Roachoid

File:Anthracoblattina ensifera.png (Phyloblattidae) in ventral view, showing prominent external ovipositor]]

Cockroaches are popularly thought to be an ancient order of insects, with their origins in the Carboniferous.Guthrie, D. M. & A. R. Tindal (1968): The Biology of the Cockroach. St. Martin's Press, New York 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 and termites but also of mantises.Grimaldi, D (1997): A fossil mantis (Insecta: Mantoidea) in Cretaceous amber of New Jersey, with comments on early history of Dictyoptera. American Museum Novitates 3204: 1–11 The origin of these groups from a blattopteran stock are now generally thought to be in the Early Jurassic; the earliest modern cockroaches appeared during the Late Jurassic.{{Cite journal|last1=Vršanský |first1=P. |last2=Palková |first2=H. |last3=Vršanská |first3=L. |last4=Koubová |first4=I. |last5=Hinkelman |first5=J. |year=2022 |title=Mesozoic origin-delayed explosive radiation of the cockroach family Corydiidae Saussure, 1864 |journal=Biologia |volume=78 |issue=6 |pages=1627–1658 |doi=10.1007/s11756-022-01279-1 |s2cid=254479766 }} Thus, the “Palaeozoic cockroaches” are not cockroaches per se, but a paraphyletic assemblage of primitive relatives.Grimaldi, D. & M. S. Engel, Michael (2005): Evolution of the Insects, Cambridge University Press, {{ISBN|0-521-82149-5}} The youngest known roachoids date to the Cretaceous, by which time they were rare compared to modern cockroaches.{{Cite journal |last1=Li |first1=Xin-Ran |last2=Huang |first2=Di-Ying |date=2023-03-29 |title=Atypical 'long-tailed' cockroaches arose during Cretaceous in response to angiosperm terrestrial revolution |journal=PeerJ |language=en |volume=11 |pages=e15067 |doi=10.7717/peerj.15067 |issn=2167-8359 |pmc=10066690 |pmid=37013144 |doi-access=free }}

The fossils assigned to the "roachoids" 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.Schneider, J. (1983): Die Blattodea (Insecta) des Paleozoicums, Teil II, Morphogenese des Flügelstrukturen und Phylogenie. ''Freiberger Forchnungshefte, Reie C 391. pp 5–34 Like modern cockroaches, the roachoids were probably swift litter inhabitants living on a wide range of dead plant and animal matter.

Contrary to modern forms, female roachoids all have a well-developed external ovipositor. They probably inserted eggs into substrate. The egg pods, called ootheca, seen in modern dictyopterans is a new shared trait (synapomorphy) separating them from their primitive ancestors.{{Cite journal |last1=Hörnig |first1=Marie |last2=Haug |first2=Carolin |last3=Schneider |first3=Jörg |last4=Haug |first4=Joachim |date=2018 |title=Evolution of reproductive strategies in dictyopteran insects – clues from ovipositor morphology of extinct roachoids |url=https://www.app.pan.pl/article/item/app003242016.html |journal=Acta Palaeontologica Polonica |volume=63 |doi=10.4202/app.00324.2016 |issn=0567-7920|doi-access=free }} Some of the roachoid species could reach relatively large sizes compared to most of their modern relatives, like Progonoblattina{{Cite journal|last=Sellards|first=Elias Howard|date=1903-04-01|title=Some new structural characters of Paleozoic cockroaches|url=https://www.ajsonline.org/content/s4-15/88/307|journal=American Journal of Science|language=en|volume=s4-15|issue=88|pages=307–315|doi=10.2475/ajs.s4-15.88.307|bibcode=1903AmJS...15..307S|issn=0002-9599}} and Necymylacris{{Cite thesis|title=Stratigraphy and paleontology of Cemetery Hill (Desmoinesian-Missourian: Upper Carboniferous), Columbiana County, eastern Ohio|url=https://etd.ohiolink.edu/apexprod/rws_olink/r/1501/10?p10_etd_subid=68187&clear=10|publisher=The Ohio State University|date=2004|language=en|first=Cary Ray|last=Easterday}}{{Cite journal|last1=Schneider|first1=Joerg|last2=Scholze|first2=Frank|last3=Germann|first3=Sebastian|last4=Lucas|first4=Spencer|date=2021-04-16|title=THE LATE PENNSYLVANIAN NEARSHORE INSECT FAUNA OF THE KINNEY BRICK QUARRY INVERTEBRATE AND VERTEBRATE FOSSIL LAGERSTÄTTE, NEW MEXICO|url=https://www.researchgate.net/publication/350896849|journal=Bulletin of the American Museum of Natural History|volume=84}} from Carboniferous reach around {{convert|9|cm|in|frac=2}} in total length, and the largest Opsiomylacris having wings reaching {{convert|7.5|cm|in|frac=2}}, close to modern largest cockroach Megaloblatta longipennis.{{Cite journal |last1=Schneider |first1=Joerg W. |last2=Rößler |first2=Ronny |date=2023 |title=The Early History of Giant Cockroaches: Gyroblattids and Necymylacrids (Blattodea) of the Late Carboniferous |journal=Diversity |language=en |volume=15 |issue=3 |pages=429 |doi=10.3390/d15030429 |issn=1424-2818 |doi-access=free }}

Some roachoids strongly deviated from a cockroach-like form. Ensiferoblatta and Proceroblatta from the Burmese amber of Myanmar, around 100 million years old, among some of the youngest known "roachoids" have a morphology resembling that of tree crickets.

• Archimylacris

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{{Orders of Insects|extinct}}

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Category:Extinct insect orders

Category:Prehistoric insects

Category:Carboniferous first appearances

Category:Lopingian extinctions

Category:Paraphyletic groups

Category:Prehistoric arthropod orders