diff --git a/EXT_SpeciesType.md b/EXT_SpeciesType.md
new file mode 100644
index 0000000..2be5201
--- /dev/null
+++ b/EXT_SpeciesType.md
@@ -0,0 +1,99 @@
+Convention for Specifying Particle Species 
+==========================================
+
+openPMD extension name: `SpeciesType`
+
+
+Introduction
+------------
+
+This convention is for standardizing the names of particle species, e.g. in
+particle physics.
+
+
+Additional Record Attribute
+---------------------------
+
+The following additional attribute for openPMD `mesh records` and
+`particle groups` is defined in this extension:
+
+- `speciesType`
+  - type: *(string)*
+  - scope: *optional*
+  - description: particle species in this record. If there are multiple
+                 species to be specified, they can be specified using a
+                 semicolon separated list.
+  - allowed values:
+    - *see the lists below* and additionally
+    - `other` if none of the ones below applies, user are free to append a
+      free text after a colon, e.g. `other:neutralino` or `other:cherry`
+  - examples:
+    - `electron` (e.g. on an electron `particle record` or an electron
+                  density `mesh record`)
+    - `electron;proton;#12C` (e.g. on a `mesh record` for a plasma's
+                              local charge density)
+    - `other:apple;other:orange` (for a `record` mixing apples & oranges)
+
+This attribute can be used with any `record` (including `mesh records`).
+
+### Elementary Particles
+
+Namings for fundamental fermions and their anti-matter particles.
+
+Quarks:
+  - `up`, `anti-up`
+  - `down`, `anti-down`
+  - `charm`, `anti-charm`
+  - `strange`, `anti-strange`
+  - `top`, `anti-top`
+  - `bottom`, `anti-bottom`
+
+Leptons:
+  - `electron`, `positron`
+  - `electron-neutrino`, `anti-electron-neutrino`
+  - `muon`, `anti-muon`
+  - `muon-neutrino`, `anti-muon-neutrino`
+  - `tau`, `anti-tau`
+  - `tau-neutrino`, `anti-tau-neutrino`
+
+Gauge & Higgs Bosons:
+  - `photon`
+  - `gluon`
+  - `w-boson`
+  - `z-boson`
+  - `higgs`
+
+### Hadrons and Jets
+
+We currently do not define spellings of hadrons besides the commonly used ones
+below and suggest for this version to use `other:` with namings from the
+[particle data group (PDG)](http://pdg.lbl.gov/). Other means of grouping e.g.
+jets can be used, e.g. additional attributes outside of the definition of this
+extension.
+
+Examples:
+  - `proton`, `anti-proton`
+  - `neutron`, `anti-neutron`
+  - `other:sigma`, `other:anti-sigma`
+  - `other:kaon`, ...
+
+### Atoms & Isotopes
+
+Element namings follow the abbreviated namings of the periodic table, defined
+by *The International Union of Pure and Applied Chemistry* (IUPAC).
+An example would be `Si` for silicon.
+
+Specifications of isotopes are denoted by a pound symbol `#` followed
+by the isotopic number followed by the chemical symbol, e.g.: `#3He`
+for Helium-3.
+
+The charge state is not encoded by the `speciesType` attribute.
+Any extension using this standard can define how to specify the charge state.
+
+### Molecules
+
+Use standard chemical notation, e.g.: `H20`.
+
+The isotope prefix can be used with molecules as well.
+Examples for heavy water: `#2H2O` for two deuterium and `#2HHO` for one
+deuterium.
diff --git a/STANDARD.md b/STANDARD.md
index c89c0cd..3e24dcd 100644
--- a/STANDARD.md
+++ b/STANDARD.md
@@ -735,6 +735,8 @@ defined:
 
 - **ED-PIC**: electro-dynamic/static particle-in-cell codes,
   see [EXT_ED-PIC.md](EXT_ED-PIC.md).
+- **SpeciesType**: naming lists for particle species,
+  see [EXT_SpeciesType.md](EXT_SpeciesType.md).
 
 Extensions to similar domains such as fluid, finite-element or
 molecular-dynamics simulations, CCD images or other particle and/or mesh-based