OCCURRENCE OF PSEUDOBORNIA NATHO T II ALASKA*

SERGIUS H. MAMAY U.S. Geological Survey, Washington 25, D.C.

ABSTRACT and informally renamed it Pseudobornia morna/a. However, the material described A small collection of fossil plan ts from north­ eastern Alaska contains Pseudobornia ursina Nath­ by Dawson exhibits none of the features orst, which aids in the differentiation of age of rocks peculiar to Pseudobornia; instead, it almost in a difficult stratigraphic section. This is not only certainly represents stem fragments of As/ero­ the first occurrence of Pseudobornia in the western caLamites Schimper, which is characterized hemisphere, but also the first verifiable occurrence since the original discovery of Pseudobornia on Bear by direct superposition of all the ribs at the Island. nodes. Since the material studied by White is no longer available for examinatlon, and N 1894 A. G. Nathorst described a series particularly in view of the apparent absence of fossil floras from the Arctic regions, of diagnostic leaves, I concur with Read I including an assemblage from the Upper (1953, p. 16) in viewing White's identification Devonian rocks of Bear Island, south of of Pseudobornia as unsubstantiated. Spitzbergen. This flora was predominantly Zimmerman (1959, p. 224) mentions occur­ a fern-lycopod association, such as commonly rences of Pseudobornia in Ireland and eastern characterizes Upper Devonian floras in other Siberia, but he has informed me (written parts of the world. However, it was of communication, 1961) that these reported unusual interest inasmuch as it contained a occurrence_ are erroneous. peculiar arthrophyte unknown until then; Source oj Jo,{aterial- The Alaskan Pseudo­ Nathorst named this plant Pseudobornia born£a was identified in one of three small ursina. Several years later (1902) Nathorst collections that were referred to me for described supplemental material of Pseudo­ fossil identification and age determination bornia. also from Bear Island, so that there by W P. Brosge and H. N. Reiser of the is now available a fairly detailed description U.S. Geological Survey. The fossils were and several excellent illustrations of both found while the collectors were conducting a fertile and sterile parts of this plant. geological mapping proj ect in the Christian Subsequent to Nathorst's publications, the and Arctic quadrangles, north-eastern Alaska, genus was not discovered elsewhere until and were submitted with the specific intent 1960, when it was found in Alaska. Two of utilizing them, jf possible, in determining earlier occurrences are recorded, but in each the enclosing sediments as either Devonian case the identification of Pseudobornia is or Cretaceou. The collection numbers and accompanied by doubt. Magdefrau (1936) geographic locations are: described several small articulate stem frag­ Be 672. 68°20' N, 146°19' Vi (Shale ments from the Upper Devonian "Braun­ interbedded with micaceous quartzites) wacken" of Lerchenberg and Weinberg in Be 661. 67°51' N, 145°24' W (Black Thuringia, Germany. Magdefrau identified shale interbedded with graywacke) this material as P. ursina, and although the Rr 635. 68°15'30" N, 144°08' W (Black stem fragments correspond reasonably well shale immediately below Kanayut con­ with some of those described bv Nathorst, glomerate and above thrust fault) Magdefrau's collection contained none of According to the collectors (BROSGE and the unique foliage that characterizes Pse~tdo­ REISER, written communications, 1961) the bornia. Even more suspect is \iVhite's beds indicated above were originally deter­ identification (in Kindle, 1912, p. 209) of mined as Devonian on the basis of inverte­ Pseudobornia in the pper Devonian Huron brate fossils, and are contained in a sequence Member of the Ohio Shale, of northern Ohio, of slates, shales, sandstones, quartzites, and and the Genesee Formation and other Devo­ graywackes. This sequence is conformably nian units in New York State. White overlain by the Kanayut Conglomerate, of examined specimens reputedly identical with known Late Devonian age. The stratigraphy Sir :William Dawson's Calam1:tes inorna/us is complicated by faulting, and lithologic

*Publication authorized by the Director, U.S. Geological Survey. 19 20 TH' PALAEOBOTANIST

similarities to rocks of known Cretaceous age Plant material in the most significant of in the Chandalar quadrangle, as well as the the three collections, Rr 635, is contained general scarcity of diagnostic fossils, create in a hard, thin-bedded black shale, rich in difficulties in distinguishing the Devonian detached foliar material of Pseudobornia rocks from the Cretaceous. The field prob­ and axial fragments that probably repre­ lem is summarized by Brosge and Reiser sent the stems and branches of the same (written communication, 1961) as follows: plant. The stem fragments are preserved " The Devonian age identification of collec­ as coalified compressions or as mere impres­ tion 60 ABe 661 was particularly important sions on the bedding surfac s. The longest as the rocks in which they occur are less is 16 cm. long and 2 cm. wide, but the entire metamorphosed than the rocks of known width is not represented since th:: specimen Devonian age in the immediately adjoining is split longitudinally. Stem fragments are areas. Although the sequence of lithologic as much as 4 cm. in width, but most speci­ units indicates the rocks at 60 ABe 661 to mens are only 6-7 mm. wide. Some of the be of Devonian age, the fact that they lie broader specimens are ornamented with more or less on strike with a belt of very longitudinal ribs, which may be as much as similar sedimentary rocks of known Creta­ 4 mm. in width. These show only slight ceous age coupled with the complex struc­ relief, and probably vary according to the ture of the area prohibits positive Devonian degree of pre-preservational decortication age assignment \vithout the fossil control." of the stems. The smaller stems show faint Description of the M aterial- Collection Be longitudinal striations, very closely set. 672 consists of only a few small slabs of Except for a few nodal compressions with black, micaceous shale in which there are evidence of branch scars. the st m fragments no identifiable plant megafossils. It con­ are otherwise lacking in distinctive features. tains a number of small, coalified remnants A few of the fragments show swollen nodes, of slender woody plant axes, but these show some of which exhibit faint depressions that no diagnostic features. are probably branch scars (FIG. 3); in this Collection Be 661 consists of several slabs feature they agre well with Pseudobornia of dark grey to black shale with abundant stems figured by Nathorst. The specimen plant debris on the irregular bedding sur­ shown in Fig. 3 has a distinct node, to either faces. The plant fragments are mostly side of which is Qttached the basal part of a small, coalified films of undeterminable lateral appendage. vVhether these were origin. No leaves are recognizeahle, but leaves or branchlets, however, cannot be there are a number of longitudinally ridged determined. This is the only specimen axial fragments, the largest of these measur­ showing nodal ::tttachment. ing about 4 cm. in width. A few of these Foliar material is abundant in the collec­ have swollen nodes and evidence of large tion, although most of the specimens are nodal branch scars, which together with the small fragments. Almost every slab con­ coarse surface ribbing, suggest that these are tains one to several leaf specimens. These secondary or smaller axes of Pseudobornia. are preserved as high rank coalifications in The most important specimen in this which cuticular material and cell structure small collection is illustrated in Fig. 1. have been destroyed, so that only the out­ It is a short fragment of a rather stout, lines are preserved. There is little contrast partly decorticated lycopod axis, measuring between the black compressions and black 4 cm. in width. Its surface is ornamented matrix, and it is difficult to examine the with closely set, spirally arranged, axially specimens under direct light. However, elongated leaf cushions that compare closely the fossils have a graphitic lustre that is with some of the specimens illustrated by lacking in the containing matrix, and obli­ Nathorst (1902, d. PL. 10, FIG. 4) as Bothro­ que lighting causes the plants to stand out dendron (Cyclostig'ma) !?iltorkense Haughton. sufficiently well that their outlines are Although a positive identification of the easily observed and the leaves may be photo­ Alaskan specimen is not possible because of graphed with reasonable success. faulty preservation, the specimen is at Repeated division of the leaf blade in an least recognizable as a representative of the essentially dichotomous manner to produce Paleozoic arborescent lycopod complex, and two to several, long, narrow, wedge-shaped as such is sufficient to idel1tify the enclosing lobes is one of the distinguishing features sediment as Devonian rather than Cretaceous. of Pseudobornia, and some of the larger MAMAY -OCCURRENCE OF PSEUDOBORNIA )1ATHORST IN ALASKA 21 specimens in the Alaska collection show this On the specific level there is no evident feature fairly well. The specimen shown in basis for separating the Ala,;ka specimens Fig. 7, an apparently complete leaf 5 em. from the type material from Bear Island. long, shows a deep basic division into two Quantitative features of the Alaska speci­ main lobes, each of which is again. deeply mens fall well within the range of variation dissected. The resultant lobes are in turn shown by the type species, sothat pending the marginally incised in an irregular manner, discovery of material that ·would controvert producing relatively narrow lobes, all direct('d this decision, the Alaska mat rial is identified apically at a very narrow angle of decurrence. here as Pseudobornia ursina Nathorst. Marginal laciniation or fimbriation of the The collection is deposited in the Paleo­ lamina, which constitutes the most diagno­ zoic plant collections of the U.S. National stic vegetative feature, is plainly shown by Museum, Washington. nc. all the Alaska specimens. The whole mar­ Discussion - The identification of Pseudo­ gin of every foliar fragment is deeply dis­ bornia ursl:na in the Devonian of Alaska sected into numerous narrow unbranched represcnts the first positive evidence of the lobes, which are 0·15-0·30 mm. wide and prescnce of the order Pseudoborniales on 3-10 mm. long. The ultimate lobes are the North American continent or, indeed, closely spaced and so numerous that they in the western hemisphere. In this regard impart to the laminae a plumose appearance. mention should be made of Prosseria grandis As in the case of the penultimate lobes, the Read (1953), described from the pper ultimate lobes are directed apically at a very Devonian Genesee Grollp of New York narrow and graceful angle of clecurrence. Statt'. Pross('.Y1:a ,vas an articulate plant Their consistentty welJ-ordered alignment with much enlarged nodes and long, grass­ and completeness discourage interpretation like leaves. Read recognized similarities of these specimens as distantly transported between this plant and other articulates and plant material. Rather, the specimens like­ considered the possibility that it was pseudo­ ly grew at, or very near to, the present site bornialean; however, it was only with ques­ of preservation. tion that he referred it to that group. Since There is no evidence of the original vena­ Read's publication, no additional information tion, although it seems reasonably safe to has been uncovered in regard to the morpho­ presume a basic dichotomous vascular sys­ logy or systematic position of Prosseria, so tem. Whether or not each of the many that the Alaska occurrence of Pseudohornia narrow marginal lobes received a veinlet is remains the only unCiuestionable discovery not known, but to judge from their extreme­ of pscmlobornialean plants in the western ly narrow proportions, it seems likely that h ~mispherc. Although the Alaska mate­ they were largely unvascularized, with the rial provides no ne,v information on the veinlets ending short of the ultimate lobes. morphology or phylogenetic relationships The cuticles are not preserved, nor is of Pseudobornia, its occurrence entails seve­ attachment of leaves clearly demonstrated ral points of signifinance. in this material. As the second known occurrence of Pseudo­ In spite of the absence of larger, more bornia, this establishes for the genus a con­ complete specimens that would demonstrate siderable geographic range, for even though the fruiting habit and other morphological both the Alaska and Bear Island localities features of the Alaska plants, the leaf frag­ lie within the Arctic Circle, they occur on ments compare so closely with leaves of nearly opposite longitudinal meridians and Nathorst's original material of PSMtdobornia are separated from each other by a distance that the identification of the Alaska mate­ of more than two thousand miles. The rial may be made without hesitation. The significance of this fact, of course - coupled peculiar form of the leaves is unique to with the apparently conspecific identity of Pseudobornia, and this is clearly duplicated in the Alaska and Rear Island plants - is the AlaSka specimens (compare FIGS, 2, 4, 5, 6 that Pseudobornia, one of the 'strange' and 7 with the leaves shown on NATHORST'S elements in the Upper Devonian land flora, PLS. 7, 8). Furthermore, the association with was not an endemic, but a plant with a con­ articulate stem fragments, again duplicative siderable geographic range indicative of of some of Nathorst',; specimens (compare some means of communication between FIG. 3 with N.'\TllORSr's Pc 8, FIGS. 10, 11), Bear Island and Alaska. Thus another of strengthens the leaf identification. the primitive plant groups falls into the 22 THE PALAEOBOTA'KIST

general pattern of widespread geographic northern Alaska and north-western Canada distribution of Devonian floras in the nor­ and presumably receiving sediments from thern hemisphere. It now seems possible the Barrow platform to the north; to the that Alaska will eventually produce Devo­ south of the geosynclinal belt is shown an nian plant assemblages of diversity compar­ extensive magmatic geosynclinal belt, which able to those of the better known Devonian covers more than the southern half of Alaska. plant localities in Europe and eastern North Inasmuch as the Pseudobornia locality lies America. Furthermore, positive demonstra­ well within the hypothetical limits of the tion of the fact that Pseudobornia was not amagmatic geosynclinal belt, it becomes limited in geographic distribution to the obvious that (1) this geosynclinal belt con­ immediate environs of Bear Island permits tained emergent land areas, sufficiently per­ anticipation of future, additional discoverie, sistent to permit population by a land flora, of Pseudobornt"a in association with the at least during Late Devonian time, or (2) a Upper Devonian Archaeopt~ris flora, which more southern extension of the Barrow may provide valuable information on the Platform, which would encompass the posi­ botanical nature and relationships of the tion of the plant deposit, is indicated. genus and order, and perhaps on the early Whichever of the foregoing interpretations history of the articulate plants in general. proves to be correct, it is virtually certain From the paleogeographic point of view, that the land on which the Alaska Pseudo­ the Alaska occurrence of Pseudobornia consti­ bornia grew occupied the same geographic tutes an additional item in evidence of a position as that of the present-day fossil site. Devonian land mass that occupied part of The fossil deposit evidently represents the the position of present-day Alaska. The remains of an essentially pure stand of physical evidence of this was summarized Pseudobornia, preserved at or at least very in 1951 by Payne and others, who illustrated near the original habitat. Extensive trans­ (1951, FIG. 23) the geologic conditions that portation before burial is doubtful, to judge hypothetically obtained from the Middle from the undamaged appearance of the fine Devonian through the Permian. Their map marginal funbriations of the leaves. More­ includes a large northern land mass, the over, if the deposit represents a basin of Barrow Platform, which extends southward deposition that received plant material from to overlap the northern edge of Alaska and distant areas containing a variety of habitats, northwest Canada. The platform is delimit­ it is probable that the sediments would now ed on the south by a broad amagmatic contain a greater variety of plant remains geosynclinal belt, trending east-west across than just one recognizable species.

REFERENCES

KINDLE, E. M. (1912). The stratigraphic relations Ibid. 36(3). of the Devonian shales of northern Ohio. Amer. PAYNE, T. G. & OTHERS (1951). Geology of the journ. Sci. 4th ser. 34(200): 187-213. Arctic slope of Alaska. U.S. Geol. Surv. Oil and MAGDEFRAU, KARL (1936). Die Flora des Oberde­ Gas Inv. Map OM-126. vons in ostlichen Thiiringer Waldo Bel:heften Z. READ, C. B. (1953). Prosser;a grandis, a new genus Bot. Centralblatt 56 (B) (1/2): 213-228. and new species from the Upper Devonian of NATHORST, A. G. (1894). Zur PaUiozoischen Flora New York. Washington A cad. Sci. jour. 43(1): der Arktischen Zone. Kungl. Svenska Vetensk.­ 13-16. Akad. Handl. 24(4). ZIMMERMAN, WALTER (1959). Die Phylogenie der Idem (1902). Zur Fossilen Flora der Polarlander. Pflanzen. Stuttgart.

EXPLANATION OF PLATE 1

1. Partly decorticated lycopod stem fragment 4. Foliar fragments of Pseudobornia ursina, show­ from locality Be 661. U.S.N.M. 41849. x 1. ing typical dichotomous division and marginal (All other figured specimens from locality fimbriations. U.S.N.M.41852. x 2. Rr 635.) 5. Part of slab showing two large leaf fragments 2. Fragment of axis at right, with two leaves of and several smaller ones. Specimen at right shown Pseudoborn1:a ursina converging toward axis from enlarged as Fig. 4. U.S.N.M.41852. x 1. left. U.S.N.M. 41850. x 1. 6. Large leaf fragment, showing repeated dicho­ 3. Part of axis showing enlarged node with faint tomous division and marginal fimbriations. U.S. branch scars and basal parts of two appendages N.M. 41853. x 1. attached at node. U.S.N.M.41851. X 2. 7. Same specimen as Fig. 6. X 2. , r.\~IA Y - PL:\'IE 1 TIlle: P.\LAEOnOT,\:\IST, VOL. 11

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