New trepostomate bryozoans from the Upper Ordovician of Morocco and the temperature influence on zooid size

Abstract

New Upper Ordovician trepostomate bryozoans from the eastern Anti-Atlas of Morocco have been identified. They have been collected from the lower and intermediate units of the Khabt-el-Hajar Formation, late Katian in age, representing, respectively, bryozoan-pelmatozoan meadows with siliciclastic input, degraded by wave activity in a mid-ramp setting, and outer-ramp environments with marly substrates. Ten species of the genera Cyphotrypa, Calloporella, Diplotrypa, Parvohallopora, Dekayia, and Aostipora are described. Of them, three species are new: Cyphotrypa regularis Jiménez-Sánchez, Parvohallopora cystata Jiménez-Sánchez, and Aostipora elongata Jiménez-Sánchez. Univariate statistical analyses of the sub-polar Moroccan species, in addition to other congeneric species of high, middle, and low latitudes, corroborate that for the trepostomate bryozoan the temperature of the ambient water was a primary control on zooecium size variations. Nevertheless, other environmental factors, besides temperature, must have also influenced significantly the zooid size, at least in low latitudes. Our data also give further support for considering the zooecium wall thickness as a limiting factor for the zooid size increment with latitude in the trepostomates.

New bryozoans from the Upper Ordovician of Morocco and their place in the temperate-to-cool water Mediterranean Province

“…From Parvohallopora sp. described in Jiménez-Sánchez et al (2015b) this new material can be distinguished because it has less mesozooecia/mm 2 (4.5/mm 2 in Parvohallopora sp. 1 vs 11.0/mm 2 in Parvohallopora sp.…”

“…Aostipora sp. differs from A. elongata Jiménez-Sánchez in Jiménez-Sánchez et al (2015b), described also in the Khabt-el-Hajar Formation, in the absence of elongated-flattened macula composed of a calcitic deposit, in the lack of tubules (not real acanthostyles), and in the smaller exozone/endozone ratio (0.18 in Aostipora sp. vs 0.36 in A. elongata).…”

“…In the Khabt-el-Hajar Formation (Upper Ordovician of Morocco) P. cystata Jiménez-Sánchez (in Jiménez-Sánchez et al 2015b) and Parvohallopora sp. (Jiménez-Sánchez et al 2015b) have been previously described.…”

“…(Jiménez-Sánchez et al 2015b) have been previously described. The new specimens included in Parvohallopora can be distinguished from P. cystata because cystoidal diaphragms are abundant in the latter species and it has larger autozooecial diameter (0.20-0.46 mm in P. cystata vs 0.22-0.37 mm in Parvohallopora sp.…”