Old turtler following excavation discovered fins turned outward (9)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

EX- (=old, former) + T <urtle> R (“following excavation” means all but first and last letters are dropped) + <d> ORSAL <s> (=fins; “dis- cover -ed”, i.e. “cover” – first and last letters – is dropped); extrorsal means “turned outward”, e.g. of an anther towards a flower