Kylinxia zhangi ZENG, ZHAO AND HUANG, GEN.ETSP.NOV.
Creators: name: Zeng, Han
name: Zhao, Fangchen
name: Niu, Kecheng
name: Zhu, Maoyan
name: Huang, Diying
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Kylinxia
Kylinxia zhangi

description: <b> <i>Kylinxia zhangi</i> ZENG,ZHAO AND HUANG, GEN.ETSP.NOV.</b> <b>Etymology. <i>Kylin</i>:CHIMERICCREATUREINCHINESEMYTHOLOGY; <i>xia</i>:CHINESE WORDFORSHRIMP-LIKEARTHROPOD; AND <i>zhang</i>: AFTERYEHUIZHANG, WHO CONTRIBUTED THE PARATYPE. Holotype. NANJINGINSTITUTEOFGEOLOGYANDPALAEONTOLOGY (NIGP) 171304, PARTANDCOUNTERPART (FIGS. 1A, C, D, G, 2C, IANDEXTENDEDDATA FIGS.1A, B, D, 3N, O, 4G, 5, 6B, G, I). Referredmaterial. PARATYPE:YINGLIANGSTONENATURALHISTORYMUSEUM (YLSNHM) 01124 (FIGS. 1B, E, F, H, 2G, HANDEXTENDEDDATAFIGS. 1C, E, 4A, F, 6A, H). OTHERSPECIMENS:NIGP 171305 (EXTENDEDDATAFIGS.2A, B, 4D, 6C), NIGP 171306 (EXTENDEDDATAFIGS.2C, D, 4B, 6D), NIGP 171307 (EXTENDEDDATAFIGS. 2E–G, 4C, 6E) ANDNIGP 171308 (EXTENDEDDATA FIGS.2H, I, 4E, 6F). Localityandhorizon. JIANSHAN,HAIKOU,KUNMING,YUNNAN,CHINA;MAO- TIANSHANSHALEMEMBER,YU’ANSHANFORMATION, <i>WutingaSpiS – EoredliChia</i> BIOZONE (CAMBRIANSTAGE 3). Diagnosis. AN EUARTHROPOD POSSESSINGA PAIR OF UPWARD-ORIENTATED FRONTALMOST APPENDAGES,EACHCONSISTING OF A STOUTSHAFT AND A DISTAL ARTICULATED REGION COMPOSED OF 15 PODOMERES BEARING ELONGATE TRI- ANGULARENDITESWITHTWOROWSOFUPTOSEVENSHARPAUXILIARYSPINES.</b> FIVESTALKEDCOMPOUNDEYES. HEADSHIELDWITHROUNDEDGENALANGLES. <b>ANTERIORMOSTFOURPOST-ORALAPPENDAGESDIFFERENTIATEDFROMPOSTERIOR</b> ONES.TRUNKCONSISTINGOFUPTO 25 TERGITES.PYGIDIUMMERGEDFROMAT LEASTFIVESOMITES.TAILFANCOMPRISINGTHREELOBES. <b>Descriptionandcomparisons</b> <i>Kylinxia</i> ISKNOWNFROMSIXSPECIMENSWITHWELL-PRESERVEDSOFTPARTS (ADETAILEDDESCRIPTIONISPROVIDEDINTHESUPPLEMENTARYDISCUSSION). ITHASFIVESTALKEDCOMPOUNDEYESONTHEHEAD, OFWHICHTHEANTERIOR <b>TWO ARE AT LEAST TWICE AS LARGE AS THE POSTERIOR THREE (‘AE’ AND ‘PE’ IN</b> FIGS.1C, 2C, GANDEXTENDEDDATAFIGS. 1D, E, 2B, D, F, I, 3N, O, 4A–G, 5B). THISCONFIGURATIONOFEYESISREMINISCENTOFTHEPECULIARFIVEEYESIN <i>OpabiniaregaliS</i> <b>10</b>. THEEYEARRANGEMENTBETWEENTHETWOTAXAIS <b>COMPARABLE,WITH THE ANTERIORAND POSTERIOR EYES IN <i>Kylinxia</i> CORRE- SPONDINGTOTHEOUTERANDINNEREYESIN <i>Opabinia</i>, RESPECTIVELY 10 (‘AE’, ‘PE’, ‘OE’ AND ‘IE’, IN FIG. 2A–C, EXTENDEDDATA FIG. 3G, H, N, O). IN BOTH <i>Kylinxia</i> AND <i>Opabinia</i>, THEEYES AREBORDEREDWITHMARGINALRIMS (‘RM’ IN FIGS. 1C, 2B, C).THETWOORTHREEMEDIANEYESINEUARTHROPODSINCLUDING CAMBRIANHELMETIIDS ANDHYMENOCARINES 11 (‘LE’ AND ‘ME’ INEXTENDED DATAFIG.3J–M) MAYTHUSBEHOMOLOGOUSTOTHEPOSTERIORORINNERCOM- POUNDEYES IN <i>Kylinxia</i> OR <i>Opabinia</i>, RESPECTIVELY,BYREFERRING TOTHEIR COMPARABLEANATOMICAL POSITIONS AND SMALLERSIZES.</b> 1State Key Laboratory of Palaeobiology and Stratigraphy,Nanjing Institute of Geology and Palaeontology,Chinese Academy of Sciences,Nanjing,China.2Center for Excellence in Life and Palaeoenvironment,Chinese Academy of Sciences,Nanjing,China.3Department of Paleobiology,National Museum of Natural History, Smithsonian Institution,Washington,DC,USA.4College of Earth and Planetary Sciences, Universityof Chinese Academyof Sciences,Beijing, China.5 Yingliang Stone Natural History Museum,Nan’an,China. ✉e-mail: fczhao@nigpas.ac.cn; dyhuang@nigpas.ac.cn <b>THE FRONTALMOST APPENDAGESOF <i>Kylinxia</i> ARERADIODONT-LIKE (‘FA’ IN FIGS.1C, 2GANDEXTENDEDDATAFIGS.2B, D, F,I, 4A–G).THESEAPPENDAGES SHARE KEY MORPHOLOGICALFEATURESOF THE RADIODONTFAMILIES ANOMALO- CARIDIDAEAND AMPLECTOBELUIDAEREPRESENTEDBY <i>AnomaloCariS</i> 12 AND <i>RamSkoeldia</i> 13, RESPECTIVELY(‘FA’ INFIG.2D, GANDEXTENDEDDATAFIG.4F–I; DETAILEDCOMPARISONS ARE PROVIDEDIN THESUPPLEMENTARYDISCUSSION). THEIRSHAREDSIMILARITIESINCLUDE12–15DISTALARTICULATEDPODOMERES(‘P1’– ‘P15’ INFIGS.1C, 2GANDEXTENDEDDATAFIGS.2D,F, 4A–C,F–I),ASHAFTREGION WITHAN OBLIQUEARTHRODIAL MEMBRANEAND A SINGLEPAIROF ENDITES (‘SH’, ‘SA’ AND ‘SE’ INFIGS.1C, 2 GANDEXTENDEDDATAFIGS.1D, E, 2B,F,I, 4A–K, 5B), ENDITESOFALTERNATINGLENGTHS (‘SE’AND‘ED’INFIGS.1C,2D–HANDEXTENDED DATAFIGS.1D, E, 2B, I, 4A, D–I) ANDROUGHLY SYMMETRICALLY ARRANGED AUX- ILIARYSPINESONEACHENDITE (ARROWHEADSINFIG.2E,F,H,I);WEALSOINFERA</b> <b>SIMILARFUNCTIONALMORPHOLOGY 12, 13 (FIG.2D,GANDEXTENDEDDATAFIG.4F–I). HOWEVER,IN CONTRAST TO RADIODONTS,THE UPWARD ORIENTATION ANDTHE ABSENCEOF OUTERSPINESIN THEFRONTALMOST APPENDAGES OF <i>Kylinxia</i> (‘FA’ INFIGS.1C, 2 GANDEXTENDEDDATAFIGS.1D, E, 2B,D,F,I, 4A–G)AREFEATURESOF MEGACHEIRANS 14 (FIG.2 JANDEXTENDEDDATAFIG.7A–F,H),GREAT-APPENDAGE BIVALVEDEUARTHROPODS 15 ANDISOXYIDS 16, 17 (EXTENDEDDATAFIG.7J–O).THE PRESENCE OF AUXILIARY ENDITIC SPINESONTHE FRONTALMOST APPENDAGES OF RADIODONTS (ARROWHEADSINFIG.2E,F), <i>Kylinxia</i> (ARROWHEADSINFIG.2H,I) ANDMEGACHEIRANS(FIG.2K– MANDEXTENDEDDATAFIG.7D–I)STRENGTHENS THE MORPHOLOGICAL SIMILARITIESOF THEFRONTALMOST APPENDAGES AMONG THESETAXA,BECAUSESUCHAUXILIARYENDITICSPINESAREABSENTINISOXYIDS 16, 17 ANDOTHERCAMBRIANEUARTHROPODS 18 (EXTENDEDDATAFIG.7J–O).</b> <b>THE BODY PLANOF <i>Kylinxia</i> —WHICH CONSISTS OF A FUSED HEAD SHIELD, A MULTI-SEGMENTED TRUNK, A PYGIDIUM AND ARTHRODIZED POST-ORAL BIRAMOUS APPENDAGES—IS TYPICAL OF DEUTEROPODS ANDIS PARTICULARLY MEGACHEIRAN-LIKE (FIG. 1A, B AND EXTENDED DATAFIGS. 1, 2A, C, E, H). THE SEMI-CIRCULARHEADSHIELDOF <i>Kylinxia</i> WITHROUNDEDGENALANGLESISVERY SIMILARTOTHEHEADOFTHEMEGACHEIRAN <i>HaikouCariS</i> 14 (‘HS’ INFIG.1C, 2G, J AND EXTENDEDDATA FIGS. 1D, E, 2D, F, I, 4A–E, 7A). <i>Kylinxia</i> HASUP TO 25 TRUNK TERGITES (‘T1’–‘T25’IN FIG. 1A, B AND EXTENDEDDATA FIGS. 1, 2A, C, E, H), WHICHFALLSWITHINTHE RANGEOF 20–33 TERGITESIN ‘MULTI-SEGMENTED’ MEGACHEIRANSINCLUDING <i>Sklerolibyon</i>, <i>Jianfengia</i> AND <i>FortiforCepS</i> 19</b> <b>(EXTENDEDDATAFIG. 7B). ALTHOUGHAPYGIDIUMTHATCOVERSMULTIPLE APPENDAGES IN <i>Kylinxia</i> IS CHARACTERISTIC OF ARTIOPODANS 18 AND THE THREE-LOBED TAIL FANCOMPRISING A MIDDLE AND A PAIR OF LATERAL FLAPS OF <i>Kylinxia</i> HASFOUND COUNTERPARTSIN MEGACHEIRANS 19, FUXIANHUIIDS 18 ANDHYMENOCARINES 17, THEFUSEDPYGIDIUMARTICULATEDWITHATAILFANOF <i>Kylinxia</i> ISUNIQUEAMONGCAMBRIAN EUARTHROPODS (‘PY’ AND ‘TF’ INFIG.1G, HANDEXTENDEDDATAFIGS.1D,E, 6E–H).THETRUNKAPPENDAGESOF <i>Kylinxia</i> AREBIRAMOUS,COMPRISINGANENDOPODITEOF ATLEASTSEVENPODOMERES (‘EN’ AND ARROWHEADSIN FIG. 1D, EANDEXTENDEDDATA FIGS.1D, 2C, D, 4A) AND ANOVALEXOPODITEFLAPFRINGEDWITHLONGLAMELLAE (‘EX’ INFIG.1D, G, H AND EXTENDED DATA FIGS. 1D, E, 2F, 4C). THE POST-ORAL APPENDAGES IN</b> <b> <i>Kylinxia</i> AREHOMONOMOUS,EXCEPTTHATTHEANTERIORMOSTFOURAPPEND- AGE PAIRS (TWO IN THEHEAD ANDTWOIN THE TRUNK) AREDIFFERENTIATED AND SMALLER (‘DA’ INFIGS.1C,F, 2GANDEXTENDEDDATAFIGS.2B,D, F,I, 3N, 4A–E, 5B). THEARRANGEMENT ANDMORPHOLOGYOFTHE APPENDAGESOF <i>Kylinxia</i> AREMOSTSIMILARTO THOSEOFMEGACHEIRANS AMONGCAMBRIANEUARTHRO- PODS 19 (‘DA’, ‘EN’ AND ‘EX’ INEXTENDEDDATA FIG. 7B).</b> <b>THE SPECIMENS OF <i>Kylinxia</i> EXHIBIT TWO TOPOLOGICALLY CONSISTENT STRANDS OF DARK MATTERTHROUGH THE BODY, ONE CENTRAL (‘AC’ IN FIG.1A–C AND EXTENDEDDATA FIGS. 1, 2A, C, 6A–D) AND THE OTHER VENTRAL (‘VN’ IN FIG. 1A ANDEXTENDEDDATAFIGS. 1A, B, D, 2A, C, 6B–D). THE TWOSTRANDS CORRESPOND WELL IN POSITION AND MORPHOLOGY TO THE EUARTHROPOD</b> <b>ALIMENTARYCANALANDVENTRALNERVECORD,RESPECTIVELY 20, 21. THEALIMEN- TARYCANALISASSOCIATEDWITHPAIREDDIGESTIVEGLANDS (‘DG’ INFIG.1D AND EXTENDEDDATAFIGS.1D, E, 2D, G, 4C).INEACHTRUNKSEGMENTOF <i>Kylinxia</i>, BIFURCATING STRUCTURESINNERVATE APPENDAGES FROM THE VENTRAL NERVE CORD (‘NT’ INFIG. 1D ANDEXTENDEDDATAFIG. 6B–D) AND ARECOMPARABLE TOTHEPAIREDLEGNERVESINOTHERCAMBRIAN EUARTHROPODS 20, 22.</b> <b>INALATERAL VIEW,THEALIMENTARYCANALANDTHE VENTRALNERVECORDMEET ATTHE HEAD REGION (‘AC’,‘FG’,‘ND’ AND ‘NT’ IN FIGS. 1A–C, 2CAND EXTENDED DATAFIGS.1A,B,D, 2B, D, 3N, O, 4A,B,D, 5B).MORPHOLOGICALINTERPRETATION AIDEDBYELEMENTALANALYSIS (EXTENDEDDATAFIG.5 ANDSUPPLEMENTARY DISCUSSION) OF THIS REGION SHOWSOESOPHAGUS,FOREGUT (‘OS’ AND ‘FG’, RESPECTIVELY, INFIGS.1C, 2 CANDEXTENDEDDATAFIGS.1D, 2B, 3N, O, 4D, 5B, D)ANDPOSSIBLEASSOCIATEDNERVOUSTISSUES (‘NB’,‘ND’ AND ‘NF’ INFIGS. 1C, 2C, GANDEXTENDEDDATAFIGS.1A, 2B, 3N,O, 4A,D, 5B,D). THEANTERIORMOST OFTHESEISPUTATIVENERVOUSTISSUEBETWEENTHEOESOPHAGEALANDOCULAR REGIONS (‘NB’ INFIGS. 1C, 2 CANDEXTENDEDDATAFIGS.1D, 2B, 3N, O, 4D, 5B, D),ANDSITUATEDPOSTERIORLY ARENERVESINTOTHEFRONTALMOST APPENDAGES ANDDIFFERENTIATED POST-ORALAPPENDAGES (‘NF’ AND ‘ND’ INFIGS. 1C, 2C,G ANDEXTENDEDDATAFIGS. 1D, 2B, 3N, O, 4D, 5B, D). TAKEN TOGETHER,THE POST-OCULARFRONTALMOST APPENDAGESOF <i>Kylinxia</i> ANDTHE OESOPHAGEAL POSITION OF THEIR NERVES ARE MOST CONSISTENTWITH ADEUTEROCEREBRAL IDENTITY,THEDEFININGFEATUREOF DEUTEROPODA 7, 22.</b> Phylogeneticimplicationsof <i>Kylinxia</i> <b>IN SUMMARY, <i>Kylinxia</i> HAS A CHIMERIC BODY PLAN THAT COMBINES KEY MORPHOLOGICALFEATURES OF <i>Opabinia</i>, RADIODONTA ANDDEUTEROPODA (ESPECIALLYMEGACHEIRA) (FIG. 3B ANDEXTENDEDDATAFIG. 8). TORESOLVE ITS PHYLOGENETIC POSITION AMONG EUARTHROPODS, WEBUILT A MORPHO- LOGICAL MATRIXBY ASSEMBLING CHARACTERSFROM PUBLISHED DATASETS OF PANARTHROPODPHYLOGENY 6, 8 (THECHARACTERLISTANDCOMPLETEREFERENCE LIST AREPROVIDEDINTHESUPPLEMENTARYDISCUSSION).OURPHYLOGENETIC RECONSTRUCTIONRESOLVES <i>Kylinxia</i> ASTHEMOSTBASALDEUTEROPOD AND AS A TRANSITIONALTAXONTHATBRIDGESBETWEENRADIODONTAANDDEUTEROPODA (FIG.3A, EXTENDEDDATAFIG.9).THISPHYLOGENETICPLACEMENTOF <i>Kylinxia</i> IS STRONGLYSUPPORTEDBY ACONFIGURATIONOFEYESSIMILARTOTHATOF <i>Opabinia</i>, RADIODONT-LIKEFRONTALMOST APPENDAGES AND ADEUTEROPOD BODY THAT FEATURES AFUSEDHEAD SHIELD,AN ARTHRODIZED TRUNK,AFUSED PYGIDIUM ANDJOINTEDENDOPODITES.PLACEDNEARTHEROOTOFDEUTEROPODA, <i>Kylinxia</i> OFFERS A KEY REFERENCENODE FOR EXPLORINGTHE ORIGINS OFSEVERAL CRITICAL EVOLUTIONARYNOVELTIES DURING THE EARLY EVOLUTION OF EUARTHROPODS, INCLUDING THECOMPLETE ARTHRODIZATION OFTHE BODY,ARTHROPODIZATION OFTHETRUNKAPPENDAGES ANDCEPHALIZATIONOF AMULTI-SEGMENTEDHEAD, WHICHAREABSENTIN RADIODONTA 7 BUTPRESENTIN <i>Kylinxia</i>.</b> <b> <i>Kylinxia</i> ISHELPFULINRESOLVINGTHE INTERRELATIONSHIPS AMONGMAJOR DEUTEROPODASTEM GROUPS.OUR PHYLOGENY RECOVERS A VERY BASALPAR- APHYLETIC LINEAGE OF DEUTEROPODA FEATURING TYPICAL RAPTORIAL FRON- TALMOST APPENDAGES AND CONSISTINGOF MEGACHEIRA, PANCHELICERATA, GREAT-APPENDAGEBIVALVEDFORMS ANDISOXYIDA (FIG. 3AANDEXTENDED DATA FIG. 9). SUCH ABASAL POSITION OF MEGACHEIRA IS LARGELY A CONSE- QUENCE OF INCLUDING <i>Kylinxia</i>, WHICH COMBINES <i>Opabinia</i>, RADIODONT ANDMEGACHEIRANCHARACTERISTICS,INOUR ANALYSIS.A CLOSEPHYLOGENETIC LINKBETWEEN RADIODONTAAND MEGACHEIRAHASBEEN SUGGESTEDONTHE BASISOFTHEIRMORPHOLOGICALSIMILARITIESINFRONTALMOST APPENDAGES 14, 23, BUT IN THAT CONTEXT, RADIODONTA ISCONSIDERED A GROUP THATLEADS TO THE ORIGINOFONLYTHE CHELICERATA 14, 23 RATHERTHANTOTHE ORIGINOF ALL DEUTEROPODS 6, 8, 9. ACOMPARABLEBASALPLACEMENTOFPARAPHYLETICMEG- ACHEIRANS AND A TIGHT PARAPHYLETIC LINK BETWEEN MEGACHEIRANS AND PANCHELICERATESHAVEALSOBEENREPORTEDINARECENT STUDY 9. HOWEVER,IN THAT ANDOTHERCONTRIBUTIONS,ISOXYIDS 8, 9 ANDEVEN HYMENOCARINES 6 ARE RECONSTRUCTED ASMOREBASALTHANMEGACHEIRANS,ALTHOUGHTHISPLACE- MENTREMAINSUNDER DEBATE 4, 24. OURPHYLOGENETICINFERENCEINSTEAD FAVOURS A POSITIONOFISOXYIDA ABOVEMEGACHEIRA ANDPANCHELICERATA, WITHISOXYIDAANDGREAT-APPENDAGE BIVALVEDFORMSEITHERPARAPHYLETIC OR MONOPHYLETIC (FIG. 3A, EXTENDED DATA FIG. 9 AND SUPPLEMENTARY</b> <b>DISCUSSION).OUR EXPERIMENTALANALYSISWITH <i>Kylinxia</i> OMITTEDRECOVERS THEBASALPLACEMENTOFISOXYIDSFOUNDINPREVIOUSSTUDIES 8, 9 (EXTENDED DATA FIG. 10, SUPPLEMENTARYDISCUSSIONAND SUPPLEMENTARY DATA 2), EMPHASIZINGTHEINFLUENCEOF <i>Kylinxia</i> ONTHEEUARTHROPODPHYLOGENY.</b> Evolutionof arthropodfirstappendages <b>THE EVOLUTION OF THE FRONTALMOST APPENDAGES HAS BEEN A KEY ISSUE IN RESOLVING THE ORIGIN AND EARLY EVOLUTION OF EUARTHROPODS 3, 24, 25</b> . <b>THE RADIODONT-LIKEFRONTALMOST APPENDAGES ON AMEGACHEIRAN-LIKE BODYIN <i>Kylinxia</i> PROVIDES STRONGEVIDENCEFORTHE HOMOLOGYBETWEEN RADIODONT ANDMEGACHEIRAN FRONTALMOST APPENDAGES.UNDER THEPAR- SIMONYCRITERION,THESHAREDCHARACTERSINFRONTALMOST APPENDAGESOF RADIODONTAAND <i>Kylinxia</i> ARE VERY UNLIKELYTO BE CONVERGENT.DESPITE THEMISMATCHEDSEGMENTALAFFINITIESOFTHEFRONTALMOST APPENDAGESIN RADIODONTA 26, AND <i>Kylinxia</i> ANDTHEMEGACHEIRANS 22,THEIRHOMOLOGYIS HERECONSIDEREDMOSTLIKELY(SEECONTROVERSIES AND ALTERNATIVEHYPOTH- ESES 14, 19, 23 INTHESUPPLEMENTARYDISCUSSION).NOTABLY,OURPHYLOGENETIC TESTS SHOW THAT THEUNCERTAINTIES IN CODING THE SEGMENTAL AFFINITY OF RADIODONTFRONTALMOST APPENDAGESDONOTINFLUENCETHEPHYLOGENETIC POSITION OF <i>Kylinxia</i> NORTHE OVERALLTREETOPOLOGY.</b> <b>THEVERY BASALPHYLOGENETIC PLACEMENT OF <i>Kylinxia</i> AND OTHER DEU- TEROPODS THATHAVE TYPICALRAPTORIALFRONTALMOST APPENDAGESFAVOURS THEIDEATHATRAPTORIALFRONTALMOST APPENDAGES WEREAPLESIOMORPHIC FEATUREOF ANCESTRALDEUTEROPODS 8, 9, 14, 23 (‘A’–‘D’ INFIG. 3A), INCONTRAST TO THE ALTERNATIVE ANTENNIFORM HYPOTHESIS 6, 21. SUCH ABASAL GROUP- ING ALSOCASTS NEW LIGHTON THE ORIGINS OF FRONTALMOST APPENDAGES IN MAJOR EUARTHROPOD CROWN GROUPS:THE CHELICERAE INCHELICERATA AND THE(FIRST) ANTENNAEINMANDIBULATA.THESISTERGROUPINGOFMEGACHEIRA AND PANCHELICERATA IN OUR PHYLOGENY HAS GAINED PALAEONEUROLOGICAL EVIDENCEFROMACHELICERATEGROUNDPATTERNINTHEMEGACHEIRANBRAIN 22, ALTHOUGHALTERNATIVE SCENARIOS SUCH AS A CLOSE PARAPHYLETIC GROUPING OFMEGACHEIRANS ANDPANCHELICERATES 9 AND ATRADITIONALARTIOPODAN AFFINITYOFCHELICERATA EXIST 6. THUS, OURPHYLOGENETICTOPOLOGYSUP- PORTSTHEORIGINOF CHELICERATAFROM BASALDEUTEROPODSWITH RAPTORIAL FRONTALMOST APPENDAGES AND, IN THISSENSE,CHELICERAEWEREMODIFIED FROMMEGACHEIRANGREAT APPENDAGES 14, 22, 23 (‘C1’ AND ‘C2’ INFIG. 3A), IN CONTRAST TO THE MODEL INWHICH CHELICERAE EVOLVED FROM SMALL SENSO- RIALANTENNAE 9.</b> <b>OURPHYLOGENETICRECONSTRUCTIONRETRIEVES ANUPTREECLADEOFDEUTER- OPODSWITHTYPICALANTENNAEASTHEIRFIRST APPENDAGES,WHICHCOMPRISES ARTIOPODA,FUXIANHUIIDA ANDMOREMANDIBULATE-RELATEDGROUPS(‘E1’– ‘E3’ IN FIG. 3AANDEXTENDEDDATAFIG.9; SUPPLEMENTARY DISCUSSION).A SIMILARMONOPHYLYOFTHESEGROUPSWASREVEALEDRECENTLY 9, DESPITETHE FACTTHATOTHERIDEASHAVEBEENPROPOSED 6.ITISNOTABLETHATTHEANTENNAE INSOMEARTIOPODANS 18, 27 (‘E1’ INFIG.3 AANDEXTENDEDDATAFIG.7P, Q) AND HYMENOCARINES 28 (‘E3’ INFIG.3A) POSSESSPAIREDNEEDLE-SHAPEDENDITIC SPINES AND THESEHAVE BEENINTERPRETEDTOHAVE A PREDATORYFUNCTION. HOWEVER,ALMOSTIDENTICALANTENNALFORMS AREPRESENTIN ISOXYIDSSUCH AS <i>ISoxySVoluCriS</i> AND <i>ISoxySaurituS</i> 17, 29 (‘D3’ INFIG. 3AANDEXTENDED DATA FIG. 7L–O), WHEREAS THE FRONTALMOST APPENDAGES OF OTHER ISOXY- IDSEXHIBITLESS ANTENNIFORM FEATURES 16, 17, 30 (‘D1’ AND ‘D2’ INFIG. 3A AND EXTENDED DATAFIG. 7J, K). GIVEN THE INTERMEDIATE POSITION OF ISOXYIDA BETWEENTHEDEUTEROPODSWITHRAPTORIALFRONTALMOST APPENDAGES AND THOSE WITH TYPICAL ANTENNAE ON OUR TREES (FIG. 3A AND EXTENDEDDATA FIG. 9), THE REMARKABLE MORPHOLOGICAL VARIATIONS SHOWN BY ISOXYID FRONTALMOST APPENDAGESINDICATETHATTHEFIRST ANTENNAEOFMANDIBULATA MIGHTHAVE BEENDERIVEDFROMRAPTORIALPROTOTYPESRESEMBLINGTHOSE IN ISOXYIDA (‘D1’–‘D3’ IN FIG. 3A).</b> <b>THE <i>Kylinxia</i> DEMONSTRATES THE IMPORTANT ROLE OFTRANSITIONAL FOS- SILS IN RESOLVING THE EARLY HISTORY OF EUARTHROPODS. THE EMERGENCE OF STEM-GROUP EUARTHROPODS WITH MORPHOLOGICALLY AND FUNCTIONALLY DIVERSEFRONTALMOST APPENDAGES ILLUSTRATESTHE BROADEXPLORATION OF MORPHOSPACEAND ECOSPACE BY EARLYEUARTHROPODS DURING THECAM- BRIAN EXPLOSION 30, WHICHPROBABLYLAIDTHEFOUNDATIONFORTHEIR LATER EVOLUTIONARY SUCCESSES.</b>
description: Published as part of <i>Zeng, Han, Zhao, Fangchen, Niu, Kecheng, Zhu, Maoyan &amp; Huang, Diying, 2020, An early Cambrian euarthropod with radiodont-like raptorial appendages, pp. 101-105 in Nature 588</i> on pages 101-105, DOI: https://DOi.ORg/10.1038/s41586-020-2883-7, http://zenodo.org/record/4717877
description: {"references": ["10. Whittington, H. B. The enigmatic animal Opabinia regalis, Middle Cambrian, Burgess Shale, British Columbia. Phil. Trans. R. Soc. Lond. B 271, 1 - 43 (1975).", "11. Ortega-Hernandez, J. Homology of head sclerites in Burgess Shale euarthropods. Curr. Biol. 25, 1625 - 1631 (2015).", "12. Daley, A. C. &amp; Edgecombe, G. D. Morphology of Anomalocaris canadensis from the Burgess Shale. J. Paleontol. 88, 68 - 91 (2014).", "13. Cong, P. et al. New radiodonts with gnathobase-like structures from the Cambrian Chengjiang biota and implications for the systematics of Radiodonta. Pap. Palaeontol. 4, 605 - 621 (2018).", "14. Chen, J., Waloszek, D. &amp; Maas, A. A new ' great-appendage' arthropod from the Lower Cambrian of China and homology of chelicerate chelicerae and raptorial antero-ventral appendages. Lethaia 37, 3 - 20 (2004).", "15. Hou, X. New rare bivalved arthropods from the Lower Cambrian Chengjiang Fauna, Yunnan, China. J. Paleontol. 73, 102 - 116 (1999).", "16. Fu, D., Zhang, X. &amp; Shu, D. Soft anatomy of the early Cambrian arthropod Isoxys curvirostratus from the Chengjiang biota of south China with a discussion on the origination of great appendages. Acta Palaeontol. Pol. 56, 843 - 852 (2011).", "17. Legg, D. A. &amp; Vannier, J. The affinities of the cosmopolitan arthropod Isoxys and its implications for the origin of arthropods. Lethaia 46, 540 - 550 (2013).", "18. Hou, X. et al. The Cambrian Fossils of Chengjiang, China: The Flowering of Early Animal Life 2 nd edn (John Wiley &amp; Sons, 2017).", "19. Aria, C., Zhao, F., Zeng, H., Guo, J. &amp; Zhu, M. Fossils from South China redefine the ancestral euarthropod body plan. BMC Evol. Biol. 20, 4 (2020).", "20. Ortega-Hernandez, J., Lerosey-Aubril, R. &amp; Pates, S. Proclivity of nervous system preservation in Cambrian Burgess Shale-type deposits. Proc. R. Soc. Lond. B 286, 20192370 (2019).", "21. Yang, J., Ortega-Hernandez, J., Butterfield, N. J. &amp; Zhang, X. Specialized appendages in fuxianhuiids and the head organization of early euarthropods. Nature 494, 468 - 471 (2013).", "22. Tanaka, G., Hou, X., Ma, X., Edgecombe, G. D. &amp; Strausfeld, N. J. Chelicerate neural ground pattern in a Cambrian great appendage arthropod. Nature 502, 364 - 367 (2013).", "7. Ortega-Hernandez, J. Making sense of ' lower' and ' upper' stem-group Euarthropoda, with comments on the strict use of the name Arthropoda von Siebold, 1848. Biol. Rev. 91, 255 - 273 (2016).", "6. Legg, D. A., Sutton, M. D. &amp; Edgecombe, G. D. Arthropod fossil data increase congruence of morphological and molecular phylogenies. Nat. Commun. 4, 2485 (2013).", "8. Aria, C. &amp; Caron, J. - B. Burgess Shale fossils illustrate the origin of the mandibulate body plan. Nature 545, 89 - 92 (2017).", "23. Haug, J. T., Waloszek, D., Maas, A., Liu, Y. &amp; Haug, C. Functional morphology, ontogeny and evolution of mantis shrimp-like predators in the Cambrian. Palaeontology 55, 369 - 399 (2012).", "9. Aria, C. &amp; Caron, J. - B. A middle Cambrian arthropod with chelicerae and proto-book gills. Nature 573, 586 - 589 (2019).", "4. Daley, A. C., Antcliffe, J. B., Drage, H. B. &amp; Pates, S. Early fossil record of Euarthropoda and the Cambrian Explosion. Proc. Natl Acad. Sci. USA 115, 5323 - 5331 (2018).", "24. Ortega-Hernandez, J., Janssen, R. &amp; Budd, G. E. Origin and evolution of the panarthropod head - a palaeobiological and developmental perspective. Arthropod Struct. Dev. 46, 354 - 379 (2017).", "3. Edgecombe, G. D. &amp; Legg, D. A. Origins and early evolution of arthropods. Palaeontology 57, 457 - 468 (2014).", "25. Scholtz, G. &amp; Edgecombe, G. D. The evolution of arthropod heads: reconciling morphological, developmental and palaeontological evidence. Dev. Genes Evol. 216, 395 - 415 (2006).", "26. Cong, P., Ma, X., Hou, X., Edgecombe, G. D. &amp; Strausfeld, N. J. Brain structure resolves the segmental affinity of anomalocaridid appendages. Nature 513, 538 - 542 (2014).", "27. Stein, M. A new arthropod from the Early Cambrian of North Greenland, with a ' great appendage' - like antennula. Zool. J. Linn. Soc. 158, 477 - 500 (2010).", "28. Yang, J., Ortega-Hernandez, J., Lan, T., Hou, J. &amp; Zhang, X. A predatory bivalved euarthropod from the Cambrian (Stage 3) Xiaoshiba Lagerstatte, South China. Sci. Rep. 6, 27709 (2016).", "29. Fu, D., Zhang, X., Budd, G. E., Liu, W. &amp; Pan, X. Ontogeny and dimorphism of Isoxys auritus (Arthropoda) from the Early Cambrian Chengjiang biota, South China. Gondwana Res. 25, 975 - 982 (2014).", "30. Aria, C. &amp; Caron, J. - B. Cephalic and limb anatomy of a new isoxyid from the Burgess Shale and the role of \" stem bivalved arthropods \" in the disparity of the frontalmost appendage. PLoS ONE 10, e 0124979 (2015)."]}