Marc Philippe

Jurassic–Early Cretaceous Gondwanan homoxylous woods: a nomenclatural revision of the genera with taxonomic notes

The homoxylous fossil woods occurring in the Gondwanan continents of South America, Australia, Africa, India and Antarctica during the Jurassic and Early Cretaceous period are considered here. Original descriptions of the genera and wherever possible, the type material, have been consulted. Applying the rules of the International Code of Botanical Nomenclature, the generic names of the homoxylous woods have been revised from a nomenclatural point of view. According to this review, out of 31 generic names used for woods from the given time interval and area, 6 are illegitimate later nomenclatural synonyms, 1 is a later homonym, and 5 can be considered as taxonomical synonyms. Moreover, 9 genera have been used erroneously. We propose one new generic name (Protaxodioxylon n. gen.) and elsewhere we will propose for conservation, with a conserved type one of the illegitimate names and one of the taxonomic synonyms. As a result, we consider that there are only eighteen generic names correctly quoted for the Jurassic-Early Cretaceous of Gondwana, and we provide a taxonomic key for the corresponding genera. This revision is the first step in systematically comparing northern and southern hemisphere woods.

Découverte d’un dépôt paralique à bois fossiles, ambre insectifère et restes d’Iguanodontidae (Dinosauria, Ornithopoda) dans le Cénomanien inférieur de Fouras (Charente-Maritime, Sud-Ouest de la France)

Resume Un gisement paralique inedit, d’âge Cenomanien inferieur, avec du bois fossile, de l’ambre insectifere et des restes de vertebres, a ete decouvert sur l’estran de la presqu’ile de Fouras (Charente-Maritime, France), a la suite d’une tempete qui a temporairement ote du littoral les nappages de cordons sableux et de vasieres. L’assemblage de bois fossiles contient trois taxons de coniferes ( Agathoxylon , Podocarpoxylon , Brachyoxylon ) et un Ginkgoxylon . Les insectes de l’ambre correspondent a des Dipteres, des Hymenopteres et des Homopteres. Les restes de vertebres sont principalement representes par des carapaces de tortues terrestres (Solemydidae), des vertebres de serpents ( Simoliophis ) et des ossements de dinosaures, appartenant probablement au genre Iguanodon . Pour citer cet article : D. Neraudeau et al., C. R. Palevol 2 (2003).

Distribution and palaeoecology of the Mesozoic wood genus Xenoxylon: palaeoclimatological implications for the Jurassic of Western Europe

Xenoxylon is a morphogenus used for a Mesozoic type of wood. Its distribution is circumpolar, limited to the Northern Hemisphere and belt-like. The lower the palaeotemperature, as estimated from geological inferences, the lower is its mean palaeolatitude. The wood is frequently associated with floristic or sedimentological indications of a cool and/or wet climate. Both synecology and autoecology suggest that Xenoxylon favoured cool/wet climates. The sedimentological analysis of its occurrence sheds new light on the relationship between palaeoclimatology and sedimentation.

Nomenclature générique des trachéidoxyles fossiles mésozoïques à champs araucarioïdes

Many studies on fossil woods did not respect the International code of botanical nomenclature. As a result their nomenclature is complex and fluctuating. During preparation of a thesis on Jurassic fossil woods from Franche-Comtd (northeastern France), problems have arisen with the nomenclature of gymnospermous woods with araucarioid cross-field pitting. This work is a nomenclatural review of the twenty-one generic names that have been used to designate mesozoic tracheidoxyls with araucarioid cross-fields. Only eight are legitimate and can be justifiably used. As a taxonomic summary, a generic key is proposed.

Biomolecules preserved in ca. 168 million year old fossil conifer wood

Biomarkers are widely known to occur in the fossil record, but the unaltered biomolecules are rarely reported from sediments older than Paleogene. Polar terpenoids, the natural products most resistant to degradation processes, were reported mainly from the Tertiary conifers, and the oldest known are Cretaceous in age. In this paper, we report the occurrence of relatively high concentrations of ferruginol derivatives and other polar diterpenoids, as well as their diagenetic products, in a conifer wood Protopodocarpoxylon from the Middle Jurassic of Poland. Thus, the natural product terpenoids reported in this paper are definitely the oldest polar biomolecules detected in geological samples. The extracted phenolic abietanes like ferruginol and its derivatives (6,7-dehydroferruginol, sugiol, 11,14-dioxopisiferic acid) are produced only by distinct conifer families (Cupressaceae s. l., Podocarpaceae and Araucariaceae), to which Protopodocarpoxylon could belong based on anatomical characteristics. Therefore, the natural product terpenoids are of great advantage in systematics of fossil plant remains older than Paleogene and lacking suitable anatomical preservation.

Are Mesozoic wood growth rings climate-induced?

Abstract Growth rings of Mesozoic fossil woods have often been used for paleoclimatological inferences. Most of the studies, however, rest upon uniformitarian deductions based on the observation of conifers from the present boreal temperate realm, whereas warm climates dominated during the Mesozoic. We propose a new approach, based on the study of the distribution of growth ring types among 643 samples from the Jurassic–Cretaceous interval. A clear picture emerges from analysis, consistent with what is known of Mesozoic climates from other sources. Woods with no rings are encountered in a wide latitudinal zone, extending up to 75°N and 65°S during the Late Cretaceous. Woods with well-developed latewood do not occur at low latitude and disappeared from the Northern Hemisphere during the Late Cretaceous. Our data set also shows that the taxonomic distribution of growth ring types is not regular. Among the genera encountered, 40% can build only one type of ring. The genus Agathoxylon never displays thick latewood, although it ranges from 75°S to 70°N. This demonstrates that growth ring studies must include a taxonomic analysis.

Which name(s) should be used for Araucaria-like fossil wood?- Results of a poll

Araucarioxylon Kraus is a widely known fossil-genus generally applied to woods similar to that of the extant Arau- cariaceae. However, since 1905, several researchers have pointed out that this name is an illegitimate junior nomenclatural synonym. At least four generic names are in current use for fossil wood of this type: Agathoxylon Hartig, Araucarioxylon, Dadoxylon Endl. and Dammaroxylon J.Schultze-Motel. This problem of inconsistent nomenclatural application is compounded by the fact that woods of this type represent a wide range of plants including basal pteridosperms, cordaitaleans, glossopterids, primitive conifers, and araucarian conifers, with a fossil record that extends from the Devonian to Holocene. Conservation of Araucarioxylon has been repeatedly suggested but never officially proposed. Since general use is a strong argument for con- servation, a poll was conducted amongst fossil wood anatomists in order to canvass current and preferred usage. It was found that the community is divided, with about one-fifth recommending retention of the well-known Araucarioxylon, whereas the majority of others advocated use of the legitimate Agathoxylon. The arguments of the various colleagues who answered the poll are synthesized and discussed. There is clearly little support for conservation of Araucarioxylon. A secondary aspect of the poll tackled the issue as to whether Araucaria-like fossil woods should be either gathered into a unique fossil-genus, or whether two fossil-genera should be recognized, based on the respective presence or absence of axial parenchyma. A majority of colleagues favoured having one fossil-genus only. Agathoxylon can be used legitimately and appears to be the most appropriate name for such woods. However, its original diagnosis must be expanded if those woods lacking axial parenchyma are to be included.

A new hybodont shark assemblage from the Lower Cretaceous of Thailand

Isolated teeth of five hybodont taxa (Hybodus sp., Parvodus sp., Lonchidion khoratensis nov. sp., Isanodus paladeji nov. gen., nov. sp., Heteroptychodus steinmanni) are described from the freshwater Sao Khua Formation of Thailand (Lower Cretaceous). This Early Cretaceous fauna appears less endemic, with some European affinities, than the hybodont fauna found in Thailand in the more recent Aptian/Albian Khok Kruat Formation. Teeth of Isanodus paladeji (Lonchidiidae) and Heteroptychodus steinmanni (Ptychodontidae) share an unusual ornamentation pattern suggesting that the origin of the family Ptychodontidae is nested among Asian Lonchidiidae.

Cretaceous plant fossils of Pitt Island, the Chatham group, New Zealand

Pitt Island, a part of the Chathams Islands group, lies 700 km east of New Zealand. Its geology includes the Tupuangi Formation, dated as Motuan to Teratan (late Albian to Santonian) on the basis of palynology. Samples of Tupuangi Formation mudstone yielded leaf cuticle assemblages dominated by araucarian and podocarp conifers and locally by angiosperms. The 12 distinguishable conifer taxa include a new species of Araucaria, A. rangiauriaensis, and the extinct genera Eromangia, Kakahuia (both Podocarpaceae), Otwayia (Cheirolepidiaceae), Paahake (Taxodiaceae or Taxaceae) and possibly Katikia (Podocarpaceae). Ginkgo and two types of dicotyledonous angiosperm cuticle are present. Based on the absence of bennettitaleans and rarity of Ginkgo, a Turonian or slightly younger age is inferred, making the Pitt Island assemblage the first Turonian plant macrofossils documented from New Zealand. The fossils provide a window into southern high-latitude (polar) vegetation of the mid-Cretaceous. Conifer charcoal (probably of Podocarpaceae) is locally abundant and suggests that fire was an important part of the ecosystem. A broad analogy with modern boreal conifer-deciduous angiosperm forests is suggested although clearly with warmer temperatures.

Systematic relationships of the Mesozoic wood genus Xenoxylon: an integrative biomolecular and palaeobotanical approach.

Xenoxylon GOTHAN is one of the very few components of Mesozoic terrestrial biota which give clear palaeoecological signal. Unfortunately its systematic relationships are still unknown. This work analyzes the organic geochemistry of particularly well preserved samples of Xenoxylon from the Callovian of ⁄ Lukow (eastern Poland) for comparison with the Bathonian of Gnaszyn (southcentral Poland). The wood fragments from both ⁄ Lukow and Gnaszyn contain phenolic abietanes like ferruginol, 6,7-dehydroferruginol, sugiol, hinokiol or 2-ketototarol. The presence of such biomolecules, with simultaneous absence or very small amount of tetracyclic diterpanes such as phyllocladanes, beyerane and/or kauranes, is characteristic for extant conifer families Cupressaceae s. l. and Podocarpaceae. Thus, the molecular composition of the wood genus Xenoxylon suggests systematic relationships with these extant families. This study presents the evidence that preserved biomarkers and biomolecules are not exceptional in fossil wood, and that their composition generally supports the anatomical data.