Publications

2018
J. Ortega-Hernández, J. Yang, and X. G. Zhang. 2018. “Fuxianhuiids.” Current Biology, 28, 13, Pp. R724-R725. Publisher's VersionAbstract
The fuxianhuiids — of which there are eight species described so far —are a clade of extinct soft-bodied euarthropods (colloquially: arthropods) that are known
from early Cambrian marine deposits in South China (Figure 1). They are widely
regarded as distant relatives of extant euarthropod groups — namely arachnids,
myriapods, crustaceans and insects. The exceptional preservation of their fossils
has provided unique information on their morphology (Figure 2). Fuxianhuiids
have contributed towards a better understanding of the early evolutionary
radiation of euarthropods —the most successful animal phylum in the history
of life on Earth — and led to a detailed reconstruction of the origin of the
euarthropod body plan.
S. Pates, A.C. Daley, and J. Ortega-Hernández. 2018. “Reply to Comment on “Aysheaia prolata from the Utah Wheeler Formation (Drumian, Cambrian) is a frontal appendage of the radiodontan Stanleycaris” with the formal description of Stanleycaris.” Acta Palaeontologica Polonica, 63. Publisher's VersionAbstract
As part of a comprehensive examination of all radiodontans
from Cambrian localities in the USA, Pates et al. (2017a, b)
and Pates and Daley (2017) revised the taxonomic affinities
of several described specimens. This included the reinterpretation
of two putative lobopodians, one from the Wheeler
Formation (Utah, USA) and one from the Valdemiedes Formation
(Spain), as frontal appendages of the radiodontan
genera Stanleycaris and Caryosyntrips respectively. In their
comment, Gámez Vintaned and Zhuravlev (2018) disagree
with these conclusions and raise three topics for discussion:
(i) anatomical features they suggest support a lobopodian
affinity for “Mureropodia”; (ii) the identity of Caryosyntrips
as a radiodontan, and the assignment of certain specimens to
this genus; and (iii) the nomenclatural status of Stanleycaris
hirpex as an invalid taxon. For (i), we dispute that the anatomical
features put forward by Gámez Vintaned and Zhuravlev
(2018) are biological and conclude that a lobopodian
affinity for Mureropodia is untenable. In response to (ii), we
provide further evidence supporting a radiodontan affinity
for Caryosyntrips, and those specimens ascribed to this genus.
Finally, we concur with (iii) Stanleycaris as an invalid
taxon according to the International Code on Zoological
Nomenclature (ICZN), and have rectified the situation by
providing a valid systematic description.
R. Lerosey-Aubril, R. Gaines, T. A. Hegna, J. Ortega-Hernández, P. Van Roy, C. Kier, and E. Bonino. 2018. “The Weeks Formation Konservat-Lagerstätte and the evolutionary transition of Cambrian marine life.” Journal of the Geological Society , 175, Pp. 705-715. Publisher's VersionAbstract
The Weeks Formation in Utah is the youngest (c. 499 Ma) and least studied Cambrian Lagerstätte of the western United States. It preserves a diverse exceptionally-preserved fauna that inhabited a relatively deep-water environment at the offshore margin of a carbonate platform, resembling the setting of the underlying Wheeler and Marjum formations. Yet, the Weeks fauna differs significantly in composition from the other remarkable biotas of Cambrian Series 3 of Utah, suggesting a significant Guzhangian faunal restructuring. This bioevent is regarded as the onset of a transitional episode in the history of life, separating the two primary diversifications of the Early Palaeozoic. The Weeks fossils have been strongly affected by late diagenetic processes, but some specimens still preserve exquisite anatomical details.
2017
J. Ortega-Hernández, A. Azizi, T. W. Hearing, T. H. P. Harvey, G.D. Edgecombe, A. Hafid, and K. El Hariri. 2017. “Corrigendum: A xandarellid artiopodan from Morocco - a middle Cambrian link between soft-bodied euarthropod communities in North Africa and South China.” Scientific Reports, 7, Pp. 46797.
S. Pates, A.C. Daley, and J. Ortega-Hernández. 2017. “Aysheaia prolata from the Wheeler Formation (Cambrian, Drumian) is a frontal appendage of the radiodontan Stanleycaris.” Acta Palaeontologica Polonica, 62, 3, Pp. 619-625.Abstract
Aysheaia prolata, was described as the only lobopodian from the Drumian (Cambrian) Wheeler Formation in Utah, USA, and the sole representative of this genus besides the type species Aysheaia pedunculata, from the Cambrian (Stage 5) Stephen Formation, British Columbia. A redescription of Aysheaia prolata reveals previously overlooked morphological features, including segmental boundaries between putative lobopods, and curved terminal spines on the putative anterior end. These observations undermine lobopodian affinities of Aysheaia prolata, and instead we interpret this specimen as an isolated radiodontan frontal appendage. The presence of 11 podomeres, five of which possess elongate and anteriorly recurved ventral blades with auxiliary spines, together with shorter robust dorsal spines, identify the specimen as Stanleycaris. This represents the first report of Stanelycaris outside of the Cambrian Stage 5 thin Stephen Formation in British Columbia, expanding its palaeobiogeographic and stratigraphic range. Aysheaia is left as a monotypic genus endemic to the Burgess Shale. The Spence Shale luolishaniid Acinocrinus stichus is currently the only lobopodian known from the Cambrian of Utah.
J. Ortega-Hernández, R. Janssen, and G. E. Budd. 2017. “Origin and evolution of the panarthropod head - A palaeobiological and developmental perspective.” Arthropod Structure and Development, 46, Pp. 354-379.Abstract
The panarthropod head represents a complex body region that has evolved through the integration and functional specialization of the anterior appendage-bearing segments. Advances in the developmental biology of diverse extant organisms have led to a substantial clarity regarding the relationships of segmental homology between Onychophora (velvet worms), Tardigrada (water bears), and Euarthropoda (e.g. arachnids, myriapods, crustaceans, hexapods). The improved understanding of the segmental organization in panarthropods offers a novel perspective for interpreting the ubiquitous Cambrian fossil record of these successful animals. A combined palaeobiological and developmental approach to the study of the panarthropod head through deep time leads us to propose a consensus hypothesis for the intricate evolutionary history of this important tagma. The contribution of exceptionally preserved brains in Cambrian fossils - together with the recognition of segmentally informative morphological characters - illuminate the polarity for major anatomical features. The euarthropod stem-lineage provides a detailed view of the step-wise acquisition of critical characters, including the origin of a multiappendicular head formed by the fusion of several segments, and the transformation of the ancestral protocerebral limb pair into the labrum, following the postero-ventral migration of the mouth opening. Stem-group onychophorans demonstrate an independent ventral migration of the mouth and development of a multisegmented head, as well as the differentiation of the deutocerebral limbs as expressed in extant representatives. The anterior organization of crown-group Tardigrada retains several ancestral features, such as an anterior-facing mouth and one-segmented head. The proposed model aims to clarify contentious issues on the evolution of the panarthropod head, and lays the foundation from which to further address this complex subject in the future.
A.W. Hunter and J. Ortega-Hernández. 2017. “A primitive starfish ancestor from the Early Ordovician of Morocco reveals the origin of crown group Echinodermata.” bioRxiv. Publisher's VersionAbstract

The somasteroids are Ordovician star-shaped animals widely regarded as ancestors of Asterozoa, the group of extant echinoderms that includes brittle stars and starfish. The phylogenetic position of somasteroids makes them critical for understanding the origin and early evolution of crown group Echinodermata. However, the early evolution of asterozoans, the origin of their distinctive body organization and their relationships with other Cambrian and Ordovician echinoderms, such as edrioasteroids, blastozoans, crinoids, and other asterozoans, remain problematic due to the difficulties of comparing the calcitic endoskeleton of these disparate groups. Here we describe the new somasteroid Cantabrigiaster fezouataensis from the Early Ordovician (Tremadocian) Fezouata Lagerstatte in Morocco. Cantabrigiaster shares with other somasteroids the presence of rod-like virgal ossicles that articulate with the ambulacrals, but differs from all other known asterozoans in the absence of adambulacral ossicles defining the arm margins. The unique arm construction evokes parallels with non-asterozoan echinoderms. Developmentally informed Bayesian and parsimony based phylogenetic analyses, which reflect the homology of the biserial ambulacral ossicles in Paleozoic echinoderms according to the Extraxial-Axial Theory, recover Cantabrigiaster as basal within stem group Asterozoa. Our results indicate that Cantabrigiaster is the earliest diverging stem group asterozoan, revealing the ancestral morphology of this major clade and clarifying the affinities of problematic Ordovician taxa. Somasteroids are resolved as a paraphyletic grade within stem and crown group Asterozoa (starfishes), whereas stenuroids are paraphyletic within stem group Ophiuroidea (brittle stars). Cantabrigiaster also illuminates the relationship between Ordovician crown group Echinodermata and its Cambrian stem lineage, which includes sessile forms with incipient radial symmetry such as edrioasteroids and blastozoans. The contentious Pelmatozoa hypothesis (i.e. monophyly of blastozoans and crinoids) is not supported; instead, blastozoans represent the most likely sister-taxon of crown group Echinodermata.

R. Lerosey-Aubril, X. Zhu, and J. Ortega-Hernández. 2017. “The Vicissicaudata revisited - insights from a new aglaspidid arthropod with caudal appendages from the Furongian of China.” Scientific Reports, 7, Pp. 11117.Abstract
Cambrian marine ecosystems were dominated by arthropods, and more specifically artiopods. Aglaspidids represent an atypical group amongst them, not the least because they evolved and rapidly diversified during the late Cambrian, a time interval between the two diversification events of the Early Palaeozoic. Recent phylogenetic analyses have retrieved aglaspidids within the Vicissicaudata, a potentially important, but difficult to define clade of artiopods. Here we describe a new aglaspidid from the Furongian Guole Konservat-Lagerstatte of South China. This taxon displays a pretelsonic segment bearing non-walking appendages, features as-yet known in all vicissicaudatans, but aglaspidids. A new comprehensive phylogenetic analysis provides strong support for the legitimacy of a monophyletic clade Vicissicaudata, and demonstrates the pertinence of new characters to define Aglaspidida. It also motivates important changes to the systematics of the phylum, including the elevation of Artiopoda to the rank of subphylum, and the establishment of a new superclass Vicissicaudata and a new aglaspidid family Tremaglaspididae. Two diversification pulses can be recognized in the early history of artiopods - one in the early Cambrian (trilobitomorphs) and the other in the late Cambrian (vicissicaudatans). The discrepancy between this pattern and that traditionally depicted for marine invertebrates in the Early Palaeozoic is discussed.
J. Ortega-Hernández. 2017. “What is the point of phylogenies?” In 52 More Things You Should Know About Palaeontology, Pp. 110-111. Nova Scotia, Canada: Agile Libre.
J. Ortega-Hernández, A. Azizi, T. W. Hearing, T. H. Harvey, G.D. Edgecombe, A. Hafid, and K. El Hariri. 2017. “A xandarellid artiopodan from Morocco - a middle Cambrian link between soft-bodied euarthropod communities in North Africa and South China.” Scientific Reports, 7, Pp. 42616.Abstract
Xandarellida is a well-defined clade of Lower Palaeozoic non-biomineralized artiopodans that is exclusively known from the early Cambrian (Stage 3) Chengjiang biota of South China. Here we describe a new member of this group, Xandarella mauretanica sp. nov., from the middle Cambrian (Stage 5) Tatelt Formation of Morocco, making this the first non-trilobite Cambrian euarthropod known from North Africa. X. mauretanica sp. nov. represents the youngest occurrence of Xandarellida - extending its stratigraphic range by approximately 10 million years - and expands the palaeobiogeographic distribution of the group to the high southern palaeolatitudes of West Gondwana. The new species provides insights into the lightly sclerotized ventral anatomy of Xandarellida, and offers stratigraphically older evidence for a palaeobiogeographic connection between Burgess Shale-type euarthropod communities in North Africa and South China, relative to the (Tremadocian) Fezouata biota.
2016
J. Ortega-Hernández and M. R. Smith. 2016. “The enigmatic lobopodian Hallucigenia and the origin of velvet worms.” Fundamental, 29, Pp. 1-46.
J. Yang, J. Ortega-Hernández, N. J. Butterfield, Y. Liu, G. S. Boyan, J. B. Hou, T. Lan, and X. G. Zhang. 2016. “Fuxianhuiid ventral nerve cord and early nervous system evolution in Panarthropoda.” Proceedings of the National Academy of Sciences U S A, 113, Pp. 2988-93.Abstract
Panarthropods are typified by disparate grades of neurological organization reflecting a complex evolutionary history. The fossil record offers a unique opportunity to reconstruct early character evolution of the nervous system via exceptional preservation in extinct representatives. Here we describe the neurological architecture of the ventral nerve cord (VNC) in the upper-stem group euarthropod Chengjiangocaris kunmingensis from the early Cambrian Xiaoshiba Lagerstatte (South China). The VNC of C. kunmingensis comprises a homonymous series of condensed ganglia that extend throughout the body, each associated with a pair of biramous limbs. Submillimetric preservation reveals numerous segmental and intersegmental nerve roots emerging from both sides of the VNC, which correspond topologically to the peripheral nerves of extant Priapulida and Onychophora. The fuxianhuiid VNC indicates that ancestral neurological features of Ecdysozoa persisted into derived members of stem-group Euarthropoda but were later lost in crown-group representatives. These findings illuminate the VNC ground pattern in Panarthropoda and suggest the independent secondary loss of cycloneuralian-like neurological characters in Tardigrada and Euarthropoda.
J. Ortega-Hernández. 2016. “Making sense of 'lower' and 'upper' stem-group Euarthropoda, with comments on the strict use of the name Arthropoda von Siebold, 1848.” Biological Reviews, 91, Pp. 255-73.Abstract
The ever-increasing number of studies that address the origin and evolution of Euarthropoda - whose extant representatives include chelicerates, myriapods, crustaceans and hexapods - are gradually reaching a consensus with regard to the overall phylogenetic relationships of some of the earliest representatives of this phylum. The stem-lineage of Euarthropoda includes numerous forms that reflect the major morphological transition from a lobopodian-type to a completely arthrodized body organization. Several methods of classification that aim to reflect such a complex evolutionary history have been proposed as a consequence of this taxonomic diversity. Unfortunately, this has also led to a saturation of nomenclatural schemes, often in conflict with each other, some of which are incompatible with cladistic-based methodologies. Here, I review the convoluted terminology associated with the classification of stem-group Euarthropoda, and propose a synapomorphy-based distinction that allows 'lower stem-Euarthropoda' (e.g. lobopodians, radiodontans) to be separated from 'upper stem-Euarthropoda' (e.g. fuxianhuiids, Cambrian bivalved forms) in terms of the structural organization of the head region and other aspects of overall body architecture. The step-wise acquisition of morphological features associated with the origins of the crown-group indicate that the node defining upper stem-Euarthropoda is phylogenetically stable, and supported by numerous synapomorphic characters; these include the presence of a deutocerebral first appendage pair, multisegmented head region with one or more pairs of post-ocular differentiated limbs, complete body arthrodization, posterior-facing mouth associated with the hypostome/labrum complex, and post-oral biramous arthropodized appendages. The name 'Deuteropoda' nov. is proposed for the scion (monophyletic group including the crown-group and an extension of the stem-group) that comprises upper stem-Euarthropoda and Euarthropoda. A brief account of common terminological inaccuracies in recent palaeontological studies evinces the utility of Deuteropoda nov. as a reference point for discussing aspects of early euarthropod phylogeny.
J. Ortega-Hernandez and G. E. Budd. 2016. “The nature of non-appendicular anterior paired projections in Palaeozoic total-group Euarthropoda.” Arthropod Structure and Development, 45, Pp. 185-199.Abstract
Recent studies have clarified the segmental organization of appendicular and exoskeletal structures in the anterior region of Cambrian stem-group Euarthropoda, and thus led to better understanding of the deep evolutionary origins of the head region in this successful animal group. However, there are aspects of the anterior organization of Palaeozoic euarthropods that remain problematic, such as the morphological identity and significance of minute limb-like projections on the anterior region in stem and crown-group representatives. Here, we draw attention to topological and morphological similarities between the frontal filaments of extant Crustacea and the embryonic frontal processes of Onychophora, and distinctive anterior paired projections observed in several extinct total-group Euarthropoda. Anterior paired projections are redescribed in temporally and phylogenetically distant fossil taxa, including the gilled lobopodians Kerygmachela kierkegaardi and Pambdelurion whittingtoni, the bivalved stem-euarthropod Canadaspis perfecta, the larval pycnogonid Cambropycnogon klausmuelleri, and the mandibulate Tanazios dokeron. Developmental data supporting the homology of the 'primary antennae' of Onychophora, the 'frontal appendages' of lower-stem Euarthropoda, and the hypostome/labrum complex of Deuteropoda, argue against the morphological identity of the anterior paired projections of extant and extinct panarthropods as a pair of pre-ocular appendages. Instead, we regard the paired projections of fossil total-group euarthropods as non-appendicular evaginations with a likely protocerebral segmental association, and a possible sensorial function. The widespread occurrence of pre-ocular paired projections among extant and extinct taxa suggests their potential homology as fundamentally ancestral features of the anterior body organization in Panarthropoda. Non-appendicular paired projections with a sensorial function may reflect a critical--yet previously overlooked--component of the panarthropod ground pattern.
J. Ortega-Hernandez, P. Van Roy, and R. Lerosey-Aubril. 2016. “A new aglaspidid euarthropod with a six-segmented trunk from the Lower Ordovician Fezouata Konservat-Lagerstätte, Morocco.” Geological Magazine, 153, Pp. 524-536.Abstract
A new euarthropod with an uncommon morphology, Brachyaglaspis singularis gen. et sp. nov., is described from the Early Ordovician (middle Floian) Fezouata biota of Morocco. The presence of a pair of postventral plates, widely attached to each other and located under the posterior-most trunk tergite and the base of the tailspine, indicates a phylogenetic relationship with the enigmatic group Aglaspidida. The overall morphology of Brachyaglaspis most closely resembles that of the ‘Ordovician-type’ aglaspidids, more specifically the late Cambrian – Early Ordovician genus Tremaglaspis. However, the presence of a prominent cephalon and only six trunk tergites in the new genus deviates from the organization of all other known aglaspidid species, notably extending the known range of morphological disparity of the group. A taxonomic revision of this euarthropod group indicates that the most accurate name and authorship combination correspond to Aglaspidida Walcott, 1912.
J. Yang, J. Ortega-Hernandez, T. Lan, J. B. Hou, and X. G. Zhang. 2016. “A predatory bivalved euarthropod from the Cambrian (Stage 3) Xiaoshiba Lagerstatte, South China.” Scientific Reports, 6, Pp. 27709.Abstract
Bivalved euarthropods represent a conspicuous component of exceptionally-preserved fossil biotas throughout the Lower Palaeozoic. However, most of these taxa are known from isolated valves, and thus there is a limited understanding of their morphological organization and palaeoecology in the context of early animal-dominated communities. The bivalved euarthropod Clypecaris serrata sp. nov., recovered from the Cambrian (Stage 3) Hongjingshao Formation in Kunming, southern China, is characterized by having a robust first pair of raptorial appendages that bear well-developed ventral-facing spines, paired dorsal spines on the trunk, and posteriorly oriented serrations on the anteroventral margins of both valves. The raptorial limbs of C. serrata were adapted for grasping prey employing a descending stroke for transporting it close the mouth, whereas the backwards-facing marginal serrations of the bivalved carapace may have helped to secure the food items during feeding. The new taxon offers novel insights on the morphology of the enigmatic genus Clypecaris, and indicates that the possession of paired dorsal spines is a diagnostic trait of the Family Clypecarididae within upper stem-group Euarthropoda. C. serrata evinces functional adaptations for an active predatory lifestyle within the context of Cambrian bivalved euarthropods, and contributes towards the better understanding of feeding diversity in early ecosystems.
2015
J. Ortega-Hernandez. 2015. “Homology of head sclerites in Burgess Shale euarthropods.” Current Biology, 25, Pp. 1625-31.Abstract
The Cambrian fossil record of euarthropods (extant arachnids, myriapods, crustaceans, hexapods) has played a major role in understanding the origins of these successful animals and indicates that early ancestors underwent an evolutionary transition from soft-bodied taxa (lobopodians) to more familiar sclerotized forms with jointed appendages [1-3]. Recent advances in paleoneurology and developmental biology show that this major transformation is reflected by substantial changes in the head region of early euarthropods, as informed by the segmental affinity of the cephalic appendages [1, 4-6]. However, data on the implications of this reorganization for non-appendicular exoskeletal structures are lacking, given the difficulty of inferring the precise segmental affinities of these features. Here, I report neurological remains associated with the stalked eyes and "anterior sclerite" in the (middle Cambrian) Burgess Shale euarthropods Helmetia expansa and Odaraia alata and provide evidence that these features are associated with nerve traces originating from the anterior brain region, the protocerebrum. The position of the protocerebral ganglia in exceptionally preserved Cambrian euarthropods indicates the homology of the anterior sclerite in extinct groups (e.g., fuxianhuiids, bivalved forms, artiopodans [7, 8]) and allows new comparisons with the dorsal cephalic plate of radiodontans, large nektonic predators whose anterior segmental organization bears fundamental similarities to that of Paleozoic lobopodians [1, 6, 9, 10]. These observations allow reconstruction of the segmental architecture of the head region in the earliest sclerotized euarthropods and demonstrate the deep homology between exoskeletal features in an evolutionary continuum of taxa with distinct types of body organization.
J. Ortega-Hernandez. 2015. “Lobopodians.” Current Biology, 25, Pp. R873-5.
J. Ortega-Hernandez, R. Lerosey-Aubril, C. Kier, and E. Bonino. 2015. “A rare non-trilobite artiopodan from the Guzhangian (Cambrian Series 3) Weeks Formation Konservat-Lagerstätte in Utah, USA.” Palaeontology, 58, Pp. 265-276.Abstract
We describe a weakly biomineralized non-trilobite artiopodan arthropod from the Guzhangian Weeks Formation of Utah. Falcatamacaris bellua gen. et sp. nov. is typified by a thin calcitic cuticle, broad cephalon without eyes or dorsal ecdysial sutures, an elongate trunk with distinctively sickle-shaped pleural spines and a long tailspine with a bifurcate termination. The precise affinities of Falcatamacaris gen. nov. are problematic due to the presence of unique features within Artiopoda, such as the peculiar morphology of the pleural and posterior regions of the trunk. Possible affinities with aglaspidid-like arthropods and concilitergans are discussed based on the possession of 11 trunk tergites, edge-to-edge articulations and overall body spinosity. The new taxon highlights the importance of the Weeks Formation Konservat-Lagerstätte for further understanding the diversity of extinct arthropod groups in the upper Cambrian.
J. Yang, J. Ortega-Hernandez, S. Gerber, N. J. Butterfield, J. B. Hou, T. Lan, and X. G. Zhang. 2015. “A superarmored lobopodian from the Cambrian of China and early disparity in the evolution of Onychophora.” Proceedings of the National Academy of Sciences U S A, 112, Pp. 8678-83.Abstract
We describe Collinsium ciliosum from the early Cambrian Xiaoshiba Lagerstatte in South China, an armored lobopodian with a remarkable degree of limb differentiation including a pair of antenna-like appendages, six pairs of elongate setiferous limbs for suspension feeding, and nine pairs of clawed annulated legs with an anchoring function. Collinsium belongs to a highly derived clade of lobopodians within stem group Onychophora, distinguished by a substantial dorsal armature of supernumerary and biomineralized spines (Family Luolishaniidae). As demonstrated here, luolishaniids display the highest degree of limb specialization among Paleozoic lobopodians, constitute more than one-third of the overall morphological disparity of stem group Onychophora, and are substantially more disparate than crown group representatives. Despite having higher disparity and appendage complexity than other lobopodians and extant velvet worms, the specialized mode of life embodied by luolishaniids became extinct during the Early Paleozoic. Collinsium and other superarmored lobopodians exploited a unique paleoecological niche during the Cambrian explosion.

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