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Phoronids, together with brachiopods and bryozoans, form the animal clade Lophophorata. Modern lophophorates are quite diverse—some can biomineralize while others are soft‐bodied, they could be either solitary or colonial, and they develop through various eccentric larval stages that undergo different types of metamorphoses. The diversity of this clade is further enriched by numerous extinct fossil lineages with their own distinct body plans and life histories. In this review, I discuss how data on phoronid development, genetics, and morphology can inform our understanding of lophophorate evolution. The actinotrocha larvae of phoronids is a well documented example of intercalation of the new larval body plan, which can be used to study how new life stages emerge in animals with biphasic life cycle. The genomic and embryonic data from phoronids, in concert with studies of the fossil lophophorates, allow the more precise reconstruction of the evolution of lophophorate biomineralization. Finally, the regenerative and asexual abilities of phoronids can shed new light on the evolution of coloniality in lophophorates. As evident from those examples, Phoronida occupies a central role in the discussion of the evolution of lophophorate body plans and life histories. RESEARCH HIGHLIGHTS: Phoronida is a crucial clade for the understanding of lophophorate evolution. The recent findings on their development, combined with new fossils, allow a reconstruction of how larvae, armor, and asexuality evolved in Lophophorata. [ABSTRACT FROM AUTHOR]

Cambrian Series 2 shelly fossils from thick carbonate successions in East Antarctica have received limited systematic treatment through the 20th century. Described here are the East Antarctic camenellan tommotiids from the Shackleton Limestone in the Central Transantarctic Mountains and the Schneider Hills limestone in the Argentina Range. This material comes from both newly sampled collections and incompletely described material from older collections. The assemblage supports correlation to the Dailyatia odyssei Zone and Pararaia janeae Trilobite Zone of South Australia, with the newly examined specimens of Dailyatia decobruta from the Shackleton Limestone providing direct correlation to the Mernmerna Formation of the Ikara-Flinders Ranges and White Point Conglomerate of Kangaroo Island. These East Antarctic assemblages include five species referred to Dailyatia, in addition to an undetermined kennardiid species and fragments of the problematic Shetlandia multiplicata. The results further corroborate the notion that fossiliferous carbonate clasts found on King George Island were sourced from the same carbonate shelf as the Shackleton Limestone, with the taxon S. multiplicata found in both units. The Schneider Hills limestone in the Argentina Range has yielded sclerites of Dailyatia icari sp. nov., currently only known from this location.

The lower Cambrian (Series 2) White Point Conglomerate (WPC) on Kangaroo Island, South Australia contains exotic clasts representing a diverse array of lithologies, including metamorphics, chert, sandstone, and abundant carbonates, notably archaeocyath-rich bioclastic limestone. Acetic acid digestion of the WPC bioclastic limestone clasts reveals a diverse shelly fauna. This assemblage includes abundant organophosphatic brachiopods such as Cordatia erinae Brock and Claybourn gen. et sp. nov., Curdus pararaensis, Eodicellomus elkaniformiis, Eohadrotreta sp. cf. E. zhenbaensis, Eoobolus sp., Kyrshabaktella davidii, and Schizopholis yorkensis. Additional shelly taxa include the solenopleurid trilobite Trachoparia? sp., the tommotiids Dailyatia odyssei, Dailyatia decobruta Betts sp. nov., Kelanella sp., and Lapworthella fasciculata, spines of the bradoriid arthropod Mongolitubulus squamifer, and several problematica, such as Stoibostrombus crenulatus and a variety of tubular forms. The upper age limit for the WPC is constrained by biostratigraphic data from the overlying Marsden Sandstone and Emu Bay Shale, which are no younger than the Pararaia janeae Trilobite Zone (Cambrian Series 2, Stage 4). The shelly fossil assemblage from the WPC limestone clasts indicates an upper Dailyatia odyssei Zone (= Pararaia tatei to lower P. janeae trilobite zones), equivalent to the Atdabanian–early Botoman of the Siberian scheme. This contrasts with the previously suggested late Botoman age for the limestone clasts, based on the diverse archaeocyath assemblage. The minor age difference between the WPC and its fossiliferous limestone clasts suggests relatively rapid reworking of biohermal buildups during tectonically-active phases of deposition in the Stansbury Basin.

Cambrian Series 2 shelly fossils from thick carbonate successions in East Antarctica have received limited systematic treatment through the 20th century. Described here are the East Antarctic camenellan tommotiids from the Shackleton Limestone in the Central Transantarctic Mountains and the Schneider Hills limestone in the Argentina Range. This material comes from both newly sampled collections and incompletely described material from older collections. The assemblage supports correlation to the Dailyatia odyssei Zone and Pararaia janeae Trilobite Zone of South Australia, with the newly examined specimens of Dailyatia decobruta from the Shackleton Limestone providing direct correlation to the Mernmerna Formation of the Ikara-Flinders Ranges and White Point Conglomerate of Kangaroo Island. These East Antarctic assemblages include five species referred to Dailyatia, in addition to an undetermined kennardiid species and fragments of the problematic Shetlandia multiplicata. The results further corroborate the notion that fossiliferous carbonate clasts found on King George Island were sourced from the same carbonate shelf as the Shackleton Limestone, with the taxon S. multiplicata found in both units. The Schneider Hills limestone in the Argentina Range has yielded sclerites of Dailyatia icari sp. nov., currently only known from this location. [ABSTRACT FROM AUTHOR]

Tommotiida finds from the Lower Cambrian of the Khairkhan Section located within the Central Tuva trough were characterized for the first time. The assemblages of small shelly fossils are represented by species of the genera typical for the Upper Atdabanian age, such as Tannuolina, Kelanella, Lugoviella, and Microdictyon. Sclerites of four different morphotypes were identified for the Lugoviella ojmuranica species. [ABSTRACT FROM AUTHOR]

The lower Cambrian (Series 2) White Point Conglomerate (WPC) on Kangaroo Island, South Australia contains exotic clasts representing a diverse array of lithologies, including metamorphics, chert, sandstone, and abundant carbonates, notably archaeocyath-rich bioclastic limestone. Acetic acid digestion of the WPC bioclastic limestone clasts reveals a diverse shelly fauna. This assemblage includes abundant organophosphatic brachiopods such as Cordatia erinae Brock and Claybourn gen. et sp. nov., Curdus pararaensis, Eodicellomus elkaniformiis, Eohadrotreta sp. cf. E. zhenbaensis, Eoobolus sp., Kyrshabaktella davidii, and Schizopholis yorkensis. Additional shelly taxa include the solenopleurid trilobite Trachoparia? sp., the tommotiids Dailyatia odyssei, Dailyatia decobruta Betts sp. nov., Kelanella sp., and Lapworthella fasciculata, spines of the bradoriid arthropod Mongolitubulus squamifer, and several problematica, such as Stoibostrombus crenulatus and a variety of tubular forms. The upper age limit for the WPC is constrained by biostratigraphic data from the overlying Marsden Sandstone and Emu Bay Shale, which are no younger than the Pararaia janeae Trilobite Zone (Cambrian Series 2, Stage 4). The shelly fossil assemblage from the WPC limestone clasts indicates an upper Dailyatia odyssei Zone (= Pararaia tatei to lower P. janeae trilobite zones), equivalent to the Atdabanian-early Botoman of the Siberian scheme. This contrasts with the previously suggested late Botoman age for the limestone clasts, based on the diverse archaeocyath assemblage. The minor age difference between the WPC and its fossiliferous limestone clasts suggests relatively rapid reworking of biohermal buildups during tectonically-active phases of deposition in the Stansbury Basin. [ABSTRACT FROM AUTHOR]

Abstract The eccentrothecimorph tommotiid Paterimitra pyramidalis Laurie, 1986, was previously only known from lower Cambrian rocks of the Northern Territory and South Australia. Herein, we document the first occurrence of P. pyramidalis from the Xinji Formation in the Shuiyu section at Ruicheng County, Shanxi Province, located at the southwestern margin of the North China Platform. This represents the first report of a tommotiid taxon from lower Cambrian strata of the North China Platform. All three sclerite types that characterise the scleritome of P. pyramidalis have been recovered and are described, permitting definitive identification to species level. The discovery of P. pyramidalis from the North China Platform not only greatly extends the palaeogeographic range of this distinctive tommotiid taxon, but also supports planktotrophic development of larvae in Paterimitra as a stem group brachiopod. The discovery of P. pyramidalis supports a Cambrian, Epoch 2, late Age 3 to early Age 4 age for the shelly fossil fauna from the Xinji Formation and indicates a close palaeogeographic position between the North China Platform and Australian East Gondwana during the early Cambrian. Graphical abstract Unlabelled Image Highlights • This is the first discovery of tommotiid Paterimitra pyramidalis from the Cambrian Epoch 2 of North China. • This discovery extends the palaeogeographic range of this taxon, supporting planktotrophic development of the larvae. • It indicates a close palaeogeographic position between North China and Australian East Gondwana during the Cambrian. [ABSTRACT FROM AUTHOR]

Three specimens of a new eccentrothecimorph tommotiid are described from the Paralleldal Formation of North Greenland. The specimens are all tubular structures composed of a number of individual sclerites. The sclerites were arranged in rings, which fused to form a rigid tube during ontogeny. The tube has a basal aperture presumably allowing attachment to a hard substrate. In morphology, both individual sclerites and the tubular scleritome are remarkably similar to specimens of Eccentrotheca from South Australia. However, the Greenland specimens are silicified and may have been either weakly mineralised or calcareous in original composition. In this respect they differ from all previously known tommotiids, considerably expanding the ultrastructural disparity of the Tommotiida and allowing comparison to a new range of possible lophotrochozoan fossils. [ABSTRACT FROM AUTHOR]

Among extant animals, Lophotrochozoa accounts for the majority of phyla. 1 This bilaterian clade radiated rapidly during the Cambrian explosion, obfuscating its phylogenetic relationships and rendering many aspects of its early evolution uncertain. Many early lophotrochozoans are known only from isolated skeletal microfossils, "small shelly fossils," often derived from larger animals with complex multi-element skeletons. 2 The discovery of articulated fossils has revealed surprising insights into the animals from which these skeletal pieces were derived, such as paired shells in the mollusc Halkieria. 3 Tommotiids are a key group of phosphatic early skeletal fossils that first appear in the late early Cambrian. 4,5 Although their affinities were previously obscure, discoveries of partial scleritomes and investigations of growth and microstructure 6 provide links with Brachiopoda 7,8 and Phoronida, 9 two of the lophophorate phyla. By contrast, the body plan of camenellan tommotiids remains a palaeontological mystery, with hypothetical reconstructions representing motile, benthic, dorsally armored worms. 4,10 Here, we describe an articulated camenellan (Wufengella bengtsoni gen. et sp. nov.) from the Cambrian Chengjiang Biota, China, revealing the morphology of the scleritome and the first soft tissues from an adult tommotiid. Wufengella carries two dorsal rows of sclerites in a highly asymmetric arrangement, flanked by smaller, cap-shaped sclerites. The scleritome was fringed by iterated fascicles of chaetae and two layers of flattened lobes. Phylogenetic analysis confirms that camenellans occupy a deep branch in lophophorate phylogeny, prior to the acquisition of a sessile lifestyle. Wufengella reveals direct evidence for a metameric body plan reminiscent of annelids early in the evolutionary history of lophophorates. 11,12 [Display omitted] • We describe the first articulated camenellan tommotiid, from the early Cambrian • Camenellans had seriated, annelid-like chaetal bundles and body outgrowths • Early lophophorates were armored, vagile animals prior to becoming sessile • Soft anatomy is vital for understanding the oldest skeletal fossils Guo et al. describe the first known articulated camenellan tommotiid, a group of enigmatic Cambrian animals that have been difficult to classify based on disarticulated microfossils. Camenellans were vagile armored worms, with affinities to living lophophorates (e.g., brachiopods), suggesting a motile last common ancestor. [ABSTRACT FROM AUTHOR]

The camenellan tommotiid Dailyatia is one of the most common fossils in shallow water carbonates from Cambrian Stages 2-4 in South Australia (Arrowie and Stansbury basins). Six species of Dailyatia are documented and new terminology for describing camenellan sclerites is introduced. Dailyatia sclerites are found in three fundamental sclerite types (A-C), each of which may be present in one to three sub-types depending on species. The previously described species Dailyatia ajax Bischoff 1976 and D. macroptera (Tate 1892) are revised and four additional species are described for the first time from South Australia. These include D. odyssei Evans & Rowell 1990, previously known only from Antarctica, and two new species; D. bacata sp. nov. and D. helica sp. nov. as well as a species left under open nomenclature. Two of the recognised species (D. macroptera and D. helica) occur in two different ecophenotypic variants. Species and variants are defined by differences in sclerite types present in the scleritome, sclerite morphology and ornament. The sclerites of Dailyatia are finely laminated with distal expansion of laminae supporting the prominent concentric ribs. The external surface is covered by a fine reticulate network which indicates that the sclerites were at least partly embedded in soft integument. The pattern of incremental growth reveals specific initial and possible gerontic growth stages with unique surface sculptures. Evidence of physical damage and growth disturbances is common in Dailyatia sclerites and many specimens reveal preferential abrasion of the apex. Apical canals are present in all sclerites and are connected to specialised internal apical structures. The internal surface of the sclerites in most species reveals raised platforms and depressed, scar like areas forming unique patterns in each sclerite type, presumably representing muscular attachment. Two specimens revealing ontogenetic fusion of Dailyatia sclerites have been recovered. Based on all available evidence, a new reconstruction of the Dailyatia scleritome is proposed. In the reconstruction, a central row of A and paired B sclerites is flanked on both sides by one or two lateral rows of C sclerites. The exact number of sclerites may vary between species. This reconstruction is based on an assumed slug-like bodyplan and the Dailyatia animal is considered to be a vagrant, benthic animal living in and around archaeocyathan-microbial buildups and in other shallow water carbonate environments. [ABSTRACT FROM AUTHOR]

A carbonate bed of the Pardailhan Formation, early Cambrian, southern Montagne Noire (southern France), provided microfossils such as Hyolithellus sp., Torellella cf. mutila and Torellella sp. along with numerous disarticulated pieces of composite skeletons such as valves of the brachiopod Eoobolus priscus and of the bradoriid Monceretia erisylvia, and chancelloriid sclerites ( Chancelloria sp.). The assemblage also furnished a rich set of sclerites from the tommotiid Kelanella altaica. Five morphological variations of the latter have been identified. The presence of concentric ribs formed by distal inflation of selected shell laminae in Kelanella supports its assignment to the camenellans. More particularly, the presence of transverse structures within the internal cavity (septa) of Kelanella suggests a close relationship with the Lapworthellidae. However, the latter differ from Kelanella by the continuous morphological variation along their scleritome which is also composed of simple conical elements with uniform ornamentation. Several forms of Kelanella are similar to mitral and sellate sclerites of Camenella, whereas some other forms are comparable to Kennardia. The new material suggests that Kelanella occupies a transitional position between Lapworthellidae and the grouping of Tommotiidae and Kennardiidae. Such a phylogenetic position also implies that the number of sclerite morphotypes tends to decrease within the camenellan scleritome during evolution. [ABSTRACT FROM AUTHOR]

Early Middle Cambrian bituminous coquinoid limestones from a tectonically isolated outcrop in southwestern Kyrgyzstan yield a remarkably diverse fauna, with stem-group cnidarians, trilobites, rhynchonelliformean brachiopods, and other shelly fossils. The fossil site is in the northern foothills of the Turkestan Range and thus forms part of the westernmost extension of the South Tien Shan. The fauna includes two fairly well known trilobite species, Glabrella ventrosa Lermontova, 1940 and Dorypyge richthofeniformis Lermontova, 1940, that provide confident support for an Amgan age of the rocks. New described taxa include the stem-group cnidarian Cambroctoconus kyrgyzstanicus Peel sp. nov., the trilobite Olenoides sagittatus Geyer sp. nov., and the helcionelloid Manasoconus bifrons Peel gen. et sp. nov. Additional fossils within the samples include the trilobites Olenoides sp. A, Kootenia sp., and Pseudoeteraspis? sp.; the rhynchonelliform brachiopods Narynella cf. ferganensis (Andreeva, 1962), Narynella? sp., Austrohedra? sp. nov., and two species of uncertain generic affinity; the tommotiid Tesella sp.; the hyolithelminth Hyolithellus sp.; and the palaeoscolecid Hadimopanella oezgueli Gedik, 1977. Of particular interest is Cambroctoconus kyrgyzstanicus with an octagonal corallum and a sparsely septate calyx. [ABSTRACT FROM AUTHOR]

The tommotiid Paterimitra pyramidalis Laurie, 1986, is redescribed based on well-preserved material from the lower Cambrian Wilkawillina, Wirrapowie and Ajax limestones of the Flinders Ranges, South Australia. The material shows that the scleritome of Paterimitra pyramidalis includes three sclerite morphotypes (S1, S2 and L). Detailed shell microstructure studies show striking similarities with both the paterinid brachiopod Askepasma toddense and the tommotiid Eccentrotheca helenia, which strengthens the suggested evolutionary link between tommotiids and brachiopods. Based on the partly articulated specimens and similarities in shell microstructure and sclerite morphology with Eccentrotheca, Paterimitra pyramidalis is reconstructed as a tube-dwelling, epifaunal, sessile, filter-feeder with an organic pedicle-like attachment structure. The proposed reconstruction of the scleritome comprises a basal unit composed of one S1 and one S2 sclerite, as well as an unresolved number of L sclerites lining a coniform tubular structure. [ABSTRACT FROM AUTHOR]

The morphology and organophosphatic shell structure of the paterinate brachiopod Askepasma is documented using new and previously collected specimens from the lower Cambrian of South Australia. Lack of adequately preserved material has seen the majority of paterinate specimens previously reported from South Australia referred to the genus Askepasma and treated under open nomenclature. Large collections of paterinates from the lower Cambrian Wilkawillina, Ajax, and Wirrapowie limestones in the Arrowie Basin, South Australia have prompted redescription of the type species Askepasma toddense and the erection of a new species, Askepasma saproconcha sp. nov. Askepasma saproconcha sp. nov. currently represents the oldest known brachiopod from the lower Cambrian successions in South Australia with a FAD in pre-trilobitic (Terreneuvian, Cambrian Stage 2, lower Atdabanian) strata in the basal part of the Wilkawillina and Wirrapowie limestones. Askepasma toddense predominantly occurs in Abadiella huoi Zone equivalent strata (Unnamed Cambrian Series 2, Stage 3, middle-upper Atdabanian) in the upper part of the lower Wilkawillina,Wirrapowie, and Ajax limestones. The shell microstructure of Askepasma suggests a proximal stem group position within the Brachiopoda and similarities with tommotiid taxa provides further evidence that the ancestry of crown group brachiopods is firmly entrenched within the Tommotiida. [ABSTRACT FROM AUTHOR]

The first partially articulated scleritome of a tommotiid, Eccentrotheca sp., is described from the Lower Cambrian of South Australia. The Eccentrotheca scleritome consists of individual sclerites fused in a spiral arrangement, forming a tapering tube-shaped skeleton with an inclined apical aperture and a circular to subcircular cross section. Traditionally, tommotiid sclerites have been assumed to form a dorsal armor of imbricating phosphatic plates in slug-like bilaterians, analogous to the calcareous sclerites of halkieriids. The structure of the Eccentrotheca scleritome is here reinterpreted as a tube composed of independent, irregularly shaped sclerites growing by basal-marginal accretion that were successively fused to form a rigid, protective tubular structure. The asymmetrical shape and sometimes acute inclination of the apical aperture suggests that the apical part of the scleritome was cemented to a hard surface via a basal disc, from which it projected vertically. Rather than being a vagrant member of the benthos, Eccentrotheca most likely represented a sessile, vermiform filter feeder. The new data suggest that the affinities of Eccentrotheca, and possibly some other problematic tommotiids, lie with the lophophorates (i.e., the phoronids and brachiopods), a clade that also possesses a phosphatic shell chemistry and a sessile life habit. [ABSTRACT FROM AUTHOR]

The tommotiids are a significant component of the earliest skeletal animal remains in the fossil record, occurring in large numbers in the Lower Cambrian. Sclerites of the tommotiid genus Sunnaginia have been implicated as integral to hypotheses regarding the evolution of the brachiopod body plan, with a morphology intermediate between the unspecialized sclerites of the tubular Eccentrotheca and the specialized sclerites of the tannuolinids. Abundant Sunnaginia ? imbricata sclerites, of a broad ontogenetic spectrum, were recovered from the Comley Limestone, Lower Cambrian (Stages 3-4), Shropshire, UK and compared to Sunnaginia imbricata from the Aldan River, Siberia (uppermost Tommotian). New microstructural data, collected using synchrotron radiation X-ray tomographic microscopy, reveal a unique microstructure for Sunnaginia ? imbricata sclerites among the tommotiids; interlamellar cavities spanned by a series of continuous pillars, giving a colonnaded appearance contrasting to that of S. imbricata. These data refute the inclusion of Eccentrotheca within the Sunnaginiidae and highlight the need for a revision of suprageneric classification of the tommotiids. Rather, structural similarities between Sunnaginia sclerites and those of the tannuolinids suggest a close affinity to this group. Recent phylogenetic hypotheses place the tannuolinids as stem-linguliform brachiopods, with Paterimitra plus the paterinid (and possibly rhynchonelliform) brachiopods as their sister group. Our new data therefore resolve Sunnaginia as close to the node defining crown-Brachiopoda. However, the characters supporting this phylogenetic scheme cannot be consistently applied to all taxa, nor do they define a series of nested clades. We therefore suggest that a more thorough phylogenetic analysis is required in the light of the data presented here and other recent descriptions. [ABSTRACT FROM AUTHOR]