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opencc-zeroDec 2016View details →

Data from: A new crustacean from the Herefordshire (Silurian) Lagerstätte, UK, and its significance in malacostracan evolution

Cascolus ravitis gen. et sp. nov. is a three-dimensionally preserved fossil crustacean with soft parts from the Herefordshire (Silurian) Lagerstätte, UK. It is characterized by a head with a head shield and five limb pairs, and a thorax (pereon) with nine appendage-bearing segments followed by an apodous abdomen (pleon). All the appendages except the first are biramous and have a gnathobase. The post-mandibular appendages are similar one to another, and bear petal-shaped epipods that probably functioned as a part of the respiratory–circulatory system. Cladistic analysis resolves the new taxon as a stem-group leptostracan (Malacostraca). This well-preserved arthropod provides novel insights into the evolution of appendage morphology, tagmosis and the possible respiratory–circulatory physiology of a basal malacostracan.

opencc-zeroDec 2018View details →

Data from: Kalana Lagerstatte crinoids: early Silurian (Llandovery) of central Estonia

The Kalana Lagerstätte of early Aeronian (Llandovery, Silurian) age in central Estonia preserves a diverse shallow marine biota dominated by non-calcified algae. This soft-tissue flora and decalcified and calcified crinoids are preserved in situ, in a lens of microlaminated, dolomitized micrite interbedded in a sequence of dolomitized packstones and wackestones. Although the Lagerstätte is dominated by non-calcified algae, crinoids (together with brachiopods and gastropods) are among the most common organisms that were originally comprised of a carbonate skeleton. Two new crinoids are described from this unit, Kalanacrinus mastikae (large camerate) and Tartucrinus kalanaensis (small disparid). Interestingly, these two crinoids display contrasting preservation with the more common large camerate preserved primarily as a decalcified organic residue, whereas the smaller disparid is preserved primarily in calcite. Preservation was assessed using elemental mapping of C, Ca, S, and Si. Columns have the highest portion of Ca, once living soft tissue is indicated by C, S was dispersed as pyrite or associated with organics, and Si is probably associated with clay minerals in the matrix. This new fauna increases our understanding of the crinoid radiation on Baltica following Late Ordovician extinctions.

opencc-zeroDec 2015View details →

Data from: Axial growth gradients across the postprotaspid ontogeny of the Silurian trilobite Aulacopleura koninckii

Recent morphometric analysis revealed a juvenile (meraspid) axial growth gradient in the trunk of the ~429 Myr old trilobite Aulacopleura koninckii that resulted from growth control based on positional specification, as is common among extant organisms. Here we explore axial growth gradients in the more anterior body region, the cephalon, and in the cephalon and trunk during subsequent development in the holaspid period. We detected an axial growth gradient in the cephalon in the meraspid period, flatter and opposite in direction to that of the trunk, which also persisted during the holaspid period. We also found an holaspid trunk growth gradient, with a different distribution of growth rates among segments than that of the meraspid period. These newly observed growth gradients are compatible with the mechanism of growth control inferred for the meraspid trunk. Thus, the same kind of growth control may have operated in both body regions and during the whole ontogeny of A. koninckii. This study, along with others on the same species that preceded it, show that morphometric analysis of appropriate data sets can address questions of high interest for evolutionary developmental biology using data from fossils. By revealing developmental features at deep nodes of the phylogenetic tree, these studies will elucidate both how developmental processes evolved and how they themselves affected the evolution of organismal body patterning.

opencc-zeroDec 2017View details →

Data from: A three-dimensionally preserved lobopodian from the Herefordshire (Silurian) Lagerstätte, UK

The Herefordshire (Silurian) Lagerstätte (c. 430 MYr BP) has yielded, amongst many exceptionally preserved invertebrates, a wide range of new genera belonging to crown-group Panarthropoda. Here we increase this panarthropod diversity with the lobopodian Thanahita distos, a new total-group panarthropod genus and species. This new lobopodian preserves at least nine paired, long, slender appendages, the anterior two in the head region and the posterior seven representing trunk lobopods. The body ends in a short post-appendicular extension. Some of the trunk lobopods bear two claws, others a single claw. The body is covered by paired, tuft-like papillae. T. distos joins only seven other known three-dimensionally preserved lobopodian or onychophoran (velvet worm) fossil specimens and is the first lobopodian to be formally described from the Silurian. Phylogenetic analysis recovered it, together with all described Hallucigenia species, in a sister-clade to crown-group panarthropods. Its placement in a redefined Hallucigeniidae, an iconic Cambrian clade, indicates the survival of this clade to Silurian times.

opencc-zeroJan 2020View details →

Early Silurian chondrichthyans from the Tarim Basin (Xinjiang, China)

The Sinacanthida ordo nov. and Mongolepidida are spine- and scale-based taxa whose remains encompass some of the earliest reported fossils of chondrichthyan fish. Investigation of fragmentary material from the Early Silurian Tataertag and Ymogantau Formations of the Tarim Basin (Xinjiang Uygur Autonomous Region, China) has revealed a diverse mongolepidid and sinacanthid fauna dominated by mongolepids and sinacanthids in association with abundant dermoskeletal elements of the endemic 'armoured' agnathans known as galeaspids. Micro-computed tomography, scanning electron microscopy and histological sections were used to identify seven mongolepid genera (including Tielikewatielepis sinensis gen. et sp. nov., Xiaohaizilepis liui gen. et sp. nov. and Taklamakanolepis asiaticus gen. et sp. nov.) together with a new chondrichthyan (Yuanolepis bachunensis gen. et sp. nov.) with scale crowns consisting of a mongolepid-type atubular dentine (lamellin). Unlike the more elaborate crown architecture of mongolepids, Yuanolepis gen. nov. exhibits a single row of crown elements consistent with the condition reported in stem chondrichthyans from the Lower Devonian (e.g. in Seretolepis, Parexus). The results corroborate previous work by recognising lamellin as the main component of sinacanthid spines and point to corresponding developmental patterns shared across the dermal skeleton of taxa with lamellin and more derived chondrichthyans (e.g. Doliodus, Kathemacanthus, Seretolepis and Parexus). The Tarim mongolepid fauna is inclusive of coeval taxa from the South China Block and accounts for over two-thirds of the species currently attributed to Mongolepidida. This demonstrates considerable overlap between the Tarim and South China components of the Lower Silurian Zhangjiajie Vertebrate Fauna.

opencc-zeroDec 2016View details →

Data from: An edrioasteroid from the Silurian Herefordshire Lagerstätte of England reveals the nature of the water vascular system in an extinct echinoderm

Echinoderms are unique in having a water vascular system with tube feet, which perform a variety of functions in living forms. Here, we report the first example of preserved tube feet in an extinct group of echinoderms. The material, from the Silurian Herefordshire Lagerstätte, UK, is assigned to a new genus and species of rhenopyrgid edrioasteroid, Heropyrgus disterminus. The tube feet attach to the inner surface of compound interradial plates and form two sets, an upper and a lower, an arrangement never reported previously in an extant or extinct echinoderm. Cover plates are absent and floor plates are separated creating a large permanent entrance to the interior of the oral area. The tube feet may have captured food particles that entered the oral area and/or enhanced respiration. The pentameral symmetry of the oral surface transitions to eight columns in which the plates are vertically offset resulting in a spiral appearance. This change in symmetry may reflect flexibility in the evolutionary development of the axial and extraxial zones in early echinoderm evolution.

opencc-zeroDec 2016View details →

Data from: New crinoids from the Baltic region (Estonia): fossil tip-dating phylogenetics constrains the origin and Ordovician–Silurian diversification of the Flexibilia (Echinodermata)

This study documents previously unknown taxonomic and morphological diversity among early Palaeozoic crinoids. Based on highly complete, well preserved crown material, we describe two new genera from the Ordovician and Silurian of the Baltic region (Estonia) that provide insight into two major features of the geological history of crinoids: the early evolution of the flexible clade during the Great Ordovician Biodiversification Event (GOBE), and their diversification history surrounding the end-Ordovician mass extinction. The unexpected occurrence of a highly derived sagenocrinid, Tintinnabulicrinus estoniensis gen. et. sp. nov., from Upper Ordovician (lower Katian) rocks of the Baltic palaeocontinent provides high-resolution temporal, taxonomic and palaeobiogeographical constraints on the origin and early evolution of the Flexibilia. The Silurian (lower Rhuddanian, Llandovery) Paerticrinus arvosus gen. et sp. nov. is the oldest known Silurian crinoid from Baltica and thus provides the earliest Baltic record of crinoids following the aftermath of the end-Ordovician mass extinction. A Bayesian 'fossil tip-dating' analysis implementing the fossilized birth–death process and a relaxed morphological clock model suggests that flexibles evolved c. 3 million years prior to their oldest fossil record, potentially involving an ancestor–descendant relationship (via 'budding' cladogenesis or anagenesis) with the paraphyletic cladid Cupulocrinus. The sagenocrinid subclade rapidly diverged from 'taxocrinid' grade crinoids during the final stages of the GOBE, culminating in maximal diversity among Ordovician crinoid faunas on a global scale. Remarkably, diversification patterns indicate little taxonomic turnover among flexibles across the Late Ordovician mass extinction. However, the elimination of closely related clades may have helped pave the way for their subsequent Silurian diversification and increased ecological role in post-Ordovician Palaeozoic marine communities. This study highlights the significance of studies reporting faunas from undersampled palaeogeographical regions for clade-based phylogenetic studies and improving estimates of global biodiversity through geological time.

opencc-zeroDec 2018View details →

Data from: A new ophiocistioid with soft-tissue preservation from the Silurian Herefordshire Lagerstätte, and the evolution of the holothurian body plan

Reconstructing the evolutionary assembly of animal body plans is challenging when there are large morphological gaps between extant sister taxa, as in the case of echinozoans (echinoids and holothurians). However, the inclusion of extinct taxa can help bridge these gaps. Here we describe a new species of echinozoan, Sollasina cthulhu, from the Silurian Herefordshire Lagerstätte, UK. S. cthulhu belongs to the ophiocistioids, an extinct group that shares characters with both echinoids and holothurians. Using physical-optical tomography and computer reconstruction, we visualize the internal anatomy of S. cthulhu in three dimensions, revealing inner soft tissues that we interpret as the ring canal, a key part of the water vascular system that was previously unknown in fossil echinozoans. Phylogenetic analyses strongly suggest that Sollasina and other ophiocistioids represent a paraphyletic group of stem holothurians, as previously hypothesized. This allows us to reconstruct the stepwise reduction of the skeleton during the assembly of the holothurian body plan, which may have been controlled by changes in the expression of biomineralization genes.

opencc-by-nc-1.0Oct 2017View details →

Hemicyclaspis (Silurian jawless fish)

This is a beautiful fossil (specimen BU 2469) of the Silurian jawless fish *Hemicyclaspis murchisoni*, from the Downton Castle Sandstone Formation of Gornal, West Midlands, UK. The specimen is on display at the Lapworth Museum of Geology, in the Evolution of Life gallery. Specimen digitised using an Artec Spider 3D scanner by University of Birmingham Palaeobiology & Palaeoenvironments undergraduate student Luke Meade. Source: Objaverse 1.0 / Sketchfab

FIGURE 7 in A new generic name, Semigothograptus, for Gothograptus? meganassa Rickards & Palmer, 2002, from the Silurian post- lundgreni Biozone recovery phase, and comparative morphology of retiolitids from the lowermost upper Homerian (upper Wenlock)

FIGURE 7. SEM pictures of nassa type genicular hoods of Gothograptus nassa Holm, 1890 and Semigothograptus meganassa (Rickards & Palmer, 2002). A – D. Semigothograptus meganassa, ZPAL G. 54 / 1, 1649.2 m, Bartoszyce IG- 1 drill core, Poland, uppermost part of dubius / nassa Biozone, A. hood of th 2 2 with marked surface bandages (arrow). B. enlargement showing pustules on parallel bandages (arrow), C. hood of th 1 2 with marked space between bandages (arrow), D. hood of th 3 2, surface bandages (arrow). E – H. Gothograptus nassa, Bartoszyce IG- 1, 1655.8 m, dubius / nassa Biozone, E. whole hood of th 3 2, irregular bandages arrowed, specimen ZPAL G. 54 / 3. F – G. enlargement of hood, ZPAL G. 54 / 9, F. showing pustules on parallel bandages (arrows), G. presenting edges of subjacent bandages (arrows). H. fragment of hood of mature specimen with thick layer of irregular bandages with distinctive pustules and parallel bandages (arrow), ZPAL G. 54 / 6.

FIGURE 6 in A new generic name, Semigothograptus, for Gothograptus? meganassa Rickards & Palmer, 2002, from the Silurian post- lundgreni Biozone recovery phase, and comparative morphology of retiolitids from the lowermost upper Homerian (upper Wenlock)

FIGURE 6. Silurian paleogeographic map with occurrences of Semigothograptus new genus. Localities and graptolite data derived from the following literature sources; 1. Northeastern Poland (Baltica): this paper. 2. United Kingdom (Avalonia): Rickards & Palmer 2002. 3. Bohemia: KozłowskāDawidziuk et al. 2001. 4. Thuringia (Saxo-Thuringia): Jaeger 1991.

FIGURE 5 in A new generic name, Semigothograptus, for Gothograptus? meganassa Rickards & Palmer, 2002, from the Silurian post- lundgreni Biozone recovery phase, and comparative morphology of retiolitids from the lowermost upper Homerian (upper Wenlock)

FIGURE 5. Stratigraphical ranges of the Semigothograptus meganassa (Rickards & Palmer, 2002) in the Homerian at United Kingdom (Rickards & Palmers 2002), Czech Republic (Kozłowska et al. 2001), Germany (Maletz 2010), and Poland (Kozłowska this paper). Abbreviations: L. Hom.—Lower Homerian, Rep.—Republic.

FIGURE 3 in A new generic name, Semigothograptus, for Gothograptus? meganassa Rickards & Palmer, 2002, from the Silurian post- lundgreni Biozone recovery phase, and comparative morphology of retiolitids from the lowermost upper Homerian (upper Wenlock)

FIGURE 3. Light photos of Semigothograptus meganassa (Rickards & Palmer, 2002), specimen broken into two parts, ZPAL G.54/2, Bartoszyce IG-1 drill core, depth 1649.2 m; A. with sediment before cleaning in HF; B–C. two sides of lower part of the fragment after cleaning in HF. Abbreviation: lat. ap. rod—lateral apertural rod.

FIGURE 4 in A new generic name, Semigothograptus, for Gothograptus? meganassa Rickards & Palmer, 2002, from the Silurian post- lundgreni Biozone recovery phase, and comparative morphology of retiolitids from the lowermost upper Homerian (upper Wenlock)

FIGURE 4. Comparison of the main structures of tubaria used in this study. A. Papiliograptus papilio Lenz & Kozłowska- Dawidziuk, 2002, Šiupyliai-69 borehole, Lithuania; B. Semigothograptus meganassa (Rickards & Palmer, 2002), ZPAL G.54/ 1, Bartoszyce IG-1 drill core, depth 1649.2 m; C-D. Gothograptus nassa Holm, 1890, C. young colony, reverse side, ZPAL G.54/4, Bartoszyce IG-1 drill core, depth 1656.8 m, D. mature colony with broken distal end, obverse side, ZPAL G.54/5, Bartoszyce IG-1 drill core, depth, 1655.8 m. Scale 1 mm for all pictures. Abbreviations: anc.—ancora, sl.—sleeve, umbr.— umbrella.

FIGURE 2 in A new generic name, Semigothograptus, for Gothograptus? meganassa Rickards & Palmer, 2002, from the Silurian post- lundgreni Biozone recovery phase, and comparative morphology of retiolitids from the lowermost upper Homerian (upper Wenlock)

FIGURE 2. Proximal ends showing ancora umbrella looping meshes of A. Gothograptus nassa Holm, 1890 early growth stage, ZPAL G.54/7, Bartoszyce IG-1 drill core, depth 1656.8 m; B. Semigothograptus meganassa (Rickards & Palmer, 2002), ZPAL G.54/1, Bartoszyce IG-1 drill core, depth 1649.2 m.

FIGURE 1 in A new generic name, Semigothograptus, for Gothograptus? meganassa Rickards & Palmer, 2002, from the Silurian post- lundgreni Biozone recovery phase, and comparative morphology of retiolitids from the lowermost upper Homerian (upper Wenlock)

FIGURE 1. Tubaria of A–C. Gothograptus nassa Holm, 1890 and D. Semigothograptus meganassa (Rickards & Palmer, 2002) from dubius/nassa Biozone, Bartoszyce IG-1 drill core, Poland. A. Gothograptus nassa, obverse view of mature tubarium with destroyed distal end, long morphotype, ZPAL G.54/5, 1655.8 m, B. latero-ventral view of mature tubarium with appendix, short morphotype, ZPAL G.54/8, 1658.8 m, C. long appendix, ZPAL G.54/10, 1656.8 m. D. Semigothograptus meganassa, obverse view, ZPAL G.54/1, 1649.2 m, uppermost part of dubius/nassa Biozone.

FIGURE 7 in A new generic name, Semigothograptus, for Gothograptus? meganassa Rickards & Palmer, 2002, from the Silurian post- lundgreni Biozone recovery phase, and comparative morphology of retiolitids from the lowermost upper Homerian (upper Wenlock)

FIGURE 7. SEM pictures of nassa type genicular hoods of Gothograptus nassa Holm, 1890 and Semigothograptus meganassa (Rickards & Palmer, 2002). A–D. Semigothograptus meganassa, ZPAL G.54/1, 1649.2 m, Bartoszyce IG-1drill core, Poland, uppermost part of dubius/nassa Biozone, A. hood of th22 with marked surface bandages (arrow). B. enlargement showing pustules on parallel bandages (arrow), C. hood of th12 with marked space between bandages (arrow), D. hood of th32, surface bandages (arrow). E–H. Gothograptus nassa, Bartoszyce IG-1, 1655.8 m, dubius/nassa Biozone, E. whole hood of th32, irregular bandages arrowed, specimen ZPAL G.54/3. F–G. enlargement of hood, ZPAL G.54/9, F. showing pustules on parallel bandages (arrows), G. presenting edges of subjacent bandages (arrows). H. fragment of hood of mature specimen with thick layer of irregular bandages with distinctive pustules and parallel bandages (arrow), ZPAL G.54/6.