Family SMITTINIDAE Levinsen, 1909

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Family SMITTINIDAE Levinsen, 1909

Compiler and date details

July 2001 - Dr Philip Bock

Introduction

The family Smittinidae was introduced by Levinsen (1909) and forms another very large grouping which traditionally includes genera which have a very wide range of character correlations. More than 30 genera have been assigned to the family, many, but not all of which, have in common a tooth protruding from the proximal edge of the primary orifice. This tooth, termed a lyrula, is frontal in position to the operculum, whereas the accompanying paired lateral condyles are beneath the operculum (Soule & Soule 1973). Presumably the lyrula protects the opening into the ascus, much as do the proximal denticles of the Petraliellidae. The frontal shield may have numerous pseudopores, or may be imperforate centrally, but has marginal frontal septular pores, often extended frontally as areolae. Oral spines may be present or absent. Avicularia are usually present, and may be suboral or lateral, and are sometimes greatly enlarged. Ovicells are hyperstomial and the ectooecium and entooecium are alike pierced by pores. Sometimes the ectooecium is raised to form a margin surrounding the entooecium. This ovicell structure is in contrast to the Schizoporellidae, where the ectooecium is membranous. Gordon (1994) considered the ovicell characteristics of such importance that he grouped all the Smittinidae together with the Bitectiporidae in one superfamily, the Smittinoidea. Preliminary studies of frontal shield development indicates that lepralioid development is characteristic of groups with a porous frontal shield (e.g. Smittina), while umbonuloid development may be present in at least three closely related genera with a centrally imperforate frontal shield (Parasmittina, Hemismittoidea, and Pleurocodonellina) (D.P.Gordon, p.c.).

Soule & Soule (1973) have provided a preliminary analysis and revision of some Indo-Pacific smittinid groups, and Hayward & Parker (1994) have revised several Indo-Pacific records of widely distributed 'species' of Parasmittina. Whereas the majority of Australian smittinids have encrusting colonies, a significant number of species, particularly of Parasmittina, and many of the Antarctic forms, have large, erect tubular colonies, or grow in large unilaminar sheets of semi-erect and folded, anastomosing colony forms. Fourteen genera have either an Australian or Antarctic to subantarctic distribution.

The genus Smittina includes all species with a porous frontal shield, a lyrula and a median, suboral avicularium. The species recorded from Australia include S. cribraria (MacGillivray 1886), S. oculata (MacGillivray 1883), S. obscura (MacGillivray 1891), S. personata (Hincks 1884), S. protrusa Powell 1967 and S. papillifera (MacGillivray 1869). S. papillifera is found on the fronds of brown algae (Brown 1982); it has an atypical frontal wall morphology, with prominent tubercles, and may prove to belong to a new, or at least a different genus. Its larvae and early colony development were comprehensively described by Stach (1938). The local fauna needs complete revision, and more species are likely to be identified.

Hayward (1995) reported 13 species of Smittina from the Antarctic, and remarked that it was probable that others had yet to be described.

The genus Parasmittina has species with a zooidal frontal shield which has only marginal pores, a lyrula, and avicularia which are lateral and oral, or extremely large, covering the frontal shield of the autozooid. The genus is one of the most widely distributed, and is particularly common in warm, shallow waters. It is a well-known coral-associate, and Winston (1986) described 27 species from this type of habitat. Encrusting colonies develop multilaminar sheets by frontal budding. Hayward & Parker (1994) described 9 species of Parasmittina, four of which were new. Seven of these species had an Australian distribution, and three are endemic. P. delicatula is widely distributed from Hawaii to Japan, as well as from southern Australia to New Zealand. It was figured (as P. unispinosa) by Bock (1982). It forms both encrusting and large, bilaminar and tubular, erect and anastomosing multibranched colonies up to 100 mm in height. The widely distributed P. hastingsae was among the 6 species of Parasmittina described from the Great Barrier Reef by Hayward & Ryland (1995). It was the third commonest species on coral, and has multilaminar yellow colonies; it also occurs from Hawaii and Indonesia (Gordon 1984; Hayward & Parker 1994). Bock (1982) figured P. raigii from southern Australia, but the record needs reassessment in the light of the selection of a neotype by Hayward & Parker (1994).

The genus Smittoidea resembles Smittina, but the species have no pseudopores in the zooidal frontal walls. Gordon (1989) noted that S. maunganuiensis (Waters) was a senior synonym of S. acaroensis (Levinsen), which was figured by Bock (1982) from Victoria. Ryland & Hayward (1992) described S. pacifica Soule & Soule (1973) from the Great Barrier Reef, and Hayward (1995) described six species from Antarctica, four of which had erect unilaminar colonies.

The genus Pleurocodonellina was introduced by Soule & Soule (1973) and has species with marginal frontal pores only, and a proximo-lateral suboral avicularium. It includes the pan-tropical to subtropical P. signata, which does not have a proximal lyrula, but a sinus in the orifice margin. Ryland & Hayward (1992) and Hayward & Ryland (1995) have described P. signata and other, new species, from the Great Barrier Reef.

In the southern oceans a further 10 genera of Smittinidae have been reviewed by Hayward (1995). Many of the 15 species described have large colonies which are initially encrusting, but rise into unilaminar or bilaminar plates and anastomoses, sometimes exceeding 50 mm in height. Single expanses of Bostrychopora dentata may be larger than 10 cm2 (Hayward 1995).

Fossil smittinids are relatively common in the Tertiary sediments of southeastern Australia. Two of the genera, Smittinella and Hippomonavella, have Australian Tertiary type species, one of which, H. praeclara, was also reported from the Recent of South Australia by Wass & Yoo (1983). The earliest record of a smittinid genus was from the Early Eocene of the Pacific (Taylor 1993).

Diagnosis

Colony well calcified, encrusting, often multilaminar, with frontally budded layers, or erect, tubular, with unilaminar, anastomosing expansions. Zooids with lepralioid frontal shield, with or without pseudopores. Orifice usually with a proximal denticle (lyrula). Avicularia adventitious, often oral, sometimes greatly enlarged. Ovicells hyperstomial, with a porous entooecium and ectooecium, which may be raised forming a margin.