New fossil Pinaceae from the Early Cretaceous of Mongolia

Bickner

et al. 2021

American J of Botany

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Premise: Seed cones of extant Pinaceae exhibit two mechanisms of seed release. In "flexers" the cone scales remain attached to the central axis, while flexing and separating from each other to release the seeds. In "shedders" scales are shed from the axis, with the seeds either remaining attached to the scale or becoming detached. The early fossil history of Pinaceae from the Jurassic to Early Cretaceous is dominated by flexing seed cones, while the systematic information provided by shedding fossil cones has been overlooked and rarely integrated with data based on compression and permineralized specimens. We describe the earliest and best-documented evidence of a "shedder" seed cone from the Aptian-Albian of Mongolia. Methods: Lignite samples from Tevshiin Govi locality were disaggregated in water, washed, and dried in air. Fossils were compared to material of extant Pinaceae using LM and CT scans. Results: Lepidocasus mellonae gen. et sp. nov. is characterized by a seed cone that disarticulated at maturity and shed obovate bract-scale complexes that have a distinctive ribbed surface and an abaxial surface covered with abundant trichomes. The ovuliferous scale has ca. 30-40 resin canals, but only scarce xylem near the attachment to the cone axis. Resin vesicles are present in the seed integument. Phylogenetic analysis places Lepidocasus as sister to extant Cedrus within the abietoid grade. Conclusions: The exquisite preservation of the trichomes in L. mellonae raises questions about their potential ecological function in the cones of fossil and living Pinaceae. Lepidocasus mellonae also shows that a shedding dispersal syndrome, a feature that has often been overlooked, evolved early in the history of Pinaceae during the Early Cretaceous.

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Early Cretaceous abietoid Pinaceae from Mongolia and the history of seed scale shedding

Herrera

Bickner

et al. 2021

American J of Botany

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“…iwatsukii in the lignite floras and the exquisite preservation also suggest little long distance transport from the place of growth. The Tevshiin Govi and Tugrug floras were dominated by conifers and other gymnosperms, some of them deciduous, including conifers such as Krassilovia (Herrera et al, 2015; Shi et al, 2017), Schizolepidopsis , Picea , and Pityostrobus in Pinaceae (Leslie et al, 2013; Herrera et al, 2016), Elatides , Stutzeliastrobus , and Pentakonos in Cupressaceae (Shi et al, 2014; Herrera et al, 2017b), the putative ginkgophyte plant Umaltolepis (Herrera et al, 2017a), as well as the corystosperm Umkomasia (Shi et al, 2016). The authors hypothesize that H .…”

Section: Discussionmentioning

confidence: 99%

An exquisitely preserved filmy fern (Hymenophyllaceae) from the Early Cretaceous of Mongolia

Herrera

Moran

et al. 2017

American J of Botany

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Hymenophyllum iwatsukii was likely an epiphyte based on the sedimentary environment in which the fossils are preserved, the associated fossil flora, and the growth habit of extant species of Hymenophyllum. The new fossil species underlines the extent to which morphological characters in Hymenophyllum have been conserved despite significant tectonic, climatic, ecological, and floristic changes since the Early Cretaceous.

“…The shed parts of the Krassilovia plant are a significant component of the Tevshiin Govi lignite, which shows no evidence of higher energy input and appears to have accumulated largely autochthonously. Growing alongside the Krassilovia plant were a variety of other presumed trees, including taxa related to extant Pinaceae (Schizolepidopsis, Picea, Pityostrobus, [65,86]), Cupressaceae (Elatides, Stutzeliastrobus, Pentakonos, [64,87], and the ginkgophyte Umaltolepis [70], as well as plants that may have been shrubs, such as the corystosperm Umkomasia [31,32]. The absence of lycopods and ferns (as macrofossils, mesofossils, or megaspores), other than the epiphytic filmy fern Hymenophyllum [88], suggests there was little or no herbaceous vegetation.…”

Section: Paleoecology Of the Krassilovia Mongolica-podozamites Harrismentioning

confidence: 99%

Reconstructing Krassilovia mongolica supports recognition of a new and unusual group of Mesozoic conifers

Herrera¹,

Mays

et al. 2020

PLoS ONE

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Previously unrecognized anatomical features of the cone scales of the enigmatic Early Cretaceous conifer Krassilovia mongolica include the presence of transversely oriented paracytic stomata, which is unusual for all other extinct and extant conifers. Identical stomata are present on co-occurring broad, linear, multiveined leaves assigned to Podozamites harrisii, providing evidence that K. mongolica and P. harrisii are the seed cones and leaves of the same extinct plant. Phylogenetic analyses of the relationships of the reconstructed Krassilovia plant place it in an informal clade that we name the Krassilovia Clade, which also includes Swedenborgia cryptomerioides-Podozamites schenkii, and Cycadocarpidium erdmanni-Podozamites schenkii. All three of these plants have linear leaves that are relatively broad compared to most living conifers, and that are also multiveined with transversely oriented paracytic stomata. We propose that these may be general features of the Krassilovia Clade. Paracytic stomata, and other features of this new group, recall features of extant and fossil Gnetales, raising questions about the phylogenetic homogeneity of the conifer clade similar to those raised by phylogenetic analyses of molecular data.