Conifer Wood from the Upper Jurassic of Utah; I, Xenoxylon Morrisonense Sp

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Conifer wood from the Upper Jurassic of Utah; I, Xenoxylon morrisonense sp. nov.

William D. Tidwell

David A. Medlyn

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BYU ScholarsArchive Citation Tidwell, William D. and Medlyn, David A., "Conifer wood from the Upper Jurassic of Utah; I, Xenoxylon morrisonense sp. nov." (1975). Faculty Publications. 1452. https://scholarsarchive.byu.edu/facpub/1452

This Peer-Reviewed Article is brought to you for free and open access by BYU ScholarsArchive. It has been accepted for inclusion in Faculty Publications by an authorized administrator of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. Amer. J. Bot. 62(2): 203-208. 1975.

CONIFER WOOD FROM THE UPPER JURASSIC OF UTAH PART I: XENOXYLON MORRISONENSE SP. NOV.1

DAVID A. MEDLYN AND WILLIAM D. TIDWELL Department of Botany, Brigham Young University, Provo, Utah 84602

ABSTRACT A new species of conifer wood, Xenoxylon morrisonense, is described from the Morrison Formation on the Colorado Plateau. It is compared with other species of Xenoxylon, with X. latiporosum being the closest. Xenoxylon morrisonense differs from X. latiporosum in its marked indentations, simple pits on the horizontal and tangential walls of ray cells, absence of crassulae, presence of wood parenchyma, and thin borders on podocarpoid type crossfield pits. The origin of the septa in the tracheids is summarized, and the possible affinity of Xeno- xylon with the Podocarpaceae is considered.

THE PETRIFIEDWOOD considered in this report Tangential-Rays 2-35 cells high, commonly was collected from the Upper Jurassic Morrison 10-15 (Fig. 3), cells squarish, largest about Formation on the Colorado Plateau in southcen- 25 fLm; rays mostly uniseriate, frequently partiaUy tral Utah. The locality, near Clay Point, Garfield biseriate, rarely entirely biseriate; tracheids with Co., Utah2, was shown to us by Mr. and Mrs. numerous septa (Fig. 3, 7), tangential pitting Thomas Hopkins of Hanksville, Utah. The site absent. is relatively undisturbed and contains several well- preserved specimens. Petrified woods are 10caUy Radial- Tracheary pits uniseriate, round, com- abundant in the Morrison Formation. Many of monly vertically flattened (Fig. 4, 9), mostly these woods are highly siliceous and variously contiguous with adjacent pits, rarely separate, colored and are often poorly preserved. However, pit diam varies from 16 fLm in late wood to 27-30 some specimens are well preserved and are ge- fLm in early wood, pit aperture circular 5-7 fLm, nerically comparable to previously reported fos- pit border nearly fills entire width of the lumen; silwoods of similar age. crassulae absent, contact line of adjacent pits com- The specimen, a trunk measuring approximately monly appear dark brown; tracheids with numer- twenty-two in. at its widest diam, was embedded ous septa (Fig. 3, 4, 7, 8); ray crossfields with in a pebble conglomerate (Fig. 1). The axis is one (Fig. 5), often two (Fig. 10), large podo- partly silicified and contains areas of structurally carpoid pits 10-16fLm in diam, with elliptic aper- preserved cells favorable for study. However, the tures (Fig. 5); pit borders thin, crescent shaped, pith, primary xylem, and phloem are not pre- some crossfields appear to be occupied by a large served. Pinus silvestris-type pit (although the lack of border could be a feature of preservation); hori- DIAGNOSIS: Xenoxylon morrisonensesp. n.- zontal and tangential waUs of ray parenchyma Transverse section-Growth rings narrow, some- pitted with numerous indentations; tangential walls timesindistinct (Fig. 2), 2-3 cells wide, late wood of ray parenchyma typically meet horizontal tracheids tangentially flattened, angular to waUs mostly at right angles; ray tracheids absent; rounded, 20 fLm in diam, lumens round to elliptic; axial parenchyma throughout stem and commonly early wood tracheid size varies from 25-50 fLm in appear as swollen bulbous cells (Fig. 6, 8). diam,tracheids more or less regularly aligned, oc- casionaUy with smaUer tracheids interspersed Holotype: Brigham Young University Reposi- among the larger; cell walls 5-6 fLm thick in both tory 926. early and late wood; wood parenchyma present but not readily observable in cross section; rays Horizon: Upper Jurassic Morrison Formation. uniseriate,occasionally biseriate, separated by one to five rows of tracheids, commonly four; hori- DISCUSSION-Xenoxylon was proposed by Got- zontal walls of ray parenchyma pitted with 1-2 han (1905) for specimens of wood previously de- simplepits. scribed by Cramer (1868) as Pinites latiporosus from Green Harbor, Spitzbergen. The diagnostic 1 Received for publication 16 January 1974. 'U.S. Geo!. Surv. Map, Hall Mesa Quadrangle, T 35 characteristics of this genus are (1) the occur- S, R 10 E, N. E. 1,4 Sec. 24. rence of at least some vertically flattened and 203 204 AMERICAN JOURNAL OF BOTANY [Vol. 62

travers ely elongated pits on the radial walls of thin border on some of the crossfield pits of our tracheids; (2) the absence of pitting on the hor- specimen is also a notable difference. izontal and tangential walls of rays; and (3) large Wood parenchyma is present in Xenoxylon oval pits on the radial walls of the ray cells. morrisonense but not in X. latiporosum. The lat- Xenoxylon spans a comparatively narrow geo- ter species has small oval or circular pits on the logical range (Middle Triassic to Lower Creta- tangential walls of the late wood tracheids (Shima- ceous). However, geographically it is widely kura, 1936), which are missing in the former. distributed in northern latitudes. Since 1905, Seward (1919) stated there are no resin canals an increasing number of occurrences have been or xylem parenchyma in Xenoxylon. However, cited. In 1906, Gothan reported Xenoxylon from X. hopeiense Chang, recorded from China in the Jurassic of Poland, and Holden (1913) de- 1929, is said to differ from other described spe- scribed it from the Jurassic of Yorkshire, En- cies of Xenoxylon in having crassulae, wood pa- gland. The oldest occurrence was cited by Fliche renchyma, occasional biseriate rays, and resinous ( 1910) from Middle Triassic strata of France. cells in the rays. Xenoxylon has been reported from the Jurassic of Thus, on the basis of marked indentations, pit- China (Chang, 1929; Gothan and Sze, 1933), ted horizontal and tangential walls of ray cells, Korea (Ogura, 1931), Japan and Manchuria absence of crassulae, thin borders on podocar- (Shimakura, 1936; Watari, 1960), Jurassic of poid-type crossfield pits, and wood parenchyma, France (Grambast, 1953), and also the Creta- X. morrisonense is proposed as a new species. ceous of Alaska (Arnold, 1952). The origin of the septa in tracheids has been Five previously described species of Xenoxylon reviewed and postulated by several authors. Pen- are X. latiporosum (Cramer) Gothan, X. phyllo- hallow (1907) attributed similar structures to cladoides Gothan, X. conchylalianum Fliche, X. resin plates which divided the tracheids. Con- hopeiense Chang, and X. barberi (Seward) Kdiu- rad (1910) and Record (1918) proposed that sel. Xenoxylon morrisonense shows a close af- these septa are of parenchymatous origin. Thom- finity to X. latiporosum on the basis of the diag- son (1913) described septate tracheids from the nostic tracheid septation which is lacking in the xylem of the Araucarineae. Some of these are other four species. These thin, transverse septa- partial septations composed of secondary walls, tions were figured by Gothan (1905), Ogura whereas others are complete septations which (1944), Arnold (1952), and Watari (1960) in Thomson described from Agathis bornensis and their reports of X. latiporosum. Xenoxylon mor- A. alba. In connection with the latter, Thomson risonense differs from X. latiporosum in the ab- (1913, p. 25) stated "... there are often paren- sence of crassulae, and in having marked in- chyma cells replacing some of the septated parts. dentations and simple pits on both the horizontal This may go so far that the whole tracheid is re- and tangential walls of the rays (Fig. 5). The placed parenchyma, but usually there is some latter condition is not compatible with the generic vestige of the origin of these vertical series of cells designation, but it is not inconsistent with the from the tracheary elements." He also mentioned admixture of characters associated with transi- that septate tracheids and parenchyma cells re- tional conifers. Shimakura (1936) and Watari place tracheids in vertical rows in the wood of (1960) has stated that true crassulae, as seen in Abies and also in association with the resin canals abietinean wood, are never present in X. laii- of pines. Jeffery (1925) considered septate tra- porosum, although the contact between the bor- cheids to be intermediate stages between tracheids ders of two adjacent pits are often dark brown. However, Arnold (1952) pointed out distinct and wood parenchyma, as viewed in Picea, and crassulae that had apparently been overlooked that they represent a primitive form of axillary by authors who previously described this species. parenchyma. He further mentioned that tracheids He described these crassulae as being narrow be- in the roots and cones of pine are occluded by in- cause of the crowded condition of the pits. The growing parenchyma cells (Jeffery, 1917), al- tracheal pitting of X. morrisonense is always con- though this condition is not normal to the vegeta- tiguous (Fig. 9), but the pits are not always verti- tive axis of living pines. Jane (1956) discussed cally flattened and horizontally elongated as in horizontal biconcave resin plates characteristic of X. latiporosum. The conspicuous presence of a the genera Agathis and Araucaria. He explained

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Fig. 1-6. Xenoxylon morrisonense. BYU 926 holotype. 1. Holotype specimen imbedded in pebble conglomerate. 2. Transverse section, illustrating the homogenity of xylem and a narrow growth ring. X 145. 3. Tan- gential section, showing the septa in the tracheids. X 125. 4. Radial section, demonstrating pitting and tracheal septation. X 195. 5. Radial section, showing indentations and crossfield pitting. X 575. 6. Radial section, showing swollen axillary parenchyma. X 285. February, 1975] MEDLYN AND TIDWELL-WOOD OF XENOXYLON 205 206 AMERICAN JOURNAL OF BOTA Y [Vol. 62

Fig. 7-10. Xenoxylon morrisonense. BYU 926 holotype. 7. Tangential section, showing epta. X 490. 8. Radial section. Notice septa and swollen axillary parenchyma. X 155. 9. Radial section, howing contiguous, flattened pits. X 490. 10. Radial section, showing crossfield pitting. X 490.

that if these plates were cut medianly, the tracheid wood parenchyma into some tracheids. The pres- would appear to be full of resin; whereas if cut ence of tylose formation in some species of living near the upper boundary, there would appear to conifers (Batton and Boureau, 1965; Ogura, be a resinous lining to the tracheid lumen. 1944) makes the presence of these structures in Both Ogura (1944) and Watari (1960) dis- fossil woods entirely possible. cussed the origin of septate tracheids in Xeno- Arnold (1952), commenting on the tylosoid xylon latiporosum and concluded they were ty- nature of the septa in his specimen of Xenoxylon losoid. The septa were formed by the fusion of latiporosum, remarked, "... they are present in membranes of adjacent tyloses which originated such great numbers that connection of all them by the projecting of the parenchymatous ray cells with ray cells does not seem quite possible." This through the ray pit. Watari (1960) demonstrated is also the case in Xenoxylon morrisonense; al- the development of the tylose from its origin as a though some septa definitely appear to have bladder until it formed the septum. In Araucar- formed from tyloses, others appear as transverse oxylon mineense and A. huzinamiense Ogura walls (Fig. 7). Ogura (1944) postulates a simi- (1960) observed the projection of the contents of lar condition as being due to the lateral mem- February, 1975] MEDL Y AND TIDWELL-WOOD OF XENOXYLON 207 branes of the tylo es coming in close contact with genera which show affinity to the modern family the tracheid walls and thereby obscuring the ty- Podocarpaceae. It was primarily intended to re- lose-like structure. The horizontal portion of the place Gothan's two genera Podocarpoxylon and membranes then appear as thin, flattened plates Phyllocladoxylon. Earlier Stopes' (1915), recog- crossing the tracheid lumen. Ogura (1960) con- nizing the inconsistencies between these two cluded that differences in tracheid septation may genera, lumped them into the single genus Podo- be due to species variation and the age of the carpoxylon. Seward in his original diagnosis de- wood. fined Mesembrioxylon as a coniferous wood in which the features are similar to those associated Affinities-As is the case with many Mesozoic with Cupressinoxylon, although the xylem paren- conifers, placing Xenoxylon in an extant family chyma mayor may not be present. Another or genus is rather problematical. In tracing coni- feature that Seward described for the former fers through the geologic past, the Mesozoic, genus is the presence of one or two large simple especially Middle Mesozoic, would have to be pits, or in some species two or more smaller bor- termed "The Age of Conifers." It was at this dered pits, in the crossfields. In either case, the time that conifers were undergoing rapid diver- apertures are more vertical than horizontal. gence. The species of this Era had retained many When Gothan established Xenoxylon he did ancestral characteristics, but at the same time not mention its affinities with the Podocarpaceae many of the characteristics which denote modern but alluded to some relationship by naming one forms were evolving. Hence some authors have species X. phyllocladoides. Seward (1919) also called them "transitional conifers." If classifica- recognized a relationship when he said that Xen- tion of these species were based only on primitive oxylon showed a close resemblance to Gothan's characters, which some authors have done, all genus Phyllocladoxylon (=M esembrioxylon). would be diagnosed as araucarian or, probably Krausel (1939) proposed Protophyllocladoxy- more accurately, cordaitalean conifers. lon for woods similar to that of the Podocarpaceae Arnold (1952) reviewed the previous concepts but which differ by having araucaria-type pitting of araucarian affinities proposed for Xenoxylon on the radial walls of the tracheids. The previ- by Holden (1913) and others. He pointed out ously described species of this genus range strati- discrepancies in using some criteria, particularly graphically from the Upper Carboniferous (?) to presence or absence of crassulae, as a fundamen- the Tertiary. All species are characterized by the tal difference between araucarian and the "more presence of araucaria-type crossfield pitting. Sep- advanced" conifers. As stated by Arnold (1952), tate tracheids are present in some species. Spe- "Considerable confusion and misunderstanding cies of Protophyllocladoxylon show many striking about the affinities of fossil conifers has resulted similarities to Xenoxylon morrisonense, especially from an 'either-or' attitude on the part of in- those having septate tracheids. However, the vestigators who have endeavored to force mis- araucarian pitting on the radial walls of the tra- fits into modern families where they do not be- cheids of Protophyllocladoxylon excludes our long." Perhaps by using a combination of ancestral specimen. and living characters with special emphasis on the Lemoigne (1966) and Demarcq and Lemoigne "more advanced" features, a semiorderly system ( 1967) placed two new species in Dadoxylon, of classification of these fossil conifers may yet be but Lemoigne (1968) later removed them by as- established. signing them to a new genus, Embergerixylon, A combination of large podocarpoid pits in the which features septate tracheids with uniseriate crossfields, smooth horizontal and tangential walls and, more rarely, biseriate (araucarian) tracheary on the ray cells, and the absence of resin canals pitting on the radial walls. The crossfield pitting suggests a possible phyletic affinity of Xenoxylon is also of the araucarian type, although poorly pre- with the modern family Podocarpaceae. Some served, which is probably why any possible af- Xenoxylon species are said to be indistinguish- finity of this genus with the Podocarpaceae was able from Sciadopitys and Podocarpus (Arnold, not mentioned. Xenoxylon morrisonense and Em- 1952). The occurrence of pitted horizontal and bergerixylon alpinum are very similar but differ tangential walls of the rays of X. morrisonense in their crossfield pitting. also suggests a possible ancestral tie to some All of the above genera tend to merge into one members of the Pinaceae. another, part of the problem of affinities being the There are three established fossil genera, Mes- great range of structural variability in both living embrioxylon, Protophyllocladoxylon, and Xen- oxylon, for petrified woods which show possible and extinct conifers. The rest of the enigma lies affinities to the Podocarpaceae. In addition, in the lack of precise generic delineation. Embergerixylon is similar but has not yet been The foliage of Xenoxylon is unknown although allied with woods related to this family. Nathorst (1897) suggested a possible relationship Mesembrioxylon is an artificial genus estab- between this genus and Elatides. Arnold (1952) lished by Seward (1919) to include those extinct noted the association of his specimen with Podo- 208 AMERICAN JOURNAL OF BOTANY [Vol. 62 zamites and Baiera. Watari (1960) mentioned du wealdien de Feron-Glageon (Nord). Bull. Soc. that Podozamites occurs in the same strata as his Geo!. France 9: 53-56. specimens of Xenoxylon latiporosum. No fossil FLICHE, P. 1910. Flore fossile du Trias en Lorraine et Franche-Comte avec des considerations finales foliage has yet been collected in the area where part M. R. Zeiller. Paris. Xenoxylon morrisonense was found. However, FLORIN, R. 1958. On Jurassic taxads and conifers Brown (1972) reported Podozamites with the from northwestern Europe and eastern Greenland. conifers Pagiophyllum and Pityophyllum from the Acta Horti Bergiani 17: 145-147. Morrison Formation in Montana. If an organic GOTHAN, W. 1905. Zur Anatomie lebender und fos- connection could be proven between the supposed siler Gymnosperm-Holzer. Abh. K. Preuss. Geo!. araucarian Podozamites and Xenoxylon, which Landes. (N.F.) 2: 1-108. appears to be unlikely, the evidence would be 1906. Fossile Holzer aus dem Bathonien Russ-Polens. Verh. Kais. Russ. Min. Ges. 44: 454. against the placement of Xenoxylon in the Podo- ---, ANDH. C. SZE. 1933. Dber fossil Holzer aus carpaceae. China. Mem. Nat. Res. Inst. Geo!. Acad. Sinica Xenoxylon has a wide geographical distribution 13: 93. in the Northern Hemisphere. It has been reported GRAMBAST,L. 1953. Sur des bois de conifer proven ant from Spitzbergen, King Charles Land, England, de terrains Jurassiques de France. Bull. Ge6!. Poland, France, Germany, Korea, Manchuria, France. 3: 761-766. western Canada, and northern Alaska (Arnold, HOLDEN, R. 1913. Contributions to the anatomy of 1952). The occurrence of Xenoxylon morrison- Mesozoic Conifers. Part I. Jurassic coniferous wood from Yorkshire. Ann. Bot. 27: 533-545. ense in Utah is the southernmost extension of the JANE, F. W. 1956. The structure of wood. Macmillan genus in North America. Co., New York. Xenoxylon is not known from the Southern JEFFERY, E. 1917. The anatomy of woody plants. Hemisphere. In contrast, the Podocarpaceae is Univ. Chicago Press. the most important family of Coniferales in the 1925. The origin of parenchyma in geolog- Southern Hemisphere today. Species of this fam- ical time. Prec. Nat. Acad. Sci. 2: 106-110. ily grown mainly in mountain tropical forests, al- KRAUSEL, R. 1939. Ergebnisse der Forschungsreisen though some occur in lowland forests (Florin, Prof. E. Stromers in den Wusten Aegyptens (iv). 1958). Die fossilen Floren Aegyptens. Abh. dey. Bayek. Akad. Wiss. Math. Naturwiss. 47: 1-40. Xenoxylon and other allied genera seem to be LEMOTGNE,Y. 1966. Sur une nouvelle espece de coni- widespread in the Mesozoic. Of the described ferale Jurassique provenant des Terres Noires du species of Xenoxylon, Protophyllocladoxylon, Bassin de la Durance (Dadoxylon alpinum nov. Mesembrioxylon, and Embergerixylon, approxi- sp.). Bull. Soc. Geo!. France 8: 393-397. mately 75 % are found in the Mesozoic, thus 1968. Un nouveau genre de structure Jig- showing that these possible representatives of the neuse de type gymnospermien: Embergerixylon nov. Podocarpaceae were an important aspect of the g. Ann. Soc. Geo!. Nord. 88: 155-157. NATHORST, A. 1897. Zur Mesozoischen flora Spitz- Mesozoic flora. bergens. K. Svensk. Vetenskapsakad. Hand. 30: 42. OGURA, V. 1931. Fossil plants, 'in Kenbikyo-ka no LITERATURE CITED Kyoi,' p. 50. 1944. Notes on fossil woods from Japan and ARNOLD, C. A. 1952. Silicified plant remains from Manchoukuo. Jap. J. Bot. 13: 346-365. the Mesozoic and Tertiary of western North Amer- 1960. Tyloses in tracheids in Araucarioxylon. ica. II. Some fossil woods from northern Alaska. J. Fac. Sci. Univ. Tokyo, III 7: 501-509. Pap. Mich. Acad. Sci. Arts. Lett. 38: 9-19. PENHALLOW,D. P. 1907. A manual of North Amer- BATTON,G., ANDE. BOUREAU. 1965. Etude des flo res ican Gymnosperms. Boston. fossiles du Nord du Cameroun: Protophylloclado- RECORD, S. 1918. Significance of resinous tracheids. xylon diphtericum n. sp., bois fossil du Cretace Bot. Gaz. 66: 61. moyen du Lagon. Centre Recherches des Zones SEWARD,A. C. 1919. Fossil Plants. Vo!. IV. Cam- Arides. CNRS Geo!. 6: 97-114. bridge. BROWN,J. T. 1972. The flora of tbe Morrison Forma- SHIMAKURA,M. 1936. Studies on fossil woods from tion (Upper Jurassic) of central Montana. Un- Japan and adjacent lands. I. Some Jurassic woods pub!. diss., Univ. Montana. from Japan and Manchoukuo. Sci. Rep. Tohoku. CHANG, C. Y. 1929. A new Xenoxylon from North Imp. Univ. II. Ser. 18: 267-298. China. Bull. Geo!. Soc. China 7: 243-251. STaPES, M. 1915. Catalogue of Mesozoic plants in CONRAD, E. 1910. Beitrage zur Morphologie und the British Museum (Nat. Hist.). London. Anatomie von Agathis (Dammara) Brownii. Diss. THOMSON, R. B. 1913. On the comparative anatomy Kie!. and affinities of the Araucarineae. Phi!. Trans. R. CRAMER,C. 1868. Fossile Holzer der Arctischen Zone. Soc. London B. 204: 1-46. In O. Heer, Foss. Flor. Arct. Vo!. I. Zurich. WATARI, S. 1960. On some structures and affinity of DEMARCQ, G., AND Y. LEMOIGNE. 1967. Nouvelle Xenoxylon latiporosum. J. Fac. Sci. Univ. Tokyo, espece de Dadoxylon a tracheides septees proven ant III 7: 511-521.