1086
Journal of Paleontology
Occurrence.—Early Cambrian, Yu’anshan Member, Chiung- chussu Formation, Eoredlichia-Wutingaspis Biozone, Yunnan Province, South China (Chen et al., 2003).
Remarks.—Analysis of the body shape of Didazoon, Poma- trum, and Yuyuanozoon distinguishes Yuyuanozoon as a sepa- rate genus based on its overall size and the proportions of the anterior and posterior sections, which were fully described by Chen et al. (2003). Yuyuanozoon is also clearly distinct fromother vetulicolians, with the exception of Didazoon, in possessing annulations within each segment of its posterior section.
Yuyuanozoon magnificissimi Chen, Feng, and Zhu in Chen et al., 2003
Figures 3, 4, 5, 6
2003 Yuyuanozoon magnificissimi Chen, Feng, and Zhu in Chen et al., p. 282, pl. 1, figs. a–d.
2004 Yuyuanozoon magnificissimi; Chen, p. 318, fig. 509.
2007 Yuyuanozoon magnificissimi; Aldridge et al., p. 142, pl. 5, figs. 3, 5, text-fig. 6.
2012 Yuyuanozoon magnificissimi; Ou et al., p. 81, fig. 5.
2017 Yuyuanozoon magnificissimi; Hou et al., p. 276, fig. 26.3.
Holotype.—CFM00059, deposited in the Chengjiang Fauna Museum, Chengjiang National Geological Park, Yunnan. The holotype was found on the northern slope of Maotianshan, Chengjiang (Chen et al., 2003).
Other material.—Three additional specimens from Ercaicun (see Hou et al., 2017, fig. 4.3): YKLP 13071, a nearly complete laterally preserved specimen; YKLP 13072, preserving most of the anterior section and part of the posterior section; and YKLP 13070, preserving most of the posterior section.
Diagnosis.—Monotypic, as for the genus.
Description.—The anterior section forms an elongated ellipsoid in lateral view, with five lateral pouches on each side; the anterior opening is broad (Fig. 3). The posterior section is about one-third of the width of the anterior section, elongate, seg- mented and annulated throughout. Narrow gut situated medially (Fig. 4.6, 4.8).
Body.—All specimens are laterally preserved. The most com- plete specimen YKLP 13071 (Fig. 3) has a length of at least 17.2cm (the last two segments of the posterior section are not preserved). The anterior section is 11.8cm long and up to 5.4cm wide; the posterior section is more than 4.5cm in length and has a maximum width of 2.0 cm. The dorsal surface of the anterior
Ordering lines.—Lines circumventing the anterior section and perpendicular to the body axis are displayed best in the anterodorsal area, and here they comprise two orders. The most prominent lines traverse the entire body. These delineate six subdivisions of the anterior section, and their boundaries are coincident with five lateral pouches on each side of the animal (Figs. 3, 5.1, 5.2). There are faint lines between these boundaries that are less continuous in the dorsal section. This pattern is similar to Vetulicola cuneata Hou, 1987 (Chen and Zhou, 1997, fig. 135) and V. rectangulata Luo and Hu in Luo et al., 1999 (Aldridge et al., 2007, pl.1, fig. 9; text-fig. 2) and is known in Pomatrum (Aldridge et al., 2007, pl. 5, fig. 1, text-fig. 8).
Lateral pouches.—The lateral pouches are one of the most prominent features of all vetulicolians and number five on each side of the anterior section. In the new specimens of Y. magnificissimi, the five pouches are cowl-shaped and form a series of lateral openings (Fig. 4.5). These pouches occur in the middle region of the dorsal and ventral sections of the anterior section and are similar to those in the holotype (Fig. 4.4). The lateral groove is absent in all specimens of Y. magnificissimi. The pouches show an orientation that may
have allowed water to exit the anterior section in a posteriorly flowing direction. No filaments are preserved in the new material.
Posterior segmentation.—Only five of up to seven segments in the posterior part are present in YKLP 13071, and within each of these segments are five to six annulations. Only a few
Figure 3. (1, 2) Lateral view of Yuyuanozoon magnificissimi YKLP 13071, anterior to left, dorsal to top. (1) Photograph of the fossil (largely the internal mold) with low-angle lighting; (2) camera lucida drawing of the same specimen. The six subdivisions of the anterior section are evident, as are the occurrence of secondary lines between these subdivisions. The ‘segmentation’ and ‘annulation’ of the posterior part of the body (which is incomplete posteriorly) are also evident. Ac=alimentary canal; Cv=circumventing feature behind the anterior opening; Lp1–Lp5=first through fifth lateral pouch; Mr=marginal region at the anterior opening; Ol=ordering lines; S1–S5=putative segments. (3, 4) Lateral view of anteriorly incomplete Yuyuanozoon magnificissimi YKLP 13071, anterior to right, dorsal to top. (3) Photograph of counterpart YKLP 13071 with low-angle lighting; (4) camera lucida drawing of counterpart. Lp=lateral pouches; Ol=the ordering lines. Scale bars=10mm.
section from the anterior opening to the posterior section is coincident along the dorsal side but has a concave outline on the ventral side (Fig. 3). The length of the posterior section measures 11mm for the first segment and then posteriorly
9mm, 9mm, 9mm, and at least 7mm for the incomplete fifth segment.
Anterior opening.—YKLP 13071 possesses a wide anterior opening (Figs. 3.1, 4.1) with a circumventing rim situated 5mm posterior of this. InYKLP 13072, the anterior section has a more quadrate shape than is typical, and the anterior opening is broad, but the circumventing feature is less well developed (Figs. 4.2, 5.1). No anterior opening has been detected in the holotype, but strongly developed wrinkles approximately parallel to the dorsal and ventral edge provide a hint that the anterior opening is not observable, owing to distortion through com- pression (Fig. 4.3).
Anterior circumventing feature.—Raised rim, a narrow struc- ture circumventing the entire perimeter of the anterior section, some 5mm posterior of the anterior opening.
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