Four trilobite specimens, two of Ordovician, one of Silurian, and one of Devonian age, display ab... more Four trilobite specimens, two of Ordovician, one of Silurian, and one of Devonian age, display abnormal exoskeletal features ranging in expression from superficial to severe. Traumatic injury and developmental malfunction are considered the most probable causative mechanisms, each accounting for two of the abnormalities. Evidence of external healing of a marginal pygidial wound is apparent in one of the injured trilobites; the other may have succumbed to more extensive posterolateral pleural trauma. The two examples of developmental malfunction both involve disruption of axial and pleural regions of the pygidia. One was of limited effect, the second more severe and possibly fatal.
The fossil record of the basic xiphosurid horseshoe crab body plan has been extended back to the ... more The fossil record of the basic xiphosurid horseshoe crab body plan has been extended back to the Late Ordovician Period, about 445 million years ago, demonstrating an origin that lies outside of the paraphyletic ‘synziphosurines.’ Horseshoe crab body fossils are exceptionally rare and are found mostly in shallow coastal and marginal marine Konservat-Lagerstätten deposits. Their sporadic occurrences document a post-Cambrian
The relationships between early jawed vertebrates have been much debated, with cladistic analyses... more The relationships between early jawed vertebrates have been much debated, with cladistic analyses yielding little consensus on the position (or positions) of acanthodians with respect to other groups. Whereas one recent analysis showed various acanthodians (classically known as 'spiny sharks') as stem osteichthyans (bony fishes) and others as stem chondrichthyans, another shows the acanthodians as a paraphyletic group of stem chondrichthyans, and the latest analysis shows acanthodians as the monophyletic sister group of the Chondrichthyes. Methodology/Principal Findings: A small specimen of the ischnacanthiform acanthodian Nerepisacanthus denisoni is the first vertebrate fossil collected from the Late Silurian Bertie Formation Konservat-Lagersta ¨tte of southern Ontario, Canada, a deposit well-known for its spectacular eurypterid fossils. The fish is the only near complete acanthodian from pre-Devonian strata worldwide, and confirms that Nerepisacanthus has dentigerous jaw bones, body scales with superposed crown growth zones formed of ondontocytic mesodentine, and a patch of chondrichthyan-like scales posterior to the jaw joint. Conclusions/Significance: The combination of features found in Nerepisacanthus supports the hypothesis that acanthodians could be a group, or even a clade, on the chondrichthyan stem. Cladistic analyses of early jawed vertebrates incorporating Nerepisacanthus, and updated data on other acanthodians based on publications in press, should help clarify their relationships.
Articulated plumulitid machaeridians are rarely preserved intact. Here, we describe a complete sp... more Articulated plumulitid machaeridians are rarely preserved intact. Here, we describe a complete specimen of Plumulites canadensis (Woodward, 1889) retaining much of the head region. The two anteriormost pairs of shell plates are quite distinct from the rest in outline, density of concentric rugae, and especially the radial ornamentation of the second pair. We demonstrate that the latter condition is present in other complete plumulitids and therefore widespread, which elucidates a larger diversity in morphology of plumulitids than realized previously.
Odontogriphus omalus was originally described as a problematic non-biomineralized lophophorate or... more Odontogriphus omalus was originally described as a problematic non-biomineralized lophophorate organism. Here we reinterpret Odontogriphus based on 189 new specimens including numerous exceptionally well-preserved individuals from the Burgess Shale
... Inversion and rotation of the cranidium during exuviation has also been recorded .in Telephin... more ... Inversion and rotation of the cranidium during exuviation has also been recorded .in Telephina (Fischer 1946, Fig. ... 36: 17-19, Fig. 15). Unlike the phacopine genera which lack functional facial sutures in the adults, the sutures are functional in Telephina and Carolinites. ...
The bizarre morphology of living Pycnogonida, known colloquially as sea spiders, has long fueled ... more The bizarre morphology of living Pycnogonida, known colloquially as sea spiders, has long fueled dissent over their status within the arthropods. Pycnogonids figure prominently in recent analyses of anterior limb homologies and ancestral crown-group euarthropod relationships, with support for the concept of Pycnogonida as sister taxon to Euchelicerata now contested by proponents of a more basal position between Radiodonta and all other arthropods. A challenge to further elucidation of their phylogenetic position is the exceptional rarity and disjunct distribution of pycnogonids in the fossil record, due largely to their fragile unmineralized exoskeletons. New fossil discoveries therefore have the potential to add significantly to knowledge of their evolution, paleoecology, and paleobiogeography. Here we report the first known occurrence of fossil pycnogonids from rocks of Ordovician age, bridging a 65 Myr gap between controversial late Cambrian larval forms and a single documented S...
... Priscansermarinus barnetti, a probable lepadomorph barnacle from Middle Cambrian Burgess Shal... more ... Priscansermarinus barnetti, a probable lepadomorph barnacle from Middle Cambrian Burgess Shale of British Columbia. Desmond Collins, and David M. Rudkin R. Ont. Mus., Toronto, ON, Canada. This record provided courtesy of AGI/GeoRef. ...
... Editor: Waddington, Janet; Rudkin, David M. Corporate Author: Royal Ontario Museum Title of S... more ... Editor: Waddington, Janet; Rudkin, David M. Corporate Author: Royal Ontario Museum Title of Source: Proceedings of the 1985 workshop on care and maintenance of natural history collections Title of Series: Life sciences miscellaneous publications, Publisher/Distributor ...
A new genus and species of articulated scleritomous metazoan, Curviconophorus andersoni, is descr... more A new genus and species of articulated scleritomous metazoan, Curviconophorus andersoni, is described on the basis of a unique specimen from the Late Ordovician Georgian Bay Formation of southern Ontario. The affinities of the organism remain obscure, although the overall morphology of component sclerites suggests a possible relationship with the Agmata, an extinct phylum-level group so far known with certainty only from the Cambrian. Curved, conical elements of the scleritome are preserved as internal moulds and yield no details of ultrastructure or primary composition, precluding detailed comparisons with the aggultinated, internally laminated sclerites of agmatans. Curviconophorus gen.nov. has a scleritome architecture similar to that of the Early Ordovician putative agmatan Dimorphoconus granulatus, though it has fewer elements that are strictly monomorphic.
Two similar species of Sphaerocoryphe, Sphaerocoryphe gemina sp.nov. and Sphaerocoryphe longispin... more Two similar species of Sphaerocoryphe, Sphaerocoryphe gemina sp.nov. and Sphaerocoryphe longispina sp.nov., from the Edinburg Formation (Blackriveran) of northwest Virginia are described. The most conspicuous differences lie in the pygidia. The protaspis closely resembles that of Ceraurinella; transitory pygidia are allocated to degrees one to eight, and the first appearance of the great spines provides a useful marker. Two ontogenetic series can be recognized, culminating in the two adult morphologies, and ruling out the possibility of a single dimorphic species. There are two profixigenal spines in meraspid cranidia up to 2.5 mm in sagittal length, one pair in larger cranidia of both species. The smallest hypostome possesses two lateral spines, later reduced to one. Hemisphaerocoryphe Reed is considered a junior subjective synonym of Sphaerocoryphe Angelin. The 29 named species are compared.
... How to Cite. Caron, J.-B., Scheltema, A., Schander, C. and Rudkin, D. (2007), Reply to Butter... more ... How to Cite. Caron, J.-B., Scheltema, A., Schander, C. and Rudkin, D. (2007), Reply to Butterfield on stem-group worms: fossil lophotrochozoans in the Burgess Shale. BioEssays, 29: 200202. ... 3 University of Bergen, Department of Biology, Bergen, Norway. 4 ...
... Healed injuries in Ogygopsis klotzi (Trilobita) from the Middle Cambrian of British Columbia.... more ... Healed injuries in Ogygopsis klotzi (Trilobita) from the Middle Cambrian of British Columbia. Post a Comment. CONTRIBUTORS: Author: Rudkin, David M. (b. 1951, d. ----. PUBLISHER: Royal Ontario Museum (Toronto). SERIES TITLE: YEAR: 1979. PUB TYPE: Book. ...
in which soft-bodied or lightly sclerotized fossils are preserved, are very rare in Ordovician st... more in which soft-bodied or lightly sclerotized fossils are preserved, are very rare in Ordovician strata. Three significant sites are known from Upper Ordovician rocks in Manitoba: at Cat Head -McBeth Point, William Lake, SOMMAIRE Les lagerstätten de conservation, ces sédiments contenant des fossiles d'organismes à corps mou ou légèrement sclérotisés particulièrement bien conservés, sont très rares dans les strates ordoviciennes. Trois sites d'importance sont connus dans des roches de l'Ordovicien supérieur à Cat Head, Manitoba, soit McBeth Point, William Lake et Airport Cove. Ces sites sont situés dans deux bassins sédimentaires distincts: les deux premiers sont situés dans le bassin de Williston, tandis que le second est situé dans le bassin de la baie d'Hudson. Les trois sites contiennent des fossiles marins, mais chacun présente un assemblage différent, chacun montrant une composante distincte de la diversité biologique d'alors. Les groupes les plus importants représentés, dans un ou plusieurs de ces sites, sont les algues, les éponges, les cnidarian medusae (méduses), les conularides, les trilobites, les euryptérides, xiphosurides (limules) et pycnogonides. Les différents biotopes reflètent les conditions de dépôt de chaque site. Nombre de ces fossiles sont inconnus ailleurs dans l'Ordovicien, au niveau de la famille ou du taxon supérieur de la classification. Ainsi, la province du Manitoba offre-telle une contribution importante à la connaissance de la biodiversité de l'Ordovicien supérieur.
Konservat-Lagerstatten , deposits in which soft-bodied or lightly sclerotized fossils are preserv... more Konservat-Lagerstatten , deposits in which soft-bodied or lightly sclerotized fossils are preserved, are very rare in Ordovician strata. Three significant sites are known from Upper Ordovician rocks in Manitoba: at Cat Head – McBeth Point, William Lake, and Airport Cove. These sites are in two distinct sedimentary basins: the former two are in the Williston Basin, while the latter is in the Hudson Bay Basin. All three sites contain marine fossils, but each has a different assemblage that contributes a distinct piece of the diversity picture. Important groups represented at one or more of the sites include seaweeds (algae), sponges, cnidarian medusae (jellyfish), conulariids, trilobites, eurypterids, xiphosurids (horseshoe crabs), and pycnogonids (‘sea spiders’). The different biotas reflect depositional conditions at each site. Many of the fossils are unknown elsewhere in the Ordovician at the family level or higher. The province of Manitoba therefore makes a significant contributio...
Specimens of Euproops sp. (Xiphosura, Chelicerata) from the Carboniferous Piesberg quarry near Os... more Specimens of Euproops sp. (Xiphosura, Chelicerata) from the Carboniferous Piesberg quarry near Osnabrück, Germany, represent a relatively complete growth series of 10 stages. Based on this growth sequence, morphological changes throughout the ontogeny can be identified. The major change affects the shape of the epimera of the opisthosoma. In earlier stages, they appear very spine-like, whereas in later stages the bases of these spine-like structures become broader; the broadened bases are then successively drawn out distally. In the most mature stage known, the epimera are of trapezoidal shape and approach each other closely to form a complete flange around the thoracetron (=fused tergites of the opisthosoma). These ontogenetic changes question the taxonomic status of different species of Euproops, as the latter appear to correspond to different stages of the ontogenetic series reconstructed from the Piesberg specimens. This means that supposed separate species could, in fact, represent different growth stages of a single species. It could alternatively indicate that heterochrony (=evolutionary change of developmental timing) plays an important role in the evolution of Xiphosura. We propose a holomorph approach, i.e., reconstructing ontogenetic sequences for fossil and extant species as a sound basis for a taxonomic, phylogenetic, and evolutionary discussion of Xiphosura.
Four trilobite specimens, two of Ordovician, one of Silurian, and one of Devonian age, display ab... more Four trilobite specimens, two of Ordovician, one of Silurian, and one of Devonian age, display abnormal exoskeletal features ranging in expression from superficial to severe. Traumatic injury and developmental malfunction are considered the most probable causative mechanisms, each accounting for two of the abnormalities. Evidence of external healing of a marginal pygidial wound is apparent in one of the injured trilobites; the other may have succumbed to more extensive posterolateral pleural trauma. The two examples of developmental malfunction both involve disruption of axial and pleural regions of the pygidia. One was of limited effect, the second more severe and possibly fatal.
The fossil record of the basic xiphosurid horseshoe crab body plan has been extended back to the ... more The fossil record of the basic xiphosurid horseshoe crab body plan has been extended back to the Late Ordovician Period, about 445 million years ago, demonstrating an origin that lies outside of the paraphyletic ‘synziphosurines.’ Horseshoe crab body fossils are exceptionally rare and are found mostly in shallow coastal and marginal marine Konservat-Lagerstätten deposits. Their sporadic occurrences document a post-Cambrian
The relationships between early jawed vertebrates have been much debated, with cladistic analyses... more The relationships between early jawed vertebrates have been much debated, with cladistic analyses yielding little consensus on the position (or positions) of acanthodians with respect to other groups. Whereas one recent analysis showed various acanthodians (classically known as 'spiny sharks') as stem osteichthyans (bony fishes) and others as stem chondrichthyans, another shows the acanthodians as a paraphyletic group of stem chondrichthyans, and the latest analysis shows acanthodians as the monophyletic sister group of the Chondrichthyes. Methodology/Principal Findings: A small specimen of the ischnacanthiform acanthodian Nerepisacanthus denisoni is the first vertebrate fossil collected from the Late Silurian Bertie Formation Konservat-Lagersta ¨tte of southern Ontario, Canada, a deposit well-known for its spectacular eurypterid fossils. The fish is the only near complete acanthodian from pre-Devonian strata worldwide, and confirms that Nerepisacanthus has dentigerous jaw bones, body scales with superposed crown growth zones formed of ondontocytic mesodentine, and a patch of chondrichthyan-like scales posterior to the jaw joint. Conclusions/Significance: The combination of features found in Nerepisacanthus supports the hypothesis that acanthodians could be a group, or even a clade, on the chondrichthyan stem. Cladistic analyses of early jawed vertebrates incorporating Nerepisacanthus, and updated data on other acanthodians based on publications in press, should help clarify their relationships.
Articulated plumulitid machaeridians are rarely preserved intact. Here, we describe a complete sp... more Articulated plumulitid machaeridians are rarely preserved intact. Here, we describe a complete specimen of Plumulites canadensis (Woodward, 1889) retaining much of the head region. The two anteriormost pairs of shell plates are quite distinct from the rest in outline, density of concentric rugae, and especially the radial ornamentation of the second pair. We demonstrate that the latter condition is present in other complete plumulitids and therefore widespread, which elucidates a larger diversity in morphology of plumulitids than realized previously.
Odontogriphus omalus was originally described as a problematic non-biomineralized lophophorate or... more Odontogriphus omalus was originally described as a problematic non-biomineralized lophophorate organism. Here we reinterpret Odontogriphus based on 189 new specimens including numerous exceptionally well-preserved individuals from the Burgess Shale
... Inversion and rotation of the cranidium during exuviation has also been recorded .in Telephin... more ... Inversion and rotation of the cranidium during exuviation has also been recorded .in Telephina (Fischer 1946, Fig. ... 36: 17-19, Fig. 15). Unlike the phacopine genera which lack functional facial sutures in the adults, the sutures are functional in Telephina and Carolinites. ...
The bizarre morphology of living Pycnogonida, known colloquially as sea spiders, has long fueled ... more The bizarre morphology of living Pycnogonida, known colloquially as sea spiders, has long fueled dissent over their status within the arthropods. Pycnogonids figure prominently in recent analyses of anterior limb homologies and ancestral crown-group euarthropod relationships, with support for the concept of Pycnogonida as sister taxon to Euchelicerata now contested by proponents of a more basal position between Radiodonta and all other arthropods. A challenge to further elucidation of their phylogenetic position is the exceptional rarity and disjunct distribution of pycnogonids in the fossil record, due largely to their fragile unmineralized exoskeletons. New fossil discoveries therefore have the potential to add significantly to knowledge of their evolution, paleoecology, and paleobiogeography. Here we report the first known occurrence of fossil pycnogonids from rocks of Ordovician age, bridging a 65 Myr gap between controversial late Cambrian larval forms and a single documented S...
... Priscansermarinus barnetti, a probable lepadomorph barnacle from Middle Cambrian Burgess Shal... more ... Priscansermarinus barnetti, a probable lepadomorph barnacle from Middle Cambrian Burgess Shale of British Columbia. Desmond Collins, and David M. Rudkin R. Ont. Mus., Toronto, ON, Canada. This record provided courtesy of AGI/GeoRef. ...
... Editor: Waddington, Janet; Rudkin, David M. Corporate Author: Royal Ontario Museum Title of S... more ... Editor: Waddington, Janet; Rudkin, David M. Corporate Author: Royal Ontario Museum Title of Source: Proceedings of the 1985 workshop on care and maintenance of natural history collections Title of Series: Life sciences miscellaneous publications, Publisher/Distributor ...
A new genus and species of articulated scleritomous metazoan, Curviconophorus andersoni, is descr... more A new genus and species of articulated scleritomous metazoan, Curviconophorus andersoni, is described on the basis of a unique specimen from the Late Ordovician Georgian Bay Formation of southern Ontario. The affinities of the organism remain obscure, although the overall morphology of component sclerites suggests a possible relationship with the Agmata, an extinct phylum-level group so far known with certainty only from the Cambrian. Curved, conical elements of the scleritome are preserved as internal moulds and yield no details of ultrastructure or primary composition, precluding detailed comparisons with the aggultinated, internally laminated sclerites of agmatans. Curviconophorus gen.nov. has a scleritome architecture similar to that of the Early Ordovician putative agmatan Dimorphoconus granulatus, though it has fewer elements that are strictly monomorphic.
Two similar species of Sphaerocoryphe, Sphaerocoryphe gemina sp.nov. and Sphaerocoryphe longispin... more Two similar species of Sphaerocoryphe, Sphaerocoryphe gemina sp.nov. and Sphaerocoryphe longispina sp.nov., from the Edinburg Formation (Blackriveran) of northwest Virginia are described. The most conspicuous differences lie in the pygidia. The protaspis closely resembles that of Ceraurinella; transitory pygidia are allocated to degrees one to eight, and the first appearance of the great spines provides a useful marker. Two ontogenetic series can be recognized, culminating in the two adult morphologies, and ruling out the possibility of a single dimorphic species. There are two profixigenal spines in meraspid cranidia up to 2.5 mm in sagittal length, one pair in larger cranidia of both species. The smallest hypostome possesses two lateral spines, later reduced to one. Hemisphaerocoryphe Reed is considered a junior subjective synonym of Sphaerocoryphe Angelin. The 29 named species are compared.
... How to Cite. Caron, J.-B., Scheltema, A., Schander, C. and Rudkin, D. (2007), Reply to Butter... more ... How to Cite. Caron, J.-B., Scheltema, A., Schander, C. and Rudkin, D. (2007), Reply to Butterfield on stem-group worms: fossil lophotrochozoans in the Burgess Shale. BioEssays, 29: 200202. ... 3 University of Bergen, Department of Biology, Bergen, Norway. 4 ...
... Healed injuries in Ogygopsis klotzi (Trilobita) from the Middle Cambrian of British Columbia.... more ... Healed injuries in Ogygopsis klotzi (Trilobita) from the Middle Cambrian of British Columbia. Post a Comment. CONTRIBUTORS: Author: Rudkin, David M. (b. 1951, d. ----. PUBLISHER: Royal Ontario Museum (Toronto). SERIES TITLE: YEAR: 1979. PUB TYPE: Book. ...
in which soft-bodied or lightly sclerotized fossils are preserved, are very rare in Ordovician st... more in which soft-bodied or lightly sclerotized fossils are preserved, are very rare in Ordovician strata. Three significant sites are known from Upper Ordovician rocks in Manitoba: at Cat Head -McBeth Point, William Lake, SOMMAIRE Les lagerstätten de conservation, ces sédiments contenant des fossiles d'organismes à corps mou ou légèrement sclérotisés particulièrement bien conservés, sont très rares dans les strates ordoviciennes. Trois sites d'importance sont connus dans des roches de l'Ordovicien supérieur à Cat Head, Manitoba, soit McBeth Point, William Lake et Airport Cove. Ces sites sont situés dans deux bassins sédimentaires distincts: les deux premiers sont situés dans le bassin de Williston, tandis que le second est situé dans le bassin de la baie d'Hudson. Les trois sites contiennent des fossiles marins, mais chacun présente un assemblage différent, chacun montrant une composante distincte de la diversité biologique d'alors. Les groupes les plus importants représentés, dans un ou plusieurs de ces sites, sont les algues, les éponges, les cnidarian medusae (méduses), les conularides, les trilobites, les euryptérides, xiphosurides (limules) et pycnogonides. Les différents biotopes reflètent les conditions de dépôt de chaque site. Nombre de ces fossiles sont inconnus ailleurs dans l'Ordovicien, au niveau de la famille ou du taxon supérieur de la classification. Ainsi, la province du Manitoba offre-telle une contribution importante à la connaissance de la biodiversité de l'Ordovicien supérieur.
Konservat-Lagerstatten , deposits in which soft-bodied or lightly sclerotized fossils are preserv... more Konservat-Lagerstatten , deposits in which soft-bodied or lightly sclerotized fossils are preserved, are very rare in Ordovician strata. Three significant sites are known from Upper Ordovician rocks in Manitoba: at Cat Head – McBeth Point, William Lake, and Airport Cove. These sites are in two distinct sedimentary basins: the former two are in the Williston Basin, while the latter is in the Hudson Bay Basin. All three sites contain marine fossils, but each has a different assemblage that contributes a distinct piece of the diversity picture. Important groups represented at one or more of the sites include seaweeds (algae), sponges, cnidarian medusae (jellyfish), conulariids, trilobites, eurypterids, xiphosurids (horseshoe crabs), and pycnogonids (‘sea spiders’). The different biotas reflect depositional conditions at each site. Many of the fossils are unknown elsewhere in the Ordovician at the family level or higher. The province of Manitoba therefore makes a significant contributio...
Specimens of Euproops sp. (Xiphosura, Chelicerata) from the Carboniferous Piesberg quarry near Os... more Specimens of Euproops sp. (Xiphosura, Chelicerata) from the Carboniferous Piesberg quarry near Osnabrück, Germany, represent a relatively complete growth series of 10 stages. Based on this growth sequence, morphological changes throughout the ontogeny can be identified. The major change affects the shape of the epimera of the opisthosoma. In earlier stages, they appear very spine-like, whereas in later stages the bases of these spine-like structures become broader; the broadened bases are then successively drawn out distally. In the most mature stage known, the epimera are of trapezoidal shape and approach each other closely to form a complete flange around the thoracetron (=fused tergites of the opisthosoma). These ontogenetic changes question the taxonomic status of different species of Euproops, as the latter appear to correspond to different stages of the ontogenetic series reconstructed from the Piesberg specimens. This means that supposed separate species could, in fact, represent different growth stages of a single species. It could alternatively indicate that heterochrony (=evolutionary change of developmental timing) plays an important role in the evolution of Xiphosura. We propose a holomorph approach, i.e., reconstructing ontogenetic sequences for fossil and extant species as a sound basis for a taxonomic, phylogenetic, and evolutionary discussion of Xiphosura.
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