Diversification of spore-pollen “character states” in the Indian Permian

ELSEVIER

REVIEW OF PALAEOBOTANY AND PALYNOLOGY Review of Palaeobotany and Palynology 85 (1995) 319-340

Diversification of spore-pollen "character states" in the Indian Permian * B.S.

Venkatachala ", R.S. Tiwari b Vijaya b

a Wadia Institute of Himalayan Geology, 33, General Mahadeo Singh Road, Dehradun 248 001, India b Birbal Sahni Institute of Palaeobotany, 53, University Road, Lucknow 266 007, India Received 20 January 1994; revised and accepted 22 June 1994

Abstract The circumscription of palynomorphs depends on our understanding of "character states". In time, a character appears, distinguishes itself and proliferates. This paper attempts to delineate certain important characters found in palynomorphs of the Permian sequence of India, which commenced with a glaciogenic event followed by warm humid climate and terminated in relatively cooler and dry condition. The intervening time of c. 40 Ma witnessed a gradual amelioration of the climate which resulted in the proliferation of the Glossopteris flora. An analysis of some important characters of palynomorphs revealed major trends of diversification. The simple girdling monosaccate organization, as in Plicatipollenites, Parasaccites, and Virkkipollenites, was prevalent in the Early Asselian Lower Talchir Formation. Subsequently, during the Upper Talchir and Lower Karharbari Formations, varied architectures evolved in the mode of saccus attachment and its symmetry (such as in Crucisaccites, Divarisaccus, and Stellapollenites), although the basic plan of morphology remained monosaccate. Bisaccate pollen with simple striations (e.g. Crescentipollenites) also appeared in the Lower Talchir Formation. Certain characteristic features, such as vertical partitions and reticuloid arrangements of striations, appeared subsequently in the forms with basic bisaccate organization and are recognised in Rhizomaspora, Lahirites, and Verticipollenites. Taeniate morphology (as in Lueckisporites) first appeared at the top of the Karharbari Formation, followed by Lunatisporites in the Raniganj Formation and proliferated in the Lower Triassic Panchet Formation. The upper part of the Talchir and Lower Karharbari Formations became distinct by the advent of several spore morphologies, such as zona (in Indotriradites), cingulum (in Dentatispora), and the trilete apparatus expension imitating the saccus (sub-infraturma Varitrileti). All these characters are considered as dispersal aiding morphologies. Other trends of diversification through time (such as increasing variation of ornamentation and their differential distribution) appeared in Microbaculispora, Brevitriletes, Microfoveolatispora, and Didecitriletes. The analysis of palyno-assemblages based on evolutionary character states holds a high potential for precise biostratigraphy.

1. Introduction T h e t a x o n o m i c c i r c u m s c r i p t i o n o f fossil spores a n d p o l l e n is b a s e d o n their m o r p h o l o g i c a l c h a r a c ters. Hence, these t a x a are c o n s i d e r e d as artificially d e l i m i t e d units. V a r i o u s c h a r a c t e r s in a t a x o n repre*Paper presented at the 8th International Palynological Congress, Aix-en-Provence, France, September 1992. 0034-6667/95/$9.50 © 1995 Elsevier Science B.V. All rights reserved SSDI 0034-6667(94)00122-Z

sent different e v o l u t i o n a r y states o r levels o f evolution. I n totality, the set o f c h a r a c t e r s in a s p o r e o r p o l l e n species is the result o f e v o l u t i o n o r e n v i r o n m e n t a l stress, o r b o t h . T h e e v o l u t i o n r a t e in different c h a r a c t e r s c o u l d be different t h r o u g h time. This can be s h o w n b y c h a r a c t e r state analysis. T h e " c h a r a c t e r s t a t e " is defined as a state o f a c h a r a c t e r in a t a x o n , i.e. w h e t h e r a p a r t i c u l a r c h a r a c t e r is primitive, t r a n s i t i o n a l o r advance. F o r example,

320

B.S. Venkatachala et aL/Review of Palaeobotany and Palynology 85 (1995) 319-340

the presence of a trilete mark in a monosaccate pollen is a primitive character state, bi- or a bent monolete mark is a transitional character state while its absence is an advanced character state. At the same time, in monosaccate pollen a complete circular saccus is primitive, bilateral configuration of saccus is transitional while bisaccoid-monosaccate construction is an advanced state within this group. These derivations are based on stratigraphically controlled occurrences of these characters through time, from Asselian to Scythian on Indian Peninsula. The taxonomic systems for classifying the dispersed spores and pollen are artificial; therefore, they have shortcomings due to subjectivity in the approaches of different taxonomists. This ultimately is reflected in palynostratigraphy. On the other hand, a palynostratigraphic study based on character states could remove the background noise of subjectivity because discrete characters are the expressions of evolutionary trends in morphology. Their assessment can, therefore, be made more objectively. In time, a character appears, distinguishes itself, and then proliferates. Its beginning and subsequent stabilization are the results of the response to the environmental requirements and adjustments for survival. The thickening of the exine, for example, could be the demand of environment for the protection of the genetic material of the cell, and consequently the preservation of the whole organism. Thus, the adaptational morphology may also be used to identify the time levels at which the form has responded to the changing conditions. In India the Permian sequence commences with a glaciogenic event in the Early Asselian Lower Talchir Formation. The time span of 40 Ma through the Permian witnessed a gradual climatic amelioration (Fig. 1 ). The proliferation of the Glossopteris flora had occurred in the late Early Permian. This was followed by a warm and humid climate that prevailed in the Upper Permian. Cooler and drier conditions were again attained at the end of the Permian (Datta and Mitra, 1982; Tiwari and Tripathi, 1988; Vijaya and Tiwari, 1992). It ultimately led for adaptation of a major evolutionary shift at the Permo-Triassic boundary when the warm and dry climate changed the environment in the Early Triassic.

my Period

250

LOWER TRIASSIC

Age

Early Scyfhian End Perm.

Formation

Panther

Biohorizon

VIII VII

Raniganj UPPER PERMIAN Kutti

270

VI

L.Lower Permian Barakar

V

LOWER PERMIAN

IV

Karharbari L.Sakmarian

2901

E.Sakmarian Yatchir

Ill

_.Assetian

II I

Fig. 1. General stratigraphy and age relationship of the Permian and Lower Triassic sequence and biohorizon levels based on palynoevents(after Vijaya and Tiwari, 1992). In the Permian sequence of the Indian Peninsula, six basic clans of character states in spore-pollen morphology have been identified. Bearing in mind the ameliorating climate, increasing humidity, and cyclic seasonality, an attempt has been made to analyse the evolutionary trends, their manifestation in the form of changing character states, and their relationship to stratigraphic levels (Fig. 1 ). The present evaluation is based on the stratigraphically controlled data, collected from several extensive studies of morphology of palynomorphs (Bharadwaj, 1962; Tiwari, 1965; Venkatachala and Kar, 1968a; Lele and Makada, 1972; Lele, 1975, 1984; Tiwari and Singh, 1981; Tiwari and RamAwatar, 1988; Tiwari and Tripathi, 1992; Vijaya and Tiwari, 1992).

2. Clans and character states

The Early Asselian palyno-assemblages are the oldest available record for Indian Gondwana

B.S. Venkatachala et al./Review of Palaeobotany and Palynology 85 (1995) 319 340

Sequence (Lele and Chandra, 1972; Lele, 1984). The main morphological characters of spores and pollen of this time are assigned to six clans. The clans of character states are defined here to represent a group of palynomorphs which are organizationally closely related with each other in the basic mode of morphology. Each clan comprises several discrete characters. The girdling monosaccus mode is one of the important basic clans of character state. Through time, new character states of unique organizations in body-saccus attachment appear within this clan, namely, cruciform (Crueisaccites), para-attachment (Parasaecites), amphi-equatorial (Plicatipollenites), and star-shaped (Stellapollenites) (Fig. 3). Cumulatively, they form a set of character states within the clan of girdling monosaccate pollen. All forms cited here are girdling monosaccates but the character states of saccus attachment in each case is different. These organizationally close-knit characters of a clan have a lineage value because a uniform basic architecture underlies their construction. The protection and conservation of the genetic material, wider dispersal for effective propogation and an efficient mode of germination are essential a priori requirements for any morphological adaptation in spore-pollen. Thus, an analysis of distinct morphological features, which are related to the germinal apertures, body-saccus attachment modes, sexinal extensions and ornamentation, grooving patterns on the pollen body (corpus), and similar other inter alia manifestations, is considered important for a better understanding of morpho-evolutionary trends. The following six clans of character states are identified for discussion in this paper: (1) girdling monosaccus; (2) bisaccate construction; (3) SAFRA (SAccus-FRee Area); (4) germinal apparatus; (5) sculpture; and (6) sexinal extension (Fig. 2).

321

~F ~B

2.1 Girdling monosaccus

Fig. 2. The six basic clans of character states identified in spores and pollen. (A) Girdling monosaccus (Plicatipollenites). (B) Bisaccate construction (Vestigisporites); two figures illustrate typical nature of SAFRAwith distinctly structured sexine. (C,D) Advance state towards thinning and unstructured nature of exine in the region of SAFRAin monosaccates and bisaccates; in the latter (i.e. in D) a trend towards the sunken area (sulcus) is apparent (Satsangisaccites). (E) Germinal apparatus associated with laciniate folds, a distinctive character state in the Varitriletes group (Microbaculispora). (F) Sexinal extension in spores (Indotriradites), an imitation of a saccus character. (G) Lateral view of a spore of the Varitriletes group to illustrate the differential distribution of sculpture and body orientation (Microbaculispora). (H) A zonate spore in lateral view to project the orientation of sexinal extension.

The simple girdling monosaccate organization, as in Plicatipollenites (Fig. 3A), Parasaccites (Fig. 3B), Virkkipollenites, and Potonieisporites, is the character which originated in the Carboniferous (Vijaya and Tiwari, 1992). This group became distinct in the lowermost palyno-

zone of the Talchir Formation. Subsequently, it diversified during the Upper Talchir, resulting into new modes of saccus attachments (Plate I, 2, 4). Thus, the cruciform (Crucisaccites) and star-shaped (Stellapollenites) types of body-saccus organizations were probably produced to achieve a better

322

B.S. Venkatachala et al./Review of Palaeobotany and Palynology 85 (1995) 319 340

(

Fig. 3. A group of close-knit palynomorphs in the basic girdling monosaccus clan. (A,B) Girdling monosaccus (Plicatipollenites, Parasaceites). (C) Stellate mode (Stellapollenites). (D) Cruciform mode (Crucisaccites). (E,F) Bilateral bisaccoidal amphisaccate mode (Gondwanopollis, Divarisaccus). (G L) Expression of out-clan characters (i.e. striations and taeniae) in girdling monosaccate clan. (G) Reticuloid striations (Barakarites). (H) Simple horizontal striations on one face of the body (Striomonosaccites). (J) Subsequently striations developed on both the faces of the corpus (Distriomosaccites). ( K ) Further complexity is introduced by the development of sexinal inflated islands on distal face of the body (Goubinispora). (L) Appearance of sexinal bands on one of the faces of corpus (Kamthisaccites). (I) The basic girdling mode expresses a completely enveloping mode of saccus, as seen in Densipollenites. ( M ) Playfordiaspora further exhibits a trend of specialization in having continuous saccus on distal side and partial coverage o f the proximal side.

disperal mechanism (Fig. 3C,D). It is interesting to note that the development in this trend did not stop after achieving varied types of monosaccus configuration, as cited above. The ultimate thrust

of diversity was directed towards stablizing a bilateral bisaccoid mode of the saccus-spread. Such a change, from radial monosaccatism to bilateral bisaccoid condition, obviously served to conserve the building material. Examples of these trends could be sought in the taxa Divarisaccus (Fig. 3F) and Gondwanopollis (Fig. 3E). Most of these monosaccate diversities occurred during the deposition of the Upper Talchir and Karharbari Formations (Fig. 7). Thus, the Upper Talchir Formation can be identified by the first occurrence of these character states which make a First Appearance Datum (FAD). We consider the amelioration of climate from intensively cold to relatively warm as a causal factor for such a varied diversity. Besides various modes of saccus attachments discussed above, the clan of monosaccate character state also developed several other characters (e.g. rugulae, reticuloid striations, simple striations, taeniae) which probably originated in unrelated groups of pollen, such as in bisaccate, sub-saccate (or bisaccate with rudimentary sacci) and nonsaccate pollen, appearing at different times. In the basic clan of monosaccates, examples of these characters are many: sculpture of the body in the form ofrugulae (Rugasaccites), reticuloid striations (Barakarites; Fig. 3G; Parastriapollenites), simple striations (Striomonosaccites; Fig. 3H; Distriomonosaccites; Fig. 3J; Goubinispora; Fig. 3K), or taeniae (Kamthisaccites; Fig. 3L). The change in the basic organization through time, from girdling to enveloping monosaccus, is also recorded as an example of multiple diversity, e.g. in Densipollenites and Playfordiaspora (Fig. 3I,M; Plate I, 3-8). The appearance of these morphologies occurred late in the Permian when most of the other types of saccus configurations, discussed above, declined in monosaccate pollen. In bisaccate pollen, simple horizontal striations appeared first, followed by reticuloid striations (e.g. Crescentipollenites; Fig. 4H; Rhizomaspora; Fig. 4M; Plate II, 1, 3). In monosaccate pollen, however, the reticuloid striations appeared first (as in Barakarites; Fig. 3G) while simple horizontal striations appeared later (as in Striomonosaccites; Fig. 3H; Plate I, 3, 5). The appearance levels of new character states

B.S. Venkatachala et al./Review of Palaeobotany and Palynology 85 (1995) 319-340

323

cus with striations, however, continued to occur during the Upper Permian.

2.2 Bisaccate construction

Fig. 4. Diversity in bisaccate construction clan. (A) The simplest basic non-striate bisaccate mode (Vestigisporites). This path of the clan is relatively less diversified as illustrated in B-G, with the changes in the size of corpus, thickness of nexine and orientation of sacci through time (Platysaccus, B; Sahnites, C; Cuneatisporites, D; Scheuringipollenites, E; Klausipollenites, F; Satsangisaccites, G). Expression of Striations in bisaccates. (H) Simple horizonal grooves (Crescentipollenites). Much diversity is introduced to these linear striations in time. (I-Q) Circumstriatites, Striasulcites,

Faunipollenites, Tiwariasporis, Rhizomaspora, Schizopollis, Verticipollenites, Striatopodocarpites, Distriatites. Appearance of taeniae at intervals is also an important event as seen in

R T (Lueckisporites, Corisaccites, Lunatisporites).

within the clan of monosaccates can be linked with stratigraphy (Fig. 7). It has been established that in this group most of the morphologies which diversified during the Lower Permian declined or disappeared by the end of the Lower Permian. The enveloping monosaccus and the girdling monosac-

Two sacci attached on either sides of the central body form another clan of basic character state in saccate pollen. The earliest palynoassemblage of the Lower Talchir Formation is impoverished in bisaccate pollen. It has only Pityosporites as a representative of the simplest form. Striations appeared for the first time in the next younger palynozone (Biohorizon II; Vijaya and Tiwari, 1992). These linear grooves on the proximal surface of the body exine are generally considered to have developed in response to the increased seasonality in climate. They may have acted as hermomagathic apperati. In the Upper Talchir, the striations diversified to produce varied patterns, namely ends of the striations were joined to form a circumstriate configuration (Circumstriatites; Fig. 4I), vertical partitions appeared between the horizontal striations (Tiwariasporis; Fig. 4L), or striations were arranged to make a reticuloid pattern (Rhizomaspora; Fig. 4M). These characters proliferated to their maximum in the Karharbari and stablized during the remaining Permian, i.e. in the Barakar, Kulti and Raniganj Formations. Thus, varied types of striations in the bisaccate pollen began to dominate in the upper part of the Lower Permian and continued up to the Upper Permian (Fig. 7; Plate II, 1-5). The other significant character state is marked by the appearance of sexinal bands in the form of taeniae on the proximal face of the saccate pollen body. The terminal Karharbari Formation witnessed the initial appearance of this type of structure (Lueckisporites; Fig. 4R); it was followed by additional forms in the Barakar Formation (Corisaccites; Fig. 4S; Guttulapollenites). By the end of the Permian, multi-taeniate organizations manifested in Lunatisporites (Fig. 4T; Plate II, 8-10). The taeniate condition may not have arisen from a striate condition. The presence of this character in monosaccate (Kamthisaccites; Fig. 3L) as well as bisaccate (Lunatisporites; Fig. 4T) pollen suggests that the taeniae on the corpus originated

m~

m~

I

%

B.S. Venkatachala et al./Review of Palaeobotany and Palynology 85 (1995) 319-340 independently b o t h in m o n o s a c c a t e s and bisaccates (Figs. 3, 4). The other b r a n c h o f the bisaccate clan is represented by the non-striate, non-taeniate bisaccate pollen which are less diversified than the striate forms (Vesicaspora; Platysaccus; Fig. 4B; Seheuringipollenites; Fig. 4E). However, they are quantitatively p r o m i n e n t at several levels in the Permian, and some diversity has been observed in the b o d y - s a c c u s a t t a c h m e n t modes, e.g. in Klausipollenites (Fig. 4 F ) and Falcisporites, at the end o f the Permian (Plate II, 7). Several other characters are also expressed in the bisaccate group, namely rudimentary or sub-saccate condition where the saccus is spongy, condensed and not fully blown, as in Tiwariasporis (Fig. 4L), or m o n o s a c c o i d a l trend where m o n o s a c c a t e organization is simulated by the n a r r o w continuation o f sacci on lateral sides o f the b o d y (in several species o f Primuspollenites and Rhizomaspora). However, these expressions o f character states could n o t forcefully establish themselves in the bisaccate clan. Taking an overview o f the two clans discussed above, it is evident that the m o n o s a c c a t e pollen had, at different levels o f time, attempted to a d a p t saccus-spread to simulate a bisaccate condition and the vice versa is also true. Similarly, simple linear grooves, reticuloid patterns o f striations, or taeniae were introduced in b o t h the m o n o s a c c a t e and bisaccate clans at various levels, perhaps indicating a response to environmental conditions.

325

Does this m e a n that m o n o - and bisaccate pollen are artificial groups? In the b r o a d e r sense, this m a y be true; but considering the two types o f distinct saccus configurations in two populations o f forms, these two organizations fall into different clans.

2.3 SAFe,A S ~ is an a c r o n y m o f SAccus-FRee Area on the distal face o f the central b o d y in saccate pollen. The earliest Permian m o n o s a c c a t e pollen possessed a prominent tri-, bi- or monolete m a r k on the proximal face o f the b o d y (Plicatipollenites, Parasaecites, Potonieisporites); at the same time, the SAFl~ o f varied configurations were also delineated but the exine on the SAFaA at the distal region was clearly structured. This character state represents a "pre-pollen" state. The s ~ is not a sulcus but thinning o f its exine makes it a precursor o f a sulcus. In due course o f time, in such pollen the prominence o f proximal germinal m a r k gradually diminished, and so also the exine in the SAF~ became unstructured and thin, m a k i n g it a "sulcus". These two events established the change o f polarity. Thus, by the U p p e r Talchir, such trends o f stabilization in these character states became noticeable, as the SAF~ possessed the character o f a sulcus and the germinal m a r k on proximal side disappeared, as in Stellapollenites and Tuberisaeeites (Figs. 2, 3; Plate I, 1 4). In the saccate pollen, b o t h in m o n o - and

PLATEI Diversities in the monosaccate pollen character clans, i.e. girdling monosaccus, s ~ and germinal apparatus. All magnifications × 750 unless otherwise stated. 1. Plicatipollenites. Girdling monosaccus. Exine in SAFRAstructured and indistinct trilete mark. x 400. 2. Stellapollenites. Stellate mode of body-saccus attachment; unstructured exine in s~v,h and the absence of trilete mark. 3. Barakarites. Expression of reticuloid striations as out-clan character on body surface in girdling monosaccus clan; thin exined unstructured circumsulcus, and the vestigial trilete mark. x 400. 4. Divarisaccus. Bilateral amphisaceate mode of bod~saccus attachment, and the transformational phase of unstructured exine in s~ah in an alete pollen. 5. Distriomonosaccites. Expression of discrete character, i.e. horizonal striations on both the faces of corpus in an alete pollen. 6. Kamthisaccites. Expression of taeniae on proximal face of corpus, the out-clan character in girdling monosaccus; unstructured exine in S~V,Ain an alete form. 7. Densipollenites. Completely enveloping mode of saccus on corpus in an alete form. 8. Playfordiaspora. Partial enveloping of saccus on proximal face of corpus and complete covering distally; vestigial trilete mark on proximal face.

326

B.S. Venkatachala et al./Review of Palaeobotany and Palynology 85 (1995) 319 340

P L A T E II

I

B.S. Venkatachala et al./Review o f Palaeobotany and Palynology 85 (1995) 319-340

bisaccates, the SAFRAis distinguishable in the form of circular, oval, ovoid, biconvex, straight-sided, wide or narrow slit-like area. The shape of the SAH~ depends on the extent of saccus encroachment on to the body. In one of the deviation of the major trends, the outline of SAF~tA became diffused, as in Faunipollenites (Fig. 4K) and Scheuringipollenites (Fig. 4E; Plate II, 6). The trends o f evolution in SAFRAcharacter state are aimed to attain a true sulcus-state, to conserve maximum material, and to give protection to the vital region of germinal aperture on distal side. The sexine in SAFR_~is almost always thinner than the cappa. If the sexine is not differentiated and a considerable thinning accompanied by a dipression-like sunken area is developed in the region of SAH~ it becomes a true sulcus. The Early Talchir monosaccate pollen do not exhibit the true sulcate nature of the SAHtA because they show infrastructure in the exine. However, in the Upper Talchir, characters denoting considerable thinning as well as absence of structure in SAFRA start appearing, as in Parasaccites korbaensis and Plicatipollenites indicus. This is the tie-point for stratigraphy. By the beginning of the Barakar Formation, the state of the unstructured thin-exined SAFRA,morphologically similar to a sulcus, gets established, and continues in several forms of pollen during the Upper Permian (Scheuringipollenites). However,

327

the sunken depression-like feature hardly develops in the SAH~Auntil the end of the Permian by which time forms, e.g. Satsangisaccites and species of Cuneatisporites, Klausipollenites and Lunatisporites, started exhibiting true sulci (Fig. 4F,G,T; Plate II, 7, 9, 10).

2.4 Germinal appparatus The germinal aperture on the cappa of a saccate pollen or the proximal polar region of a spore is a significant character.

Pollen In

the

girdling

monosaccate

pollen,

i.e.

Plieatipollenites, Parasaccites, Virkkipollenites, and Potonieisporites, occurring in the Early Asselian, the tri-, bi-, or monolete mark continued to remain prominent in spite of the distinct delimitation of the distal SAH~. As stated earlier, in this clan the proximal aperture was well organized and in all probability also functional too (Vijaya and Tiwari, 1992). However, in the younger sequences they lost their functional value and became vestigial. This change-over is noted in several forms in the Upper Talchir Formation (e.g. Gondwanopollis, Parasaccites spp., Crucisaccites). It is significant to note that a defined or vestigial proximal mark is also present on the proximal face of the corpus

P L A T E II Diversities in bisaccate pollen character clans, i.e. bisaccate construction and nature of SAra~,A. All magnifications × 750 unless otherwise stated. 1. Crescentipollenites. In the basic bisaccate construction clans expression of horizontal striations as out-clan character. Exine in SAH~ indistinctly structured. 2. Circumstriatites. Circumstriate state, a discrete character in the out-clan character of linear grooves. Exine in SAFRA unstructured. 3. Rhizomaspora. Expression of reticuloid nature of striations as out-clan character in bisaccate construction. 4. Guttulapollenites. A globular form in bisaccate construction clan with clefs on corpus. N o distinctly unstructured exine established in SAFm~. 5. Distriatites. The out-clan character, linear grooves express further diversity occurring on both the faces of corpus. Unstructured exine in s ~ u ~ . 6. Scheuringipollenites. Simplest bisaccate form with indistinct SAF~. 7. Klausipollenites. Organisational variations in the mode o f body-saccus attachment of simple bisaccate pollen. SAFRAdistinctly developed as sunken area having unstructured exine, i.e. true sulcus. 8. Corisaccites. Expression o f two distinct sexinal bands on corpus as out-clan character. Indistinctly structured exine in SAra~. 9, 10. Lunatisporites. 9. Transitional state of taeniate out-clan character towards multi-taeniate. Unstructured exine in SAFPa~. 10. Established multi-taeniate state.

:~i~i~!!ii~i~ ~

~

~.,

~nUl. -.I--4 - - ~

L~

L~

B.S. Venkatachala et al./Review of Palaeobotany and Palynology 85 (1995) 319-340

329

in Vestigisporites (Fig. 4A), Sahnites (Fig. 4C), Tiwariasporis (Fig. 4L), Lueckisporites and Lunatisporites (Figs. 3, 4; Plate II, 8 - 1 0 ) . y-

1:"

Spores The simple trilete or a m o n o l e t e m a r k in spores (Plate III, 5, 7) c o n t i n u e d to r e m a i n a distinctive character all t h r o u g h the P e r m i a n . S u b - i n f r a t u r m a Varitriletes (comprising Brevitriletes, Microbaculi-

spora, Microfoveolatispora, Didecitriletes, Lacinitriletes, a n d Imparitriletes) represents diversity in the character of the trilete mark. The elevations along the labra, represented by regular laciniate folds in the proximo-distally compressed specimens, are indicators o f distinctive m o r p h o l o g i c a l organizations. Their f u n c t i o n could have been a n aid in dispersal, almost a n a l o g o u s with the saccus in a pollen (Fig. 5; Plate I l l , 1-4). The character state typified by laciniate fold is also manifested in different groups of spores, i.e. in sculptured as well as laevigate forms. The diversification o f this character state started in the U p p e r Talchir a n d was established in the Barakar, to c o n t i n u e t h r o u g h the rest of the P e r m i a n . The clan o f Varitriletes with character states o f trilete m a r k a n d o r n a m e n t a t i o n provides a useful c o n t r o l in stratigraphy.

Fig. 5. Diversity in three major clans, i.e. germinal apparatus, sculpture and the exinal extensions in spores. The mutual expression of these character states is seen in different spore groups. (A,D) An apiculate trilete spore with low and high ornamentation (Verrucosisporites, Horriditriletes). (B) Monosaccus with prominent trilete mark an expression of

germinal aperture and sexinal extension (Virkkipollenites). (C,E) Sexinal extension resulting into the formation of cingulum and zona, an imitating character state of a girdling saccus (Dentatispora, Indotriradites) in association with elevated germinal mark and the sculpture. (F-H) Subsequent variations observed in the nature of zona and cingulum (F, Gondisporites;

G, Densoisporites; H, Tethysispora).

PLATE III Diversities in spore character clans, i.e. nature of germinal apparatus, sculpture and exinal extension. All magnification x 750 unless otherwise stated. 1. Lacinitriletes. Distinct laciniate folds along trilete rays; psilate exine. 2. Microbaculispora. Highly elevated nature of folds in germinal mark; exine with low ornament comprised of baculate sculpture. 3. Microfoveolatispora. Distinct laciniate folds along trilete rays; exine sculptured with low foveolae. × 500. 4. Didecitriletes. Laciniate folds along trilete rays; exine beset with differentially distributed spines which are bigger in size. 5. Callumispora. Simple trilete mark and psilate exine. 6. Verrucosisporites. Simple trilete mark. Exine sculpture verrucose, bigger in size. 7. Indotriradites. Trilete mark elevated; exine sculptured with low to mediumly high spines. Exine extented as zona. 8. Lundbladi6pora. Trilete mark elevated and labra associated with thin folds. Exine sculpture of mixed kind, i.e. coni, bacula. Exine extended to create equatorial cingulum.

B.S. Venkatachalaet al./Review of Palaeobotanyand Palynology85 (1995) 319 340

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2.5 Sculpture The exine sculpture has developed independently in varied groups o f spores and pollen. T h e y are considered to have a role in dispersal and protection. The Callumispora-Leiotriletes type o f spores are examples o f simple psilate spores while Cyclogranisporites and Verrucosisporites are examples o f o r n a m e n t e d forms, occurring in the earliest Permian on the Indian Peninsula.

There is a noticeable trend in the patterns o f the gradual increase in o r n a m e n t size. This tendency is independent o f facies variation and t a x o n o m i c limits. The species distribution o f Microbaculispora, Verrucosisporites, and Micrfoveolatispora reveals that the older species (in the Talchir Formation) possessed smaller ornament, while the younger (in the B a r a k a r and u p w a r d ) are bedecked with bigger sculpture. The ameliorating climate appears to be one o f the factors for such a trend

B.S. Venkatachala et al./Review of Palaeobotany and Palynology 85 (1995) 319-340

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of full expression of characters. The first appearance of typical species with pronounced sculpture (e.g. Microfoveolatispora bokaroensis, Microbaeulispora villosa, and Verrucosisporites triassicus) marked the beginning of diversity in the lineages of sculptural characters (Plate III, 1-8). Another prominently visible type of character state is the differential distribution of ornament on the spore body. The character of restricted ornament on the distal and equatorial regions is observed in the earliest Permian (Imparitriletes). In time, several types of sculpture patterns manifested, such as baculae in Microbaculispora, foveolae in Microfoveolatispora, and coni-spines in Brevitriletes, Didecitriletes. Additionally, in these forms differential distribution of ornamentation and laciniate folds in trilete mark occurred in combination. The distally restricted ornamentation helped the entire spore to behave like a parachute. The sculpture could have added weight to the spore on the distal side which in turn helped landing in a suitable position (Fig. 5; Plate III, 2-4).

2.6 Sexinal extensions The saccus, zona, cingulum or other extension of sexine are adaptation for dispersal. They are essential aids for bouyancy, balance and protection. The sacci in the Permian pollen are "protosaccate". They are filled with alveoli (Scheuring, 1974, 1978; Tiwari, 1981) and do not possess an inner chamber as the true sacci (eusaccate) of modern Pinus do. The trend in evolution of the saccus shows a reduction in size, a trend from monosaccate to bisaccate construction, coarser to finer reticulation and protosaccate to eusaccate condition. The pollen found in the Talchir and Karharbari Formations had a leathery appearance with massive muri. In later stages, these structures became thinner and finer. Tiwari and Tripathi (1988) have related these characters to climatic amelioration. The linkage of morphology of the saccus with extremes in climate is also depicted in Densipollenites where the leathery nature (Plate I, 7) appeared in response to drier conditions. The Early Permian pollen had big sacci, and in

335

order to give support to these massive structures, a radial arrangement of muri (in Plicatipollenites) or double infrareticulation (in Primuspollenites and Rhizomaspora) was developed (Plate I, 1; Plate II, 3). The diploxylonoid condition is the dominating construction in bisaccate pollen of Permian but a haploxylonoid mode also developed prominently in the Talchir and Upper Raniganj Formations. This is also linked with the cooler climatic conditions (Tiwari and Tripathi, 1988). The cingulum and zona (or flange) in spores are the imitations of a saccus character. They are also sexinal extensions and help in dispersal by keeping proximo-distal orientation and balance of the body, and through equatorial rigidity the protection from mechanical damage is also provided. There are relatively few forms under this category, e.g. Jayantisporites, Dentatispora, Indotriradites,

Potonieitriradites, Gondisporites, Densoisporites, and Lundbladispora (Plate III, 7, 8). The genus Jayantisporites, a pseudozonate spore appearing in the lower part of the Talchir Formation, possessed discrete ornament, which partially coalesced at places along the equatorial zone and appears as broken patches of cingulum. This may be considered as an attempt for the sculptural element to align themselves at the equator simulating a zona. This character state appears to form a functional mechanism to aid in dispersal. They are not true zonate spores. The true cingulum appeared in the Upper Talchir Formation and a true zona in the upper part of the Karharbari Formation (Fig. 7). The cingulate spores declined by the end of the Lower Permian whilst a character with a reduced zona in the form of ridge appeared thereafter (Gondisporites). The end of the Permian witnessed the incoming of a new spore morphology with a smaller size and a compact and narrower cingulum, as in Lundbladispora and Densoisporites. The zona and cingulum appeared in the sculptured group (Indotriradites, Dentatispora) as well as in the non-sculptured group (Potonieitriradites, Densoisporites); thus, the sexinal extensions are manifested independently in several spore groups. The clan of cigulate-zonate organization possesses several character states in the nature of ornament, zona, cingulum and trilete mark. Their evaluation can be linked with stratigraphy.

336

B.S. Venkataehala et al./Review of Palaeobotany and Palynology 85 (1995) 319 340

3. Clans, character states and stratigraphy The evolutionary trends in the six clans, or the basic groups, appear to express various combinations of character states, at different levels of stratigraphy. Thus, basic organization being the same, several discrete characters overlap the different clans. The assembly of such characters at a particular time-level becomes diagnostic for a datum line. Fig. 6 explains this pattern where the sharing of striations and tetrad mark in monosaccare and bisaccate pollen groups are depicted. Non-striate and tetrad mark-bearing monosaccates represent two primitive character states whilst striate and alete monosaccates exhibit two advance character states, the clan being the same, i.e. girdling monosaccate clan. The stratigraphic significance of such evaluation is clear from Fig. 6. The advanced character state of having striations in monosaccate clan appeared for the first time at the end of Karharbari Formation (Lower Permian). Alete monosaccates made their first appearance at Biohorizon II of the Lower Talchir Formation. Taking the example of bisaccate pollen, the tetrad scar-bearing bisaccates were very few but occurred side-by-side of the alete bisaccates. It has been observed that in Talchir and Karharbari Formations the tetrad mark was more pronounced than in younger formations. In the Lower Triassic it almost disappeared. The striate and non-striate bisaccate dominance was balancing throughout the Permian but at the end of the Permian the non-striate bisaccates seem to have prevailed over the striate group. The analysis plotted in Fig. 6 shows that Biohorizon II of the Lower Talchir Formation is the level where almost all character combinations have started evolving. At the Karharbari-Barakar transition there has been a major shift in the dominance of clans and at the Raniganj Panchet transition the striations in bisaccate pollen started declining. The significance of appeareance and proliferations in various characters through the Permian and Lower Triassic and their bearing with stratigraphy are exemplified in Fig. 8. The girdling monosaccates with all manifestations of saccus organizations (cruciform, star-shaped, amphilat-

eral, etc.) and body characters (striate, non-striate, varied sculpture/structure, etc.) show up with a maximum number of species at the Talchir/ Karharbari transition. This is the time level when glaciers were almost completely withdrawn from the Indian peninsula and climate ameliorated to support rich vegetation which gave rise to coals in the Karharbari Formation. In the monosaccate clan the enveloping monosaccus appeared for the first time at the Karharbar~Barakar transition. It is an unmistakable index organization. In the bisaccate clan, the appeareance of reticuloid striations is the marker of Upper Talchir, and that of taeniae (bi-taeniate condition) denotes the Upper Karharbari Formation. Actually, the nature of the taeniae themselves shows primitive and advanced character states; the multiple taeniae appeared at the end of the Permian to become dominant in the Lower Triassic. Beside this, the subsaccate bisaccates or bisaccates with subdued, vestigial sacci proliferated in the Lower Barakar Formation. As a group, the characters of spores do not make significant markers, but taking the individual characters, the First Appeareance Datum (FAD) can be ascertained. For example, at the end of the Permian, the narrow, compact and well organized cingulum appeared and subsequently gave rise to varied forms (Densoisporites, Lundbladispora) which dominated in the Lower Triassic. It is to be noted that diversity in spores had considerably declined in the Kulti Formation, due to the drier conditions. When the distribution of various character states (along with their diversification) is plotted against the axis of time, a pattern emerges which demarcates several levels of stratigraphy. Fig. 7 exhibits such an attempt where morphologically distinguishable pollen and spores are grouped according to important gross characters. These groups (second column) broadly represent four clans: (1) girdling monosaccus; (2) bisaccate construction; (3) sculpture; and (4) sexinal extension. The SAFRA and the germinal apparatus clans of character states have not been included in this figure because exhaustive data about these characters are not available at present. The generic names indicate precisely delimited and well established organizations in the respective clans and the range lines of

B.S. Venkatachala et al./Review of Palaeobotany and Palynology 85 (1995) 319-340

distribution represent distinct and discrete units of circumscription generally described as "species". However, a line may represent one or more "species" in this figure, but definitely it represents one derivative of the main character state. A detailed description of each and every character is not possible here because of space restrictions as well as the scope of this article. Therefore, only the girdling monosaccus clan is taken up as an example (Fig. 7). It is clear from the distribution of various character states and their derivatives (solid lines) that the Lower-Upper Permian boundary can be identified as most of the proliferation lines die out at this level. So also the PermoTriassic passage zone is marked by a shift in the main characters of the saccate clan of the Permian. Similar trends (discussed in detail above) are also seen in this figure for the bisaccate pollen and the spores of different morphologies. The FAD of a character and its diversification and ultimately decline is evident by the solid lines of character state representations.

4. Discussion and conclusion

On the Indian peninsula, glaciers were prevailing at the advent of the Permian. The diversity of plant life was at its lowest due to the extremely cold climate. Lithological features, namely varves, dimictite, and rafted boulders in sandstones, suggest that cold climate continued throughout the entire Talchir Formation. But the progressive diversity in the morphology of palynomorphs reveals that much of the land was exposed in the Upper Talchir as a result of the melting of the ice and retreat of the glaciers. The characters which subsequently became dominant throughout the Lower Permian had established by the Upper Talchir (Fig. 7). The levels of appearance and diversification of selected characters are shown in Fig. 8. Their First Appearance Datum (FADs) and Last Appearance Datum (LADs) have proven to be useful in stratigraphy (Vijaya and Tiwari, 1992). Further analysis reveals that one group of character state overlaps the other basic group of character states (Fig. 6). Thus, monosaccate clan, during the course of

337

evolution, had a trend for the expression of striations, taeniae, bisaccoid construction, thinning of SAFe, gradual disappeareance of proximal trilete or monolete mark and fineness in saccus reticulation. Similarly, bisaccate pollen (both striate and non-striate) tend to exhibit monosaccate organization or rudimentary saccate construction, expression of vestigial proximal mark, narrowing and thinning of SAFI~ and fineness of saccus structure. The climate played a decisive role in the change and establishment of characters states. The frigid climate of the Talchir produced more haploxylonoid construction and more massive leathery and big sacci, big body, and a functional proximal germinal aperture. This was necessary to withstand the severity of the climate. Certain adaptations are also seen in the Kulti Formation as well as at the end of the Permian and the beginning of the Triassic, where adverse climate again intervened the otherwise amiable conditions of the Permian. Striations (linear groves) and taeniae (stripes of sexine) were developed both in monosaccates and bisaccates. Were they responsive to the climate? It is difficult to say at this juncture but they have been interpreted to play various roles (Tiwari, 1982; Vijaya, 1990) including those of emergency germinal apertures. In any case, these two important characters have persisted for a very long period of time in all types of climatic zones and hence they cannot be merely the result of adaptations to meet the climatic adversities. They represent evolutionary states of characters in pollen which helped in the survival of the Permian floras. The present study adds to the stratigraphic significance of cladistics by the way of analysing the manifestation of various character states in different clans (Figs. 7, 8). Recently, Cornet (1992) has suggested a practical method of palynofacies analysis. According to him, through the comparisons of ratios of different groups of pollen, a reliable correlation can be achieved. Thus the ratio of smooth:ornamented spores, cingulate:noncingulate spores; pollen with big sacci:small sacci etc., could provide correlation values. With reference to the present analysis, these ratios also represent the character state ratios. However Cornet's units are gross and, at times, could be unrelated with evolution and may reflect effects of

B.S. Venkatachala et aL/Review o[Palaeobotany and Pa(vnology 85 (1995) 319 340

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the first level o f m a x i m u m innovation in the Lower Talchir Formation, the major change datum at the Karharbari/Barakar Formations, the sprouting o f new character states at the L o w e r / U p p e r Permian Boundary, the decline in character diversification in the Kulti Formation, and an evolutionary shift at the Permo-Triassic boundary have been identified by character state analysis.

B.S. Venkatachala et al./Review of Palaeobotany and Palynology 85 (1995) 319 340

Appendix 1. List of spore and pollen genera Parasaccites Bharadwaj and Tiwari, 1964 Plicatipollenites Lele, 1964 Potonieisporites Bhardwaj emend. Bharadwaj, 1964 Virkkipollenites Lele, 1964 Gondwanopollis Lele and Maithy, 1969 Rimospora Lele and Maithy, 1969 Rugasaccites Lele and Maithy, 1969 Tuberisaccites Lele and Makada, 1972 Parastriopollenites Maheshwari, 1967 Barakarites Bharadwaj and Tiwari, 1964 Striomonosaccites Bharadwaj, 1962 Kamthisaccites Srivastava and Jha, 1988 Goubinispora Tiwari and Rana, 1981 Crucisaccites Lele and Maithy, 1964 Stellapollenites Lele, 1965 Densipollenites Bharadwaj, 1962 Plakfordiaspora Maheshwari and Banerji, 1975 Vestigisporites Balme and Hennelly emend. Tiwari and Singh, 1984

Vasicaspora Schemel emend. Wilson and Venkatachala, 1963 Divarisaccus Venkatachala and Kar, 1966 Sahnites Mehta emend. Tiwari and Singh, 1984 Platysaccus (Naumova) Potonie and Klaus, 1954 Scheuringipollenites Tiwari, 1973 Cuneatisporites Leschik, 1955 Satsangisaccites Bharadwaj and Srivastava, 1969 Klausipollenites Jansonius, 1962 Falcisporites Leschik emend. Klaus, 1963 Crescentipollenites Bharadwaj, Tiwari and Kar, 1974 Striatopodocarpites Soritch and Sedova emend. Bharadwaj, 1962

Striatites Pant emend. Bharadwaj, 1962 Distriatites Bharadwaj, 1962 Faunipollenites Bharadwaj, 1962 Circumstriatites Lele and Makada, 1972 Vertk:ipollenites Bharadwaj, 1962 Hindipollenites Bharadwaj, 1962 Rhizomaspora Wilson, 1962 Primuspollenites Tiwari, 1964 Striasulcites Kar, 1964 Distriamonocolpites Bharadwaj and Sinha, 1969 Tiwariasporis Maheshwari and Kar, 1967 Vittatina Luber emend. Wilson, 1962 Schizopollis Venkatachala and Kar, 1964 Ephedripites Bolkhovitina ex Potonid, 1958 Weylandites Bharadwaj and Srivastava, 1969 Marsupipollenites Balme and Hennelly, 1956 Lueckisporites Potoni6 and Klaus emend. Potoni6, 1958 Corisaccites Venkatachala and Kar, 1966 Guttulapollenites Goubin emend. Venkatachala, Goubin and Kar, 1967

Lunatisporites Leschik emend. Scheuring, 1970 Callumispora Bharadwaj and Srivastava, 1969 Simeonospora Balme, 1970 Ringo.sporites Tiwari and Rana, 1981

339

Jayantisporites Lele and Makada, 1972 Dentatispora Tiwari, 1964 Densoisporites Weyland and Kreiger emend. Dettmann, 1963 Lundbladispora Balme emend. Playford, 1965 Indotriradites Tiwari, 1964 Potonieitriradites Bharadwaj and Sinha, 1969 Gondisporites Bharadwaj, 1962 TeNysispora Vijaya and Tiwari, 1988 Apiculatisporis Potonid and Kremp, 1954 Lophotriletes Naum. ex Potoni6 and Kremp, 1954 Cyclogranisporites Potonid and Kremp, 1954 Verrucosisporites (Ibrahim) Potonid and Kremp, 1954 Horriditriletes Bharadwaj and Salujha, 1964 Godavarisporites Tiwari and Moiz, 1971 Acanthotriletes Naumova ex Potonid and Kremp, 1954 Navalesporites Sarate and Ram-Awatar, 1984 Thymospora Wilson and Venkatachala, 1963 Imparitriletes Tiwari and Singh, 1981 Brevitriletes Bharadwaj and Srivastava emend. Tiwari and Singh, 1981

Lacinitriletes Venkatachala and Kar emend. Tiwari and Singh, 1981

Microbaculispora Bharadwaj, 1962 Microfoveolatispora Bharadwaj, 1962 Didecitriletes Venkatachala and Kar emend. Tiwari and Singh, 1981

References Bharadwaj, D.C., 1962. The miospore genera in the coals of Raniganj Stage (Upper Permian) India. Palaeobotanist, 9(1/2): 68 106. Cornet, B., 1992. Letter to the Editor. Am. Assoc. Stratigr. Palynol. Newslett., 25(1): 4-6. Datta, N.R. and Mitra, N.D., 1982. Gondwana geology of Indian plate-its history of fragmentation and dispersion. Int. Cent. Symp. Geol. Soc. Jpn. Geol. Surv. India, Calcutta, pp. 1 31 (pre-print). Lele, K.M., 1975. Studies in the Talchir flora of Indi~10. Early and Late Talchir miofloras from the West Bokaro Coalfield, Bihar. Palaeobotanist, 22:219 235 Lele, K.M., 1984. Studies in the Talchir flora of India-12. Basal Talchir palynofossils from the Penganga Valley and their biostratigraphical value. In: A.K. Sharma et al. (Editors), Proc. Symp. Evolution Bot. Biostratigr. A.K. Ghosh Commem. Vol., Today & Tomorrow's, New Delhi, pp. 267 283. Lele, K.M. and Chandra, A., 1972. Palynology of the marine intercalations in the Lower Gondwana of Madhya Pradesh, India. Palaeobotanist, 19: 253-262. Lele, K.M. and Makada, R., 1972. Studies in the Talchir flora of India - 7. Palynology of the Talchir Formation in the Jayanti Coalfield, Bihar. Geophytology, 2: 41-73. Scheuring, B.W., 1974. "Protosaccate" structuren, ein weitverbreitetes Pollen-merkmal zur fruhen und mittleren

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