Definitions
from The Century Dictionary.
- noun The composite sacrum in certain extinct reptiles, which may consist of any number of co-ossified vertebræ from three to ten. In the dinosaurs the number is greatest, while in the pterosaurs there are from three to six.
- noun The mass of united vertebræ to which the pelvis is attached in birds. It consists of from ten to twenty vertebræ comprising dorsals, lumbars, true sacrals, and caudals, and is commonly termed the ‘sacrum.'
from Wiktionary, Creative Commons Attribution/Share-Alike License.
- noun anatomy, of birds The
bone composed of thesacrum and somelumbar orcaudal vertebrae fused together.
Etymologies
from Wiktionary, Creative Commons Attribution/Share-Alike License
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Examples
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We also found an assortment of gull bones, including a nice tarsometatarsus, a cervical vertebra, and a dorsal vertebra, along with what appears to be the synsacrum and incomplete pelvis of a cormorant.
"While my feet are the trunks and my head is the canopy, high..." greygirlbeast 2009
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& Ruben (2009) also note that the avian synsacrum might play a role in preventing paradoxical collapse, but this is not explained, nor it is clear how modern birds are fundamentally different from non-avians in this respect.
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In slightly more detail, the paper asserts that a specialised 'femoral-thigh complex', combined with a synsacrum and ventrally separated pubic bones, provides crucial mechanical support for the abdominal wall in modern birds, and has thereby allowed the evolution of large abdominal air-sacs that function in respiration.
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& Ruben (2009) also note that the avian synsacrum might play a role in preventing paradoxical collapse, but this is not explained, nor it is clear how modern birds are fundamentally different from non-avians in this respect.
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In slightly more detail, the paper asserts that a specialised 'femoral-thigh complex', combined with a synsacrum and ventrally separated pubic bones, provides crucial mechanical support for the abdominal wall in modern birds, and has thereby allowed the evolution of large abdominal air-sacs that function in respiration.
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