Monticulipora d’Orbigny, 1850

Jiménez-Sánchez, Andrea, 2010, New Monticuliporidae (Bryozoa, Trepostomata) from the Cystoid Limestone Formation (Upper Ordovician) of the Iberian Chains (NE Spain), Geodiversitas 32 (2), pp. 177-199 : 182-183

Genus Monticulipora d’Orbigny, 1850

TYPE SPECIES. — Monticulipora mammulata d’Orbigny, 1850 ; Upper Ordovician of Ohio .

EMENDED DIAGNOSIS. — Genus characterized by a massive growth habit formed by multiple layers, but frondescent or branching habits can be present; autozooecia with polygonal or subpolygonal apertures, less commonly subcircular; with simple cystiphragms larger in endozone than in inner exozone; autozooecial diaphragms join cystiphragms to the opposite wall; mesozooecia not abundant, located in autozooecial corners and monticules, and densely tabulated by diaphragms; acanthostyles mainly developed in exozone; monticules present and formed by mesozooecia and autozooecia larger than those in the intermonticular area.

DISCUSSION

Astrova (1978) characterized Monticulipora as having autozooecia with polygonal apertures, numerous cystiphragms and diaphragms in all autozooecia, few mesozooecia, presence of acanthostyles, and zooecial walls with granular microstructure. Ross (1967) had described Prasopora as having autozooecia with rounded or subpolygonal apertures, isolated and superimposed autozooecial diaphragms and cystiphragms, abundant closely spaced mesozooecia, and sporadic acanthostyles. According to Astrova (1978) these two genera are similar, but can be distinguished because Monticulipora has fewer mesozooecia, walls with granular microstructure, and cystiphragms always attached to the wall side nearest to the maculae. However, after a detailed study of the species assigned to these genera, I have observed no clear separation between them as these characters used by Astrova (1978) to distinguish between these genera are mixed up in some species. Prasopora fritzae Loeblich, 1942 , from the Upper Ordovician of Oklahoma, Monticulipora mammulata d’Orbigny, 1850 , as described by Singh (1979) from the Upper Ordovician of Indiana and Kentucky, and by Boardman & Utgaard (1966) in the Upper Ordovician of Ohio, and finally Monticulipora parallela McKinney, 1971 (Middle Ordovician of Alabama), were all characterized as having the same laminated-granular microstructure wall.

In spite of Astrova’s (1978) assertion of the scarcity of mesozooecia in Monticulipora , some of its species have mesozooecia in similar densities to Prasopora . Even more, some species assigned to Prasopora have fewer mesozooecia per mm2 than Monticulipora cystiphragmata n. sp. or Monticulipora epidermata Ulrich & Bassler, 1904 (as was described by Utgaard & Perry [1964] in the Upper Ordovician from Indiana and Ohio) for example Prasopora fritzae , P. prismatica Fritz, 1957 , P.similis Fritz, 1957 (the two last species from the Middle Ordovician of Ottawa), P. fistuliporides Vinassa de Regny, 1910 (Upper Ordovician from Sardinia [ Italy], Conti [1990]), and P. thorali Prantl, 1940 (Upper Ordovician from Wales, Buttler [1991]). Nevertheless, the same Prasopora colony can have a variable number of mesozooecia in different parts or at different depth of the zoarium. But some of these differences in mesozooecia density, of the species mentioned above, could be due to incomplete measurements.

It seems that the most constant character in Monticulipora is the arrangement of cystiphragms around maculae, but still there are some species that do not follow this. In this study most of the Monticulipora species recognized have neither cystiphragms nor diaphragms in the outer exozone, and the former are bigger in the inner endozone. However, this character is not persistent in all species, because the following ones have been described as having diaphragms, and sometimes cystiphragms, throughout the autozooecial: Monticulipora epidermata Ulrich & Bassler, 1904 as described by Utgaard & Perry (1964) from the Middle Ordovician of Indiana and Ohio, and by Brown & Daly (1985) in the Upper Ordovician from Indiana; Monticulipora multipora Dyer, 1925 as described by Utgaard & Perry (1964), also in the Middle Ordovician from Indiana and Ohio, and by Fritz (1976) in the Upper Ordovician from Ontario and Toronto; and Monticulipora grandis Ulrich, 1886 , as described by Bork & Perry (1968) in the Middle Ordovician from Illinois, Iowa and Wisconsin. One of these species, Monticulipora grandis , has been alternatively assigned to Monticulipora and Prasopora ( Nickles & Bassler [1900] assigned it to Prasopora , and Bork & Perry [1968] assigned it back to Monticulipora ).

After a comprehensive review of the type species of Monticulipora and Prasopora ( Monticulipora mammulata as described by Ulrich [1882], Boardman & Utgaard [1966], Singh [1979], and Brown & Daly [1985], and Prasopora grayae as described by Nicholson & Etheridge [1877] and by Buttler [1991]) and of a large number of species belonging to these genera it is concluded that Monticulipora has fewer mesozooecia, more polygonal autozooecial apertures and simpler cystiphragms (isolated cystiphragms or cystiphragms forming a single row) than Prasopora . Cystiphragms and diaphragms in the endozone and the inner exozone, as well as acanthostyles are common to almost all Monticulipora species , while in Prasopora cystiphragms and diaphragms are equally distributed in the autozooecia, and acanthostyles are rare.