Blattoptera, or proto-cockroaches, is a name given to various "roachid" fossil insects related to cockroaches, mantises and termites, and of general cockroach-like appearance and possibly habit. The group is on the rank of an order, though being paraphyletic is most often given without formal taxonomic rank. Several alternative names have been suggested for this fossil group, including Blattodea, a name currently used for the group including the modern cockroaches as well as their fossil relatives.
Cockroaches are popularly thought to be an ancient order of insects, with their origins in the Carboniferous. However, since the middle of the 20th century it has been known that the primitive cockroach insects found fossilized in Palaeozoic strata are the forerunners not only of modern cockroaches but also of mantises and termites. The origin of these groups from a blattopteran stock are now generally thought to be in the early Jurassic; the earliest modern cockroach found is from the Cretaceous. Thus the “Palaeozoic cockroaches” are not cockroaches per se, but a paraphyletic assemblage of primitive relatives.
The fossils assigned to the "roachids" are of general cockroach-like build, with a large disc-like pronotum covering most of the head, long antennae, legs built for running, flattened body and heavily veined wings with the distinct arched CuP-vein so typical of modern cockroach wings. Like modern cockroaches, the roachids were probably swift litter inhabitants living on a wide range of dead plant and animal matter.
Contrary to modern forms, the female roachids all have a well-developed external ovipositor, a primitive insect trait. They probably inserted eggs singly into soil or crevices. The egg pods, called ootheca, seen in modern cockroaches and their relatives is a new shared trait separating them from their primitive ancestors. Some of the roachid species could reach relatively large sizes compared to most of their modern relatives, like the Carboniferous Archimylacris and the Permian Apthoroblattina, the latter who could reach 50 mm in body length. However, none that we know of reached near the size of today's largest tropical species, the modern 'giant cockroaches', such as the famous Hissing Cockroach.