pars 1890  Popanoceras.- Karpinski: 170.
pars 1903  Popanoceras.- Smith: 132.
pars 1931  Stacheoceras.- Tumanskaia: 22.
pars 1937  Marathonites.- Plummer & Scott: 137.
pars 1949  Marathonites (Almites) Tumanskaia: 68.
pars 1963  Marathonites (Almites).- Tumanskaia: 55.
pars 1960  Marathonites (Almites).- Ruzhentsev: 226.
pars 1950  Peritrochia.- Miller & Downs: 210.
pars 1950  Marathonitea (Marathonites).- Ruzhentsev: 193.
        1967  Cardiella Pavlov: 75
pars 1978  Cardiella.- Bogoslowskaia: 58.
        1981  Cardiella.- Leonova: 38.
        1987  Cardiella.- Glenister & Furnish: 983
        1989  Cardiella.- Leonova: 149.
        2000  Cardiella.- Leonova & Boiko: 32.
        2004  Cardiella.- Leonova: S78.

Type species: Cardiella gracia Pavlov, 1967, p. 76.

[Bogoslovskaia, 1978, p. 58]: Shell predominantly small, pachyconic or subdiscoidal, stronly involute, with very narrow
and even closed umbilicus. In the terminal stage it is usually heart-shaped or irregularly oval. The ornament consists of
narrow lamellae, which are directed forward from the umbilical border, but thereafter are deflected backwards in the
middle part of the lateral side, forming a broad ventral sinus. Appreciable thickening of the shell layer that is not
expressed at the surface, but is clearly apparent in section, is to be seen in the region of the umbilical border.
The suture consists of 20 to 22 lobes. Ventral lobe broad, divided by a high median saddle into two broad basally
bicuspid branches. First to third outer lateral lobes clearly tricuspid, fourth bicuspid or most often very
complex in outline owing to the appearance of numerous denticles on the inner side. Umbilical lobe simple or tricuspid.
Dorsal lobe narrow and tricuspid. Firts to third inner lateral lobes basally bicuspid. Fourth lobe very small, fifth lobe (if
developed) simple, considerably smaller than the first three, separated by a broad saddleDistinguished from
Demarezites and Hyattoceras by the simpler suture: tricuspid instead of multicuspid first outer lateral
lobes. Distinguished from Peritrochia by the smaller number of lobes (20 to 22, as against 24), but which are more
dissected.

[Glenister & Furnish, 1987, p. 983]: Small to intermediate size marathonitids (15-40 mm mature diameter) characterized
by conspicuous geniculate coiling of the ultimate volution, and by terminal thickening of the shell that restricted the
mature aperture and sealed the umbilicus. External lateral lobes generally regularly  tridentate, and dorsal lobe narrow
and weakly tridentate.

[Leonova, 1989, p. 149]: Conch pachycone or subdiscone, completely involute. Umbilicus extremely tight or closed.
In terminal stages heart-shaped, irregularly triangular or oval, which is related to an increase in height and decrease
in venter width 1/3 whorl distance from terminal rim. Living chamber equals one whorl. Thin lamellae or ribs proceed
forward in the umbilical zone, turn backwards in the middle of the lateral sides and form a wide and deep sinus on
the venter. Ribs on the lateral side either bifurcating or intercalating. Considerable thickening of shell in umbilical
area not expressed on conch surface. 20--22 lobes in all. Ventral lobe more or less wide, divided by a high
median saddle in two bifid parts. First three external lateral lobes threefid, as a rule. Fourth lateral lobe can be whole,
bifid or threefid. Umbilical lobe tight, deep, threefid. Fourth and an extremely small fifth (if present) lobe whole,
considerably smaller than first three. Dorsal lobe tight, deep, threefid.