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Padgettia, a New Ge~Us Based on Fertile Ieurop Teroid

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Padgettia, a New Ge~Us Based on Fertile Ieurop Teroid PADGETTIA, A NEW GE~US BASED ON FERTILE IEUROP­ TEROID FOLIAGE FROM THE PEH.MIAN OF TEX \S* SERGIUS H. MAi:vIAY .S. Geological Survey, \>Vashington 25, D.C. s Permian floras become increasingly to several adnate, sef'd-like fructifications, well-known, it becomes more apparent probably imbedded in the lZLIllina, aligned A that the Permian period produced parallel to the venation on either side of the many peculiar plant forms that defy close midrib. comparison with plants of the present. Pad­ Fronds at kast once pinnat ; pinnules gettia, the new genus to be described here, is apparently isophyllous, long (12 em. or morC') represen ted by one of these morphologically and relatively narrow (to 3 cm. wide) with anomalous types of plants. entire margins and cordate bases, the bminae The material upon which this account is tapering gently to acut apices. Pinnule based was found in an assemblage of plant midribs to 3 mm. wide, finely --triated; lateral compressions collected in 1939 by Charles veins clo ely spac d, departing decurrently B. Read, U.S. Geological Survey, at a locality at an angle of approximately 30 degrees, " approximately 2 miles northwest of Pad­ arching to meet pinnule margins nearly gett ", in Young County, Texas, (U.s.G.S. perpendicularly, usually forking once within Palaeobotanical Locality Number 8967). a short distance of the midrib According to the geological map of Young Fructifications ovoid, elliptical or pyriform, County (Plummer and Fuqua, 1937), out­ from 2·5 to 9·0 mm. long and 2·0 to 5·0 mm. crops in that area lie within the Lower wide, usually borne one or two, occasionally Permian Moran formation of the Wichita several to a pinnule, being evel Iy . paced group, at an undetermined distance above in the latter instances. Fructifications the Dothan limestone of former usage. oriented lengthwise along decurrence of The abundant plant remains are preserved lateral veins, with broadest ends toward in a fine-grained, dark grey shale with well­ pinnule midrib, some in contact with midribs, developed fissility. In some specimens the and apparently attached to laminae or preservation is so fine that epidermal cell imbedded in them throughout their length; patterns are visible under high magnification; apices of some fructifications extended as in most specimens, however, only a very thin either broad or constrictecl " beaks", tt'rJDi­ film of dark brown carbonaceous matter nating truncately at pinnule margins. remains, which presents a fairly sharp colour Holotype ~ US.l\.iVI 41165 a and b contrast with the shale matrix. (counterparts): figures 3 and 4. The plant assemblage is fairly diverse, Descriphon of the .11 aterial ~ The Padgett containing representatives of Cordaites, Bow­ collection contains nearly a hundred seedlike manites, Sphenophyllum, Pecopteris, Sphenop­ fructifications, distributed among 52 pinnul s. teris, Odontopteris, and Padgett·ia. Although Most of the fertile pinnules, which in the the Pueblo formation, which underlies the sterile form have a decidedly neuropteroid Moran, is known to contain Callipteris, this appearance, have only one fructification each, Permian " guide" fossil is not recognizable but 12 have 2 each, 7 hZLve 3 or more, and in the Padgett collection. Padgettia seems one small pinnule fragment, 3 em. long and to have dominated the flo rule , and on the 1·7 em wide, has 7. The holotypc, the basis of more than fifty fertile pinnules, its counterparts of whi.ch are shown in Fig'. 3 known features are diagnosed as follows: and 4, is an incomplete pinnule 6 cm. long and 2 cm. wide, with 8 fructifications. Sterile Padgettia readi n. gen. and sp. pinnules apparently do not differ from fertile ones in regard to size, outline or v nation. Combined Diagnosis ~ Plants "vith large The fructifications are all flattened to the neuropteroid pinnules; pinnules bearing one extent that they create hardly any relief on 'Publication authorized by the Director, U.S. Geological Survey. 53 54 THE PALAEOBOTANIST the leaf surface; in this flattened condition It is likely, however, that the frond was at they are mostly ovoid or pyriform. There is least bipinnately compound. no evidence of pedicellate attachment. Most Interpretation - The problem of morpho­ specimens occur on the laminar area between logical interpretation of the fertile pinnules the midrib and pinnule margin, but a few of Padgettia has been discussed with various have their basal ends in contact with the colleagues, and although the possibility that midrib; none of these, however, extend from the ovoid objects represent abnormaliti s of one side of the midrib to the other. unknown origin has been considered, the Most of the fructifications occur nearer to consensus favors their interpretation as fruc­ the base than the tip of the pinnule. Their tifications. My personal opinion is that orientation conforms closely with the angle Padgett1:a is a pteridosperm, and that the of decurrence of the lateral veins, so that the pinnules described here are the ovuliferous fructifications are typically situated with parts. Reasons for this interprdation are: their long axes directed apically at a wide 1. The presence in the Padgett collection angle to the midrib, with their broadest ends of a large number of the ovoid objects, and toward the midrib. Where several fructi­ their complete restriction to one species of fications are present on the same side of the plants in this reasonably diverse flora, seems midrib, they tend to be approximately evenly convincing evidence that they constitute a spaced and, as shown in Figs. 3 and 4, they natural growth feature of the pinnules. may also occur in opposite pairs. 2. The strict conformity of the long axes Although not all of the fructifications of the objects with the decurrence of the extend as far as the pinnule margin, many lateral veins of the supporting pinnules have beak-like apical prolongations that indicates a preferential orientation along the extend as far as, but not beyond, the pinnule ultimate vascular strands, as in linear fern margin. The beak may be narrow and son. In adition to this feature, the relatively constricted, giving the fructification its even spacing and opposite pairing in the few pear - or urnlike outline, or it may conti­ observable instances are also suggestive of nue unconstricted to the pinnule margin as reproductive structures rather than pathologi­ an extension of the greatest width of the cal effects, insect damage, or other artificially fructification. induced abnormalities. The outline of the fructification is delimited 3. Their shape is seed-like and their size is by a more or less pronounced furrow - evi­ comparable to that of any number of the dentlya compression border - in the matrix. smaller pteridospermous seeds. They are This surrounds a small, flat, lens-like body of too large for micro.'porangia or isoporangia, sediment that can be flaked off to expose the and there is no evidence to indicate that they opposite side of the specimen; this obviously are multisporangiate sori. represents the filling by sediment of an The most unusual and perhaps morphologi­ originally hollow structure on the pinnule. cally most significant aspect of the seeds is Some of the furrows are filled with fusinized the manner in which their apical ends are carbonaceous matter, suggesting that the truncated exactly at the pinnule margins. original structure had considerable substance; Had the seeds been pedicellate or, if sessile, some specimens are almost completely cover­ had they been attached only at their basal ed by a thin film of coal, but others lack ends, it is unlikely that their apical ends this, having lost it to their counterparts would have coincided exactly with the pinnule when the matrix was split. margins in all instances. The marginal No spores or cuticular remains were found truncation of the seeds thus suggests that in any of the fructifications, although several they were imbedded within the lamina and specimens were sacrificed for matrix dispersal as the seeds matured, slits opened along the and examination of residues; nor was it pinnule margins to permit access of pollen possible to determine definitely whether the to the micropyles and shedding of the matured fructifications were borne on the lower or seeds from the sporophylls. The compressed upper surface of the pinnule, although they " beaks" would thus represent the fossilized generally appear to have been on the lower avenue of access between the seeds and the surface. outside of the sporophylls. The degree of frond division is not known Further support of this interpretation lies because only one specimen was found with in the evidence of complete sessility or adna­ two pinnules attached to an ultimate rachis. tion of the seeds as demonstrated by their ).!.\MA'l-PADGETTlA, Ai EW GlZ~ "S ON FE! TILlZ l"E -R PTEROTD FOLIAGE 55 consistently decurrent alignment. Had the Discussion - The taxonomic implications seeds been stalked or incompletely attached of Pad"ettia are important, becau. e in its to the lamina, some of them certainly "vould sterile stat a pinnule of thi plant i. indistin­ have been preserved in other positions relative guishable from i reuropteris foliage. In leaf to the bLrral vein~. shape and venation, Padgettia readi bear a Another point worthy of consideration is clo-e re· mblance to . europteris permiana the r lationshi p between size of s eds and S Jlarcls (1908), from the Permian of Kan.-a.-, development of the apical beak. The small st and the t"..·O .-pecies would po..-ibly be r ­ seeds arc unbeakrrl, while the be. t dev loped gardecl as conspecific if the fructifications beaks occur on the largest ~eeds, sugge. ting of the PJ.dgett mat rial wer not known. that all seeds did not mature at on 0., and It must be pointeel out, of cour.
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