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Micrina xiaofanensis
Taxonomy
Micrina xiaofanensis was named by Li and Xiao (2004). Its type specimen is NIGPAS-136140 (mitral sclerite) and is a 3D body fossil. Its type locality is Bed 17, Xiaotan Section, which is in a Meishucunian/Tommotian marine siltstone/dolomite in the Yu'anshan Formation of China.
Synonymy list
| Year | Name and author |
|---|---|
| 2004 | Micrina xiaofanensis Li and Xiao pp. 910 - 912 figs. 2.4–2.7, 6–8 |
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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.
†Micrina xiaofanensis Li and Xiao 2004
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Diagnosis
| Reference | Diagnosis | |
|---|---|---|
| G. Li and S. Xiao 2004 | Mitral sclerites subconical in lateral view. Apex rounded, smooth, and slightly curved addeltoidally to sit just above the deltoid area. Deltoid area gently convex. Perideltoid areas not well developed. Mitral teeth arise from the apical region, diverge and widen along the lateral-deltoidal slopes, and extend beyond the margin of the lateral slopes. Mitral sclerites have a well-defined apical region where pores and canals are absent. Sellate sclerite as for genus.
Sellate sclerites (Fig. 6) flattened and triangular, with an apical divergence angle of about 100–150 degrees. They are about 50 percent as long (apex to margin direction) as wide, with observed maximum width about 6 mm. Apex slightly rounded. Sella not developed. Abduplicature surface slightly convex in both horizontal and vertical directions. Duplicature well developed, occupying less than 50 percent of sclerite length and adpressed closely to the inner surface of the abduplicature (Fig. 6.2, 6.3). Mitral sclerites (Figs. 7, 8) bilaterally symmetrical, subcircular in apertural view, and subconical in lateral view. Aperture width 1–3 mm (measured in incomplete specimens), about 90 percent as long (deltoid to abdeltoid direction) as wide. Mitral sclerites 0.4–2.0 mm in height, about 40 percent as high as wide. Apex round and smooth, devoid of pores or canals (Fig. 7.4, 7.15). Apex slightly curved addeltoidally, but not beyond the apertural margin. Deltoid area slightly convex (convexity best seen in larger specimen) and expands from just beneath the apex to the two lateral slopes, forming an angle of about 110 degrees. Deltoid area does not expand outwardly as much as the other sides, and it is about 0.1–2.0 mm high, or 50 (small specimens) to nearly 100 percent (larger specimens) of the mitral height. Deltoid area flanked by shallow and narrow furrows, but no distinct perideltoid areas developed. Abdeltoidal slope moderately convex. Interior surface of mitral sclerite typically smooth, although unevenly distributed pores may be present occasionally (Fig. 8.4, 8.5); it is not clear whether these pores on the interior surface are also connected with canals. Teeth consist of several tubelike structures, best seen in broken specimens (Figs. 7.14, 8.1, 8.3). Transverse section of teeth is elliptical, while that of tubes subcircular. |
Measurements
No measurements are available
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| Source: p = phylum, uc = unranked clade | |||||
| References: Aberhan et al. 2004, Nesnidal et al. 2013 | |||||
Age range: base of the Meishucunian to the top of the Tommotian or 530.70000 to 521.00000 Ma
Collections (2 total)
| Time interval | Ma | Country or state | Original ID and collection number |
|---|---|---|---|
| Meishucunian - Tommotian | China (Yunnan) | Micrina xiaofanensis (type locality: 96302 96303) |