Oscar F. Gallego

Conchostracans and insects from the Upper Triassic of the Biobío river ('Santa Juana Formation'), south-central Chile

Fossil arthropods from Upper Triassic outcrops along the Biobio river, south-central Chile, are reported in this paper. Two species of the order Coleoptera, Ademosyne sp., and Ischichucasyne santajuanaensis gen. et sp. nov. (Permosynidae) are described for the first time for the Triassic of Chile. The conchostracans Menucoestheria terneraensis Gallego and Polygrapta troncosoi (Gallego) comb. nov., are re-examined based on newly collected specimens and scanning electron microscope photographs. A close relation between M. terneraensis and Argentinean and Antarctic species is postulated, with the possibility that Menucoestheria evolved from Euestheria Deperet y Mazeran. Menucoestheria could be the origin of all other Gondwanic eosestherids. The use of Menucoestheria and Polygrapta as fossil guides for continental levels of the Upper Triassic of Argentina and Chile is tentatively proposed. The reported entomofauna, which exhibits close affinities with the Argentinean entomofauna, sharing, for example, the genera Ademosyne and Ischichucasyne, broadens our knowledge of South American arthropod diversity during the Triassic. The presence of the homopteran dysmorphoptilid Bandelnielsenia Martins-Neto and Gallego, the most plesiomorphic of the South American forms, seems fundamental for an understanding of the phylogeny of this important Triassic group.

EOCENE CONCHOSTRACANS FROM THE LANEY MEMBER OF THE GREEN RIVER FORMATION, WYOMING, USA

Abstract Two new species of conchostracans, Cyclestherioides wyomingensis and Prolynceus laneyensis, belonging to the Cyclestheriidae and Lynceidae, respectively, are described from the Eocene Laney Member of the Green River Formation of Wyoming, USA. These are the first Cenozoic fossil conchostracans to be formally reported from North America. Cyclestherioides wyomingensis has a close affinity to the extant Cyclestheria hislopi. The latter is a pan-tropical species, found between approximately 30°N and 35°S. Thus, Cyclestherioides may indicate that the Laney Member was deposited in a subtropical setting. The conchostracans and associated fauna of the Laney Member suggest that this member was deposited nearshore in a shallow lake. The concept of Cyclestherioides is emended and some fossil species referred to this genus are revised.

The First Record of the Family Fushunograptidae (‘Conchostraca’, Spinicaudata) from the Cañadón Asfalto Formation (Upper Jurassic), Patagonia, Argentina

Abstract. A description is provided for Wolfestheria smekali gen. and sp. nov., a new member of the family Fushunograptidae, from the “Estancia La Sin Rumbo” locality in the Puesto Almada Member of the Cañadón Asfalto Formation. Assignment to the family Fushunograptidae is supported by evidence from detailed scanning electron microscope studies of this species. An assessment of the complex carapace ornamentation is also provided, as W. smekali exhibits an array of ornamentations that cover the entire carapace surface. These consist of irregular, thick radial lirae with numerous thin cross-bars on the dorsal middle-upper third of the carapace, changing to straight, thick radial lirae with fewer cross-bars restricted to the upper half of the growth band in the ventral third of the carapace, with the interspaces between the radial lirae wider than the lirae themselves, and with the radial lirae terminating in the upper part of the growth bands, where they then enlarge to form a triangular shape upon contact with the following growth line. These characteristics allow us to compare W. smekali with the eosestheriid genera Yanjiestheria Chen and Abrestheria Wang, as well as with the other fushunograptids from the Upper Jurassic to Lower Cretaceous of China such as Cratostracus Huang and Qinghaiestheria Wang. W. smekali is also comparable to fushunograptids and related forms from the Jurassic system of Argentina. The occurrence of W. smekali correlates biostratigraphically with the “Eosestheriopsis dianzhongensis fauna” of China, as well as with other Jurassic faunas from Africa and Europe. This correlation supports a Late Jurassic age for these fossiliferous assemblages (Puesto Almada Member, Cañadón Asfalto Formation) from the province of Chubut, Argentina.

First record of oligocene conchostracans (Tremembé formation, Taubaté Basin) from São Paulo, Brazil

Abstract In this paper the first Oligocene conchostracans are described from the Tremembe Formation (Taubate Basin) of Brazil, these are also the first known Oligocene conchostracans in the world. References to a few other Cenozoic conchostracan discoveries are also discussed. Tremembeglypta saadi nov. gen. et sp. is compared with different members of the family Loxomegaglyptidae, specifically with Paraleptestheria menglaensis Chen, the only member of the family described from the Lower Tertiary of China. Paleobiological and environmental comments about conchostracans and their associated fish fauna are included. Finally, the importance and implication of this find are briefly discussed.