# How does one use \node[inner node]{}?

I'm trying to reproduce a TikZ tree from a Till Tantau presentation (see pg.33 of this .pdf)

My code is as follows:

\documentclass{article}

\usepackage[latin1]{inputenc}
\usepackage{tikz}
\usetikzlibrary{trees}
\begin{document}

\begin{tikzpicture}[edge from parent fork down, edge from parent/.style={black,thick,draw}]

\node[inner node]{}
child { node {bacteria} }
child {  node[inner node] {}
child { node {plants} }
child   { node[inner node] {}
child { node[inner node] {}
child { node {fish} }
child { node[inner node] {}
child { node {mammals} }
child { node {birds} }
}
}
child { node[inner node] {}
child { node {dragonflies} }
child { node {beetles} }
}
}
};

\end{tikzpicture}

\end{document}

I get six errors of the type below for each of the six node[inner node] {} calls in the code above:

! Package pgfkeys Error: I do not know the key '/tikz/inner node' and I am goin
g to ignore it. Perhaps you misspelled it.
See the pgfkeys package documentation for explanation.
Type H <return> for immediate help.
...
l.11 \node[inner node]
{}
This error message was generated by an \errmessage
command, so I can't give any explicit help.
Pretend that you're Hercule Poirot: Examine all clues,
and deduce the truth by order and method.

I couldn't find anyting pertinent on this type of usage in the PGF manual. Any help is welcome!

-
Which version of PGF are you using? –  Loop Space Sep 15 '11 at 15:52
inner node is the name of a node with a matrix but it's not a style with PGF 2.10 CVS. –  Alain Matthes Sep 15 '11 at 18:40
I get a similar error message with TeXLive2011 (updated within the last week)... –  Peter Grill Sep 15 '11 at 20:28
I use PGF 2.0 which is available as a debian package under Ubuntu 11.04 –  champost Sep 15 '11 at 22:15