Pourtalesiidae Agassiz 1881

Minin, Kirill V., Mironov, Alexandr N., Petrov, Nikolay B. & Vladychenskaya, Irina P., 2024, Evolutionary and biogeographic patterns in the deep-sea echinoid families Pourtalesiidae Agassiz 1881 and Ceratophysidae fam. nov. (Echinoidea), Zoological Journal of the Linnean Society 202 (4), pp. 1-30 : 12-13

publication ID	https://doi.org/10.1093/zoolinnean/zlae034
publication LSID	lsid:zoobank.org:pub:E00BFDE-D7E9-4515-88C5-25A4993398FF
DOI	https://doi.org/10.5281/zenodo.14833342
persistent identifier	https://treatment.plazi.org/id/5B0C164C-663C-8824-41B9-D788D840F9CF
treatment provided by	Plazi
scientific name	Pourtalesiidae Agassiz 1881
status

Treatment

Family Pourtalesiidae Agassiz 1881 View in CoL

( Figs 1D, E View Figure 1 , 2A–E View Figure 2 , 3–9 View Figure 3 View Figure 4 View Figure 5 View Figure 6 View Figure 7 View Figure 8 View Figure 9 )

Diagnosis: Frontal furrow deepest on oral side of test. Peristome at posterior end of deep furrow, facing forwards, not visible from below. Labral plate small, asymmetrical, separated from sternal plate by two, three, or even four asymmetrical pairs of plates ( Fig. 1D, E View Figure 1 ). No rostral plate. All gonopore-bearing plates in contact. Marginal fasciole absent.

Genera included: Cystocrepis Mortensen 1907 and Pourtalesia Agassiz 1869 (type genus). The fossil record of the Pourtalesiidae can be traced back to the Middle Miocene of the north-eastern Honshu Is. ( Pourtalesia sp. ; Kikuchi and Nikaido 1985).

Remarks: The family Pourtalesiidae is restricted to include only the genera Pourtalesia and Cystocrepis . These genera are characterized by the plastron plating of the type VI: a small asymmetrical labral plate is separated from the sternal plate by two to four asymmetrical pairs of plates (two or three pairs of ambulacrals and, sometimes, one pair of interambulacrals); the intercalating ambulacral plates lack intra-plate lines; the labral plate is often not visible. This morphological synapomorphy of pourtalesiids (type VI plastron plating) is well-supported by the molecular data and clearly differentiates them from the representatives of the families Ceratophysidae and Galeasteridae .

Apart from the plastron plating, the other diagnostic features of the family Pourtalesiiadae , listed in the revised diagnosis, do not depart from those previously used. The characters of the apical system are in accordance with the diagnosis of Smith and Kroh (2011), with some simplifications. The characters of the frontal furrow, peristome, and fascioles follow those listed by Smith (2004) for the family Pourtalesiidae as represented by the genus Pourtalesia .

The genus Pourtalesia differs from the monotypic Cystocrepis in having a supramarginal periproct, subanal rostrum, subanal fasciole, and longer valves of the ophicephalous pedicellariae. Among 12 Pourtalesia species described to date, P. aurorae Koehler 1926 is morphologically closest to Cystocrepis . In this species, the subanal rostrum is very small, and the periproct is more marginal than supramarginal. The species here referred to as Pourtalesia (?) sp. A has an even smaller subanal rostrum that takes the inframarginal position below the marginal periproct ( Fig. 4C, D View Figure 4 ). This set of features makes the species transitional in morphology between the two genera. Pourtalesia (?) sp. A thus might represent a new genus of pourtalesiids. Molecular data provide evidence that Pourtalesia (?) sp. A represents a separate phylogenetic lineage that is sister to the group comprised of Cystocrepis setigera and all other representatives of Pourtalesia ( Fig. 3 View Figure 3 ). However, the statistical support of these groupings is weak in one of the two analyses (namely, the ML). Apart from the unusual test shape, no significant differences (e.g. in external test appendages) between Pourtalesia (?) sp. A and the species of the genus Pourtalesia are found at the moment. Additional morphological and molecular data are needed to determine whether Pourtalesia (?) sp. A deserves establishing a new genus to accommodate the species. This problem will be addressed in the future. Hereinafter, this putative new species will be provisionally referred to the genus Pourtalesia .

Pourtalesia in its current state is the most species-rich among the genera of Urechinina . Apart from the 12 species described to date ( Mironov 1995b), representatives of the five more yet undescribed species are available at the authors’ disposal.