Corybas dentatus, commonly known as the Lofty Ranges helmet orchid, is a species of terrestrial orchid endemic to South Australia. It has a more or less round leaf and a single purplish and green flower. It is only known from two locations and is listed as "vulnerable" under the Environment Protection and Biodiversity Conservation Act.
Corybas dentatus is a terrestrial, perennial, deciduous, herb with a broad egg-shaped, heart-shaped or almost round leaf NaNsigfig=1NaNsigfig=1 long and NaNsigfig=1NaNsigfig=1 wide. The leaf is green on the upper surface and silvery green on the lower side. A single purplish and green flower NaNsigfig=1NaNsigfig=1 long and NaNsigfig=2NaNsigfig=2 wide is borne on a short flowering stem. The largest part of the flower is the dorsal sepal which is NaNsigfig=2NaNsigfig=2 long and NaNsigfig=2NaNsigfig=2 wide. It is pinkish grey with dark purple markings and forms a hood over the labellum. The lateral sepals are whitish, linear to lance-shaped, about 5sigfig=1NaNsigfig=1 long, and 1sigfig=1NaNsigfig=1 wide and spread widely apart from each other. The petals are lance-shaped, about 3sigfig=2NaNsigfig=2 long, 1sigfig=1NaNsigfig=1 wide and curved. The labellum is dark purple, tube-shaped near its base, about 6sigfig=1NaNsigfig=1 long, before curving and flattening into a broad egg-shaped flat NaNsigfig=2NaNsigfig=2 long and wide with teeth on the edges. Flowering occurs in July and August.[1] [2] [3]
Corybas dentatus was first formally described in 1991 by David Jones from a specimen collected in the Sandy Crrek Conservation Park and the description was published in Australian Orchid Research.[4] The specific epithet (dentatus) is a Latin word meaning "toothed" or "pointed",[5] referring to the prominent teeth on the edges of the labellum.
In 2002, David Jones and Mark Clements proposed splitting Corybas into smaller genera and placing this species into Corysanthes but the change has not been widely accepted.
The Lofty Ranges helmet orchid grows in open forest and woodland with low shrubs and ferns. It is known from two populations, the larger of which is in the Sandy Creek Conservation Park.
Corybas dentatus is classified as "vulnerable" under the Australian Government Environment Protection and Biodiversity Conservation Act 1999. The main threats to the species are road and track maintenance, weed invasion, herbicide spraying and population fragmentation.