Biodiversity of ecosystems in an arid setting: The late Albian plant communities and associated biota from eastern Iberia

Principal Component Analysis (PCA) was performed to evaluate environmental gradients underlying the palynological dataset and to identify groups of taxa representing different types of vegetation. Only the most abundant or ecologically relevant taxa were analysed. PCA calcu- lations were performed using the SPSS and software (version 4.0.2) with FactoMineE and Rioja packages for PCA and Cluster Analysis, respectively [100, 101]. Mega and mesoflora Megaflora was initially investigated and documented by using an Olympus SZX 12 stereomi- croscope with DP 70 digital camera. Material with preserved morphological details was studied via Scanning Electron Microscopy (SEM). Specimens were mounted on cleaned aluminium stubs using nail polish, coated with gold and examined with a Hitachi S-3700N Environmental Scanning Electron Microscope at 2 kV, at the National Museum of Prague (Czechia), where the studied material is stored temporarily. Specimens from SJ and AP will be transferred in the future to the Museo Aragone´s de Paleontologı´a (Fundacio´n Conjunto Paleontolo´gico de Teruel-Dino´polis, Spain) as the definitive repository. Amber bioinclusions In the Maestrazgo Basin, amber pieces with bioinclusions have been collected for research pur- poses since 1998. They have been prepared using epoxy resin [102], to improve the visualisa- tion of the bioinclusions and their long-term preservation. The amber pieces from the San Just and Arroyo de la Pascueta outcrops are housed at the Museo Aragone´s de Paleontologı´a (Fun-

dacio´n Conjunto Paleontolo´gico de Teruel-Dino´polis, Teruel), and the ones from the La Hoya outcrop at the Museu de la Universitat de València d’Història Natural (Valencia). Bioinclu- sions have been photographed using a digital camera sCMEX-20 attached to a compound microscope Olympus CX41 with the software ImageFocusAlpha version 1.3.7.12967.20180920 (www.euromex.com) and processed with Photoshop CS6 version 13.0 (www.adobe.com). The list of identified taxa is included in Table 2 and S2 Appendix. Results Palaeobotanical aspects A total of 26 out of 92 samples processed for their palynological content were barren (1 in San Just section, 14 in Cortes de Arenoso section and 11 in the Arroyo de la Pascueta section). Pro- ductive samples showed an overall good recovery and well-preserved palynological content. Except on a few occasions, interpreted as reworking, miospores and dinocysts present a yellow to pale brown colour suggesting low thermal maturation [103]. A total of 367 palynomorph types (S2 Appendix) have been identified, mainly consisting of dinoflagellate cysts (dinocysts, 30 taxa; Fig 7C–7H), bryophyte, lycophyte and pteridophyte spores (186 taxa; Fig 8), gymno- sperms (53 taxa; Fig 7I–7T) and angiosperms (88 taxa; Fig 9). A small number of acantho- morph acritarchs, phycomes of prasinophytes, freshwater algae (Fig 7A and 7B) and linings of foraminifers have also been recorded (S1 Appendix). Unlike the upper Albian–lower Cenomanian successions of the Basque-Cantabrian and

Lusitanian basins [104, 105], dinocysts were only scarcely recorded in the studied assemblages. The most frequently occurring taxa are Cyclonephelium spp., Criboperidinium spp. (Fig 7C), Implestosphaeridium spp., Kiokansium unituberculatum (Fig 7H) and Oligosphaeridium com- plex (Fig 7G). The remaining of the identified marine and freshwater palynomorphs are not numerically significant (S1 Appendix). Terrestrial assemblages are characterised by abundant conifers with Classopollis (mainly Classopollis major) and Inaperturopollenites dubius (Fig 7K PLOS ONE Late Albian desert biota from Iberia PLOS ONE | https://doi.org/10.1371/journal.pone.0282178 March 2, 2023 21 / 51