Sphagnum heinrichsii, Ignatov & Lamkowski & Ignatova & Perkovsky, 2019

Ignatov, M. S., Lamkowski, P., Ignatova, E. A. & Perkovsky, E. E., 2019, Mosses from Rovno amber (Ukraine), 4. Sphagnum heinrichsii, a new moss species from Eocene, Arctoa 28 (1), pp. 1-11 : 2-9

Sphagnum heinrichsii sp. nov. ( Figs. 1–42 ).

Holotype: Rovno amber. Late Eocene. SIZK-VT- 88 ( Fig. 1 ) [original piece of amber SIZK-VT-115 was cut into three parts, two containing parts of the Sphagnum plant(s): VT-88 ( Figs. 1-35 ) and VT-88A ( Figs. 36 с42) [scheme of their connection is in Fig. 3 ].

Etymology: In honour of Jochen Heinrichs (1969- 2018), outstanding German bryologist and paleobotanist.

Description: Stem longer than 1 cm, sparsely branched, with branches separated at ca. 2 mm one from another, branches single or in fascicles of two, one being much smaller than another. The bigger branches spreading from stem at right angles, as well as one branch (B 7 in Fig. 1 ) with considerably smaller leaves. Stem leaf (only one observed) small, lingulate, appressed, 0.7×0.3 mm; distal margin likely irregularly broken; hyalocysts of proximal to middle part broad, ca. 140×70 µm, towards margin and above elongated, to ca. 150–200× 50– 70 µm, on dorsal side with numerous imperfect pores (with clear outline but without true perforation) along commissures 17–23 µm in diameter, separated one from another by 5–10 µm, arranged in regular rows, occasionally with few similar pores along convex hyalocyst median part; perfect (with perforation) pores few, more numerous towards apex; chlorocysts exposed to dorsal surface as narrow strips ca. 5 µm close to leaf base among especially broad cells. Branch leaves on long branches apparently arranged in rows, up to 3.0×0.7 mm, narrow lanceolate, gradually tapered to apex, flat to concave near base; hyalocysts 200–280×25–30 µm, fibrils numerous at 15–20 µm from each other (in both large leaves and in leaf only 1 mm long); pores only in few cells, mostly in distal hyalocyst corners, more rarely also in proximal corners, occasionally in other parts of leaves (some cells near base of concave leaf part with large pores along whole cell); in middle leaf part mostly imperfect pores occur and in distal parts of leaves from pendent branches cells are almost undifferentiated into chlorocysts and hyalocysts; border of longer cells not apparent, although cells close to margin in proximal part of leaf somewhat narrower; leaves from small branches are only 200 µm long; leaves in proximal part of branch 0.5 mm long, its hyalocysts distally with some pores of quite small size, <5 µm.

Material: The piece of amber was cut into two unequal parts (before initial study). The Sphagnum specimen appeared mostly in a thinner slice, where its stem comes in from rough face, and then curved, lying parallel to the cutting. The stem is surrounded by amber metamorphosis along most length of the stem: it covers the stem surface so only one stem leaf ( SL in Figs. 1 , 3 , 30–35 ) is available for study (ca. 0.5 mm below there is probably another one, but it is only slightly visible by its end and not allowing to understand any details). Several branches appear to be closer to the cut and polished face, allowing clear view of branches and a single stem leaf. The polarity of stem is not evident per se. We interpret it as shown in Fig. 3 mostly considering two types of evidence: (1) concave stem leaf orientation; although we are aware of a not rare stem leaf downwards orientation in Sphagnum , it is unlikely that adaxial surface of small-sized stem leaf can be strongly convex as in Figs. 30–32 ; (2) branch assumed as pendent, B 6 ( Fig. 3 ), due to especially long, narrow and flexuose branch leaves, is likely directed downwards (as all pendent branches), despite during the fossilization its direction might be changed to unnatural direction. However, the coincidence of both of these facts justify our interpretation as the most probable.

The whole appearance of the plant, its coverage by debris and numerous diatoms indicates it grew submerged in water. Such environments sometimes result in a reduction in branching, so their single arrangement is unusual, but not totally exceptional. The bases of branches B 1 and B 7 are clearly visible, thus their solitary position is evident. Branch B 2 is likely also solitary, although the position of branches B 3, B 4 and B 5 ( B 5 is questionable whether this is branch however) are not clear enough to state anything definite about branch arrangement. The B 3 and B 4 ( Figs. 3 , 36 ) is the only case were a pair of two branches, apparently adjoining each other, is seen. We can not exclude that B 3 and B 4 can not be considered as one fascicle with B 2, and maybe B 5. Also B 6 base is not seen and one can not exclude its close position to B 7; however, these cases are much more hypothetical.

Three branches, B 1, B 2, and B 3, are characterized by the largest and densely arranged leaves, and their position at about a right angle from the stem indicate that they are spreading. Uppermost branch leaves of them are not available for study, but all three leaves in lower few millimeters are appressed and rather flat, and only on B 2 at ca. 5 mm from branch base the leaves are more loose, with concave bases ( Figs. 4–7 ).

Branch B 6 is seen partly, without its basal part, but its orientation is pendent, and uppermost leaves are narrow and flexuose; i.e., similar to pendent branches. Shoot B 6a is difficult to interpret: it could be either a terminal continuation of B 6, or a separate branch similar to B 7, but fallen off and retained close to the mother plant. Leaves of B 6a are very similar in shape and size to B 7.

Stem leaf ( Figs. 30–35 ) is partly emerging above alveolar medium surrounding stem. However, what is possible to see through this rather transparent amber, is its basal part and an indefinite part is its distal edge, which likely consists of partly decomposed cells. Micrographs with more intensive transmitted light show numerous pores (e.g. Fig. 35 ); however, in reflected light it is seen that they are mostly imperfect pores ( Figs. 30, 32 ).

In branch leaves (e.g. Fig. 23 ) imperfect pores are also much more common than true window pores, which are more numerous only in concave leaf bases ( Figs. 5–7 ).

Figures

Figs. 1 & 2: Sphagnum heinrichsii (holotype): (1) general view with number indicating parts of plants shown by closeups in subsequent pictures; (2) slightly enlarged view of holotype at a slightly different angle.SL: stem leaf, B1–B7: branches numbered for ease of discussion. The putative remains of one of pendent branches are denoted as?B5 (its interpretation as a branch is not certain). Branch B3 (shown in Fig. 35) is situated at angle of ca. 70° to the polished surface of amber piece with the main part of specimen. SL (cf. Fig. 3). Branch B6a may represent apical part of B6 or otherwise the separate branch (similar to B7), fallen off and lying near the end of B6.

Fig. 3: Scheme of Sphagnum heinrichsii position in two amber pieces, with numbering of branches (B1, B2, etc.) for ease of discussion, and showing position of stem leaf (SL).

Figs. 4–7: Sphagnum heinrichsii (holotype): branch (3) and lower parts of branch leaves (4–6), showing pores mostly in distal ends of hyalocysts, however at places (especially in the middle of convex surface near leaf bases, vf. 6 and 7) scattered along whole cells. Marginal and submarginal cells (6, below, right) narrower and eporose.

Figs. 8–11: Sphagnum heinrichsii (holotype): dorsal surface of branch leaves showing pores mostly in distal ends of hyalocysts.

Figs. 12–20: Sphagnum heinrichsii (holotype): dorsal surface of branch leaves showing pores in ends of hyalocysts. Three series (11–13, 14–16, 17–19) show tree photos each with different focus to better understanding of pore position.

Figs. 21-24: Pendent branch leaves of Sphagnum heinrichsii (holotype) and their areolation. (21–22): upper part of branch leaves with longly attenuate and narrowed acuminae, which are flexuose and irregulary crumples. 21 taken from back, “raw” face of specimen; 22 from polished side, as all other photos; 23: median cells of long leaf closer to distal part of pendent branch; they are only slightly porose, with many inperfect pores (seen as rings covered by cell walls); (24) cells closer to leaf apex: pores are totally or almost totaly absent.

Figs. 25-29: Sphagnum heinrichsii (holotype): 25: spreading branch B1, with leaves quite strongly covered by mud and detritus (26, 27), and diatoms (28). 29 is a small leaved branch B6a (unclear if it is a continuation of B6 or a separated bench), where leaves also covered by mud and quite damaged. Note a very few pores, mostly confined to upper hyalocyst corners in B6a.

Figs. 30-35: Sphagnum heinrichsii (holotype): 31: branch with small leaves (B7), with a stem leaf near its base; the lower leaf from this branch have pores very variable in size on cell dorsal surface near leaf apex (33). Stem leaf by its overall habit (30 and 32) looks having not slightly porose cells, as pores are mostly imperfect, without perfo- ration; however under higher magnification and additional transmitted light abundant pores are apparent (34, 35).

Figs. 36–42: Sphagnum heinrichsii (holotype, cut off second part). 30: General view: upper part of branch with large leaves (close up in Fig. 31) and attached (seemingly close to its base) small-leaves branch, partly cut longitudinally. Details of the latter branch are showin in Figs. 32–36: it bears one leaf ca. 1 mm long close to its base (Figs. 32-33), while leaves closer to its tip are only 200 µm long (Fig. 34). Fig 35 shows part of this tiny branch, only 50 µm thick. Fig 36 comprise longitudinal section of small leaf close to branch tip showing fibrils.