Thompson et al.—Permian echinoids
Other species.—Pronechinus cretensis König, 1982 from the Asselian of Crete.
Pronechinus? sp. Figure 2.15–2.21
Occurrence.—Lamar Member of the Bell Canyon Formation of the Guadalupe Mountains, West Texas. Capitanian in age. Locality 728p from Cooper and Grant (1972). See preceding description of localities in Eotiaris guadalupensis for details.
Description.—This taxon is known only from disarticulated ambulacral and interambulacral plates. Ambulacral plates variably polygonal in shape. Some plates bear well-defined imperforate tubercles (Fig. 2.15) while others do not (Fig. 2.19). In addition, some pore pairs are surrounded by distinct peripodia (Fig. 2.15, 2.16). Peripodia about 0.5 to 0.8 times as wide as plates. Ambulacral plates both with and without primary tubercle can bear smaller secondary tubercles. Pore pairs per- forating ambulacral plates at about halfway through their thickest point. Ambulacral plates with adoral margin heavily beveled, and ambulacral plating almost certainly imbricate. Interambulacral plates also imbricate, larger than ambulacral plates. All bearing minute tubercles but with some additionally bearing distinct imperforate primary tubercles.
Materials.—USNM 617192 and USNM 617193 (Fig. 2.15) are ambulacral plates with well-defined peripodial rims. USNM 617194 (Fig. 2.16) is an ambulacral plate with a well-defined peripodial rimand imperforate
tubercle.USNM617195 (Fig. 2.18) is an ambulacral platewithout awell-defined peripodial rim and an imperforate tubercle. USNM 617196 (Fig. 2.19) lacks both a well- defined peripodial rim and a primary tubercle. USNM 617198– 617200 are lots of ambulacral plates and USNM 617197 and 617201 (Fig. 2.20, 2.21) are lots of interambulacral plates.
Remarks.—This taxon is questionably assigned to Pronechinus because the details of the arrangement of its test plating are incompletely known. The details of the interambulacral and ambulacral plates, however, confidently allow placement within the Proterocidaridae. Pronechinus is the only proterocidarid that has numerous ambulacral plates with small tubercles lacking peripodia yet containing large tubercles. These plates are located within the more perradial ambulacral columns of Pronechinus anatoliensis, and this tuberculatemorphology is present among the ambulacral plates described herein (Fig. 2.18). Proterocidaris belli (Kier, 1965) from the Pennsylvanian Marble Falls Formation of
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Texas has ambulacral plates with adoral tubercles; however, all of these plates bear peripodia (Kier, 1965). In addition, it is likely that the interambulacral plates with primary tubercles described herein are adambulacral in origin, as the adambulacral plates of Pronechinus anatoliensis bear distinct primary tubercles (Kier, 1965). Pronechinus is known from two species, Pronechinus cretensis and Pronechinus anatoliensis from the Asselian and Changhsingian respectively (Fig. 4). This is the first putative occurrence of this genus in the Capitanian and the first occurrence of a proterocidarid in the Permian of North America, indicating that the Proterocidaridae were likely biogeographically widespread in the Permian.
Echinoidea indet. Figure 3.1–3.3
Occurrence.—Same as for Eotiaris guadalupensis.
Description.—Numerous disarticulated fragments of Aristotle’s lanterns with associated teeth are present among the described fauna. Most of the fragments are disarticulated hemipyramids, though some articulated hemipyramids with teeth are present (Fig. 3.1–3.3). Maximum height of hemipyramid is 16.44mm. Foramenmagnum is 1.58mmdeep on this specimen and generally sloping at about 50° to the horizontal. Depth and angle of foramen magnum are variable; however, even in smaller specimens, the foramen magnum never appears to exceed 0.2 times the height of the hemipyramids. Protractor muscle scars about halfway down length of hemipyramid terminating in deep perforation. Retractor muscle attachment scars
below.The wing edge is a faint ridge along the side of the hemipyramids, though may be faint due to pre- servational biases. Wings about 0.3 times as long as hemipyramids are high. Dental slide present. Teeth U-shaped, nonserrate.
Materials.—Lanterns are in lots USNM 617190 (Fig. 3) and 617191.
Remarks.—It is unknown whether the pyramids described here can be attributed to any of the taxa described herein. The hemi- pyramids are much taller than the test of Eotiaris guadalupensis; thus, it is unlikely that the pyramids belong to this taxon. Smith and Hollingworth (1990) described the lantern of Eotiaris keyserlingi, which is much smaller than the pyramids discussed here. The morphology of lanterns of echinoids in the upper Paleozoic is rarely described in detail (though see Lewis and Ensom [1982] for a counter example). The indeterminate pyramids described here appear to be similar in morphology to
Figure 2. Permian archaeocidarids from Timor, Kansas, the Salt Range (presumably Pakistan), and west Texas, and ambulacral and interambulacral plates of Pronechinus? sp. (1) Interambulacral plate of Permocidaris? timorensis (Wanner, 1941) from the Permian of Timor (RGM 835575). Specific locality unknown. Crenulate tubercle of this taxon is very similar to those of the indeterminate archaeocidarid in Figure 2.6, 2.7. (2) Interambulacral plate of holotype of Archaeocidaris manhattanensis (MGL 206289). Note plate dimensions, which are similar to those of Archaeocidaridae indet. in Figure 2.7–2.9. (3) Syntype of Archaeocidaris forbesiana (NMS G.1871.1.34); (4) First plate morphotype of Archaeocidaridae indet. (USNM 617188a); (5) interior view of same plate; note lack of denticulate margin indicating median location of plates. (6) Crenulate interambulacral plate of Archaeocidaridae indet. (USNM 617188b); (7) crenulate interambulacral plate of second plate morphotype of Archaeocidaridae indet. (USNM 617189); (8) adambulacral second interambulacral plate morphotype of Archaeocidaridae indet. (USNM 617189). Note plate dimensions, which are much higher than wide. (9) Interior side of the same; (10) spine of Archaeocidaridae indet. (USNM 617187a); (11) The same in cross section. Note triangular cross section. (12) Base and acetabulum of spine (USNM 617187b); (13) the same spine in plan view; (14) thin spine of Archaeocidaridae indet. (USNM 617187c); (15) ambulacral plate of Pronechinus? sp. with well-developed peripodial ring surrounding pore pairs (USNM 617193); (16) ambulacral plate of Pronechinus? sp. with peripodial ring and imperforate primary tubercle (USNM 617194); (17) same as 2.16 but in side view; (18) ambulacral plate lacking peripodial ring and with imperforate primary tubercle (USNM 617195); (19) ambulacral plate lacking well-defined peripodial ring and primary tubercle (USNM 617196); (20) interambulacral plate of Pronechinus? sp. with large imperforate primary tubercle (USNM 617197a); (21) nontuberculate interambulacral plate of Pronechinus? sp. (USNM 617197b). Scale bars = 2.5mm.
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