Lower Carboniferous Ostracoda (Beyrichicopida and Kirkbyocopa) from the Bonaparte Basin, northwestern Australia

Beyrichicopids and kirkbyocopes are represented in the Early Carboniferous 
benthic ostracod fauna of the Bonaparte Basin by at least 29 species referable to 18 genera (including two that are probably new, 
but unnamed). The described number of species are distributed among the ostracod families. Of the species described, eight are new (Libumella 
bonapartensis, Welleriella atypha, Malnina spinosa, Coryellina excaudata, C.robertsi, Selebratina serotina, Tetrarhabdus 
dictyon, and Scrobicula inaequalis), eight are closely related to, if not conspecific with, established taxa [Pseudoleperditia cf. 
venulosa, Coryellina cesarensis, Kirkbya aff. lessnikovae, K. aff. quadrata, Amphissites aff. centronotus, A. umbonatus, Kirkbyella
 (Berdanella) quadrata, and Scrobicula aff. inaequalis), and 13 are placed in open nomenclature, most of which are comparable with 
 previously described taxa. The morphological similarities of the extinct Kirkbyacea and the extant Punciacea are discussed, and
  possible homoemorphic resemblances between them are considered. Detailed SEM examination of the reticulation pattern of the 
  kirkbyacean species Amphissites sp.B revealed the results of epidermal cell-division during the ecdysis between the A-I 
  stage and the presumed adult stage. Mitosis of the epidermal cells not only increases the valve surface area, but also 
  initiates carinae by the fusion of adjacent muri of twin fossae. An interim biostratigraphic scheme for the Early 
  Carboniferous sequence of the Bonaparte Basin consists of a succession of eight ostracod assemblages that are based 
  on the first appearance (in ascending order) of the following species: Welleriella atypha, Coryellina robertsi, 
  Shivaella cf. armstrongiana, Coryellina cesarensis,. Malnina spinosa sp. nov., Selebratina serotina, Scrobicula inaequalis
   and A mphissites sp.B. The scale of assemblages is controlled by conodont and foraminiferal zonations, and is calibrated
    against the Dinantian time-scale. So far, the atypha, robertsi and armstrongiana Assemblages have been recognised in 
    the Early Carboniferous (Tournaisian) sequence of the Canning Basin. The major affinities of the Early Carboniferous 
    beyrichicopids and kirkbyocopes from the Bonaparte Basin are with cognate species from Western Europe (Belgium, 
    northern England), the Russian Platform, Kazakhstan, and Tibet. North American affinities are of minor significance. 
    In general terms, the entire Early Carboniferous ostracod fauna from the carbonate shelf sediments of the Bonaparte 
    Basin belongs to the Bairdiacea-Paraparchitacea ecozone, suggesting warm climatic conditions. The Tournaisian (Burt 
    Range Formation; Septimus Limestone) faunas may include ecologically mixed assemblages, i.e., marine nearshore and 
    shallow offshore, but the palaeoecological studies needed to test this model must await the description of the total 
    Early Carboniferous ostracod fauna. The Visean (Utting Calcarenite) Kirkbyacea are as frequent (in species abundance) 
    as the Paraparchitacea, both superfamilies ranking second to the Bairdiacea; a proportion indicative of open-marine 
    shallow offshore conditions.

Tags: AU-NT, AU-WA, Bulletin, Earth Sciences, GA Publication, Published_External, marine, palaeontology
Organization: Geoscience Australia Data