A eudicot leaf from the Lower Cretaceous (Aptian, Araripe Basin) Crato Konservat‐Lagerstätte

Abstract

Premise: The Crato Konservat-Lagerstätte in Brazil preserves an exceptionally rich assemblage of plant macrofossils from the Early Cretaceous (late Aptian), including rare early angiosperm fossils related to Nymphaeales, monocots, and magnoliids, and a variety of angiosperms of uncertain affinities. Macrofossils of eudicot angiosperms have not been described previously, despite the presence of tricolpate pollen. We describe a fossil leaf with morphology characteristic of eudicot angiosperms. Methods: The fossil was collected from a quarry in the Lower Cretaceous (late Aptian) Crato Formation of northeastern Brazil in the state of Ceará. We compared the leaf architecture with that of ferns, gymnosperms, and similar living and fossil angiosperms.Results: The leaf of Baderadea pinnatissecta gen. et sp. nov. is simple and petiolate, with leaf architecture similar to that of some herbaceous Ranunculales. The blade is 5 cm long and the margin is untoothed and twice pinnately lobed with narrow lobes (pinnatisect). The primary vein framework is pinnate and there are multiple orders of reticulate venation. Conclusions: The combination of characters preserved in the fossil supports the interpretation that B. pinnatissecta was an herbaceous eudicot similar to some members of Ranunculales and distinguished from other lobate Aptian angiosperms by leaf shape, presence of multiple orders of reticulate venation, and the absence of glandular teeth. The presence of eudicots in the flora of the Crato was already supported by pollen; the discovery of macrofossils like these provides additional information about their morphology and ecological role in low-latitude Early Cretaceous plant communities.

First evidence of ranunculids in Early Cretaceous tropics

“…Another potential eudicot, Baderadea pinnatissecta Pessoa et al, was recently described from the Crato Formation flora 6 . It consists of a single leaf with a pinnatisect dissection similar to that of the leaflets of Santaniella lobata , but the leaf is simple and its lobes are distinctly linear.…”

“…They comprise a grade of early-diverging lineages, i.e., Ranunculales, Proteales, Trochodendrales and Buxales, that are successively sisters to the rest 5 . However, while the resolution of their phylogenetic relationships and systematic affinities have been constantly improved over the past 30 years, their origin and early evolutionary history are still elusive because our knowledge is based mostly on dispersed pollen and mesofossils, whereas the macrofossil record is scarce and mostly fragmented 2 , 6 .…”

“…Northern Gondwanan floras (e.g., Crato Formation flora), which represent the paleoequatorial vegetation during the Early Cretaceous, provide important insights in the evolution and early radiation of angiosperms and their biology. In the Crato Formation from Brazil, one-third of the total angiosperm pollen record is represented by tricolpate grains 25 , but no unquestionable eudicot megafossil was described yet (see discussion 6 ).…”

Is Santaniella a ranunculid? Reassessment of this enigmatic fossil angiosperm from the Lower Cretaceous (Aptian, Crato Konservat‐Lagerstätte, Brazil) provides a new interpretation

“…They argued that the Santaniella material is the oldest unequivocal occurrence of eudicot macrofossils in a low‐latitude setting, supporting the hypothesis of a widespread distribution of this clade during the Cretaceous. They mentioned Baderadea pinnatisecta E. Pessoa & Jud (Pessoa et al, 2021), a eudicot from CKL, but it is very different from Santaniella and they were skeptical about its eudicot affinity because that interpretation is based on leaf architecture. They focused their comparison on Chinese taxa from the Cretaceous with ranunculid affinities.…”

First fossil-leaf floras from Brunei Darussalam show dipterocarp dominance in Borneo by the Pliocene

“…However, the literature regarding out-of-Gondwana origins for dipterocarps seems to omit that Early Cretaceous deposits have been sampled across Gondwana for decades, and no fossil dipterocarps or likely relatives have been reported from hundreds of publications (among many others, Archangelsky, 1963 ; Banerji, 2000 ; Mohr & Friis, 2000 ; McLoughlin, Pott & Elliott, 2010 ; Nagalingum & Cantrill, 2015 ; Monje-Dussán et al, 2016 ). Importantly, angiosperms in Gondwanan Early Cretaceous floras are rare, show early stages in the evolution of leaf organization and other characters, and are not allied with derived eudicot families ( Mohr & Friis, 2000 ; Cúneo & Gandolfo, 2005 ; Nagalingum & Cantrill, 2015 ; Coiro et al, 2020 ; Pessoa, Ribeiro & Jud, 2021 ). All confirmed reports of fossil dipterocarps and related taxa in Africa and India ( e.g ., Ashton et al, 2021 ) are from much younger, post-Gondwanan strata, and even the Maastrichtian Dipterocarpus -type pollen from Sudan ( Morley, 2018 ) is ca.…”