Jurassic-Cretaceous conchostracan faunas from Asia and South America: relationship, paleogeography and probable evolution-dispersion pattern.

GALLEGO, O.F.; SHEN, Y.B.

Córdoba

Congreso; IX Congreso Argentino de Paleontología y Bioestratigrafía; 2006

Since the pionner works of the chinese researchers in the 20th century (Zhang et al., 1976; Chen and Shen, 1985) and them join new contributions with southamerican teams in this century (Shen et al., 2001, 2004; Gallego and Shen, 2004; Rohn et al., 2005), mayor evidence reflected the close relationship between the Asian and Gondwanean conchostracan faunas (A-Gcf) mainly during the Jurassic-Cretaceous times. Nevertheless, the Triassic associations from Argentina and Chile show the presence of eosestheriid forms (Menucoestheria) close related with others from the Middle Jurassic from ?Argentina and Antarctica (Carapacestheria), also from Europe and China and with Upper Jurassic-Lower Cretaceous forms from China. Those wide distribution, their affinities and relationships between all of them are still doubtfull. The first A-G related faunas was the record of the Family Ulugkemiidae in the Triassic from Argentina (Gallego and Melchor, 2000) and Kenya (Shen, 2006), until this moment only present in the Upper Paleozoic from Asia. Others, Asian-Gondwanean related members are the palaeolimnadiopseid Endolimnadiopsis with records in the Upper Permian of Rusia and the Middle-Upper Triassic of Argentina (Gallego, 2005). On the other hand, the Triassic pemphilimnadiopseid Challaolimnadiopsis has related forms in the Upper Paleozoic and Triassic from Asia. Recently the authors describe many new species with joined record in the Jurassic-Cretaceous rocks from Southern South America and specially from China. They include members of the families: Fushunograptidae (Orthestheria-Migransia) from the Upper Jurassic-Lower Cretaceous from Uruguay with related forms in the Upper Jurassic-Lower Cretaceous from Africa and China; Anthronestheriidae (Pseudoestherites) from the Lower Cretaceous from Argentina and with related species in the Lower Cretaceous from China and the Family Polygraptidae (Dendrostracus) from the Lower Cretaceous from Argentina with close taxa in the Mesozoic from Europe and Asia (Prámparo et al., 2005). More recently, a member of the Family Jilinestheriidae (Bauruestheria) is reported from the Upper Cretaceous from Brazil, that evidence close affinities with Upper Cretaceous forms from China and Africa. From the paleogeographic point of view, due to it age and phylogenetical relations some taxa as Orthestheria (Migransia) ferrandoi from Uruguay, or other undiscover form would be the ancestral of other genus or branch lineage as Bauruestheria (from Brazil) and Plectestheria (from China). Still unpublish, is the record of a Lower-Middle Jurassic guide genus from China (Eosolimnadiopsis-Palaeolimnadiopseidae) in the Middle Jurassic from Argentina. Those faunal similarities between northern and southern hemispere, allow us to propose a model of paralel evolution for the fossil conchostracan faunas following origination from a common ancestor.       Chen, P.J. and Shen, Y.B. 1985. An introduction to fossil Conchostraca. Beijing: Science Press, China, 241 p. Gallego, O.F. 2005. First record of the family Palaeolimnadiopseidae (Defretin-LeFranc, 1965) from the Triassic of Argentina. Journal of South American Earth Sciences 18: 223-231. Gallego, O.F. and Melchor, R.N. 2000. La Familia Ulugkemiidae Novojilov,1958 (Conchostraca) en el  Triásico de la Argentina. Implicancias Paleobiogeográficas. Ameghiniana 37: 47-58. Gallego, O.F. and Shen, Y.B. 2004. A new conchostracan form from La Amarga Formation (Neuquen Basin), Argentina. Revista Brasileira de Paleontología 17: 5-12. Prámparo, M., Ballent, S., Gallego, O.F. and Milana, J.P. 2005.Paleontología de la Formación Lagarcito (Cretácico Inferior alto), provincia de San Juan, Argentina. Ameghiniana 42: 93-114. Rohn, R., Shen, Y.B. and Dias-Brito, D. 2005. A new Coniacian-Santonian conchostracan genus from the Bauru Group, south-east Brazil: Taxonomy, palaeobiogeography and palaeoecology. Cretaceous Research 26: 581-592. Shen Y.B., 2006. A new genus of Kenyaestheria (Crustacea: Conchostraca) from the Lower Triassic of Kenya. Acta Palaeontologia Sinica 45: 175-181. Shen, Y.B., Gallego, O.F. and Martínez, S. 2004. The conchostracan subgenus Orthestheria (Migransia) from the Tacuarembó Formation (Late Jurassic – ?Early Cretaceous, Uruguay), with notes on its geological age. Journal of South American Earth Science 16: 631-638. Shen, Y.B., Gallego, O.F. and Zavattieri, A.M. 2001. A new conchostracan genus from Triassic Potrerillos Formation, Argentina. Acta Geologica Leopoldensia 24:,227-236. Zhang, W.T., Chen, P.J. and Shen, Y.B. 1976. Fossil Conchostraca of China. Beijing, Science Press, 325 p.