Determination of a Late Miocene rocky palaeoshore by bioerosion trace fossils from the Bozcaada Island, Çanakkale,Turkey

Bioerosion is a common process in hard substrates. This study introduces an example from the rocky palaeoshore cropping out at a sea cliff on the Bozcaada Island. It includes bioerosion trace fossils preserved in limestone boulders of the shallow marine and lacustrine Alcitepe Formation of Late Miocene age. The ichnotaxa include borings produced by duraphagous drillers (Oichnus isp.), phonorids (cf. Conchotrema isp.), clionid sponges (Entobia cf. goniodes, Entobia geometrica, Entobia laquea, Entobia ovula, E. cf. solaris, Entobia isp.), endolithic bivalves (Gastrochaenolites torpedo, Gastrochaenolites lapidicus, Gastrochaenolites isp., Phrixichnus isp.), polychaete annelids (Maeandropolydora isp., Maeandropolydora sulcans, Maeandropolydora decipiens, Caulostrepsis taeniola, Caulostrepsis isp.), echinoids (cf. Circolites isp.) and spinculid worms (cf. Trypanites isp.). Barnacles are also common as encrusters. The borings can be ascribed to the Gastrochaenolites-Entobia assemblage, which is typical of Neogene rocky-shores. They belong to the Entobia ichnofacies indicating various conditions of light, energy, and depth. Therefore they can reveal environmental changes and play an important role in forming palaeo-rocky shores and wave-cut platforms during marine trangressive events.     

Shell-Filled Burrows in the Upper Oligocene Antigua Formation,Antigua, Lesser Antilles

Limestones of the Upper Oligocene Antigua Formation of Antigua contain unusual burrows filled with the densely packed debris of shelly benthos. Unlined burrows (Planolites?) in deep-water biofacies at Half Moon Bay, parish of Saint Philip, are packed with a monospecific assemblage of large benthic foraminiferans (Lepidocyclina canelli Lemoine &; Douvillé) and a single brachiopod valve, Tichosina sp. A similar burrow in shallower-water biofacies at Hughes Point, parish of Saint Philip, is packed with echinoderm debris and, particularly, test fragments of the spatangoid echinoid Lovenia n. sp. Fragments of the same echinoid fill a conical burrow, Bergaueria isp. The latter is probably a physical accumulation, the common fragments of echinoid being washed into an empty burrow. In contrast, the infill of Planolites? isp. is more likely to be an accumulation mediated by the burrower.     

An Intersection in Time and Space: Significance of Modern Invertebrate Borings in Upper Cretaceous Echinoids

Reworked fossils may contribute unique data to ichnology, stratigraphy, and paleoecology. Reworked Upper Cretaceous echinoids are found on Ocean Isle Beach, North Carolina, United States. Tests of Hardouinia sp. cf. H. mortonis were intensely bored by clionaid sponges (Entobia) and bivalves (Gastrochaenolites), with rare polychaete annelids (Caulostrepsis). Evidence for a high-energy environment in the Late Cretaceous is provided by the sandstone infill and a geopetal infill. Hardouinia were bored on all surfaces, largely lack surface detail and have been corraded, exposing the internal structure of some borings, indicating that these specimens were tumbled in a modern, high energy marine environment. Borers showed substrate preferences: Entobia is largely limited to the test, but do penetrate the sandstone infill in some specimens; Caulostrepsis mainly infested the crystalline calcite of the echinoid test; and Gastrochaenolites penetrated both tests and lithified sandstone infill. This Entobia-Gastrochaenolites assemblage in these echinoids differs from the Entobia-Caulostrepsis assemblage recognized from the approximately coeval, but spatially distant, tests of Upper Cretaceous Echinocorys ex gr. scutata found reworked on the North Sea coast of Norfolk, England. Unlike the Entobia-Gastrochaenolites association of North Carolina, the boring association in Norfolk is between Entobia and Caulostrepsis, which are found in both tests and chalk infill. Thus, the lithology of the infill is an important factor in determining these differences.     

Ichnofacies and microbial build-ups on Late Miocene rocky shores from Menorca (Balearic Islands), Spain

Angular unconformites between Jurassic and Miocene strata are exposed in the sea cliffs of Cala Cigonya on the northwest coast of Menorca in the Balearic Islands of Spain. The geological discontinuities represent rocky shores on opposite sides of a former headland with 15 m of topographic relief. On the east flank, Jurassic dolomite is overlain by Upper Miocene (Tortonian to Messinian) breccia and laminated limestone. Here, a partially exhumed dolomite surface records Miocene bivalve borings of the ichnospecies Gastrochaenolites torpedo and G. lapidicus that achieved a density of >1,000 borings/m². Other associated traces include sponge borings (Entobia isp.) and polychaete borings (Caulostrepsis isp.). A breccia deposit 0.8 m thick was derived from the underlying dolomite and angular clasts still retain evidence of bivalve borings. Above follows a succession of laminated limestone beds more than 5 m thick, including some levels with dome-shaped stromatolites and other horizons with reworked dolomite clasts. Thin-section analysis of the laminated limestone reveals dark and light couplets 0.2 mm thick consistent with microbial origins. In contrast, the west flank was buried by coarse sandstone and laminated sediments. Here, dwelling structures of regular echinoids (Circolites kotoncensis) are the dominant traces preserved on the dolomite surface, reaching a maximum density of 66 borings/m². Associated borings include Entobia geometrica as well as rare traces of Gastrochaenolites isp. and Trypanites isp. Notable for the absence of a basal Miocene breccia, the west flank is interpreted as a sheltered rocky shore coeval with an exposed rocky shore on the east flank. Today, heavy surf on the north coast of Menorca is related to the Tramontana winds that blow out of Spain during winter months. Similar atmospheric circulation patterns must have prevailed during the Late Miocene, but the replacement of ichnofacies by microbial build-ups resulted from increased salinity during the Messinian crisis.     

Site selection and behavior of sponge and bivalve borers in shells of the cretaceous oysters exogyra cancellata and pycnodonte mutabilis from delaware,U.S.A

In shells of the oysters Exogyra cancellata and Pycnodonte mutabilis from the Mount Laurel and Marshalltown Formations (Campanian‐Maestrichtian), three‐quarters of all valves bear sponge borings (Entobia isp.) borings and 30% have borings of a lithophagid bivalve (Gastrochaenolites isp.). Non‐random distributions of these euendoliths, documented in this paper, may in part be accounted for by differential survival of sponge and lithophagid larvae and spat in varying circumstances. In addition, exterior shell architectures and post‐mortem orientations of shells are inferred to have prompted active geophobic (antigravity), rugophilic (groove‐seeking), and rheophilic (current‐seeking) behavior that enhanced survivorship of the settling larvae.     

Devonian Trace Fossils of the Horlick Formation,Ohio Range,Antarctica: Systematic Description and Palaeoenvironmental Interpretation

The clastic Horlick Formation contains an ichnofauna of 28 ichnotaxa dominated by burrowers. These are a mixture of simple vertical forms (Skolithos linearis, S. magnus, Bergaueria cf. langi, Rosselia socialis, Monocraterion isp.), U or arc-like forms (Diplocraterion parallelum, Arenicolites types A and B, Catenarichnus antarcticus, C. isp., aff. Lanicoidichna isp.), and complex, vertical spiral structures (Asterosoma isp., Spirophyton isp.). Horizontal burrows include Ancorichnus cf. capronus, Palaeophycus tubularis, and Psammichnites devonicus isp. nov. Surface traces comprise Haplotichnus isp., Cruziana problematica, C. rhenana, Rusophycus aff. carbonarius, R. isp., Protovirgularia rugosa, Lockeia ornata and cubichnia indet., while trackways include Diplichnites gouldi, D. isp., Maculichna? isp. and large imprints. The Horlick Formation (maximum 56 m) records an early Devonian transgression onto a deeply weathered land area that lay in the direction of Marie Byrd Land, spreading from the South Africa sector of Gondwana. Analysis of the trace fossils confirms their formation in near-shore to intertidal environments, with some ichnotaxa living close to the marine/fluvial boundary (e.g., Spirophyton, aff. Lanicoidichna, Cruziana problematica, Rusophycus aff. carbonarius, Maculichna?). The ichnofauna probably comprised a variety of marine suspension and deposit-feeding worms, shallow burrowing molluscs (bivalves and possibly bellerophontids) and several different types of arthropods, including trilobites.     

A New Ichnospecies of Gastrochaenolites Leymerie from the Pleistocene Port Morant Formation of Southeast Jamaica and the Taphonomy of Calcareous Linings in Clavate Borings

The ichnospecies Gastrochaenolites pickerilli isp. nov. is based on ten borings found in a shell of the gastropod Strombus gigas Linné from the Pleistocene (Sangamonian) Port Morant Formation of southeast Jamaica. These borings bear morphological similarities to Gastrochaenolites torpedo Kelly and Bromley but differ from all other Gastrochaenolites ispp. in having prominent and numerous calcareous meniscate structures arrayed adjacent to one side of the boring. These menisci are concave towards the center of the boring and are the remnants of calcareous tubes that lined earlier boreholes, that the boring bivalve treated as part of the lithified substrate when relocating. They are thus evidence of the former positions of borings that, unusually, were breached as the bivalve migrated sideways. Although this was a common behavior for Gastrochaenolites-producing bivalves within this substrate, the reason for it occurring is uncertain.     

An Updated Review of the Avian Footprint Record from the Yacoraite Formation (Maastrichtian-Danian), Northwestern Argentina

Abstract

The Yacoraite Formation (Maastrichtian–Danian; Balbuena Subgroup; Salta Group), from Northwestern Argentina, represents a shallow epeiric unit which is the result of transgressions in the Andean basin of South America. Herein, we study the avian footprints from the Maimará locality, Jujuy province, and Quebrada del Tapón ichnosite, Salta province. The avian footprints from the Maimará locality is less diverse, made up: cf. Alaripeda isp., Avipeda isp., cf. Gruipeda filiportatis, and cf. Gruipeda isp. The avian track record from the Quebrada del Tapón ichnosite is composed of: cf. Alaripeda isp., Ardeipeda cf. egretta., Gruipeda filiportatis (=Yacoraitichnus avis) and others Gruipeda or compared to this ichnogenus, cf. Uhangrichnus isp., and several indetermined avian footprints. Both ichnological assemblages have tracks assigned to shorebirds or Charadriiformes. The facies distribution of trace fossils reinforces the overall model of a shorebird tracks dominance in moderate to low energy settings. This distribution can be divided into three sub-environments: (1) a moderate to high energy shoreline under wave action, (2) a supratidal body of ephemeral ponds, far away from direct wave influence and (3) a landward position, beyond the ephemeral ponds system. We have included all the ichnoassemblages within the shorebird ichnosubfacies as a subset of the Scoyenia Ichnofacies.     

Taphonomic signatures on modern molluscs and corals from Red Sea coast,southern Saudi Arabia

Bioeroded gastropod, bivalve and coral specimens (n = 570) were collected from the Jazan area, Saudi Red Sea coast, from which 22 ichnospecies of 8 ichnogenera were identified and illustrated. These traces were produced by clionid sponges (Entobia geometrica, E. ovula, E. cf. goniodes, E. cretacea, E. laquea, E. cf. paradoxa and E. isp.), duraphagous drillers (Oichnus ovalis, O. paraboloides, O. simplex and O. isp.), endolithic bivalves (Gastrochaenolites cf. dijugus, G. lapidicus, G. torpedo and G. isp.), polychaete annelids (Caulostrepsis taeniola, C. isp., Maeandropolydora sulcans, M. isp. and ?Trypanites isp.), acorn barnacles (Rogerella isp.), and vermetid gastropods (Renichnus isp.). The seashells act as hard substrate for colonization by serpulid worm, bivalves, bryozoans, and barnacles. Ichnogenus Entobia was most abundant (56.1%), followed by Gastrochaenolites (25.4%), Caulostrepsis (5.3%), Trypanites (4.2%), Maeandropolydora (3.2%), Oichnus (2.8%), Renichnus (1.9%), and Rogerella (1.0%). Oichnus occurred on the thin-shelled and smooth molluscs, while most Gastrochaenolites borings were found in the larger and thicker seashells as a suitable substrate for the settlement of polychaetes, lithophages, naticids, mytilids, and vermetids. Presence of annelid traces among radial ribs and at the siphonal areas of bivalves is indicative of nutrient capturing from water flow during the lifetime of these bivalves, within a shallow, high energy marine environment, where disarticulation, fragmentation, and abrasion of the seashells were abundantly observed.     

Site Selectivity of the Pit Oichnus excavatus Donovan and Jagt Infesting Hemipneustes striatoradiatus (Leske) (Echinoidea) in the Type Maastrichtian (Upper Cretaceous,The Netherlands)

Two tests of the holasteroid echinoid Hemipneustes striatoradiatus (Leske) from the type area of the Maastrichtian Stage (Upper Cretaceous) bear a varied infestation of episkeletozoans (oysters, bryozoan colony, and serpulids), borings (probable Caulostrepsis isp., Oichnus simplex Bromley), surface abrasion (Gnathichnus? isp.), and pits (O. excavatus Donovan and Jagt). Only O. excavatus represents a premortem infestation. In one specimen, the four individual pits of this ichnospecies are each associated with a different ambulacrum and pore pairs that, in life, bore respiratory tube feet; the anterior ambulacrum, of different gross morphology, is not infested. In the second test, three out of four of the same ambulacra are infested, although there are also O. excavatus in the interambulacra. The association between O. excavatus and the ambulacra of the echinoid, and thus its tube feet, is open to several plausible explanations, but most likely provided some form of feeding or protective advantage to the pit-forming organism.     

The Tommotian phase of the Early Cambrian Agronomic Revolution in the carbonate mud environment of central Siberia

The profound ecological change of the marine benthos that eventually led to the almost complete destruction of the Precambrian matgrounds by benthic grazers and bioturbators (the agronomic revolution) was largely completed in the Tommotian. At that time, burrows produced by bottom‐dwelling animals as shelters against predators were supplemented by burrowing for food by predators and sediment feeders. The limy mud ichnofauna of that age in Siberia was very different from the roughly coeval sand bottom faunas of Baltica. Although the exact zoological identity of the animals forming the infaunal Tommotian traces remains unknown, they probably mostly represent various kinds of early nemathelminthes. No apparent locomotion traces of mollusc origin have been encountered in the Early Cambrian, despite the abundant occurrence of skeletal fossils attributed to molluscs. Possibly the standard muscular foot, typical of modern molluscs, had not yet developed. Ichnotaxa represented are Teichichnus isp., Rhizocorallium isp., Chondrites isp., possibly the Buren ichnocomplex and others.     

Revision of Late Permian tetrapod tracks from the Dolomites (Trentino-Alto Adige,Italy)

The Val Gardena Formation of the Dolomites region in northern Italy preserves the most significant assemblage of Late Permian tetrapod footprints in the world. More than 120 years of collecting resulted in about 900 publicly accessible specimens from the study area. This huge amount of data is comprehensively revised in the light of recent advances in the study of Late Palaeozoic – Early Mesozoic tetrapod ichnofossils. According to our analyses, the Val Gardena Sandstone Formation includes tracks that can be assigned to cf. Batrachichnus isp. (temnospondyl amphibian), Capitosauroides isp. (amphibian), Dicynodontipus isp. (cynodont therapsid), Dolomitipes accordii n. igen. n. comb. (dicynodont therapsid), cf. Dromopus isp. (neodiapsid), Pachypes dolomiticus (pareiasaurian parareptile), Paradoxichnium problematicum (archosauromorph neodiapsid), Procolophonichnium tirolensis n. comb. (procolophonoid parareptile), cf. Protochirotherium isp. (archosauriform neodiapsid) and Rhynchosauroides pallinii (neodiapsid). The ichnoassociation is dominated by tracks of neodiapsid and parareptilian tetrapods, whereas synapsid and anamniote tracks are rather minor components. It includes 10 out of 12 tetrapod ichnogenera known from Lopingian deposits and thus it constitutes a reference for the Paradoxichnium biochron. It shows striking similarities with other low-latitude non-aeolian contemporaneous ichnoassociations of Europe and North Africa, differences may be linked to the palaeoenvironment. Moreover, it shows a clear Triassic affinity.

The new ichnogenus Dolomitipes was registered in Zoobank.org. urn:lsid:zoobank.org:act:5B4D871C-D16A-4E93-8211-CEE08019BA60     

Oichnus Bromley Borings in the Irregular Echinoid Hemipneustes Agassiz from the Type Maastrichtian (Upper Cretaceous,The Netherlands and Belgium)

Three ichnospecies of Oichnus Bromley occur in tests of the large holasteroid echinoid Hemipneustes striatoradiatus (Leske) in the type area of the Maastrichtian (Upper Cretaceous) in The Netherlands and Belgium; Oichnus simplex Bromley (penetrative), Oichnus paraboloides Bromley (nonpenetrative and showing two distinct morphologies), and Oichnus excavatus isp. nov. (nonpenetrative). The two distinct morphologies of O. paraboloides (both shallow, one with a central boss) are gregarious, but do not occur together on the same specimens, suggesting they were generated by different taxa. Oichnus paraboloides with a central boss occurs on H. striatoradiatus from the upper Nekum Member, Maastricht Formation (Maastrichtian, Upper Cretaceous). Tests of the host echinoid are smaller in the overlying Meerssen Member, Maastricht Formation, where they are infested by O. excavatus, the largest borings considered herein, which have concave walls and a large central boss. Blisters inside tests from the Meerssen Member show that this infestation occurred when the echinoid was alive. It is postulated that producers of these borings in H. striatoradiatus may have been genetically related and increased in size during the Maastrichtian even as the host echinoids showed a size decrease. This size increase in H. striatoradiatus was genetic and cannot be related to increase in size of borings.     

Avian diversity and behavior in an Eocene coastal plain,Svalbard: the ichnological evidence

Abstract

This study presents an ichnotaxonomical assessment of bird footprints from a coastal plain setting in the Eocene lower to middle Aspelintoppen Formation in Brongniartfjellet and Storvola, Svalbard. These footprints are unique evidence for Paleogene birds from Svalbard and the second evidence of Paleogene avifauna of the Arctic (along with scarce fossil remains from Ellesmere Island). The analyzed footprints are assigned to six ichnotaxa belonging to three ichnofamilies: Aquatilavipes isp., avian footprint morphotype A and B (ichnofamily Avipedidae); Gruipeda cf. G. abeli, Gruipeda cf. G. dominguensis (ichnofamily Gruipedidae); and Gyeongsangornipes isp. (ichnofamily unknown). Associated invertebrate ichnofossils include Helminthoidichnites tenuis, Cochlichnus anguineus, and Helminthopsis isp. The avian footprints reflect small, medium-sized and rare large birds that can be morphologically compared to those of modern relatives including crane, heron, plover, moorhen, gallinule, oystercatcher and curlew. It is also proposed that in situ sets of shorebird footprints showing a preferred orientation, not composing trackways and showing overprinting, can be used as an indicator of the position and orientation of the shoreline.     

Early cretaceous bird-dominated and dinosaur footprint assemblages from the northwestern margin of the Junggar Basin, Xinjiang, China

Here we describe a number of mostly isolated bird and non-avian dinosaur footprints from the Huangyangquan track site in the Lower Cretaceous Lower Layer of the Tugulu Group near Huangyangquan Reservoir in the Wuerhe District, Karamay, Xinjiang Uyghur Autonomous Region, China. Bird footprints at the site pertain to Koreanaornis dodsoni n. ichnosp., Goseongornipes isp., Aquatilavipes isp., and Moguiornipes robusta n. ichnogen. n. ichnosp. Moguiornipes tracks may be the products of a bird with lobed feet. These shorebird-morph tracks are the first solid evidence of birds in the Tugulu Group, and greatly enrich the known faunal diversity of the Lower Layer of the Tugulu Group. The Huangyangquan avian ichnofauna is comparable to those of the Jindong Formation, Korea and the Dakota Formation, USA. Non-avian dinosaur footprints at the site pertain to cf. Jialingpus isp., Asianopodus isp., and Kayentapus isp. This is the first report of Jialingpus from Lower Cretaceous strata. The discoveries of Asianopodus isp. and Kayentapus isp. increase the known ranges of these two ichnogenera.     

Evidence of Bioerosive Structures in Quaternary Glaciomarine Sediments from Southwestern Iceland

The Late Weichselian marine and glaciomarine sediments occurring in many places along the coast of Iceland are rich in invertebrate fossils, especially mollusks and barnacles. A diverse ichnofauna, constituted especially by bioerosional traces documenting the activity of predators and animals that use the host shell for attachment or the construction of dwellings, was identified at the localities of Ósmelur, Saurbær, and Brekkubakkar in southwestern Iceland. The ichnotaxa identified include Anellusichnus circularis (Santos, Mayoral, and Muñiz), Caulostrepsis isp., Centrichnus concentricus (Bromley and Martinell), Clionolithes isp., Finichnus peristroma (Taylor, Wilson, and Bromley), Finichnus isp., Sedilichnus asperus (Nielsen and Nielsen), Sedilichnus cf. excavatus (Donovan and Jagt), Sedilichnus gradatus (Nielsen and Nielsen), Sedilichnus smiley isp. nov., Sedilichnus ovalis (Bromley), Sedilichnus paraboloides (Bromley), Sedilichnus simplex (Bromley), and Sedilichnus spongiophilus (Müller).     

Bioerosive structures from Miocene marine mobile‐substrate communities in southern Spain,and description of a new sponge boring

Abstract: Neogene palaeoshore sediments are abundantly represented along the Mediterranean coast of Iberia. An outcrop north of the Sierra Tejeda, named La Resinera, exposes concentrations of pebbles and boulders of marble, comprising an upper Miocene marine beach deposit. The high diversity of bioerosion trace fossils present in these boulders includes structures produced by polychaete annelids, demosponges, echinoids and endolithic bivalves, which indicate a shallow shoreface environment. The ichnotaxa represented are Maeandropolydora sulcans, Caulostrepsis taeniola, Entobia geometrica, Entobia ovula, Circolites kotoncensis, Gastrochaenolites torpedo, Gastrochaenolites lapidicus, Gastrochaenolites ornatus and Gastrochaenolites turbinatus. The borings are Tortonian (late Miocene) in age. Also present, and particularly abundant, are large sponge borings that have a single chamber from which radiating canals emerge. This trace fossil is designated as Entobia resinensis isp. nov.     

Ichnosystematics of the Lower Permian Invertebrate Traces from the Collio and Mt. Luco Basins (North Italy)

The Lower Permian ichnofauna in the Collio Formation (Artinskian) in the Val Trompia (Brescian Prealps, North Italy) has been studied for a long time, but the studies have focused mainly on vertebrate prints. In this study, the invertebrate ichnofauna of the Collio Formation, and in the epiclastites of the Monte Luco Formation (Artinskian) cropping out in the Monte Luco area (Trentino Alto Adige region), is systematically analyzed for the first time. This ichnocoenosis consists of: Permichnium isp., Paleohelcura tridactyla, Diplichnites gouldi (Types A and B), Diplopodichnus biformis, Circulichnis montanus, Helminthopsis hieroglyphica, Gordia marina, Acripes cf. multiformis, Cruziana cf. problematica, Cochlichnus anguineus, Palaeophycus tubularis, Planolites isp. and ?Scoyenia isp. The ichnoassociation from the Collio Formation belongs to the Scoyenia ichnofacies, while that from the Mt. Luco Formation belongs to the Mermia ichnofacies. The latter, because of the lack of complete data, can be linked only to one of several submersion phases of the intravolcanic basin and is not referred to the complete continental Permian sequence in this zone. The composition of the ichnoassociation here analysed is similar to those of other European (especially France and Germany) and extra-European areas (especially North America and Argentina).     

The earliest fossil evidence of bone boring by terrestrial invertebrates,examples from China and South Africa

We report the oldest fossil evidence of osteophagia by terrestrial invertebrates on both the Asian and African continents. Bones attributable to the Middle Jurassic dinosaur Chuanjiesaurus (Dinosauria: Sauropoda) were found with post-mortem insect modification in the Chuanjie Formation, Yunnan Province, China. The morphology of the borings closely matches the ichnogenus Cubiculum. Based on the lack of bioglyphs observed in Cubiculum ornatus, a new ichnospecies is proposed here. The new trace fossil, Cubiculum inornatus isp. nov., is interpreted to have been constructed for pupation by an unknown taxon of insect. Additionally, we report even older borings from Early Jurassic dinosaur bones of the Elliott Formation in the Karoo Basin, which represent the second oldest occurrence of insect traces in bone from continental settings. Both trace fossils sites have palaeogeographic implications for the origins and dispersal of osteophagia amongst terrestrial invertebrates during the Mesozoic. These discoveries push back the antiquity of pupation in animal bones by more than 100 million years to the Middle Jurassic, indicating that this behaviour, and osteophagy more generally, originated early in the Mesozoic, roughly comparable with the origination of insect pupation in woody substrates (Late Triassic).     

Scolicia shirahamensis isp. nov.: a triple-corded scolicia and its ichnological implications

Abstract

Peculiar meniscate burrows with three sediment cords occur in early to middle Miocene tidal-flat deposits of southwestern Japan. Two of the cords are situated at the bottom and the other is at its center. Detailed observations of the burrow structures and comparative neoichnological studies of modern spatangoid burrows in a tidal flat revealed that the former two were true drainage tubes and the latter was fecal in origin. The trace fossil was thus assigned to the ichnogenus Scolicia. Based on these findings, a new ichnospecies Scolicia shirahamensis isp. nov. has been described here. The central sediment cord is seemingly identical to the drainage tube of the ichnogenus Bichordites, another ichnogenus that has been commonly ascribed to a fossil spatangoid burrow, similar to Scolicia. Careless ichnogeneric identification of a spatangoid burrow, based only on the central sediment cord, therefore, may produce an incorrect identification.