Given that there are no firm rules for synonymy for high-ranked taxa, alternative names like Leptomedusa, Thecaphora or Thecata, with or without the ending emended to "-ae", are also often used for Leptothecata.

[1] In the sessile stage, Leptothecata are surrounded by a chitinous outer layer as their exoskeleton, including the gonophores, their reproductive organ.

[3] The approximately 1,900 species of Leptothecata are characterized by a number of features: Their polyps are always living in colonies with the hydranths set in hydrotheca which are usually permanent and often long enough so the animal can fully retract into it; some have very reduced hydrothecae resembling Anthoathecata.

The medusae have a shallow bell, bear the gonads on their radial canals, and usually have statocysts which are formed only from epidermal tissue and more than four tentacles and.

The dactylozooid recently had become more highly variable with not being present in some thecata colony forms, and only possessing the gastrozooid and gonozooid polyps.

Which has allowed the synapomorphy for Leptothecata to form hydrothecae that is also made of theca, that surrounds the gonozooid.

[9] The location of where Leptothecata are found ranges from shallow waters to the deep sea, most being marine species.

In their polyp and medusa form, due to natural factors they can travel outside their native location.

[10] Leptothecata has been the main attraction in many great expeditions and studies due to the broad spectrum of thecate hydroids within their order.

These developments have led to further discoveries of finding locations where thecate hydroids can be relatively rich in the marine environment.

Allowing researchers to study a range of differences based on the colonies, the hydrotheca and even the pairs of thecae themselves.