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Revista mexicana de ciencias geológicas
On-line version ISSN 2007-2902Print version ISSN 1026-8774
Abstract
LIANG, Jun-Hui; VRSANSKY, Peter and REN, Dong. Variability and symmetry of a Jurassic nocturnal predatory cockroach (Blattida: Raphidiomimidae). Rev. mex. cienc. geol [online]. 2012, vol.29, n.2, pp.411-421. ISSN 2007-2902.
Cockroaches are as of yet the only animal group with a fossil record complete enough to reveal the quantitative changes of individual intraspecific variability over a considerable interval of time (320 Ma). Ninety three individuals of the first known nocturnal and/or crepuscular carnivorous cockroach Divocina noci gen. et sp. nov. of the family Raphidiomimidae (Middle Jurassic Jiulongshan Formation; Daohugou, Inner Mongolia Province, China) now reveal the comparison of variability and symmetry of right and left wings separately. The sole significant difference is the more pronounced variability of the anterior part (involved in flight) of the leftforewings, which may be the consequence of the superposition of the left wing and its protective function associated with vein reorganizations. The overall variability coefficient of the number of veins in the distal forewing margin and total number of veins at the margin (CVtotal= 7.65; hindwing CVtotal= 7.54) was low when compared with the wing centre, which together with wing symmetry suggest comparatively good flight. The total number of veins is in perfect congruence with the variability of Fortiblatta cuspicolor Liang, Vrsansky and Ren, 2009- another raphidiomimidfrom the same locality (CVtotal = 7.70; hind wing CVtotal= 7.33). In spite of nearly identical overall variability, data for respective veins vary up to 30%. Different also is the mean asymmetry expressed as the difference in the number ofveins meeting at the margin between the respective sides (4.7% of Divocina vs 7.0% of Fortiblatta cuspicolor). Itfollows that the general variability is to a large extent independent of variability of respective characters as well as of symmetry values.
Keywords : insects; fossil cockroaches; Bathonian; Middle Jurassic; nocturnal; Raphidiomimidae; predators.
