Ernst et al.—New caledonian Triassic bryozoan
problematica (Campbell and Grant-Mackie, 1984). No internal zonation has been established for the Oretian Stage so it is not possible at present to be sure how much of Oretian time is represented by this formation or at what level within the stage the bryozoan-bearing locality lies. The Ouamoui Formation has Manticula problematica in its
basal beds, underlies strata with the Warepan Stage indicator Monotis, and includes a variety of taxa restricted to the Otamitan Stage. The Leprédour Shellbeds constitute essentially the range-
zone of Monotis and are thus of Warepan age, with no indicators of younger strata present. As noted above, bryozoan-bearing Warepan localities can be allocated to the Discordans, Gigantea, and Calvata Zones of Campbell and Grant-Mackie (1984) (Fig. 5). The Bouraké Formation has been shown by both Pharo
(1967) and Campbell and Grant-Mackie (1984) to cross the Triassic-Jurassic boundary. The bryozoans discussed here have all been recovered from the Triassic portion, below strata con- taining the Early Jurassic indicators Otapiria marshalli Trech- mann and Mentzelia ongleyi Marwick. On Ile Leprédour Pharo (1967) reported Monotis (Maorimonotis) calvata Marwick and other forms of Monotis in the lowest 20m of the formation and regarded it as therefore being Warepan in its lower part. Sub- sequent fieldwork has demonstrated for Iles Hugon and Ducos that specimens of this species from above the angular uncon- formity at the base of the Bouraké Formation have been derived from the underlying Leprédour Shellbeds and that the formation is Otapirian at its base. Some specimens of M. calvata retain matrix within the
umbo that is different from that of the enclosing rock. A speci- men from f795 on île Leprédour shows a 5-mm-thick mudstone apical filling in an enclosing matrix of coarse sand and shell debris. Another, from f109 on île Hugon, has mud between two nested valves that is darker brown than that of the host rock. Other examples are much less clear-cut in their evidence: many valves contain matrix indistinguishable from the rest of the rock, and, if reworked, have been fully disinterred without significant breakage, but the matrix does contain much fragmented shell material that could be interpreted, although not unequivocally, as being from valves that were broken during disinterment. Derivation is also demonstrated by the partial steinkern of a moderate-sized (>30mmdiameter) gastropod (?pleurotomariid) in f7, île Hugon, which consists of buff-colored lutite quite distinct from the enclosing medium brown coarse sandstone, but similar to the matrix of some strata of the Leprédour Shellbed and to that of the above valve from f795. Careful re-examination of Pharo’s other specimens indicates
that they alsowere probably derived fromthe underlying beds and that the base of the Bouraké Formation on Ile Leprédour is of Otapirian
age.Despite there being depositional continuity here, no collection from the Bouraké Formation includes any indication of an older age. On Ile Ducos,where there are also sections showing conformity between the Leprédour Shellbeds and Bouraké Formation (Fig. 1), no collection from the base of the Bouraké Formation in these sections contains either derived Monotis specimens or any indicators of Warepan age. An Otapirian age is further indicated by the presence in the bryozoan-bearing strata on all three main islands of the bivalve Torastarte bensoni
735
Marwick, which in New Zealand is confined to rocks of the Otapirian Stage (Marwick, 1953). Within the Otapirian Stage Campbell (1956) recognized a
basal Otapirian fauna, without any formal designation of a basal zone. Members of that fauna include the stage marker Rastelligera diomedea, the additional brachiopods Sakawairhynchia hugonensis MacFarlan and Fissirhynchia pacifica MacFarlan, and the bivalves Antiquilima sp. and Minetrigonia otapiriensis Fleming, most of which also occur in many of those bryozoan-bearing faunas of the Bouraké Formation. MacFarlan (1992) noted also that Sakairhynchia harihariensis Macfarlan, which is recorded in f503, is confined to the early Otapirian, although not being known from the basal beds of that stage. Campbell (1956) also recognized an upper Otapirian fauna characterized by Otapiria dissimilis (Cox) and Mentzelia kawhiana Trechmann, which have been found in association with the Bouraké Bryozoa in f111. We can confidently assert that bryozoans from the Bouraké Formation are therefore of early Otapirian age, with the exception of that in f111, which is late Otapirian. Thus we conclude that Bryozoa have been recovered from
the New Caledonian Triassic in rocks of Oretian, possibly Middle Otamitan, Middle and Late Warepan and Otapirian ages, i.e., in rocks correlated with four levels in the Norian and two in the Rhaetian.
Previous work
Bryozoans have previously been recorded without further identification in many earlier field reports (e.g., Avias, 1953; Pharo, 1967; Paris, 1981; Campbell et al., 1985). Some of these records refer to “Monotrypella maorica” Wilckens (1927), which was originally described from the New Zealand Triassic and thought to be a bryozoan, but has since been interpreted by Schäfer and Grant-Mackie (1998) as a tabulate coral and transferred to the genus Eoheteropora Morozova in Morozova and Zharnikova, 1984. Until now, no other attempt has been made to taxonomically determine these bryozoan remains.
Systematic paleontology
Phylum Bryozoa Ehrenberg, 1831 Class Stenolaemata Borg, 1926 Order Trepostomata Ulrich, 1882
Family Stenoporidae Waagen and Wentzel, 1886 Genus Metastenodiscus new genus
Type species.—Stenodiscus zealandicus Schäfer and Grant-Mackie, 1994. Upper Triassic; New Zealand.
Diagnosis.—Massive or encrusting colonies with short endozones. Apertures rounded or oval. Autozooecial walls thin in the endozone; laminated, fused without autozooecial bound- aries, irregularly (monilaeform) thickened in the exozone. Diaphragms thin, complete, usually abundant. Cystiphragms present. Heterozooecia usually rare, sometimes common, with diaphragms. Acanthostyles abundant, usually varying in size.
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