The genus Calix Rouault, 1851 (Echinodermata, Aristocystitidae) from the Ordovician of peri-Gondwanan regions: a taxonomic review
Abstract
Aristocystitid diploporitan echinoderms were major components of Mid-Late Ordovician benthic communities in peri-Gondwanan regions, yet their taxonomy remains problematic owing to the frequent absence of the oral surface, a key diagnostic feature. The genus Calix Rouault, 1851, one of the most widespread and long-recognised aristocystitids, exemplifies this difficulty: numerous species historically attributed to Calix were erected solely from aboral morphologies. This study re-examines all taxa traditionally assigned to Calix, based on direct investigation of type and additional material from European and North African localities, supported by high-resolution morphological documentation and multivariate statistical analyses. A suite of 17 morphological characters, coded across 62 specimens representing Calix and allied genera (Enodicalix, Lepidocalix, Oretanocalix, Phlyctocystis, Sinocystis), was analysed using supervised and unsupervised multivariate approaches. The results reveal that Calix, as historically delimited, was strongly polymorphic, comprising morphotypes or species more closely allied to other related genera. Our revised diagnosis restricts Calix to a small, morphologically consistent group, comprising C. sedgwicki, C. purkynei (including morphotypes 'a' and 'c' of C. rouaulti), and C. hajraensis, characterised by a tetraradiate peristome, irregular thecal plating, spiny ornamentation, and radially arranged diplopores. Several species formerly included in Calix are reassigned: C. toledensis and the 'd' morphotype of C. rouaulti to Enodicalix; C. cornuta, C. segaudi, and morphotypes 'b', 'e' to 'g' of C. rouaulti to Oretanocalix; C. termieri to Phlyctocystis; and C. gutierrezi and C. rotundipora tentatively to Sinocystis. These results establish clearer morphological boundaries among the six genera of Calicinae and provide a robust, quantitative framework for aristocystitid taxonomy. The genus Calix thus emerges as a distinct, morphologically stable taxon rather than a repository for poorly constrained forms.
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BibTeX
@article{makhlouf2026genus,
title = {{The genus Calix Rouault, 1851 (Echinodermata, Aristocystitidae) from the Ordovician of peri-Gondwanan regions: a taxonomic review}},
author = {Yamouna Makhlouf and Elise Nardin and Bertrand Lefebvre and Ahmed Nedjari and Jorge Colmenar and Juan Carlos Gutiérrez-Marco and Christopher R. C. Paul},
journal = {Journal of Systematic Palaeontology},
year = {2026},
month = aug,
doi = {10.1080/14772019.2026.2698627},
url = {https://hal.science/hal-05768170v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - The genus Calix Rouault, 1851 (Echinodermata, Aristocystitidae) from the Ordovician of peri-Gondwanan regions: a taxonomic review
AU - Yamouna Makhlouf
AU - Elise Nardin
AU - Bertrand Lefebvre
AU - Ahmed Nedjari
AU - Jorge Colmenar
AU - Juan Carlos Gutiérrez-Marco
AU - Christopher R. C. Paul
PY - 2026
DA - 2026/08/28
JO - Journal of Systematic Palaeontology
DO - 10.1080/14772019.2026.2698627
UR - https://hal.science/hal-05768170v1
AB - Aristocystitid diploporitan echinoderms were major components of Mid-Late Ordovician benthic communities in peri-Gondwanan regions, yet their taxonomy remains problematic owing to the frequent absence of the oral surface, a key diagnostic feature. The genus Calix Rouault, 1851, one of the most widespread and long-recognised aristocystitids, exemplifies this difficulty: numerous species historically attributed to Calix were erected solely from aboral morphologies. This study re-examines all taxa traditionally assigned to Calix, based on direct investigation of type and additional material from European and North African localities, supported by high-resolution morphological documentation and multivariate statistical analyses. A suite of 17 morphological characters, coded across 62 specimens representing Calix and allied genera (Enodicalix, Lepidocalix, Oretanocalix, Phlyctocystis, Sinocystis), was analysed using supervised and unsupervised multivariate approaches. The results reveal that Calix, as historically delimited, was strongly polymorphic, comprising morphotypes or species more closely allied to other related genera. Our revised diagnosis restricts Calix to a small, morphologically consistent group, comprising C. sedgwicki, C. purkynei (including morphotypes 'a' and 'c' of C. rouaulti), and C. hajraensis, characterised by a tetraradiate peristome, irregular thecal plating, spiny ornamentation, and radially arranged diplopores. Several species formerly included in Calix are reassigned: C. toledensis and the 'd' morphotype of C. rouaulti to Enodicalix; C. cornuta, C. segaudi, and morphotypes 'b', 'e' to 'g' of C. rouaulti to Oretanocalix; C. termieri to Phlyctocystis; and C. gutierrezi and C. rotundipora tentatively to Sinocystis. These results establish clearer morphological boundaries among the six genera of Calicinae and provide a robust, quantitative framework for aristocystitid taxonomy. The genus Calix thus emerges as a distinct, morphologically stable taxon rather than a repository for poorly constrained forms.
SN - 1477-2019
SN - 1478-0941
ER -