THE DISTRIBUTIOi-J OF DENSOSPORES ?lIAVIS A. BUTTERWORTH* Department of Geo1c'gy, University of SIH'ffleld, United Kingdom ABSTRACT by Butter.worth et aZ. (1964a), and by Staplin Densospores include species of the miospore & Jansonms (1064). These workers divide genera Cingulizonafes (Dybova & Jachowicz), the group into [our genera: Densosporites Crisfafisporifes (Potoni6 & Kremp), De1/sosporifes (Berry) Butterworth, J ansonius, Smith & (Berry) and Radiizonafes Staplin & Jansonius Starlin, in which the cingulum is massive from the literature of Europe and ~orth America, and the exine without prominent ornament; and ElIryzol1ot1'ilefrs i'aumoya, Hymellozonofrilefes Naumova and Tremafo:;onotrilefes Kaumova from Cristatisporitfs (Potonie & Kremp) Butter• the Russian literature. An account is given of \\'orth, Jansonius, Smith & Staplin, the taxonomic position of densospores and of their in 'I hich the cingulum and whole of the morphographic variation in clifferent parts of the column. distal surface are covered with rows or Densosporcs have been recorded in large numbers, cristae of verrucae or spines; Cingl{Zizonates mainly from coal seams, from the Devonian to the (Dybova & J achowicz) Butterworth, J an• Permian of the northern hemisphere. The geo• son ius, Smith & StapJin, in which the graphical distribution of these occurrences forms the subject mattcr of the present paper. Tn general cingnlum is prominc:ntly divided into an densospores first occur in abundance in more inner thick and an outer thin part; and northerly regions and are displaced gradually Radiizonates Staplin & Jansonins in \\'hich southwards during the Carboniferous. They are the divi~ion of the cingulum into thicker most common and have the longest ranges, in areas of slow subsidence. and thinner parts is accompanied by radial striations. These [our genera are included INTRODUCTION by Smith & Butten\'orth (in press) in a new infraturnla - Cingulicavati, described to include trilete cavate spores with simple or THEmiosporesdensosporescharacterizedare a bygroupa thickof ridged laesurae and a comprehensive equa• cingulum or equatorial girdle \\'hich torial thickening (cingulum) or extension may be massive or variously differentiated (zona) of the outer exine layer. Densospo• into thinner and thicker part". These rites and Cristatisporites \\ ere previcusly spores are distinguished from more simple assigned to the infraturma Cingulati Potonie cingulate forms by the two-layered nature & Klaus along with cingulate genera in which of the exine, the intexinc forming the inner the exine is not two-layered, \-"hilst C1'ng1tli• body and the exoexine being expanded zonates and Radiizonates were assigned to equatorially to form the cingulum (BHARAD• the infraturma Cingulizonati Dybova & WA}, 1958; SMITH, 1960; HUGHES, DETT• J achowicz; both infratnrma "'ere designated MANN & PLAYFORD, 1962). The group is for acavate, zonate spores. essentially Carboniferous in age but has also In the U.S.S.R. the species of the group been recorded from the Devonian and the are variously. assignerl among the followiJ]g Permian; it is restricted in occurrence to genera: EuryzollotriZetes Naumova, 1937, the northern hemisphere. with a massive cingulum; Hymenozonotri• The botanical affinities of the densospore letes Naumova, 1937, with a differentiated group are still somewhat obscure, (the cingulum; and Tre11latozonotrilfies Naumova, relevant findings are summarized in BUT• 1937 with an alveolate or punctate cingulum. TERWORTHet aZ., 1964a), hut Chaloner (1958, Luber & Waltz 119+1) include all spores of 1962) and Bharadwaj (1958) have isolated the group in the comprehensive genus various species from the cones of herbace• ZOllotn'Zetes Waltz, 1935 which Potonie & ous lycopsids. K remp (1954) use at subturma level. Very many species of densospores have Ishchenko (1956, 1958) assigns species wi th a been described and they have been sub• massive cingulum to Euryzonotriletes and divided at the generic If'vel in various ways. others, including forms else\vhere assign• Their taxonomic position as applied in ed to Cristatisporites and Cingulizonates, Europe and North America is summarized to HYl1lfnOZol1otriZetes; one 5pecies only is *Present acldress: College of ;\cl\'anced Technology, Bosta breen, Birmingham 4, U.K. 16 BUTTERWORTH - THE DISTRIBUTIOX OF DEKSOSPORES 17 assignerl to Trematozonotriletes _. T. variabilis enough peat had accllmulatrd above the (\Valtz) Ishchenko, with a markedly al\-co• general ground water level. This theory late cingulum. was borne out by Butterworth (1964) who showed that D, sphaerotriallgularis, and THE OCCURRENCE OF DENSOSPORES hence Cl assidurain, is particularly abundant The association of certain densospores in the thick seams which occur towards the with llull coal \ras fIrst noted by Thiessrn stable margins of basins of coal deposition. (1930) and ,,'as confirmed by other ,,'orkers. The prevalence of Iycospores in the more Smith (1957, 1962, 1964) has shmm that in expanded part of the sequence occurring the Upper Westphalian A and Westphalian nearer to the cen tres of basins of deposition B, Densosporites sphacrotriangularis Kosanke, was demonstrated by this author in the characterising his Densospcre PhasE', coalfielns of Central England and by Hac• occurs almost exclusively in bands of cras• quebard & Donaldson (1964) in the Sydney sidnrain, towards the middle and top of Coalfield of Nova Scotia. coal seams. Smith (1962) suggested that the The stratigraphical occurrences of spores peat forming crassidurain was deposited of the densospore group, which are detailed under at IE'ast partly aerobic conditions, in the follo\\'ing sections,' are summarized and that it could have been formed wherever in Text-fig, 1. ..•.v>;n''"v> .... ..•. '"..•. "ij"'":or~';:r0::l;:JCbv>E).P>......,....:or ;:r::l 0> s.Cb"P>Ul::l'\J P> 0 ::l ::lCb t:I "ijzZ9~f;;f;;'::l0e:.:;::f;;.td...,t:I::lSS f;;' 0> <: P> .g>- >- f;;'Cb ::l q~ f;;' n 000000000 Kaiping 000000000000000000000000000000000000000 Tunguska xxxxxxx SpitslJergern xxxxxxx Moscow xxxxxxxxxxxxxxXOOOOOOOOOOOOOO Dnieper -Donetz xxxxxxxxxxxxxxxxxxxxxxxxxx Bug xxxxxxxxxxxxxxxxxxxx Upper Silesia xxxxxxxxxxxxxxxxxxxx Turkey xxxxxxxxxx xxxx xxxx Spain xxxxx xxx North Africa xxxXOOOOOO Saar and Lorraine xxx Plzen xxxx pfalz xxOOOO French limnic xxxxxxxxxOOOO Ruhr xxxxxxxxx Campine xxx Mons xxx Pas de Calais xxxxx xxxxxxxxxxxxxxxxxxXOOoxxx Britain xxxxxxxxxxxxxxxxxxOOO Eastern Canada xxxxxxxxxxxxxxxXOOOOoxx l.:nited States xxxx N.\V. Canada TEXT-FIG, 1 - The distribution of densospores in coal basins from which miospore assemblages have been described. (Crosses denote miospore assemblages in which densospores are present, noughts miospore assemblages in which densospores have not been recorded.) 18 'tHE PALAEOBOTANIST 1. Devonian in the Lovyer Carboniferous are zonate, and of these 60 per cent to 70 per cent are Richardson (1960, 1965) has described thickly fringed, that is have a cingulum. several densospore species from the Middle Of the seven predominant spores listed Old Red Sandstone of north-fast Scotland; Z(lnotriletes crassiptertts Waltz (l.e., PL. 5, although the differentiation of the exim FIG. 64) is a typical Densospr,rites form with into two layers has not been demonstrated a massive cingulum, Zonotriletcs dentatus in these species, they appear to have the Waltz (t. C., PL. 7, FIG. 103) has a cingulum same internal organisation as their Carboni• modified by the presence of small cones and ferous equivalents; they differ fro m Carbo• Z. variablilis (l. C., PL. 5, FIGS. 65, 66) has niferous species in their much gr eater size a punctate cingulum. In the Tunguska (87 to 159 microns, compared wi th 25 to Floral Area, to the south and east, spores 110 microns in the Carboniferous). Two with 'thick massive fringes' are stated to of the species, Densosporites del/on/eus be completely lacking. Richardson and D. oreadensis Richardson, The rather more detailed assemblages which have the characteristic bizonate given by Ishchenko (1958, FIGS. 1-11) for cingulum of Cingulizonates, are orramented sequences in the Dnieper-Donetz Ba:o-in with small bifurcating spines such as occur show that whereas Hymenozonotriletes bialatus on many Devonian spores. The three (Waltz) Ishchenko, a spore with a bizonate species of Cristatisporites describen differ cingulum, and Tre11latozonotriletes var'iablilis from younger species only in their greater (Waltz) Ishchenko are hath common at size. Similar forms have been described some horizons in the Tournaisian they are by Luber & Waltz (1941) hom the Timan more dcminan t in the Visean, where in Peninsular and the Kuznetsk Basin, and bv addition H. cOlllmutatus (Waltz) Ishchenko, Naumova (1953) from the Upper Givetia~ with a bizonate cingulum, and Euryzonotri• of the Russian Platform. letes crassipterus (Waltz) Ishchenko are McGregor (1960) has described a denso• also common. spore, D. erassus, vyith a massive cingulum Jackowicz (1964, PL. 2) records low and of large size, from a coal of Givetian age numbers of Densosporites from the Tournai• in the Canadian Arctic. Since only three sian of the Bug Basin of Eastrrn Poland; specimens of the spore were found this occur• this genus is more common in the Visean rence is perhaps not important; more signi• where species of C1:ngulizonates are also ficant is the record in this Seam of 33 per present. cent of ThoUsporites Butterworth & Wil• Several of the coals and shales examined liams, a genus differing from those of Lhe by Playford (1962, 1963a)