Global paleobiogeography of Albian—Cenomanian(mid-Cretaceous)marine ostracods

Despite their potential for providing important information for paleobiogeography,studies using ostracod assemblages compiled from global datasets have been scarce so far.In this study,the paleogeographic implications of the relationship between different ostracod assemblages are analyzed and discussed for the Albian and Cenomanian.We compiled an ostracod dataset at the genus level,with 168 genera for the Albian and 174 for the Cenomanian,to which different multivariate statistical methods of grouping were applied.The affinity between different ostracod assemblages from different regions allowed for the delineation of 30 operational geographic units(OGUs)for the Albian,and 32 OGUs for the Cenomanian,grouped in three paleobiogeographic units(PBUs;Megatethys,Persia,and Austral)and one sub-unit(PBSU;Maghreb associated to the Megatethys).The Maghreb PBSU showed minor changes between the Albian and Cenomanian.The relationship among the OGUs grouped in each PBU is related to different factors,such as eustatic sea level events,similar climatic zones,and marine current circulation patterns.A relationship was observed between the Gabon and Nigeria OGUs with the Persia PBU,which suggests a direct east—west connection between them during the Cenomanian.The affinity observed in the Austral PBU between the South American,South African,and Australian regions during the Albian can be explained by their relative geographic isolation due to the Walvis Ridge barrier.The eventual flooding of this barrier led to the relationship observed between the SE Brazilian and Bolivian regions with the Austral PBU.Finally,the data also suggested that the separation of the Indian subcontinent from the Austral PBU took place during the Cenomanian.

The Impact of Some Environmental Factors on the Distribution of the Benthic Ostracod Species from of Safaga Island, Red Sea, Egypt

The benthic ostracods of Red Sea of Egypt have received little attention in ecological studies. Temperature, depth, salinity, dissolved oxygen, pH, conductivity, and other environmental variables all have an impact on benthic ostracods. This study aimed to determine the influence of environmental parameters on the distribution of benthic ostracods by determining the similarity and dissimilarity between the eight collection sites, investigating the regional distribution form by accomplished Multidimensional Scaling (MDS), and recognizing the percentage of the influence of each species on the resemblances and variances within the clusters formed by SIMPER analysis, determining the relationships between depth and other factors by Spearman’s rank correlation coefficient. A total of 43 ostracod species had been identified. According to the frequency index, a single species was rare, six were common and the remaining species (36) were dominant. Seven ostracods species were found across all sites and Cytherelloidea sp. was found in two. The abundance and richness of ostracod species were correlated positively with water temperature, dissolved oxygen, organic matter, salinity, and calcium carbonate. The cold water is preferred by the ostracods Cylindroleberis vix and Prionotoleberis lux and the warm water is favored by podocopid ostracods. The findings of this study will aid in the identification of ostracod species, as well as understanding the characteristics and ecological variables in this zone of the Red Sea in Egypt. The current investigation is an attempt to shed the light on the features of ostracods that live on the east side of Safaga Island.