Diagnosis. Smooth, very low trochospiral test, finely perforate  to macroperforate test wall, crater-like  pores on the earlier chambers  and imperforate  peripheral  band  throughout the final whorl.

Description. Test low to very low trochospiral with globular to  subglobular   chambers,  separated  by  straight,  incised  and radial sutures. Test biconvex, nearly symmetrical in edge view. Periphery broadly rounded with a wide imperforate  band throughout the final whorl. Main  aperture  is in the shape of a low to medium high arch, peripheral-umbilical in position  and bordered by an imperforate  lip. Test wall calcitic, hyaline, perforate, with perforation diameters  ranging between 1.7 and 3.1 mm. Test surface smooth.

Remarks.  Liuella nov.  gen. differs from  any  other  hedbergellid genus by presenting an imperforate  peripheral band throughout the  final  whorl.  It  also  differs from  Clavihedbergella  Banner   and  Blow  of  the  upper   Albian   by  its  finely perforate   to  macroperforate  test  wall  and  lack  of  radially elongate chambers. Seemingly, there is a gap that separates the stratigraphic ranges of the two genera and that spans the Cenomanian-early Santonian interval. Herein, Liuella is included  within  the  Subfamily   Hedbergellinae—despite the presence of the imperforate  peripheral band—due  to the strong general resemblances  with the hedbergellid  group  rather  than with the ticinellids of the Subfamily Ticinellinae, such as Biticinella, Clavihedbergella, Claviticinella and Ticinella (Loe- blich and Tappan, 1987, p. 466). Pore-size terminology  is that used   by  the   Mesozoic   Planktonic  Foraminifera  Working Group   (2006,  coordinator  B.  T.  Huber):   1.0  to  2.5 mm  is considered  finely  perforate,  and  over  2.5 mm  is  considered macroperforate.

Species included. Liuella falklandica nov. sp.

Phylogenetic relationships. The low to very low trochospire, the shape and position of the aperture, which touches the periphery,  and the size of the umbilical area, which is approximately  one third of the maximum test diameter, suggest  that  this  genus  evolved  from  Hedbergella  planispira or related species of the Santonian, such as H. atlantica Petters,1977. Another  species with close morphological features to Liuella falklandica n. sp. is Hedbergella punctata Michael, 1973, which was originally described from the upper  Albian sediments  of the  southern  United  States  (Texas) by Michael (1973)  and  subsequently   reported   from  the  Great   Artesian Basin of northern Australia (Playford and others, 1975). This is a small-sized species (Dmax=0.150 mm), with relatively large- sized  pores   and   low   trochospire.  The   presence   of   an imperforate  peripheral  band  throughout the  final  whorl,  the large-sized pores situated  in the center of crater-like  structures and lower trochospire differentiate  L. falklandica from H. punctata. However, there is a significant stratigraphical interval that  separates  the two species without  a record of similar tests and  spanning  the Cenomanian and  Santonian. The genera of the Family Hedbergellidae  that have an imperforate  peripheral band  and  that   have  traditionally  been  included  within  the  Subfamily Rotundininae Bellier and Salaj, 1977 of the Albian- Coniacian  comprise  two  genera:  Falsotruncana   Caron,   1983 and Praeglobotruncana Bermudez, 1952 (Loeblich and Tappan,1987, p. 462–463). Both of these have a truncated and keeled periphery and apparently evolved from globular-chambered hedbergellids (Caron  and Spezzaferri, 2003). Accordingly, a phylogenetic   relationship  between   either   Falsotruncana   or Praeglobotruncana and Liuella nov. gen., which does not show keels, is not plausible (Fig. 2).

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