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Nilanjan Bhowmick AIR 3, CSIR NET (Earth Science)
- IIT JAM
- Geology (GG)
Pls explain my confusion in classification of bivalve on the basis of sense of umbo below:-
suppose we take the prosogyrate body, and we consider that the umbo is present on the anterior side .. but what about the other half/valve .. it looks like as if the umbo is also present on the posterior side .. how can we exactly differentiate? where to consider posterior and anterior properly?
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Mayank vedwal Vedwal Best Answer
In a bivalve shell umbo and beak always present on the dorsal side of the valve and prosogyrate is a type of bivalve in which beak points toward anterior of the shell. The projection of beak is same on both valve ....In prosogyrate beak points towards anterior on both valve, it is not like that beak is projecting anterior on one and posterior on another... for this confusion look at given figure carefully and attach both valve's umbo together you will get which side is anterior and which is posterior....... Now coming on how to find anterior and posterior of umbo , so there are some features like pallial sinus, escutcheon which are present on posterior side of bivalve and opposite side of posterior is anterior side.
that means if we consider an ophistogyrate body then the umbo , as it is said which is present on the posterior side ... that means umbo is present near the escutcheon? and in prosogyrate umbo is present near the lunule?
yes