Raymondcia rigida, (LORENZ, 1886)

Lombardi, Chiara, Taylor, Paul D. & Cocito, Silvia, 2010, Systematics of the Miocene-Recent bryozoan genus Pentapora (Cheilostomata), Zoological Journal of the Linnean Society 160 (1), pp. 17-39 : 33-34

RAYMONDCIA RIGIDA ( LORENZ, 1886) ( FIG. 12 )

Smittina rigida: Lorenz, 1886: 91 , figs 8, 8a.

Pentapora boreale: Kuklinski & Hayward, 2004: 81 , fig. 1a, c.

Raymondcia rigida: Grischenko, Dick & Mawatari, 2007: 1108 , fig. 24.

Material: NHM 2003.3.10.1, holotype of P. boreale, Kongsfjorden, Spitsbergen , 79°03.51 ′ N, 11°34.4 ′ E, Kuklinski Collection. NHM 2003.3.10.2-6, paratypes of P. boreale, Kongsfjorden, Spitsbergen , 79°01.8 ′ N, 11°49.8 ′ E, Kuklinski Collection.

Brief description: Colony encrusting, unilaminar.

Autozooids hexagonal, boundaries well defined, averaging 0.58 ± 0.03 mm long by 0.41 ± 0.04 mm wide ( Kuklinski & Hayward, 2004). Frontal shield convex, granular, a pronounced conical umbo proximal of the orifice; areolar pores and pseudopores large. Primary orifice as wide as long, 0.15 ± 0.02 mm long by 0.16 ± 0.01 mm wide; condyles and oral spines lacking; lyrula broad. Ovicells hyperstomial, imperforate, slightly wider than long, averaging 0.18 ± 0.02 mm long by 0.25 ± 0.03 mm wide, becoming overgrown by granular calcification extending proximally from distal zooid ( Kuklinski & Hayward, 2004). Lateral and transverse walls bearing multiporous septula. Median septum lacking on basal wall.

Avicularia monomorphic, suboral, lying below the lyrula, proximally directed, small; rostrum rounded, spatulate; crossbar uncalcified apart from short condyles.

Remarks: Restudy of the holotype and paratypes of P. boreale from Kongsfjorden, West Spitsbergen, show this species to belong to another genus, Raymondcia , and to be a junior synonym of R. rigida ( Lorenz, 1886) , which was comprehensibly redescribed recently by Grischenko et al. (2007). The most important feature of ‘ P. boreale ’ that enables it to be excluded from Pentapora is the presence of a lyrula ( Fig. 12C, D ). Because of its location deep within the orifice, the lyrula was apparently missed by Kuklinski & Hayward (2004) when they originally described the species. Furthermore, the species lacks two features found in Pentapora : a porous ectooecium and orificial condyles (the ‘minute and rounded condyles’ noted by Kulinski & Hayward were not evident when the material was restudied using SEM).

PHYLOGENETIC ANALYSIS

The phylogenetic analysis was undertaken using the program PAUP 4.0. A matrix of 20 characters, nine qualitative and 11 quantitative, was assembled for the six species of Pentapora that we have accepted (see the Appendix). Five of these characters are multistate, the remainder are binary. Gap analysis was used to determine character states for quantitative characters. Among the quantitative characters, three are ratios similar to those successfully used for bryozoan phylogenetics (e.g. Cheetham et al., 2006).

Out-group selection is problematical in Pentapora because there is no phylogenetic analysis available for the family ( Bitectoporidae ) to which the genus belongs, and the genera assigned to this family are too morphologically variable to provide a clear indication of character polarization. Similar variability is evident in the closely related Smittinidae , making this also difficult to use as an out-group. Therefore, we have reluctantly chosen to root the tree on an in-group taxon: P. ottomulleriana . This species was selected because it exhibits character states considered to be primitive for Pentapora , including an entirely encrusting colony form, lack of median septa, monomorphic avicularia, and oral spine bases.

The exhaustive search algorithm of PAUP yielded a single most parsimonius tree of 29 steps; the next shortest trees (three) had 31 steps. Of the 20 characters employed, 11 were found to be parsimony informative. The shortest tree ( Fig. 13 ) had a consistency index (CI) of 0.862, a retention index (RI) of 0.667, and a rescaled consistency index ( RC) of 0.575.

Three species, the extant P. foliacea plus the Pliocene species P. pertusa and P. lacryma sp. nov., form a clade in which P. foliacea and P. pertusa are sister species. Outside this essentially Atlantic clade are the Mediterranean species: the Pliocene–recent P. fascialis and the Pliocene P. clipeus sp. nov. Bootstrap support values for the clades range from 69 to 86, based on a heuristic search of 1000 replicates.

Although the phylogeny is concordant with the biogeography, with the more basal species living in the Mediterranean and the crownward species in the Atlantic, many of the synapomorphies supporting the major clades are quantitative characters that may be suspect in view of the known plasticity of such characters in bryozoans related to factors such as seawater temperature and nutrient levels (e.g. Okamura, 1987; Lombardi et al., 2006).

The oldest fossil occurrence of Pentapora appears to be from the Upper Miocene (Messinian) of Morocco. Material from Morocco was identified by El Hajjaji (1992) as P. pertusa , but the lack of giant avicularia or uniporous ovicells means that El Hajjaji’s specimens must be left in open nomenclature as Pentapora sp. From a stratigraphical standpoint, the relatively short range of Pentapora (less than 4 million years for the identifiable species) means that testing the phylogeny against the fossil record is of doubtful value.

The separation of P. fascialis and P. foliacea on the cladogram by the Pliocene P. lacryma sp. nov. is notable, in view of the debate about whether these two extant species are synonyms. If synonymous, they would be expected to come out as sister species. Indeed, the sister species of P. foliacea is inferred to be the Pliocene P. pertusa that, although similar in autozooidal morphology, has uniquely uniporous ovicells and an enormous triangular giant avicularium. The only species of Pentapora to have lost the giant avicularia is P. foliacea , assuming that the monomorphic avicularia of P. ottomulleriana are correctly classified as giant avicularia, as suggested by their size and horizontal inclination. Dimorphism of avicularia into normal and giant types apparently occurred immediately crownward of P. ottomulleriana , with all subsequent species retaining dimorphic avicularia, apart from P. foliacea .

Figures

Figure 12. Raymondcia rigida (Lorenz, 1886), holotype of Pentapora boreale Kuklinski & Hayward (2004), Kingsfjorden, Spitsbergen, NHM 2003.3.10.1; scanning electron micrographs of uncoated specimen imaged using back-scattered electrons. A, zooids and growing edge. B, zooids with ovicells and suboral avicularia. C, primary orifice, nonporous ovicell, suboral avicularium and lyrula. D, primary orifice, suboral avicularium and ovicell overgrown by granular calcification. Scale bars: A = 600 Mm; B = 200 Mm; C = 80 Mm; D = 100 Mm.

Figure 13. Cladogram showing the inferred phylogenetic relationships between species of Pentapora based on an analysis rooted on Pentapora ottomulleriana. The numbers in the squares are bootstrap support values for clades along the spine of the tree. Smaller figures are character numbers (see the Appendix), with state changes given in brackets. Extinct species are indicated with asterisks. Note that the Atlantic species form a clade crownward of the Mediterranean species in this analysis.