A Grammatical Dictionary of Botanical Latin

Subdivision: subdivisio,-onis s.f.III, acc. sg. subdivisionem, dat. sg. subdivisioni, abl.sg. subdivisione, nom. & acc. pl. subdivisiones, gen. pl. subdivisionum, dat. & abl. pl. subdivisionibus.

- species nova ab omnibus aliis speciebus suae subdivisionis foliis ellipticis differt, the new species from all other species of its own subdivision differs by the elliptic leaves.

- species nova inter species subdivisionis Leptosphaeriophytinorum ramis dorsiventralibus distincta, new species distinct among species of the subdivision Leptosphaeriophytina by the dorsiventral branches.

- subdivisio nova a subdivisione Basidiomycotinis distincta, new subdivision distinct from the subdivision Basidiomycotina.

NOTE: a noun used to describe another, and denoting the same person or thing, agrees with it in case: e.g. above: subdivisione (abl.) and Basidiomycotinis (abl.) even though one is a singular and the other a plural noun.

According to the Code of Nomenclature (Vienna 2006) (Article 16.3 Note 1) the term division and phyllum are synonymous: they refer to the same rank. By extension, the term subdivision is synonymous with subphyllum:

        sg.             pl.                  sg.                  pl.
Nom. subdivisio    subdivisiones     Nom. subphylum (s.n.II)   subphyla
Gen. subdivisionis subdivisionum     Gen. subphyli             subphylorum
Dat. subdivisioni  subdivisionibus   Dat. subphylo             subphylis
Acc. subdivisionem subdivisiones     Acc. subphylum            subphyla
Abl. subdivisione  subdivisionibus   Abl. subphylo             subphylis

According to the Code of Nomenclature (Vienna 2006) (recommendation 16A.2):

Latin endings for the ranks of subdivision and subphylum are:

1. for all plants except fungi:  -phytina
      [> stem of designated ending for rank of division or phylum (-phyta) + 
      + neuter plural adj. ending -ina of L. adj. endings -inus,-a,-um:
      phyt- + -ina (pl.n.II), gen. pl. -phytinorum, dat. & abl. pl. -phytinis, acc. pl. -phytina.
         Bryophytina (Bryum), Cycadophytina (Cycas,-adis), Equisetophytina (Equisetum),  
Ginkgoophytina (sic) (Ginkgo), Gnetophytina (Gnetum); Pinophytina (Pinus); 
Pteridophytina (Pteris,-idis), Sphagnophytina (Sphagnum).
2. for fungi:                    -mycotina
      [> stem of designated ending for rank of division or phylum of fungi (-mycota)
      + neuter plural of L. adj. endings -inus,-a,-um:
      mycot- + -ina (pl.n.II)], gen. pl. -mycotinorum, dat. & abl. pl. -mycotinis, acc. pl. -mycotina.
          Agaricomycotina (Agaricus), Basidiomycotina, Eumycotina

NOTE: there is no special designation for Algae as there is in the ranks of class and subclass, q.v.