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The multiple bones of a bluefin tuna head
Skull of a bluefin tuna (Thunnus thynnus, Scombridae)
Despite the more than 200 bones in the head, bluefin tuna is not the acanthomorph with the most complex skull anatomy. The skull of the remoras (Echeneidae), with a dorsal fin transformed in a sucker and extending onto the head, or the asymmetrical skull of flatfish (pleuronectiformes), or the flattened skull of a monkfish (Lophius piscatorius, Lophiidae) are few examples of higly modified skulls. But, because of their size, the bones of the skull of a bluefin tuna are good tools to learn to identify bony structures.
The different ostéologic layers, from the most superficial bones to intern ones, are here exposed, as they appear during an osteologic dissection.
The colour of the legends refers to the origin of the :
- in red : dermal bones,
- in blue : enchondral bones,
- in purple : bones of mixte origin (dermal and enchondral).
On all images, scale bar indicates 10 cm.
1èr layer : superficial dermal skeleton
Abbreviations |
Nom français |
English name |
| scl | sclérotique | sclerotic |
| la (io1) | lacrymal (= infraorbital 1) | lachrymal (= infraorbital 1) |
| c s io | canal sensoriel infra-orbitaire | infra-orbital sensory canal |
| io 2-6 | infra-orbitaire ou infra-orbital (numérotés de 2 à 6) | infra-orbital (numbered from 2 to 6) |
| exsc | extrascapulaire | extrascapular |
| art hyomd | articulation avec l'hyomandibulaire | hyomandibular articulation |
| op | operculaire | opercular |
| pop | préoperculaire | preopercular |
| sop | sous-operculaire | sub-opercular |
| iop | interoperculaire | interopercular |
2nd layer: appendicular skeleton
Only the pectoral girdle is shown here. To examine the pelvic girdle, please have a look to the page dedicated to osteological systems.
Abbreviations |
Nom français |
English name |
| exsc | extrascapulaire | extrascapular |
| spcl | supracleithrum | supracleithrum |
| mtcl | métacleithrum | metacleithrum |
| lep | lépidotriche | lepidotriche |
| cl | cleithrum | cleithrum |
| rd | radial | radial |
| sc | scapulaire | scapula |
| co | coracoïde | coracoid |
3rd layer: splanchnocranium (gill arches excepted)
Abbreviations |
Nom français |
English name |
| pmx | prémaxillaire | premaxilla |
| mx | maxillaire | maxilla |
| pal | palatin | palatine |
| d | dentaire | dentary |
| ang-art | angulo-articulaire | angulo-articular |
| c | carré | quadrate |
| ecpt | ectoptérygoïde | ectopterygoid |
| mtpt | métaptérygoïde | metapterygoid |
| entpt | entoptérygoïde | entopterygoid |
| hyomd | hyomandibulaire | hyomandibula |
| fc art n | facette d'articulation avec le neurocrâne | articulary facet with the neurocranium |
| fc art op | facette d'articulation avec l'operculaire | articulary facet with the opercular |
| sy | symplectique | symplectic |
| ephy | épihyal | epihyal |
| cthy | cératohyal | ceratohyal |
| r br | rayon branchiostège | gill ray |
| hphy | hypohyal | hypohyal |
| bhy | basihyal | basihyal |
4rd layer: gill arches
Abbreviations |
Nom français |
English nam |
| bhy | basihyal | basihyal |
| u | urohyal | urohyal |
| bbr 1-3 | basibranchial (numérotés de 1 à 3) | basibranchial (numbered from 1 to 3) |
| hpbr | hypobranchial | hypobranchial |
| crbr | cératobranchial | ceratobranchial |
| crbr 5 | cératobranchial 5 | ceratobranchial 5 |
| epbr | épibranchial | epibranchial |
| phbr | pharyngobranchial | pharyngobranchial |
| arc br | arc branchial | branchial arc |
| arc br 2 | arc branchial 2 | branchial arc 2 |
| o d d | os dermique dentigère | dentigerous dermic bone |
5. Neurocranium
The neurocranium is the most intern structure of the skull. It surrounds and protects the encephalon (= "brain"). To study its organisatoon, please consult the page neurocranium.
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