Figure 1.
Dendrogramma gen. nov., all 15 paratypes of D. enigmatica and (with *) D. discoides.
Photographs taken after shrinkage (see Material and Methods).
Figure 2.
Dendrogramma enigmatica sp. n., A, holotype, ‘lateral’ view. B, same, aboral view.
C, cross-section through approx. half of stalk (level indicated by arrow heads in Fig. 2A) showing gastrovascular canal in centre (pharynx), mouth-field lobe with thickened epidermis, and main systems of fibrils in mesoglea. D, enlargement of mouth-field lobe. Drawings made before shrinkage.
Figure 3.
Dendrogramma enigmatica sp. nov., holotype.
A, B, lateral views; C, aboral view, D, adoral view. Photographs taken after shrinkage.
Figure 4.
Dendrogramma enigmatica sp. nov., paratype.
A, B, lateral views; C, adoral view; D, close-up of disc surface; E, aboral view; F, tip of stalk; G, aboral view of notch of disc surface. SEM micrographs made after shrinkage.
Figure 5.
Dendrogramma enigmatica sp. nov., paratype, same specimen as in figure 4 after cutting away part of stalk and disc;
A, lateral view. B, radial-section of disc; C, radial-section of disc in light microscopy before sputter coating for SEM. D,E, cross-sections of gastrovascular branches in disc. F, epidermis of disc. G, cross-section of stalk. H, cross-section of gastrovascular canal of stalk (pharynx). I, gastrodermis of gastrovascular canal (pharynx) of stalk. J, epidermis of stalk. SEM micrographs made after shrinkage.
Figure 6.
Dendrogramma discoides gen. et sp. n., A, holotype, aboral view.
B, enlargement of A showing gastrovascular canal (stippled) of stalk (pharynx) and point of connection to the first branching node of gastrovascular system of the disc. C, paratype, oblique oral view of trilobed mouth-field with mouth opening in centre; entire pharyngeal part of the gastrovascular system is shown. D, Albumares with trilobed field (reproduced from [19]). E, Rugoconites tenuirugosus (reproduced from [19]). F, 1. Albumares brunsae, 2. Anfesta stankovskii, 3. Rugoconites enigmaticus; (all three from [23]; sizes: see text in Discussion). Drawings of Dendrogramma made before shrinkage.
Figure 7.
Dendrogramma discoides gen. et sp. n., various aspects of holotype.
A, adoral view. B, enlarged part of disc; C, aboral view; D, oblique adoral view. Photographs taken after shrinkage.
Figure 8.
Possible positions of Dendrogramma in a simplified phylogeny showing the deepest splits in the metazoan Tree of Life.
The position of Ctenophora is controversial so two possibilities have been shown with dashed lines, one as sister group to the remaining metazoans (the ‘Ctenophora-first’ hypothesis), and one as sister group to Cnidaria (Coelenterata hypothesis) (based on [6], [7], [8], [24], [25]. We suggest that Dendrogramma most likely is related to Ctenophora and/Cnidaria (red arrows) due to general similarities in body organisation (see Discussion). However, depending on the position of Ctenophora and on whether certain aspects of Dendrogramma (e.g., mesoglea and gastrovascular system) are ancestral for Metazoa or modified, Dendrogramma can be positioned in a variety of ways below Bilateria (yellow oval).