Romain Thomas

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  Article: Palm stem anatomy and computer-aided identification: The Coryphoideae (Arecaceae).

  Romain Thomas, Dario De Franceschi
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  ABSTRACT: • Premise of the study: Through a comparative study of the anatomy of palm stems and the development of an interactive web-based tool, the present paper aims to provide a method of identifying palm stems. The stem determination will allow specialists in archaeology and paleontology to better exploit palm fossils for paleoenvironmental interpretations. The precise anatomical description also provides new systematic data tested in phylogenetic analyses (new anatomical characters, stratigraphic calibrations).• Methods: Stem samples were collected, including representatives from each tribe of the five palm subfamilies, and 25 descriptors (with 78 states) were defined within 37 taxa and registered in Xper(2), a management tool for taxonomic description that allows editing of standardized descriptions. Some descriptors were used for the first time in this work; others were compiled from the existing literature. While all the palm subfamilies were included in the present study, the focus here is on the Coryphoideae.• Key results: Descriptors were mainly based on the general organization of the transverse section and the structure of the fibrovascular bundles as well as ground parenchyma. Coryphoideae have 1, 2, or more metaxylem elements, whereas the other subfamilies systematically present only 1 or 1 and 2 metaxylem elements. The centrifugal differentiation of the sheath of phloem fibers is described in other subfamilies but is not found in the Coryphoideae (except in Caryoteae).• Conclusion: Some tribes are easy to identify (Borasseae, Cryosophileae, Phoeniceae, Caryoteae); others are rather heterogeneous and more difficult to define (Chuniophoeniceae, Trachycarpeae). Caryoteae presents some unique states of the Arecoideae.
  American Journal of Botany 01/2013; · 2.66 Impact Factor
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  Article: First evidences of fossil Cryosophileae (Arecaceae) outside the Americas (early Oligocene and late Miocene of France): anatomy, palaeobiogeography and evolutionary implications

  Romain Thomas, Dario De Franceschi
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  ABSTRACT: A recent anatomical study of living palm stems shows that the five palm subfamilies and their tribes have useful identification characters. This study intends to show that identification of fossil palm stems from anatomical descriptors is potentially possible at the tribe level. As a concrete application, we study the holotype of Palmoxylon vestitum (Saporta) Stenzel and some other stems of two localities: five fossil palm stems from the lower Oligocene of Apt (Vaucluse, France) and two from the upper Miocene of Castellane (Alpes-de-Haute-Provence, France). These seven palm stems belong to the same species (P. vestitum). With a referential of living stems, we improve the identification of this species within the palm family. This species is a Cryosophileae (Coryphoideae) and the closer living genus is Coccothrinax Sargent This discovery has important consequences on the history of the palm family. Indeed, it is the first record of this tribe outside the Americas. Currently the living Cryosophileae are mainly restricted to Central America and this identification provides evidence for a Laurasian origin of this tribe, during the early Eocene as for its sister tribe (Sabaleae). Furthermore, the ecology of this tribe and of this genus gives more information about the palaeoclimatical conditions of these two localities (dry area to subtropical dry forest).
  Review of Palaeobotany and Palynology 01/2012; 171:27-39. · 1.64 Impact Factor
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  Article: Analysis of a Protohistoric net from Shahi Tump, Baluchistan (Pakistan)

  Romain Thomas, M. Tengberg, Christophe Moulhérat, Vincent Marcon, Roland Besenval
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  ABSTRACT: The fire that partly destroyed a 4th millennium BCE building at Shahi Tump in the Kech Valley of south-western Pakistan is responsible for the exceptional preservation by carbonisation of a net found on the burnt floor as a heap of entangled cords and knots. Macro- and microscopic observation has allowed a reconstruction of the techniques used to manufacture the net from a two-strand plied cord. The comparison of the phytoliths extracted from the archaeological net to those from a modern reference collection suggests the use of fibres that originate from the leaves of a local palm species: the desert palm or Nannorrhops ritchieana (Griff.) Aitch. Besides the technical and archaeobotanical aspects of the study, the paper discussed past and present uses of the desert palm in the arid regions of the Middle East as well as the possible utilisation (fishing, carrying etc.) of the protohistoric net.
  Archaeological and Anthropological Sciences. 01/2011;
• Article: Palm-ID, a database to identify the palm stem anatomy with an expert system (Xper2)

  Romain Thomas
  01/2011;
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  Article: Wood anatomy of the Mascarene Dombeyoideae: systematic and ecological implications

  Anaïs Boura, Timothée Le Péchon, Romain Thomas
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  ABSTRACT: The Dombeyoideae (Malvaceae) are one of the most diversified groups of plants in the Mascarene Islands. Species of Dombeya Cav., Ruizia Cav. and Trochetia DC. are distributed in almost all parts of the archipelago and show a wide diversity in their growth forms. This study provides the first wood anatomical descriptions of 17 out of the 22 Mascarene species of Dombeyoideae. Their wood anatomy is similar to that of previously described species: wide vessels, presence of both apotracheal and paratracheal parenchyma, and storied structure. In addition, we also found a second wood anatomical pattern with narrower vessels, high vessel frequency and thick-walled fibres. The two aforementioned wood patterns are considered in a phylogenetic context and used to trace the evolutionary history of several wood anatomical features. For example, the pseudoscalariform pit arrangement supports a sister group relationship between Trochetia granulata Cordem. and T. blackburniana Bojer ex Baker and may be a new synapomorphy of the genus Trochetia. Finally, wood variability is evaluated in relation to geographic, climatic and biological data. Despite the juvenile nature of some of the specimens studied, we discuss how the habit, but also factors related to humidity, influence the variability observed in the Mascarene Dombeyoideae wood structure.
  IAWA journal / International Association of Wood Anatomists 01/2011; 32(4):493-518. · 1.04 Impact Factor