Family PORICELLARIIDAE Harmer, 1926

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Introduction

The family Poricellariidae was introduced for a single genus, Poricellaria d'Orbigny (1852), who described Tertiary European species. Both Harmer (1926) and Ryland (1982) have discussed the relationships of the family. Cheetham (1968, 1973) used analyses of the morphometrics of Poricellaria and other genera to illustrate a postulated evolutionary sequence derived from the genus Nellia, as discussed by Winston & Cheetham (1984).

Only one Recent species, P. ratoniensis, is known from shallow water in the Indo-West Pacific. Colonies are small, erect and dichotomously branched. They arise from a series of erect kenozooids and are anchored by rhizoids, which may themselves give rise to a further kenozooid series. Zooids are asymmetrical and are curved to face one side of the branch only. The alternating paired frontal series are curved towards the mid-line; the paired basal series are more strongly curved to face frontally. Zooids have a well-developed cryptocyst lamina with a single slit-like opesiule. Avicularia occur on the proximal gymnocyst of each zooid. They have a large subrostral chamber which covers the gymnocyst and a narrow, acute rostrum which is orientated towards the outer side of the branch in frontal zooids and towards the mid-line in basal zooids. Embryos are brooded in interior ovisacs (Waters 1913).

P. ratoniensis is known from Zanzibar and the East Indies (Harmer 1926). Ryland (1974) gave the first Australian record, from the underside of rocks near Townsville, Queensland. The colonies formed a turf, accompanied by other species with a similar colony form, such as Nellia oculata, and were inhabited by numerous pycnogonids, which may have been feeding on the bryozoans. Further information is given by Ryland (1984; 1993).

P. ratoniensis is capable of living in conditions of very high temperature (29°C) and salinity (56.7‰), according to Lagaaij & Cook (1973). The genus is known from the Late Cretaceous of Jamaica, and the Tertiary of Central and North America, Europe and the Indo-West Pacific (Cheetham 1973; Lagaaij & Cook 1973).

Diagnosis

Colony small, erect, nodal, lightly calcified, anchored by rhizoids. Internodes alternating with cuticular joints. Autozooids biserial, asymmetrical, curved to face one side of the branch. Zooids with well developed cryptocyst and one opesiule. Brooding in interior ovisacs.

General References

Cheetham, A.H. 1968. Evolution of zooecial asymmetry and origin of poricellariid cheilostomes. Atti della Società Italiana di Scienze Naturali e del Museo Civico di Storia Naturale di Milano 108: 185-194

Harmer, S.F. 1926. The Polyzoa of the Siboga Expedition. Part 2. Cheilostomata Anasca. Siboga-Expéditie Report 28B: 183-501

Lagaaij, R., & Cook, P.L. 1973. Some Tertiary to Recent Bryozoa. pp. 489-498 in Hallam, A. (ed.). Atlas of Palaeobiogeography. Amsterdam : Elsevier.

Ryland, J.S. 1974. Bryozoa in the Great Barrier Reef Province. Proceedings of the 2nd International Coral Reef Symposium 1: 341-348

Ryland, J.S. 1982. Bryozoa. pp. 743-769 in Parker, S.P. (ed.). Synopsis and classification of living organisms. New York : McGraw-Hill.

Ryland, J.S. 1984. Phylum Bryozoa. pp. 68-75 in Mather, P. & Bennett, I. (eds). A Coral Reef Handbook. Brisbane : The Australian Coral Reef Society.

Ryland, J.S. 1993. Phylum Bryozoa - Lace corals and other moss animals. pp. 141-156 in Mather, P., & Bennett, I. (eds). A Coral Reef Handbook. Chipping Norton, NSW : Surrey Beatty & Sons.

Winston, J.E., & Cheetham, A.H. 1984. The Bryozoan Nellia tenella as a living fossil. pp. 257-265 in Eldredge, N., & Stanley, S. (eds). Living Fossils. New York : Springer Verlag.

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