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Davidonia rostratum
Taxonomy
Mackinnonia rostratum was named by Zhou and Xiao (1984). It is not a trace fossil. Its type locality is Huoqiu, Huainan, which is in an Atdabanian/Botomian carbonate limestone in the Yutaishan Formation of China.
Sister species lacking formal opinion data
Synonymy list
No taxonomic opinions are available
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If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.
†Davidonia rostratum Zhou and Xiao 1984
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Invalid names: Davidonia anhuiensis Zhou and Xiao 1984 [synonym], Davidonia costata Zhou and Xiao 1984 [synonym], Davidonia obliqua Landing and Bartowski 1996 [synonym], Mackinnonia davidi Bengtson et al. 1990 [synonym]
Diagnosis
| Reference | Diagnosis | |
|---|---|---|
| T. M. Claybourn et al. 2019 | Moderately high, cyrtoconic steinkerns, coiled through one-third of a whorl and moderately laterally compressed. Range 0.5–1.3 mm in length, 0.2–0.8 mm in height (see Table 1), and approximately 1.5 times longer than high. Protoconch reclined, rounded, rapidly expanding, and distinct from the teleoconch by change in microstructural imprints from smooth to polygonal. Strongly hooked apex directly above the parietal train or displaced up to one-quarter the length of the steinkern beyond the parietal train.
Supra-apical field evenly convex, subapical field short and concave; moderate rate of expansion. Apertural outline elongated elliptical, sometimes with short rounded parietal train separated by a distinct indent from the subapical field. Rounded parietal train tilts upward at an angle. In lateral view the aperture exhibits a convex profile. Transverse rugae subdued, not present on all Antarctic material but terminate before subapical field when present. Some small juvenile specimens lack rugae. Polygonal microstructural imprints (9–12 μm wide) are exhibited on the surface of the co-marginal rugae, with smooth furrows. The parietal train has pitted depressions on the steinkern surface (3–5 μmwide), and the protoconchs are smooth. |