Zosterophyllophyta

Zosterophyllophyta
Fossils of Zosterophyllum , on the left a curled end of the shoot, on the right a shoot with a sporangium
Temporal occurrence
Lower Devonian ( Lochkovian ) to Lower Carboniferous ( Tournaisian )
416 to 345 million years
Systematics
without rank: Chloroplastida without rank: Charophyta without rank: Phragmoplastophyta without rank: Streptophyta Empire : Plants (Plantae) Department : Zosterophyllophyta
Scientific name
Zosterophyllophyta

Reconstruction of Distichophytum = Rebuchia

Model of Zosterophyllum

Sawdonia ornata fossil

The Zosterophyllophyta are a group of extinct plants that were mainly found in the Devonian . They occupy an intermediate position between the basal vascular plants, the Rhyniophyta , and the bear moss plants .

features

Most representatives are forked (dichotomously) branched. Some genera also show pseudo monopodial branching. The conductive tissue in the axis forms a protostele . It is always exarch, that is, the protoxylem is on the outside and the stele matures from the outside inwards. The shape of the xylem cord is often elliptical in cross section.

The most important distinguishing feature from the other primitive vascular plants is the position of the sporangia : they stand laterally along the stem axis or are attached to the stem axis by a short branch. In many species the sporangia are huddled at the terminal areas of the axes. The shape of the sporangia ranges from spherical to kidney-shaped. The opening is usually along the distal side, with the sporangium cracking open in half. Zosterophyllum deciduum appears to have shed the sporangia upon maturity. The Zosterophyllophyta were probably homosporous, although the size of the spores can vary widely. In Barinophyton and Pseudobarinophyton , a sporangium contains large and small spores.

Systematics

The zosterophyllophyta were established by Harlan P. Banks when he realized that the psilophytes are an extremely heterogeneous group. When dividing the psilophytes, he formed the zosterophyllophyta, which in 1992 had the following size:

• Zosterophyllophytina
  • Zosterophyllaceae
    • "Terminal standing sporangia"
      • Zosterophyllum
      • Rebuchia (= Bucheria)
      • Gumuia
    • "Not terminal, bilateral"
      • Sawdonia
      • Gosslingia
      • Crenaticaulis
      • Bathurstia
      • Serrulacaulis
      • Oricilla
      • Konioria
      • Margophyton
      • Tarella
      • Anisophyton
      • Thrinkophyton
      • Discalis
      • Deheubarthia
• incertae sedis within Zosterophyllophyta
  • Barinophytales
    • Barinophytaceae
      • Barinophyton
      • Pectinophyton
      • Protobarinophyton
      • Barinostrobus
• incertae sedis within plants
  • Hsua
  • Nothia
  • Hicklingia
  • Huia

Based on cladistic analyzes, Kenrick and Crane established the following cladogram of the basal branches of the clade leading to the lycophytes:

Zosterophyllopsida   Sawdoniales   Sawdoniaceae  Anisophyton     Konioria     Crenaticaulis     Serrulacaulis     Deheubarthia     Sawdonia     Thrinkophyton  Barinophytaceae  Barinophyton citrulliforme     Barinophyton obscurum     Protobarinophyton  Hsuaceceae  Hsua  Gosslingiaceae  Gosslingia     Oricilla     Tarella     Zosterophyllum divaricatum     Zosterophyllum fertile     Zosterophyllum llanoveranum     Rebuchia     Discalis     Zosterophyllum deciduum  Lycopodiopsida  Huperzia     Asteroxylon     Baragwanathia     Drepanophycus     Nothia     Adoketophyton     Zosterophyllum myrtonianum     Gumuia     Huia     Hicklingia

According to these results, the zosterophyllophyta are paraphyletic in relation to the bear moss plants (Lycopodiopsida). Kenrick and Crane have therefore restricted the definition of Zosterophyllophyta and also made this clear by changing the name to Zosterophyllopsida.

Zosterophyllopsida

The Zosterophyllopsida are the group of extinct bear moss-like plants redefined by Kenrick and Crane, which were mainly represented in the Devonian . The growth takes place with rolled up (circinate) shoot tips, similar to what happens with ferns. The sporangia are arranged in two rows on the side of the shoot axes. The xylem in the axial vascular bundle is elliptical in cross-section, but this may also apply to the more basal representatives of the lycophytes.

The Zosterophyllopsida include the diverse group of Dawsoniales and some types of Zosterophyllum and possibly Rebuchia and Discalis .

The Sawdoniales represent the majority of the species . Basal representatives of the Zosterophyllopsida, which are not counted among the Dawsoniales, are Rebuchia , Discalis , as well as Zosterophyllum divaricatum , Zosterophyllum fertile and Zosterophyllum llanoveranum .

Temporal spread

The first fossils that can be clearly assigned to the zosterophyllophyta ( Zosterophyllum , Drepanophycus ) come from the Lochkovian , which began around 416 million years ago. The dating of some finds in the Upper Silurian ( Ludlow ) using graptolites is not generally recognized. They reached their greatest diversity in the early Devonian.

The latest finds are those of Protobarinophyton from the Tournaisian , the lowest stage of the Carboniferous, which ended 345 million years ago.

supporting documents

• Paul Kenrick, Peter R. Crane: The Origin and Early Diversification of Land Plants. A Cladistic Study . Smithsonian Institution Press, Washington DC 1997, ISBN 1-56098-729-4
• Thomas N. Taylor, Edith L. Taylor: The Biology and Evolution of Fossil Plants . Prentice Hall, Englewood Cliffs 1993, pp. 203-216, ISBN 0-13-651589-4

Individual evidence

1. ↑ Kenrick, Crane: The Origin and Early Diversification of Land Plants. A Cladistic Study , 1997, Table 5.2.
2. ↑ Kenrick, Crane: The Origin and Early Diversification of Land Plants. A Cladistic Study , 1997, part of Fig.5.26.

Web links

Commons : Zosterophyllophyta  - Collection of images, videos and audio files