''Danziella'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of extinct

vascular plant Vascular plants (), also called tracheophytes () or collectively Tracheophyta (), form a large group of land plants ( accepted known species) that have lignified tissues (the xylem) for conducting water and minerals throughout the plant. They al ...

s of the

Early Devonian The Early Devonian is the first of three Epoch (geology), epochs comprising the Devonian period, corresponding to the Lower Devonian Series (stratigraphy), series. It lasted from and began with the Lochkovian Stage , which was followed by the P ...

(around ). Fossils found in the

Artois Artois ( ; ; nl, Artesië; English adjective: ''Artesian'') is a region of northern France. Its territory covers an area of about 4,000 km2 and it has a population of about one million. Its principal cities are Arras (Dutch: ''Atrecht'') ...

region of northern France were first described as ''

Zosterophyllum ''Zosterophyllum'' was a genus of Silurian- Devonian vascular land plants with naked branching axes on which usually kidney-shaped sporangia were arranged in lateral positions. It is the type genus for the group known as zosterophylls, thought ...

artesianum'', but a later review by Edwards showed that they did not fit the

circumscription Circumscription may refer to: *Circumscribed circle * Circumscription (logic) *Circumscription (taxonomy) *Circumscription theory, a theory about the origins of the political state in the history of human evolution proposed by the American anthrop ...

of that genus.

Description

Compressed fossils were found in the

region of northern France, in rocks which were originally thought to be of

Pragian The Pragian is one of three faunal stages in the Early Devonian Epoch. It lasted from 410.8 ± 2.8 million years ago to 407.6 ± 2.8 million years ago. It was preceded by the Lochkovian Stage and followed by the Emsian Stage. The most important La ...

age (around ) but more recently have been considered to be probably of

Emsian The Emsian is one of three faunal stages in the Early Devonian Epoch. It lasted from 407.6 ± 2.6 million years ago to 393.3 ± 1.2 million years ago. It was preceded by the Pragian Stage and followed by the Eifelian Stage. It is named after the ...

origin (around ). Plants consisted of smooth leafless stems (axes) up to 1.5 mm wide and were at least 85 mm high. They branched at right angles. Spore-forming organs or

sporangia A sporangium (; from Late Latin, ) is an enclosure in which spores are formed. It can be composed of a single cell or can be multicellular. Virtually all plants, fungi, and many other lineages form sporangia at some point in their life cyc ...

were borne on all sides, spaced irregularly on stalks up to 3 mm long which held them horizontally, and not forming a distinct 'spike'. Individual sporangia were elliptical in shape, around 3 mm wide by 2 mm high, splitting into two 'valves' along a line opposite to the stalks in order to release their spores. Since the sporangia were at right angles to the stem, the split was vertical.

Taxonomy

Specimens were first attributed to ''

'' cf. ''myretonianum'' by Corsin in 1933. In 1956 Danzé-Corsin constructed a new species, ''Z. artesianum'' to accommodate this plant, arguing that it resembled ''Z. llanoveranum'' but had its sporangia arranged in a much laxer spike. Edwards notes that since then, reviews of the genus ''Zosterophyllum'' have clarified its circumscription. All species of ''Zosterophyllum'' have a compact spike of sporangia, arranged helically with some degree of regularity. The sporangia are bivalved as in this plant, but they have short stalks which turn upwards, so that the sporangia are vertically aligned and hence split (dehisce) along a horizontal line. No other genera within the

zosterophyll The zosterophylls are a group of extinct land plants that first appeared in the Silurian period. The taxon was first established by Banks in 1968 as the subdivision Zosterophyllophytina; they have since also been treated as the division Zosteroph ...

s has the features of the French specimens, so that Edwards assigned them to a new genus, ''Danziella'', named after Danzé-Corsin.

Phylogeny

Edwards considers the placement of ''Danziella'' to be uncertain. It has a simpler organization than most of the genera assigned to the

s, somewhat resembling taxa such as ''

Cooksonia ''Cooksonia'' is an extinct group of primitive land plants, treated as a genus, although probably not monophyletic. The earliest ''Cooksonia'' date from the middle of the Silurian (the Wenlock epoch); the group continued to be an important comp ...

caledonica'' and ''

Renalia ''Renalia'' is a genus of extinct vascular plants from the Early Devonian (around ). It was first described in 1976 from compressed fossils in the Battery Point Formation (Gaspé, Québec, Canada). It is difficult to reconstruct the original for ...

''. ''Renalia'' is placed outside the zosterophylls as one of a set of sister taxa in the

cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to d ...

for the

polysporangiophyte Polysporangiophytes, also called polysporangiates or formally Polysporangiophyta, are plants in which the spore-bearing generation (sporophyte) has branching stems (axes) that bear sporangia. The name literally means 'many sporangia plant'. The cl ...

s which Crane et al. published in 2004. Edwards agrees that ''Danziella'' may be part of the stem group of the zosterophylls and hence the lycophyte clade, but says that it could also belong elsewhere and show convergent evolution of the mechanism by which the sporangia split to release spores. Hao and Xue in 2013 listed the genus as a zosterophyll.

References

{{Taxonbar, from=Q5221467 Early Devonian plants Emsian life Pragian life Zosterophylls Prehistoric lycophyte genera