Anomalocarididae Raymond, 1935

Jiao, De-Guang, Pates, Stephen, Lerosey-Aubril, Rudy, Ortega-Hernández, Javier, Yang, Jie, Lan, Tian & Zhang, Xi-Guang, 2021, The endemic radiodonts of the Cambrian Stage 4 Guanshan Biota of South China, Acta Palaeontologica Polonica 66 (2), pp. 255-274 : 263-267

Family Anomalocarididae Raymond, 1935

Type genus: Anomalocaris Whiteaves, 1892 .

Genera included: Type genus and Paranomalocaris Wang, Huang, and Hu, 2013 .

Remarks.— Paranomalocaris was originally described as a monospecific genus within the family Anomalocarididae . All phylogenetic analyses attempting to resolve the internal relationships of radiodonts to date have failed to resolve the family Anomalocarididae or even genus Anomalocaris (even excluding “ Anomalocaris ” briggsi and “ Anomalocaris ” kunmingensis which are not considered members of the genus) as a monophyletic group. Analyses either returned a paraphyletic grade towards monophyletic Amplectobeluidae , or a polytomy with the latter group (e.g., Cong et al. 2014; Vinther et al. 2014; Van Roy et al. 2015; Lerosey-Aubril and Pates 2018; Moysiuk and Caron 2019). Only Liu et al. (2018) retrieved a clade Anomalocarididae ( A. kunmingensis and A. briggsi excluded) in one of their analyses, which recovered Paranomalocaris as sister to a clade uniting Anomalocarididae to Amplectobeluidae . In summary, there is no strong phylogenetic support for assigning Paranomalocaris to Anomalocarididae , but this is also the case of all the species of Anomalocaris . Future work may support the erection of a distinct family for Paranomalocaris , but for now we retain this genus within the family as originally described.

Genus Paranomalocaris Wang, Huang, and Hu, 2013

Type species: Paranomalocaris multisegmentalis Wang, Huang, and Hu, 2013 ; Gaoloufang Village, Kunming, Yunnan, China, Wulongqing Formation ( Palaeolenus and Megapalaeolenus zones), Cambrian (Stage 4).

Diagnosis (emended from Wang et al. 2013).—Radiodont with slender frontal appendages, which comprise at least 17 podomeres; proximal podomeres have a tall rectangular lateral outline, which changes to approximately square distally; endites alternate long/short on subsequent podomeres, and reduce in length along the appendage; small triangular terminal spine on distalmost podomere.

Paranomalocaris multisegmentalis Wang, Huang, and Hu, 2013 Fig. 5.

2013 Paranomalocaris multisegmentalis sp. nov.; Wang et al. 2013: 3940, figs. 2, 3.

2013 Paranomalocaris multisegmentalis Wang et al. 2013 ; Hu et al. 2013: 137, 192, fig. 181.

2014 Paranomalocaris multisegmentalis Wang et al. 2013 ; Cong et al. 2014: ext. data fig. 4.

2014 Paranomalocaris multisegmentalis Wang et al. 2013 ; Vinther et al. 2014: fig. 3.

2015 Paranomalocaris multisegmentalis Wang et al. 2013 ; Van Roy et al. 2015: ext. data fig. 10.

2018 Paranomalocaris multisegmentalis Wang et al. 2013 ; Lerosey-Aubril and Pates 2018: fig. 2, sup. figs. 4, 5.

2018 Paranomalocaris multisegmentalis Wang et al. 2013 ; Liu et al. 2018: sup. fig. 2.

2018 Paranomalocaris multisegmentalis Wang et al. 2013 ; Zeng et al. 2018a: 41, 42, 46.

Holotype: NIGP154564 , an incomplete frontal appendage compressed laterally ( Wang et al. 2013).

Type localit y: Gaoloufang village, Kunming, East Yunnan, China

( Wang et al. 2013).

Type horizon: Wulongqing Formation ( Palaeolenus and Megapalaeolenus Zone ), Cambrian (Series 2, Stage 4) ( Wang et al. 2013).

Material.— Type material and YKLP 12416 , a partial frontal appendage compressed laterally from Lihuazhuang section, near Lihua village , about seven kilometres northwest of the Yiliang county in Yunnan, China ( Fig. 1 ), Cambrian (Stage 4), lower part of Wulongqing Formation, Palaeolenus Biozone ( Hu et al. 2010b) .

Diagnosis (emended from Wang et al. 2013).— Paranomalocaris with short, plate-like proximal endites, each bearing a spiniform termination and at least three distally facing auxiliary spines; serrated dorsal spines.

Description.— YKLP 12416 is incomplete proximally, consists of 15 podomeres (Fig. 5: pd1–15) and a terminal spine, and measures 45 mm along the dorsal margin. The appendage curves ventrally with a slight dorsal kink visible at the midpoint of the second podomere (Fig. 5A 1). Most podomeres are approximately square shaped, being slightly taller than long in the proximal part and slightly longer than tall towards the middle, except for the four distal ones that are notably taller than long. Endites are present on every podomere (Fig. 5A 2: en). No second row of endites is observed. On pd1, the endites are not well preserved. A single outgrowth from the ventral surface close to the proximal margin might represent a broken endite base (Fig. 5A 2: en1) orientated towards the proximal part of the appendage. The endite on pd2 is broadly rectangular in outline (3 × 1 mm), with an incomplete spiniform termination, and bears three auxiliary spines on its distal margin (Fig. 5A 3). En3, the longest endite (Fig. 5A 2), measures c. 4.5 mm from base to tip, and is also rectangular in outline, except for a robust spiniform termination that slightly curves towards the distal portion of the appendage. Three robust and elongate auxiliary spines radiate ventro-distally from the middle third of the distal margin of en3, and a single, much smaller one project from its proximal margin (Fig. 5A 3). En4 is much smaller than En3, but exhibits similar shape and distribution pattern of auxiliary spines. En5–11 bear three to six auxiliary spines on both margins, which follow a mostly pectinate arrangement and project at an angle of c. 130° (distal ones) or c. 150° (proximal ones) with the long axes of the endites (Fig. 5A 3). The size of the spiniform termination relative to the rest of the endite tends to decrease from en4–11. The preservation of en12–15 is poorer, but en13–15 appear to be short, project distally, and devoid of auxiliary spines. A small dorsal spine may occur on pd14, and a single, robust terminal spine is visible on pd15 (Fig. 5A 2: ds, ts).

Remarks.—While the broad shape of en3–11 and their pattern of numerous distal and proximal facing auxiliary spines bear similarity to both Paranomalocaris multisegmentalis and Ramskoeldia platyacantha, the relative length and morphology of en2–7 provide strong support for the interpretation of this specimen as the distal 15 podomeres of a P. multisegmentalis appendage.

The alternation in size of the endites of adjacent podomeres and their overall reduction in length along the appendage are characters known in all anomalocaridids. While members of the Anomalocaris have 13 podomeres in the distal articulated region, all 15 podomeres of the new specimen are considered to belong to the distal articulated region, a number only known in the Paranomalocaris and Tamisiocaris ( Daley and Peel 2010; Wang et al. 2013; Vinther et al. 2014). Affinities with the latter genus can be discarded, as endites of Tamisiocaris are all of subequal length, a character that currently distinguishes Tamisiocarididae from Amplectobeluidae and Anomalocarididae .

Under a hypothesis that would interpret this specimen as Ramskoeldia platyacantha, the distal 13 podomeres of YKLP 12416 would represent the distal articulated region, with pd1 and pd2 comprising the shaft. The slight dorsal kink in pd2 could be interpreted as supporting this arrangement, however its presence within a podomere, rather than at the boundary of two adjacent podomeres, suggests that this feature is due to a slight twist of the appendage during compression and does not represent a biological feature. Two further observations allow us to reject the assignment of this specimen to R. platyacantha, in favour of Paranomalocaris . Firstly, the endites decrease in length along the whole appendage with no exception, while an en7 longer than en5 characterizes the amplectobeluid genera Amplectobelua and Ramskoeldia. Secondly, the distalmost shaft podomere bears a small and simple spiniform endite at its distal margin in R. platyacantha, while the specimen described herein would exhibit an elongate endite with auxiliary spines at this position (Fig. 5: en2), if interpreted as a sub-complete appendage of this species. For the specimen under consideration, en2 is smaller than, but morphologically similar to en3, as would be expected from the endites of adjacent podomeres in the distal articulated region of Paranomalocaris .

Some characters diagnostic for Paranomalocaris multisegmentalis cannot be observed in YKLP 12416. The serrated appearance of the distal dorsal margin of the holotype appendage, resulting from the presence of half a dozen dorsal spines, is not observed in the new specimen due to the poor preservation/incomplete exposition of this part of the fossil. Likewise, the proximal part is missing in the new specimen, which therefore only preserves 15 podomeres, whereas Wang et al. (2013) described the holotype specimen to possess “at least 22 podomeres”. We can confirm at least 17 podomeres from the figured specimen ( Wang et al. 2013: figs. 2, 3), but since this previously illustrated specimen is clearly incomplete, a higher podomere number must characterize the genus Paranomalocaris . Of note, YKLP 12416 shows that the proximal endites (Fig. 5: en2, en3) differ from the more distal ones in having a single proximally facing auxiliary spine each (rather than multiple ones), a detail that could not be observed in the holotype due to preservation.

Stratigraphic and geographic range.—Gaoloufang village and Lihuazhuang section, Yunnan, China, Wulongqing Formation ( Palaeolenus and Megapalaeolenus zones), Cambrian (Stage 4).

Paranomalocaris simplex sp. nov.

Fig. 6 .

Zoobank LCID: urn:lsid:zoobank.org:act:F79695F0-AF05-4A3A-B326-A6516936F3B2

Etymology: From Latin simplex , simple; emphasising the simple morphology of endites and dorsal spines in the new species, which contrast to the complex endites and serrated dorsal spines of the type species.

Type material: Holotype: YKLP 12417 , a laterally compressed frontal appendage; paratype: YKLP 12418 a, a partial laterally compressed frontal appendage from the type locality.

Type locality: Lihuazhuang section, locality c. 2.5 km southeast of the Lihua village, China ( Fig. 1 ).

Type horizon: Lower part of Wulongqing Formation, Palaeolenus Biozone, Cambrian (Stage 4) ( Hu et al. 2010b).

Material.— Type material only.

Diagnosis.— Paranomalocaris with long needle-like endites, some exceeding in length the height of the podomere to which they attach; non-serrated dorsal spines present on every podomere.

→ Fig. 5. Anomalocaridid radiodont Paranomalocaris multisegmentalis Wang, Huang, and Hu, 2013 , from the Cambrian (Stage 4) Guanshan Biota, Lihuazhuang section, Yunnan, China. YKLP 12416 , incomplete frontal appendage (proximalmost region missing); general view (A 1), white arrow indicates fold in dorsal margin; details of the proximal preserved endites (A 2, A 3), white arrows, distally facing auxiliary spines; black arrows, proximally facing auxiliary spines. Photographs (A 1, A 3) and explanatory drawing (A 2). Abbreviations: ds, dorsal spine; en, endite; pd, podomere; ts, terminal spine .

Description. —Two isolated near-complete frontal appendages laterally compressed ( YKLP 12417, 12418a) measuring 32 mm and 33 mm along the dorsal margin, respectively ( Fig. 6 ). At least 20 podomeres can be identified for each appendage, changing in lateral outline from tall rectangles proximally to square shapes distally ( Fig. 6 : pd). Podomeres can be identified from their boundaries, visible as simple lines on the surface of the appendage, and/or from the pair of endites projecting ventrally.

Both specimens bear needle-like endites, one pair per podomere, which reduce in length toward the distal tip of the appendage, and alternate long/short on adjacent podomeres ( Fig. 6 : en). In the holotype (YKLP 12417; Fig. 6A ), thin and short auxiliary spines might occur on the distal margin, at an angle of c. 140° with the long axis, on some endites. Other endites appear to lack auxiliary spines. No auxiliary spines are visible on any endites of the paratype ( Fig. 6B ). Dorsal spines are visible on every podomere in the holotype, either as spines in its distal third ( Fig. 6A 2 : ds) or as circular attachment points in its more proximal region ( Fig. 6A 2 : c). A single spine in the distal region of YKLP 12418a may be a dorsal spine, but most of the dorsal surface of this specimen is poorly preserved. One small and curved terminal spine is visible on each specimen ( Fig. 6 : ts).

Remarks.—The type species and hitherto only species of Paranomalocaris , namely Paranomalocaris multisegmentalis , was distinguished from other members of Anomalocarididae by its high number of podomeres, the morphology of its proximal endites (plate-like and bearing at least five auxiliary spines on both proximal and distal margins), and the presence of serrated dorsal spines.

Among radiodonts only Paranomalocaris and Tamisiocaris possess such a high number of podomeres in the distal articulated region. As discussed above, this feature is combined with an alternation in endite length along the appendage only in Paranomalocaris , allowing a confident assignment of the new taxon to this genus. Paranomalocaris simplex can be easily differentiated from P. multisegmentalis by the slender morphology of its endites, and the absence of serration on the dorsal spines.

Stratigraphic and geographic range.—Lihuazhuang section, Yiliang county, Yunnan, China, Wulongqing Formation ( Palaeolenus Biozone ), Cambrian (Stage 4).

Figures

Fig. 1. A. Map of China showing location of the studied area. B. Map showing thirteen sites where fossil assemblages assigned to the Cambrian (Stage 4) Guanshan biota have been found: 1, Dahai (Liu et al. 2012); 2, Shijiangjun (Luo et al. 2008); 3, Xinlongcun (Liu et al. 2016); 4, Wulongqing (Luo et al. 2008); 5, Kanfuqing (Chen et al. 2019); 6, Baimei (Liu et al. 2016); 7, Qiongzhusi (Luo et al. 2008); 9, Dabanqiao (Luo et al. 2008); 10, Changchunshan (Zhao et al. 2020); 11, Gaoloufang (Luo et al. 2008; Hu et al. 2010); 12, Chenggongxincheng (Hu et al. 2013); 13, Lihuazhuang (Jiao et al. 2016; this study). C. The location of the Lihuazhuang section in (asterisk). D. Stratigraphic column showing the occurrence of the fossils reported in this study.

Fig. 6. Anomalocaridid radiodont Paranomalocaris simplex sp. nov. from the Cambrian (Stage 4) Guanshan Biota, Lihuazhuang section, Yunnan, China. A. YKLP 12417, a near complete frontal appendage. B. YKLP 12418, distal portion of a frontal appendage. Photographs (A1, B1) and explanatory drawings (A2, B2). Abbreviations: c, circular attachment point for dorsal spine; ds, dorsal spine; en, endite; pd, podomere; ts, terminal spine.

Fig.2.Amplectobeluid radiodont “Anomalocaris” kunmingensis Wang, Huang, and Hu, 2013, from the Cambrian (Stage 4) Guanshan Biota, Lihuazhuang section, Yunnan, China.YKLP 12414, a pair of frontal appendages and associated oral cone.Abbreviations: la, left appendage; oc, oral cone; om, organic matter; ra, right appendage; w, ecdysozoan worm.