Species of this genus are characterized by deformable flask-shaped cells that exhibit at least one flagellum that is active at the tip, arising from a neck-like structure that also hosts the feeding apparatus.

[9] Their cell body is deformable, but can be distinguished from other euglenids by a flared collar[10] or 'neck' in the anterior region, which hosts a canal where the feeding apparatus and the flagellum are located.

[11] They have been reported in marine and freshwater sediments of various locations, both temperate and tropical, such as the Norwegian Oslofjord,[12] lake Tämnaren [sv] in Sweden,[13] the Danish portion of the Wadden Sea,[3] numerous ponds and wetlands in Czech Republic[11] and Russia,[8] tropical Australia,[14][15] the Juma River in China,[16] and Fiji.

[13] Urceolus is a genus of phagotrophic flagellates belonging to the Euglenida, a highly diverse group that also contains the phototrophic euglenophyte algae.

This is known as the 'second strip duplication event', an evolutionary innovation that presumably led to more plastic movement (metaboly) and an increase in cell size for a clade uniting Urceolus, Peranema and the phototrophic euglenophytes,[17] known as Spirocuta.

[17] Phylogenetic analyses through DNA sequences place all peranemids (e.g., Urceolus, Peranema and others) as a whole as the sister group to euglenophytes, rather than any particular genus.

[2] He described it to accommodate a rare species of flagellate that he discovered that same year in the White Sea, near the Solovetsky Monastery, named U. alenizini.

This genus is essentially equal in appearance to Urceolus, with the only difference being that the cell surface is covered in adherent sand grains.