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Journal of Paleontology 90(1):59–77
surfaces of cephalon and pygidium with finely granulose sculpture, augmented by tubercles on glabella.
Lectotype.—According to Nitecki and Golden (1970), a crani- dium (UC 965; Fig. 6.9, 6.10) in the Field Museum was ori- ginally part of the collection of U.P. James, and was figured by Meek (1873, pl. 14, fig. 2a) in his description of Dalmanites carleyi. We select it as the lectotype. It is most likely from the Fairmount Member of the Fairview Formation (Foerste, 1919) of the Cincinnati region.
Other material.—Five cephala (CM 51280a, CM 51280b, CM 51280c, CM 31699a, CM 31699b), and two pygidia (CM 51280d, CM 31699c).
Description.—Cephalon is relatively wide, semielliptical out- line (excluding genal spines); cranidium approximately sub- trapezoidal in outline. Cranidial length approximately 47% of the cranidial width across the posterolateral fixigena. Axial furrow generally shallowly impressed; the furrow tends to weaken in front of L3. Well-defined apodemal pit at intersection of S3 and axial furrow. Glabella outline pinches inward from the LO to the narrowest point across L1, slowly expands from L2, then more rapidly across L3 and the anterior lobe. The anterior tip of LO and the posterior tip of L2 are approximately parallel. Maximum width of the glabella across the anterior lobe is approximately 48% of cranidial width; glabella has low convexity, relatively flat adaxially. LO relatively wide and long; generally subovate in outline but posterior margin nearly transverse medially; expands outward beyond level of L1. LO occupies approximately 19% of total glabellar length. L1 rela- tively transverse, elongate subrectangular in outline. L2 angled slightly posteriorly, middle portion of the lobe is slightly expanded, but outline is otherwise subrectangular. L3 is larger, subtriangular in outline, narrows sharply toward the axis. Anterior lobe is relatively long and narrow, only slightly extending past L3; subovate in outline, rounded anteriorly especially along the lateral margins. SO narrow, shallowly impressed along the axis, then marked by deeper lateral furrows angled very slightly anteriorly. S1 furrow moderately impressed, transverse laterally, curves gently anteriorly adaxially. S2 furrow directed obliquely backward, more strongly developed adaxially, terminating short of lateral glabellar margin. S3 extends oblique forward; becomes more strongly impressed abaxially toward the apodemal pit. Palpebral lobe narrow, arcuate band that tapers abaxially; palpebral furrow is finely etched groove. Eye extends from S3 to S1; does not reach axial furrow anteriorly. Anterior branch of the facial suture curves inward to follow anterolateral margin of the anterior glabellar lobe. Posterior branch of facial suture poorly preserved but apparently nearly transverse. Genal spine moderately long, less than half of total librigenal length and slightly less than glabella length. Coarsely granulose sculpture covers entire cranidial surface, with tubercles on central part of glabella and anterior lobe; on well-preserved specimens, weak median embayment on anterior glabellar margin flanked by indistinct, larger tubercles. Librigenal lateral border and border furrow well defined; furrow expressed as a relatively wide, trough-like break in
slope. Librigenal field moderately convex; subocular furrow gently impressed. Visual surface of eye weakly conical in lateral view, with width approximately three-fourths of height. Twenty-two columns of lenses with up to eight lenses. Strongly developed granular sculpture across the librigena. Pygidium elongate, triangular to subtriangular in
outline, length approximately 90% of width. Axis of 11 to 12 well-defined rings and furrows outlined by distinct axial furrows. Pleural field relatively flat adaxially, but with strong change in slope distally toward weak lateral border defined only by absence of furrows. Up to 12 pairs of oblique, firmly impressed pleural furrows; interpleural furrows obsolete. Granulose sculpture developed along the axis.
Remarks.—In their revision of Achatella, Ludvigsen and Chatterton (1982) noted the limited information available for A. carleyi (Meek, 1872), although they speculated that it might be a junior synonym of A. achates. In addition to the lectotype, we had access to archival specimens from the type area (Figs. 6, 7). They are mostly compacted to varying degrees but demonstrate clearly that A. carleyi is a distinct species in the C1 and C2 deposition sequences in southern Ohio and northern Kentucky. Lespérance and Weissenberger (1998, p. 313) interpreted Foerste’s (1919, pl. 19, fig. 17) image of A. carleyi as showing a small occipital spine. There is no trace of a spine in any of our cephala, although there is an occipital tubercle (e.g., Fig. 6.2), which could perhaps be exaggerated by compaction in Foreste’s specimen. Meek (1872, 1873) does not mention either feature in his description. The pygidium that Meek (1873, pl. 14, fig. 2d) attributed to the species has a rounded posterior margin that resembles those illustrated in this paper (Fig. 7.3, 7.5). Achatella carleyi was compared to A. achates earlier, under
the discussion of the latter. It shares an outwardly curved lateral cephalic margin behind the posterior branch of the suture with A. katharina from Missouri and Oklahoma. However, it differs from A. katharina in having a much larger palpebral lobe (compare Fig. 6 and Fig. 8.8–8.11), a shorter (tr.) S2 glabellar furrow that terminates well short of the lateral glabellar margin (compare Fig. 6.1, 6.6, and 6.10 with Fig. 10), and a background sculpture of coarser granules; the posteriormargin of the pygidium is rounded (Fig. 7.3, 7.5) rather than sharply pointed (Fig. 12.4). Achatella consobrina (Tripp, 1954, pl. 4, figs. 26–33) has a
similarly sized eye to A. carleyi, but is closer to the glabella. The lateral margin of the cephalon appears to be evenly curved, rather than curved outward behind the posterior suture. The S2 furrow is better defined and extends to the lateral glabellar margin, and the sculpture of the glabellar surface includes numerous, more closely spaced fine tubercles. Other species, including A. kuckersianus (Schmidt), A. clivosa Lespérance and Weissenberger, and A. retardarta (Reed) have eyes that extend forward to reach the axial furrow.
Achatella katharina (Bradley, 1930) Figures 8–12
1930 Dalmanites katharina Bradley, p. 286, pl. 30, figs. 19–28. 1940 Dalmanites katharina; Delo, p. 112, pl. 13, figs. 26–29.
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