  We investigate systematics of the freezeout surface in heavy ion collisions
due to the hadron spectrum. The role of suspected resonance states that are yet
to be confirmed experimentally in identifying the freezeout surface has been
investigated. We have studied two different freezeout schemes - unified
freezeout scheme where all hadrons are assumed to freezeout at the same thermal
state and a flavor dependent sequential freezeout scheme with different
freezeout thermal states for hadrons with or without valence strange quarks.
The data of mean hadron yields as well as scaled variance of net proton and net
charge distributions have been analysed. We find the freezeout temperature $T$
to drop by $\sim5\%$ while the dimensionless freezeout parameters $\mu_B/T$ and
$VT^3$ ($\mu_B$ and $V$ are the baryon chemical potential and the volume at
freezeout respectively) are insensitive to the systematics of the input hadron
spectrum. The observed hint of flavor hierarchy in $T$ and $VT^3$ with only
confirmed resonances survives the systematics of the hadron spectrum. It is
more prominent between $\sqrt{s_{NN}}\sim10 - 100$ GeV where the maximum
hierarchy in $T\sim10\%$ and $VT^3\sim40\%$. However, the uncertainties in the
thermal parameters due to the systematics of the hadron spectrum and their
decay properties do not allow us to make a quantitative estimate of the flavor
hierarchy yet.
