Problematic Fossil Research Articles

MIA-Clustering: a novel method for segmentation of paleontological material.

Paleontological research increasingly uses high-resolution micro-computed tomography (μCT) to study the inner architecture of modern and fossil bone material to answer important questions regarding vertebrate evolution. This non-destructive method allows for the measurement of otherwise inaccessible morphology. Digital measurement is predicated on the accurate segmentation of modern or fossilized bone from other structures imaged in μCT scans, as errors in segmentation can result in inaccurate calculations of structural parameters. Several approaches to image segmentation have been proposed with varying degrees of automation, ranging from completely manual segmentation, to the selection of input parameters required for computational algorithms. Many of these segmentation algorithms provide speed and reproducibility at the cost of flexibility that manual segmentation provides. In particular, the segmentation of modern and fossil bone in the presence of materials such as desiccated soft tissue, soil matrix or precipitated crystalline material can be difficult. Here we present a free open-source segmentation algorithm application capable of segmenting modern and fossil bone, which also reduces subjective user decisions to a minimum. We compare the effectiveness of this algorithm with another leading method by using both to measure the parameters of a known dimension reference object, as well as to segment an example problematic fossil scan. The results demonstrate that the medical image analysis-clustering method produces accurate segmentations and offers more flexibility than those of equivalent precision. Its free availability, flexibility to deal with non-bone inclusions and limited need for user input give it broad applicability in anthropological, anatomical, and paleontological contexts.

On the Eocene mangroves of Wadi Al-Hitan World Heritage site, Fayum, Egypt

Wadi Al-Hitan is the first site in Egypt to be inscribed by UNESCO on the “Natural World Heritage List”. Wadi Al-Hitan mangrove plant bed lies in late middle Eocene (Bartonian) at the top of Birket Qarun Formation, underlying Qasr El-Sagha Formation (Priabonian). Plant fossils include casts of roots and rhizomes, an impression of a leaf and petrified drift woods. Problematic fossils include directly–preserved hard parts of Echinodermata and casts of closely-spaced, mineral-filled siphons of bivalves. All fossils are described, illustrated and discussed in detail.

A cosmopolitan late Ediacaran biotic assemblage: new fossils from Nevada and Namibia support a global biostratigraphic link

Owing to the lack of temporally well-constrained Ediacaran fossil localities containing overlapping biotic assemblages, it has remained uncertain if the latest Ediacaran (ca 550-541 Ma) assemblages reflect systematic biological turnover or environmental, taphonomic or biogeographic biases. Here, we report new latest Ediacaran fossil discoveries from the lower member of the Wood Canyon Formation in Nye County, Nevada, including the first figured reports of erniettomorphs, Gaojiashania, Conotubus and other problematic fossils. The fossils are spectacularly preserved in three taphonomic windows and occur in greater than 11 stratigraphic horizons, all of which are below the first appearance of Treptichnus pedum and the nadir of a large negative δ13C excursion that is a chemostratigraphic marker of the Ediacaran-Cambrian boundary. The co-occurrence of morphologically diverse tubular fossils and erniettomorphs in Nevada provides a biostratigraphic link among latest Ediacaran fossil localities globally. Integrated with a new report of Gaojiashania from Namibia, previous fossil reports and existing age constraints, these finds demonstrate a distinctive late Ediacaran fossil assemblage comprising at least two groups of macroscopic organisms with dissimilar body plans that ecologically and temporally overlapped for at least 6 Myr at the close of the Ediacaran Period. This cosmopolitan biotic assemblage disappeared from the fossil record at the end of the Ediacaran Period, prior to the Cambrian radiation.

Ancestral morphology of crown-group molluscs revealed by a new Ordovician stem aculiferan.

Exceptionally preserved fossils provide crucial insights into extinct body plans and organismal evolution. Molluscs, one of the most disparate animal phyla, radiated rapidly during the early Cambrian period (approximately 535-520 million years ago (Ma)). The problematic fossil taxa Halkieria and Orthrozanclus (grouped in Sachitida) have been assigned variously to stem-group annelids, brachiopods, stem-group molluscs or stem-group aculiferans (Polyplacophora and Aplacophora), but their affinities have remained controversial owing to a lack of preserved diagnostic characters. Here we describe a new early sachitid, Calvapilosa kroegeri gen. et sp. nov. from the Fezouata biota of Morocco (Early Ordovician epoch, around 478 Ma). The new taxon is characterized by the presence of a single large anterior shell plate and polystichous radula bearing a median tooth and several lateral and uncinal teeth in more than 125 rows. Its flattened body is covered by hollow spinose sclerites, and a smooth, ventral girdle flanks an extensive mantle cavity. Phylogenetic analyses resolve C. kroegeri as a stem-group aculiferan together with other single-plated forms such as Maikhanella (Siphogonuchites) and Orthrozanclus; Halkieria is recovered closer to the aculiferan crown. These genera document the stepwise evolution of the aculiferan body plan from forms with a single, almost conchiferan-like shell through two-plated taxa such as Halkieria, to the eight-plated crown-group aculiferans. C. kroegeri therefore provides key evidence concerning the long debate about the crown molluscan affinities of sachitids. This new discovery strongly suggests that the possession of only a single calcareous shell plate and the presence of unmineralised sclerites are plesiomorphic (an ancestral trait) for the molluscan crown.

The origin of tetraradial symmetry in cnidarians

Serially arranged sets of eight septa-like structures occur in the basal part of phosphatic tubes of Sphenothallus from the early Ordovician (early Floian) Fenxiang Formation in Hubei Province of China. They are similar in shape, location and number, to cusps in chitinous tubes of extant coronate scyphozoan polyps, which supports the widely accepted cnidarian affinity of this problematic fossil. However, unlike the recent Medusozoa, the tubes of Sphenothallus are flattened at later stages of development, showing biradial symmetry. Moreover, the septa (cusps) in Sphenothallus are obliquely arranged, which introduces a bilateral component to the tube symmetry. This makes Sphenothallus similar to the Early Cambrian Paiutitubulites, having similar septa but with even more apparent bilateral disposition. Biradial symmetry also characterizes the Early Cambrian tubular fossil Hexaconularia, showing a similarity to the conulariids. However, instead of being strictly tetraradial like conulariids, Hexaconularia shows hexaradial symmetry superimposed on the biradial one. A conulariid with a smooth test showing signs of the ‘origami’ plicated closure of the aperture found in the Fenxiang Formation supports the idea that tetraradial symmetry of conulariids resulted from geometrical constrains connected with this kind of closure. Its minute basal attachment surface makes it likely that the holdfasts characterizing Sphenothallus and advanced conulariids are secondary features. This concurs with the lack of any such holdfast in the earliest Cambrian Torellella, as well as in the possibly related Olivooides and Quadrapyrgites. Bilaterally arranged internal structures in polyps representing probably the oldest medusozoans support the suggestions based on developmental evidence that the ancestor of cnidarians also was a bilaterally symmetrical animal. This is one more example of fossil data that strictly fit the molecular phylogenetic evidence but not necessarily morphology-based zoological interpretations.

Environmental Human Rights in the Trump Era: Modes of Resistance and Reform

The ecological ramifications of the Trump administration may well prove catastrophic. Climate change denial and problematic fossil fuel positions featured prominently in the President’s campaign; post-election, far-right nominations and policy stances have seemingly confirmed the administration’s dire trajectory. Thus, environmental human rights—i.e., normative guarantees inter alia to clean water and air—are imperiled in the U.S., perhaps especially in subordinated regions like Appalachia. Critically informed local activism approaches, however, will likely constitute the most effective eco-reform modes under the Trump regime.

Prasinophyte green algae Tasmanites and problematic fossils in the Upper Vendian Biota of the Zavkhan Basin, western Mongolia

A new species of spheromorphic microfossils of Tasmanites with a characteristically thick cover is established in the Zavkhan association of algae, microfossils, and problematic Upper Vendian organisms from the upper part of the siliciclastic–carbonate section of the Tsagaanolom Formation (632 ± 14 Ma) of the Zavkhan Basin in western Mongolia. Representatives of this genus are widespread in the Phanerozoic beds and their accumulations are recorded in the Domanik facies and near hydrocarbon deposits.

Enalikter is not an annelid: homology, autapomorphies and the interpretation of problematic fossils

A megacheiran arthropod, Enalikter aphson, was recently described by Siveter et al. (2014) from the mid-Silurian (late Wenlock) of Herefordshire. Previously, megacheirans had only been recognized from the Cambrian. Struck et al. (2015) considered the body plan of Enalikter to be incompatible with this affinity, arguing that many of the arthropod features were either not present or misinterpreted. Instead, they compared Enalikter to polychaete annelids, identifying characters from numerous polychaete lineages which they considered to be present in Enalikter. A reply to this critique by Siveter et al. (2015) reaffirmed arthropod affinities for Enalikter by presenting additional evidence for key arthropod features, such as arthropodized appendages. Here, we augment Siveter et al. by critically addressing the putative annelid characters of Enalikter presented by Struck et al. and additionally explore the morphological and phylogenetic implications of their hypothesis. We conclude that similarities between Enalikter and polychaetes are superficial and that character combinations proposed by Struck et al. are not present in any annelid, living or extinct. This taxon highlights the importance of using a phylogenetic framework for interpreting fossils that present unusual morphologies, such that proposed shared characters are hypotheses of homology rather than merely phenotypic similarities. Crucially, we argue that autapomorphic characters of subgroups of large taxa (like families or classes within phyla) should not be used to diagnose problematic fossils.

Ediacaran fossils in thin-section

Retallack, G.J., June 2016. Ediacaran fossils in thin-section. Alcheringa 40, xx–xx. ISSN 0311-5518Megafossils from the Ediacaran Period (635–541 Ma) have been controversial in part because many are mere impressions in coarse-grained rocks. New examination of these fossils in petrographic thin-sections reveals various features that inform understanding of the biological affinities of these problematic fossils. Material examined includes Dickinsonia costata from the Ediacara Member of the Rawnsley Quartzite in South Australia, Ernietta plateauensis from the Kliphoek Member of Namibia, Ivesheadia lobata from the Drook Formation of Newfoundland, Charnia antecedens and Charniodiscus spinosus from the Mistaken Point Formation of Newfoundland, Aspidella terranovica from the Fermeuse Formation of Newfoundland, and Nemiana simplex from the Mogilev Formation of Ukraine and the Verkovka Formation of Russia. Three characteristics stand out for all but Nemiana. First, these fossils were remarkably resistant to burial compaction, as originally inferred from depth gauge measurements of overlying moulds, and here confirmed by thin-sections perpendicular to bedding planes. Second, thin-sections reveal a construction of micrometric branching elongate structures forming millimetric hollow elongate structures in fractal arrangements. Third, some of the fossils are asymmetric bifacial or unifacial, with a thick finished upper wall but lower wall thin or non-existent and attached to elongate structures downward into sediment. Compaction-resistant fossils with asymmetric histological layering are most like crustose and fruticose lichens fortified with chitin. In contrast, non-resistant impressions in the tops of beds filled by overlying cross-bedded sediment, as in Nemiana, preserve no informative histology and are similar to lake balls and microbial colonies.Gregory J. Retallack [gregr@uoregon.edu], Department of Geological Sciences, University of Oregon, Eugene, OR 97403-1272, USA.

Reducing taxonomic noise in problematic fossils: revision of the incertae sedis genus Allonema based on shape analysis

Reducing taxonomic noise in problematic fossils: revision of the incertae sedis genus Allonema based on shape analysis

The 'Tully monster' is a vertebrate.

Problematic fossils, extinct taxa of enigmatic morphology that cannot be assigned to a known major group, were once a major issue in palaeontology. A long-favoured solution to the 'problem of the problematica', particularly the 'weird wonders' of the Cambrian Burgess Shale, was to consider them representatives of extinct phyla. A combination of new evidence and modern approaches to phylogenetic analysis has now resolved the affinities of most of these forms. Perhaps the most notable exception is Tullimonstrum gregarium, popularly known as the Tully monster, a large soft-bodied organism from the late Carboniferous Mazon Creek biota (approximately 309-307 million years ago) of Illinois, USA, which was designated the official state fossil of Illinois in 1989. Its phylogenetic position has remained uncertain and it has been compared with nemerteans, polychaetes, gastropods, conodonts, and the stem arthropod Opabinia. Here we review the morphology of Tullimonstrum based on an analysis of more than 1,200 specimens. We find that the anterior proboscis ends in a buccal apparatus containing teeth, the eyes project laterally on a long rigid bar, and the elongate segmented body bears a caudal fin with dorsal and ventral lobes. We describe new evidence for a notochord, cartilaginous arcualia, gill pouches, articulations within the proboscis, and multiple tooth rows adjacent to the mouth. This combination of characters, supported by phylogenetic analysis, identifies Tullimonstrum as a vertebrate, and places it on the stem lineage to lampreys (Petromyzontida). In addition to increasing the known morphological disparity of extinct lampreys, a chordate affinity for T. gregarium resolves the nature of a soft-bodied fossil which has been debated for more than 50 years.

Problematic scale-like fossils from the Ordovician of Siberia with possible affinities to vertebrates

Problematic scale-like fossils from the Ordovician of Siberia with possible affinities to vertebrates

Ancestral state reconstruction of ontogeny supports a bilaterian affinity for Dickinsonia.

Despite numerous attempts, classification of the Precambrian fossil Dickinsonia has eluded scientific consensus. This is largely because Dickinsonia and its relatives are structurally simple, lacking morphological synapomorphies to clarify their relationship to modern taxa. However, there is increasing precedence for using ontogeny to constrain enigmatic fossils, and growth of the type species Dickinsonia costata is well understood. This study formalizes the connection between ontogeny in Dickinsonia-which grows by the addition of metameric units onto one end of its primary axis-with terminal addition, defined as growth and patterning from a posterior, subtermial growth zone. We employ ancestral state reconstruction and stochastic character mapping to conclude that terminal addition is a synapomorphy of bilaterian animals. Thus, terminal addition allies Dickinsonia with the bilaterians, providing evidence that large stem- or crown-group bilaterians made up a significant proportion of the Precambrian biota. This study also illustrates the potential for combining developmental and phylogenetic data in constraining the placement of ancient problematic fossil taxa on the evolutionary tree.

New occurrence of Cambroclavus absonus from the lowermost Cambrian of North China and its stratigraphical importance

Li, L.-Y., Zhang, X.-L., Yun, H. & Li, G.-X., October 2015. New occurrence of Cambroclavus absonus from the lowermost Cambrian of North China and its stratigraphical importance. Alcheringa 40, xxx–xxx. ISSN 0311-5518.The problematic Small Shelly Fossil Cambroclavus absonus is described from the Xinji Formation in the Longxian area, which is located near the southwestern margin of the North China Platform. The Xinji Formation, the basal rock unit of the Cambrian in the studied area, yields an assemblage of skeletal fossils that share many common elements with contemporary faunas from South Australia. Sclerites of C. absonus reported herein represent the first occurrence of the species outside Australia, thus extending the palaeogeographic range of the taxon to northern China. To date, palaeogeographic occurrences of Cambroclavus sclerites are restricted to the Peri-Gondwana realm, including South China, Australia, Tarim, Kazakhstan, North China and Western Europe. These occurrences are divided into a Southern Group realm and Northern Group realm. Stratigraphically, Cambroclavus occurs mostly in Cambrian Stage 3 and has three occurrences in Stage 5, separated by Stage 4 in which Cambroclavus has not yet been found. The first appearance datum of Cambroclavus in Cambrian Stage 3 is of importance for regional and inter-regional correlations. In particular, the presence of Cambroclavus absonus in North China allows species-level correlation between North China and South Australia.Luoyang Li [lly@stumail.nwu.edu.cn], Xingliang Zhang [xzhang69@nwu.edu.cn], Hao Yun [yunhao@stumail.nwu.edu.cn], Early Life Institute and State Key Laboratory Of Continental Dynamics, Department of Geology, Northwest University, Xian 710069, PR China; Guoxiang Li [gxli@nigpas.ac.cn], Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, PR China.

Reassessment of the Silurian problematicum Rutgersella as another post-Ediacaran vendobiont

Retallack, G.J., 1.7.2015. Reassessment of the Silurian problematicum Rutgersella as another post-Ediacaran vendobiont. Alcheringa 39, 573–588. ISSN 0311-5518Rutgersella is a problematic fossil from the early Silurian (Llandovery) Shawangunk Formation of New Jersey, at first interpreted as a jellyfish comparable with Ediacaran fossils, such as Dickinsonia. Three proposed species of Rutgersella from the same locality are here regarded as growth or reproductive variants of a single species, R. truexi. Sedimentary structures, associated trace fossils and petrographic examination now show that they were sessile organisms of intertidal mudflats. These fossils have been dismissed as pyrite suns, but thin-sections show that they were weakly pyritized, organic structures, with a quilted hollow internal structure, similar to Seilacher’s constructional and taxonomic concept of Vendobionta. As for Cambrian Swartpuntia, and Devonian Protonympha, Rutgersella may be a post-Ediacaran vendobiont. The biological affinities of Rutgersella are problematic, but are compared with coenocytic green algae, cellular slime moulds, puffball-like fungal fruiting bodies and foliose lichens.Gregory J. Retallack [gregr@uoregon.edu], Department of Geological Sciences, University of Oregon, Eugene, OR 97403-1272, USA.

The characters of Palaeozoic jawed vertebrates.

Newly discovered fossils from the Silurian and Devonian periods are beginning to challenge embedded perceptions about the origin and early diversification of jawed vertebrates (gnathostomes). Nevertheless, an explicit cladistic framework for the relationships of these fossils relative to the principal crown lineages of the jawed vertebrates (osteichthyans: bony fishes and tetrapods; chondrichthyans: sharks, batoids, and chimaeras) remains elusive. We critically review the systematics and character distributions of early gnathostomes and provide a clearly stated hierarchy of synapomorphies covering the jaw-bearing stem gnathostomes and osteichthyan and chondrichthyan stem groups. We show that character lists, designed to support the monophyly of putative groups, tend to overstate their strength and lack cladistic corroboration. By contrast, synapomorphic hierarchies are more open to refutation and must explicitly confront conflicting evidence. Our proposed synapomorphy scheme is used to evaluate the status of the problematic fossil groups Acanthodii and Placodermi, and suggest profitable avenues for future research. We interpret placoderms as a paraphyletic array of stem-group gnathostomes, and suggest what we regard as two equally plausible placements of acanthodians: exclusively on the chondrichthyan stem, or distributed on both the chondrichthyan and osteichthyan stems.

Affirming life aquatic for the Ediacara biota in China and Australia: COMMENT

[Xiao et al. (2013)][1] argue that Ediacaran fossils were not in paleosols because some Australian beds contain the problematic fossil Eoandromeda also known from Chinese beds they consider marine. They offer no alternative explanations. My preferred alternative is that Eoandromeda was a terrestrial

Cambrian Hyolitha and problematica from West Laurentian North America: taxonomy and palaeobiogeography

Fifteen species of hyoliths and problematic fossils from the present-day western margin of the Laurentian palaeocontinent (Cordilleran North America) are described and/or reassigned. Early Cambrian strata of this region are home to the orthothecid hyolith Guduguwan buelna (Lochman) and the hyolithids Nevadotheca whitei (Resser), Grantitheca? montis (Howell) and Hyolithes sp. B. Diversity of hyoliths increases in the middle Cambrian, featuring an un-named species of the orthothecid Decoritheca Sysoev, three un-named hyolithid species possibly representing Hyolithes Eichwald and one individual referred to as Hyolith sp. that bears resemblance to the Siberian Linevitus fossularis Val’kov. Haydenoconus prolixus (Resser) is documented from southeastern Idaho, and Doescherina clarki Malinky occurs in west-central Montana as pavements of conchs and opercula on bedding surfaces, with such large numbers of specimens affording an opportunity to further assess the range of morphologic variability within a single hyolith species. The upper Cambrian contains the hyolithids Haydenoconus gallatinesis (Resser), one un-named species each of Crestjahitus Sysoev and possibly Hyolithes Eichwald. An un-named species of the orthothecid Contitheca Sysoev occurs within this interval, as do the unusual problematic forms of uncertain affinity, Attenuella attenuata (Walcott 1890) and Kygmaeoceras corrugatus (Walcott 1890). The occurrence of Guduguwan recorded herein suggests a faunal connection between North America and Australia, and Contitheca, Decoritheca and the possible Hyolithes with Baltica and central Europe. Crestjahitus, Hyolith sp. and Kygmaeoceras demonstrate faunal affinity with Siberia. Whereas Doescherina and Grantitheca are endemic to North America, the families they represent also occur in Siberia. Attenuella is currently known from North America only at this time. The stratigraphic range of Contitheca is extended from middle to upper Cambrian; Crestjahitus from lower to upper Cambrian, and if the species of Hyolithes are authentic representatives of that genus, the range of the genus now definitively extends into the lower Cambrian.

Sphenothallus (Cnidaria?) in the Late Ordovician of Baltica, its mineral composition and microstructure

Sphenothallus is a problematic fossil with possible cnidarian affinities. Two species of Sphenothallus, S. aff. longissimus and S. kukersianus, occur in the normal marine sediments of the Late Ordovician of Estonia. S. longissimus is more common than S. kukersianus and has a range from early Sandbian to middle Katian. Sphenothallus had a wide paleobiogeographic distribution in the Late Ordovician. The tubes of Sphenothallus are composed of lamellae with a homogeneous microstructure. The homogeneous microstructure could represent a diagenetic fabric, based on the similarity to diagenetic structures in Torellella (Cnidaria?, Hyolithelminthes). Tubes of Sphenothallus have an apatitic composition, but one tube contains lamellae of diagenetic calcite within the apatitic structure. Sphenothallus presumably had originally biomineralized apatitic tubes. Different lattice parameters of the apatite indicate that biomineralization systems of phosphatic cnidarians Sphenothallus and Conularia sp. may have been different.

New material from the Ordovician of China indicates that Inocaulis is a graptolite

Muir, L.A., Zhang, Y.-D. & Lin, J.-P. 2012. New material from the Ordovician of China indicates that Inocaulis is a graptolite. Alcheringa 37, 558–559. ISSN 0311-5518.The problematic Early Palaeozoic fossil Inocaulis has been regarded as an alga, a graptolite and a hydroid by different authors. A new specimen from the Ordovician (late Darriwilian) of Guizhou Province (China) shows fusellar banding, confirming that it is a benthic graptolite.Lucy A Muir [lucy@asoldasthehills.org], Yuan-dong Zhang [ydzhang@nigpas.ac.cn], Jih-Pai Lin [jplin@nigpas.ac.cn] (corresponding author), State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, No. 39 East Beijing Road, Nanjing 210008, PR China. Received 13.12.2012; revised 10.5.2013; accepted 13.5.2013.