Hukam Singh

A new genus and species of fossil pseudoscorpion (Arachnida: Pseudoscorpiones) from the Eocene amber of Western India

The Palaeogene biota and the palaeoenvironmental history from the low latitudes are remarkably well–preserved in theopen–cast lignite deposits from Western India. Lignite sequences of the Cambay Shale Formation (Gujarat) have been a majorsource to understand the concept of early evolution of fossils including flora, arthropods, vertebrates fauna, and several aquaticforms during the Early Eocene. The study deals with an extensive record of amber inclusions and extracted pollen, vertebratefragments, dinoflagellate cysts and Carbon isotopes from the lignite and associated sediments from the Tarkeshwar Lignite Mineto add insights into the palaeoenvironment and depositional conditions of the Cambay Basin during the Early Eocene period. Thecurrent study demonstrates that throughout the late Palaeocene and early Eocene epoch, the palaeoenvironment changed fromlow land, marshy (lower portion), to shallow marine environment, presumably due to hyperthermal event PETM (middle part).Age diagnostic taxa, viz. Auxiodinium longispinosum, Apectodinium parvum and early wetzelielloid (Vallodinium? sp.) excursionprovide late Palaeocene–early Eocene period (~56–53 Ma) for the dinocyst interval in the middle part of the section. A pronouncednegative Carbon Isotope Excursion (CIE) in the middle part is correlated to the second Eocene Thermal maximum (53.7 Ma),which is a globally recorded hyperthermal event. During the ETM–2 warming, the rise in pCO2 caused warm, humid conditionsas well as a rise in sea level, which may have contributed to the establishment of constrained shallow marine environments in theexamined middle unit sedimentary succession. Floral (spore–pollens, leaf, wood, seed, fruits) and faunal assemblages (Crocodiles,fish remains, amber insects) revealed the prevalence of a dense tropical luxurious rain forest (floral and faunal) near shore duringthe ETM–2 in the Tarkeshwar Lignite Mines, Cambay Basin.

The family Dolichopodidae (Diptera) from the Eocene amber of the Cambay and Kutch, India is reviewed. Based on a sample of 38 inclusions, the fauna preserved in amber reveals that the family was well-differentiated by early the Eocene. Palaeomedeterus cambayensis Bickel sp. nov. is described and provisionally assigned to the Peloropeodinae, and is congeneric with European Baltic amber species, suggesting the genus was widespread for a considerable time period in both Europe and India. Two small-sized new monotypic genera are also described, Gujaratmyia rotunda Bickel gen. et sp. nov. and Rajpardia grimaldii Bickel gen. et sp. nov. Also included are undescribed members of the dolichopodid subfamilies Diaphorinae and Medeterinae, and unplaced species. The Baltic amber species Prohercostomus noxialis (Meunier, 1907) is regarded as the new senior synonym of Sympycnites primaevus Grimaldi & Cumming, 1999, described with a mistaken provenance of Cretaceous Lebanese amber.

A new species Sycorax longistyla has been recovered in amber from the Tadkeshwar Lignite Mine, Cambay Basin, Gujarat. It belongs to the Sycoracinae, a subfamily of tiny flies, some of which prey on amphibian blood, well-preserved in the Early Eocene Cambay amber. Females of most species have functional mandibles. The new species is distinguished from the extant and extinct representatives by possessing an elongate tubular gonocoxite with a large internal lobe, the gonostylus is curved and longer than the gonocoxite and bears a strong apical spine 0.6 times the length of the gonostylus. The species occurred in sludge-based peat bog spring habitats that existed in the Early Eocene tropical angiosperm Cambay forest.

Micro and macrofossil assemblage have been recovered and documented from the lignite beds of the Vastan lignite mines, Cambay Basin, Gujarat. These are extracted after dissolving amber pieces inclusive of pollen spores, epiphyllous fruiting fungal bodies, algal elements, insect fossils with some unidentified biotic groups. Of these, the major dominant flora belongs to angiosperm origin, in accompaniment to pteridophyte spores and fungal elements. Recorded palynotaxa viz. Proxapertites, Spinizonocolpites, Neocouperipollis and Acanthotricolpites are significant elements for tropical humid vegetation. Rich terrestrial amber palynomorphs and palynodebris suggest proximity source vegetation. Characteristic biotic interactions within the dense evergreen tropical rain forest environment is suggestive of mutual association among groups during the Early Eocene and share close affinities with those of Kutch and Barmer, Bikaner and Nagaur basins.

A fossil of a mayfly nymph that shows similarities with the modern genus Teloganella Ulmer, 1939 of the family Teloganellidae is recorded for the first time from the Indian subcontinent. It is systematically described from the Gurha lignite mine of Bikaner, Rajasthan which belongs to the Palana Formation (late Paleocene-early Eocene). As assignment of the fossil to a modern species of Teloganella is difficult due to indistinguishable location of gills in the impression, a new species, Teloganella gurhaensis Agnihotri et al., sp. nov. is instituted to include this fossil naiad resembling the extant Teloganella.

Indian Eocene amber, like other dammar-type fossil resins, has a unique feature where inclusions are easily extracted with organic solvents. This allows for a comparison of palynological assemblages embedded in the amber with those in associated sediments. Pollen assemblages extracted from the amber are rich with diverse angiosperm flora dominated by Liliacidites sp., Palmidites elongatus, Palmidites naviculus, Monocolpopollenites sp., Proxapertites cursus, Proxapertites sp., Albertipollenites crassireticulatus, Polybrevicolporites cephalus and Dipterocarpuspollenites retipilatus. Besides, pteridophyte spores, bryophytes, algal and a variety of fungal. In the associated sediments, mainly represented by clays carbonaceous shales and lignite, pollens are less diverse and poorly represented (nearly 23%). Palynological assemblages were recorded in both amber and in the sediment samples, but the palynological assemblage extracted from the amber is more diverse and better preserved. Resin, on the amber-producing trees, was able to intercept pollen from the full forest column from the canopy to the upper canopy to the soil to a taphonomic bias in comparison to sediment-derived palynological assemblages. The exceptionally well-preserved and diverse amber flora exhibits a tropical humid moist environment and shows the existence of Palm and Dipterocarpaceae-dominated deciduous forest (including herbs and shrubs) along with other mixed angiospermic, pteridophytic and bryophytic vegetation, growing near the seashore.

The first representative of Tipulomorpha in Early Eocene Cambay amber from India is described. The new find belongs to the genusDicranomyiain the family Limoniidae. This genus has a worldwide distribution today and is relatively common in Eocene Baltic amber. A new species belonging to the subgenusDicranomyiais described asDicranomyia(Dicranomyia)indicasp. nov.