Anomalocaris daleyae, Paterson & Garćıa-Bellid & Edgecomb, 2023

Paterson, John R., Garc ́ ıa-Bellid, Diego C. & Edgecomb, Gregory D., 2023, The early Cambrian Emu Bay Shale radiodonts revisited: morphology and systematics, Journal of Systematic Palaeontology (2225066) 21 (1), pp. 1-29 : 4-12

publication ID	https://doi.org/ 10.1080/14772019.2023.2225066
publication LSID	lsid:zoobank.org:pub:AEFDB294-AE8F-426D-9805-FC701798A986
DOI	https://doi.org/10.5281/zenodo.10987554
persistent identifier	https://treatment.plazi.org/id/4A7969A5-C180-454D-9DC4-42FAC9714F8F
taxon LSID	lsid:zoobank.org:act:4A7969A5-C180-454D-9DC4-42FAC9714F8F
treatment provided by	Felipe
scientific name	Anomalocaris daleyae
status	sp. nov.

Treatment

Anomalocaris daleyae sp. nov.

( Figs 2–7A, B View Figure 2 View Figure 3 View Figure 4 View Figure 5 View Figure 6 View Figure 7 )

1995 Anomalocaris sp. ; Nedin: 33–36, figs 2, 3B.

1997 Anomalocaris sp. ; Nedin: 134.

1999 Anomalocaris sp. ; Nedin: 989.

2006 Anomalocaris sp. ; Paterson and Jago: 43.

2011 Anomalocaris sp. nov.; Paterson, Garćıa-Bellido, Lee, Brock, Jago, and Edgecombe: 237–240, figs 1, 2, SI fig. 1a–e.

2013 Anomalocaris cf. canadensis Whiteaves ; Daley, Paterson, Edgecombe, Garćıa-Bellido, and Jago: 973, 975–977, fig. 3.

2014 Anomalocaris sp. Emu Bay; Vinther, Stein, Longrich, and Harper: 498.

2014 Anomalocaris cf. canadensis Whiteaves ; Lerosey-Aubril, Hegna, Babcock, Bonino, and Kier: 274–275.

2014 Anomalocaris cf. canadensis Whiteaves ; Cong, Ma, Hou, Edgecombe, and Strausfeld: ext. data fig. 4.

2015 Anomalocaris cf. canadensis Whiteaves ; Van Roy, Daley, and Briggs: ext. data fig. 10.

2016 Anomalocaris cf. canadensis Whiteaves ; Paterson, Garćıa-Bellido, Jago, Gehling, Lee, and Edgecombe: 3–5, figs 3j, k, 4c, d.

2016 Anomalocaris cf. canadensis Whiteaves ; Jago, Garćıa-Bellido, and Gehling: 549.

2017 Anomalocaris cf. canadensis Whiteaves ; Pates and Daley: 468.

2018 Anomalocaris sp. A (Emu Bay); Lerosey-Aubril and Pates: 4.

2019 Anomalocaris cf. canadensis Whiteaves ; Guo, Pates, Cong, Daley, Edgecombe, Chen, and Hou: 105–106.

2020 Anomalocaris aff. canadensis Whiteaves ; Paterson, Edgecombe, and Garćıa-Bellido: 1, 2, 5, 6–8, figs 4, 5C, D.

2021 Anomalocaris cf. canadensis Whiteaves ; Pates, Daley, Edgecombe, Cong, and Lieberman: 258.

2021 Anomalocaris cf. canadensis Whiteaves ; Wu, Ma, Lin, Sun, Zhang, and Fu: 3, 6–10.

2021 Anomalocaris cf. canadensis Whiteaves ; Wu, Fu, Ma, Lin, Sun, and Zhang: 215.

2021 Anomalocaris cf. canadensis Whiteaves ; Jiao, Lerosey-Aubril, Ortega-Herńandez, Yang, Lan, and Zhang: 269, 271.

2022 Anomalocaris aff. canadensis Whiteaves ; Bicknell, Holmes, Pates, Garćıa-Bellido, and Paterson: 13.

2023 Anomalocaris aff. canadensis Whiteaves ; Zeng, Zhao, and Zhu: 14, 15.

2023 Anomalocaris aff. canadensis Whiteaves ; Potin and Daley: 11, 16, fig. 6F–H.

Diagnosis. Base endite of frontal appendage 80% height of associated podomere; pair of tiny auxiliary spines on base endite. Proximal portion of claw endites 1, 3, 5 and 7 relatively robust; En1 with three pairs of auxiliary spines; En3 with two pairs of auxiliary spines; En5 and 7 with two posterior auxiliary spines. Cp 9–13 with well-developed dorsal spines; Cp13 with terminal spine of roughly equal length to dorsal spine.

Derivation of name. For Allison Daley, in recognition of her impressive work on radiodonts, including Emu Bay Shale taxa.

Holotype. SAMA P51398 View Materials ; pair of frontal appendages and associated oral cone ( Figs 2 View Figure 2 , 3 View Figure 3 ) from level 10.9 in Buck Quarry (35 ǫ 34 Į 25 ʺ S, 137 ǫ 34 Į 36 ʺ E), Big Gully, Kangaroo Island, South Australia. Previously illustrated by Paterson et al. (2016, fig. 3j, k).

Paratypes. Frontal appendages: SAMA P15374 ( Fig. 6A, B View Figure 6 ; En1 previously illustrated by Daley, Paterson et al. 2013, fig. 3E), P40807 (previously illustrated by Nedin, 1995, fig. 2 A and Daley, Paterson et al., 2013, fig. 3A–D), P42037 (previously illustrated by Daley, Paterson et al., 2013, fig. 3F–H), P54844 ( Fig. 4 View Figure 4 ; pair of frontal appendages and associated oral cone), and P55619 ( Fig. 5 View Figure 5 ).

Additional material. Frontal appendages: SAMA P54915 ( Fig. 6C View Figure 6 ), in addition to other specimens listed by Daley, Paterson et al. (2013, supp. information) and Paterson et al. (2020, table S4) as ‘ cf. canadensis ’ or ‘ aff. canadensis ’, respectively. Oral cones: SAMA P54874 ( Fig. 6D, E View Figure 6 ), in addition to P54255 and P54799. Compound eye specimens are listed by Paterson et al. (2020, table S3) as ‘ Anomalocaris -type’.

Description. Frontal appendages are Ĺ 183 mm in length along the dorsal margin ( Daley, Paterson et al., 2013), consisting of a non-segmented base and a claw of 13 podomeres (Cp1–13). The single podomere of the base is rectangular (length:height is ~1.8) and at least twice as long as the adjacent podomere (Cp1), without a conspicuous dorsal kink at the articulation of the base and Cp1 ( Figs 2–4 View Figure 2 View Figure 3 View Figure 4 ). The base endite located at the distal corner is relatively long (length ~80% the height of the associated podomere) and has a single, tiny pair of auxiliary spines situated about two-thirds of the way from its base ( Figs 2 View Figure 2 , 6A, B View Figure 6 ). Claw podomeres have a trapezoidal outline in lateral view (observed Cp1–Cp11 length:height ratios range from ~0.6 to 0.7), with dorsal margins longer than ventral margins, and the overall size of podomeres gradually decreasing distally. The proximal margin of each podomere is relatively straight, and the distal margin is slightly sinuous. Arthrodial membrane is preserved as recessive triangular regions between podomeres in outstretched frontal appendages (e.g. Fig. 2 View Figure 2 ). Claw endites are paired (e.g. Figs 2 View Figure 2 , 5 View Figure 5 ) and alternate in length to at least En9, with odd-numbered endites (En1, En3, and so on) being longer than adjacent, even-numbered endites; all endites project anteriorly to varying degrees, with the angle between the endite and the anteroventral margin of the podomere becoming more acute towards the distal end of the claw, shifting abruptly at En9. En1 is enlarged, slightly curved anteriorly, length is ~95% the height of the podomere, and bears three spikey auxiliary spines on both the anterior and posterior margins arranged in pairs, with each pair becoming longer towards the ventral tip of the endite ( Figs 2 View Figure 2 , 3A View Figure 3 , 4A, B, 6A, B; Daley, Paterson et al., 2013, fig. 3F–H). En2 length is ~50% the height of the podomere, with one small pair of auxiliary spines ( Figs 2 View Figure 2 , 4A, B View Figure 4 ). En3 is stout, slightly curved anteriorly, length is ~75% the height of the podomere, bearing two pairs of auxiliary spines (one variably unexposed on either anterior or posterior margin), with each pair becoming longer towards the ventral tip of the endite ( Figs 2 View Figure 2 , 3B View Figure 3 , 4, 5; Daley, Paterson et al., 2013, fig. 3D). En4 length is ~40% the height of the podomere, with one small pair of auxiliary spines ( Figs 2 View Figure 2 , 4 View Figure 4 ). En5 and En7 are stout, slightly curved anteriorly, lengths are ~60–65% the height of the podomeres, each bearing two auxiliary spines on the posterior margin and one auxiliary spine on the anterior margin ( Figs 2 View Figure 2 , 4 View Figure 4 , 5 View Figure 5 ). En6 and En8 lengths are ~25–40% the height of the podomeres, with no apparent auxiliary spines ( Figs 2 View Figure 2 , 5 View Figure 5 ), or with a single pair of auxiliary spines on En 6 in SAMA P54844 ( Fig. 4 View Figure 4 ). En9 length is ~70% the height of the podomere, with the angle between the endite and the ventral margin of the podomere being ~40 ǫ, and without auxiliary spines ( Figs 2 View Figure 2 , 5 View Figure 5 ; Daley, Paterson et al., 2013, fig. 3A, B). En10 and En11 are poorly preserved in available specimens. Dorsal spines are present on Cp7–13, with those on Cp7 and Cp8 being very short, and those on Cp9–13 being very long (i.e. of equal or greater length than the dorsal margin of the associated podomere) and have a sickleblade-like outline ( Figs 2 View Figure 2 , 3D View Figure 3 , 4, 5A, B, 6A–C; Daley, Paterson et al., 2013, fig. 3A, B, G, H). The distal-most podomere (Cp13) largely consists of the dorsal spine paired with an elongate terminal spine of roughly equal length, the two diverging at ~35 ǫ ( Figs 2 View Figure 2 , 3D View Figure 3 ).

The compound eyes of Anomalocaris daleyae sp. nov. have been previously described in detail by Paterson et al. (2011, 2020) and this will not be reiterated here.

The oral cone is sub-circular in outline, reaching a diameter of ~ 50 mm in available specimens. It has a triradial symmetry, with three large plates separated by medium- and small-sized plates, and a small central opening. The large plates are oriented ~110–125 ǫ from each other, of roughly equal size, and have subparallel margins ( Figs 2, 3E View Figure 3 View Figure 2 ); one large plate appears to align with the anterior-posterior axis of the head based on two assemblages of paired frontal appendages and the oral cone apparently in situ ( Figs 2 View Figure 2 , 4A, B View Figure 4 ). Medium- and small-sized plates tend to alternate and exhibit folds in their outer portions towards the oral cone margin, with up to eight medium plates in each sector ( Figs 2, 3E View Figure 3 View Figure 2 , 6D, E). Teeth on the inner margins of plates are not clearly preserved in the available specimens. The large and medium-sized plates exhibit nodes that tend to be clustered on the inner portions of the plates, with as many as 12 nodes on large plates ( Figs 2, 3E View Figure 3 View Figure 2 , 6D, E). The nodes have an asymmetrical surface profile, with the raised tips directed towards the centre of the oral cone. The remainder of the oral cone surface appears to be smooth. The somewhat distorted preservation of specimen SAMA P54874 View Materials ( Fig. 6D, E View Figure 6 ) suggests that the oral cone was a pliable structure. Based on the holotype ( SAMA P51398 View Materials , Fig. 2 View Figure 2 ), the ratio of frontal appendage length to oral cone diameter is about 5:1.

Remarks. The following discussion considers phylogenetic evidence for the generic assignment of Anomalocaris daleyae sp. nov., followed by a specieslevel comparison with A. canadensis from the Burgess Shale, with which it has regularly been compared.

Parsimony analysis of our modified version of the Zeng et al. (2023) matrix under equal weights ( Fig. 1A View Figure 1 ) unites Anomalocaris daleyae in an unresolved trichotomy with the type species of Anomalocaris , A. canadensis , and the type species of Ramskoeldia, R. platyacantha . As the oral cone is undescribed for R. platyacantha and body flaps are not assigned to A. daleyae , this grouping is based on detailed similarities in the frontal appendages. Implied weighting finds the interrelationships of the three species in this clade to be sensitive to differing concavity constants: k = 3, 6 and 7 recover a clade of A. daleyae and R. platyacantha ( Fig. 1B View Figure 1 ), k = 4, 5, 9 and 10 group A. canadensis and R. platyacantha , and k = 8 unites A. daleyae and A. canadensis . These unstable alternatives receive almost no support under symmetrical resampling.

The characters allying Anomalocaris daleyae and R. platyacantha to the exclusion of A. canadensis under some concavity constants involve the greater number of auxiliary spines on claw endites in the former two species. The character matrix of Zeng et al. (2023) is quantitatively dominated by frontal appendage characters, which are coded independently for different podomeres or regions along the proximodistal axis of the appendage. This allows a large character sample to be amassed, but predicts the independence of codings for each podomere or region. However, the form of endites, plus numbers and morphologies of anterior and posterior auxiliary spines, exhibit a high degree of covariation along the frontal appendage.

Our classification of A. daleyae as Anomalocaris rather than Ramskoeldia draws on the near identical tripartite, tuberculate, furrowed oral cones of A. daleyae and A. canadensis . Ramskoeldia platyacantha, Ramskoeldia consimilis and Amplectobelua symbrachiata differ from other radiodonts in possessing smooth plates, tuberculate plates and gnathobase-like structures – with shared features of the teeth and scales – on each of the segments with reduced flaps in an intermediate region between the head and trunk (new character 180 herein) ( Cong et al., 2017, 2018). These likely constitute the exclusive mouthparts for Amplectobelua symbrachiata , which is known from numerous assemblages of paired frontal appendages, head sclerites, associated smooth plates, tuberculate plates and gnathobase-like structures, and body flaps, none of which have an oral cone ( Cong et al., 2017). Based on the detailed similarities in the smooth plates, tuberculate plates and gnathobase-like structures in Ramskoeldia and Amplectobelua , it cannot presently be excluded that an absence of an oral cone in the latter may pertain to the former as well; the smaller number of body assemblages of the two Ramskoeldia species conform to those of A. symbrachiata in apparently lacking an oral cone.

The historical classification of Anomalocaris daleyae (see synonymy above) reflects consistent comparison and perceived affinities with A. canadensis . Nedin (1995) classified the EBS species under open nomenclature as Anomalocaris sp. but considered Chengjiang frontal appendages previously misassigned to A. canadensis by Hou and Bergstrom (1991) to be conspecific. The Chengjiang specimens were later identified by Hou et al. (1995) as A. saron (now Houcaris saron , following Wu, Fu et al., 2021) and Anomalocaris sp. Subsequent classification of the EBS Anomalocaris species as A. cf. canadensis and then A. aff. canadensis has reinforced the hypothesis that a distinct EBS species is closely comparable to A. canadensis . The presence of extra pairs of auxiliary spines on some claw endites was cited by Daley, Paterson et al. (2013) as the sole difference between the Australian and Canadian frontal appendages, but variability in auxiliary spine numbers in the EBS material led them to keep the species under open nomenclature. With the larger sample now available, we identify characters of the frontal appendages that permit the diagnosis of A. daleyae as distinct from A. canadensis , but despite the exceptional preservation in both biotas, we cannot identify consistent diagnostic differences in the oral cones. The most reliable characters for distinguishing A. daleyae from A. canadensis are the much longer base endite (80% the height of the associated podomere, vs 40% in A. canadensis ), the presence of auxiliary spines on the base endite (one pair vs none), the more robust basal portions of the claw endites on odd-numbered podomeres, three pairs of auxiliary spines on En1 (vs one pair or rarely two; see Zeng et al., 2023, supplementary fig. 1d, f), two pairs of auxiliary spines on En3 (vs one pair), two posterior auxiliary spines on En5 and En7 (vs one spine), and a terminal spine of roughly equal length to the dorsal spine on Cp13 (vs a terminal spine less than half the length of the dorsal spine).