Beu: Evolution of Janthina and Recluzia 
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Age 
m.yr. 
Epoch 
Internal. 
Stages 
N.Z. 
Stages 
Janthinid time ranges 
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Figure 22. Stratigraphical positions and ages of world Janthina fossil localities, correlated with biostratigraphical zonations and geomagnetic 
polarity stratigraphy (normally magnetized intervals in black, reversed intervals in white). Planktonic microfossil zones (based on Blow, 
1969; Wade etal., 2011; Okada and Bukry, 1980: “Nannos”) and geomagnetic polarity stratigraphy all from Gradstein et al. (2012). 
age. Janthina krejcii probably also occurs at Pinheiros, a 
short distance northwest of and at the same elevation as Cre. 
Apparently J. krejcii is more widespread than the present 
data indicate, and its time range is poorly constrained. 
Janthina krejcii has evenly rounded whorls, prominent, 
fine, straight axial ridgelets, and a very low spire similar to 
that of juvenile specimens of J. typica and J. janthina , but 
it completely lacks spiral folds. It possibly evolved from J. 
typica abruptly through a heterochronic process. Janthina 
chavani is not recorded from the Atlantic islands (although 
it possibly occurs at Madeira) so the complete evolutionary 
succession cannot be examined in any one locality or area. 
This leaves several possible phylogenies to be evaluated. 
Coevally with Janthina chavani , J. globosa is recorded 
from two widely separated Piacenzian or Gelasian localities. 
The two early records of J. globosa lie near the equator in 
the central tropics in both main oceans: Luzon, Philippine 
Islands, in the Indo-West Pacific, and Jamaica in the Atlantic. 
In contrast, Pacific records of J. chavani lie in higher latitudes 
to the north and south of the one fossil record of J. globosa. 
Although this latitudinal segregation does not hold in the 
Atlantic, it gives the impression that J. chavani was limited 
in the Pacific to more temperate areas during late Piacenzian 
time, both north and south of the tropics, while J. globosa 
occupied the central tropics. This possibly could represent 
the type of zonal distribution described by Savilov (1969) for 
living species. However, neustonic epitoniids, and especially 
the species extending up to the living fauna, are recorded 
from far too few fossil localities as yet to able to evaluate 
the significance, if any, of this distribution. 
Phylogeny. It is accepted here that Recluzia evolved during 
Holocene time independently of other neustonic Epitoniidae, 
recently enough to have no fossil record. The major question 
remaining is the phylogeny of the species formerly included 
in the genera Janthina and Hartungia. In evaluating the 
several possible phylogenies of Janthina species allowed by 
the history of fossils described above, a few key similarities 
and character changes are significant phylogenetic indicators. 
As recorded below under J. chavani , the most important 
of these is the great similarity between J. chavani and J. 
janthina. These two species are similar in having the outer 
lip sinus limited to the base of the lip, or occupying mainly 
the lower limb of the lip in the case of J. janthina. The sinus 
is symmetrical, with its centre in the centre of the outer lip 
in all other living Janthina species. Janthina janthina and 
J. chavani are also similar in their great variation in shell 
shape, most large specimens tending to be taller and narrower 
than small (young) ones—moderately so in the case of J. 
janthina , but strongly so in the case of J. chavani , although 
shell shape is highly variable in both species. Weak spiral 
grooves in the shell wall also occur below the periphery in 
many specimens of J. janthina (Figs 2 A, D, 4A, 5 A), similar 
to but much weaker than the folds of J. chavani , although 
