Taxonomy of the clam shrimp Halysestheriidae (Diplostraca: Spinicaudata) from the Upper Cretaceous Nenjiang Formation in central Dayangshu Basin of eastern Inner Mongolia, northeastern China Author LI, GANG text Palaeoentomology 2021 2021-04-29 4 2 156 164 http://dx.doi.org/10.11646/palaeoentomology.4.2.4 journal article 4093 10.11646/palaeoentomology.4.2.4 43c4ba9f-1f5a-47d8-b4bb-a642f0d78bc5 2624-2834 5507750 B023453A-C003-4B0E-8721-744168CBEA14 Family Halysestheriidae Zhang & Chen in Zhang et al ., 1976 Emended diagnosis. Carapaces are ovate, elliptical, rounded, or subquadrate in outline. Umbo bulging, located in the middle or anterior part of the dorsal margin. Growth lines are prominent, with serrated lower margins. Growth bands ornamented with radial lirae, which transition through reticulation to chain-like decoration. The grid arrangement is very regular, with dense chains perpendicular to the growth line. The longitudinal mesh wall is thickened and the mesh becomes narrower and longer, like the chain hole, which becomes a regular, radially arranged discontinuous linear structure on an external mould. Growth bands in the umbonal area ornamented with widely spaced radial lirae, between which short lirae and crossbars occur, and forming fine reticulation. Puncta occur between radial lirae and within reticulation. FIGURE 1. A geological sketch map of the Ganhe area, Oroqen Autonomous Banner, Inner Mongolia to show the fossil locality (after Zhang et al ., 2020 ). Remarks. This family was named by Zhang & Chen ( in Zhang et al ., 1976 ) to include Halysestheria Zhang & Chen in Zhang et al ., 1976 , Brachygrapta Novozhilov, 1954 , Pseudocyclograpta Chang, 1957 , Tylestheria Zhang & Chen in Zhang et al ., 1976 , Aglestheria Chen in Zhang et al ., 1976 . Later, Dictyestheria Chang & Chen, 1964 and Plectestheria Zhang & Chen in Zhang et al ., 1976 were assigned to this family by Li et al . (2009) .