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Plant remains from a new cretaceous site in Santa Cruz, Argentina
Review of Palaeobotany and Palynology, 39 (1983) 301--311
301
Elsevier S c i e n c e Publishers B.V., A m s t e r d a m - - Printed in T h e N e t h e r l a n d s
PLANT REMAINS FROM A NEW CRETACEOUS SITE IN SANTA CRUZ, ARGENTINA
ALICIA M
B A L D O N I and T H O M A S
N. T A Y L O R
Centro de lnvestzgaciones en Recursos Geologicos (CIRGEO), Buenos Aires (Argentzna) Department of Botany, The Ohzo State University, Columbus, OH 43210 (U.S.A ) (Received
November 17, 1982 ; revised version accepted March 14, 1983)
ABSTRACT Baldoni, A. M. and Taylor, T. N., 1983. Plant remains from a n e w C r e t a c e o u s site in Santa Cruz, Argentina. Rev. Palaeobot. Palynol., 39:301--311 L e a f remains are described f r o m a n e w l o c a l i t y in the Sprlnghill F o r m a t i o n in Santa Cruz, Argentina. S p e c i m e n s o f Brachyphyllum and t h e n e w speciesPtdophyllum angustus n. sp. and Otozamites archangelskyi n. sp. are described based o n cuticular studies using light and e l e c t r o n m i c r o s c o p y . T h e c o m p o s i t i o n o f the flora reaffirms the Early Cretaceo u s age o f the site and p o i n t s o u t t h e i m p o r t a n c e that megafossils m a y p l a y in biostratigraphic correlations in s o u t h e r n Argentina.
INTRODUCTION Well-preserved leaf remains have been f o u n d in fine-grained sandstones from four plant-bearing levels (Cortfnas and Arbe, 1981). A preliminary analysis of this flora was completed by Archangelsky (1979), who placed it in the Cretaceous, basing his decision on the presence of P t i l o p h y l l u m , Z a m i t e s , O t o z a m i t e s , C y c a d o l e p i s , and B r a c h y p h y l l u m . Previous palynologlcal investigations of the Cretaceous of southern Argentina (Archangelsky et al., 1981) placed the exposure of the Estancia E1 Salitral in " Z o n e B", regarded by some authors as Early Cretaceous (Hauterivian--Barremian base of the Aptian). It is the intent of the present study to describe an interesting florule of Cretaceous age from a new locality in the Springhlll Formation in the northeast of the Province of Santa Cruz (Fig.l). The site is located near the Estancia El Salitral, Departamento de Rio Chico, approximately 100 km southwest of the locality of Perito Moreno, along the road that unites the provincial routes 1209 and 2105. Information on stratigraphy for the Estancia E1 Salitral has already been published by Cortfnas and Arbe (1981). The material described here was collected by personnel of Y.P.F. (Yacimientos Petroliferos Fiscales) in 1979.
0034~667/83/$03.00
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Fig.1 Plant fossil locality m the Springhfll Formation of Santa Cruz, Argentina MATERIAL AND METHODS The specimens consist of well-preserved leaves (Plate I, 1--3), m any with cuticle fragments. Cuticle preparations were obtained after macerating foliage fragments in Schultz solution for a p p r o x i m a t e l y 150 h. After maceration, a p o r tio n o f the cutmle was washed in disUlled water, d e h y d r a t e d t o xylene, and m o u n t e d in HSR (Harleco S y n t h e t m Resin) for light mmroscopy. The re m ammg cutmulax sample was treated ultrasomcally for about 2 s and attached to standard SEM stubs with double-stick tape. Spectmens used m scanning electron m m r os c opy were coated wxth approxi m at el y 100 A of gold and examined m a Hitachi HS-500 instrument. SYSTEMATICS Genus Ptilophyllum Morris 1840 T y p e Species Ptdophyllum acutlfolium Morns 1840
Ptdophyllum angustus n. sp. (Plate I, 2; Plate II, 1--4; Plate III, 1--4) D~agnos~s" Leaves simply pinnate, greater than 8 cm long and a p p r o x i m a t e l y 2 cm wide at the midlevel; principal rachis 2.0 mm wide. Linear pinnae a p p r o x imately 3 cm long and 4 mm wide, s o m ew hat falcate, opposite; pinna apex acute, base asymmetric with margm basiscopic, decurrent, and acroscopic margin hghtly joined. Pmnae continuous to slightly separated, some inserted on the upper surface of the rachls at angles of 45--80 °, less m apical and basal regions o f the leaf Vems parallel and arising from entire region of
303 attachment. Upper cuticle relatively think, smooth and lacking stomata and trichomes; cells large (approximately 40 × 15 um), sinuate anticlinal walls with sinuses up to 5 pm deep. Lower cuticle reflecting similar cells, but with sinuses less conspicuous; stomata arranged in narrow bands between veins and oriented transversely to vein axis, stomata often crowded and sharing adjacent cells. Both solitary and compound papillae between veins, papillae bases oval, apically flattened to rosette-shaped; papillae often surround stoma. Unicellular trichome bases present, 2--3 surrounding each stomatal complex. Guard cells approximately 9 ~m long by 7 ~m wide, with narrow aperture often hidden by overarching papillae. Stomatal complex surrounded by papillae. Periclinal walls of cells internally microgranular, anticlinal walls thick. Trichomes numerous with papillae occupying all of the cell, circular at base, globose on the surface. Strongly cutinized trichomes along the edge. Trichomes of the guard cells strongly curved toward the surface, with guard cells arcuate and sheathed by surrounding papillae. Epidermal cells of rachis slightly rectangular and sinuous, with narrow anticlinal walls. Holotype: Specimen No. 638 deposited in the Paleobotanical Collections, Centro de Investigaciones en Recursos Geologicos (CIRGEO), Buenos Aires, Argentina. Paratypes: Specimens 639,640 and 641 in the above collections. Etymo/ogy: The species designation angustus is proposed to reflect the narrow stomatal bands on the lower surface of this leaf type.
Discussion The essential characters of this species agree with the emended diagnosis provided by Harris (1969a) for Ptilophyllum, which includes the asymmetric pinna base with basiscopic decurrent margin and acroscoplc margin inserted at nearly right angles (Plate I, 2). Absent from the diagnosis by Harris is the characteristic "papilla" that is expanded on the dorsal side (Plate II, 3), and that surrounds the stomatal complex (Archangelsky and Baldoni, 1972). The principal features upon which this new species is based include the small size of the leaf, narrow stomatal zones on the lower surface (Plate II, 1), abundant compound papillae (Plate III, 3), often with lobed apices and numerous, unicellular, oval hair bases (Plate III, 2) surrounding the stomatal complex. Of the several species of Ptilophyllum reported from Argentina, P. angustus appears most similar to foliage remains described by Menendez (1957) as P. hislopii (Oldham) Seward from the Middle Jurassic of Neuqu~n. Several features are consistent between the two species, however, compound papillae are absent from the lower surface of P. hislopii. Ptilophyllum antarcticum (Halle) Seward is known from several localities in southern Argentina (e.g., Antarctic Peninsula -- Halle, 1913; Baquer5 Formation -- Archangelsky and Baldoni, 1972; Springhill Formation -- Archangelsky, 1976; Baldoni, 1979). This species differs from P. angustus in possessing large pinnae, fewer stomata which may be oriented both transversely and obliquely, and both simple and compound papillae with more angular bases and two or three lobes per cell. The presence of larger pinnae may also be used to distingumh
304
PLATE I
:e L
®
305
the new species from P. ghiense reported from the Cretaceous of Paso Roballos (Baldoni, 1977). Additional differences include the relatively few papillae that are simple, notched or closed, solitary trichome bases, and absence of distinctive rows or bands of stomata. Ptilophyllum species that possess morphologically similar pmnae to those o f P . angustus include P. pecten and P. hirsutum, b o t h from the Middle Jurassic of Yorkshire (Harris, 1969a). Although the pinnae ofP. pecten are morphologically similar to P. angustus, they are generally slightly larger and possess weakly defined stomatal bands. In P. hirsutum the pinnae are smaller and the stomata are organized into two or three regular bands. The stomatal apparatus is sunken and the lower cuticle lacks trichome bases. Numerous species of Ptilophyllum, many with epidermal features well preserved, have been described from Jurassic sediments in India (Bose and Kasat, 1970). Several of these species compare closely with P. angustus in general size and m o r p h o l o g y but differ in other features. For example, P. oldhamii J a c o b et J a c o b (1954) has stomata on the lower surface, but the rows are highly irregular, and the individual stomata m a y be either transverse or oblique. In addition, papillae typically overarch and obscure the stomatal aperture. In P. labapurense J a c o b et J a c o b the lower cuticle has simple papillae b u t lacks trichomes. S t o m a t a are in well-defined bands and the stomatal apparatus is surrounded by papillae arising from adjacent cells. Few stomata, weakly cutinized papillae and the general epidermal structure of the rachis are primary characters that can be used to separate P. angustus from P. gladiatum (Bose and Dev, 1957). In addition, in this species the papillae are generally notched or dome-like, and often organized in a ring. Papillae are absent from both lamina surfaces in P. sparsifolium together with the organization of the stomata in a broader zone (Sharma, 1967). Genus Otozamites Braun 1 8 4 2 T y p e Species Filicites bechei Brongniart (see Harris, 1969a)
Otozamites archangelskyi n. sp. (Plate I, 1, 3, 5, 6) Diagnoszs: Pinnate leaves in excess of 8.0 cm long by 1.6 mm wide; rachis 2--2.5 mm wide and striate. Pinnae falcate, alternate and attached to upper PLATE I 1. S e g m e n t o f a b r a n c h of Brachyphyllum ( a r r o w ) a n d y o u n g leaf o f Otozamztes archangelskyz C I R G E O Pb 637. × 1.1. 2. G e n e r a l o r g a n i z a t i o n o f Ptdophyllum angustus pinna. C I R G E O Pb 638. × 1.1. 3 P o r t i o n o f a l e a f o f Otozamttes archangelskyz s h o w i n g b r o a d p i n n a rachls and m o r p h o l o g y of pinnules. C I R G E O P b 636. x 1.4. 4. L o w e r cuticle ofBrachyphyllum sp. × 1000. 5. G e n e r a l o r g a n i z a t i o n o f t h e l o w e r cuticle o f Otozamites archangelskyl x 640. 6. Upper cuticle o f Otozamztes archangelskyz s h o w i n g s i n u o u s cell walls o f e p i d e r m a l cells. × 400.
306
PLATE II
Ptdophyllurn angustus 1. Internal vmw of upper and lower cutmle showing arrangement of stomata. × 300. 2. Internal view of the cuticle of the rach~, x 600. 3. Internal vmw of a stomatal complex showing the fused cells and papillae (arrow) thickened on the dorsal surface. × 1000. 4. Detail of the anticlinal walls of epidermal cells on the upper surface as vmwed from the inside. × 2500. r a c h ~ m a r g m a t a p p r o x t m a t e 4 5 °, p m n a e a p p r o x i m a t e l y 1 . 0 c m l o n g b y 4.0 mm wide with slight auricle on adaxial margin, abaxial margin rounded to slightly decurrent, margin entire and parallel except for rounded tip. Venation free. Upper surface cuticle thick (3--4/~m), hypostomatic and
307
PLATE III Ptdophy llum angustus
1. Internal view of the lower cuticle showing the disposition of stomata, x 300. 2. Morphology of hair bases (arrow) and papillae along the edge of the lower cuticle. x625. 3. Stoma surrounded by papillae. × 600. 4. Epidermal cells along the rachis showing wound region. × 600. r e v e a h n g e p i d e r m a l cell o u t l i n e s ranging f r o m i s o d i a m e t r i c t o r e c t a n g u l a r , b u t l o n g i t u d i n a l l y o r i e n t e d , a n d possessing sinuate anticlinal walls. T r i c h o m e s a n d papillae absent. L o w e r cuticle t h i n (0.5 urn) s h o w i n g irregular cells e l o n g a t e to i s o d i a m e t r i c in o u t l i n e , cells 10 X 30 p m and lacking a precise o r i e n t a t i o n . A n t i c l i n a l walls less s i n u o u s t h a n u p p e r cuticle. S t o m a t a bet w e e n veins, irregular a n d n o t o r g a n i z e d i n t o b a n d s or rows. S t o m a t r a n s v e r s e o r o b l i q u e t o vein; s t o m a t a l a p p a r a t u s slightly s u n k e n , consisting o f delicate
308 guard cells with dorsal thickening; aperture small and often plugged by one or two papillae. Remaining epidermal cells with solitary papillae and globose trichomes. Holotype: Specimen Pb 636 in the Paleobotamcal Collectmns, Centro de Investigaciones en Recursos Geologmos (CIRGEO), Buenos Aires, Argentina. Paratype: Specimen 637 in the above collection. Etymology : The specific name archangelskyi is proposed in honor of the outstanding contributions made to paleobotany by Sergio Archangelsky.
Discussion The description of this specms is based on morphological features (Plate I, 1, 3) since the cuticle is not well preserved. Our inclusion of the leaves in the genus Otozamites is based prmcipally on the presence of the basal auricle, especially on the medium-sized pinnae. Cutmular fragments that were obtained especially from the lower surface suggest the presence of numerous papillae (Plate I, 5) sometimes obscuring the stomatal aperture. Trichomes and trichome bases are more frequent around the stomatal zone. Numerous species of Otozamites have been described from the Jurassic and Cretaceous of Argentma. Several authors have noted that Liassm species do not have similar morphological characteristics in addition to lacking preserved cutmles. In the Late Jurassic, on the other hand, there are a number of c o m m o n species including O. sanctae-crucis Feruglio. Initially described by Feruglio (1951) from the Province of Santa Cruz, this species has also been reported from Chubut (Bonettl, 1963) and Cuenca Austral (Springhlll Formation) (Archangelsky, 1976). The taxon differs from the material described in this account in possessing pinnae that are nearly imbricate and that possess an obtuse apex and well-developed basal auricle. Specimens of O. linearis Halle (1913) from the Late Jurassic (or Early Cretaceous) of the Antarctic Peninsula have pinnae that are larger and falcate with a welldeveloped basal auricle. Otozarmtes parviauriculata reported from the Baquer5 Formation (Early Cretaceous) is also a larger leaf with thicker cuticles and stomata arranged in bands on the abaxial surface (Menendez, 1966). In O. walton~i (Archangelsky and Baldom, 1974) also from the Baquer5 Formation the lower cuticle has epidermal cells with hollow papillae m a subcentral position. Frequently the trichome bases are associated with a ring of specialized, thick-walled cells. The stomata are typically orgamzed into short rows. Other Otozamites species that superficially resemble O. archangelstzyi mclude O obtusus (Lindley et Hutton) and O raciborsk~i Reymanovna from the Jurassic of Poland (Reymanovna, 1963). Specimens of O. obtusus possess smaller pinnae with stomatal and non-stomatal bands nearly indistinguishable. The stomatal apparatus is sunken and the aperture is surrounded by approximately ten papillae that arise from a broad base. The smaller size and absence of trichomes except associated with the stomatal apparatus are features that characterize O. rac~borskii. There are a number o~ Middle Jurassic (Yorkshire) species of Otozamltes
309 that have been delimited by Harris (1969a). For example, O. beanii (Lindley et Hutton) Brongniart m a y be distinguished b y the morphology of the pinnae, density of veins and sunken level of the stomata. In O. simpsonii Harris the lower cuticle contains broad stomatal bands without papillae on the epidermal cells but with numerous trichomes. In this species the stomatal apparatus is deeply sunken and surrounded by numerous folds. The presence of folds around sunken stomata is also a feature of O. mimetes Harris; however, in this species the pinnae are broader with the apex rounded-truncate to rounded-obtuse. In addition the auricle is scarcely developed. Subsidiary cells are small and lack papillae. Recently Person and Delevoryas (1982) described O. hespera Wieland from the Middle Jurassic of Mexico. This species m a y be distinguished by the general size of the pinnae which are attached to the rachis at an angle of 65--80 ° and that possess an auricle somewhat more developed than in O. archange lsk yi.
Genus Brachyphyllum Brongniaxt, 1828 T y p e Species B. mamillare Brongniart, 1828
Brachyphyllum sp. (Plate I, 1, 4) Descriptmn : Branches of two orders. Primary branch approximately 8.5 cm long, 5 m m wide; secondary branch 3.5 cm long by 3 mm wide, inserted at an angle of approximately 45 °. Leaves small, helically inserted in a phyllotactic spiral of approximately 3/8; leaves triangular, 3--3.5 mm long by 4 mm wide at base, 1 mm wide at apex; margin entire, base rhombic, venation not visible. Cuticle thick with isodiametric epidermal cells 35 × 30 #m, periclinal walls straight and up to 6 ~m thick; stomata on both surfaces, irregularly oriented and at times forming poorly defined rows, stomata similar on both surfaces, monocyclic to imperfectly dicyclic, stomatal apparatus oval with slightly sunken guard cells and 4--5 subsidiary cells. Material studied: Specimen Pb 637 in the Paleobotanical Collection, Centro de Investigaciones en Recursos Geologicos (CIRGEO) Buenos Aires, Argentina.
Discussion The cuticle is somewhat corroded and in some regions it is impossible to recognize structure; nevertheless, the material does conform to the generic diagnosis of Brachyphyllum as emended by Harris (1969b). The branches possess leaves that are helically arranged with the total length of the leaf less than the width of the foliar base. Because taxonomically important characters such as cuticle and venation are not well preserved in this material, we have not provided a species description.
310 CONCLUSION These are the first fossil plants that have been described and illustrated f r o m t h i s l o c a l i t y in t h e r e g i o n o f t h e E s t a n c i a E1 S a h t r a l in t h e n o r t h e a s t o f t h e P r o v i n c e o f S a n t a C r u z . T h e p r e s e n c e o f Ptdophyllum, Otozamites a n d Brachyphyllum r e a f f i r m s a n E a r l y C r e t a c e o u s age t o t h e s e d i m e n t s b a s e d o n palynology, paleobotany, stratigraphy and lithology (Archangelsky, 1979; A r c h a n g e l s k y e t al., 1 9 8 2 ; C o r t f n a s a n d A r b e , 1 9 8 1 ) . T h e q u a l i t y o f t h e p r e servation of some of the specimens and diversity of taxa suggest that the p l a n t m e g a f o s s l l s in t h i s r e g i o n m a y p l a y a n I m p o r t a n t r o l e m m o r e a c c u r a t e l y delimiting the Early Cretaceous stratigraphy of the area. ACKNOWLEDGEMENTS We are appreciative to the authoritms of the Yaclmientos Petrohferos Fiscales for authorization to pubhsh these findings. This study was completed during the tenure of a fellowship to the senior author from Consejo Nacional de Investigacmnes Cientificas y Tecmcas, Argentina This research w a s s u p p o r t e d in p a r t b y f u n d s f r o m t h e N a t i o n a l S c m n c e F o u n d a t i o n (DEB-8001803). REFERENCES Archangelsky, S., 1976. Vegetales f6slles de la Formam6n Sprmghill, Cret~emo en el subsuelo de la cuenca Magkllanica, Chile. Ameghmiana, 3 141--158 Archangelsky, S , 1979. Informe Paleobot~mco de muestras de superficm de la Provinma de Santa Cruz Informe m6dito CIRGEO, Buenos Aires. Archangelsky, S. and Baldom, A M., 1972 Revim6n de las Bennett]tales de la Formacibn Baquer6 (Cretacico Inferior), Provinma de Santa Cruz I Ho]as. Rev Mus. de La Plata, N S., Secc. Paleontol , 7 : 195--265 Archangelsky, S., Baldom, A.M , Gamerro, J.C., Palamarczuk, S. and Seller, J., 1981. Palinologia Estratlgr~fica del Cret~cico de Argentina Austral. Dlagramas de Grupos Polinmos del Suroeste de Chubut y Noroeste de Santa Cruz I n VIII Congreso Geologmo Argentino, San Lms, Actas 4 719--742. Baldom, A M., 1977. Ptdophyllum ghu~nse n. sp. Una nueva Bennettltal de Paso Roballos, Provmcia de Santa Cruz. Ameghmiana, 1 4 : 5 3 - - 5 8 Baldoni, A M., 1979 Neuvos elementos Paleoflorfstmos de la Tafoflora de la Formaclbn Springhill, limlte Jur~sico--Cret~cico, Subsuelo de Argentina y Chde Austral Ameghiniana, 16 103--119 Bonetti, M.I R., 1963. F16rula Mesojur~isma de la Zona de Taquetr6n (Cafiadbn del Zaino) Chubut. Rev. Mus. Argent Cienc. Nat "Bernardino Rivadavia", Paleontol., 1--2_ 23--43. Bose, M N. and Dev, S., 1957. A new specms of Ptdophyllum from Bansa, South Rewa Gondwana Basra. The Paleobotanist, 6 : 1 2 - - 1 5 . Bose, M.N and Kasat, M.L., 1970. The genusPtdophyllum in India The Palaeobotanist, 19 115--145. Cortfnas, J. and Arbe, H. 1981 Un nuevo aflorammnto fosilffero de la Formambn Springhill en el noroeste de la Provmeia de Santa Cruz Rev Asoe_ Geol. A r g , 36 212--214_ Feruglio, E_, 1951. Pmnte del Mesozomo della Patagonia. Publ. Ist. Geol Umv. Tormo Fasc_, 1:35--80
311 Halle, T.G., 1913. The Mesozoic Flora of Graham Land en Nordenskjold @. Wiss. Erg. Schwed. Sudpolar Exped. 1901--1903, 3. 1--123. Harris, T.M., 1969a The Yorkshire Jurassic Flora III. Bennettitales. Br. Mus (Nat Hist.), No. 675' 186 pp. Harris, T.M., 1969b. Naming a fossil conifer. J. Sen. Mere. Bot. Soc. Bengal, pp.243--252. Jacob, K and Jacob, Ch., 1954. Cuticular study of Indian Ptdophyllum fronds from Cutch and Jabulpore. Palaeontol. Ind , N.S., 33 1--35 Menendez, C.A., 1957. F16rula Jur~sica del Ba]o de los Baguales en Plaza Huincul, Neuqu~n. Acta Geol. Llnoana, 1. 315--338. Menendez, C.A., 1966. Fossil Bennettitales from the Tic6 Flora, Santa Cruz Province, Argentina. Bull. Br Mus. (Nat. Hlst ) Geol , 12 1--42. Person, C.P. and Delevoryas, T , 1982. The Middle Jurassm flora of Oaxaca, Mexico. Palaeontographma, 180B 82--119. Reymanowna, M., 1963. The Jurassm flora from Grojecnear Gracow, in Poland. I. Acta Palaeobot., 4 9--48 Sharma, B D., 1967. Inveshgatlons on the Jurassm flora of Rajmahal Hills, India. 3. A review of the genus Ptilophyllum of Morris, with descriptions of two new specms from Amarjola in the Rajmahal Hills. Palaeontographica, 1 2 0 B 139--150.
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Elsevier S c i e n c e Publishers B.V., A m s t e r d a m - - Printed in T h e N e t h e r l a n d s
PLANT REMAINS FROM A NEW CRETACEOUS SITE IN SANTA CRUZ, ARGENTINA
ALICIA M
B A L D O N I and T H O M A S
N. T A Y L O R
Centro de lnvestzgaciones en Recursos Geologicos (CIRGEO), Buenos Aires (Argentzna) Department of Botany, The Ohzo State University, Columbus, OH 43210 (U.S.A ) (Received
November 17, 1982 ; revised version accepted March 14, 1983)
ABSTRACT Baldoni, A. M. and Taylor, T. N., 1983. Plant remains from a n e w C r e t a c e o u s site in Santa Cruz, Argentina. Rev. Palaeobot. Palynol., 39:301--311 L e a f remains are described f r o m a n e w l o c a l i t y in the Sprlnghill F o r m a t i o n in Santa Cruz, Argentina. S p e c i m e n s o f Brachyphyllum and t h e n e w speciesPtdophyllum angustus n. sp. and Otozamites archangelskyi n. sp. are described based o n cuticular studies using light and e l e c t r o n m i c r o s c o p y . T h e c o m p o s i t i o n o f the flora reaffirms the Early Cretaceo u s age o f the site and p o i n t s o u t t h e i m p o r t a n c e that megafossils m a y p l a y in biostratigraphic correlations in s o u t h e r n Argentina.
INTRODUCTION Well-preserved leaf remains have been f o u n d in fine-grained sandstones from four plant-bearing levels (Cortfnas and Arbe, 1981). A preliminary analysis of this flora was completed by Archangelsky (1979), who placed it in the Cretaceous, basing his decision on the presence of P t i l o p h y l l u m , Z a m i t e s , O t o z a m i t e s , C y c a d o l e p i s , and B r a c h y p h y l l u m . Previous palynologlcal investigations of the Cretaceous of southern Argentina (Archangelsky et al., 1981) placed the exposure of the Estancia E1 Salitral in " Z o n e B", regarded by some authors as Early Cretaceous (Hauterivian--Barremian base of the Aptian). It is the intent of the present study to describe an interesting florule of Cretaceous age from a new locality in the Springhlll Formation in the northeast of the Province of Santa Cruz (Fig.l). The site is located near the Estancia El Salitral, Departamento de Rio Chico, approximately 100 km southwest of the locality of Perito Moreno, along the road that unites the provincial routes 1209 and 2105. Information on stratigraphy for the Estancia E1 Salitral has already been published by Cortfnas and Arbe (1981). The material described here was collected by personnel of Y.P.F. (Yacimientos Petroliferos Fiscales) in 1979.
0034~667/83/$03.00
© 1983 Elsevier Scmnce Publishers B.V.
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PLANTAS
Fig.1 Plant fossil locality m the Springhfll Formation of Santa Cruz, Argentina MATERIAL AND METHODS The specimens consist of well-preserved leaves (Plate I, 1--3), m any with cuticle fragments. Cuticle preparations were obtained after macerating foliage fragments in Schultz solution for a p p r o x i m a t e l y 150 h. After maceration, a p o r tio n o f the cutmle was washed in disUlled water, d e h y d r a t e d t o xylene, and m o u n t e d in HSR (Harleco S y n t h e t m Resin) for light mmroscopy. The re m ammg cutmulax sample was treated ultrasomcally for about 2 s and attached to standard SEM stubs with double-stick tape. Spectmens used m scanning electron m m r os c opy were coated wxth approxi m at el y 100 A of gold and examined m a Hitachi HS-500 instrument. SYSTEMATICS Genus Ptilophyllum Morris 1840 T y p e Species Ptdophyllum acutlfolium Morns 1840
Ptdophyllum angustus n. sp. (Plate I, 2; Plate II, 1--4; Plate III, 1--4) D~agnos~s" Leaves simply pinnate, greater than 8 cm long and a p p r o x i m a t e l y 2 cm wide at the midlevel; principal rachis 2.0 mm wide. Linear pinnae a p p r o x imately 3 cm long and 4 mm wide, s o m ew hat falcate, opposite; pinna apex acute, base asymmetric with margm basiscopic, decurrent, and acroscopic margin hghtly joined. Pmnae continuous to slightly separated, some inserted on the upper surface of the rachls at angles of 45--80 °, less m apical and basal regions o f the leaf Vems parallel and arising from entire region of
303 attachment. Upper cuticle relatively think, smooth and lacking stomata and trichomes; cells large (approximately 40 × 15 um), sinuate anticlinal walls with sinuses up to 5 pm deep. Lower cuticle reflecting similar cells, but with sinuses less conspicuous; stomata arranged in narrow bands between veins and oriented transversely to vein axis, stomata often crowded and sharing adjacent cells. Both solitary and compound papillae between veins, papillae bases oval, apically flattened to rosette-shaped; papillae often surround stoma. Unicellular trichome bases present, 2--3 surrounding each stomatal complex. Guard cells approximately 9 ~m long by 7 ~m wide, with narrow aperture often hidden by overarching papillae. Stomatal complex surrounded by papillae. Periclinal walls of cells internally microgranular, anticlinal walls thick. Trichomes numerous with papillae occupying all of the cell, circular at base, globose on the surface. Strongly cutinized trichomes along the edge. Trichomes of the guard cells strongly curved toward the surface, with guard cells arcuate and sheathed by surrounding papillae. Epidermal cells of rachis slightly rectangular and sinuous, with narrow anticlinal walls. Holotype: Specimen No. 638 deposited in the Paleobotanical Collections, Centro de Investigaciones en Recursos Geologicos (CIRGEO), Buenos Aires, Argentina. Paratypes: Specimens 639,640 and 641 in the above collections. Etymo/ogy: The species designation angustus is proposed to reflect the narrow stomatal bands on the lower surface of this leaf type.
Discussion The essential characters of this species agree with the emended diagnosis provided by Harris (1969a) for Ptilophyllum, which includes the asymmetric pinna base with basiscopic decurrent margin and acroscoplc margin inserted at nearly right angles (Plate I, 2). Absent from the diagnosis by Harris is the characteristic "papilla" that is expanded on the dorsal side (Plate II, 3), and that surrounds the stomatal complex (Archangelsky and Baldoni, 1972). The principal features upon which this new species is based include the small size of the leaf, narrow stomatal zones on the lower surface (Plate II, 1), abundant compound papillae (Plate III, 3), often with lobed apices and numerous, unicellular, oval hair bases (Plate III, 2) surrounding the stomatal complex. Of the several species of Ptilophyllum reported from Argentina, P. angustus appears most similar to foliage remains described by Menendez (1957) as P. hislopii (Oldham) Seward from the Middle Jurassic of Neuqu~n. Several features are consistent between the two species, however, compound papillae are absent from the lower surface of P. hislopii. Ptilophyllum antarcticum (Halle) Seward is known from several localities in southern Argentina (e.g., Antarctic Peninsula -- Halle, 1913; Baquer5 Formation -- Archangelsky and Baldoni, 1972; Springhill Formation -- Archangelsky, 1976; Baldoni, 1979). This species differs from P. angustus in possessing large pinnae, fewer stomata which may be oriented both transversely and obliquely, and both simple and compound papillae with more angular bases and two or three lobes per cell. The presence of larger pinnae may also be used to distingumh
304
PLATE I
:e L
®
305
the new species from P. ghiense reported from the Cretaceous of Paso Roballos (Baldoni, 1977). Additional differences include the relatively few papillae that are simple, notched or closed, solitary trichome bases, and absence of distinctive rows or bands of stomata. Ptilophyllum species that possess morphologically similar pmnae to those o f P . angustus include P. pecten and P. hirsutum, b o t h from the Middle Jurassic of Yorkshire (Harris, 1969a). Although the pinnae ofP. pecten are morphologically similar to P. angustus, they are generally slightly larger and possess weakly defined stomatal bands. In P. hirsutum the pinnae are smaller and the stomata are organized into two or three regular bands. The stomatal apparatus is sunken and the lower cuticle lacks trichome bases. Numerous species of Ptilophyllum, many with epidermal features well preserved, have been described from Jurassic sediments in India (Bose and Kasat, 1970). Several of these species compare closely with P. angustus in general size and m o r p h o l o g y but differ in other features. For example, P. oldhamii J a c o b et J a c o b (1954) has stomata on the lower surface, but the rows are highly irregular, and the individual stomata m a y be either transverse or oblique. In addition, papillae typically overarch and obscure the stomatal aperture. In P. labapurense J a c o b et J a c o b the lower cuticle has simple papillae b u t lacks trichomes. S t o m a t a are in well-defined bands and the stomatal apparatus is surrounded by papillae arising from adjacent cells. Few stomata, weakly cutinized papillae and the general epidermal structure of the rachis are primary characters that can be used to separate P. angustus from P. gladiatum (Bose and Dev, 1957). In addition, in this species the papillae are generally notched or dome-like, and often organized in a ring. Papillae are absent from both lamina surfaces in P. sparsifolium together with the organization of the stomata in a broader zone (Sharma, 1967). Genus Otozamites Braun 1 8 4 2 T y p e Species Filicites bechei Brongniart (see Harris, 1969a)
Otozamites archangelskyi n. sp. (Plate I, 1, 3, 5, 6) Diagnoszs: Pinnate leaves in excess of 8.0 cm long by 1.6 mm wide; rachis 2--2.5 mm wide and striate. Pinnae falcate, alternate and attached to upper PLATE I 1. S e g m e n t o f a b r a n c h of Brachyphyllum ( a r r o w ) a n d y o u n g leaf o f Otozamztes archangelskyz C I R G E O Pb 637. × 1.1. 2. G e n e r a l o r g a n i z a t i o n o f Ptdophyllum angustus pinna. C I R G E O Pb 638. × 1.1. 3 P o r t i o n o f a l e a f o f Otozamttes archangelskyz s h o w i n g b r o a d p i n n a rachls and m o r p h o l o g y of pinnules. C I R G E O P b 636. x 1.4. 4. L o w e r cuticle ofBrachyphyllum sp. × 1000. 5. G e n e r a l o r g a n i z a t i o n o f t h e l o w e r cuticle o f Otozamites archangelskyl x 640. 6. Upper cuticle o f Otozamztes archangelskyz s h o w i n g s i n u o u s cell walls o f e p i d e r m a l cells. × 400.
306
PLATE II
Ptdophyllurn angustus 1. Internal vmw of upper and lower cutmle showing arrangement of stomata. × 300. 2. Internal view of the cuticle of the rach~, x 600. 3. Internal vmw of a stomatal complex showing the fused cells and papillae (arrow) thickened on the dorsal surface. × 1000. 4. Detail of the anticlinal walls of epidermal cells on the upper surface as vmwed from the inside. × 2500. r a c h ~ m a r g m a t a p p r o x t m a t e 4 5 °, p m n a e a p p r o x i m a t e l y 1 . 0 c m l o n g b y 4.0 mm wide with slight auricle on adaxial margin, abaxial margin rounded to slightly decurrent, margin entire and parallel except for rounded tip. Venation free. Upper surface cuticle thick (3--4/~m), hypostomatic and
307
PLATE III Ptdophy llum angustus
1. Internal view of the lower cuticle showing the disposition of stomata, x 300. 2. Morphology of hair bases (arrow) and papillae along the edge of the lower cuticle. x625. 3. Stoma surrounded by papillae. × 600. 4. Epidermal cells along the rachis showing wound region. × 600. r e v e a h n g e p i d e r m a l cell o u t l i n e s ranging f r o m i s o d i a m e t r i c t o r e c t a n g u l a r , b u t l o n g i t u d i n a l l y o r i e n t e d , a n d possessing sinuate anticlinal walls. T r i c h o m e s a n d papillae absent. L o w e r cuticle t h i n (0.5 urn) s h o w i n g irregular cells e l o n g a t e to i s o d i a m e t r i c in o u t l i n e , cells 10 X 30 p m and lacking a precise o r i e n t a t i o n . A n t i c l i n a l walls less s i n u o u s t h a n u p p e r cuticle. S t o m a t a bet w e e n veins, irregular a n d n o t o r g a n i z e d i n t o b a n d s or rows. S t o m a t r a n s v e r s e o r o b l i q u e t o vein; s t o m a t a l a p p a r a t u s slightly s u n k e n , consisting o f delicate
308 guard cells with dorsal thickening; aperture small and often plugged by one or two papillae. Remaining epidermal cells with solitary papillae and globose trichomes. Holotype: Specimen Pb 636 in the Paleobotamcal Collectmns, Centro de Investigaciones en Recursos Geologmos (CIRGEO), Buenos Aires, Argentina. Paratype: Specimen 637 in the above collection. Etymology : The specific name archangelskyi is proposed in honor of the outstanding contributions made to paleobotany by Sergio Archangelsky.
Discussion The description of this specms is based on morphological features (Plate I, 1, 3) since the cuticle is not well preserved. Our inclusion of the leaves in the genus Otozamites is based prmcipally on the presence of the basal auricle, especially on the medium-sized pinnae. Cutmular fragments that were obtained especially from the lower surface suggest the presence of numerous papillae (Plate I, 5) sometimes obscuring the stomatal aperture. Trichomes and trichome bases are more frequent around the stomatal zone. Numerous species of Otozamites have been described from the Jurassic and Cretaceous of Argentma. Several authors have noted that Liassm species do not have similar morphological characteristics in addition to lacking preserved cutmles. In the Late Jurassic, on the other hand, there are a number of c o m m o n species including O. sanctae-crucis Feruglio. Initially described by Feruglio (1951) from the Province of Santa Cruz, this species has also been reported from Chubut (Bonettl, 1963) and Cuenca Austral (Springhlll Formation) (Archangelsky, 1976). The taxon differs from the material described in this account in possessing pinnae that are nearly imbricate and that possess an obtuse apex and well-developed basal auricle. Specimens of O. linearis Halle (1913) from the Late Jurassic (or Early Cretaceous) of the Antarctic Peninsula have pinnae that are larger and falcate with a welldeveloped basal auricle. Otozarmtes parviauriculata reported from the Baquer5 Formation (Early Cretaceous) is also a larger leaf with thicker cuticles and stomata arranged in bands on the abaxial surface (Menendez, 1966). In O. walton~i (Archangelsky and Baldom, 1974) also from the Baquer5 Formation the lower cuticle has epidermal cells with hollow papillae m a subcentral position. Frequently the trichome bases are associated with a ring of specialized, thick-walled cells. The stomata are typically orgamzed into short rows. Other Otozamites species that superficially resemble O. archangelstzyi mclude O obtusus (Lindley et Hutton) and O raciborsk~i Reymanovna from the Jurassic of Poland (Reymanovna, 1963). Specimens of O. obtusus possess smaller pinnae with stomatal and non-stomatal bands nearly indistinguishable. The stomatal apparatus is sunken and the aperture is surrounded by approximately ten papillae that arise from a broad base. The smaller size and absence of trichomes except associated with the stomatal apparatus are features that characterize O. rac~borskii. There are a number o~ Middle Jurassic (Yorkshire) species of Otozamltes
309 that have been delimited by Harris (1969a). For example, O. beanii (Lindley et Hutton) Brongniart m a y be distinguished b y the morphology of the pinnae, density of veins and sunken level of the stomata. In O. simpsonii Harris the lower cuticle contains broad stomatal bands without papillae on the epidermal cells but with numerous trichomes. In this species the stomatal apparatus is deeply sunken and surrounded by numerous folds. The presence of folds around sunken stomata is also a feature of O. mimetes Harris; however, in this species the pinnae are broader with the apex rounded-truncate to rounded-obtuse. In addition the auricle is scarcely developed. Subsidiary cells are small and lack papillae. Recently Person and Delevoryas (1982) described O. hespera Wieland from the Middle Jurassic of Mexico. This species m a y be distinguished by the general size of the pinnae which are attached to the rachis at an angle of 65--80 ° and that possess an auricle somewhat more developed than in O. archange lsk yi.
Genus Brachyphyllum Brongniaxt, 1828 T y p e Species B. mamillare Brongniart, 1828
Brachyphyllum sp. (Plate I, 1, 4) Descriptmn : Branches of two orders. Primary branch approximately 8.5 cm long, 5 m m wide; secondary branch 3.5 cm long by 3 mm wide, inserted at an angle of approximately 45 °. Leaves small, helically inserted in a phyllotactic spiral of approximately 3/8; leaves triangular, 3--3.5 mm long by 4 mm wide at base, 1 mm wide at apex; margin entire, base rhombic, venation not visible. Cuticle thick with isodiametric epidermal cells 35 × 30 #m, periclinal walls straight and up to 6 ~m thick; stomata on both surfaces, irregularly oriented and at times forming poorly defined rows, stomata similar on both surfaces, monocyclic to imperfectly dicyclic, stomatal apparatus oval with slightly sunken guard cells and 4--5 subsidiary cells. Material studied: Specimen Pb 637 in the Paleobotanical Collection, Centro de Investigaciones en Recursos Geologicos (CIRGEO) Buenos Aires, Argentina.
Discussion The cuticle is somewhat corroded and in some regions it is impossible to recognize structure; nevertheless, the material does conform to the generic diagnosis of Brachyphyllum as emended by Harris (1969b). The branches possess leaves that are helically arranged with the total length of the leaf less than the width of the foliar base. Because taxonomically important characters such as cuticle and venation are not well preserved in this material, we have not provided a species description.
310 CONCLUSION These are the first fossil plants that have been described and illustrated f r o m t h i s l o c a l i t y in t h e r e g i o n o f t h e E s t a n c i a E1 S a h t r a l in t h e n o r t h e a s t o f t h e P r o v i n c e o f S a n t a C r u z . T h e p r e s e n c e o f Ptdophyllum, Otozamites a n d Brachyphyllum r e a f f i r m s a n E a r l y C r e t a c e o u s age t o t h e s e d i m e n t s b a s e d o n palynology, paleobotany, stratigraphy and lithology (Archangelsky, 1979; A r c h a n g e l s k y e t al., 1 9 8 2 ; C o r t f n a s a n d A r b e , 1 9 8 1 ) . T h e q u a l i t y o f t h e p r e servation of some of the specimens and diversity of taxa suggest that the p l a n t m e g a f o s s l l s in t h i s r e g i o n m a y p l a y a n I m p o r t a n t r o l e m m o r e a c c u r a t e l y delimiting the Early Cretaceous stratigraphy of the area. ACKNOWLEDGEMENTS We are appreciative to the authoritms of the Yaclmientos Petrohferos Fiscales for authorization to pubhsh these findings. This study was completed during the tenure of a fellowship to the senior author from Consejo Nacional de Investigacmnes Cientificas y Tecmcas, Argentina This research w a s s u p p o r t e d in p a r t b y f u n d s f r o m t h e N a t i o n a l S c m n c e F o u n d a t i o n (DEB-8001803). REFERENCES Archangelsky, S., 1976. Vegetales f6slles de la Formam6n Sprmghill, Cret~emo en el subsuelo de la cuenca Magkllanica, Chile. Ameghmiana, 3 141--158 Archangelsky, S , 1979. Informe Paleobot~mco de muestras de superficm de la Provinma de Santa Cruz Informe m6dito CIRGEO, Buenos Aires. Archangelsky, S. and Baldom, A M., 1972 Revim6n de las Bennett]tales de la Formacibn Baquer6 (Cretacico Inferior), Provinma de Santa Cruz I Ho]as. Rev Mus. de La Plata, N S., Secc. Paleontol , 7 : 195--265 Archangelsky, S., Baldom, A.M , Gamerro, J.C., Palamarczuk, S. and Seller, J., 1981. Palinologia Estratlgr~fica del Cret~cico de Argentina Austral. Dlagramas de Grupos Polinmos del Suroeste de Chubut y Noroeste de Santa Cruz I n VIII Congreso Geologmo Argentino, San Lms, Actas 4 719--742. Baldom, A M., 1977. Ptdophyllum ghu~nse n. sp. Una nueva Bennettltal de Paso Roballos, Provmcia de Santa Cruz. Ameghmiana, 1 4 : 5 3 - - 5 8 Baldoni, A M., 1979 Neuvos elementos Paleoflorfstmos de la Tafoflora de la Formaclbn Springhill, limlte Jur~sico--Cret~cico, Subsuelo de Argentina y Chde Austral Ameghiniana, 16 103--119 Bonetti, M.I R., 1963. F16rula Mesojur~isma de la Zona de Taquetr6n (Cafiadbn del Zaino) Chubut. Rev. Mus. Argent Cienc. Nat "Bernardino Rivadavia", Paleontol., 1--2_ 23--43. Bose, M N. and Dev, S., 1957. A new specms of Ptdophyllum from Bansa, South Rewa Gondwana Basra. The Paleobotanist, 6 : 1 2 - - 1 5 . Bose, M.N and Kasat, M.L., 1970. The genusPtdophyllum in India The Palaeobotanist, 19 115--145. Cortfnas, J. and Arbe, H. 1981 Un nuevo aflorammnto fosilffero de la Formambn Springhill en el noroeste de la Provmeia de Santa Cruz Rev Asoe_ Geol. A r g , 36 212--214_ Feruglio, E_, 1951. Pmnte del Mesozomo della Patagonia. Publ. Ist. Geol Umv. Tormo Fasc_, 1:35--80
311 Halle, T.G., 1913. The Mesozoic Flora of Graham Land en Nordenskjold @. Wiss. Erg. Schwed. Sudpolar Exped. 1901--1903, 3. 1--123. Harris, T.M., 1969a The Yorkshire Jurassic Flora III. Bennettitales. Br. Mus (Nat Hist.), No. 675' 186 pp. Harris, T.M., 1969b. Naming a fossil conifer. J. Sen. Mere. Bot. Soc. Bengal, pp.243--252. Jacob, K and Jacob, Ch., 1954. Cuticular study of Indian Ptdophyllum fronds from Cutch and Jabulpore. Palaeontol. Ind , N.S., 33 1--35 Menendez, C.A., 1957. F16rula Jur~sica del Ba]o de los Baguales en Plaza Huincul, Neuqu~n. Acta Geol. Llnoana, 1. 315--338. Menendez, C.A., 1966. Fossil Bennettitales from the Tic6 Flora, Santa Cruz Province, Argentina. Bull. Br Mus. (Nat. Hlst ) Geol , 12 1--42. Person, C.P. and Delevoryas, T , 1982. The Middle Jurassm flora of Oaxaca, Mexico. Palaeontographma, 180B 82--119. Reymanowna, M., 1963. The Jurassm flora from Grojecnear Gracow, in Poland. I. Acta Palaeobot., 4 9--48 Sharma, B D., 1967. Inveshgatlons on the Jurassm flora of Rajmahal Hills, India. 3. A review of the genus Ptilophyllum of Morris, with descriptions of two new specms from Amarjola in the Rajmahal Hills. Palaeontographica, 1 2 0 B 139--150.