Correct Thyristor IV characteristics
The two curves are essentially the same with the second showing more detail.

The first curve shows only the characteristic with no gate current. The second curve shows the characteristic with no gate current and also the characteristic with insufficient gate current for efficient turn-on (Ig > 0 and the gate current required for efficient turn-on (Ig >> 0). The second curve has a current scale that is much lower current per vertical distance.

The second curve can be used to illustrate latching current and holding current.

For more information, see the General Electric SCR Manual Fifth Edition sections 3.12 Holding and Latching Current p67 and 4.1 The Triggering Process, p71. A PDF and be found here and here and possibly elsewhere.