ago. Priscoculex burmanicus can be definitively assigned to Anophelinae, one of the two subfamilies of mosquitoes alongside Culicinae, indicating the split between these two subfamilies occurred over 99 million years ago. Molecular estimates suggest that the split between the two subfamilies occurred 197.5 million years ago, during the Early Jurassic, but that major diversification did not take place until the Cretaceous. The mosquito Anopheles gambiae is currently undergoing speciation into the M(opti) and S(avanah) molecular forms. Consequently, some pesticides that work on the M form no longer work on the S form. Over 3,500 species of the Culicidae have already been described. They are generally divided into two subfamilies which in turn comprise some 43 genera. These figures are subject to continual change, as more species are discovered, and as DNA studies compel rearrangement of the taxonomy of the family. The two main subfamilies are the Anophelinae and Culicinae, with their genera as shown in the subsection below. The distinction is of great practical importance because the two subfamilies tend to differ in their significance as vectors of different classes of diseases. Roughly speaking, arboviral diseases such as yellow fever and dengue fever tend to be transmitted by Culicine species, not necessarily in the genus Culex. Some transmit various species of avian malaria, but it is not clear that they ever transmit any form of human malaria. Some species transmit various forms of filariasis, much as many Simuliidae do. Taxonomy Family Mosquitoes are members of a family of nematoceran flies: the Culicidae (from the Latin , genitive , meaning "midge" or "gnat"). Superficially, mosquitoes resemble crane flies (family Tipulidae) and chironomid flies (family Chironomidae). Subfamilies Anophelinae Culicinae Genera Mosquitoes have been classified into 112 genera, some of the more common of which appear below. Aedeomyia Aedes Anopheles Armigeres Ayurakitia Borachinda Coquillettidia Culex Culiseta Deinocerites Eretmapodites Ficalbia Galindomyia Haemagogus Heizmannia Hodgesia Isostomyia Johnbelkinia Kimia Limatus Lutzia Malaya Mansonia Maorigoeldia Mimomyia Onirion Opifex Orthopodomyia Psorophora Runchomyia Sabethes Shannoniana Topomyia Toxorhynchites Trichoprosopon Tripteroides Udaya Uranotaenia Verrallina Wyeomyia Species Over 3,500 species of mosquitoes have thus far been described in the scientific literature. Genomics An analysis by Matthews et al. 2018 suggests mosquito species all carry a large and diverse number of transposable elements. Morphology As true flies, mosquitoes have one pair of wings, with distinct scales on the surface. Their wings are long and narrow, as are their long, thin legs. They have