Palaeozoic roots of the sigilliid ostracods

Podocopine ostracods rapidly increased in species diversity after the Palae ozoic, and 32 out of the 36 podocopine families are extant (Whatley et al., 1993), but the phyletic origins are known for only a few. The Sigilliacea are unique in having a long and detailed fossil record. The Sigilliidae kno wn from the recent and Mesozoic faunas differ from others ostracods in havi ng large adductor muscle scars with many spots, a character typical rather to Palaeozoic forms. Paleozoic Microcheilinellidae were morphologically clo se to the sigilliids, but details of their hingement and carapace margin st ructures were unknown until now. Silicified specimens of Microcheilinella m endelgrammi, new species, from the Early Carboniferous of southern China an d Microcheilinella mandelstami, from the Middle Devonian of north-western P oland show merodont hingement and narrow calcified inner lamella. This make s their relationship to the Mesozoic, Tertiary, and recent sigilliids Saipa netta, Cardobairdia, Sigillium, and Kasella likely. The sigilliid lineage w as thus established already in the Devonian. Tubulibairdia, with adont hing ement and tubulous shell wall, and Microcheilinella s. s., with merodont hi ngement and no tubules, are distinct genera in different families. (C) 2001 Elsevier Science B.V. All rights reserved.