Bushizheia yangi O’Flynn and Liu, 2020
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publication ID |
https://doi.org/ 10.26879/1069 |
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publication LSID |
lsid:zoobank.org:pub:A1DFE048-F763-4B75-9EF0-A20B9B8CD619 |
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persistent identifier |
https://treatment.plazi.org/id/03FAC70F-7E0B-FFC0-FCA8-67B3FECDFAAB |
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treatment provided by |
Felipe |
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scientific name |
Bushizheia yangi O’Flynn and Liu |
| status |
sp. nov. |
Bushizheia yangi O’Flynn and Liu , sp. nov.
Figures 1 View FIGURE 1 A-B, 2A-D, 3A-B, 4A zoobank.org/ 6809EBE1-DFB7-4D46-A24C-7F620FFA5FAD
Type material. Holotype YKLP 11421 ( Figure 1A View FIGURE 1 ) from the Cambrian, Series 2, Stage 3, Eoredlichia - Wutingaspis trilobite biozone, Nangoan Stage of regional Chinese usage, Yu’anshan Member, Chiungchussu Formation (Repository: YKLP).
Diagnosis. Euarthropod with a semi-circular head shield lacking dorsal compound eyes, eight thoracic tergites, and a large, semi-circular pygidium. Frontal head limbs circa 33% of body length, strong, composed of ≥ 12 podomeres, each with paired spines laterally.
Etymology. Yangi, after Mr Zhixin Yang, who recovered and prepared the fossil.
Description. Dorsal aspect of the head shield, trunk, and pygidium ( Figures 1 View FIGURE 1 A-B, 2C-D, 3A, 4A): Bushizheia yangi gen. et sp. nov. is circa 54 mm long. The habitus is sub-elliptical in dorsal aspect, with a length (anterior margin of the head shield to the posterior termination of the tailspine) of circa 250% of the width (maximum width in the anterior half of the body at the third and fourth tergites) ( Figures 1 View FIGURE 1 A-B, 4A). The length of the head shield is circa 20% of the total length. The trunk tapers from the fourth tergite backwards to a large pygidium (the tail shield of the exoskeleton covering the fused posterior segments of the body). The pygidium’s margin is spinose ( Figures 1 View FIGURE 1 A-B, 3A, 4A).
The head shield is a simple, semi-circular shield, with smoothly rounded posterolateral margins, and the length is circa 70% of its width.
The trunk consists of eight tergites. The anterior-most three tergites are virtually of equal length; the length is circa 20% of the width. Tergites 3-4 are widest; the width and length of tergites subsequently decrease posteriorly in width and length ( Figures 1 View FIGURE 1 A-B, 4A). Axially, the posterior border of each tergite overhangs the following tergite by circa 17% of its length, but by less abaxially. The first, second, and third tergites are reflexed anteriorly, whereas tergites posterior to that are transverse or reflexed posteriorly. The tergopleurae of the first and second tergites terminate bluntly posterolaterally. The tergopleurae of tergites 3-8 are extended into posterolateral projections ( Figures 1 View FIGURE 1 A-B, 4A).
The pygidium is a semi-circular shield and its length is circa 70% of its width; the margins bear eight paired short falcate spines, which curve very slightly posteriorly ( Figures 1 View FIGURE 1 A-B, 3A, 4A). The pleural regions of the pygidium’s anterior-most segment are effaced, but a transverse furrow is vis-
PALAEO- ELECTRONICA.ORG ible axially. The tailspine is sub-triangular and incompletely articulated; it is as wide as long, circa 8% of the total length, and circa 30% of the total length of the pygidium.
Appendages ( Figures 1 View FIGURE 1 A-B, 2A-D, 4A): The frontal head limbs reach a length of circa 33% of the total length of the body: 12 podomeres extend beyond the head shield, each with lateral endites that bear two inward facing setae, and terminal setae that are outward facing. Podomeres 2-7 are of equal length but decrease in width distally ( Figures 1 View FIGURE 1 A-B, 2A-B, 4A).
All visible post-frontal head limb appendages consist of either an endopod or an exopod. The one (incompletely) preserved endopod comprises four narrow podomeres ( Figures 1 View FIGURE 1 A-B, 3A). The two preserved exopods are paddle-shaped flaps, fringed with setae ( Figures 1 View FIGURE 1 A-B, 3B). Stein (2010), in his description of Kiisortoqia soperi , identified four cephalic appendiferous segments (a head incorporating the antennular plus three post-antennular limb-bearing segments), considered to be part of the ground pattern of Euarthropoda (Waloszek et al., 2007). The distal exopod of the anterior-most post-frontal head limb appendage of Bushizheia yangi gen. et sp. nov. appears beneath the head shield, and may, based on its position, be the fourth cephalic appendage. The limb immediately posterior of this, adjacent to the first trunk tergite, appears to be the first trunk appendage.
Remarks. Bushizheia yangi gen. et sp. nov. is dorsoventrally compressed and lies parallel to lamination; its well-articulated nature (i.e., tergites preserved attached, exopods preserved in situ). This state of preservation, especially the presence of articulated frontal head limbs, suggests limited post-mortem transportation: in, e.g., extant crustaceans, antennae can easily disarticulate (but see Allison, 1986). Compression wrinkles in the head shield that parallel its margin ( Figures 1 View FIGURE 1 A-B, 2A-D), suggest localised, weak sclerotisation. It is, therefore, presumed that the head shield was a simple, convex shield, sclerotised but without substantial biomineralization.
As a result of the state of preservation, not all podomeres of the frontal appendages are accessible for a straightforward description. The exact number of podomeres cannot be established; some are obscured by sediment. Lateral endites can be confirmed for at least podomeres 2-7, 9, 11, 12, and medial endites bearing two firm setae at their tips can be confirmed for at least 4, 5, 7, 11, and 12 ( Figure 2 View FIGURE 2 A-B). Rotation of podomere 2 evinces widely spaced double rows of endites ( Figures 1 View FIGURE 1 A-B, 2A).
Limbs with exopod setae are visible to the right of the two anterior-most thoracic tergites; the exopod of the posterior-most cephalic limb protrudes from beneath the head shield directly adjacent to the border of the head shield and first tergite, and is significantly rotated posteriorly, as is, albeit to a lesser extent the exopod of the first trunk limb. Only a single posteriorly situated endopod is, due to a degradation or complete absence of the overlying tergite, visible. No additional limbs were revealed by palaeontological techniques. The exact number of podomeres in the frontal appendages cannot be ascertained due to poor preservation of the distal-most ones. The proximal portions of the exopods are unavailable for description, so it cannot be established as to whether they were bipartite and divided into proximal and distal portions as in Leanchoilia illecebrosa (see Liu et al., 2007).
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.