Cyclotella petenensis and Cyclotella cassandrae, two new fossil diatoms from Pleistocene sediments of Lake Petén-Itzá, Guatemala, Central America Author Paillès, Christine Aix-Marseille Université, CNRS, IRD, Collège de France, INRA - CEREGE UM 34, 13545 Aix en Provence, France pailles@cerege.fr Author Sylvestre, Florence Aix-Marseille Université, CNRS, IRD, Collège de France, INRA - CEREGE UM 34, 13545 Aix en Provence, France Author Escobar, Jaime Universidad del Norte, Km 5 Via Puerto Colombia, Atlantico, Colombia Author Tonetto, Alain Aix-Marseille Université, Fédération de Chimie, PRATIM, 3 Place Victor Hugo, 13331 Marseille Cedex 3, France Author Rustig, Sybille Institute of Chemistry, Universität Potsdam, Karl-Liebknecht-Str. 24 - 25, D- 14476 Potsdam, Germany Author Mazur, Jean-Charles Aix-Marseille Université, CNRS, IRD, Collège de France, INRA - CEREGE UM 34, 13545 Aix en Provence, France text Phytotaxa 2018 2018-06-07 351 4 247 263 http://dx.doi.org/10.11646/phytotaxa.351.4.1 journal article 10.11646/phytotaxa.351.4.1 1179-3163 13707314 Cyclotella petenensis Sylvestre, Paillès & Escobar sp. nov . ( Figs. 1–9 ) Type : Lake Petén-Itzá, Department of Petén , Guatemala , Latitude 16° 15’ 50 N , Longitude 89° 15’ 00 W . Lacustrine sediment in Core PI- 6, sample GLAD 9- PET 06-6A-13H2-98,3-99,3 cm ( 39.35 m below lake floor). Core collected in February 2006 . Holotype : slide PC0612192 and sediment PC0612194 deposited at the Laboratoire de Cryptogamie , Museum National Histoire Naturelle ( MNHN ) Paris , France . Isotype : slides Zu/1094 and sediment R 1278 deposited at the Friedrich Hustedt Diatom Study centre in Bremenhaven, Germany . Description Cells circular, drum-shaped, with a diameter between 15 and 60 μm. Central area tangentially undulate, representing one third to half of the valve surface. Central area occupied on the elevated part by two (for smaller specimens) to>20 valve face fultoportae in a semicircular arrangement, the depressed part appears unstructured or colliculate. The total number of central fultoportulae is strongly positively related with cell diameter. Marginal area circumferentially undulate with coarse striae of equal length, 5 to 9 within 10 μm. Marginal striation crossed circumferentially by a «ring» about two third of the valve surface, representing the transition between internal openings of alveoli and central lamina. Stria composed of a main row of large pori starting near the central part and continuing with a double row of smaller ones arranged in a quicunx (staggered). Central fultoportulae formed by a short tubulus surrounded by three satellite pores. Marginal fultoportulae (one tube + three satellite pores) on each costa. Rimoportula on a costa within the ring of mantle fultoportulae.