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Journal of Paleontology 91(3):493–511
Figure 7. Camera-lucida drawings of elements in the Iowagnathus grandis n. gen. n. sp. apparatus: (1)S0 element, SUI 139894 (W18-246); (2)S1 element, SUI 139904 (WS15-342); (3)S2 element, SUI 139898A (WS13-656A); (4)S3 element, SUI 139898C (WS13-656C); (5)S4 element, SUI 139905 (WS17-296), note that this specimen is illustrated in posterior view with a hidden anterior process as a rectangular extension from the cusp; (6)P1 element, SUI 139899 (WS16-80); (7)P2 element, SUI 139900 (WS14-553); (8) M element, SUI 139901 (WS11-342). Scale bars = 2mm.
element, but the former lacks a third process. The M elements differ from others by their obviously asymmetrical morphology and smaller element size (Figs. 7.8, 8.17). Also, as indicated in
Figure 5 and schematically illustrated in Figures 6 and 9.2, the paired M elements are always located at one end of its apparatus.
Figure 8. Illustrations of individual elements showing typical element morphologies and microstructures of Archeognathus primus (1–6) and Iowagnathus grandis n. gen. n. sp. (7–19): (1)P1 element of A. primus with a centrally placed wide downward projection (“handle”) from the basal body; SUI 139889 (WS12-251); scale bar = 1mm; (2, 3)P2 elements of A. primus with a narrower downward projection placed near the end of the element; in the element illustrated in Figure 8.3, the amber denticle color has faded to white, and most of the basal body has been dissolved leaving only a carbon film; SUI 139885 (WS12-382) and SUI 139890 (WL58), respectively; scale bar = 1mm; (4) saw-blade like S element of A. primus with the basal body having a short “ear-like” extension near the end of the element, which is marked by a red arrow; SUI 139891 (WS16-386); scale bar = 2mm; (5) thin section of a denticle of A. primus showing compact growth lamellae; SUI 139892 (WL211); scale bar = 100 µm; (6) thin section of basal body of A. primus showing thick undulate lamellae; SUI 139893 (WL225); scale bar = 100 µm; (7–9)S0 elements (only the lower one in 8 and 9) showing variations in the element morphology of I. grandis n. sp.; SUI 139894 (WS18-246), SUI 139895 (WS13-1), and SUI 139896 (WS18-265), respectively; scale bar = 2mm in (7) and (8), 1mm in (9); (10) color-faded denticle with fibrous lamellae, which are indicated by white arrows; sample SUI 102854; scale bar = 100 µm; (11)S1 element of I. grandis n. sp. with nearly symmetrically placed lateral processes and large, distinctly ornamented basal body; SUI 139897 (WS16-235); scale bar = 1mm; (12)S2 element of I. grandis n. sp. with a slightly curved anterior process; SUI 139898A (WS13-656A); scale bar = 1mm; (13)P1 element of I. grandis n. sp. with symmetrical lateral processes, prominent anterior cusp, and large, strongly ornamented basal body; SUI 139899 (WS16-80); scale bar = 1mm; (14) posterior view of S element of I. grandis n. sp. with uniformly long denticulated processes and reclined cusp; SUI 139905 (WS17-296); scale bar = 1mm; (15)P2 element of I. grandis n. sp. with short and approximately uniform processes and a long reclined cusp; SUI 139900 (WS14-553); scale bar = 1mm; (16)S3 element of I. grandis n. sp. with prominent, slightly curved, anterior process; SUI 139898C (WS13-656C); scale bar = 1mm; (17) M element of I. grandis n. sp. with asymmetrical lateral processes and prominent cusp; SUI 139901 (WS11-342); scale bar = 1mm; (18) thin section of a denticle of I. grandis n. sp. showing very thin growth lamellae; SUI 139902 (WS13-587); scale bar = 100 µm; (19) thin section of basal body of I. grandis n. sp. illustrating relatively thick undulating lamellae; SUI 139903 (WL208); scale bar = 100 µm.
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