Thompson et al.—Permian echinoids
interambulacral plates belonging to the second plate morphotype.
Remarks.—Although very few species of Archaeocidaris based off of articulated or semiarticulated test material are known from the Permian, numerous plates and spines that have been attributed to Archaeocidaris are known globally (e.g., Waagen, 1885; Prosser, 1895; Kittl, 1904; Gortani, 1905; Boos, 1929; Wanner, 1941;Matthieu, 1949;Kier, 1958b; Leupke, 1976; Simpson, 1976; Mihály, 1980; Webster and Jell, 1992; Hlebzevitsch and Cortiñas, 2009; Schneider, 2010). As cautioned by Kier (1958a, 1965), because different genera within the Archaeocidaridae have differ- ing numbers of interambulacral columns, it is best not to assign disarticulated archaeocidarid plates to a particular genus. That being the case, these plates likely belong to Archaeocidaris as the genus Polytaxicidaris Kier, 1958a is not knownfrom outside of the Mississippian, and the species of Polytaxicidaris for which exter- nal plate morphology is well known, Polytaxicidaris lirata Kier, 1965, displays perforate secondary tubercles (Kier, 1965, figs.4,6) and are very unlike the plates described herein. However, because this determination is not definitive, and because of its crenulate tubercles, the taxon is designated as Archaeocidaridae indet. The shape and secondary tuberculation of the first plate morpho- type is similar to the interambulacral plate morphology of numerous Archaeocidaris species, including Archaeocidaris brownwoodensis Schneider, Sprinkle, and Ryder, 2005, Archaeocidaris marmorcataractensis Thompson et al., 2015a, and Archaeocidaris wortheni Hall, 1858. The shape of the second plate morphotype, with its extended flange adorally and aborally, is similar to that of the plates of Archaeocidaris rossica (von Buch, 1840) from the Pennsylvanian of Russia. This plate morphotype is also present in Archaeocidaris selwyni Etheridge, 1892 and archaeocidarids described as ‘Cidaroid indet.’ in Webster and Jell (1992) from the Permian of Australia, Archaeocidaris manhattanensis Matthieu, 1949 (Fig. 2.2) from the Permian of Kansas, and Archaeocidaris aculeata Shumard in Shumard and Swallow, 1858 from the Pennsylvanian of Kansas. The plates of the indeterminate archaeocidarid fromthe Bell Canyon Formation, however, are different from those of these aforementioned taxa in that they display crenulate tubercles (Fig. 2.6, 2.7). The only definitive species of Archaeocidaris with crenulate tubercles is Archaeocidaris apheles Schneider, Sprinkle, and Ryder, 2005; however, these are merely faint indentations on the platformof the tubercle, and may not be homologous with true crenulate tubercles. Archaeocidaris forbesiana (de Koninck, 1863), which was placed into Archaeocidaris tentatively by Jackson (1912), was illustrated with crenulate tubercles by Waagen (1885). In addition, crenulate tubercles are known from echinoids from the Permian of Timor (Wanner, 1941; Fig. 2.1). That crenulate tubercles are clearly pre- sent in the indeterminate archaeocidarid described herein indicates that the crenulate tubercles illustrated by Waagen (1885) were likely truly present on the figured specimens and that crenulate tubercles were likely widespread among numerous taxa in the Permian. Crenulate tubercles are also present in miocidarids such
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as Eotiaris keyserlingi (Geinitz, 1848) and Eotiaris guadalupensis, and the importance of crenulate tubercles on Archaeocidaris?sp. will be discussed further in the following. It is also necessary herein to address the genus Permoci-
daris Lambert, 1900, which has been regarded within the Miocidaridae by Smith and Kroh (2011) and has also been described as having crenulate tubercles. The type species of Permocidaris is Cidaris forbesiana de Koninck, 1863, and the type specimen is NMS G.1871.1.34. The type of Cidaris forbesiana consists of several disarticulated spines that are clavate in morphology, bearing columns of spinules arranged laterally from the proximal end, slightly above the milled ring, to the distal end (Fig. 2.3). Waagen (1885) attributed several disarticulated interambulacral plates to this species, while transferring it to the genus Eocidaris Desor, 1856. He and Bather (1909) pointed out that these plates were not definitively associated with the spines described by de Koninck (1863). Bather (1909) rightly pointed out that, dependent upon the morphology of the interambulacral plates, there seems little to distinguish Permocidaris from Archaeocidaris save for its crenulate tubercles. However, because the material attributed by Waagen (1885) to Eocidaris forbesiana and the spines similar to the type of Eocidaris forbesiana have not been found in direct association, it is best to treat this material as indeterminate, and as such, we treat the genus Permocidaris Lambert, 1900 as incertae sedis. Furthermore, as this genus is known solely from disarticulated spines and plates, its familial level affiliation is uncertain. Smith and Kroh (2011) choose to place it within the Miocidaridae, one of the diagnosable characters of which is the presence of two columns of interambulacral plates. As the number of interambulacral columns of this taxon is unknown, however, this seems unadvisable. Furthermore, if the inter- ambulacral plates assigned by Waagen (1885) to Eocidaris forbesiana are similar in nature to the interambulacral plates herein assigned to Archaeocidaridae indet., then they may well in fact have been arranged into more than two columns of interambulacral plates, as is the case with the latter. Permoci- daris? timorensis Wanner, 1941 from the Permian of Timor also appears to have interambulacral plates bearing crenulate tubercles arranged into more than two columns, as plates both with and without a denticulate margin bear crenulations (Wanner, 1941, pl. 25, figs. 11–19). Because both of these taxa have more than two columns of interambulacral plates and crenulate primary tubercles, they may be closely aligned. Because of the incomplete nature of specimens of both taxa, however, we find it best to treat both as indeterminate.
Family Proterocidaridae Smith, 1984
Type genus.—Proterocidaris de Koninck, 1882 Genus Pronechinus Kier, 1965
Type species.—Pronechinus anatoliensis Kier, 1965 from the Changhsingian of southeastern Turkey.
Figure 1. Cidaroid echinoids from the Bell Canyon Formation. (1) Straight spine of Eotiaris guadalupensis (USNM 610605c); (2) clavate spine of Eotiaris guadalupensis (USNM 610605a); (3) spine base and milled ring of USNM 610605 (same as 2.2); (4) paratype of Eotiaris guadalupensis (USNM 610601). This specimen consists of a single interambulacral area with at least six interambulacral plates in each column. (5) Holotype of Eotiaris guadalupensis (USNM 610600). Note crenulate tubercles and spine, which is morphologically similar to those in Figure 1.1–1.3. Scale bars = 2.5mm.
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