  In this article we consider smooth projective curves $C$ of genus two
described by integral equations of the form $y^2=xh(x)$, where
$h(x)\in\mathbb{Z}[x]$ is monic of degree $4$. It turns out that if $h(x)$ is
reducible, then the absolute discriminant of $C$ can never be an odd prime,
except when $h(x)=(x-b)g(x)$ and $g(x)$ is irreducible. In this case we obtain
a complete description of such genus $2$ curves. In fact, we prove that there
are two one-parameter families $C_t^i$, $i=1,2$, of such curves such that if
$C$ is a genus two curve with an odd prime absolute discriminant, then $C$ is
$C_t^i$, for some $i$, and $t\in\mathbb{Z}$. Moreover, we show that $C_t^i$ has
an odd prime absolute discriminant, $p$, if and only if a certain degree-$4$
irreducible polynomial $f^i(t)\in\mathbb{Z}[t]$ takes the value $p$ at $t$.
Hence there are conjecturally infinitely many such curves. When $h(x)$ is
irreducible, we give explicit examples of one-parameter families of genus $2$
curves $C_t$ such that $C_t$ has an odd prime absolute discriminant for
conjecturally infinitely many integer values $t$.
