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Neosemantis bjoerklundi mimicus Goll, 1979

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Diagnosis: A subspecies of Neosemantis bjoerklundi characterized by relatively straight frontal and primary lateral spines which lie in the horizontal plane including the median bar.
Name: mimicus (Latin)—imitative.
Description: Skeleton consists only of cephalic elements and their associated spicules; no lattice shell. Frontal, apical and 2 primary lateral spines relatively straight, 35 to 95 µm long, irregularly sulcate, with profusions of spicules projecting from intervening ridges. Median bar short, circular in cross section. 7—10 (im in diameter; bears an obscure axobate on most specimens (pl. 3. figs. 2, 4, 5). Slender, simple, erect vertical spine 4-10µm long preserved on most specimens (pl. 3, figs. 1. 3-4, 9-10, 12). Simpler specimens (e. g., pl. 3, figs. 6, 8.11) have no other systematic structure, and 4 major spines are of equal length. Rare specimens have nodular spicules (pi. 3. fig. 7). Frontal spine shorter on other specimens, verticil of 2 or 3 long spicules project from distal third of apical and primary lateral spines (pl. 3, figs. 1-4, 10, 12). Two of the long spicules of each verticil are directed toward the other 2 major spines.
Holotype: USNM 253203. DSDP Hole 77B. core 26. section 6. 17-19 cm. England Finder T34/0; plate 3. figure 8.
Paratypes: USNM 253204. DSDP Hole 77B. core 28, section 5, 0-2 cm, England Finder A18/0; plate 3, figure 4. USNM 253205, DSDP Hole 77B. core 28. section 2. 35-37 cm. England Finder P31/3. plate 3. figure 1.
Remarks: Neosemantis bjoerklundi mimicus, n. subsp. is distinguished from Neosemantis bjoerklundi bjoerklundi in that the primary lateral spines are not broadly curved apically, and from Neosemantis distephanus in that the apical and primary lateral spines are not joined. Rarely, specimens of N. b. mimicus n. subsp., display a tendency toward fusion of the long spicules of adjacent verticils (pi. 3, fig. 2), but the major spines themselves are not joined. The spine system of N. b. mimicus, n. subsp., bears certain similarities to the major apophyses of Callimitra atavia, n. sp. The cephalic elements of C. atavia, n. sp., are slender and circular in cross section. These apophyses assume the massive, sulcate construction only exterior to the cephalic wall. In gross form, the skeleton of N. b. mimicus, n. subsp., resembles that of Plagiacantha arachnoides. but the construction of the spines is quite different. Moreover, the latter species has two fibrillar spine clusters on the primary lateral spines and no vertical spine.
Occurrence: At Site 77, Neosemantis bjoerklundi mimicus, n. subsp., is present in trace concentrations from core 29 [Stichocorys delmontensis Zone: Lower Miocene) to core 21 [Cannartus laticonus Zone, Middle Miocene).
Goll 1979


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