R O C Z N I K P O L S K I E G O T O W A R Z Y S T W A G E O L O G I C Z N E G O A N N A L E S D E L A S O C l E T E G E O L O G I Q U E D E P O L O G N E
T c m ( V o l u m e ) X X X I X — 1969 Z e s z y t ( F a s c i c u l e ) 1—3 K r a k ó w 1969
M.Y. SEROVA*
COMPARISON OF CHARACTERISTICS OF RZEHAKINIDAE IN THE CARPATHIAN REGION AND PACIFIC PROVINCE
М. Я. СЕРОВА
Сравнительная характеристика ржегакинид Карпатского региона и Тихоокеанской провинции
The Rzehakinidae form one of the most interesting, but poorly studied groups of the arenaceous Foraminifera. A t the present, not only the .origin of silica in the test w all (i.e. w hether it is agglutinated or secre- tionary, prim ary or resulting from diagenetic replacem ent of a prim arily calcareous test) is problem atical but there is also the question, as to w hether the type of coiling is of taxonom ic im portance for the group
;(S c o t t, 1961). Moreover, the problem concerning the position of Rzeha
kinidae in the scheme of phylogenetic developm ent of protozoans is being solved in different ways.
In a previous paper ( S e r o v a , 1966), the present author tried to analyze the taxonom ic im portance of certain morphological features of representatives of the Rzehakinidae fam ily.
The present paper deals with the Stratigraphie im portance and char
acteristics of Rzehakinidae assemblages in various basins o f Late Cre
taceous and Early Tertiary age. A ttention is also drawn to the taxonom ic im portance of the type of coiling.
The discussion of these problems w ill be lim ited to a description of o n ly two genera 'belonging to this fam ily, Rzehakina and Silicosigmoilina, w hich are most interesting, very widespread and of considerable Strat
igraphie importance. These genera are w ell developed m ainly in Upper Cretaceous and Lower Tertiary deposits.
S ix species of the genus Rzehakina are most often encountered in recent literature: Rzehakina epigona ( R z e h a k ) , R. inclusa (G r z y - b о w s k i), R. fissistom ata (G r z у b о w s k i), found in the Carpathian Flysch basin, and Rzehakina epigona lata C u s h m a n et J a r v i s , R. epigona minima C u s h m a n et R e n z, R. venezuelana H e d b e r g, distinguished on the A m erican continent. Most micropalaeorit'ologists distinguish Rzehakina epigona or its variety R. epigona lata (on the American continent and in the most regions o f the Pacific province).
M. A. G l a e s s n e r (1937) and E. H a n z l i k o v ä (1955) consider the variety „lata” and the species R. inclusa and R. fissistom ata as junior synonym s of R. epigona. S. G e r o c h (1960), in his study on Rzehakina from the Silesian series of the Polish Flysch Carpathians, unlike the two
* A d d ress: Dr M. Y . S ero v a , G eological In stitu te , A ca d em y o f S c ie n c e .U S S R , M oscov W -17, P y z h e v sk ii 7.
15 R o c z n i k G e o l o g i c z n y t o m X X X I X
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previous authors, considers the possibility of retaining the Rzehakina forms distinguished by G r z y b o w s k i (1901), as independent specific taxons. Characteristic features, which served as a basis for distinguishing the species, mentioned above, are given below.
R z e h a k (1895) gave a detailed description of Rzehakina epigona, genotype of the genus. In this description, there are no data on the range of variability of this species, nam ely about changes in length-w idth ratio of the test. This is supposed to result from distinction of the variety ,,lata”, which differs from the typical form in a having wider, alm ost rounded form and a more compressed periphery (based on data by C u s h m a n and J a r v i s (1928), who described this variety from the Lizard Springs form ation of Trinidad).
The data on principal dimensions (length, width, thickness) are absent in the first description of this variety. It should be mentioned that, w hile describing the new variety R. epigona lata, C u s h m a n says that ,,...this variety is more rounded and much larger than the forms found in the Velasco shale of M exico” ( C u s h m a n and J a r v i s , 1928, p. 93), which were distinguished by him in 1927 as Rzehakina epigona.
In his later monograph on the Upper Cretaceous Foram inifera of the Gulf Coast and adjacent areas, C u s h m a n (1946) included in the synonym y of Rzehakina epigona lata not only the forms of Rzehakina epigona from the Velasco shale m entioned above, but also forms from the same deposits of the Tampico region, described by W h i t e (1928).
C u s h m a n (1947) also assigned Rzehakina from the Santa Anita for
mation (Venezuela) to R. epigona lata.
The main reason for the distinction of the variety ,,lata” by C u s h- m a n was the relative w idth of the test. It would be interesting, there
fore, to know the parametres of Rzehakina from various deposits assigned by C u s h m a n to this variety. U nfortunately, alm ost all C u s h m a n’s papers contain no data on parameters, even in the de
scription, of holotypes. Consequently, we were obliged to measure the forms figured. The results of these investigations are presented in Table 1.
Thus, at that time, C u s h m a n considered relative w idth of the test as a decisive point for distinction of the „lata” variety, w hereas in his monograph of 1946, he included in it not only the forms w ith a test wider than that of R. epigona (holotype of variety ,,lata”), but also forms w ith a similar degree of elongation, as w ell as forms more elongated than the holotype of Rzehakina epigona. In other words, all the R zeha
kina found on the American continent, regardless of the degree of elongation of the test, w ere assigned by C u s h m a n to R. epigona var.
la ta, whereas R. epigona was discarded.
The data cited seem to indicate that the degree of elongation („growth ind ex” after E. H a n z l i k o v a , in H o m o l a , H a n z l i k o v a , 1955;
„growth index” after S c o t t , 1961) is an intraspecific feature and its change in various forms cannot serve as a -basis for distinction of even a taxon of variety rank. However, this topic w ill be considered later.
Only two of the other specific taxons of the genus Rzehakina, w ill be considered: R. inclusa and R. fissistomata. These two species are known to have been distinguished first by G r z y b o w s k i (1901). on the basis of test structure, and were assigned to Spiroloculina (fam ily M iliolidae). When describing them, that author paid attention to the
— '227 —
Table 1
Name 'v P a r a m e t e r s of t a x o n
A u t h o r ,
y e a r N.
L e ng t h MM
L
Width MM
B
T h i c k n e s s
MU T
Degree of e l o n g a t i o n
L : B
Degree of f l a t n
B : T
1 p 3 4 5 6
Rseh.aki.ca e p i g o n a / R z e h a k , 1 8 9 5 / ,
h o l o t y p e 0 , 6 _ 1 , 5 2 , 9
R z e h a k i n a e p i g o n a / R z e h a k / y a r . l a t a Cushman a nd J a r v i s , 1 928, h o l o t y p e
- - - 1 , 3 5 3, 7
R z e h a k i n a e p i g o n a / R z e h a k / v a r . l a t a Cushman and J a r v i s ,
1932
- - - 1 , 3 5 3 , 7
R z e h a k i n a e p i g o n a / R z e h a k / W h i te , 1928
0 , 7 0 , 4 5 - 1 , 8 -
R z e h a k i n a e p i g o n a / R z e h a k / Cushman, 1927
- - - 1 , 5 5 -
R z e h a k i n a e p i g o n a / R z e h a k / v a r . l a t a Cushman, 194-6, F i g . 1
- - - 1 , 4 3 2 , 9
R z e h a k i n a e p i g o n a / R z e h a k / v a r . l a t a Cuslunan, 1^46, F i g . 2
- - - 1 , 9 3
R z e h a k i n a e p i g o n a / R z e h a k / v a r . l a t a Cushr.an, 1 v 4 7
- - - 1 , 6 -
siliceous composition of the test of these „Spiroloculina”. Lnter, on the basis of the composition of the wall and Spiroloculina type of coiling of chambers, they were assigned to Rzehakina genus. S. G e r o c h (1960), w ho studied these two species in detail, using topotypical material,, considered them to be independent species, existing along w ith a typical species Rzehakina epigona. However, w hen describing Rzehakina from the Upper Cretaceous and Lower Palaeogene deposits of the Silesian series of the Western Carpathians, S. G e r o c h finds that all the three
15*
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species found here, Rzehakina epigona (R z e h a k), R. inclusa ( G r z y b o w s k i ) and R. fissistomata ( G r z y b o w s k i ) have „...sim ilar internal structure of the test differing in the external m orphology” (S. G e r o c h ,
1960, p. 132). According to the data given by S. G e r o c h , the main difference betw een the two latter species and the genotype of the genus Rzehakina is the lack of um bilici in the central part of lateral surfaces of tests of the R. inclusa species and the much more flattened test of R. fissistomata, as compared w ith the two previous species. „The arrangem ent of the chambers in the central coils is distinctly marked on the surface of broad umibilical depression of both sides of the test”
( G e r o c h , 1960, p. 133), w hereas chambers of R. epigona and R. inclusa are usually closed by lateral protuberances of the w all of later chambers or by non transparent m atter of a supplem entary skeleton.
D espite considerable sim ilarity in the morphology of the tests of all three forms, in G e r o c h’s opinion, it is possible for them to retain independent specific taxons, since the extrem e forms R. inclusa and R. fissistomata „...are of stratigraphical importance in the Flysch of Silesian unit. The occurrence of Rzehakina inclusa is confined to the Lower Istebna Beds (Senonian), and R. fissistomata m ainly occurs in the Ciężkowice B eds”, (S. G e r o c h , 1960, p. ,132). U nfortunately, G e r o c h did not give his opinion on the validity of R. epigona lata m entioned above.
M. A. G l a e s s n e r (1937) and E. H a n z l i k o v a ( H o m o l a , H a n z l i k o v a , 1955) studied very thoroughly the ranges of Rzehakina epigona ( R z e h a k ) species and did not acknowledge the independence o f the taxons Rzehakina epigona lata C u s h m a n and J a r v i s and R- inclusa ( G r z y b o w s k i ) but considered them to be junior synonym s of R. epigona. It should be emphasized, however, that E. H a n z l i k o v a , though accepting M. A. G l a e s s n e r ’s interpretation of R. epigona, considers this species most probably to include a group of species. In her opinion, the M aestrichtian-Palaeocene forms of Rzehakina of the Carpathian Flysch assigned to Rzehakina ex. gr. epigona (R z e h a k)
„differ from the specim en-form s from the typical Cretaceous groups by several, relatively marked features”. These are:
,,1) a broad, umbiliform, relatively shallow depression in the middle of the shell;
2) a visible w inding, caused by the very thin w alls of the initial whorls;
3) larger size; this character can be influenced by very different factors;
4) the moderately asym m etrical growth, and especially the asym m e
trical w inding of the last whorl ( H o m o l a , H a n z l i k o v a , 1955, p. 495).
The features of M aestrichtian-Palaeocene Rzehakina, mentioned by E. H a n z l i k o v a , correspond quite w ell to those of the species, char
acterized by G r z y b o w s k i (1901) and G e r o c h (1960) as Rzeha
kina fissistomata, the latter being typical for M aestrichtian-Palaeocene deposits.
When describing „specim en-form ” in the Rzehakina ex gr. epigona group. H a n z l i k o v a tried to apply a method of grow th indices (length-w idth ratio). In other words, she tried to present precisely and statistically the very feature, on w hich C u s h m a n and J a r v i s distinguished the variety R. epigona lata. On the basis of the data
— 2 2 0 —
obtained H a n z l i k o v a established that „The specim ens found in sedim ents of a Palaeocene age (Beskydy Mts.) have a grow th index (length to width) alm ost agreeing w ith that of the specim ens from the Palaeocene of the Caucasus, which am ounts to 1,5, where on ly the hundredths are different. The specim ens found in sedim ents of M aestrichtian age... have values around 1,3” ( H o m o l a , H a n z l i k o v a , 1955, p. 495). Consider
ing the grow th-index to be of great im portance, E. H a n z l i k o v a , how ever, believes that the data obtained are prelim inary, since the m aterial available is quantitatively insufficient. Furthermore, in her opinion, to establish the taxonom ic rank of this feature, it is necessary to determ ine the variation in grow th-index for the forms of various generation. According to H a n z l i k o v a , it is not possible to subdivide the Beskydian Rzehakinidae into species, until this work has been carried out. She provisionally assigns all these Rzehakinidae to one group R z e hakina ex. gr. epigona.
The method proposed by Hanzlikova, for statistical treatm ent of features of Rzehakinidae of various generations, was used by G. S c o t t (1961), w ho published a rather detailed and interesting study of Rzeha
kinidae of N ew Zealand. He presented the results of statistical treatm ent of a large number of Rzehakinidae from the Upper Cretaceous and Lower Palaeogene deposits of N ew Zealand. The main aim of his work was to establish a definite opinion concerning m orphological variability of local Rzehakinidae population and the study of possibilities of using this variability for stratigraphic interpretation. G. S c o t t approached this problem from the point of v iew of a biom etric analysis of outer morpho
logical features of Rzehakinidae; the size of proloculus, w hich can be easily measured in planispiral forms w ithout investigating their sections, change in growth rate (length-w idth ratio) and the type of coiling of chambers. On the basis of m any data on the main param eters and their statistical treatm ent, G. S c o t t distinguished four m ain Rzehakinidae groups, occurring in the Upper Cretaceous and Palaeocene deposits of N ew Zealand: the a, y, ft and 8 forms. The a and y forms represent m ega- -and microsphaerical generations, in which coiling of chambers takes place in one plane (spiroloculinic type of coiling) in all grow th stages.
The forms w ith size of proloculus exceeding 50 microns (50— 75 microns) w ere assigned by G. S c o 11 to the m egasphaerical generation («), w h ile the forms having the proloculus below 50 m icrons in size w ere assigned to the microsphaerical one (y).
The forms o f group |3 and 5 are m icro- and m egasphaerical genera
tions of forms, in which coiling of successive pairs of chambers takes place in different planes (sigm oilinic type of coiling of chambers). In S c o t t ’ s opinion, the grow th ratios „a” for all forms studied are w ithin
the intraspecific rank.
Having analyzed the distribution in tim e of the groups distinguished, G. S c o t t points out that groups a and y, differing only in param eters of proloculus, are widespread in the low er part of the Haumurian stage (Maestrichtian), w here Rzehakina are better developed and more num er
ous than in the Raukumara series, where they appear for the first tim e.
„Later Haumurian and Teurian sam ples reveal progressive attenuation in the shape of the microspheric generation together w ith rotation of planes of coiling of early chambers. The megalospheric generation throughout maintains stability in shape dim ensions”, ( S c o t t , 1961,
— 230 —
abstract). In other words, the P forms, with sigm oilinic-type coiling of chambers, appear in the upper part of the Haumurian stage.
Rzehakinidae of the 5 group (megaspheric species w ith a sigm oilinic type of arrangement of chambers) are found in these deposits much more rarely. A ll four groups are present in the deposits of Teurian age (Danian-Lower Palaeocene) and disappear in Dannevirke time (Palaeo- cene).
When describing genetic relations of the four Rzehakinidae groups distinguished, S c o t t is inclined to regard them rather as being cogene- tic, assigning them to a single group, the Rzehakina group. However, the author does not exclude the possibility that P and 5 forms, w ith a sigm oilinic arrangement of chambers, are micro- and m egagenerations of an independent genetic group, which differs from the group represent
ed by a and y forms. In S c o 11 ’ s opinion, the extrem ely rare occurrence of 5 forms in the East Basin of N ew Zealand, contrasted w ith the abun
dance of the P forms, is an argument against such an assumption.
S c o t t assigned all Rzehakinidae of N ew Zealand not only to one genus Rzehakina, but also to one species of this genus, Rzehakina epigona (R z e h a k), on the basis of the relative stability in growth index of the m ajority of forms studied. In this case, S c o t t em phasizes considerably greater variability in grow th rate for representatives of the y form as compared w ith the a form.
W hile evaluating the validity of the genus Silicosigmoilina C u s h m a n (1927), G. S c o t t indicates that the main difference in diagnoses o f the genera Rzehakina and Silicosigmoilina is as follow s: the former shows planispiral coiling of chambers, w hile the planes of coiling of the latter change progressively and only the last chambers are arranged in one plane. The difference in geom etry of early chambers, however, in S c o t t’s opinion is not a reliable criterion for a genetic classification of the Rzehakinidae. To confirm this point of view , S t o t t notes that in N ew Zealand the assem blages of planispiral Rzehakinidae and those displaying a tendency to change the coiling plane are found together in the M aestrichtian and Danian-Palaeocene deposits and cannot be separated.
Having analyzed the Californian Rzehakina fauna, described by M a l l o r y (1959), S m i t h (1957), I s r a e l s k y (1951) and other authors, S c o t t writes: „that in this country the microspheric (v-group) of Rzeha
kina does show rotation of planes of coiling in upper Haumurian and Teurian populations; this being so, it w ould be quite unrealistic to assign the (5 and 5 groups to Silicosigmoilina”. The validity of this genus should be established ,,by careful stu d y of the Californian faunas” ( S c o t t, 1961, p. 36).
These are the essential conclusions of G. S c o t t , concerning Rzeha
kinidae and based on a statistical study of this problem. Practically all the considerable specific variability of Rzehakinidae (especially among representatives of the genus Silicosigmoilina) was grouped by him into one species, Rzehakina epigona R z e h a k. In this respect, he w ent even further than previous authors, not only elim inating species distinguished in the genus Rzehakina, but even denying the validity of the genus Silicosigmoilina C u s h m a n et C h u r c h . Consequently S c o t t con
siders the change in type of coiling of chambers to b e the intraspecific variability, whereas in numerous Foraminifera groups, particularly M i-
— m —
liolidae, representing the same structural type as Rzehakinida, this feature is considered to be at least of generic rank.
The Rzehakinidae being w ell represented in Cretaceous and Lower T ertiary deposits of the N orth-W est part of the Pacific province (Sakha
lin, Kamchatka, Koryak highland) attracted the attention of the present w riter. But, in contrast w ith previous investigations the taxonom ic im portance of certain morphological features, which served as a basis for the classification of the Rzehakinidae, was approached in the present studies from a som ewhat different point of view . In addition to the m ethods used previously for studying Rzeha!kinidae (immersion in trans
parent liquids; estim ation of the degree of elongation — growth ratio, after G. S c o t t , 1961 1; the degree of flatness, by means of elem entary statistics), thin sections were examined, to study the inner structures of
Rzehakinidae.
The application of this method perm itted exam ination of the types of coiling of chambers, their forms, the character of supplem entary skeletal formations and the forms of sigm oid spiral in Silicosigmoilina.
The study of these features, which is possible only in transverse cross- -sections, made through the initial chamber of Rzehakinidae tests, per
m itted the establishm ent of new supplem entary features in the generic and specific diagnoses of Rzehakinidae. The results of these studies, concerning m ainly the representatives of the genus Silicosigmoilina, have been published in part ( S e r o v a , 1966). In the present account, the methods of exam ination, described in the paper, cited above w ill not be considered. The reader will find here only the point of view of the present writer on evaluation of the taxonom ic im portance of certain features of Rzehakinidae, questioned by G. S c o t t.
First of all, the author does not agree with S c o 11 as to his evaluation of the type of coiling of chambers of Rzehakinidae. This feature w as inherited by Rzehakinidae from the M iliolidae fam ily, w hich includes tw o genera: Spiroculina d ’ O r b i g n y , 1926, w ith a planispiral arrangement of chambers, and Sigmoilina S c h l u m b e r g e r , 1887, which differs from t'he gen u s Spiroloculina in the arrangement of chambers along a sigm oid spiral. The arrangement of the coiling plane for all other genera o f M iliolidae is known to be the main, diagnostic generic, feature. The common occurrence in one population of Rzehakinidae w ith sigm oilinic and convincing spiroculinic types of coiling cannot 'be held as a convinc
ing criterion for uniting them into one species, as was suggested by S c o t t .
M oreover, it seems that the data presented 'by S c o 11, rather confirm than deny the existence of two generic categories, Rzehakina and Sili
cosigmoilina in Upper Cretaceous and Lower Palaeogene deposits of N ew Zealand. The presence of both micro- and macrogenerations in forms w ith a sigm oilinic arrangement of chambers (P and 5 forms of Scott) is certainly an argument in favour of recognition of the genus Silico
sigmoilina. The 5 forms are more seldom found in the Eastern Basin o f N ew Zealand, as compared w ith the (3 forms. This can be explained by a specific, ecological environm ent, allowing large-scale developm ent of
1 Editor's note: T h ere is no close an alo gy b e tw e e n S e r o v a ’ s d eg ree of e lo n g a tio n and S c o t t’s „grow th ra tio”, sin ce 'the la tter is ex p r e sse d as th e ra tio o f stan dard d ev ia tio n s of len g th and w id th of a series of sam p les.
— 232 —
forms of the microspherical generation, as w ell as by the fact that the m aterials have not been studied thoroughly enough.
As to the grow th ratio (length/w idth ratio), G. S c o t t ’ s studies have d istin ctly shown, that this feature cannot be used for generic diagnosis, since wide and short forms can be found in Silicosigmoilina (in the holotype of species Silicosigmoilina californica, the length/ w idth ratio does not exceed 1,2), w hereas relatively narrow and long forms were found in Rzehakina (Rzehakina epigona from the Velasco shale of M exico, described by C u s h m a n in 1927, length/w idth ratio is 1,9).
Statistical treatm ent of the degree of flatness of tests (thicknees/width ratio) gives more prom ising results. The degree of flatness for the genus Rzehakina does not exeed 0,4 and is generally sm aller. The degree of flatness for representatives of the genus Silicosigmoilina is alw ays larger than 0,4, because the tests of Silicosigmoilina are alw ays sw ollen in the central part, owing to a sigmoid arrangement of chambers.
As follow s from these data, the genera Rzehakina and Silicosigmoi
lina are equally valid.
They are distinguished m ainly by means of different types of coiling of chambers: Rzehakina displays spiroloculinic type of coiling and Silicosigmoilina a sigm oilinic one.
The m aterial obtained by the present author, in a study of the Rzehakina fauna from the Upper Cretaceous and Lower Tertiary deposits of the N orth-W est part of the Pacific province, perm its the distinction of four species of Rzehakina, distributed w ithin this tim e interval. These are . Rzehakina epigona (R z e h a k), R. fissistomata ( G r z y b o w s k i ) , R. inclusa ( G r z y b o w s k i ) and the subspecies R. epigona mi ni ma C u s h m a n et R e n z , which latter m ust be regarded as an independent specific taxon. The supplem entary features obtained for each species distinguished from a study of their internal structure and the structure
of the w all in thin sections w ill be given below.
Before the exam ination of the internal structure, the specific identi
fication of Rzehakina found in the present m aterial w as determ ined on the basis of those external m orphological features, w hich w ere reported in the description of holotypes: supplem entary data cited in the work of Ge r o c h (1960) w ere considered for the first three species. A fter G e r o c h, forms displaying relatively elongated tests w ith a length/w idth ratio of not less than 1,5, as w ell as distinctly pronounced depressions (umbilici) in the central part of the lateral sides of the test, w ere assign
ed to the species R. epigona. Forms assigned to the species Rzehakina inclusa ( G r z y b o w s k i ) are characterized by approxim ately the same length/w idth ratio as for representatives of R. epigona, but they show som ewhat sm aller dimensions; and the sides of their tests are almost flat w ith a barely detectable concavity in the central part. Both in the first and in the second species chambers of the last w horl only are observed on the outer part of the test. Specim ens assigned to the species Rzehakina fissistomata ( G r z y b o w s k i ) differ from the first two species in the considerably greater w idth o f the test. The w idth of the test in some specim ens is alm ost equal to the length (length/w idth ratio of specimens of this species ranges from 1 to 1,2— 1,3, never reach
ing the value of il,5). Moreover, th ey differ in uncom plete involution of chambers. C onsequently the chambers of early w horls are alw ays seen in the shallow broad umbilicus of the test.
- - 2,33 —
Table 2 shows the main parameters and degree of elongation of the Rzehakina holotypes cited above.
Exam ination of Rzehakinidae in thin sections showed that the repre
sentatives of genus Rzehakina are characterized, ( S e r o v a , 1966) by saddle-shaped or lum p-shaped forms of outer contours of the chamber in cross-section, w hile lateral protuberances may reach alm ost the middle part of the test, closing partly or com pletely the chambers of previous whorls. The degree of involution of various Rzehakina species is differ
ent, providing supplem entary data for diagnosis of the species.
The representatives of R. inclusa ( G r z y b o w s k i ) display small, rounded-triangular, inner cavities of chambers in cross-section, equi- dim ensional in the direction of w idth and thickness of the test. The wall of the chamber is thin and lateral protuberances of the test wall reach the central part of the test, even slightly covering the w all of the opposite chamber. Because of com plete involution of each pair of chambers, the chambers of the previous whorls are not seen on lateral surfaces. Since the lateral surfaces of the opposite chambers are in close contact or even slig h tly overlapping, there are no depression in the central part of the
test of R. inclusa specim ens.
TaTale 2
M a ln parameters
° fs p e c i e s
Lenght MS
Degree o f e l o n g a t i o n le n g t h /w i d t h
Rzehakitia epigona /K zehak/ 0 , G 1 , 5
Rzehakina i n c l u s a /G rzybow sk i/ 0 , 9 1 , 6 Rzehakina f i s s i s t o m a t a
/G rzy b o w sk i/ 0 , 7 - 1 , 2 1 - 1 , 3
The inner cavities of chambers of R. epigona species are oval in cross- -section w ith long axis elongated in the direction of the thickness of the test.
The dim ensions of chambers increase rather rapidly as added, so that the cross-section of each chamber of the subsequent whorl is almost tw ice as large as that of the chambers of the previous one. The w all of chambers is rather thin, the chambers being almost com pletely involuted.
Lateral surfaces of the opposite chambers, how ever, do not adjoin each other at all, as in the case of R. inclusa species, forming a deep narrow um bilicus in the central part. This umbilicus in the specim ens from the Far East was, as a rule, filled w ith the fine-grained glassy m aterial
of a supplem entary skeleton.
Rzehakina fissistomata (G r z y b o w s k i) differs more distinctly from R. epigona in outer morphological features, because on lateral sur
faces of this species the chambers of early whorls could be seen. Such a test structure is due to the form of the chambers, w hich are half involuted, as can be clearly seen in cross section. The cross-section is sim ilar to that described for R. epigona: lateral protuberances of the wall
of chambers of R. fissistomata reach only the middle of the lateral sur
face, leaving the chambers of the previous whorls half open.
The differences m entioned above cannot result from a m odification of the variability, because all the specim ens studied had commensurable parameters of the proloculus, its size not exceeding 27— 30 microns.
According to the classification by S c o t t (1961), it is necessary to assign them to the form v (microspherical generation w ith a planispiral arrangement of chambers).
Thus, as a result of studying Rzehakina in cross-section (thin sections and polished surfaces) new data were obtained. They confirmed the view put forward by G e r o c h on the specific rank of the taxons R. epigona, R. inclusa and R. fissistomata.
On the basis of the opinions cited above concerning the taxonom ic rank of the degree of involution of chambers, the variety Rzehakina epigona minima C u s h m a n et R e n z should be given the rank of a species, because it is characterized (unlike the forms described above) by a com plete evolution of chambers, so that the chambers of all whorls are alw ays visible on the test surface.
R. minima C u s h m a n et R e n z species is rather similar to R. ve- nezuelana H e d b e r g in terms of m orphology of the test. They differ only in range of vertical distribution; R. minima is characteristic of Upper Cretaceous and Palaeocene deposits, whereas R. venezuelana w as described by H e d b e r g (1937) from Neogene deposits (Carapita for
mation) of Venezuela. Since Rzehakina were not found in the north- -w estern part of the Pacific province in deposits younger than Palaeocene in age, the present author cannot express her opinion on the validity of
the species R. venezuelana.
R. epigona lata C u s h m a n et J a r v i s , as considered by C u s h m a n (1946), is certainly composite and probably includes, three species of the genus distinguished on the European continent: R. epigona, R. in
clusa and R. fissistomata. The present author shares the opinion of G. S c o t t , who indicated the necessity of a detailed study of the Cali
fornian Rzehakinidae fauna.
A fter a short review of the m orphology of Rzehakinidae tests, geo
graphical distribution and evaluation of the im portance of this group for stratigraphic subdivision and correlation w ill be discussed. A vailable data on the distribution of this Foraminifera group in time and space are not numerous and som etim es incom plete. Since this problem w as considered in general terms by T h a l m a n n (1949), the data given in his paper w ill be not repeated here. Only new m aterial on the distribu
tion of this group in the Carpathians and Crimea-Caucasian region of the A tlantic province and in some areas of the Pacific province, where Rzehakinidae are best studied, w ill be discussed.
When analyzing the geographical and stratigraphical distribution of Rzehakinidae, it is necessary to emphasize that only the genus Rzehakina is present in the Upper Cretaceous and Palaeogene sedim ents of the Carpathian and Caucasian regions. There are no definite indications of the occurrence of Silicosigmoilina. Both genera are equally developed within this tim e interval in the Pacific province, w ith Silicosigmoilina prevailing in certain regions. It seem s, however, that such lim ited distri
bution of Silicosigmoilina within the Pacific province does not correspond to the real distribution and may be due to the poor know ledge of this group on the European continent. The possibility is not excluded that
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som e authors could have taken Silicosigmoilina tests for Rzehakina, because Rzehakina and Silicosigmoilina have a flat spiral and are very similar. This opinion was confirmed by the discovery of Silicosigmoilina tests in the Cretaceous flysch deposits of the Carpathians (the collection of N. I. M a s 1 a k o v a). The present discussion w ill be lim ited to the published data.
The Rzehakina fauna in the Polish Flysch Carpathians was described by S. G e r o c h (1960), from the Silesian unit. It occurs in Flysch sedi
m ents, characterized by the wide developm ent o f arenaceous Fora- m inifera. The first Rzehakina assigned provisionally by G e r o c h to Rzehakina epigona (?) R z e h a k w ere found by him in the upper part of the Godula Beds (horizon w ith Hormosina ovulum ( G r z y b o w s k i ) var. gigantea G e r o c h ) . In the lower Istebna Beds (Campanian-M aest- richtian), G e r o c h recognizes two species of Rzehakina, R. epigona ( R z e h a k ) from the Godula Beds, and R. inclusa ( G r z y b o w s k i ) , found only in the Istebna Beds. In G e r o c h ’ s opinion, the latter may be considered as being an index species for Cam panian-M aestrichiian deposits w ithin the Carpathian region.
In the Upper Istebna Beds and Ciężkowice Beds of the D anian-Pala- eocene age (horizon w ith Nodellum velascoense ( C u s h m a n ) , Rzehakina fissistomata ( G r z y b o w s k i)), Rzehakina epigona (R z e h a k.), Hormo
sina ovulum ( G r z y b o w s k i ) , a new Rzehakina species appears. This is R. fissistomata ( G r z y b o w s k i ) , the vertical distribution of which is D anian-Palaeocene in the Carpathian region.
According to the data presented by G e r o c h , Rzehakina does not pass into the upper (Eocene) part of the Silesian unit (H ieroglifie Beds, M enilite Shales, Krosno Beds).
A similar feature of the vertical distribution of Rzehakina in flysch deposits of the Silesian Carpathians is given by E. H a n z l i k o v a , who assigns all forms of Rzehakina to one group Rzehakina ex. gr. epigona
( R z e h a k ) .
Later on E. H a n z l i k o v a (1965, p. 36) recognized the follow ing Rzehakina species and gave their vertical distribution in the West Car
pathians Flysch: Rzehakina epigona lata C u s h m a n et J a r v i s and Rz. epigona ( R z e h a k ) — M aestrichtian-Danian; R. minima C u s h m a n et R e n z and R. complanata ( G r z y b o w s k i ) — Danian-M ontian;
R. inclusa ( G r z y b o w s k i ) — M ontian-Landenian.
A scheme of vertical distribution of Rzehakina in Flysch deposits of the Eastern Carpathians, sim ilar to that of S. G e r o c h , is presented by E. V. M i a 1 1 u k (1950), N. V. D a b a g i a n ( V i a l o v , D a b a g i a n , K u l c h i t s k i y , 1960); V i a l o w , D a b a g i a n , Z h u r a k o v s k i y (1967). The first Rzehakina described by D a b a g i a n as Rzehakina epi
gona ( R z e h a k ) and R. inclusa ( G r z y b o w s k i ) w ere collected by her from the deposits of fine- and m iddle-rythm ical flysch of the Stryj series, exposed in the key section of the Cretaceous flysch on the Dnestr river, betw een Tereshov and Spas. These deposits overlie sandstones of Iamna type and are assigned by D a b a g i a n to the uppermost Campanian.
In the rocks of the sandy-clayey greenish-grey flysch (D anian-Palaeo
cene) of the upper part of the Stryj series, Dabagian recognized the species Rzehakina fissistomata ( G r z y b o w s k i ) . E .V . M i a t l u k (1950) describes R. epigona from the middle (Maestrichtian) part of the Stryj series.
We have only poor data on the distribution of Rzehakina w ithin the
— 236 —
Crimea-Caucasian area. M. A. G l a e s s n e r (1937) described Rzehakina epigona from Flysch deposits of the Ilsk area. He assigned them to the Goriaczi klucz horizon (Palaeocene), whereas N. N. S u b b o t i n a re
cognized this species in the flysch deposits of the inferior horizon (Danian- Lower Palaeocene). R. epigona was also found by I. K a c h a r a v a and M. K a c h a r a v a in Palaeocene clays, overlying marls, containing Globorotalia conicotrunoata in the Adzhar-Trioletsk folded zone of Georgia.
Only two Rzehakina species are known from Trinidad: R. epigona lata C u s h m a n et J a r v i s , P. epigona minima C u s h m a n et R e n z . According to B e c k m a n n (1960), both these species occur in the Naparima H ill form ation (the upper part o f which belongs to Lower Campanian) and in all the zones of M aestrichtian, Danian and Palaeocene, including the Globorotalia velascoensis zone. But are not known in the Eocene and younger deposits. B o 11 i (according to the data by S c o 11, 1961) determ ines more exactly the low er lim it of the range of these two species and considers that R. epigona minima appears in the Globotrun- cana fornicata zone (Upper Santonian), w hile R. epigona lata occurs in the Globotruncana stuarti zone (Lower Campanian).
Thus, in the Upper Cretaceous and Palaeocene deposits of the Atlantic province only representatives of the genus Rzehakina were developed. There is no published data on the occurrence there of the genus Silicosigmoilina.
W ithin the Pacific province, the m orphology and stratigraphic distri
bution of Rzehakinidae seem to have been m ost thoroughly studied in Japan and N ew Zealand. They have been described in numerous papers by Japanese geologists, but were best studied b y T a k a y a n a g i (1960) and I o s h i d a (1963). Rzehakinidae forms w ith a sigm oilinic type of coiling of chambers appear first in the Upper Cretaceous deposits o f Hokkaido Island. T a k a y a n a g i found Silicosigmoilina in the deposits of the Lower Gyliakian stage (Cenomanian) and described them as Bram- letteia ezoensis T a k a y a n a g i . This species was traced by him along the section up to the deposits of the Lower Hetonian stage (lower part o f the M aestrichtian) inclusively. T a k a y a n a g i assigned Rzehakina w ith a spiroculinic-arrangem ent of chambers to Rzehakina epigona R z e h a k . They were observed only beginning from the deposits of the Upper Gyliakian stage (Turonian) and could be straced along the section up to the deposits of the Upper Urakai (Santonian). Thus on the basis of the data presented by T a k a y a n a g i , the vertical range of Bram- letteia ezoensis T a k a y a n a g i in Hokkaido is Cenom anian-M aestrich- tian, w hile that of Rzehakina epigona ( R z e h a k ) is Turonian-Santonian.
In the south-eastern part of Hokkaido, in the deposits of the Nemuro group, assigned b y Y o s h i d a (1963) to M aestrichtian, only the follow ing Silicosigmoilina species were found: Silicosigmoilina futabaensis A s a n o, S. futabaensis tokachiensis Y o s h i d a , S. kushiroensis Y o s h i d a , S. akkesievsis Y o s h i d a .
Rzehakina is not observed in the deposits of the Nemuro groups.
But in one of his earlier works, Y o s h i d a (1958) recognized the species Rzehakina epigona lata in the deposits of the Kavarappu formation, w hich he correlated w ith the Rzehakina-Spiroplectammina zone, this species being considered to be the most typical form for these deposits.
However, despite the presence of representatives of Rzehakina genus in the Japanese com plex of Upper Cretaceous and Palaeogene deposits
— 237 —
Silicosigvioilina still prevail m arkedly in the com plexes, both in quantity and their 'systematic variability.
The distribution of Rzehakinidae in N ew Zealand has been m entioned already. On the basis of recent data, given by G. S c o t t (1961) and N. de B. H o r n i b r o o k (1968), Rzehakinidae appear in this region in the low erm ost parts of the Raukumara series (Lower Senonian) and are traced upwards to the Lower Eocene, not passing into the Lower Eocene deposits. As was already m entioned, all the Rzehakinidae w ith a spiro- loculinic and sigm oilinic types of coiling w ere assigned by S c o 11 to one species, Rzehakina epigona (R z e h a k). H owever, on the basis of his data, it may be said that Rzehakinidae w ith a spiroloculinic arrangem ent of chambers (a and y forms, S c o t t , 1961) are traced w ithin the w hole tim e interval mentioned, from the Lower Senonian up to the Palaeocene.
The forms w ith a sigm oilinic type of coiling ((3 and 5 forms) appear only in the deposits of the Teurian stage (Danian-Lower Palaeocene) and are traced up to the upper boundary of the range of this group together w ith a and y forms.
T h a l m a n n (1949) gives the vertical range of Rzehakinidae on the Am erican continent, determ ining it w ithin the boundaries from Lower Senonian up to Palaeocene. The upper boundary of the range of Silico
sigmoilina oalifornica (after M a l l o r y , 1959) is lim ited b y the Narisian stage (Upper Eocene). Rzehakina from Lower Tertiary deposits of Cali
fornia are not determined b y M a l l o r y . However, as S c o t t states, certain Rzehakinidae cited in M a 11 o r y ’s paper as Silicosigmoilina californica should be assigned to genus R z e h a k i n a .
The distribution of R z e h a k i n a in the N orth-W est part of the P acific province w ill now be considered.
The first Silioosigmoilina here are very small, but w ith w ell pro
nounced morphological features. They were found in the Cogniacian-San- tonian deposits (Barykov suite) of the eastern part of the Koryak high
land, Ugolnaya Bay. O. D m i t r i e n k o (oral information) provisionally assigned them to the species Silicosigmoilina ex. gr. futabaensis A s a n o.
There is no data as yet on the developm ent of this group w ithin the deposits of the Campanian stage, but in the M aestrichtian and Danian- -Palaeocene deposits, both Silicosigmoilina and R z e h a k i n a are w ell developed. In some rocks, they represent the total assem blage of micro
fauna. In the deposits of the M ainy-Kakiyne range section assigned to the uppermost parts of M aestrichtian, (southern part of the Koryak high
land) the following species were found: Rzehakina epigona ( R z e h a k ) , Rz. inclusa G r z y b o w s k i , Silicosigmoilina californica C u s h m a n et C h u r c h , S. com pacta S e r o v a . In the D anian-Paleocene deposits, the Silicosigmoilina assem blage was more diversified. In addition to the above R z e h a k i n a species, Silicosigmoilina mindalaformis S e r o v a and S. futabaensis A s a n o were also found. In the upper part of Upper Palaeocene (zone Globigerina nana — Acarinina primitiva) and younger deposits of the region investigated, Rzehakina are lacking, w hereas Silicosigmoilina are found in Eocene deposits up to Upper Eocene.
A t Sakhalin, in the stratotypic section of Upper Cretaceous deposits on the Naiba river, Rzehakinidae were found in Campanian — M aestrich
tian deposits of the Krasnoiarsk formation and in Sinegory Beds of the D anian-Palaeocene age. In the low er part of the Krasnoiarsk formation, according to V a s i l e n k o ’ s data and the present w riter’s determ ina
tions ( S e r o v a , 1967), the follow ing are present: Rzehakina minima
— 238 —
C u s h m a n et R e n z , R. inclusa (G r z y b o w sk i), Silicosigmoilina futabaensis A s a n o, S. californica C u s h m a n and C h u r c h , S. per- plexa (I z r a e 1 s k y), S. ezoensis T a k a y a n a g i . In the upper Mae
strichtian part of the section of the Krasnoiarsk formation, the Sinegory Beds contain Rzehakina fissistomata ( G r z y b o w s k i ) R. epigona ( R z e h a k ) , Silicosigmoilina californica C u s h m a n et C h u r c h , S. kushiroensis J o s h i d a, S. elegantissima S e r o v a and Silicomassi- lina sinegorioa S e r o v a .
In the Eocene deposits of Sakhalin, as w ell as in the Koryak highland, on ly Silicosigmoilina w ere found.
On the basis of the above data on the m orphology and system atics of the Rzehakinidae and their geographical and vertical distribution, the follow ing conclusions may be drawn:
1) The main feature for distinction of genera in Rzehakinidae fam ily, as w ell as in isomorphic M iliolidae fam ily, is the type of coiling of chambers.
2) The degree of involution of chambers is one of specific feature?.
In combination w ith other features it permits the distinction of R. epi
gona, R. inclusa and R. fissistomata.
3) R epresentatives of the genus Rzehakina are best developed w ithin the Carpathian and Crimea-Caucasian regions of the A tlantic province, in the Upper Cretaceous and Lower Palaeogene deposits. Silicosigmoilina m ay also be present here. In the Upper Cretaceous and Palaeogene de
posits of the Pacific province, both of these genera are present.
4) Rzehakina species have a narrower time range of occurrence.
Involute forms o f th ise genera are developed in the M aestrichtian, Danian and Palaeocene. In the Pacific province, Silicosigmoilina appear in the Turonian stage (Japan: c.f. T a k a y a n a g i , 1960) and are traced in the section up to the Upper Eocene deposits.
5) Species of the genus Rzehakina are very valuable indicators of the age of rocks belonging to a certain facies type, ow ing to their narrow time ranges, the facies being, as a rule, characterized by an im poverish
ed assem blage of arenaceous Foraminifera.
A c k n o w l e d g e m e n t
I am v e r y g ra tefu l to P rof. B ied a, for h is k in d in v ita tio n to p a r tic ip a te in th e v olu m e ded icated to th e m em ory of P ro fesso r G r z y b o w s k i .
Geol ogical I n st i t u t e
A c a d e m y of Science, U S S R
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Р Е ЗЮ М Е
П риведенны е в работе данные по морф ологии и систематике рж егакинид и их географичеокому и вертикальному распространению позволяет сделать сле
дую щ ие выводы:
1. Тип навивания камер в сем. R z eh a k in id a e является основны м признаком для вы деления родов как и у изом орф н ого сем. M iliolid ae.
2. К числу видозы х относится признак степени объем лим ости камер который в сочетании с другими признаками, позволяет различать виды: R. e pigona, R. i n
clusa, R. f i s s is t om at a , R. m in i m a .
3. В пределах Карпатското' и Кры мско-Кавказского регионов в верхнем еловы х и 11 и ж не па л ео ге нов ых отлож ени ях п реи м ущ ествен н ое развитие имеют п р едста
вители рода Rz e ha k i na , хотя и не исклю чено присутствие зд есь силикоеигмоилин.
В тихоокеанской провинции в верхнем мелу и палеогене присутствую т о б а эти рода.
4. Р ж е гаки ны имеют бол ее узкий возрастной интервал по сравнению с си- лккосипмои линами. Инвалютные формы этого рода развиты в кампане, Маастрих
те, дании и палеоцене. Силикоеигмоилины в Тихоокеанской провинции появ
ляются в туроне (Япония, T a k a y a n a g i , I960) и прослеж иваю тся в р а зр е зе цо верхнеэоценовы х отлож ений включительно.
5. Виды рода R z e h a k i n a благодаря узк ом у временном у интервалу своего с у щ ествования является весьма ценными индикаторами возраста пород оп р ед ел ен ного фациального типа, как правило, охарактеризованны х обедненны м комплек
сом агглю тинирую щ их ф орам иниф ер.
В заклю чение я благодарю прсф . Б и еду за л ю безн ое приглаш ение принять участие в сборнике, посвящен-пом памяти Гржибовского.
