Family Asteraceae > Subfamily Cichorioideae > Tribe Cichorieae > Subtribe Crepidinae.
Dandelions are native to Eurasia and North America.

Plants of the World Online lists 2472 species while others recognise only 60.
The around 2500 species are divided into 60 or 70 sections.

Identification and classification is very difficult with constant revisions.
Problems are mainly because so many reproduce asexually without cross fertilisation (apomixis).
These lines have more mutations leading to different populations in any area that can each be classified as a microspecies.
It is the acceptance of these local differences that leads to the large number of species some recognise.
There are plants that produce by cross fertilisation and these more stable lines are easier to identify as species.

Sexually reproduced plants have the normal 2 sets of chromosomes while the asexually produced ones can have 2 (diploid) or
    3 (triploid) sets and occasionally more (polyploid).

The species most commonly seen are the Common dandelion T. officinale and the Red-seeded dandelion T. erythrospermum.

Dandelions are flat-weeds with all the leaves in a basal rosette, a flower-head on a hollow peduncle, heads with only ray
    florets with a ligule and an involucre with 2 rows of bracts.