from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A bone situated immediately beneath the sphenoid in the base of the skull in many vertebrates.
from the GNU version of the Collaborative International Dictionary of English
- adj. Near the sphenoid bone; -- applied especially to a bone situated immediately beneath the sphenoid in the base of the skull in many animals.
from The Century Dictionary and Cyclopedia
- n. A long azygous dagger-shaped membrane-bone extending in midline lengthwise beneath the base of the skull in Sauropsida, along the course of the sphenoid bone proper. It forms part of the so-called rostrum or beak of the skull.
- n. A median unpaired bone underlying the skull of amphibians and fishes, articulating with the vomer in front and with several bones behind.
- n. This does not appear to be the same bone as that of the same name in the higher vertebrates, and has been ho-mologized by some authors with the true vomer of the latter. See def. 1, and cuts under Lepidosiren and Anura.
- Lying under or alongside the sphenoid; of or pertaining to the parasphenoid, in either sense; parasphonoidal.
He recognised also that the bone now known as the parasphenoid was developed in the frog in the mucous membrane of the mouth, and had originally no connection with the cranial basis (p. 34).
Hertwig considered that the following bones were originally formed by coalescence of teeth -- parasphenoid, vomer, palatine, pterygoid, the tooth-bearing part of the pre-maxillary, the maxillary, the dentary and certain bones of the hyo-mandibular skeleton of
There is no parasphenoid in the mammal*; and, instead, a complete series of ossifications, the median -, basi -, and pre-sphenoids, and the lateral ali - and orbito-sphenoids occur.
Remove from it and place in glycerine on a glass slip the fronto-parietal and parasphenoid bones.
It contains only two ossifications in its cartilaginous substance (the sphen-ethmoid and the ex-occipital), being protected by the membrane bones, the parieto-frontals above and the parasphenoid below.
In the salamander, behind the teeth-bearing vomers comes a similar toothed parasphenoid bone.
It does so in the possession of gills and of a branchial apparatus during one time of life at the least; a large parasphenoid in the skull; the often persistently unsegmented terminal part of the notochord; the single ventricular cavity of the heart; the presence of a bulbus aortæ; the development of a nervus lateralis; the communication between the urinary canal and the oviduct, and certain other characters of less importance.
Although this great membrane bone is constant in Batrachians and bony fishes, and is represented, if at all, only by minute rudiments in higher vertebrates; nevertheless in serpents we once more meet with a far-reaching and well-developed parasphenoid.