Metacladophyton tetraxylum

Name

Metacladophyton tetraxylum

Rank

Species

Generic Name

[Genus] Metacladophyton

Authors (Pub.)

Wang Zh. Geng B.-Y.  

Publication

A new Middle Devonian plant: Metacladophyton tetraxylum gen. et sp. nov. [1997/10]

Journal

Palaeontographica

Volume

243

Issue

4-6

Page number

93

Year

1997

Fossil Status

stems (with sporangia)

Stratigraphy

Givetian

Strat. comment

Yuntaiguan Formation

Location

Changyang County, Hubei Province, China

Paleoregion

Cathaysia (South)

Data for Holotypus

Repository

Institute of Botany, Chinese Academy of Sciences, Beijing, China

Repository Number

9167

Num

3: 1

Pub.

A new Middle Devonian plant: Metacladophyton tetraxylum gen. et sp. nov. [1997/10]

Diagnosis

Plant about 1.0 metre high. Nodose rhizome about 0.8 cm thick. 0.25 cm-thick roots attached to internodes of the rhizome. Aerial branching system arising from the rhizome nodes or as a continuation of the rhizome apex. Diameter of the stem about 7-15 mm. Node of stem with eight first branches in a whorled or near whorled sequence, interval between nodes about 7-11 cm. First order branches about 1-5 mm wide and over 18.5 cm long. Second order branches, about 1 mm wide and 9 cm long, opposite or near opposite on the first order branch. Dichotomous branchlets occasionally occurring on first order branches. Ultimate unit, about 12-19 mm high, over 0.8 mm thick at base and less 0.15 mm at tip, 4-8 times dichotomous with recurved tips. Arrangement of ultimate units on the second order branches, appearing as a linear sequence because the units curve upwards steeply, but occur in an alternate sequence. Fertile branching system similar to vegetative except for terminal, erect, paired sporangia. Sporangium, with a short stalk about 0.2 mm long, elliptical C. 0.75 mm by 0.36 mm, but over 1.4 mm by 0.6 mm when mature and longitudinally dehiscent. Spores, about 50 flm in diameter, trilete and of one size, with verrucate ornament. Dissected primary xylem group consisting of four V-shaped strands and eight arms. Each arm about 0.33-0.40 mm wide at its tip. Mesarch maturation. Protoxylem tracheids up to 25 I!m in diameter. Protoxylem lacunae or peripheral loops present. Metaxylem tracheids circular or elliptical about 25-80 I!m in diameter. Eight C-shaped traces departing respectively from eight arms in a whorled sequence, each one with a protoxylem group at its two ends. On branching, strands split and fuse and join together at the centre part of the vascular tissue. Secondary xylem tracheids, occurring in mature stem, elliptical, 30-60 I!m by 15-30 I!m. Bordered pits scalariform, elliptical and circular on all walls of metaxylem tracheids and secondary xylem tracheids. Weakly developed uniseriate rays with 1-6 cells high. Decussate pit apertures.