DOI: 10.5061/dryad.23h4r85
title: Maiaspora: a new miospore genus with enigmatic sculpture from the late Visean of European Russia

description: We describe a new miospore genus Maiaspora gen. nov. from the upper Visean
 (middle Mississippian) of the southern wing of Moscow Syneclise (European
 Russia). A combination of methods (optical light microscopy (LM),
 scanning-electron microscopy (SEM), confocal laser microscopy (CLSM) and
 image-analysis) to study the same individual miospore specimens revealed a
 remarkable sculptural type for which we propose the new term
 ‘metareticuloid’. Metareticuloid sculpture is defined as a complex
 arrangement of muri with apiculate elements, polygonal lumina and circular
 scrobiculae at the base of the lumina. The discovery of fossil spores with
 metareticuloid sculpture allows the recognition of clear morphological
 differences between microreticulate and foveolate sculptures which
 palynologists have historically had difficulty in separating. Virtual
 cross-sections provided by CLSM show that miospores with metareticuloid
 sculpture display perfectly-preserved, funnel-shaped tunnels (like a
 gallery of cave stalactites) in the deep exospore. In contrast, miospores
 with microreticulate or reticulate and partly-vermiculate sculpture lack
 such vertical tunnels (termed scrobiculae). The morphology of Maiaspora
 gen. nov. is considered in comparison with Microreticulatisporites (Knox
 non sensu Potonié et Kremp) Bhardwaj emended Oshurkova,
 Pseudoreticulatispora Bharadwaj et Srivastava emended Price et Foster,
 Vadaszisporites (Deák et Combaz) emended Juhasz, Foveosporites Balme,
 Foveotriletes van der Hammen ex Potonié, Garotriletes Singh et Singh,
 Assamiasporites Mehrota et Sah, Margotriletes Mehrota et Sah. The
 morphological conceptions of Microreticulatisporites and Foveotriletes are
 reinterpreted by numerical typification. The adaptative significance of
 metareticuloid sculpture is discussed in relation to modern and fossil
 spores, and in terms of harmomegathic mechanisms of angiosperm pollen.
description: Maiaspora 51
 VirtualMaiaspora 54
 VirtualSeries of slides are
 provided by confocal scanning electron microscopy. Miospore specimen 54 of
 Maiaspora panopta.Maiispora 40
 VirtualSeries of slides are
 provided by confocal scanning laser microscopy. Miospore specimen 40 of
 Maiaspora panopta.Microreticulatisporites
 concavus 1 VirtualSeries of slides are
 provided by confocal scanning laser microscopy. Miospore specimen 1 of
 Microreticulatisporites concavus.Microreticulatisp-1
 Virtual.aviMicroreticulatisporites
 concavus - 73 VirtualSeries of slides are
 provided by confocal scanning laser microscopy. Miospore specimen 73 of
 Microreticulatisporites concavusMicroreticulatisp-2
 Virtual.aviFigure 19
 (Supplemental)SEM photomicrographs of
 Maiaspora panopta gen. et sp. PIN RAS. A, miospore specimen 336-13, distal
 aspect; B, miospore specimen 336-17, distal aspect; C, miospore specimen
 336-15, distal aspect; D, miospore specimen 336-16, proximal aspect; E,
 miospore specimen 336-14, distal aspect; F, miospore specimen 336-41,
 distal aspect; G, miospore specimen 336-18; proximal aspect; H, miospore
 specimen 336-20; proximal aspect; I, miospore specimen 336-22, proximal
 aspect; J, miospore specimen 336-21, distal aspect; K, miospore specimen
 336-19, distal aspect; L, miospore specimen 336-23, proximal aspect. Scale
 bar = 10 µm.Figure 20
 (Supplemental)SEM photomicrographs of
 Maiaspora panopta gen. et sp. PIN RAS. A, miospore specimen 336-37, distal
 aspect; B, miospore specimen 336-43, proximal aspect; C, miospore specimen
 336-38, proximal aspect; D, miospore specimen 336-33, distal aspect; E,
 miospore specimen 336-32, distal aspect; F, miospore specimen 336-31,
 equatorial-proximal aspect; G, miospore specimen 336-40, equatorial
 aspect; H, miospore specimen 336-36, distal-equatorial aspect; I, miospore
 specimen 336-38, proximal aspect. Scale bar = 10 µm.Figure 21
 (Supplemental)SEM photomicrographs of
 Microreticulatisporites concavus (A–C), Maiaspora panopta gen. et sp. (D,
 F–I), and Microreticulatisporites sp. (E) PIN RAS. A, miospore specimen
 336-50, proximal aspect, BSE mode; B, miospore specimen 336-51, distal
 aspect; C, miospore specimen 336-52, equatorial-proximal aspect; D,
 miospores specimen 336-53, distal aspect; E, miospore specimen 336-54,
 proximal aspect; F, miospore specimen 336-55, equatorial aspect; G,
 miospore specimen 336-56, proximal aspect; H, miospore specimen 336-57,
 proximal aspect; I, miospore specimen 336-58, distal aspect. Scale bar =
 10 µm.Figure 22
 (Supplemental)CLSM virtual
 reconstructions of Maiispora panopta gen. et sp. nov showing fluorescent
 exospore and non-fluorescent vertical tunnels on equatorial margin. A-C,
 miospores specimen 336-52; A, surface mode, proximal aspect; B,
 transparent mode, virtual plane close to proximal focus, tunnels visible;
 C, virtual plan close to distal focus; D-F, miospore specimen 336-29; D,
 surface mode, distal aspect; E, transparent mode, virtual plane close to
 proximal focus, tunnels visible; F, virtual plane close to distal focus;
 G-I, miospore specimen 336-53; G, surface mode, proximal aspect; H,
 transparent mode, virtual plane close to distal focus, tunnels visible; I,
 virtual plane close to proximal focus. Scale bars = 5
 µm.Source_
 file_morphometryThe data file contains a
 series of measurements of area, Wadell`s diameter of lumina, scrobiculae,
 a distance of the mass centres, muri width, the coefficient of variation,
 ratio w\W. All measurements were provided on detailed SEM micrographs of
 miospore specimens of Maiaspora panopta gen. et sp. nov,
 Microreticulatisporites concavus, and SEM micrographs of comparable in
 situ spores.