Tsn mouth are designed to open much larger than adult rtc. Anatomically their skulls are lighter and more loosely connected than rtc. Adult tsn can take larger prey than rtc. Rtc is an advanced and opportunistic predator that takes a wide variety of prey items but in the wild mainly crustaceans. Tsn is more of a sit abd wait predator and needs the very large mouth to take whatever sized prey comes close but will also actively hunt when hungry. Planiceps takes it even farther. The flatter the head and more compressed it is the larger the mouth can gape. Size of the body has nothing to do with it. 2' rtc mouth gapes about 5" but 2' tsn mouth can gape around 7". Much thinner fish but the anatomical design allows the mouth to open much farther.just though i would throw that out there.
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I missed your knowledge on here Cliff. Good to have ya back man.