I don't believe any species of Earless dragon has ever been common in captivity. Some seem to go through a brief period where a number are available because of a successful breeding program with a particular female, vis-a vie, T. centralis about 4-5 years ago coming out of Alice Springs and T. cephalus and T.tetraporophora coming from a captive breeding program on the Subshine Coast. But other then that I would say they are and have always been relatively hard to get in captivity. I know I have had to work extremely hard with my contacts to get hold of the specimens I have been able to acquire.
There are 8 species of earless dragons currently recognised. Of these there is only one that is seriously at risk in the wild, T. pinguicolla. All other species are relatively common although the effect of recent flooding in inland Australia on populations is still unknown.
The concern with T. pinguicolla (the Grassland Earless Dragon) is that the population that was thought to exist west of Brisbane has been reclassified as an island population of T. tetraporophora. (See Wilson and Swan 3rd Edition 2010). This means quite literally that of the 3 locations where this species was thought/known to occur, there is now only one that still has a population that appears to be viable and sustaining itself. The other location to the west of Melbourne has not seen one of these animals collected since 1960. in the ensuing period there have been some reports of T. pinguicolla being collected just north of Melbourne on the urban fringe, but how reliable these reports are I am not sure.
I have worked with earless dragons for the last 10 years and I can say quite categorically, they are an extremely difficult animal to keep. The husbandry with these animals needs to be exactly right. I have and I know of a handful of others who have bred various species of this group. The five species that I know have been bred are centralis, cephalus, lineata, intima, and tetraporophora. The 3 species that are not in private keepers collections to my knowledge at this point are, T. pinguicolla, houstoni and uniformis. I say this because I see dozens of posts on this and other forums from people either claiming that the keeping process is easy or wanting to get hold of some of these animals and then asking how to keep them. If you have to ask how then you probably really should not keep these guys. If you cannot give daily attandance to these animals without stressing them then they will not do well. They need to monitored very closely without being obtrusive. Stress is a serious problem.
The captive breeding program with T. pinguicolla has been floated for the last couple of years. There are even some thoughts with the regulatory authority involved that selected private keepers should be included. I believe this is critical if the program is to be successful. (See ARC and the work Gerry Marantelli has done with safeguarding the future of Corroboree Frogs). I fully support not only the proposal to captive breed but to include suitably experienced private keepers and totally endorse the suitability of one of the people who I am aware has been asked for their EOI. Whether these animals ever end up in private collections is not important although the availability of viable numbers of any species breeding regularly in captivity certainly gives hope that the species can be reintroduced into the wild assuming all other environmental parameters have been addressed.
