Fengzhengia, O’Flynn & Williams & Yu & Harvey & Liu, 2022
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publication ID |
https://doi.org/ 10.26879/1167 |
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publication LSID |
lsid:zoobank.org:pub:454132D3-421B-4F8F-ADB7-F9F629070902 |
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persistent identifier |
https://treatment.plazi.org/id/2B2787CB-FFE4-FFD3-CF2D-B534FD72FF17 |
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treatment provided by |
Felipe |
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scientific name |
Fengzhengia |
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Phylum Euarthropoda Lankester, 1904 Class, Order, and Family incertae sedis
Genus Fengzhengia new genus zoobank.org/ 3B72CDB4-5DE5-40AE-87B6-89B478FAAE63
Fengzhengia mamingae new species zoobank.org/ 302FEF94-956A-4743-BD44-E67DCF3D70FC
Figures 1 View FIGURE 1 A-C, 2A-C, 3A-C, 4A-C, 5A-J, 6A-C
Type species. Fengzhengia mamingae gen. et sp. nov., by monotypy.
Type material. Holotype, YKLP 11431 (part: Figures 1 View FIGURE 1 A-C, 2A-C, 3A-C, 5A, E-J, 6A-C; counterpart: Figures 4 View FIGURE 4 A-C, 5B-D) 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 possessing pair of upward-orientated frontal-most appendages, each consisting of stout shaft and distal articulated region composed of at least six podomeres, five of which clearly bear elongate triangular endites. Two anterior and no posterior stalked compound eyes. Head shield with rounded genal angles. Trunk consisting of 15 tergites — anterior-most nine bearing medial axial spines. Biramous trunk appendages with paddle-shaped exopods fringed with setae. Posterior shield-like structure merged from ≥ three somites articulated with tail fan.
Etymology. Genus name from Ņ⁂ fēngzhēng, Mandarin, kite, i.e., a quadrilateral whose four sides can be grouped into two pairs of equal-length sides that are adjacent to each other, with reference to the overall shape of the fossil. Species from ¼¾ Mă Míng, the wife of 杨 志 # Yáng Zhìxīn of Kunming, the man who recovered and prepared the fossil.
Description. Lateral aspect of the head shield, trunk, posterior shield-like structure, and tail fan ( Figures 1 View FIGURE 1 A-C, 5A, E-J, 6A-C; Table 1): the overall outline of Fengzhengia mamingae is sub-quadrilateral, making a kite-shape whose maximum length is circa 38 mm. It is laterally compressed, lies parallel to lamination, and is well-articulated, i.e., the tergites are preserved attached and the left eye is preserved in situ.
The head shield is simple and sub-triangular with a medial axial spine ( Figure 1 View FIGURE 1 A-C), smoothly rounded posterolateral margins, and its length, which is comparable to its width, is circa one-third of the total length of the body.
The trunk tapers very gently from the first and second tergites, which are of equivalent size, to the ninth tergite, each one of which possesses a medial axial spine. Tergites 10-15 are comparatively short and narrow: tergite 10 is characterised by an abrupt change in length and width compared to the preceding tergite (tergite 9). These short and narrow tergites, without medial axial spines, taper backward to a posterior shield-like structure to which a tail fan is attached. All tergites curve posteriorly ( Figure 3 View FIGURE 3 A-C).
The posterior shield-like structure ( Figure 6 View FIGURE 6 AC), is sub-triangular, appears to consist of at least three fused segments, and covers at least one putative endopod ( Figures 1C View FIGURE 1 , 6C View FIGURE 6 ) and two putative exopods ( Figures 1C View FIGURE 1 , 6C View FIGURE 6 ). Its length is circa two-thirds its width. The pleural regions of the shield’s anterior-most segment are effaced but a transverse furrow is visible axially.
The tail fan ( Figures 1 View FIGURE 1 A-C, 6A-C), attached to the posterior shield-like structure, is broad. It inserts at the end of the shield-like structure: one lateral terminus is visible (‘tf’ in Figure 6 View FIGURE 6 A-C). Its morphology, e.g., the posterior margin of the middle, cannot be described further because it is partly hidden underneath the matrix.
The frontal head limbs, with no clear terminus, reach a length of circa 16% of the total length of the body. They are upwardly curved and protrude from the ventral side of the head shield. The shaft is sub-rectangular, robust, and stout across its length. At least six podomeres, five of which bear a single endite per podomere with no auxiliary endites, taper distally. The length of each endite does not exceed the height of its podomere, which decrease in width distally. The frontal head limb, along which the endites alternate in length, is not situated close to the eyes but inserts circa one-third of the length of the head shield behind it.
Three trunk limbs, immediately posterior to the head shield, are concealed within the slab ( Figure 2 View FIGURE 2 A-C) and revealed by micro-CT ( Figure 3 View FIGURE 3 AC). Three paddle-shaped exopods that extend beyond the tergopleural termini ( Figure 3 View FIGURE 3 A-C), one per tergite, one putative endopod with four putative podomeres, and two putative podomeres in isolation ( Figures 1C View FIGURE 1 , 6C View FIGURE 6 ), are figured.
Indeterminate soft tissue ( Figure 1 View FIGURE 1 A-C): an indeterminate structure ( Figures 1 View FIGURE 1 A-C, 5G-H), which runs through the central portion of the body, might be a trace of the gut. Its maximum diameter is about 2.2 mm.
Remarks. Morphological features of Fengzhengia mamingae include body arthrodisation, limb biramy, and stalked compound eyes. The first and second are synapomorphies associated with Deuteropoda ( Ortega-Hernández, 2016, table 4).
Fengzhengia mamingae exhibits a stout, anteroventral grasping appendage that is superficially like the frontal appendage of radiodonts, megacheirans, isoxyids, and certain other euarthropods, e.g., Bushizheia yangi and Kiisortoqia soperi . The upward orientation of the appendages in F. mamingae is shared with megacheirans and Kylinxia zhangi (reviewed in Zeng et al., 2020) and those isoxyids with raptorial rather than antenniform frontal appendages, e.g., Isoxys ( Walcott, 1890) (see García-Bellido et al., 2009; Edgecombe, 2020). In contrast, the frontal appendages of radiodonts typically face downward, and typically bear a pivot joint ( Wu et al., 2021), dorsal spines ( Pates et al., 2021), and auxiliary enditic spines ( Zeng et al., 2020), none of which are evident in F. mamingae . The lack of dorsal spines on the frontal appendage also distinguishes F. mamingae from Bushizheia yangi (cf. O’Flynn et al., 2020, figure 2A-B).
The frontal appendage in Fengzhengia mamingae is constructed from at least six podomeres, whereas those of megacheirans typically consist of five podomeres, therefore F. mamingae is not a megacheiran sensu Aria et al. (2020). F. mamingae also lacks evidence for the characteristic elbow joint and chelate tip of megacheiran ‘great appendages’ (cf. Edgecombe and Legg, 2014). In contrast to Kylinxia zhangi , a recently described deuteropod with similarities to both radiodonts and megacheirans ( Zeng et al., 2020), the frontal appendage in F. mamingae exhibits a single rather than a double row of elongate triangular endites on the shaft and lacks auxiliary spines.
The head of Fengzhengia mamingae bears what appears to be a protuberance ( Figure 5I View FIGURE 5 ), which could represent the anterior sclerite from which large, stalked, sub-circular (far more circular than elliptical) eyes protrude anterolaterally, as observed in, e.g., Odaraia alata Walcott, 1911 (e.g., Briggs, 1981; Ortega-Hernández, 2015); the peduncles’ length (such as are visible laterally) is about equal to the eyes’ diameter. The eyes bear marginal rims that may represent a flattened lens or corneal layers ( Figures 1 View FIGURE 1 A-C, 5J).
The division of the trunk into an anterior series of nine broad tergites with medial axial spines, followed by a series of six comparatively narrow tergites that lack spines, resembles the thoracicabdominal subdivision of fuxianhuiids. Despite these apparent similarities, neither part nor counterpart exhibits a pair of antennae or a pair of specialised post-antennal appendages (Chen et al., 2020); therefore, it is not a fuxianhuiid sensu Chen et al. (2020).
We interpret the posterior shield-like structure, based on the conjoined segments posterior to the last trunk articulation ( Hughes et al., 2006) in Fengzhengia mamingae as a pygidium sensu Cotton and Braddy (2004), i.e., a posterior tagma consisting of several fused segments under a single tergite, which may or may not incorporate the postsegmental telson. Fengzhengia mamingae also shows a putative endopod attached to its posterior shield-like structure ( Figure 6 View FIGURE 6 A-C). A pygidium similar to the posterior shield-like structure in F. mamingae is also present in Bushizheia yangi ( O’Flynn et al., 2020) , and the recently described stem mandibulate bivalved arthropod, Pakucaris apatis Izquierdo-López and Caron, 2021 . If the posterior shield of F. mamingae is a pygidium, it adds to a growing number of pygidium-bearing arthropods and supports a phylogenetic scenario in which a pygidium is not synapomorphic for a clade composed of xandarellids, naraoiids, helmetiids, tegopeltids, and trilobites, but rather is plesiomorphic, with the structure being retained in certain groups (e.g., B. yangi , F. mamingae , and Artiopoda; discussed in O’Flynn et al., 2020; Izquierdo-López and Caron, 2021).
Fengzhengia mamingae resembles Kylinxia zhangi ( Zeng et al., 2020) in having a subtriangular head shield with rounded genal angles; large, stalked compound eyes extending from under the head shield, which bear marginal rims; possibly also a pygidium merged from ≥ three somites articulated with a tail fan. However, there are further, significant morphological differences: (1) F. mamingae has 15 trunk tergites, of which the first nine are broad with medial spines, and the remaining six are narrow without spines, whereas K. zhangi has as many as 25 trunk tergites, which do not contrast in size; (2) the trilobation of tergites is effaced in F. mamingae , but prominent in K. zhangi ; and (3) F. mamingae has no posterior stalked compound eyes on the head, whereas K. zhangi has two anterior and three posterior stalked compound eyes on the head ( Zeng et al., 2020, figure 3).
In terms of preservation, Fengzhengia mamingae is laterally compressed, lies parallel to lamination, and is well-articulated, i.e., its tergites are preserved attached and its eyes are preserved in situ. This state of preservation suggests limited post-mortem transportation (e.g., Shu et al., 1999). Compression wrinkles in the head shield and tail fan suggest localised, weak sclerotisation.
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.