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Gryponautilus from the Upper Triassic is broadly involute with a narrowly rounded, keel-like venter at maturity and shallow ventral and lateral lobes in the suture. All members of the Grypoceratidae have a ventral lobe with the exception of Stenoporceras, Parastenopoceras, and Virgaloceras, which have a ventral saddle instead. The derivation of ...
The turtle shell is a shield for the ventral and dorsal parts of turtles (the order Testudines), completely enclosing all the vital organs of the turtle and in some cases even the head. [1] It is constructed of modified bony elements such as the ribs, parts of the pelvis and other bones found in most reptiles.
The external or ventral region refers to sutures along the lower (outer) edge of the shell, where the left and right suture lines meet. The external (or ventral) saddle, when present, lies directly on the lower midline of the shell. As a result, it is often called the median saddle. On suture diagrams the median saddle is supplied with an arrow ...
Crocodilian form of crurotarsal ankle. The astragalus (pink) is fixed to the tibia (green) by a suture. Adapted with permission from Palaeos. In the type of crurotarsal ankle, which is found in crocodilians and some other archosaurs, the astragalus is fixed to the tibia by a suture, and the joint bends around a peg on the astragalus, which fits into a socket in the calcaneum.
The following are the types of ventral sutures. [81] Connective sutures – are the sutures that continue from the facial sutures past the front margin of the cephalon. Rostral suture – is only present when the trilobite possesses a rostrum (or rostral plate). It connects the rostrum to the front part of the dorsal cranidium.
The ecdysial suture is longitudinally placed on the vertex, separating the epicranial halves of the head to the left and right sides. Depending on the insect, the suture may come in different shapes: like either a Y, U or V. Those diverging lines that make up the ecdysial suture are called the frontal or frontogenal sutures.
The ventral (from Latin venter ' belly ') surface refers to the front, or lower side, of an organism, or organ such as the undersurface of the tongue. [ 13 ] In a fish , the dorsal fin is on the upper surface and its ventral fins (pelvic fins) are on the belly or undersurface.
In most fossil nautiluses, the siphuncle runs more or less through the center of each chamber, but in ammonites and belemnites it usually runs along the ventral edge of the shell. In some fossil straight shelled nautiloids, cylindrical calcareous growths ("siphuncular deposits") around the siphuncle can be seen towards the apex of the shell.