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Invertebrate Zoology
A current probable phylogenetic tree of invertebrate phyla:

Phyla are in order of the chapters in your text book (Pechenik 2000) with the exception of the Lophophorate phyla which I move forward (upward) and adjacent to the Trochozoa phyla.

Click on symbol in phylogenetic tree below to go to information on the particular phylogenetic branch:

? = phylogenetic relationship undetermined due to significant contradications of evidence.
* = recent major change in phylogentic relationship (and still controversial) or other note.
† = links to llustrations of Ernst Haeckel & Rudolph Leuckart
Or click on the phylum name to go to the lecture outline for this group.

 









PHYLUM

Protozoans*
 †

Unicellular










Poriferans †

?
 Placozoans










     ? 

Cnidarians †

?
 Ctenophores †

Diploblasts/Radiata

















 


Platyhelminthes †


   ("Platyzoa")
?
 Mesozoans


*
?
 Nemertines



Rotifers †


  Syndermata

Acanthocephalans


*  ("Spiralia")







Trochozoa
*
 Molluscs †


Annelids*




Sipunculans


Lophotrochozoa
  Phoronids


*
Brachiopods †



Lophophorata ?
Bryozoans †




Entoprocts


Triploblasts/Bilateria



















Panarthropoda

Arthropods †



Ecdysozoa
Tardigrada


*

*
 Onychophorans






Nematodes



*
 Nematomorpha




Cycloneuralia
Priapulida





*
 Kinorhyncha







Loricifera






 








?
 Myxozoa






?
 Gnathostomulida






?
 Gastrotricha






?
 Cheatognatha






?
 Cycliophora













Deuterostoma
Echinoderms †



Hemichordates




*
 Chordates †

Absolute horizontal distance on the above diagram does not imply relative evolutionary time since divergences.  Instead, the diagram above should only be interpreted as order (sequence) of divergence within a particular taxonomic lineage.

The above phylogentic tree incorporates recent findings that include molecule sequence data and more current fossil interpretations (e.g. based on papers from the syposium of Evolutionary Relationships of Metazoan Phyla Advances, in American Zoologist, Volume 38, 1998; but see Jenner 2000 as an example of a cautionary view of this new phylogeny).

Click here to see the Simplified tree to memorize for the first exam:

Click here to see the old (historical) phylogenetic tree that Dr. D. learned in the Dark Ages
 
 
 

Click here for References
  

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