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KINGDOM DISCICRISTATAE

This taxonomic system groups the kinetoplastids, euglenoids, amoeboflagellates, stephanopogonids, and some of the cellular slime molds together in one kingdom within the supergroup Excavata.  Molecular and ultrastructural data suggest that these occupy a single clade and should be grouped together as a coherent lineage (e.g. Baldauf 2003).  Taxa in this kingdom have mitochondria with distinctive discoid cristae, and the basal bodies (kinetosomes) are paired and are parallel.  Although many produce asexual structures and variable forms through elaborate life cycles, they do not undergo sexual reproduction.  They are sisters to the Kingdom Euexcavata and share the Supergroup Excavata in that some taxa possess the excavate feeding groove.

The relationships between the kinetoplastids and euglenoids have long been recognized to bear clear synapomorphies (Margulis and Schwartz 1998; Barnes 1984; Vickerman 1990b; Lee and Hunter 1985; Patterson 1999; and Taylor 1999).   They all have an anteriorly-directed crypt from whose base emerges the flagella (usually 2 that are heteromorphic and heterodynamic).  The anteriorly-directed flagellum is tinsel and has a paraflagellar rod that lies next to the 9+2 microtubular array.  Patterson (1999) indicates that the paraflagellar rod is tubular and that the other flagellum has a lattice-like structure.  The cell covering is a complex vesiculate pellicle.   

This system represents a modification of Margulis and Schwartz (1998), Patterson (1999), Taylor (1999), and Cavalier-Smith (2003). More recent interpretations of molecular and ultrastructural evidences suggest that some of the jakobids might belong in this kingdom.  Furthermore, the supergroup analyses hint at an association with the cryptomonads and haptomonads (Baldauf 2003).  Thus, I present this system as a work in progress (Go to the Domain Eukarya Page).

A more complete taxonomy (to the ordinal level) of the Kingdom Discicristatae.

New Terms and Concepts for the Kingdom Discicristatae.