T08B6.9 is a well-defined expressed coding gene with 9 exons.
It has been duplicated in the at some point in the past to produce Y51H4A.22 and Y51H4A.23.
Y51H4A.22 looks like a well-defined expressed coding gene, ending with a polyA site with four and a bit exons.
It looks as it there is an old transposon integration at the end of this gene which has decayed away, leaving the splice site and polyA site now used by this gene.
Y51H4A.23 looks like it is not expressed, which is reasonable if it was split off from Y51H4A.22 by the integration of the transposon and so no longer has a promoter region.
It is likely that this gene will be converted into a Pseudogene by a curator at some point.
So… the story looks like it goes:
The parent gene T08B6.9 was duplicated.
It suffered a transposon integration at some time in the distant past which cut the gene in half.
The 5’ end of the damaged gene was still expressed and still produced a product which had selection operating on it.
The transposon region was subsumed into the new 5’ gene which has continued to be selected for.
The transposon region has degraded away leaving the functional gene Y51H4A.22.
The rump 3’ end is the probable pseudogene Y51H4A.23.