Predation by early Cambrian trilobites on infaunal worms - evidence from the Swedish Mickwitzia Sandstone

Evidence of early Cambrian predation is found in trace fossils from the Mickwitzia Sandstone of VastergÖtland, Sweden. The arthropod burrow Rusophycw dispar was dug down to spreite burrows in such a manner that mere coincidence of place is unlikely. The predator is identified as an olenellacean trilobite, mainly through the presence of a cephalic impression. The prey, a worm that may have been a priapulid, was localized visually or chemically at the spreite-burrows apertures. The predator lacked legs specialized for seizing prey, as indicated by the parallel, but laterally displaced position of the Rusophycus above the spreite burrow. In this stance prey could be gripped by flexing the supposedly spinose legs of one side around it. When a spreite burrow of limited horizontal extension was encountered, parallel orientation was obtained prior to digging, probably through chemical sensing, whereas parallel orientation to an extended burrow required a number of diggings. These traces are important evidence of early Cambrian predation and of the predatorial capability of trilobites. □ Lower Cambrian, Sweden predation, trilobites, priapulids , Rusophycus.     

The function of forks: Isotelus‐type hypostomes and trilobite feeding

Hegna, T.A. 2010: The function of forks: Isotelus‐type hypostomes and trilobite feeding. Lethaia, Vol. 43, pp. 411–419. Despite previous investigations, the function of the forked morphology of asaphid trilobite hypostomes is enigmatic. The focus of this study is the large and robust forked hypostome of the largest known genus of trilobite, Isotelus, and the independently‐derived forked hypostome of Hypodicranotus, the longest hypostome relative to body size of any trilobite. Although the trilobite hypostome is analogous to the labrum in other arthropods, forked hypostomes lack an obvious modern functional counterpart. The Isotelus hypostome is distinguished from other trilobite hypostomes by closely‐spaced terrace ridges on a greatly thickened inner surface of the forked posterior margin, with the scarp of the terrace facing antero‐ventrally. This is compatible with a grinding function, suggesting possible limb differentiation to complement this structure. The inner face of the tine (one of the two, prominent, sub‐parallel posterior projections) is also unique in that it has a microstructure which is evident in section, running perpendicular to the surface. Macropredatory and filter‐feeder roles are ruled out, and previous characterizations of the hypostome as knife‐like or serrated are rejected. Its function is incompatible with that of other non‐asaphid trilobites with forked hypostomes, like the remopleuridid Hypodicranotus, which lack similar terrace ridges and thickened inner‐edge cuticle. □Arthropoda, Asaphida, ecology, functional morphology, Trilobita.     

Tonganoxichnus a new insect trace from the Upper Carboniferous of eastern Kansas

Upper Carboniferous tidal rhythmites of the Tonganoxie Sandstone Member (Stranger Formation) at Buildex Quarry, eastern Kansas, USA, host a relatively diverse arthropod-dominated ichnofauna. Bilaterally symmetrical traces displaying unique anterior and posterior sets of morphological features are well represented within the assemblage. A new ichnogenus, Tonganoxichnus, is proposed for these traces. T. buildexensis, the type ichnospecies, has an anterior region characterized by the presence of a frontal pair of maxillary palp impressions, followed by a head impression and three pairs of conspicuous thoracic appendage imprints symmetrically opposite along a median axis. The posterior region commonly exhibits numerous delicate chevron-like markings, recording the abdominal appendages, and a thin, straight, terminal extension. T. buildexensis is interpreted as a resting trace. A second ichnospecies, T. ottawensis, is characterized by a fan-like arrangement of mostly bifid scratch marks at the anterior area that records the head- and thoracic-appendage backstrokes against the substrate. The posterior area shows chevron-like markings or small subcircular impressions that record the abdominal appendages of the animal, also ending in a thin, straight, terminal extension. Specimens display lateral repetition, and are commonly grouped into twos or threes with a fix point at the posteriormost tail-like structure. T. ottawensis is interpreted as a jumping structure, probably in connection with feeding purposes. The two ichnospecies occur in close association, and share sufficient morphologic features to support the same type of arthropod producer. T. buildexensis closely mimics the ventral anatomy of the tracemaker, whereas T. ottawensis records the jumping abilities of the animal providing significant ethologic and paleoecologic information. The presence of well-differentiated cephalic, thoracic, and abdominal features, particularly in T. buildexensis, resembles the diagnostic tagmosis and segmentation of insects. Detailed analysis of trace morphology and comparison with described Paleozoic insect fossils and extant related forms suggest a monuran as the most likely tracemaker.     

Burrowing trilobite caught in the act

A trace fossil associated with its assumed in situ maker, a holaspid specimen of the trilobite Agraulos ceticephalus (Barrande in Notice préliminaire sur le Systême Silurien et les trilobites de Bohême, Leipzig, 1846), is reported from the middle Cambrian Buchava Formation (Drumian Stage) of the Skryje-Tyřovice Basin, Czech Republic. The ichnofossil is preserved on the surface of a mudstone, behind the posterior part of the intact trilobite exoskeleton; this natural association is interpreted as mortichnia. Possible mode of life and feeding strategy of the trilobite genus Agraulos are discussed. For the association of a fodichnion with its producer preserved in situ (atop, in, or at the end of its trace fossil), the designation fodichnial association is proposed.     

Legs in the trilobite Rhenops from the Lower Devonian Hunsrück Slate

A specimen of the dalmanitacean trilobite Rhenops sp. cf. R. anserinus with ventral appendages is described and discussed. It is shown to have 1 pair of antennae, 4 pairs of cephalic legs, 11 pairs of thoracic legs, and 9(?) pairs of pygidial legs. The pygidial legs differ clearly from those of the thorax in their construction and are also smaller and more closely spaced. Of the outer appendage branch a few sets of lamellar spines are visible. D Trilobita, appendages, segmentation. Vom dalmanitiden Trilobiten Rhenops sp. cf. R. anserinus wird ein Exemplar mit ventralen Extremitaten beschrieben und diskutiert. Es hat 1 Antennenpaar, 4 Kopfbeinpaare, 11 Thorakalbeinpaare, und 9(?) Pygidium-Beinpaare. Die Pygidium-Beinpaare unterscheiden sich in ihrer Konstruktion klar von den Thorakalbeinpaaren. Sie sind kiirzer, und der Abstand zueinander ist schmaler. Lamellendornen (sogen-annte ‘Kiemenanhange’) sind an einigen wenigen Aussenasten sichtbar.     

山东寒武系苗岭统三叶虫消化系统的化石证据

三叶虫是寒武纪演化动物群中最引人注目的成员之一,其内部解剖结构一直以来受到广泛关注.与其他非生物矿化软体结构相比,三叶虫的消化系统更容易留下化石记录,为探索其内部结构提供了难得的机会.本文描述了来自山东省潍坊市寒武系馒头组的Proasaphiscus,Lioparia,Deiradonyx和Iranoleesia,以及...     

Rusophycus by Any Other Name Is Still Rusophycus carleyi

Rusophycus carleyi (James, 1885 James, J. F. 1885. The fucoids of the Cincinnati Group, Pt. 2. Journal of the Cincinnati Society of Natural History, 7:151–166. [Google Scholar]) is an ichnospecies that encompasses a variety of sizes and morphological variations that can be attributed to substrate-organism interaction(s) and taphonomic variation(s). R. carleyi ranges from the Cambrian to the Late Ordovician, with a cosmopolitan (global) distribution. Four ichnospecies are identified as junior synonyms of R. carleyi: morgati, moyensis, polonicus and radialis.     

Integrated sedimentological,ichnological and sequence stratigraphical studies of the Koti Dhaman Formation (Tal Group), Nigali Dhar Syncline,Lesser Himalaya,India: paleoenvironmental,paleoecological, paleogeographic significance

Abstract

Integrated ichnology, sedimentology and sequence stratigraphy of the Lower Quartzite Member to the Arkosic Sandstone Member of the Koti Dhaman Formation (Cambrian Series 2, Stage 4), Tal Group, Nigali Dhar Syncline, Lesser Himalayan lithotectonic zone are presented. Trilobite traces of Gondwanan affinity i.e., Cruziana salomonis, Cruziana fasciculata, Rusophycus dispar and Rusophycus burjensis are recorded along with Arenicolites isp. and Skolithos isp. from the Lower Quartzite Member. A rich and diverse ichnoassemblage attributed to the Cruziana ichnofacies is described for the first time from the Arkosic Sandstone Member of the same formation. Seven ichnofossil assemblages, i.e., Cruziana-Rusophycus, Planolites-Palaeophycus, Cruziana problematica, Diplichnites, Cochlichnus anguineus, Bergaueria perata and Psammichnites gigas have been recognized in the Lower Quartzite to Arkosic Sandstone members of the Koti Dhaman Formation. Seven sedimentary facies i.e., sandstone–shale facies (FT1), cross-bedded (trough and planar) sandstone (FT2), bedded sandstone facies (FT3), shale facies (FT4), shale–sandstone facies (FT5), shale-rippled sandstone facies (FT6) and planar and trough cross-laminated sandstone (FT7) and four facies associations FA1-FA4 are identified in the Koti Dhaman Formation. The formation contains shallowing upward parasequences of a tidal flat complex. Overall, two major events are recognized: i) the break in sedimentation between the Lower Quartzite Member and the overlying Shale Member probably related to forced-regressive event and ii) the facies shift from FT6 to FT7 of the Arkosic Sandstone Member represents an erosive transgressive event; the surface is interpreted as wave ravinement surface, which also serves as a sequence boundary. Integrated ichnology, sedimentology and sequence stratigraphic studies indicate that the Lower Quartzite Member was deposited in a shallow subtidal sand sheet complex and tidal flat complex; the Shale Member was deposited in a mud flat setting of a tidal flat complex, and the Arkosic Sandstone Member in a mixed-flat (tidal flat complex) to sand sheet complex front and margin (subtidal sand sheet complex). Overall, the lower to middle part of the Koti Dhaman Formation represents a tide-dominated shallow subtidal–intertidal to mud-flat subenvironments of the tidal flat complex. A palaeogeographic reconstruction of lower Cambrian (516–514?Ma) is presented based on the distribution of trilobite traces from the Lesser Himalaya and the Bikaner–Nagaur area of Peninsular India (eastern Gondwana), Egypt, Jordan, Turkey (western Gondwana) and Canada (Avalonia).     

An early Cambrian chelicerate from the Emu Bay Shale,South Australia

The Emu Bay Shale Lagerstätte (Cambrian Series 2, Stage 4) occurs on the north coast of Kangaroo Island, South Australia. Over 50 species are known from here, including trilobites and non‐biomineralized arthropods, palaeoscolecids, a lobopodian, a polychaete, vetulicolians, nectocaridids, hyoliths, brachiopods, sponges and chancelloriids. A new chelicerate, Wisangocaris barbarahardyae gen. et sp. nov., is described herein, based on a collection of some 270 specimens. It is up to 60 mm long, with the length of the cephalic shield comprising about 30% that of the exoskeleton. The cephalic margin has three pairs of bilaterally‐symmetrical small triangular spines. A pair of small eyes is placed well forwards on the ventral margin of the cephalic shield. The trunk comprises 11 segments that increase in length while narrowing posteriorly, each possibly bearing a pair of biramous appendages; the most posterior segment is almost square whereas the others are transversely elongated. The spatulate telson is proportionately longer than in taxa such as Sanctacaris, Utahcaris and Leanchoilia. Up to eight (?four pairs) of 3 mm‐long elements bearing alternating inward‐curving short and long spines beneath the cephalic shield are interpreted as basipodal gnathobases, part of a complex feeding apparatus. A well‐developed gut includes a stomach within the cephalic shield; it extends to the base of the telson. In a few specimens there are shell fragments within the gut, including those of the trilobite Estaingia bilobata (the most common species in the biota); these fragments have sharp margins and extend across the gut lumen. The species may have been a predator or a scavenger, ingesting material already broken up by a larger predator/scavenger. The morphology of this taxon shares many overall body features with Sanctacaris, and some with Sidneyia, particularly its gnathobasic complex. These chelicerate affinities are corroborated by phylogenetic analyses.     

Palaeoecology and evolutionary implications of enrolled trilobites from the Kushan Formation,Guzhangian of North China

Damesella paronai is the earliest enrolled odontopleurid trilobite to be found in the fossil record. Whereas its interlocking devices were very poorly developed, its trunk shows advanced articulations, which only lack an articulating facet, though an anterior notch is present in the outer part of each pleura. Its body pattern and structures did not allow it an encapsulated enrolment style. On the other hand, it is coeval with the early asaphid Monkaspis daulis, found in the same beds and at the same level. This co-inhabiting trilobite had a more advanced structure that enabled it to achieve a fully enrolled, encapsulated style. These superior structures enhance the preservation of enrolled specimens of M. daulis, and it seems to be generally the case that more elegant structures actually improve preservation. The evolutionary trends of the lineages of these two trilobites show that while odontopleurids were very conservative, using the same enrolment style throughout their history, the asaphids developed different enrolment styles, which was one factor in giving them a capacity to occupy different ecological niches and a greater range of environments.     

A Curious Rusophycus (Arthropod Ichnofossil) Assemblage from the Upper Ordovician of Ontario,Canada

The ichnogenus Rusophycus includes a wide range of short bilobate excavations generally attributed to variable feeding behaviors of arthropods, especially trilobites. An unusual Rusophycus assemblage from Upper Ordovician Georgian Bay Formation in Ontario departs radically from previously described examples and presents new challenges for understanding the behavior represented by these traces. This specimen is unique in the arrangement of multiple Rusophycus burrows in a circular, lens-shaped array (as opposed to a linear or random arrangement typical of other Rusophycus assemblages). The size and shape of the individual Rusophycus components are consistent with traces attributed to the coeval trilobite Flexicalymene. Multiple Rusophycus assemblages likely reflect aggregations of trilobites in response to a local concentration of food. The topology of this particular Rusophycus assemblage suggests that the trilobites opportunistically exploited a rich and narrowly restricted food source, perhaps the decaying remains of a buried organism.     

Trace fossils from arenig flysch sediments of eire and their bearing on the early colonisation of the deep seas

A sequence of Lower Ordovician (Arenig) turbidites in Co. Wexford, Eire, has yielded one of the earliest diverse ichnofaunas yet recorded from deep water sediments comprising: Chondrites, Glockerichnus, Gordia, Helminthopsis, Lorenzinia, Neonereites, Palaeophycus, Paleodictyon, Planolites, Sublorenzinia, Taenidium, Taphrhelminthopsis, Teichichnus and Tomaculum. This ichnofauna is critical in any analysis of the colonisation of the deep seas by trace fossil‐producing animals.

A world‐wide review shows that the earliest trace fossils are mainly from Late Precambrian shelf sea environments, but many more evolved during very rapid diversification in the pre‐trilobite Lower Cambrian.

There was little increase in diversity in shallow water after the Lower Cambrian but a progressive colonisation of the deep ocean took place and this accelerated during the Ordovician, when the main lineages of deep sea trace fossils were established there. Rosetted, patterned, meandering and simple spiral forms evolved in shallow water in the Upper Precambrian and pre‐trilobite Lower Cambrian and only later migrated into the deep sea, whereas complex, closely programmed, spiral traces may have evolved there.     

贵州台江下-中寒武统凯里组遗迹化石群落与环境关系的探讨

通过贵州台江凯里组中丰富的、分异度较高的、以原地埋藏为特征的遗迹化石的研究,探讨凯里组遗迹化石群落的沉积环境和埋藏环境。凯里组遗迹化石群落以节肢动物和软体动物的停息迹、爬行迹和游泳迹占优势,浅层内生爬行觅食潜穴和系统觅食潜穴占有一定的地位,也见有浅的居住滤食性潜穴,属Seilacher的Cruziana遗迹相,为正常浪基面和风暴浪基面之间的浅海软质基底陆棚低能环境,那里盐度正常、光照充足、含氧量充分、水体平静、沉积速率较快。在此环境中,浮游、游泳以及底栖爬行和固着生物类型大量地生长、繁殖和活动,表生遗迹和浅层内生遗迹十分丰富。生物死亡后的腐烂和分解,使得食泥生物大量繁盛。随着沉积物的覆盖和被埋藏生物遗体的分解、腐烂,沉积物内部还原能力逐渐增强,导致分解和腐烂过程终止。     

SOME TRILOBITE RESTING AND CRAWLING TRACES

An attempt is made to explain the formation of smooth trilobite resting traces ( Rusophycus ) and some features associated with crawling and digging trails, Cruziana. Smooth resting traces are frequently current orientated, and it is thought that the scouring action of water currents was largely responsible for their formation. In Cruziana the V-shaped herringbone pattern points in an opposite direction to that of the line of movement. Sets of scratches which make up this pattern explain some aspects of appendage movement.     

Inferring internal anatomy from the trilobite exoskeleton: the relationship between frontal auxiliary impressions and the digestive system

Lerosey‐Aubril, R., Hegna, T.A. & Olive, S. 2011: Inferring internal anatomy from the trilobite exoskeleton: the relationship between frontal auxiliary impressions and the digestive system. Lethaia, Vol. 44, pp. 166–184. The digestive system of trilobites is rarely preserved. As a result, many aspects of its organization remain unknown. Fortunately, the exoskeleton sometimes preserves evidence of soft‐tissue attachment sites that can be used to infer internal anatomy. Among them are the frontal auxiliary impressions (FAIs), probable soft‐tissue insertion sites located on the fronto‐median glabellar lobe of some trilobites. FAIs are herein described in the Carboniferous trilobite Phillipsia belgica Osmólska 1970 – representing the only known example of such structures in the Proetida and their youngest occurrence. A taphonomic scenario is proposed to explain their variable preservation. Although particularly common in the Phacopina, FAIs or FAI‐like structures are also found in several orders that differ greatly. Comparisons with modern analogues suggest that FAIs might represent attachment sites for extrinsic muscles associated with a differentiated crop within the foregut. A review of purported remains of the trilobite digestive system indicates that it usually consisted of a tube‐like tract flanked by a variable number of metamerically paired diverticulae. Its anterior portion is not particularly individualized, except in a few specimens that might hint at the presence of a crop. This differentiation of a crop might have constituted a secondarily evolution of the foregut in trilobites, occurring independently in different clades. Accompanied by a strengthening of associated extrinsic muscles, this modification of the foregut might explain the presence of more conspicuous muscle insertion sites on the glabella. Study of FAIs might therefore provide new data on the anatomy of the foregut in trilobites and evidence of diverse feeding habits. □Arthropoda, digestive system, ecology, muscle scars, Proetida, Trilobita.     

Small shelly fossils and trace fossils near the Precambrian-Cambrian boundary in the Yukon Territory, Canada

In the past an ‘explosion’ in diversity and abundance of small shelly fossils and of trace fossils has served to mark the base of the Cambrian. However, no evidence has been presented to prove that the ‘explosions’ of the two groups were synchronous. We describe small shelly fossils and trace fossils from the same phosphatic limestone beds that indicate that the two events were separate in time. The small shelly fossils are Anabarites trisulcatus, Hyolithellus cf. H. isiticus, Microcornus? sp., Protohertzina anabarica, P. unguliformis, P. sp. A, Pseudorthotheca sp. A, Rushtonia? sp. A, four types of tuberculate plates and one type of reticulate plate. These fossils represent a restricted, ‘pre-explosion’ fauna and are assigned to the Anabarites-Circotheca-Protohertzina Assemblage Zone, an uppermost Precambrian zone in the Meishucun Stage, Yunnan Province, China. A point at the top of this zone has received strong international endorsement for future designation as the base of the Cambrian. Associated with the small shelly fossils are the trace fossils Cruziana sp. A, Cruziana? sp. B, Rusophycus sp. A, Palaeophycus rubdark and arthropod scratch marks. If found in isolation, this trace fossil assemblage would be considered as post-Precambrian because it includes large, highly organized arthropod traces that are traditionally accepted as occurring above the trace fossil ‘explosion’. We therefore conclude that the trace fossil ‘explosion’ predates the small shelly fossil ‘explosion’. If the proposed location of the base of the Cambrian in Yunnan is accepted, the small shelly fossil ‘explosion’ concept and its relationship to the boundary would not be greatly modified. The trace fossil ‘explosion’, however, would no longer indicate the base of the Cambrian and the ranges of some trace fossils would be extended into the Precambrian.     

Triassic trace fossils from lacustrine shoreline deposits of the Passaic formation,douglassville, pennsylvania

Lake‐margin deposits of the Late Triassic Passaic Formation, Douglassville, Pennsylvania, have yielded a moderate variety of trace fossils. The greatest diversity and abundance of trace fossils occurs on the sole of a thin gray claystone overlain and underlain by gray siltstones. Specimens of Cochlichnus anguineus, Helminthoidichnites tenuis, Helminthopsis hieroglyphica, Treptichnus pollardi, and paired trails reflect simple, unspecialized, horizontal grazing as well as feeding traces under very shallow water lacustrine conditions. The lack of commonly associated Scoyenia burrows in these deposits may possibly be related to the degree of maturation of the organic debris available. The traces, as well as a lack of meniscate burrows, compare favorably to the Mermia ichnofacies, except Passaic deposits exhibit evidence of subaerial exposure. This unit most likely records a lacustrine expansion whereby grazing trails were emplaced under fully subaqueous conditions. Subsequent shallowing and desiccation, followed by sediment influx during rainstorms, favored preservation of these traces.

In contrast, the Scoyenia ichnofacies consists of feeding burrows of Scoyenia gracilis and Spongeliomorpha milfordensis within reddish brown siltstones and mud‐stones (redbed sequence). The Scoyenia ichnofacies records limited exploitation, by opportunistic infaunal deposit feeders, of lake‐margin nutrients carried in during occasional rainstorms that punctuated otherwise extended periods of aridity.     

A new oryctocephalid trilobite from the Balang Formation (Cambrian Stage 4) of northwestern Hunan,South China,with remarks on the classification of oryctocephalids

A new trilobite, Longaspis paiwuensis n. gen. n. sp., from the Balang Formation (Cambrian Stage 4) in northwestern Hunan, South China, is described. This rare trilobite adds to an expanding taxonomic list of organisms recognized from the Balang Lagerstätte, a deposit of exceptional preservation from the Cambrian. Longaspis paiwuensis is an unusually large-sized, micropygous oryctocephalid trilobite that has proparian facial sutures, pit-like lateral glabellar furrows, up to 17 thoracic segments, and a distinct medial notch in the pygidium; it lacks marginal spines.The classification of the family Oryctocephalidae is reviewed. Three subfamilies are recognized, and Longaspis n. gen. is assigned to the subfamily Oryctocarinae.     

An Early Ordovician Trilobite assemblage from the Lashkarak Formation, Damghan area, northern Iran

A low diversity Lower Ordovician trilobite assemblage is described from the middle part of the Lashkarak Formation at Simeh-Kuh, northwest of Damghan, northern Iran. Co-occurrence with conodonts of the lowermost Paroistodusproteus Biozone suggests an uppermost Tremadocian age. This assemblage includes four taxa, including one new genus and two new species, Damghanampyxginteri nov. gen. nov. sp. and Asaphellusfecundus nov. sp. The third diagnosable species from the formation is Taihungshaniamiqueli (Bergeron, 1894) which has previously been reported from southern France and the Turkish Taurides, suggesting north Gondwanan faunal affinities.     

A Long Mortichnial Trackway of Mesolimulus walchi from the Upper Jurassic Solnhofen Lithographic Limestone near Wintershof,Germany

A 9.7 m long trackway was discovered in a plattenkalk quarry near the village of Wintershof, Bavaria, Germany, in 2002. The huge ichnofossil derives from the Lower Tithonian, Upper Jurassic Solnhofen Lithographic Limestone. The trackway is complete from beginning to end and consists of footprints, telson drag impressions, prosoma imprints and is identified as the ichnotaxon Kouphichnium isp. Preserved at the very end of the trackway is a complete specimen of Mesolimulus walchi confirming the trackway as a mortichnia (death march). Trackways and trace makers preserved together in the fossil record are rare and such specimens allow unique insights into behavior and ecology. The events that led to M. walchi preserved in this sediment are unknown; however, a most likely scenario is that the limulid was washed into the lagoonal environment during a harsh storm.