Cryptostomid Bryozoans From The Sassito Formation, Upper Ordovician Cool‐Water Carbonates of the Argentinean Precordillera

Abstract

Two new bryozoan species are described from the Upper Ordovician Sassito Formation of the Argentinean Precordillera: Moyerella spinata sp. nov. and Phylloporina sassitoensis sp. nov. The bryozoans are found in cool-water carbonates. The Silurian genus Moyerella is reported the first time in the Ordovician, showing palaeobiogeographic connections with Estonia and Siberia.

The upper Katian (Ordovician) bryozoans from the Eastern Iberian Chain (NE Spain)

“…However, transversal sections of the Iberian material closely conform to Ulrichostylus diagnosis, therefore it can be confidently assigned to this genus. The absence of diaphragms and acanthostyles is characteristic of Ulrichostylus radiatus Conti, 1990, as was described in the type material from Sardinia (Italy) (Conti 1990) and by Ernst & Key (2007) in the Montagne Noire (France), in both cases Late Ordovician in age. The absence of these characters also in the Iberian material, as well as the number of autozooecial rows and an autozooecial diameter similar to that of Ulrichostylus radiatus has allowed assigning of these specimens to this species.…”

“…-This zoarium is closely related to Graptodictya meneghinii (Vinassa de Regny, 1942) as was described by Ernst & Key (2007) from the Montagne Noire, France. The two collections share the same relative size of the large and small diameter of the zoarial branches; the angle of autozooecia with the mesotheca and the shape of the latter; the oval shape of the autozooecial apertures and its separation, both longitudinally and diagonally; the presence of hemisepta and their shape; the distribution and the microstructure of the extrazooecial skeleton, as well as the absence of heterozoecia and maculae.…”

“…-Zoarium with erect growth habit, with segments of different sizes; transversal section subcircular, 0.50 mm diameter on average; axial region formed by well-defined linear axis, sometimes substituted by a thin layer; autozooecial apertures with small peristome, arranged Ernst & Key 2007) are the following: erect growth habit with different sizes of segments; axial region with a lineal axis, less commonly a central layer, from which the autozooecia bud; the oval shape of the autozooecia and the triangular shape of the metazooecia; the arrangement of autozooecia in longitudinal rows on the zoarial surface; clearly visible autozooecial boundaries; the development of a thick extrazooecial skeleton, and the absence of acanthostyles. The study of different species included in Matsutrypa shows that the characters used to distinguish them are mainly the diameter of the zoarial segments, the number of autozooecial longitudinal rows, the density of autozooecial apertures per mm, the thickness of the extrazooecial skeleton and the presence/absence of diaphragms.…”

“…The measurements were taken directly from the thin section using the microscope with a micrometer, or from scaled photographs. The suprageneric classification is based on for the suborder Ptilodictyina, the web page: http://bryozoa.net/iba.html, edited by Phil Bock for the order Fenestrata and Ernst & Key (2007) for the rest of orders, suborders and families. The material described here is housed in the Museo de Paleontología de la Universidad de Zaragoza, specimen numbers MPZ 2006/100-107, 111, 112, 114-116, 118-125, 127, 128, 135-162, 164-167, 169-184, 186, 188-197, 199-201, 203-230, 233-238, 240-251, 253, 255-258, 261-272, 274-290 andMPZ 2008/169. Description.…”

“…The bryozoans occurring in rocks of the same age as the Cystoid Limestone Formation, from the Montagne Noire, France (Dreyfuss 1948, Boulange 1963, Ernst & Key 2007, and Sardinia (Conti 1990), have already been well studied. The contributions of Buttler & Massa (1996) and Buttler et al (2007) describing a total of seven species in the Upper Ordovician of Libya, as well as the contributions of Termier & Termier (1950) and Destombes et al (1971) identifying five genera in the Upper Ordovician of Morocco must also be acknowledged.…”