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= Weltrichia =

Weltrichia is an extinct genus of a plant belonging to Bennettitales, an order of gymnosperms widespread during the Mesozoic. Weltrichia belongs to the Williamsoniacea family, characterized by plants with unisexual reproductive structures (male: Weltrichia, female: Williamsonia) and bisexual reproductive structures (Williamsoniella).

The genus Weltrichia includes 25 species that have been recognized thanks to the fossil remains found in both hemispheres. Unfortunately, there is no complete reconstruction and the fossil material is scarce. The taxonomy of this genus is therefore difficult and uncertain.

Discovery and naming
Genus Weltrichia was defined by Braun in 1849 with the type species Weltrichia mirabilis found in the Jurassic sediments of Franconia, Germany.

He took the name from Johann P. A. Weltrich, first discoverer and collector of these plant fossil remains, even if he originally interpreted it incorrectly (family Rafflesciaceae).

The Weltrichia name was not widely used at first because this reproductive structure was referred to as "male Williamsonia", for the resemblance to the female reproductive structures of the Bennettitalean Williamsonia Carruthers 1870.

This discussion of the relationship between Weltrichia and Williamsonia and their nomenclature has been carried on with subsequent discoveries of new genera by Harris (1969), Sitholey and Bose (1971) , Schweitzer and Kirchner (2003) and Popa (2014,2019).

We don’t have many fossils finds because the preservation of these species is very rare. These structures can be easily destroyed and dismembered by mechanical and biotic factors. In fact, the centripetal rays and the pollen sacs, which are very thin and fragile, are very rarely preserved.

Fossils have been found in both hemispheres but especially in Europe.

The stratigraphic ranges of Weltrichia species vary from Late Triassic ( earliest representative is Weltrichia alpina) to Late Jurassic (latest representatives  W. maldaensis and W. huangbanjigouensis).

Records during the Triassic are scarce and generally incomplete, those of the Jurassic are better preserved. Reconstructions of whole plants are still difficult to prove. The low number for each species limits the observation of intraspecific variability.



Description
The genus Weltrichia belongs to the order Bennettitales characterized by having as reproductive structures of the gymnosperm cones that are similar to flowers.

In particular, Weltrichia has a radial symmetry and it’s characterized by a central cup from which depart centrifugal rays which are radially equal. These rays bear the synangia (pollen sacs) with monocolpate pollen. Over the cup there are centripetal rays.

There are many structural variations in the Weltrichia species that depend mainly on cup morphology and the number and shape of rays. The main variations are :

· The substance of the central cup and rays may be thin (e.g. Weltrichia ayuquiliana), moderately thick (e.g. W. antonii), or thick (e.g. W. alfredii).

·The cup may appear as the result of the lateral fusion of the rays or looks complete

· The centrifugal rays can be short (Weltrichia ayuquiliana), strongly elongated (W. spectabilis), flattened (W. whitbiensis), rhombic in cross-section (W. givulescui), or spatulated (W. Setosa).

· The shape of the rays can be triangular-elongated (W. alfredii), extremely elongated (W. spectabilis), or reach their maximal width towards their median part (W. harrisiana, W. maldaensis)

Due to the scarcity of the fossil record of Weltrichia species, it is difficult to understand the number of centripetal and centrifugal rays but considering the studied material, the number is constant.

Classification
It’s difficult to define Weltrichia taxonomically because of the scarcity of fossil material, in fact, some species are represented only by their holotype.

Weltrichia belongs to Bennettitales, that in cladistic studies are directly related to Gnetales and Angiosperms. The Bennettitales order is divided into two separate families: Williamsoniaceae (Late Triasic and Jurassic) and Cycadeoidacee (Cretaceous).

The genus Weltrichia includes 25 species.

On the right there is a cladogram based on the phylogeny of Doyle (2006) :

Paleoecology
By analyzing the different species of Weltrichia, two different strategies of pollination have been identified: pollination through the wind or through insects.

The strategy is difficult to prove due to the scarcity of fossil records. But we can assume:


 * Pollination of the wind: because Weltrichia has very similar characteristics to the male structure bennettitalea Lunzia austriaca (Krasser 1917)  of which the strategy is known. It is also understood by the position of the pollen bags on the surface of the rays which turns out to be an excellent position for dispersing the pollen using the air flows.

The co-evolution with insects, especially with the cupedid group, may explain the remarkable variability of the genus Weltrichia, related to species of pollinators and pointing to specialized collaborations between bennettitaleans and insect species already occurring in the Late Triassic and the Early Jurassic.
 * Pollination through the insect: there is strong and growing evidence of this interaction, especially thanks to traces of herbivores, oviposition and larvae within fertile structures  . The pollination of this genus is attributed to the cupedid beetles, which diversify during the Triassic. This interaction can be observed from the attractive resin bodies in the central cup of Weltrichia (e.g., W. alfredii, W. givulescui and W. whitbiensis) which represent an evolved character in relation to the pollination of insects to attract them. There is evidence of adaptations with repellent effect for predatory insects (especially beetles and cupedids) such as the thick substance of Weltrichia structures and their woody nature in some species or the centripetal rays covering the central cup.

Species
The genus Weltrichia includes 25 species that have been recognized thanks to the fossil remains found in both hemispheres :


 * Weltrichia alfredii (Krasser) Popa 2014


 * Weltrichia alpina Krasser 1919
 * Weltrichia antonii Popa 2014
 * Weltrihcia ayuquiliana Delevoryas 1991
 * Weltrichia daohugouensis Lil at al. 2004
 * Weltrichia fabrei Saporta 1891
 * Weltrichia givulescui Popa 2001
 * Weltrichia harrisiana Bose et Banerji 1984
 * Weltrichia hirsute Schweitzer 1977
 * Weltrichia huangbanjingouensis Sun et al. 2001
 * Weltrichia johannae Popa 2014
 * Weltrichia maldaensis Pal et Ghosh 1985
 * Weltrichia microdigitata Delevoryas 1991
 * Weltrichia mirabilis Braun 1849
 * Weltrichia mixtequensis Silva Pineda et al. 2011
 * Weltrichia oolithica Saporta 1891
 * Weltrichia pecten (Leckenby) Harris 1969
 * Weltrichia primaeva Schweitzer et Kirchner 2003
 * Weltrichia santalensis (Sitholey et Bose) Harris 1969
 * Weltrichia setosa (Nathorst) Harris 1969
 * Weltrichia sol Harris 1969
 * Weltrichia sp. (sp. nov.?)
 * Weltrichia spectabilis (Nathorst) Harris 1969
 * Weltrichia steierdorfensis Popa 2014
 * Weltrichia whitbiensis (Nathorst) Harris 1969