  Measurements of identified particles over a broad $p_T$ range may provide
strong evidence for the existence of a thermalized partonic state in heavy-ion
collisions (\textit{i.e.} a quark-gluon plasma). Of particular interest are the
centrality dependence and the azimuthal anisotropy in the yield of baryons and
mesons at intermediate $p_T$. The first measurements of $v_2$ and the
number-of-binary-collisions scaled centrality ratio $R_{CP}$ for $K_S^0$ and
$\Lambda+\bar{\Lambda}$ production in Au+Au collisions at RHIC are presented.
These measurements from the STAR detector establish the particle-type
dependence of $v_2$ and $R_{CP}$ within $0.4 < p_T < 6.0$. At intermediate
$p_T$ (1.5--4.5 GeV/c) $v_2$ of $K_S^0$ and $\Lambda+\bar{\Lambda}$ is shown to
follow a number-of-constituent-quark scaling with v_2^{kaon}(p_T/2)/2 =
v_2^{lambda}(p_T/3)/3. $R_{CP}$ shows that lambda production at intermediate
$p_T$ increases more rapidly with system size than kaon production: consistent
with multi-parton dynamics in particle production. At $p_T = 5.5$ GeV/c lambda,
kaon, and charged hadron production are suppressed by a similar factor ($R_{CP}
\approx 0.33$): establishing the extent of the centrality dependent baryon
enhancement. The particle- and $p_T$-dependence of $v_2$, and $R_{CP}$ are
consistent with expectations based on hadronization of bulk partonic matter by
coalescence. As such, the constituent-quark-number scaled $v_2$ may reflect the
anisotropy established in a partonic stage providing strong evidence for the
existence of a quark-gluon plasma in Au+Au collisions at RHIC.
