Diversity and Homologies of Corystosperm Seed-Bearing Structures from the Early Cretaceous of Mongolia Aã B,C D E F Gongle Shi , Peter R
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Journal of Systematic Palaeontology ISSN: 1477-2019 (Print) 1478-0941 (Online) Journal homepage: https://www.tandfonline.com/loi/tjsp20 Diversity and homologies of corystosperm seed- bearing structures from the Early Cretaceous of Mongolia Gongle Shi, Peter R. Crane, Patrick S. Herendeen, Niiden Ichinnorov, Masamichi Takahashi & Fabiany Herrera To cite this article: Gongle Shi, Peter R. Crane, Patrick S. Herendeen, Niiden Ichinnorov, Masamichi Takahashi & Fabiany Herrera (2019) Diversity and homologies of corystosperm seed- bearing structures from the Early Cretaceous of Mongolia, Journal of Systematic Palaeontology, 17:12, 997-1029, DOI: 10.1080/14772019.2018.1493547 To link to this article: https://doi.org/10.1080/14772019.2018.1493547 Published online: 14 Jan 2019. Submit your article to this journal Article views: 142 View Crossmark data Full Terms & Conditions of access and use can be found at https://www.tandfonline.com/action/journalInformation?journalCode=tjsp20 Journal of Systematic Palaeontology, 2019 Vol. 17, No. 12, 997–1029, http://dx.doi.org/10.1080/14772019.2018.1493547 Diversity and homologies of corystosperm seed-bearing structures from the Early Cretaceous of Mongolia aà b,c d e f Gongle Shi , Peter R. Crane , Patrick S. Herendeen , Niiden Ichinnorov , Masamichi Takahashi and Fabiany Herrerad aState Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology and Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, Nanjing 210008, China; bOak Spring Garden Foundation, Oak Spring, Upperville, VA 20184, USA; cSchool of Forestry and Environmental Studies, Yale University, New Haven, CT 06511, USA; dChicago Botanic Garden, Glencoe, IL 60022, USA; eInstitute of Paleontology and Geology, Mongolian Academy of Sciences, Ulaanbaatar-51, Mongolia; fDepartment of Environmental Sciences, Niigata University, Ikarashi, Nishi-ku, Niigata 950-2181, Japan (Received 14 March 2018; accepted 21 June 2018) New discoveries of corystosperm seed-bearing structures from the Tevshiin Govi locality, Mongolia, which is of Early Cretaceous (Aptian–Albian) age, show that the individual seed-bearing units of Umkomasia mongolica were borne in a cone, as also documented for the very similar reproductive units of Doylea tetrahedrasperma. New material from the Tevshiin Govi locality also documents two additional species of Umkomasia – U. corniculata sp. nov. and U. trilobata sp. nov. – that most likely grew in a different environment to U. mongolica. The occurrence of three different Umkomasia species in the Early Cretaceous of Mongolia, together with other records from the Early Cretaceous of the Northern Hemisphere, indicate that previous concepts of corystosperms, based mainly on material from the Southern Hemisphere, need to be revised. The consistent reproductive architecture of the seed-bearing structures in all three corystosperm species, with a bract subtending a variously modified axis bearing ovules, is similar to the situation in Ginkgo and conifers. These underappreciated architectural commonalities among the reproductive structures of major groups of seed plants are likely significant for a deeper understanding of seed plant evolution and require further exploration. Keywords: corystosperms; Umkomasia; Early Cretaceous; Mongolia; seed; seed ferns Introduction produced by the same group of plants, a hypothesis that has been widely accepted (Crane 1985; Rothwell & Umkomasiaceae, commonly known as corystosperms, Serbet 1994; Doyle 2006; Hilton & Bateman 2006; are a key group of extinct Mesozoic plants that have Taylor et al. 2006; Taylor & Taylor 2009). long been central in discussions of the phylogeny and The close association of Umkomasia, Pteruchus and evolution of living seed plants (Thomas 1933; Crane Dicroidium has been confirmed by studies of corysto- 1985; Doyle 2006; Hilton & Bateman 2006; Taylor sperm fossils from other parts of the Southern et al. 2006; Taylor & Taylor 2009; Rothwell & Stockey Hemisphere (e.g. Townrow 1965; Holmes & Ash 1979; 2016). The family was proposed by Thomas (1933) for Holmes 1982; Retallack 1983; Cantrill et al. 1995; Yao the seed-bearing organs Umkomasia H. H. Thomas, et al. 1995; Axsmith et al. 2000; Holmes & Anderson Pilophorosperma H. H. Thomas and Spermatocodon H. 2005; Pattemore 2016b) and these plants have been H. Thomas, the pollen organs of Pteruchus H. H. reconstructed as small to large woody shrubs and trees Thomas and the bifurcate leaves of Dicroidium Gothan, based on anatomy of the stems associated with based on compressed material from the Late Triassic Dicroidium leaves (Archangelsky 1968; Meyer-Berthaud Molteno flora in Natal, South Africa. Although the dif- et al. 1992, 1993; Decombeix et al. 2014). ferent organs were not attached, their consistent associ- Corystosperms are thought to have evolved in the palae- ation in the same bed, the similarities in the structure of otropics during the Late Permian (Kerp et al. 2006; Abu their cuticles, and the presence of the same kind of pol- Hamad et al. 2008, 2017), later becoming a very prom- len in the pollen sacs of Pteruchus and in the micropyle inent element in Gondwanan terrestrial ecosystems dur- of Umkomasia seeds, suggest strongly that they were ing the Triassic (Anderson & Anderson 1983, 2003). à Corresponding author. Email: [email protected] # The Trustees of the Natural History Museum, London 2019. All rights reserved. Published online 14 Jan 2019 998 G. Shi et al. Corystosperms appear to have declined significantly in Ulaanbaatar (Leslie et al. 2013), during field seasons in the Southern Hemisphere prior to the biotic crisis 2011, 2012, 2013 and 2015. The Tevshiin Govi around the Triassic–Jurassic boundary (Retallack 1977; Formation is one of several Lower Cretaceous terrestrial Ash 1986; Bomfleur & Kerp 2010; Pattemore 2016a), coal/lignite bearing units in eastern and central although a few relicts may have persisted until as late Mongolia (Erdenetsogt et al. 2009). It comprises a as the Eocene (McLoughlin et al. 2008). sequence of terrestrial and fluvio-lacustrine deposits While corystosperms have been considered typical including conglomerates, sandstones and siltstones, as Triassic Gondwanan plants, occurrences of probable cor- well as thick coal and lignite seams (Ichinnorov 2003; ystosperms from the Triassic (Zan et al. 2008) and Ichinnorov et al. 2012). The formation is considered to Jurassic (Harris 1964; Kirchner & Muller€ 1992) of the be of Aptian–Albian age (125–100.5 Ma) based on Northern Hemisphere suggest that the group was much stratigraphical correlations (Erdenetsogt et al. 2009) and more widespread during the Mesozoic, and this is con- palynomorphs from the Tevshiin Govi locality firmed by recent descriptions of unequivocal corysto- (Ichinnorov 2003; Ichinnorov et al. 2012). sperms from the Early Cretaceous of Western North Extensive collections have been made from the America (Stockey & Rothwell 2009; Rothwell & Tevshiin Govi locality, with about 100 samples from 49 Stockey 2016) and North-eastern Asia (Shi et al. 2016). individual sample collection sites processed and analysed; This Early Cretaceous material has added new morpho- each sample is designated using a three-digit number with logical and anatomical information on the structure of the prefix ‘PSH’ (e.g. PSH261). Most of these collections corystosperm cupules, which is important because of have come from the lignites, which have yielded abun- their potential relevance for understanding the homolo- dant and well-preserved material, including the specimens gies of other seed plant reproductive organs, including of Umkomasia mongolica described previously (Shi et al. perhaps the anatropous ovules of angiosperms (Crane 2016) and the new specimens of this species described 1985; Frohlich 2003; Doyle 2006; Hilton & Bateman here. Much less extensively collected have been the clas- 2006; Frohlich & Chase 2007; Taylor & Taylor 2009). tic sediments associated with the lignites. The two new In this paper, we provide new information on the seed- species of Umkomasia come from six Tevshiin Govi sam- bearing structures described previously from Early ples (PSH177, 281, 286, 287, 288, 295), four of which Cretaceous lignites in central Mongolia as Umkomasia mon- (PSH177, 286, 287, 288) are from the carbonaceous golica G. Shi, A. B. Leslie, Herend., F. Herrera, Ichinnorov, sandy siltstones above the lignites. Takahashi, Knopf & P. R. Crane (Shi et al. 2016). We The lignites at Tevshiin Govi locality contain diverse, emend the diagnosis of U. mongolica to include features of abundant and exquisitely preserved plant fossils, including the seed cones and we suggest that the leaf of U. mongolica fertile and sterile fronds of the filmy fern Hymenophyllum is Pseudotorellia palustris G. Shi, F. Herrera, Herend., A. B. iwatsukii F. Herrera et al. (Hymenophyllaceae) (Herrera Leslie, Ichinnorov, Takahashi, & P. R. Crane (Shi et al. et al. 2017a), leaves of Podozamites (Presl) Braun, 2018). We reject the reassignment of U. mongolica to the Pseudotorellia Florin (Shi et al. 2018) and seed-bearing genus Doylea Stockey & G. W. Rothwell, as well as the structures of Umkomasia (Shi et al. 2016)and assessment that Doylea and U. mongolica are only distantly Umaltolepis Krassilov (Herrera et al. 2017b). Also related to corystosperms (Rothwell & Stockey 2016). We important in the Tevshiin Govi assemblages are abundant also describe two new species of corystosperm cupule from conifer leaves as well as seed cones