, its teeth are borne directly on the mandibular cartilage. Mandibular splints are formed from dermal bone and appear to be an acanthodid synapomorphy. The development of a unidirectionally growing dentition may be a feature of the chondrichthyan total-group. More generally, ischnacanthid and stem gnathostome gnathal plates share a common construction and are likely homologous, and shedding teeth evolved twice in gnathostomes.

scholarly journals Modulated Expression of Type X Collagen in the Meckel's Cartilage with Different Developmental Fates

1995 ◽  
Vol 170 (2) ◽  
pp. 387-396 ◽  
Author(s):  
Kun Sung Chung ◽  
Howard H. Park ◽  
Kang Ting ◽  
Hiroko Takita ◽  
Suneel S. Apte ◽  
...  
Keyword(s):  
Type X Collagen ◽  
Meckel's Cartilage ◽  
Meckel’S Cartilage

scholarly journals Functional analysis of CTRP3/cartducin in Meckel’s cartilage and developing condylar cartilage in the fetal mouse mandible

2011 ◽  
Vol 218 (5) ◽  
pp. 517-533 ◽  
Author(s):  
Tamaki Yokohama-Tamaki ◽  
Takashi Maeda ◽  
Tetsuya S. Tanaka ◽  
Shunichi Shibata
Keyword(s):  
Functional Analysis ◽  
Condylar Cartilage ◽  
Meckel's Cartilage ◽  
Fetal Mouse ◽  
Meckel’S Cartilage

Effect of Biomechanical Environment on Degeneration of Meckel’s Cartilage

2020 ◽  
pp. 002203452096011
Author(s):  
M. Farahat ◽  
G.A.S. Kazi ◽  
E.S. Hara ◽  
T. Matsumoto
Keyword(s):  
Endochondral Ossification ◽  
Biomechanical Properties ◽  
Cartilage Degradation ◽  
Middle Region ◽  
Meckel's Cartilage ◽  
3 Dimensional ◽  
Meckel’S Cartilage ◽  
Surrounding Environment ◽  
Rigid Environment

During orofacial tissue development, the anterior and posterior regions of the Meckel’s cartilage undergo mineralization, while the middle region undergoes degeneration. Despite the interesting and particular phenomena, the mechanisms that regulate the different fates of Meckel’s cartilage, including the effects of biomechanical cues, are still unclear. Therefore, the purpose of this study was to systematically investigate the course of Meckel’s cartilage during embryonic development from a biomechanical perspective. Histomorphological and biomechanical (stiffness) changes in the Meckel’s cartilage were analyzed from embryonic day 12 to postnatal day 0. The results revealed remarkable changes in the morphology and size of chondrocytes, as well as the occurrence of chondrocyte burst in the vicinity of the mineralization site, an often-seen phenomenon preceding endochondral ossification. To understand the effect of biomechanical cues on Meckel’s cartilage fate, a mechanically tuned 3-dimensional hydrogel culture system was used. At the anterior region, a moderately soft environment (10-kPa hydrogel) promoted chondrocyte burst and ossification. On the contrary, at the middle region, a more rigid environment (40-kPa hydrogel) enhanced cartilage degradation by inducing a higher expression of MMP-1 and MMP-13. These results indicate that differences in the biomechanical properties of the surrounding environment are essential factors that distinctly guide the mineralization and degradation of Meckel’s cartilage and would be valuable tools for modulating in vitro cartilage and bone tissue engineering.

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