Research paper

Pentaradiate diploporites (Echinodermata) from the Spanish Middle Ordovician and their taxonomic significance

 


CHRISTOPHER R.C. PAUL

School of Earth Sciences, University of Bristol, BS8 1RJ Bristol, United Kingdom; glcrcp@bristol.ac.uk
Corresponding author

JUAN CARLOS GUTIÉRREZ-MARCO
Instituto de Geociencias (CSIC, UCM), and Departamento de Geodinámica, Estratigrafía y Paleontología, Facultad de CC. Geológicas, José Antonio Novais 12, E-28040 Madrid, Spain; jcgrapto@ucm.es


ABSTRACT

New Middle Ordovician specimens of pentaradiate diploporite blastozoans from the southern Central Iberian Zone, Spain, show that Oretanocalix is an aristocystitid diploporite with five ambulacra; all other aristocystitid genera have 2‒4 ambulacra. The laterally elongate oral frame is composed of eight plates, with five, facet-bearing, circumorals (COO) and three, non-facet-bearing, periorals (POO). This necessitates a new interpretation of the aristocystitid oral area and diagnosis of the family Aristocystitidae. Previous interpretations assumed four COO and four POO. Weathered examples lack oral cover plates and show that plates CO1 and CO4, which support ambulacra D and B, respectively, do not reach the inner margin of the peristome. They also reveal abundant diplopores, which were covered by a thin epistereom in life. Diplopores grew at plate sutures and were incorporated into both adjacent plates as the plates enlarged. Oretanocalix julioi n. sp. extends the stratigraphic range of Oretanocalix back to the basal Dobrotivian ‒low in the Upper Darriwilian. The genus Batalleria is a sphaeronitid diploporite with food grooves that branched within the peristome. The branching pattern reflects Lovén’s law and is: AR, BL, CR, DL, ER, where A‒E denote Carpenter’s ambulacra and L (left) and R (right) denote on which side of the ambulacrum the first branch lies. Each branch leaves the peristome by a separate ambulacral orifice. No other sphaeronitids have food grooves that branch within the peristome and all other sphaeronitids have one ambulacral orifice per ambulacrum. Thus, a new diagnosis of sphaeronitids is necessary.


Key words: Echinodermata, Diploporita, Anambulacralia, Ordovician, Darriwilian, Central Iberian Zone.

How to cite: Paul, R.C.P. & Gutiérrez-Marco, J.C. 2022. Pentaradiate diploporites (Echinodermata) from the Spanish Middle Ordovician and their taxonomic significance. Spanish Journal of Palaeontology, 37(2).

Received 10 August 2022, Accepted 25 October 2022, Published online 25 November 2022

https://doi.org/10.7203/sjp.25498