q 2006 Geological Society of America. For permission to copy, contact Copyright Permissions, GSA, or editing@geosociety.org.Geology; April 2006; v. 34; no. 4; p. 265–268; doi: 10.1130/G22187.1; 6 figures. 265

Typical Triassic Gondwanan floral elements in the Upper Permianof the paleotropicsHans KerpAbdalla Abu Hamad*Birgit Vording

Forschungsstelle fur Palaobotanik, Universitat Munster, Hindenburgplatz 57, 48143 Munster,Germany

Klaus Bandel Geologisch-Palaontologisches Institut, Universitat Hamburg, Bundesstrasse 55, 20146 Hamburg, Germany

ABSTRACTPermian floras of the Middle East often show a mixture of Euramerican, Cathaysian,

and Gondwanan elements. We report several species of Dicroidium, a seed fern typicalfor the Triassic of Gondwana, from the Upper Permian of the Dead Sea region. This isthe earliest unequivocal record and the most northerly occurrence of this genus, suggestingthat it may have evolved during the Permian in the paleotropics. With the decline andeventual extinction of the typical Permian Glossopteris flora, Dicroidium may have mi-grated southward. As the climate ameliorated in the Triassic, Dicroidium could havespread farther, eventually colonizing all of Gondwana, where it became one of the dom-inant floral elements.

Keywords: floral provinces, Permian-Triassic transition, migration, pteridosperms.

Figure 1. A: Geographical position of Wadi Himara locality (arrow). B: Stratigraphic subdi-vision of the Upper Permian–Lower Triassic in Dead Sea region with a schematic sectionof lower part of the Um Irna Formation and position of the plant-bearing horizon (arrow).

INTRODUCTIONPaleozoic floral provincialization began in

the Early Carboniferous and culminated in thePermian (Wnuk, 1996). At the end of thePermian, locally, 95% of the peat-formingplant species became extinct (Michaelsen,2002), although it also has been argued thatthe scale and timing of effects of the end-Permian biotic crisis varied markedly betweendifferent regions (Rees, 2002). Several groupsbecame extinct, whereas others suffered astrong decline. Therefore, the discovery of aLate Permian flora from the Middle East withfoliage assignable to the Gondwanan seed ferngenus Dicroidium, which is generally consid-ered to be restricted to the Triassic (Andersonet al., 1999), is most remarkable. This is notonly the earliest record of Dicroidium, butalso the most northerly occurrence of a genusthat became highly successful in Gondwana inthe Triassic.

GEOLOGICAL SETTING AND AGEPlant remains were collected from the Um

Irna Formation in Wadi Himara, Dead Sea re-gion, Jordan (Fig. 1). This 67 m thick clasticsequence unconformably overlies the Cambri-an Um Ishrin Formation (Bandel and Khoury,1981) and consists of a series of predomi-nantly sandy fining-upward sequences withpaleosols with ferruginous pisoliths. In thelower part of the formation, grayish-brownishsiltstone and claystone lenses, with abundantplant material, are interpreted as abandoned

*Current address: The University of Jordan, De-partment of Environmental and Applied Geology,Amman 11942, Jordan; E-mail: Abdalla80@hotmail.com.

channel fills of a distal braided river system(Makhlouf et al., 1991).

The rich and well-preserved microflora isdominated by Falcisporites, occurring in largeclusters and as individual pollen grains. Fal-cisporites is known from the Upper Permian,but percentages of up to 50% are normallyonly found in Triassic rocks. This pollen typehas been attributed to Dicroidium (Balme,1995), the dominant constituent of the WadiHimara macroflora. In addition, nearly sixtyother palynomorph taxa have been identifiedthat clearly indicate a Late Permian age, in-cluding Lueckisporites virkkiae, Klausipollen-ites schaubergeri, Nuskoisporites dulhuntyi,and Jugasporites delasaucei. Another flora

from a nearby locality in the upper part of theUm Irna Formation contains several typicalLate Permian Cathaysian taxa, including Lob-atannularia and Gigantonoclea (Mustafa,2003). The Ma’in Formation, which overliesthe Um Irna Formation with an erosional con-tact, yielded a low-diversity microflora, dom-inated by lycopsid spores (Endosporites pap-illatus, Densoisporites nejburgii) andacritarchs (Veryhachium sp.), an assemblagetypical for the Lower Triassic (Eshet, 1990;Looy et al., 1999).

THE UM IRNA FLORAMummified leaves with excellently pre-

served cuticles are abundant in the lower partof the Um Irna Formation, including up to 30cm long, almost complete, bifurcated fronds.Based on gross morphology and cuticle struc-ture, two species of Dicroidium can readily bedistinguished; bulk macerations have yieldedat least three other possible Dicroidium spe-cies. Although the generic assignment of theplant remains is clear, they cannot be attribut-ed to previously described species of Dicro-idium. Apart from Dicroidium, the plant-bearing beds contain a few unidentifiable fernfragments and relatively large amounts ofcharcoal.

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Figure 2. A–C: Dicroidium sp. A. A: Frond showing typical bifurcation (arrow). B: Cuticle ofa pinna. C: Cuticle of lower pinnule surface stomata with ring of equally strongly cutinizedsubsidiary cells. D–F: Dicroidium sp. B. D: Frond showing typical bifurcation (arrow). E:Pinna apex. F: Cuticle of lower pinnule surface showing stomata with weakly cutinizedlateral subsidiary cells.

Figure 3. Stratigraphic ranges of the genusDicroidium in the Middle East and variousparts of Gondwana. 1—Jordan; 2—Australiaand New Zealand; 3—Antarctica; 4—India;5—South America; 6—southern Africa.

The two species represented by larger spec-imens, here informally named Dicroidium sp.A and Dicroidium sp. B, have bifurcated, bi-pinnate fronds. Dicroidium sp. A (Figs. 2A–2C) has densely spaced, tongue-shaped pin-nules with broadly tongue-shaped terminalpinnules, whereas Dicroidium sp. B (Figs.2D–2F) has narrower, triangular pinnules andnarrow, acute terminal pinnae. The two spe-cies are easily distinguishable by their sto-mata. Dicroidium sp. A has stomata with aring of four to seven equally strongly cutin-ized subsidiary cells, whereas Dicroidium sp.B. usually has stomata with four subsidiarycells, of which the lateral ones are weakly cu-tinized (Figs. 2C and 2F). In both species, cu-ticles are of medium thickness and stomata arenot sunken.

The absence of typical wetland plants andthe low percentage of spores (,20% of thetotal assemblage) are indicative of extrabasin-al vegetation sensu Pfefferkorn (1980). The li-thology points to a tropical summer wet cli-mate; soils with ferruginous pisoliths aretypically formed in hot and humid climateswith a high annual rainfall and a short dryseason (Driessen et al., 2001).

STRATIGRAPHIC AND GEOGRAPHICDISTRIBUTION OF DICROIDIUM

Dicroidium, a corystosperm, is found in theLower Triassic but is more common in theMiddle and Upper Triassic (Anderson and An-derson, 1983). To date, the earliest unequivo-

cal representatives of the genus (D. narrabee-nense, D. zuberi) are known from theNarrabeen Group and the Newport Formation(lower Olenekian) of eastern Australia (Retal-lack, 1977), whereas the last occurrences arein the Rhaetian (Fig. 3). Dicroidium is a typ-ical Gondwanan taxon, occurring at paleola-titudes above 358 S in southern Africa, Aus-tralia, New Zealand, India, Argentina, Chile,southern Brazil, and the Antarctic (Fig. 4).The material reported here thus representsboth the earliest and the most northern occur-rence of a genus that is traditionally regardedas a typical Triassic Gondwanan element.

MIDDLE AND LATE PERMIANFLORAS OF THE MIDDLE EAST

In the Late Permian, the Arabian plate wasconnected to the African plate, and the DeadSea region was a lowland area located in theequatorial belt at ;158 S (Scotese and Lang-ford, 1995; Ziegler et al., 1997). Comparisonswith other Permian floras from the MiddleEast (Fig. 5) are of special interest with regardto paleophytogeography.

In the Middle Permian (Wordian) GharifFormation of central Oman, Euramerican taxa(e.g., the conifer Otovicia hypnoides) are as-sociated with Cathaysian elements such as Gi-gantopteris and Tingia, and with Gondwananelements such as various glossopterids (Ber-thelin et al., 2003). Cathaysian elements alsohave been recorded from Iraq, Saudi Arabia,and Oman. A small flora, exclusively consist-

ing of Cathaysian taxa, is known from the Up-per Permian of western Iraq (Ctyroky, 1973).The flora of the Unayzah Member (Khuff For-mation, early Late Permian) of Qasim Prov-ince, Saudi Arabia, is dominated by pecopter-ids and sphenopsids, suggesting a warm andhumid climate. Several taxa, e.g., Lobatan-nularia and a gigantopterid, are typically Ca-thaysian. The overlying Khuff Member yield-ed taeniopterid leaves and Euramerican-typeconifers (El-Khayal and Wagner, 1985). An-other mixed flora from the Upper Permian ofHazro, southeast Turkey (Wagner, 1962; Ar-changelsky and Wagner, 1983), predominantlyconsisting of sphenopsids and ferns, includesa number of typical Cathaysian taxa, e.g.,Lobatannularia and Gigantopteris, but alsoGondwanan elements such as Glossopterisand Botrychiopsis. Middle and Late Permianfloras from the Middle East thus often show amixture of elements from several floral prov-inces. Not only Cathaysian elements reachedthe limits of their geographical distribution,but also Gondwanan elements such asglossopterids.

In contrast, Late Permian floras from thesouthern Alps (Italy), which are ;258 northof the paleoequator (Scotese, 2002; Ziegler etal., 1997), are dominated by conifers, withpeltasperms and ginkgophytes as additionalelements (Visscher et al., 2001). Plants displayxeromorphic features, i.e., thick cuticles, oftenwith prominent papillae, sunken stomata, andstrongly cutinized subsidiary cells; leaves areoften thick and fleshy. Typical conifer prepol-len known from the Upper Permian of thesouthern Alps also has been found in the UmIrna Formation, e.g., Lueckisporites virkkiae,Jugasporites delasaucei, and Nuskoisporitesdulhuntyi.

GEOLOGY, April 2006 267

Figure 4. Distribution of Dicroidium in the Triassic. Map modified after Scotese (2002).

Figure 5. Paleogeographical map of thePermian of the Paleo- and Neotethys regionwith floras discussed in the text. Map mod-ified from Stampfli and Borel (2001). 1—central Oman; 2—Saudi Arabia; 3—DeadSea, Jordan; 4—Ga’ara, Iraq; 5—Hazro,Turkey.

Figure 6. Paleogeographic map of Late Permian with positions of Wadi Himara flora, north-central Texas flora, and northward expansion of typical Gondwanan floras. Map modifiedfrom Ziegler et al. (1997).

SURVIVORS OF THE END-PERMIANBIOTIC CRISIS

Many plant taxa, such as gigantopterids,Tingia, and Lobatannularia, became extinct atthe end of the Permian, while others dimin-ished dramatically and eventually also per-ished, such as the glossopterids. However, afew Triassic floras with Dicroidium and glos-sopterids are known from South Africa, India,and Australia (e.g., Bharadwaj and Srivastava,1969; Anderson and Anderson, 1985; Holmes,1992). On the other hand, plants with Meso-zoic affinities, primarily Northern Hemisphereconifers and cycads (e.g., Swedenborgia,Dioonitocarpidium), have been described

from the Lower Permian of Texas (DiMicheleet al., 2001). During the Permian, Texas wasa lowland area positioned at a similar latitudeas Jordan, but north of the equator, and sepa-rated from the Southern Hemisphere by amountain chain (Fig. 6), the altitude of whichis still a matter of debate (Fluteau et al., 2001).

In Gondwana, the Permian-Triassic transi-tion is characterized by a shift from cold tem-perate to cool temperate conditions (Retallackand Krull, 1999; Kidder and Worsley, 2004).Based on sedimentological, paleopedological,and paleobotanical evidence, the earliest Tri-assic is considered to have been significantlywarmer and more seasonally dry than the lat-est Permian (McLoughlin et al., 1997; Wardet al., 2000; Michaelsen, 2002). The Early Tri-assic vegetation of Gondwana was dominatedby lycopsids and conifers. More diverse

Dicroidium-dominated floras did not appearprior to the Middle Triassic (Retallack, 1995).

Two seed fern groups were obviously notadversely affected by the end-Permian bioticcrisis, i.e., corystosperms and peltasperms.With the present discovery, the corystospermDicroidium is one of the very few generaknown, to date, that survived the end-Permianbiotic crisis. Dicroidium is not currentlyknown from the lowermost Triassic; however,the floral record of the Lower Triassic is gen-erally poor. During the Early Triassic, the cli-mate became increasingly favorable andGondwana moved farther northward. Corys-tosperms fully expanded during the MiddleTriassic, when they reached their maximumdiversity and distribution, inhabiting largeparts of Gondwana. Peltasperms, a group ofshrubby, mesic to xeric plants, which first ap-peared during the latest Carboniferous (Kerp,1996), are known from the Permian of Eura-merica, Angara, and Cathaysia. This groupalso migrated southward, and appeared inGondwana in the earliest Triassic (Retallack,2002).

CONCLUSIONSAlthough the picture is still incomplete, it

is clear that Middle and Late Permian florasfrom the Middle East contain elements fromseveral floral provinces. This region occurs atthe intersection of several floral provinces, andseems to be crucial for understanding late Pa-leozoic phytogeography. The presence of Di-croidium in the Upper Permian of Jordanshows that corystosperms have evolved dur-ing the Permian, apparently in extrabasinaltropical lowland areas.

268 GEOLOGY, April 2006

Possible causes for the end-Permian bioticcrisis still remain a matter of debate. However,it becomes increasingly clear that thePermian-Triassic transition is marked by a cli-matic change. Global warming resulted in anexpansion of the tropical belt, a poleward shiftof adjacent climate zones, and a contraction ofthe more temperate and cool zones at higherlatitudes. A further complication for thePermo-Triassic is that, in time, continentsmoved northward through climatic belts. Fu-ture studies should focus on the paleotropics,where effects of climatic changes were prob-ably less severe than elsewhere. Unfortunate-ly, very little is known about Late Permianand Early Triassic tropical floras. However, re-cent finds of typical Mesozoic conifers andcycads in Texas and Dicroidium in Jordansuggest that, during the Permian, the tropics,and particularly extrabasinal settings, mighthave been a radiation center for ‘‘Mesozoic’’gymnosperms. With the climatic ameliorationin Gondwana in the Early Triassic, the genusDicroidium may have migrated southward andbecome a dominant constituent of manyGondwanan floras, whereas on the northernside of the mountain belt, conifers and cycadsexpanded northward to colonize large parts ofthe Northern Hemisphere.

ACKNOWLEDGMENTSWe thank M. Berthelin, B. Bomfleur, H. Hass

(Munster), and M. Krings (Munchen) for construc-tive discussions. This project was funded by theDeutsche Forschungsgemeinschaft (grants BA 675/26-1-3 to KB and KE 584/11-1 to HK). A. AbuHamad thanks the Natural Resources Authority(Amman, Jordan) for the opportunity to carry outthis work.

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Manuscript received 20 August 2005Revised manuscript received 25 November 2005Manuscript accepted 5 December 2005

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