Physcidium HEDENÄS, BOMFLEUR, 2023

Bomfleur, Benjamin, Hedenäs, Lars, Friis, Else Marie, Crane, Peter R., Raunsgaard, Kaj, Pedersen, Mendes, Mário Miguel & Kvaček, Jiří, 2023, Fossil Mosses From The Early Cretaceous Catefica Mesofossil Flora, Portugal - A Window Into The Mesozoic History Of Bryophytes, Fossil Imprint 79 (2), pp. 103-125 : 107-108

Family Diphysciaceae M. FLEISCH., 1919

Genus Physcidium HEDENÄS, BOMFLEUR et E.M. FRIIS gen. nov.

T y p e s p e c i e s. Physcidium tortuosum HEDENÄS,

BOMFLEUR et E.M. FRIIS

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.

PFN003146.

E t y m o l o g y. The name is an anagram of Diphyscium

D. MOHR, 1803, an extant moss genus, and is chosen to indicate strong resemblance to the gametophyte of the extant genus.

G e n e r i c d i a g n o s i s. Leaves with an oblong basal portion narrowing above to become linear, long, narrow and parallel-sided, with a shortly narrowed to obtuse or rounded apex. Costa occupying 25–35 % of leaf width. Costa with

1–2 layers of guide cells, only abaxial stereids, or both abaxial and adaxial stereids, and an epidermis that may or may not be differentiated. Upper leaf lamina 2–4-stratose, cells papillose. Cells of basal lamina sometimes partly inflated.

D i s t i n g u i s h i n g f e a t u r e s. Similar to modern

Diphyscium , but with a 1–2-stratose basal lamina and basal leaf cells that may be partly inflated. The leaves of

Physcidium species are also smaller, 1–2 mm long, whereas in most Diphyscium species the vegetative leaves are typically larger and 3–7 mm long. The few extant species of Diphyscium with shorter leaves lack inflated basal cells.

In addition, their costa has either more numerous layers of adaxial stereids or the stereids and guide cells are poorly differentiated.