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    STUDIA GEOLOGIA - Ediţia nr.2 din 2013  
         
  Articol:   NEW ADVANCES IN UNDERSTANDING THE HETEROHELICID PLANKTIC FORAMINIFER EARLY EVOLUTION.

Autori:  .
 
       
         
  Rezumat:  Three Late Cretaceous lineages of heterohelicid planktic foraminifera, which evolved in the proximity of the Cenomanian/Turonian boundary, bring new data in understanding the group evolutionary history. Lunatriella Eicher and Worstell, 1970a is a directional lineage of late Cenomanian-early Turonian age, which gradually develops peripheral backward extensions in the last-formed chambers. Steineckia Georgescu, 2009a of the Turonian is the earliest heterohelicid lineage that evolved ornamentation consisting of pore mounds; a gap spanning the latest Turonian-early Santonian separates it from Laeviheterohelix Nederbragt, 1991 of the late Santonian-Campanian, the second lineage that developed ornamentation consisting of pore mounds. Pseudoplanoglobulina Aliyulla, 1977 evolved in the early Turonian and is the first heterohelicid lineage that developed multichamber growth in the adult stage; it became extinct in the Santonian. The three directional lineages show that the iterative and convergent evolution patterns occur extensively in the early heterohelicid history.

Key words: planktic foraminifera, Late Cretaceous, evolutionary classification
 
         
     
         
         
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