Ecdysozoa jaws and pharyngeal teeth

[ANiknejad]

Very interesting stuff, but not easy to record, indeed, regarding the current available classes in Uberon

http://www.ncbi.nlm.nih.gov/pubmed/?term=26106857

"New material (Supplementary Table 1) and high-resolution microscopic analysis reveals many anatomical features in Hallucigenia for the first time. In particular, robust carbonaceous elements occur around Hallucigenia’s mouth and along its pharynx, implying that the ancestral onychophoran—and seemingly the ancestral ecdysozoan—bore circumoral elements and pharyngeal teeth."

[Term] id: UBERON:2000694 name: ceratobranchial 5 tooth namespace: uberon/phenoscape-anatomy def: "Tooth that forms on ceratobranchial 5 cartilage or bone." [ZFIN:curator] comment: Ceratobranchial 5 teeth are the only teeth present in zebrafish and other cypriniforms. synonym: "pharyngeal teeth" EXACT [TAO:0000694]

Sounds like we should redefine the Uberon pharyngeal teeth? Chris? @cmungall

[cmungall]

MIND BLOWN

OK, so there is the immediate issue that due to our 'lineage' to TAO we make assumptions that pharyngeal teeth are always on element 5. Can we do a quick intra-vertebrate review to determine the tooth-bearing arch derived elements?

But there is also the issue of 'tooth' and 'pharynx'. Both terms are used loosely in analogy-grouping fashion, clustering all kinds of disparate structures. We deal with this in uberon by allowing the loose grouping class, with a subclass for a more structurally and developmentally (and by proxy phylogenetically) unified structure:

• UBERON:0004765 ! skeletal element
  • UBERON:0003913 ! tooth-like structure
  • UBERON:0001091 ! calcareous tooth [develops_from: "tooth placode"] [developmental_contribution_from "neural crest"]

This is kind of fake already, as sea cucumbers can have calcareous(??) anal teeth, yet these don't have neural crest contribution

For the pharynx we just come right out and embed the phylogenetic assumption directly:

• UBERON:0006562 ! pharynx [only_in_taxon: "Bilateria"]
  • UBERON:0001042 ! chordate pharynx [develops_from: "pharyngeal region of foregut"] [only_in_taxon: "Chordata"]

Chordate is perhaps arbitrary, somewhat to do with the presence of arches (but other evidence points to these being in basal deuterostomes I believe)

Neither of these are optimal groupings. I am really hesitant to collapse these altogether. But perhaps neither being calcareous nor being present in Chordates is the most useful differentia for the subclass.

[cmungall]

Not directly related to the above proposed homology, but relevant to any uberon refactor regarding teeth, this article describes histrology and homology of various calcified structures in echinoderms (including anal "teeth" and Aristotle lantern "teeth"): https://www.karger.com/Article/Pdf/142845

[ANiknejad]

Can we do a quick intra-vertebrate review to determine the tooth-bearing arch derived elements?

Not sure I am matching the request here, but while it sounds clear that the fifth ceratobranchial arch (when present) supports the pharyngeal teeth in vertebrate, the evolutionary origin of teeth is still debated see http://www.ncbi.nlm.nih.gov/pubmed/?term=25219878 The ins and outs of the evolutionary origin of teeth.