The Miocene "Palmoxylon cavallottii (Lovisato & Sterzel, 1900)" and allied species

Giovanni Giuseppe SCANU

Primo

;Gian Luigi PILLOLA;Carla BUOSI

2022-01-01

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Abstract

Cenozoic rocks of Sardinia contain several plant remains. Fossil woods are easily found and numerous outcrops have been reported since the second half of the last century, especially in central and northern Sardinia. Despite this, reports are not always associated with detailed taxonomic and palaeo floristic studies. Coincidently, due to a relocation and a new organization of an exhibition of fossils, a sliced portion of the holotype of the Miocene stem Palmoxylon cavallottii was recovered. This is a part of the same plant specimen studied by Sterzel (1900), which is stored at the Natural Museum of Chemnitz (Germany). According to the Saint Louis Code "if the type specimen of a name of a fossil plant is cut into pieces, all parts originally used in establishing the diagnosis ought to be clearly marked". As a direct consequence of this, the revision of the aforementioned recovered specimen allowed to improve (or emend) the original diagnosis. In our preliminary results, we detected the characteristic arrangement of the fibrovascular bundles according to the "Cocos type" typology: the bundles of the central area become reniform (kidney -like) in shape. We have counted fibrovascular bundles finding an increasing quantity of bundles in the central part of the stem. Close to the cork, vascular bundles appear fewer (lower density) and their shape can be somewhat irregular. Vascular bundles are larger in the middle part and become smaller near the edge. The goal of this study is to understand if the Sardinian part of the holotype can confirm that P. cavallottii is a valid species to be included in the updated Palmoxylon list and, if not, whether it could be put into a synonymy. We also compared this specimen with other allied Sardinian species dating back to the Miocene to understand similarities on the basis of their paleogeography.