Cyamidia paucipora Brunnschweiler, 1962

Mooi, Rich, Kroh, Andreas & Srivastava, Dinesh K., 2014, Phylogenetic re-evaluation of fossil and extant micro-echinoids with revision of Tridium, Cyamidia, and Lenicyamidia (Echinoidea: Clypeasteroida), Zootaxa 3857 (4), pp. 501-526 : 513-517

Cyamidia paucipora Brunnschweiler, 1962

Figures 7A–C , 8–9 , 10D , 11 .

1962 Cyamidia paucipora Brunnschweiler : 162–164; fig. 1A–D.

Type material. GA CPC 2825 (holotype; Figs 7A–C , 10D ) .

Material studied. In addition to the holotype, 7 “topotypes” (GA CPC 2826 , 41767–41772 ) of Brunnschweiler (1962) .

Type locality. Sample M 24 from point 221 on airphoto No. 5170 on Run 2, Moogooloo Hill (hill crest located at 23° 36′ 12″ S, 114° 44′ 14″ E; exact coordinates of sampling locality unknown); about 8 miles SSE of the Pleiades Hills, Northwest Division , Western Australia .

Type stratum. Merlinleigh Sandstone, Late Eocene (see Darragh & Kendrick 2010: pp. 24–25)

ZooBank LSID. urn:lsid:zoobank.org:act:AC48DF0B-22B0-4ED3-AB19-1B1EBAFB1799

Description. Size and shape —Corona very small, up to 3.5 mm in TL in material originally attributed to this species; outline distinctly oval (antero-posteriorly elongated) in aboral view; slightly flattened in profile, maximum height decreasing with size, being up to 70% of TL in smallest and approximately 56% TL in largest specimens.

Internal buttressing —Absent.

Apical disc —Situated centrally, at apex of corona; monobasal, with four gonopores and single hydropore which lies close to genital pore 2 and not situated in pit or groove; ocular pores small and located outside area enclosed by gonopores ( Fig. 9A ); gonopores open in specimens as small as 2.55 mm, but may still be completely closed in slightly larger specimens (2.69 mm TL).

Ambulacra —Plating not easily discernable, but ambulacra appear to expand towards ambitus; petals short, with up to five non-conjugate respiratory pore pairs in each ambulacrum; pore pairs strongly oblique, with obliqueness increasing distally; in small specimens with well-preserved surface detail, interporal areas raised, with glossy surface reminiscent of glassy tubercles, in slightly larger specimens this area is less raised but still appears to be composed of massive, unperforated stereom; interporiferous zones narrow and of constant width along petal; petaloid region large, extending about 60% of TL; food grooves absent; buccal pores not visible in oral view, apparently lying close to peristome and facing horizontally into it; accessory pores crowded in small oblique clusters in centre of each plate; widespread isolated accessory pores present between these clusters, including in interporiferous zones; ambitus initiating at approximately fourth pair of ambulacral postbasicoronal plates.

Interambulacra —Adapically, two unpaired plates lie in tandem adjacent to apical system ( Fig. 10D ); basicoronal plates stout and quadrangular; ambital plating not discernable; a few scattered accessory pores present both in aboral and oral interambulacral plates.

Tuberculation —Primary tubercles crenulate, perforate; homogeneously distributed on aboral surface; on oral surface, towards the peristome, tubercles up to 1.5 times larger and more widely scattered, separated by ridges bearing glassy tubercles and granules ( Fig. 9B ); tubercles entirely missing on basicoronal plate of interambulacrum 5 and most of plate surface of plates 5.a.2 and 5.b.2; here large glassy tubercles are found instead ( Fig. 9C ).

Peristome —Relatively large, about 25% TL; facing directly downwards; infundibulum shallow, but with down-turned, almost vertical lip; incomplete ring of slightly elevated ambulacral stereom bars framing peristome; distinct perradial bulge containing the sphaeridium in centre of each bar; in oral view, buccal pores are hidden by these bars.

Periproct —Smaller than peristome, approximately 12% TL; positioned inframarginally and facing obliquely down-/backwards in oral view; distinctly elongated along anterior-posterior axis; anterior end bounded by first pair of post-basicoronal plates (5.a.2, 5.b.2), other sutures not discernable.

Perignathic girdle —Consisting of five small processes (auricles), one on each interambulacral basicoronal plate.

Sphaeridia —One per ambulacrum; fully enclosed; situated beneath distinct transverse bar just distal to buccal pores.

Spines, pedicellariae, lantern —Unknown.

Remarks. Brunnschweiler (1962) established a new species for the specimens described above and attributed it to the genus Cyamidia on the basis of its elongate periproct and lack of internal buttressing. It was differentiated from previously described species of Cyamidia by its larger and more marginal periproct, the smaller number of petaloid pores and the glassy tubercles between the periproct and peristome. Brunnschweiler, however, did not take allometric growth into account. In most clypeasteroids, and indeed most echinoids, the periproct and peristome are proportionally larger in smaller specimens and the petaloid pore pair number is lower. The main difference from other Cyamidia species is therefore the presence of glassy tubercles between the periproct and peristome and the more marginal periproct (although periproct position too tends to change during early ontogeny).

Cyamidia paucipora co-occurs with the larger species Lenicyamidia compta at the type locality. At first glance the two species appear very different—the former is very small, high, and ovoid in outline, while the latter is larger, more flattened and rounded. It also has a distinct oral tuberculation pattern. Upon closer examination, however, the two forms appear to be part of a single ontogenetic series, with the main differences being related to differential growth. Test height, for example, increases only slowly during growth ( Fig. 11 ), causing the end members to look very different. When included in the same graph, specimens attributed to C. paucipora by Brunnschweiler (1962) fall along the same regression lines as L. compta . The size gap between C. paucipora and L. compta apparently led Brunnschweiler to believe that he was dealing with two different taxa. This discontinuity in the size distribution might have other reasons including, but not limited to: a) collection bias (the small specimens probably being picked from sieving residues, while the larger ones might have been hand-picked in the field); b) year-cohorts (many marine invertebrates reproduce only once annually, leading to different size cohorts within populations particularly among miniaturized, paedomorphic forms in which these size differences are exaggerated).

The only other difference between C. paucipora and Lenicyamidia , apart from shape and pore pair number, is that in tuberculation pattern. However, the oral, medial area of glassy tubercles in Lenicyamidia can easily be derived from the corresponding area in Cyamidia paucipora . The latter also largely lacks spine-bearing tubercles, and features glassy ones in the oral, medial area instead ( Fig. 9C ). Based on these observations, the two species are here considered synonymous and Lenicyamida compta is chosen as the senior synonym (Principle of the First Reviser; ICZN 1999 Art. 24.2).

Figures

FIGURE 7. Brunnschweiler's (1962) holotypes: A–C. Cyamidia paucipora (= juvenile Lenicyamidia compta), GA CPC 2825; D–F. Lenicyamidia compta, GA CPC 2827. Aboral (A, D), oral (B, E) and left lateral views (C, F).

FIGURE 8. SEM images of the test of three specimens of Cyamidia paucipora (= juvenile Lenicyamidia compta). A. GA CPC 41767, aboral view. B–D: GA CPC 41768, aboral (B), oral (C) and left lateral view (D); E–G: GA CPC 41769, aboral (E), oral (F) and left lateral view (G).

FIGURE 9. SEM images showing details on test surface of Cyamidia paucipora (= juvenile Lenicyamidia compta). A. Apical region of specimen GA CPC 41767, pores of each respiratory tube foot linked by dotted lines, other apertures labelled: H = hydropore; G1, G2, G3, G4 = gonopores of interambulacra 1, 2, 3, and 4, respectively; ocular pores indicated by arrows. B. Ornamentation of test just anterior of the peristome in specimen GA CPC 41768. C. Peristomial region of specimen GA CPC 41769 showing peristomial region and periproct (bottom of image). All scale bars 200 µm long.

FIGURE 10. Partial plate architecture of Lenicyamidia compta and Cyamidia paucipora (= juvenile Lenicyamidia compta). A–C. L. compta: A. aboral view of GA CPC 41774; B. oral view of the holotype GA CPC 2827; C. left lateral view of GA CPC 41774; D. C. paucipora, holotype CPC 2825, adapical part of interambulacrum 2. Labelling conventions as in Fig. 6.

FIGURE 11. Scatter plot of test width (solid squares; n = 30), height (open triangles; n = 27) and respiratory pore number (solid circles; n = 17) vs. test length for the material attributed to Lenicyamidia compta and Cyamidia paucipora by Brunnschweiler (1962). Size range of C. paucipora highlighted by grey backfill. Thumbnail images show outline and profile for the smallest and largest complete specimens. Within profiles, scale bars 1.0 mm long, arrows indicate anterior end. APP = anterior paired petals (i.e. petal II or IV).