\textit{T. Penttila} and \textit{B. Williams} [Geom. Dedicata, to appear] have constructed a sporadic translation ovoid of the quadrangle \(Q(4, 3^5)\). Associated with this, there is a new (semifield) flock of a quadratic cone in \(\text{PG}(3,3^5)\), and hence a flock generalized quadrangle of order \((3^5,3^{10})\). The authors prove that this generalized quadrangle is new. Moreover, it is a translation generalized quadrangle, and also its translation dual is shown to be new. The exciting news about this is that it provides a counterexample to a conjecture recently stated by \textit{J. A. Thas} [J. Comb. Theory, Ser. A 79, No. 2, 223-254 (1997; Zbl 0887.51004)], saying that every semifield flock generalized quadrangle is known (classical, Kantor or Ganley).