scholarly journals Cambrian stem-group annelids and a metameric origin of the annelid head

2015 ◽  
Vol 11 (10) ◽  
pp. 20150763 ◽  
Author(s):  
Luke Parry ◽  
Jakob Vinther ◽  
Gregory D. Edgecombe
Keyword(s):  
Anterior Segment ◽  
Character State ◽  
Early Cambrian ◽  
Primitive Character ◽  
Burgess Shale ◽  
Crown Group ◽  
Middle Cambrian ◽  
Stem Group

The oldest fossil annelids come from the Early Cambrian Sirius Passet and Guanshan biotas and Middle Cambrian Burgess Shale. While these are among the best preserved polychaete fossils, their relationship to living taxa is contentious, having been interpreted either as members of extant clades or as a grade outside the crown group. New morphological observations from five Cambrian species include the oldest polychaete with head appendages, a new specimen of Pygocirrus from Sirius Passet, and an undescribed form from the Burgess Shale. We propose that the palps of Canadia are on an anterior segment bearing neuropodia and that the head of Phragmochaeta is formed of a segment bearing biramous parapodia and chaetae. The unusual anatomy of these taxa suggests that the head is not differentiated into a prostomium and peristomium, that palps are derived from a modified parapodium and that the annelid head was originally a parapodium-bearing segment. Canadia , Phragmochaeta and the Marble Canyon annelid share the presence of protective notochaetae, interpreted as a primitive character state subsequently lost in Pygocirrus and Burgessochaeta , in which the head is clearly differentiated from the trunk.

scholarly journals Ancestral morphology of Ecdysozoa constrained by an early Cambrian stem group ecdysozoan

2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Richard J. Howard ◽  
Gregory D. Edgecombe ◽  
Xiaomei Shi ◽  
Xianguang Hou ◽  
Xiaoya Ma
Keyword(s):  
Feeding Strategy ◽  
Phylogenetic Analyses ◽  
Morphological Diversity ◽  
Early Cambrian ◽  
Ancestral State ◽  
Crown Group ◽  
Stem Group ◽  
Chengjiang Biota ◽  
Fossil Records ◽  
Experimental Decay

Abstract Background Ecdysozoa are the moulting protostomes, including arthropods, tardigrades, and nematodes. Both the molecular and fossil records indicate that Ecdysozoa is an ancient group originating in the terminal Proterozoic, and exceptional fossil biotas show their dominance and diversity at the beginning of the Phanerozoic. However, the nature of the ecdysozoan common ancestor has been difficult to ascertain due to the extreme morphological diversity of extant Ecdysozoa, and the lack of early diverging taxa in ancient fossil biotas. Results Here we re-describe Acosmia maotiania from the early Cambrian Chengjiang Biota of Yunnan Province, China and assign it to stem group Ecdysozoa. Acosmia features a two-part body, with an anterior proboscis bearing a terminal mouth and muscular pharynx, and a posterior annulated trunk with a through gut. Morphological phylogenetic analyses of the protostomes using parsimony, maximum likelihood and Bayesian inference, with coding informed by published experimental decay studies, each placed Acosmia as sister taxon to Cycloneuralia + Panarthropoda—i.e. stem group Ecdysozoa. Ancestral state probabilities were calculated for key ecdysozoan nodes, in order to test characters inferred from fossils to be ancestral for Ecdysozoa. Results support an ancestor of crown group ecdysozoans sharing an annulated vermiform body with a terminal mouth like Acosmia, but also possessing the pharyngeal armature and circumoral structures characteristic of Cambrian cycloneuralians and lobopodians. Conclusions Acosmia is the first taxon placed in the ecdysozoan stem group and provides a constraint to test hypotheses on the early evolution of Ecdysozoa. Our study suggests acquisition of pharyngeal armature, and therefore a change in feeding strategy (e.g. predation), may have characterised the origin and radiation of crown group ecdysozoans from Acosmia-like ancestors.

Herpetogaster from the early Cambrian of Nevada (Series 2, Stage 4) and its implications for the evolution of deuterostomes

2018 ◽  
Vol 156 (1) ◽  
pp. 172-178 ◽  
Author(s):  
JULIEN KIMMIG ◽  
RONALD C. MEYER ◽  
BRUCE S. LIEBERMAN
Keyword(s):  
Early Cambrian ◽  
Burgess Shale ◽  
Middle Cambrian ◽  
Stage 4 ◽  
First Occurrence

AbstractThe Pioche Formation of SE Nevada preserves a diverse soft-bodied fauna from the early and middle Cambrian (Series 2–3: Stage 4–5). While the fauna is dominated by arthropods, animals belonging to other taxa can be found. Here we document the first occurrence of Herpetogaster collinsi outside the Burgess Shale. Further, the specimens are from the Nephrolenellus multinodus biozone and thus represent the oldest occurrence of the species, as well as possibly the earliest soft-bodied deuterostomes in Laurentia.

scholarly journals A superarmored lobopodian from the Cambrian of China and early disparity in the evolution of Onychophora

2015 ◽  
Vol 112 (28) ◽  
pp. 8678-8683 ◽  
Author(s):  
Jie Yang ◽  
Javier Ortega-Hernández ◽  
Sylvain Gerber ◽  
Nicholas J. Butterfield ◽  
Jin-bo Hou ◽  
...  
Keyword(s):  
South China ◽  
Cambrian Explosion ◽  
Suspension Feeding ◽  
Early Cambrian ◽  
Early Paleozoic ◽  
Crown Group ◽  
Morphological Disparity ◽  
Stem Group ◽  
Velvet Worms ◽  
Mode Of Life

We describe Collinsium ciliosum from the early Cambrian Xiaoshiba Lagerstätte 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.

scholarly journals Presence of Naraoia Walcott, 1912 (Nektaspida, Arthropoda) in the middle Cambrian of Europe (Murero, NE Spain)

2018 ◽  
Vol 33 (1) ◽  
pp. 83
Author(s):  
Rodolfo Gozalo ◽  
Mª Eugenia Dies-Álvarez ◽  
José Antonio Gámez VIintaned ◽  
Juan B. Chirivella ◽  
Eladio Liñan
Keyword(s):  
British Columbia ◽  
First Record ◽  
Early Cambrian ◽  
Burgess Shale ◽  
Evolutionary Potential ◽  
Middle Cambrian ◽  
The Family ◽  
Ne Spain

 The genus Naraoia Walcott, 1912, a Burgess Shale-type fossil known from the lower and middle Cambrian of British Columbia (Canada), Idaho and Utah (USA), as well as from Yunnan and Guizhou provinces (China), is now reported from the middle Cambrian of Murero (Zaragoza, Spain), which is the first record in the Acadobaltic province. The only fragmented specimen found is determined as Naraoia sp., its age being Pardailhania multispinosa Zone (Drumian Stage). This new datum reinforces the hypothesis of the existence of a cosmopolitan faunal substrate in early Cambrian times, which is to some extent refl ected in the mid Cambrian by faunal groups of low evolutionary potential as the family Naraoiidae and other soft-bodied fossil taxa.

scholarly journals A possible case of inverted lifestyle in a new bivalved arthropod from the Burgess Shale

2019 ◽  
Vol 6 (11) ◽  
pp. 191350 ◽  
Author(s):  
Alejandro Izquierdo-López ◽  
Jean-Bernard Caron
Keyword(s):  
Phylogenetic Analysis ◽  
National Park ◽  
Suspension Feeder ◽  
The Body ◽  
Burgess Shale ◽  
Middle Cambrian ◽  
Bayesian Phylogenetic Analysis ◽  
Stem Group ◽  
Potential Case ◽  
Caudal Rami

The origin of the arthropod carapace, an enlargement of cephalic tergites, can be traced back to the Cambrian period. However, its disparity and evolution are still not fully understood. Here, we describe a new ‘bivalved’ arthropod, Fibulacaris nereidis gen. et sp. nov., based on 102 specimens from the middle Cambrian (Wuliuan Stage) Burgess Shale, Marble Canyon area in British Columbia's Kootenay National Park, Canada. The laterally compressed carapace covers most of the body. It is fused dorsally and merges anteriorly into a conspicuous postero-ventrally recurved rostrum as long as the carapace and positioned between a pair of backwards-facing pedunculate eyes. The body is homonomous, with approximately 40 weakly sclerotized segments bearing biramous legs with elongate endopods, and ends in a pair of small flap-like caudal rami. Fibulacaris nereidis is interpreted as a suspension feeder possibly swimming inverted, in a potential case of convergence with some branchiopods. A Bayesian phylogenetic analysis places it within a group closely related to the extinct Hymenocarina. Fibulacaris nereidis is unique in its carapace morphology and overall widens the ecological disparity of Cambrian arthropods and suggests that the evolution of a ‘bivalved' carapace and an upside-down lifestyle may have occurred early in stem-group crustaceans.

scholarly journals An exceptionally preserved euarthropod with unique feather-like appendages from the Chengjiang biota

2021 ◽  
Author(s):  
Dayou Zhai ◽  
Mark Williams ◽  
David J. Siveter ◽  
Derek J. Siveter ◽  
Thomas H.P. Harvey ◽  
...  
Keyword(s):  
Soft Part ◽  
Three Dimensional ◽  
Ct Scanning ◽  
Early Cambrian ◽  
Micro Ct ◽  
Burgess Shale ◽  
Terminal Seta ◽  
Stem Group ◽  
Chengjiang Biota

AbstractMicro-CT scanning of the Cambrian euarthropod Chuandianella ovata reveals unprecedented three-dimensional soft-part details. It has an elongate uniramous antennule and a short uniramous second appendage, followed by ten homonomous biramous appendages, each comprising a short paddle-shaped exopod and a unique feather-like endopod with at least 27 podomeres each of which bears a long blade-like endite with a short terminal seta. Based on its carapace and previously known soft-part anatomy C. ovata was compared with the Burgess Shale mandibulate euarthropod Waptia. However, Waptia has recently been shown to bear specialized head appendages that are interpreted as a mandible and maxillula, posterior to which are four appendages each with five-segmented endopods. In contrast, we interpret Chuandianella as an ‘upper’ stem-group euarthropod that possessed neither a differentiated mandible nor a maxillula. Chuandianella further demonstrates that early Cambrian ‘upper’ stem-group euarthropods were experimenting with a range of different limb arrangements and morphologies.

The Burgess Shale arthropod Mollisonia (M. sinica new species): new occurrence from the Middle Cambrian Kaili fauna of southwest China

2002 ◽  
Vol 76 (6) ◽  
pp. 1106-1108 ◽  
Author(s):  
Xingliang Zhang ◽  
Yuanlong Zhao ◽  
Ruidong Yang ◽  
Degan Shu
Keyword(s):  
Southwest China ◽  
Middle Part ◽  
Guizhou Province ◽  
Cambrian Explosion ◽  
Early Cambrian ◽  
Burgess Shale ◽  
Middle Cambrian ◽  
Lowermost Part ◽  
Dark Green ◽  
Chengjiang Lagerstätte

The Early Cambrian Chengjiang Lagerstätte, Yunnan Province, Southwest China, has become one of the most celebrated Cambrian fossil Lagerstatten not only for perhaps the earliest biota of soft-bodied organisms in the Phanerozoic (Yuan and Zhao, 1999; Zhang et aI., 2001; but see Budd and Jensen, 2000), but also for a number of significant discoveries (Shu et al., 1996a, 1996b, 1999a, 1999b, 2001), proven to be of particular importance for our understanding the Cambrian explosion. Also in Southwest China, Guizhou Province, there is a very significant, although less acclaimed, Middle Cambrian soft-bodied fauna as well, namely the Kaili fauna, which occurs in the Kaili Formation in Kaili area (Kuizhou). The age of the Kaili Formation ranges from late Early to early Middle Cambrian. Regionally, the Kaili Formation is about 222 m thick and consists of three parts. The lowermost part (late Early Cambrian, about 55 m thick) is dominated by thin, calcareous siltstone strata interbedded with limestone layers at the base. The middle part (early Middle Cambrian, ca. 123 m) consists of dark green mudstone and shale, while the uppermost part (ca. 44 m) is composed of interbedded limestone and silty shale. The Kaili fauna is derived from mudstones in the middle part of the formation (Zhao et aI., 1994; Zhu et aI., 2000).

scholarly journals New records of Burgess Shale-type taxa from the middle Cambrian of Utah

2015 ◽  
Vol 89 (3) ◽  
pp. 411-423 ◽  
Author(s):  
Simon Conway Morris ◽  
Paul A. Selden ◽  
Glade Gunther ◽  
Paul G. Jamison ◽  
Richard A. Robison
Keyword(s):  
New Species ◽  
North America ◽  
Northwest Territories ◽  
Type Species ◽  
New Records ◽  
Western North America ◽  
Burgess Shale ◽  
Middle Cambrian ◽  
Stem Group ◽  
A New Species

AbstractCambrian strata of the Laurentian craton contain numerous examples of Burgess Shale–type faunas. Although displaying a more or less concentric distribution around the cratonal margin, most faunal occurrences are in present-day western North America, extending from the Northwest Territories to California. Nevertheless, the soft-bodied and lightly skeletalized fossils in most of these Lagerstätten are highly sporadic. Here, we extend knowledge of such Middle Cambrian occurrences in Utah with reports of four taxa. An arthropod from the Marjum Formation, Dytikosicula desmatae gen. et sp. nov., is a putative megacheiran. It is most similar to Dicranocaris guntherorum, best known from the younger Wheeler Formation, but differs primarily in the arrangement of pleurae and overall size. Along with a specimen of ?Yohoia sp, a new species of Yohoia, Y. utahana sp. nov., is described. It differs from the type and only known species, Y. tenuis, principally in its larger size and shorter exopods; it is the first description of this genus from outside the Burgess Shale. A new species of a stem-group lophotrochozoan from the Spence Shale, Wiwaxia herka sp. nov., possesses a palisade of dorso-lateral spines that are more robust and numerous than the type species of Wiwaxia, W. corrugata. Another notable taxon is Eldonia ludwigi from the Marjum Formation, which is interpreted as a primitive ambulacrarian (assigned to the cambroernids) and a new specimen of the ?cnidarian Cambrorhytium from the Wheeler Shale is illustrated.

Middle Cambrian arthropods from Utah

2008 ◽  
Vol 82 (2) ◽  
pp. 238-254 ◽  
Author(s):  
Derek E. G. Briggs ◽  
Bruce S. Lieberman ◽  
Jonathan R. Hendricks ◽  
Susan L. Halgedahl ◽  
Richard D. Jarrard
Keyword(s):  
New Species ◽  
New Genera ◽  
Burgess Shale ◽  
Separate Species ◽  
Middle Cambrian ◽  
Stem Group ◽  
New Material ◽  
A New Species

The Middle Cambrian Spence Shale Member (Langston Formation) and Wheeler and Marjum Formations of Utah are known to contain a diverse soft-bodied fauna, but important new paleontological material continues to be uncovered from these strata. New specimens of anomalocaridids include the largest and smallest near complete examples yet reported from Utah. New material of stem group arthropods includes two new genera and species of arachnomorphs: Nettapezoura basilika and Dicranocaris guntherorum. Other new arachnomorph material includes a new species of Leanchoilia comparable to L. protogonia Simonetta, 1970; Leanchoilia superlata? Walcott, 1912; Sidneyia Walcott, 1911a; and Mollisonia symmetrica Walcott, 1912. L. protogonia from the Burgess Shale is confirmed as a separate species and is not a composite fossil. The first example of the trilobite Elrathia kingii preserving traces of the appendages is described. In addition, new material of the bivalved arthropods Canadaspis Novozhilov in Orlov, 1960; Branchiocaris Briggs, 1976; Waptia Walcott, 1912; and Isoxys Walcott, 1890 is described.

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