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Role in Cambrian

Genera: 308
Groups: 10
Descriptors: 122

User guide
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Last modified : 6 December 2012

- ARCHAEOCYATHA - A knowledge base

General remarks


Since archaeocyathan are important Cambrian organisms, it is necessary for specialists and non-specialists to identify specimens. For a long time, several attempts to find identifications tools have been made, but keys, easy to use and adapted even to incomplete specimens, were lacking before this work. The first try is linked to archaeocyaths systematics: Archeocyaths systematics is made like an identify key. Then, using Vavilov's Law of homologous series (Vavilov 1922), Rozanov built a table with Archaeocyatha variability, that is used for identification (Rozanov & Missarzhevskiy 1966).
With computer arrival, created a database becomed a will. During a symposium in 1981, a first database was presented (Debrenne & Prieur 1981) on Ajacicyathida. A second one began during the 8O's by M. and F. Debrenne and followed informatics overhangs (Dbase2 then Dbase 5). User had to answer questions to follow archaeocyaths systematics. ECAD was never diffused and stopped in abeyance of taxonomic revisions. (Debrenne et al. 2002).Finally, a first French version of this knowledge base was presented during RST (RÚunion des Sciences de la Terre) Symposium in 2006 (Debrenne & Kerner 2006).


Xper▓ is a software dedicated to store structured descriptive data and to provide free access keys. It appears well adapted to manage the knowledge about archaeocyaths. It is one of the most suitable tools in this category. It is free of charge and offers an intuitive interface in several languages. It was already validated and used for various applications on marine or terrestrial taxa. Thus Xper▓ is adapted as well as for specialists (edition and diffusion knowledge on their taxonomic groups), as well as for users, neophytes or non-neophytes (using identification unit).
To know more about this tool see Ung et al. 2010 or http://lis-upmc.snv.jussieu.fr/lis/?q=en/resources/software/xper2
The identification service offered by Xper2 is available offline or on internet as a free access key. In a free access key, the choice of the descriptor is up to the user at each step of the key. The computer-aided identification tool deduces the remaining and eliminated taxa and can display the reasons for each elimination. This type of identification system is very flexible and allows to identify a specimen even if some characters are not available (incomplete specimen for example).

Archaeocyathan knowledge base

The computer-aided knowledge base is composed of the 308 genera considered to be valid at present. Concerning the geographical repartition it is a world-wide scale. Stratigraphical extension contains all the Cambrian even if most of Archaeocyatha lived during lower Cambrian. Each genus is illustrated with types specimens and sometimes with additional specimens better preserved. 122 descriptors are used:
  • 87 corresponding to morphological and ontogenetic data
  • 8 to stratigraphic and geographic data
  • 27 to taxonomic data
To each descriptor and character state we associated a definition and pictures and/or sketches. In the identification unit, some distinctive features appear: Two main reasons explain these choices:
  • The knowledge base has to be accessible for a large public:
    • Characters without taxonomic significance are present because they often can be seen easily.
    • Descriptors names should be easily understand.
In usual terminology, one term can imply several basic descriptors. Here we try using only basic descriptors (i.e.: mircoporous wall means a wall has two different parts: a carcass and a additional sheath).