diff --git a/EXT_SpeciesType.md b/EXT_SpeciesType.md
new file mode 100644
index 0000000..05b9a9c
--- /dev/null
+++ b/EXT_SpeciesType.md
@@ -0,0 +1,95 @@
+Convention for Specifying Particle Species 
+==========================================
+
+openPMD extension name: `SpeciesType`
+
+openPMD extension ID: `4`
+
+
+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 `records` 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.
+
+### 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 9524470..ad4ccf8 100644
--- a/STANDARD.md
+++ b/STANDARD.md
@@ -730,6 +730,8 @@ 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