Stutzeliastrobus bohemicus (BAYER) J.KVAČEK 2018

Kvaček, Jiří, Heřmanová, Zuzana, Bruthansová, Jana, Karch, Jakub, Žemlička, Jan & Dudák, Jan, 2018, Stutzeliastrobus Bohemicus Comb. Nov. - Basal Cupressaceae Conifer From The Cenomanian Of The Bohemian Cretaceous Basin, Central Europe, Fossil Imprint 74 (1 - 2), pp. 179-188 : 182-186

Stutzeliastrobus bohemicus (BAYER) J.KVAČEK comb. nov.

Text-figs 1–5

B a s i o n y m. Cyparissidium bohemicum BAYER 1914 , Archiv pro přírodovědecké prozkoumání Čech, 15(5), p. 43, text-figs 21–23.

1914 Cyparissidium bohemicum BAYER , p. 43, text-figs 21–23.

1920 Cyparissidium bohemicum BAYER ; Bayer, p. 50, text-figs 21–23.

1968 Cyparissidium bohemicum BAYER ; Němejc, p. 393, text-fig. 301a, pl. 38, fig. 4.

L e c t o t y p e. NM-F 2746, designated here in, Text-figs

1a–f, 2, 3a, c–f, housed in the National Museum, Prague.

P l a n t F o s s i l N a m e s R e g i s t r y N u m b e r. PFN000138 for new combination; PFN000140 for lectotype designation .

T y p e l o c a l i t y. Harcov near Dvůr Králové n.

Labem, the Czech Republic.

T y p e h o r i z o n. Cretaceous, Cenomanian, Peruc

Korycany Formation.

E m e n d e d d i a g n o s i s. Elongate ovuliferous cones born terminally on twigs. Ovuliferous cones consisting of about 60 helically arranged imbricate bract-scale complexes. Each bract-scale complex simple, thin, flat, bilaterally symmetrical, delicately ribbed, with base narrowing, cuneate, entire-margined, apex obovate, irregularly delicately dentate, terminating with a mucro. There are two or three inverted seeds per cone scale. Seeds are elliptical, ovoid, sometimes asymmetrical, with distal wing. Sterile twigs with helically arranged rhomboidal, imbricated Cyparissidium – type leaves with obtuse apex and delicate abaxial keel, appressed to stem. Leaves amphistomatic, adaxial cuticle bearing two stomatal bands with transversely or obliquely orientated monocyclic to amphicyclic stomata surrounded by 4–6 subsidiary cells, ordinary epidermal cells elongate; abaxial cuticle bearing monocyclic to amphicyclic stomata scattered irregularly in basal part of leaf, ordinary epidermal cells isodiametric. Hypodermis strongly cutinised.

M a t e r i a l s t u d i e d. NM-F 864, F 872, F 877, F

875a, b, F 1414, F 2742, F 2744, F 2840, F 4551.

D e s c r i p t i o n. Reproductive structures. The lectotype ( Text-figs 1a–d , 2 , 3a, c–f ) is a fragment of basal and medial parts of an ovuliferous cone 45 mm long and 25 mm broad. It is born on a twig and represents the best preserved specimen, being lignified, partly coalified and 3D preserved. It consists of more than 60 helically arranged bract-scale complexes ( Text-figs 1b , 2 ). Text-fig. 1a shows external surface of the ovuliferous cone, while Text-figs 1b , 2 display the cone surface buried in sediment. Each bract-scale complex is deltoid, having an entire-margined cuneate base ( Text-fig. 1e, f ) and oblong ovate apex with delicate teeth and terminal mucro. Text-fig. 3a shows the basal part of the adaxial surface of the bract-scale complex with centrally placed thickened stalk (arrow). The abaxial surface of the bractscale complex is delicately ribbed ( Text-fig. 1b ). MicroCT study revealed numerous morphological and anatomical details used for the emended diagnosis, particularly the arrangement of seeds ( Text-figs 1e, f , 3c–e ). The seeds are arranged in the basal part of the bract-scale complexes ( Text-figs 1e, f , 3a ), typically two or three ( Text-fig. 1e, f ). The mature seeds ( Text-fig. 3d, e ) are ovoid, 5–5.6 mm long and 3–3.2 mm broad; immature seeds ( Text-fig. 3b, f ) are smaller, 3–3.5 mm long and 2–2.5 mm broad. The wing is arranged in the distal part ( Text-fig. 3b, c, e ).

The specimens figured in Bayer (1914: figs 21a, b, 22a, 23a; 1920: figs 21a, b, 22a, 23a) are not so well preserved; they are mostly impressions of external cone surfaces ( Text-fig. 3a ). Specimen No. NM-F 4551 ( Bayer 1914: fig. 21a) shows a basal part of a cone (60 × 30 mm), showing an impression of its external surface ( Text-fig. 4a ), with fragments of lignified deltoid bracts-scale complexes 10–11 × 5–7 mm in size. One of them has a preserved terminal part with a well-preserved mucro ( Text-fig. 4a , arrow).

Specimen NM-F 872 ( Bayer 1914: fig. 21b; 1920: fig. 21b) display a twig 60 mm long, 2 mm broad, with two branchlets and terminally born ovuliferous cone (36 × 6 mm; Text-fig. 4b ). The branchlets, angled off at 30°, are 30 and 35 mm long. The ovuliferous cone (8 × 35 mm) is longitudinally broken, bearing helically arranged bractscale complexes. Its cone-scales are smaller (4 × 6 mm) and arranged helically, some showing winged seeds ( Text-fig. 3b ).

Sterile foliage. Fragments of branches are preserved as leaf compressions ( Text-figs 4 , 5a–c ). The most complete branch was figured by Bayer (1914: fig. 21c; 1920: fig. 21c; No. NM-F 877), showing leaves rhomboidal, keeled, amphistomatic ( Text-fig. 5f ). Helically arranged leaves are small (0.8 mm broad, 1– 0.8 mm long), appressed to the axis ( Text-fig. 5c ).

The adaxial cuticle is thinner than the abaxial cuticle ( Text-fig. 5d ), it shows two stomatal bands 80–150 μm wide ( Text-fig. 5e ). Ordinary epidermal cells (10–25 × 25–45 μm) are elongate to polygonal, with straight anticlinal walls. Monocyclic to amphicyclic stomata with well-cutinized guard cells are sunken in oval pits surrounded by 4–6 unspecialized subsidiary cells (10–25 × 25–40 μm) (Textfig. 5f). They are orientated transversely or obliquely to the leaf margin ( Text-fig. 5d ). The hypodermis is cutinized, and it was difficult to remove its remnants from the preparation. The abaxial cuticle is thicker than the adaxial, and shows only few stomata ( Text-fig. 4d ); ordinary cells are quadrangular, nearly isodiametric (25–40 × 35– 80 μm) with straight or bent anticlinal walls ( Text-fig. 4f ). Fresh material collected in the locality by JK in 1997 was used for SEM studies (NM-F 2840) and further cuticle preparations (NM-F 2747). It shows details of a leafy shoot ( Text-fig. 4c ). Basal parts of leaves are covered by irregularly scattered oval pits that probably represent stomata.

D i s c u s s i o n. Fossil remains of this conifer were collected and described by Bayer (1914, 1920) who assigned them to the genus Cyparissidium , based particularly on observations of foliage. MicroCT studies of the wellpreserved specimen, suggested here as a lectotype, allowed a more accurate interpretation of the ovuliferous cone and twig, and a better description of its anatomy. Based on this new data, we were able to compare the cone with previously described taxa with well-preserved anatomy, rather than with only compressed specimens. The comparison mentioned in the discussion to the genus resulted in a new interpretation of this conifer, and its transfer to the recently described genus Stutzeliastrobus .

Stutzeliastrobus bohemicus differs from S. foliatus F. HERRERA et al., 2017 in having ribbed cone-bract complexes, delicately toothed in their terminal parts, and large ovoid seeds.

Foliage of Stutzeliastrobus bohemicus is very similar in appearance to Cyparissidium gracile (HEER) HEER from the Cretaceous of Greenland ( Heer 1868: pl. 43, figs. 1e, 3c; Heer 1874: pl. 17, fig. 5b, c, pl. 18, fig. 6b, pl. 19, figs 1–11, pl. 20, fig. 1e, pl. 21, figs 9b, 10d). The type specimens stored in Naturhistoriska riksmuseet, Stockholm, were sampled for cuticle analysis, but without success. The best cuticle preparations were obtained from non-figured material (S 087443), the locality of Ekkofrat. The cuticle pattern of both taxa is also very similar. The type material of C. gracile yields only one incomplete ovuliferous cone ( S 87438 , S 105123, part and counterpart – Heer 1874: pl. 19, figs 8, 9b), which is poorly preserved, so it is difficult to compare it with S. bohemicus .

As already mentioned by Harris (1979), the species C. gracile , although used as the type of the genus, shows characters of the broadly defined genus Brachyphyllum . The same problem existed with the species C. bohemicum . This problem for the Czech material is now solved, due to the well-preserved lectotype, which allowed its transfer to the genus Stutzeliastrobus .

The leaves of Stutzeliastrobus bohemicus resemble those of Taiwania , showing similar morphology and micromorphology of epidermis: mature leaves of Taiwania are shortly decurrent, keeled, amphistomatic and appressed to the stem ( Farjon 2005).

From other fossil cupressoid conifers, Stutzeliastrobus bohemicus is most similar to Cunninghamiostrobus yubariensis STOPES et FUJII from the Late Cretaceous of Japan ( Ohana and Kimura 1995). Stutzeliastrobus bohemicus differs from Cunninghamiostrobus yubariensis in having rhombic flat, non-peltate bract-scale complex, but lacking adaxial socket-like cavities and pronounced interseminal ridges.

Another similar fossil conifer genus, Austrohamia , contains two species: Austrohamia minuta ESCAPA, CÚNEO et AXSMITH from the Early Jurassic of Argentina ( Escapa et al. 2008: fig. 11O) and Austrohamia acanthobractea J.WEI ZHANG, D’ROZARIO, L.I.WANG, Y.LI et J.YAO from the Middle – Late Jurassic of China ( Zhang et al. 2012). They both have bract-scale complexes similar to Stutzeliastrobus bohemicus , but differ in having only one or two seeds per bract-scale complex ( Herrera et al. 2017).

Juvenile cone scale complexes Athrotaxites stockeyi ESCAPA et al., 2016 ( Escapa et al. 2016) from the Late Cretaceous of USA have a similar number of seeds per scale complex (3–4), but differ from Stutzeliastrobus bohemicus in having an ovuliferous cone scale complex already robustly thick in the juvenile stage.

Parataiwania nihongii M.NISHIDA et al. from the Late Cretaceous of Japan ( Nishida et al. 1992) differs from S. bohemicus in having a thicker bract-scale complex of ligulelike shape, more like Cunninghamia .

Compression/impression material of Taiwania cryptomeroides described from the Early Cretaceous to Pliocene localities of Siberia, Japan and Alaska is discussed and summarised by LePage (2009). The paper documents the probable existence of the taxon in Alaska since the Late Cretaceous, but due to the poor preservation of the fossil plant material, particularly ovuliferous cones, this assumption remains open until better material becomes available. The same is true for ovuliferous cones and twigs of Taiwania schaefleri SCHLOEMER- JÄGER described from the Palaeocene of Svalbard ( Schloemer-Jäger 1958, Budancev and Golovneva 2009).

Figures

Text-fig. 1. Stutzeliastrobus bohemicus (BAYER) J.KVAČEK, No. NM-F 2746, Harcov, lectotype. a – surface view of ovuliferous cone photograph, scale bar 10 mm, b – microCT isosurface of ovuliferous cone, scale bar 10 mm, c – microCT longitudinal section of ovuliferous cone with segmented seeds, scale bar 10 mm, d – microCT longitudinal section of ovuliferous cone in yellow, seeds in red, e – 3D visualised bract-scale complex bearing three seeds, adaxial view, scale bar 2.5mm, f – 3D visualised bract-scale complex bearing two seeds, lateral view (incomplete reconstruction of the scale visualises the front seed), scale bar 2.5mm.

Text-fig. 2. Stutzeliastrobus bohemicus (BAYER) J.KVAČEK, No. NM-F 2746, Avizo reconstruction showing ovuliferous cone with helically arranged bract-scale complexes (green and yellow) and seeds (blue), scale bar 10 mm.

Text-fig. 3. Stutzeliastrobus bohemicus (BAYER) J.KVAČEK, Harcov. a – surface view of bract-scale complex (arrow) and probably aborted seed, No. NM-F 2746 (lectotype), scale bar 1 mm, b – seed with a wing (arrow) NM-F 872, scale bar 1 mm, c – microCT perpendicular section of bract scale complex showing two seeds with wings (arrows), No. NM-F 2746 (lectotype), scale bar 1 mm, d – microCT longitudinal section of bract scale complex showing three seeds, No. NM-F 2746 (lectotype), scale bar 1 mm, e – microCT longitudinal section of bract scale complex with one seed reconstructed showing micropyle (arrow), No. NM-F 2746 (lectotype), scale bar 1 mm, f – isolated seed with a fragment of wing (arrow), No. NM-F 2746 (lectotype), scale bar 1 mm.

Text-fig. 4. Stutzeliastrobus bohemicus (BAYER) J.KVAČEK, Harcov. a – ovuliferous cone showing apical parts of bract-scale complexes, NM-F 4551, scale bar 10 mm, b – shoot with attached ovuliferous cone (Bayer 1914: fig. 21b; 1920: fig. 21b), NM-F 872, scale bar 1 mm, c – SEM of isolated shoot, NM-F 2840, scale bar 0.5 mm, d – LM of abaxial cuticle and hypodermis, NM-F 872b, scale bar 200 µm, e – LM of abaxial cuticle showing two stomatal bands (arrows) and hypodermis, NM-F 872b, scale bar 100 µm, f – LM of abaxial cuticle, detail of e showing stomata (arrows), NM-F 872b, scale bar 50 µm.

Text-fig. 5. Stutzeliastrobus bohemicus (BAYER) J.KVAČEK, Harcov. a – Shoots of various thickness, NM-F 875 (Bayer 1914: fig. 22c, d; 1920: fig. 22c, d), scale bar 10 mm, b – detail of branch showing imbricate rhomboidal leaves, NM-F 2744, scale bar 2 mm, c – branched twig, NM-F 877 (Bayer 1914: fig. 21c; 1920: fig. 21c), scale bar 10 mm.