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

been reconstructed as a small ligneous plant or shrub growing in coastal salt-influenced envi- ronments [106, 173], F. justae [37] suggests more mesic settings [174, 175]. The association of F. turolensis with Nehvizdya (= Eretmophyllum) penalveri [29] (Fig 11A and 11K), a ginkgoalean previously interpreted as halophytic [83, 176], supports colonisation of salt-influenced settings (Fig 16). This type of ginkgoalean constituted coastal vegetation associated with Cheirolepidiaceae [177]. These communities could thrive in supratidal coastal areas [174, 178]. A similar inference has also been proposed by [28, 29] based on specimens collected in the AP succession. If not taphonomically induced, the low diversity of Frenelopsis- Eretmophyllum could be interpreted as supporting evidence of stressful ecological conditions [179]. Similarly, the complex nature of the fruit of Montsechia-type with Spermatites seeds inside recorded in SJ and CA (Fig 11F) could reflect near-shore deposits as these seeds (Spermatites) have been recorded in physical association with Pseudoasterophyllites cretaceous, a Cenoma- nian angiosperm described in tidally-influenced deposits from Bohemia [98, 180, 181]. While still debated, Montsechia has been considered by some authors as a halophytic plant growing in periodically desiccated coastal marshes [182]. Irrespective of the specific ecological require- ments of Montsechia, the existence of halophytic/xerophytic vegetation formation, including angiosperms is supported by the presence of Tucanopollis. While this pollen has been recorded

in European mid-Cretaceous deposits [183–185], it constitutes an essential element of assem- blages characterising arid settings of central [186, 187] and NE Gondwana [16] and has been observed in stamens of P. cretaceous [98]. The high proportion of Tucanopollis in the lower part of the CA succession (representing the bulk of the ‘other angiosperms’ in level CA-3.2; Fig 13, cluster II; S1 Appendix) is assumed to reflect the proximity of a halophytic/xerophytic plant community also involving Cupressaceae (Inaperturopollenites dubius-producers), Ertma- nithecales and Cheirolepidiaceae (F. turolensis) and probably Monosulcites-producers of uncertain botanical affinities (Fig 17; S1 Appendix). This plant association would characterise coastal, salt-influenced, episodically (but not periodically) flooded areas. The existence of man- groves (i.e., vegetation colonising habitats under periodic marine water influence) is possible, although currently not supported by anatomical evidence. • Wet interdunes and wetlands The presence of freshwater bodies in the study area during the late Albian to early Cenoma- nian has been inferred from sedimentological and palaeobotanical evidence [188, 189]. The existence of habitats with fluctuating humidity or with high moisture is also indicated in San Just by amber inclusions, including the hemipteran Iberofoveopsis miguelesi [44], as well as the presence of edaphic fauna linked to the litter degradation and soils [190–192] (Table 2). The high proportions of fern spores in palynological assemblages devoid of marine palyno-

morphs and characterised by low numbers of gymnosperms (see Fig 12 clusters III and IV; Fig 13 cluster IV; Fig 14 clusters II and VI) also indicate that freshwater was available, at least dur- ing part of the year, as spore producers need free water to complete their biological cycle. A series of fern spikes, mainly consisting of abundant spores with smooth exine attributed to Cyathidites and Deltoidospora, are observed in the three sections. The palynological signal corresponding to these spikes is challeging to interpret. Similar spikes have been recorded after the end-Permian, Triassic, and Cretaceous events [193–195] and interpreted as fern-dominated pioneer vegetation characterising the early stage of recov- ery after the disruption of some terrestrial ecosystems. If the existence of a global adverse palaeoenvironmental event during the late Albian can be discarded on available evidence, the fern spikes observed in the three sections could still be interpreted as riparian early succes- sional developments [196] in the present context. Modern arid ecosystems are fragile and PLOS ONE Late Albian desert biota from Iberia PLOS ONE | https://doi.org/10.1371/journal.pone.0282178 March 2, 2023 37 / 51