scholarly journals New opabiniid diversifies the weirdest wonders of the euarthropod lower stem group

2021 ◽  
Author(s):  
Stephen Pates ◽  
Joanna M. Wolfe ◽  
Rudy Lerosey-Aubril ◽  
Allison C. Daley ◽  
Javier Ortega-Hernández
Keyword(s):  
Cover Image ◽  
Burgess Shale ◽  
Additional Note ◽  
Worldwide Distribution ◽  
Stem Group ◽  
Lower Stem ◽  
Specimen Number

AbstractOnce considered ‘weird wonders’ of the Cambrian, the emblematic Burgess Shale animals Anomalocaris and Opabinia are now recognized as lower stem-group euarthropods. Anomalocaris and its relatives (radiodonts) had a worldwide distribution and survived until at least the Devonian, whereas - despite intense study - Opabinia remains the only formally described opabiniid to date. Here we reinterpret a fossil from the Wheeler Formation of Utah as a new opabiniid, KUMIP 314087. By visualizing the sample of phylogenetic topologies in treespace, our results fortify support for the position of KUMIP 314087 beyond the nodal support traditionally applied. Our phylogenetic evidence expands opabiniids to multiple Cambrian Stages spanning approximately five million years. Our results underscore the power of treespace visualization for resolving imperfectly preserved fossils and expanding the known diversity and spatiotemporal ranges within the euarthropod lower stem group.Additional noteThis work contains a new biological name. New names in preprints are not considered available by the ICZN. To avoid ambiguity, the new biological name is not included in this preprint, and the specimen number (KUMIP 314087) is used as a placeholder.Abstract FigureCover image.Artistic reconstruction of the new opabiniid from the Wheeler Formation, Utah, USA (Cambrian: Drumian). Artwork by F. Anthony.

Rare primitive deuterostomes from the Cambrian (Series 3) of Utah

2015 ◽  
Vol 89 (4) ◽  
pp. 631-636 ◽  
Author(s):  
Simon Conway Morris ◽  
Susan L. Halgedahl ◽  
Paul Selden ◽  
Richard D. Jarrard
Keyword(s):  
New Species ◽  
Fossil Record ◽  
Type Species ◽  
The Body ◽  
New Taxon ◽  
Burgess Shale ◽  
Anterior Section ◽  
Stem Group ◽  
Stratigraphic Range ◽  
New Discovery

AbstractThe fossil record of early deuterostome history largely depends on soft-bodied material that is generally rare and often of controversial status. Banffiids and vetulicystids exemplify these problems. From the Cambrian (Series 3) of Utah, we describe specimens of Banffia episoma n. sp. (from the Spence Shale) and Thylacocercus ignota n. gen. n. sp. (from the Wheeler Formation). The new species of Banffia Walcott, 1911 shows significant differences to the type species (B. constricta Walcott, 1911) from the Cambrian (Series 3, Stage 5) Burgess Shale, notably in possessing a prominent posterior unit but diminished anterior section. Not only does this point to a greater diversity of form among the banffiids, but also B. episoma indicates that the diagnostic median constriction and crossover of either side of the body are unlikely to be the result of taphonomic twisting but are original features. Comparisons extend also to the Cambrian (Series 2) Heteromorphus Luo and Hu in Luo et al., 1999 and, collectively, these observations support an assignment of the banffiids to the vetulicolians. The new taxon T. ignota represents the first discovery of a vetulicystid from beyond China and also significantly extends its stratigraphic range from Series 2 Cambrian into Series 3 Cambrian. Despite overall similarities in bodyplan, T. ignota differs from other vetulicystids in a number of respects, notably the possession of an anterior zone with broad tentacle-like structures. This new discovery is consistent with the vetulicystids representing stem-group ambulacrarians.

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.

Reassessment of the problematic Burgess Shale sponge Takakkawia lineata Walcott, 1920

2012 ◽  
Vol 49 (9) ◽  
pp. 1087-1095 ◽  
Author(s):  
Joseph P. Botting
Keyword(s):  
Organic Layer ◽  
Burgess Shale ◽  
Similar Morphology ◽  
Stem Group ◽  
The Family ◽  
Fine Microstructure ◽  
New Material ◽  
Primary Column

The monotypic Burgess Shale sponge genus Takakkawia Walcott, 1920, has been previously assigned to the Protomonaxonida, despite showing several unique features. A reassessment of the genus, including restudy of previously described material and the addition of new material that includes partially disarticulated specimens, has allowed a greatly modified understanding of its structure. The sponge possessed four primary columns (each divided into two) of highly modified spicules, with an outer organic layer extended into a unique, complex flange that shows a fine microstructure. The flanges within one column overlap to give the impression of radial fins, and each column is surmounted by an enlarged marginal spicule of similar morphology. Multi-rayed spicules are present both within the primary column architecture and as marginalia lining the osculum. The architecture most closely resembles Metaxyspongia Wu et al., 2005, which is placed into the Takakkawiidae. This restudy supports an interpretation of the family as a very early-branching sponge lineage, diverging within the early stem group of Silicea or prior to the separation of Calcarea and Silicea.

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 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.

Leanchoilia guts and the interpretation of three-dimensional structures in Burgess Shale-type fossils

Paleobiology ◽  
2002 ◽  
Vol 28 (1) ◽  
pp. 155-171 ◽  
Author(s):  
Nicholas J. Butterfield
Keyword(s):  
Lower Cambrian ◽  
Chemical Reactivity ◽  
Three Dimensional ◽  
Gut Contents ◽  
Phylogenetic Position ◽  
Internal Source ◽  
Last Common Ancestor ◽  
Burgess Shale ◽  
Stem Group ◽  
Deposit Feeding

The Burgess Shale arthropod Leanchoilia superlata Walcott 1912, commonly preserves a three-dimensional axial structure generally interpreted as gut contents. Thin-section examination shows this instead to be phosphatized biserially repeated midgut glands, including exceptional preservation of subcellular features. The preferential mineralization of these structures is related to their unusually high chemical reactivity and probably to an internal source of phosphate. Sub-millimetric lineations previously interpreted as annular musculature are in fact planar, sometimes radially arranged, subdivisions of these glands. Ventral rows of isolated phosphate patches appear to represent the same tissue.In extant arthropods, extensively developed midgut glands are related to a rich but infrequent diet with a primary function in storage. Their conspicuous occurrence in unambiguous fossil predators such as Sidneyia and Laggania (Anomalocaris) suggests they served a similar role in the Cambrian; by extension, their conspicuous occurrence in Leanchoilia suggests it was a predator or scavenger.Phosphatized midguts with a structure essentially indistinguishable from that of Leanchoilia are also found in Burgess Shale Odaraia, Canadaspis, Perspicaris, Sidneyia, Anomalocaris, and Opabinia. All are characterized by a distinctive sub-millimetric arrangement of planar elements that is not found in extant arthropods or trilobites, suggesting they diverged before the last common ancestor of extant forms; i.e., they represent stem-group arthropods.Three-dimensionally preserved guts are widely preserved in the Lower Cambrian Chengjiang biota but, unlike those in the Burgess Shale, appear to be filled with sediment. Although generally interpreted as evidence of deposit feeding, the form of these structures points to early permineralization of (sediment-free) midgut glands that were subsequently altered to clay minerals. There is no evidence of deposit feeding in the Chengjiang; indeed, there is a case to be made for deposit feeding not being generally exploited generally until after the Cambrian.Fossils with three-dimensionally preserved axes from the Lower Cambrian Sirius Passet biota have been interpreted as lobopodians; however, most of the putative lobopodian features find alternative interpretations as aspects of Leanchoilia-type midgut glands. Although Kerygmachela is reliably identified as a stem-group arthropod, its phylogenetic position remains unresolved owing to the non-preservation of critical external features and to the plesiomorphic nature of its Leanchoilia-type midgut.

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 morphology and phylogenetic significance ofKerygmachela kierkegaardiBudd (Buen Formation, Lower Cambrian, N Greenland)

1998 ◽  
Vol 89 (4) ◽  
pp. 249-290 ◽  
Author(s):  
Graham E. Budd
Keyword(s):  
Fossil Record ◽  
Lower Cambrian ◽  
Cephalic Region ◽  
The Other ◽  
Burgess Shale ◽  
Phylogenetic Significance ◽  
Long Tail ◽  
Caudal Region ◽  
Stem Group ◽  
Paraphyletic Group

AbstractSpecimens ofKerygmachela kierkegaardiBudd are described, from the Lower Cambrian Sirius Passet fauna of N Greenland. The cephalic region is characterised by a pair of stout unsegmented appendages each bearing long spinose processes, and an anterior mouth. The trunk shows alternating rows of tubercles and transverse annulations along the axis, to which are attached 11 pairs of gill-bearing lateral lobes and lobopodous limbs. The caudal region is small, and bears two long tail spines. There is some evidence for circular musculature arranged around the trunk and a dorsal, longitudinal sinus, and several details of the muscular pharynx have been preserved.The combination of characters found inKerygmachelaallows it to be allied with the lobopods, represented in the extant fauna by the onychophorans, tardigrades, and possibly the pentastomids, and in the Cambrian fossil record by a morphologically diverse set of taxa, some of which are not assignable to the extant groupings. It also shares important characters with the previously problematic Burgess Shale formsOpabinia regalisWalcott andAnomalocarisWhiteaves, and the Sirius Passet form Pambdelurion Budd. These taxa together form a paraphyletic group at the base of the clade of biramous arthropods. The position of the so-called ‘Uniramia’ remains unclear. It can be demonstrated from the reconstruction of the arthropod stem-group that full arthropod segmentation has a different derivation from that of the annelids. In line with other recent analyses, this suggests that the ‘Articulata’ of Cuvier should be dismantled, and the arthropods considered to be a group of protostomes which are phylogenetically distinct from the classic spiralians. Arthropod affinities may rather lie with the other moulting animals, in the so-called ‘Ecdysozoa’.

Banffia constricta, a putative vetulicolid from the Middle Cambrian Burgess Shale

2005 ◽  
Vol 96 (2) ◽  
pp. 95-111 ◽  
Author(s):  
Jean-Bernard Caron
Keyword(s):  
Deposit Feeder ◽  
Entire Body ◽  
Burgess Shale ◽  
Middle Cambrian ◽  
Anterior Section ◽  
New Class ◽  
Stem Group ◽  
Posterior Section

ABSTRACTAlthough Banffia constricta was first described in 1911, the affinities of this soft-bodied fossil animal have remained unclear. Banffia is redescribed here, on the basis of over 300 specimens. Banffia has a bipartite body measuring up to 10 cm in length. The entire body is axially twisted along a spiral, clockwise as seen from the front. The anterior section consists of two fused carapace-like units with a prominent crown-like structure at the anterior end surrounding the mouth. This crown-like structure is composed of three concentric circlets. A single antenniform outgrowth lies posterior to the mouth. The posterior section of Banffia is composed of 40 to 50 lightly sclerotised segments. The anus is terminal, and situated in a caudal notch. The gut is straight. Simple serially repeated structures along the gut may represent metameric mid-gut diverticulae. Banffia is considered to have been an epibenthic gregarious animal and possibly a deposit-feeder.Banffia is putatively classified as an end-member of the phylum Vetulicolia, in a new class, the Banffozoa. If the vetulicolids represent a stem-group deuterostome, the absence of gills and a possible endostyle in Banffia is problematic. The presence of mid-gut diverticulae in Banffia may represent a link with the protostomes.

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