Journ. Hattori Bot. Lab. No. 71: 377-388 (Jan. 1992) BRYOKHUTULIINIA JURASSICA, GEN. ET SPEC. NOVA, A REMARKABLE FOSSIL MOSS FROM MONGOLIA 1 MICHAELS. IGNATOV ABSTRACT The new genus Bryokhutuliinia is described. It includes Jurassic species B. jurassica lgnatov spec. nova from Mongolia and Cretaceous B. ingodensis (Srebrodolskaya) lgnatov comb. nova (Muscites ingodensis Srebrodolskaya) from Transbaikalia Region. The combination of the lack of costa, limbate leaf, elongated cells and distichous leaves is unique in mosses and does not allow to relate this new genus to any of extant groups. Both species of Bryokhutuliinia are known only as imprints of sterile leafy shoots. INTRODUCTION In discussing Mesozoic leafy hepatics Schuster and Janssens ( 1989) state that so far these fossils do not enable one to elucidate the patterns of evolution: they pose only questions, they provide no meaningful answers. This evaluation is almost true also for fossil mosses. However in spite of not having evolved into recognizeable, defineable modern groups, these fossils undoubtedly provide an interesting and almost logical picture of past diversity of bryophytes and its changes toward the present. Starting with the Tertiary practically all described fossil bryophytes, both mosses and hepatics, share the features of contemporary genera (Miller 1984, Jovet-Ast 1967, Oostendorp 1987). Moreover, many of them can be attributed even to extant species. The exceptions generally depend on the presentation of fossil material: formal genera are used for remains where microstructure is either invisible, or admits too wide an interpretations. Not one of these formal genera from the Tertiary exhibits any feature or combination of features which exceeds the range of variation in extant genera. The situation with Paleozoic mosses is different: there are a sufficient number of characters which are absolutely unknown in extant groups, i.e. net nervation in Polyssaievia Neuburg or affixial leaf attachment involving the costa only and petiolated leaves in Protosphagnum Neuburg and related genera, or laminar cell dimorphism of a quite peculiar type in Protosphagnum , Vorcutannularia Neuburg, Junjagia Neuburg, Palaeosphagnum lgnatov (Neuburg 1960, Ignatov 1990). At the same time there are a number of Permian mosses with characters like those of extant taxa, but the combi­ nation of characters mostly does not enable one to attribute them to extant genera, though one can to draw certain parallels with now-existing families. Hepaticae of the Paleozoic resemble extant groups to a greater extent than mosses of the same age: their peculiarities are restricted only to a different combination of character. Maybe this fact can be explained by the tallose nature of most of these fossils, which are more difficult to classify. Leafy hepatics were described from the 1 Main Botanical Garden of the Academy of Science of USSR, 127276 Moscow, Botanicheskaya 4, USSR. 378 Journ. Hattori Bot. Lab. No. 71 I 9 9 2 Early Permian by Poulsen ( 1974) : Jungermannites sealandicus Poulsen was referred to Jungermanniales, while Gessella striata Poulsen and G. communis Poulsen, to Calob­ ryales (for G. communis sporogones were available). Gametophytically, however, Gessella is more similar to mosses because of the lanceolate, rather long leaves without differentiation into lateral leaves and underleaves. Among Mesozoic remains of bryophytes only the order Marchantiales is wide­ spread - it is represented by 14 species, 4 genera (Oostendorp 1987). All other groups of bryophytes are worse known, even than in Paleozoic. The most important, for the present discussion, are mosses and hepatics of the order Jungermanniales, which are known by a few taxa. Among mosses l Jurassic collection was attributed directly to the extant genus Sphagnum (Reissinger 1950), and Krassilov and Schuster ( 1984) mention also a still undescribed epiphytic moss resembling extant Dicranum found in the Cretaceous. Two mosses were described in separate genera - Tricostium Krassilov from the Jurassic and Yorekiella Krassilov from the Cretaceous; both are monotypic (Krassilov 1973). Some other taxa were retained in Muscites Brogn. or were described just as mosses. Of these: - Tricostium has a rather peculiar combination of characters and it is not easy to place it in any of modern families (though Pottiaceae definitely is the first candidate); - Yorekiella is a weakly understood plant; - Muscites guescelinii Townrow from Triassic of South Africa was linked to Leucodontaceae (Townrow 1959); - Muscites fontinalioides Krassilov from the Late Jurassic has no characters which would prohibit its placement just in Fontinalis Hedw.; - Muscites ura/ensis Turutanova-Ketova, nom. illeg., from Triassic is too imperfectly known; - Muscites ostracodiferus Krassilov from the Cretaceous (Krassilov 1982) does not show enough peculiarities for its systematic interpretation; - Muscites samchakianus Srebrodolskaya superficially resembles Hypnales, but the cell structure is unknown; the age was indicated by Srebrodolskaya ( 1980) as Cretaceous, but Rasnitsyn (1985) re-estimated it as Jurassic. - Muscites ingodensis Srebrodolskaya (Cretaceous), despite absence of cell peculiarities, has enough characters for separate generic placement and will be discussed in details below; - mosses from Cretaceous of Australia (Drinnan & Chambers 1986) are represented by two gametophytes of uncertain position and two sporophytes, one of which is strongly reminiscent of the Orthotrichaceae. Among Mesozoic Jungermanniales microstructure either ( 1) is not described (Triassic Jungermannites keuperianus De Gasparis, Jurassic J. gracilis (Halle) Ooste­ ndorp, Cretaceous J. cretaceous Berry, J. noterocladioides Scott, J. vetusior Saporta); (2) or inapparent (Jurassic Laticaulina papillosa Krassilov); (3) or typical jungerm­ annioid, polygonal-rounded (Jurassic Cheirorhiza brittae Krassilov); ( 4) or at least quite different from those of modern Jungermanniales - Cretaceous Diettertia monta­ nensis Brown & Robinson has elongated laminar cells, so originally it was placed in the mosses. Additional material showing more perfect preservation allowed Schuster and Janssens (1989) to clarify it systematic position and place it in Jungermanniales, but in M. S. IGNATOV: Bryokhutuliinia, a remarkable fossil moss from Mongolia 379 a separate suborder, Diettertiinae Schust. & Janssens. Thus far from the Mesozoic 1 moss from Mongolia and 2 mosses from nearby Transbaikalia were known. In 1986 in the course of collecting fossils (mostly insects) Alexander G. Ponom­ arenko collected a number of pieces of rocks with moss imprints, which he made available for study by the present author. GEOLOGY, AGE AND PALEOENVIRONMENTS The moss fossils were found in volcanic-elastic sediments of the Ulugey formation (lower part), where coarse beds are included in lava and lava-breckchia deposits. K/Ar data from this volcanic material indicate the interval where the moss was found as 153- 138 millions YBP (Kovalenko et al., 1984). There is some evidence that the moss was buried in bottom sediments of a small temporary lake, at medium depth. The lake was surrounded by volcanos and the water may have been sometimes strongly warmed. Soon after the time when moss was abundant, the lake was completely buried by ash. The moss is associated with Brachyphyllum sp., (Cheirolepidiaceae, Gymnospermae), Equisetites sp., Baissia hirsuta Krassilov (Bennettitales). Despite the presence of some advanced taxa of insects the age of this deposit is accepted by Ponomarenko (personal communication) as the latest Late Jurassic, rather than Cretaceous (Rasnitsyn 1985). MATERIAL AND METHODS The moss was represented by ea. 100 leafy shoots, about 10 of which are rather large, and many leaf fragments. The property of the rock is such as not to allow one to split it clearly enough to avoid numerous overlaying of one shoot by another or by rock. This make it difficult to observe macroscopic characteristics such as branching patterns and even leaves observable from base to apex are very rare (but in total about a hundred leaves more than half complete were seen). The moss is found in fairly grained tufo-argillite as imprints or imprints with scarce remnants of organic material. The latter, however, is coalified and cellular structure is mostly observed guessing from rows of minute grains of coal or by the texture of the imprint. Fortunately, on several leaves there are portions where areolation can be traced more certainly (Figs. 9- 15) - at least average size and shape of laminar cells can be judged reliably. Impressions of the organic matter are very pale, only slightly deeper in color that the rock. Photographs were made by usual camera with "bellows" and polarizating microscope; the film Mikrat-200 was used. TAXONOMY Since the cell structure is particularly important for interpreting the systematic position of mosses its presence in the plant here described permit one to recognize this moss as a separate genus rather than place it in Muscites, which is retained for taxa of poorer preservation. Bryokhutuliinia lgnatov, gen. novum. Diagnosis: leaves distichous, remotely arranged, from the semi-appressed base reftexing up to the horizontal or squarrose; nerve lacking; border distinct all along the lamina; laminar cells elongate-rectangular. Type: Bryokhutuliinia jurassica lgnatov spec. nova. 380 Journ. Hattori Bot. Lab. No. 71 I 9 9 2 F1os. 1- 3. Bryokhutu/iinia jurassica lgnatov, gen. et spec. nova (2 left- hototype; I, 2