Genus
Likharevites Davydov, 1987, emend. Leven
Remarks.
[82] A great deal of Permian sections in the Tethys and South Urals regions
contain fusulinids characterized by a more or less inflated fusiform shell, extremely small
proloculus, tightly coiled juvenarium, widely and loosely coiled following whorls, and thin
septa strongly and as a rule irregularly fluted throughout the whole width and length. Over
many years these fusulinids were referred to the American genus Paraschwagerina
Dunbar et Skinner, 1936. A lot of researchers continue doing this up to now. After the
distinction of Occidentoschwagerina
[Miklukho-Maclay, 1959]
and Alpinoschwagerina
[Bensh, 1972]
some of like fusulinids were assigned to these genera. The above-mentioned genera were
mainly described from the Asselian and Sakmarian, though their
first members were recorded in the upper Gzhelian Ultradaixina bosbytauensis Zone and
the last ones, in the Yakhtashian sediments. Fusulinids of this type were recently found in
the lower Gzhelian in the Darvaz and Donetsk basin and were recognized as a new
genus Darvasoschwagerina
[Leven and Davydov, 2001].
[83] The above-reported major morphologic characters of the discussed fusulinids
remained almost unchanged with time. Only juvenarium was progressively altered. In
Gzhelian forms, for instance,
( Darvasoschwagerina donbassica Leven et Davydov, 2001 and others),
it resembles that of the Kasimovian Montiparus in the wall structure and
massive chomata. Juvenarium of the late Gzhelian, Asselian, and, partly, Sakmarian
forms, namely, of "Alpinoschwagerina" paranitida Besh, 1972,
"Occidentoschwagerina kokpectensis" Bensh, 1972, "Paraschwagerina" pseudomira M.-Maclay, 1949, and others, is similar to that of the Gzhelian
Triticites and Rauserites. Beginning with the Sakmarian time, it gained
features of Pseudofusulina s. l. characterized by strongly and
regularly fluted septa, sometimes with pronounced axial fillings, as in
"Paraschwagerina" kanmerai
[Nogami, 1961], "P." akiyoshiensis
[Toriyama, 1958], and "P." zhen'anensis
[Xia et al., 1996].
According to the biogenetic law, at early stages of ontogeny the
organisms bear ancestor characters. If so, the marked differences in the juvenarium
structure of the discussed fusulinids mean that different ancestors repeatedly and
at different times produced morphologically similar forms that, despite their general
similarity, should be interpreted as separate taxa. At first sight the current taxonomy
fits this requirement, keeping in mind that these forms are referred to different genera,
namely, D arvasoschwagerina, Occidentoschwagerina, Alpinoschwagerina, and
Paraschwagerina. However, on distinguishing these genera (excluding the former) no
particular significance was attached to differences in the juvenarium structure. Moreover,
the validity of Occidentoschwagerina and Alpinoschwagerina can be questioned
following
Forke [2002],
based on their diffuse diagnosis and undoubted similarity of the
genotypes with the genus Pseudoschwagerina. As for Paraschwagerina, judging from
the juvenarium with strongly fluted septa and general habitus, it can be compared only with
relatively young, Sakmarian-Yakhtashian members of the discussed fusulinid group.
However, they are also most likely of independent origin considering the attribution of
typical Paraschwagerina to the other, significantly isolated from the Tethys,
Midcontinent-Andean biogeographic region.
[84] All the above suggests the necessary distinction of Paraschwagerina-like fusulinids
with a simple juvenarium structure, such as "Alpinischwagerina" paranitida Bensh,
"Occidentoschwagerina" kokpectensis Bensh, "Paraschwagerina" acuminata uralensis
Rauser-Chernousova, "P." inflata Chang, and a lot of others, in a separate genus. This
conclusion was previously made by V. I. Davydov who recognized the new genus
Likharevites. Unfortunately its diagnosis was published in the Deponent of VINITI and
was almost beyond the reach of most of researchers. Owing to this, though the author
repeatedly used the name Likharevites, it actually remained nomen nudum. With the aim
of securing this name we give below the diagnosis of the genus similar to that by the
author, however, with certain refinements produced by the latest available records.
Diagnosis.
[85] Shell small to moderately large, fusiform to nearly spherical,
with bluntly pointed poles. Mature individuals usually possess 5 to 6 whorls. First three
of them constitute very tightly coiled juvenarium, which is followed by abrupt expansion
into loosely coiled adult stage. Spirotheca composed of tectum and thin alveolar keriotheca.
Septa thin, rather strongly but irregularly fluted throughout the shell. Septal folds variable
in height; some involve only lower third of septa, whereas others extend to tops of
chamber. Regularity of septal flutings increases from ancient to more developed species.
In juvenarium septa wavy or gently fluted in the highly developed species. Axial filling is
absent. Tunnel low and feebly marked. Chomata weak but clear, present only in
juvenarium.
Discussion.
[86] The discussed genus differs from Paraschwagerina Dunbar
et Skinner (s.s.) in a more simple juvenarium, which indicates that it originated from
a relatively primitive ancestor. This is also confirmed by the older, late Gzhelian-Sakmarian
age of our genus. The typical American Paraschwagerina members are dated as the
Sakmarian-Artinskian
[Wardlaw and Davydov, 2000].
Likharevites generally differs from Alpinoschwagerina (Bensh) (s.s.)
in a fusiform shell, significantly stronger fluting of septa, and in smaller size.
The author of the genus referred to it fusulinids from the Triticites (?)
fornicatus Kanmera group, which was in our opinion untrue, since they correspond to the
above diagnosis neither in shell size nor in coiling and septal fluting and most likely
should be recognized as a separate genus.
[87] Type species - Pseudoschwagerina (?) sartauensis
[Davydov, 1986, p. 92-93, Plate 14, fig. 11].
Likharevites gracilis , n. sp.
Plate 6, figs 2-11a
[88] Paraschwagerina inflata Chang.
[Kahler, 1989, Plate 5, fig. 2, p. 224].
[89] Alpinoschwagerina confinii F. et G. Kahler. [Chen Genbao et al., 1992, Plate 28, figs. 5, 6].
[90] Paraschwagerina bianpingensis Zhang et Dong.
[Chen Genbao et al., 1992, Plate 28, fig. 9].
[91] Paraschwagerina aff. toriyamaia (Igo).
[Forke, 2002, Plate 38, fig. 11, p. 250].
Etymology.
[92] Gracilis - slender, slim (Lat.).
Holotype.
[93] GIN 4781/95. Axial section. Iran, Anarak section,
Zaladou Formation, Unit 8; Permian, Cisuralian, Asselian.
Material.
[94] 25 axial sections.
Description.
[95] Shell moderately large, fusiform to nearly spherical,
with bluntly pointed poles. Mature individuals usually possess 5 to 6 whorls. First
three of them constitute very tightly coiled juvenarium, which is followed by abrupt
expansion into loosely coiled adult stage. Spirotheca composed of tectum and thin
alveolar keriotheca. Septa thin, rather strongly but irregularly fluted throughout
the shell. Septal folds high and broad. In juvenarium septa wavy or gently fluted.
Axial filling is absent. Tunnel low and feebly marked. Chomata weak but clear,
present only in juvenarium.
Variability.
[96] The outer shape of shell and juvenarium are primarily
subject to variations. Juvenarium is particularly variable: from elongated fusiform
to short oval. The degree of septal fluting slightly varies as well. Variations are
sometimes so significant (for instance, between figs. 4 and 5, Plate 6) that
the affiliation of certain forms to the same species casts some doubt. However,
the concurrent occurrence of numerous intermediate forms permits the consideration
of these variations as a result of intraspecific variability.
Discussion.
[97]
The species is similar to Likharevites kokpectensis
(Bensh) but possess a shorter and more inflated shell. In this respect it can be compared
with Likharevites inflatus (Chang). However, this Chinese species has a more elongated
juvenarium, looser coiling, and slightly stronger and more regular septal fluting. The
tighter coiling and lesser septal folds differentiate the discussed species from the
Japanese Likharevites shimodakensis (Kanmera). Likharevites gracilis is very similar
to the species described by Rauser-Chernousova as Paraschwagerina acuminata var.
uralensis from the Asselian of the South Urals
[Rauser-Chernousova and Scherbovich, 1949].
However it differs from the Uralian form in a somewhat looser coiling and less
strong septal fluting.
Distribution and age.
[98] Iran, Carnian Alps, China; Permian, Ciauralian, Asselian.
Occurrence.
[99] Iran, Anarak, Zaladou Formation, Samples P4, P8, P12, C25, C38,
C39, RupA, Rup2, Rup4, R1, R2.
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