Definittey not Scomberoides. Easiest way to differentiate Scombs from other Hyrdolycus is the gill spot. Arms and Tats have a slash like mark behind their gills while the Scomb has a round spot.
Scomberoides below
Tatauaia
And Armatus can be differentiated from Tats by white edging on their tail and adipose fin
There are other differences but IMO these are the easiest ways to identify between Hyrdolycus. Here's a pic that shows them side by side which makes the other differences between some Cynodontinae more apparent.