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

Abstract

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.

Gene duplications and phylogenomic conflict underlie major pulses of phenotypic evolution in gymnosperms

“…The traits examined (and their corresponding states) are listed in Supplementary Information, and we indicate how these relate to traits in previously published datasets. The primary source datasets were those of Hart 95 , Hilton and Bateman 96 , Mao et al 97 , Escapa and Catalano 98 , Coiro and Pott 99 , Herrera et al 100,101 , Gernandt et al 102 , and Andruchow-Colombo et al 103 See Supplementary Information for a complete list of references from which phenotypic data were obtained. We note that while determining homology for character delimitation in seed plants is a major challenge 104 , we do not believe that instances of misidentified homology (i.e., treating independently evolved structures as a single trait or expression of a trait) should necessarily undermine our goals here, given that we are not using this trait set to reconstruct phylogeny.…”

“…The traits examined (and their corresponding states) are listed in Supplementary Information, and we indicate how these relate to traits in previously published datasets. The primary source datasets were those of Hart 92 , Hilton and Bateman 93 , Mao et al 94 , Escapa and Catalano 95 , Coiro and Pott 96 , Herrera et al 97,98 , Gernandt et al 99 , and Andruchow-. CC-BY-NC-ND 4.0 International license available under a (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.…”

Ovulate Cones of Schizolepidopsis ediae sp. nov. Provide Insights into the Evolution of Pinaceae

“…nov., based on ovulate cones from the Early Cretaceous of Mongolia and China preserved as both lignitized compressions and siliceous permineralizations. This species is a new addition to a diverse conifer assemblage documented from the Early Cretaceous of Mongolia (Leslie et al 2013;Shi et al 2014;Herrera et al 2015Herrera et al , 2016Herrera et al , 2017Herrera et al , 2020. The exceptional preservation of these fossils has facilitated observations of external morphology and internal anatomy at different developmental stages, providing insights into the natural history of this species.…”

“…The discovery of a new species of Schizolepidopsis at Tevshiin Govi adds to the diversity of the conifer assemblage at this locality. To date, six other conifer species have been described from Tevshiin Govi, as follows: the voltzialean Krassilovia mongolica Herrera, Leslie, Shi, Knopf, Ichinnorov, Takahashi, Crane et Herendeen; two species of Cupressaceae, Pentakonos diminutus Herrera, Shi, Knopf, Leslie, Ichinnorov, Takahashi, Crane et Herendeen and Stutzeliastrobus foliatus Herrera, Shi, Knopf, Leslie, Ichinnorov, Takahashi, Crane et Herendeen; and three pinaceous conifers, S. canicularis, Picea farjonii Herrera, Leslie, Shi, Knopf, Ichinnorov, Takahashi, Crane et Herendeen, and Pityostrobus stockeyae Herrera, Leslie, Shi, Knopf, Ichinnorov, Takahashi, Crane et Herendeen (Leslie et al 2013;Herrera et al 2015Herrera et al , 2016Herrera et al , 2017Herrera et al , 2020. In addition, two or more species of Schizolepidopsis cooccur at Tevshiin Govi in Mongolia (S. ediae and S. canicularis) and in the Huolinhe Formation of Inner Mongolia, China (S. ediae, S. longipetiolus, and S. moelleri), highlighting the diversity of the genus during the Late Cretaceous of East Asia (Domogatskaya and Herman 2019).…”

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

“…It has also been reconstructed for Krassilovia mongolica, an extinct conifer that grew together with L. mellonae. The shedder dispersal syndrome of K. mongolica is also based on the recovery of several thousands of disarticulated seed cone scales and anatomical features (Herrera et al, 2015(Herrera et al, , 2020.…”