Cretomerobius disjunctus is known from the holotype specimen found in the Aptian age Bon–Tsagan site,[1] one of the richest insect fossil locations in Mongolia. Bon Tsagan preserves lacustrian sediments of a mountain lake.[2] The genus and type species were first described by Alexandr G. Ponomarenko in a 1992 paper on the fossil Neuroptera faunas of Mongolia, who named the species C. "distinctus", and which was later amended to C. disjunctus as a lapsus calami.[1]
At the time of the species description, placement of Cretomerobius within Hemerobiidae was uncertain. The overall venation of the wings did exclude the genus from a majority of the currently defined subfamilies; specifically Adelphohemerobiinae, Berothimerobiinae, Carobiinae, Notiobiellinae, Sympherobiinae, Psychobiellinae, Hemerobiinae, and Microminae. Makarkin et al suggested the possibility that Cretomerobius is an early offshoot genus. It would be near the start of the subfamily group consisting of Drepanacrinae, Megalominae, and Drepanepteryginae; but until more specimens are found and described, the placement could not be resolved.[1]
Description
In general, wings of Cretomerobius show a distinct forking group of the Radial vein into three branches: ORB1, ORB2, and ORB3. The ORB1 vein has a number of pectinate branches which split from the ORB1 vein and angle to the apical area of the wing. Additionally the cubital-proximal, or CuP vein, forms a deep fork and the median vein forks proximally.[1] The forewing of C. wehri is missing portions of the apical margin and small sections from along the fore and hind margins. The wing is estimated to have been 9 mm (0.35 in) by 4.0 mm (0.16 in) at its widest. The two species are distinguished by two characters. Notably, the geographic and temporal distance between the two fossils suggests they are separate species. Additionally to the temporal disjunction, the wings differ in the fusing of the Radial and Subcostal veins. The two veins in C. disjunctus fuse near the apex of the wing forming a single vein before the wing edge. However, in C. wehri, the two veins do not fuse and stay separate the whole length of the wing.[1]
References
^ abcdefgMakarkin, VN; Archibald, SB; Oswald, JD (2003). "New Early Eocene brown lacewings (Neuroptera: Hemerobiidae) from western North America". The Canadian Entomologist. 135 (5): 637–653. doi:10.4039/n02-122. S2CID53479449.
^Archibald, SB; Bradler, S (2015). "Stem-group stick insects (Phasmatodea) in the early Eocene at McAbee, British Columbia, Canada, and Republic, Washington, United States of America". Canadian Entomologist. 147 (6): 1–10. doi:10.4039/tce.2015.2. S2CID86608533.
^Vladimir N. Makarkin; Sonja Wedmann; Thomas Weiterschan (2016). "A new genus of Hemerobiidae (Neuroptera) from Baltic amber, with a critical review of the Cenozoic Megalomus-like taxa and remarks on the wing venation variability of the family". Zootaxa. 4179 (3): 345–370. doi:10.11646/zootaxa.4179.3.2. PMID27811679.