| 1. |
- Cuthbertson, Robin S., et al.
(author)
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A new species of mosasaur (Squamata: Mosasauridae) from the Pierre Shale (lower Campanian) of Manitoba
- 2007
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In: Canadian journal of earth sciences (Print). - : NRC Research Press. - 0008-4077 .- 1480-3313. ; 44:5, s. 593-606
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Journal article (peer-reviewed)abstract
- Plioplatecarpus nichollsae, sp. nov., from the lower Campanian (Pembina Member, Pierre Shale Formation) is diagnosed by the following: a thickened ventral rim of the external naris, a short supratemporal fenestra, a frontal shield with well-developed posterolateral lappets that overlap the parietal dorsally, proximal rib shafts with an approximately circular (but not inflated) cross section, a scapula shaped as in other Plioplatecarpus species but approximately the same size (not larger) than the coracoid, and a moderately large parietal foramen that reaches the frontoparietal suture but does not invade the frontal. The last two characters require that the diagnosis of the genus Plioplatecarpus be emended. With other Plioplatecarpus species, P. nichollsae shares a robust humerus with a distal expansion at least as great as the total length of the bone, a rectangular preorbital frontal shield, a "peg and socket" postorbitofrontal-jugal articulation, a transversely directed ectopterygoid process of the pterygoid, a large, robust quadrate with a distinct eminence on the posterior surface of its shaft, an unossified gap in the ventral wall of the basioccipital, and at least 11 pygal vertebrae. P. nichollsae also shares primitive features with Platecarpus, as well as features apparently intermediate betweenPlatecarpus and Plioplatecarpus. Revision of the genus Platecarpus, currently hypothesized to be both paraphyletic and polyphyletic, as well as a better understanding of the early Campanian mosasaur fauna from the Morden area, are necessary before the phylogenetic significance of some of these characters, and therefore the relationships of Plioplatecarpus nichollsae, can be fully resolved.
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| 2. |
- Daley, Allison C.
(author)
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Statistical analysis of mixed-motive shell borings in Ordovician, Silurian, and Devonian brachiopods from northern and eastern Canada
- 2008
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In: Canadian journal of earth sciences (Print). - 0008-4077 .- 1480-3313. ; 45:2, s. 213-229
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Journal article (peer-reviewed)abstract
- Hundreds of shell borings of different origin and displaying variable patterns were found in strophomenide, pentameride, and orthide brachiopods of five Paleozoic localities in northern and eastern Canada. The borings were analyzed using simple statistics as well as cluster and nonmetric multidimensional scaling analyses. At the Ordovician Anticosti Island locality, all borings are parasitic or post-mortem in origin, while at the Wenlock-Ludlow Baillie-Hamilton Island, almost all borings are predatory. At the remaining three localities, borings represent a mix of predatory, parasitic, and post-mortem domichnial borings in all three brachiopod taxa, the proportions of which were controlled largely by brachiopod shell morphology and paleoecology. For the strophomenides, predatory borings can be segregated from parasitic and post-mortem domichnial using simple and multivariate statistical analyses. Sowerbyella-type strophomenides have a higher proportion of predatory borings at the Lochkovian localities than at the Ordovician localities, while the reverse is true for the Strophomena-type strophomenides. In pentamerides and orthides, very few predatory borings are identified; most borings were emplaced by parasitic or post-mortem domichnial borers. In pentamerides, this is due to the internal structure of the shells, which elevated the muscles of the organism above the shell floor, rendering them inaccessible to boring predators. In orthides, more deliberate defense mechanisms such as toxins or external ornamentation may have deterred predation. This study indicates that throughout the Paleozoic interactions between borers and brachiopods were complex but can be elucidated using a large sample size and statistical analyses.
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| 3. |
- Ebbestad, Jan Ove R., et al.
(author)
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Failed predation in Late Ordovician gastropods (Mollusca) from Manitoulin Island, Ontario, Canada
- 2008
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In: Canadian journal of earth sciences (Print). - 0008-4077 .- 1480-3313. ; 45:2, s. 231-241
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Journal article (peer-reviewed)abstract
- Shell repairs resulting from presumed failed predation are documented in gastropods from the Late Ordovician (Cincinnatian; Richmondian) mid-to-upper Kagawong Submember of the Georgian Bay Formation on Manitoulin Island, Ontario, Canada. The bryozoan-mollusc biota and associated sediments generally suggest nearshore, shallow (<10m), low energy (lagoonal), and perhaps mesotrophic to eutrophic conditions. Two sample sets from this unit have been studied for shell repair. One of the more commonly applied estimates of shell repair frequencies involves division of the number of individuals with at least one scar by the total number of individuals in the sample (the Individuals with scars method). Using this calculation, 207 specimens ofLophospira trilineata Ulrich and Scofield yielded a shell repair frequency of 4.8%; in 28specimens of Trochonemella sp. the shell repair frequency was 35.7%. Repairs in Trochonemella occur primarily in the larger size class, suggesting that a size refuge was achieved by this species. Low repair frequencies in L. trilineata suggest predation with a higher success rate or fewer encounters. This study demonstrates that the paradigm of a standardized low level of shell repair in Ordovician and Silurian gastropods is oversimplistic and a range of frequency rates can be expected.
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| 4. |
- Evans, David C., et al.
(author)
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An unusual hadrosaurid braincase from the Dinosaur Park Formation and the biostratigraphy of Parasaurolophus(Ornithischia: Lambeosaurinae) from southern Alberta
- 2009
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In: Canadian journal of earth sciences (Print). - : NRC Research Press. - 0008-4077 .- 1480-3313. ; 46:11, s. 791-800
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Journal article (peer-reviewed)abstract
- The lambeosaurine hadrosaurid Parasaurolophus is known from rare occurrences in Campanian deposits of western North America. A previously undescribed large hadrosaurid braincase from the Dinosaur Park Formation (Alberta, Canada) is assigned to the genusParasaurolophus on the basis of several derived characters associated with the frontal–nasal articulation at the base of the crest. This identification is supported by two separate phylogenetic analyses, in which the specimen clusters with other more completely known Parasaurolophusexemplars. If correctly identified, the specimen represents the third and largest cranial specimen of the genus from the Late Cretaceous of Alberta. The specimen occurs in the same deposits as the holotype specimen of Parasaurolophus walkeri and may represent a late ontogenetic stage of this taxon. As opposed to a small frontal dome in the holotype of P. walkeri, the external contribution of the frontal to the skull roof is obliterated in the new specimen. If these hypothesized ontogenetic changes in the skull roof correlate with the size and posterodorsal development of the crest, as in other lambeosaurines, it suggests that the crest had not reached its full expression in the holotype. When placed into a detailed biostratigraphic context for the first time, the limited Parasaurolophus material from the Belly River Group is distributed in the lower half of the Dinosaur Park Formation at Dinosaur Provincial Park. This suggests thatParasaurolophus may be associated with the lower Centrosaurus–Corythosaurus assemblage zone and may have preferred more inland environments than other hadrosaurids, such asLambeosaurus and Prosaurolophus.
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| 5. |
- Morris, George A., et al.
(author)
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Correlation of mid-Cretaceous granites with source terranes in the northern Canadian Cordillera
- 2008
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In: Canadian journal of earth sciences (Print). - 0008-4077 .- 1480-3313. ; 45:3, s. 389-403
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Journal article (peer-reviewed)abstract
- This study presents a broad geochemical and isotopic synthesis of mid-Cretaceous granites in the southern Yukon as well as a comparative data set for granites sourced from, and hosted by, accreted terranes in the west through to ancient cratonic rocks in the east. We present data from a traverse perpendicular to the strike of the northern Canadian Cordillera allowing comparison with the growing body of such data derived from the host terranes. Trace elements, specifically the ""subduction signature,"" allow the discrimination of oceanic verses continental crustal sources. Comparison of isotopic ratios of Sr and, particularly, Nd with published data further refine the correlation of granites with their source terranes. Granites are initially divided based upon their host morphogeological belts, however, our study indicates that the source terranes transcend these traditional boundaries. For Intermontane Belt hosted granites three distinct sources can be identified: an isotopically primitive (Sr-i, 0.7050; Nd-T, 2.3 toa-1.2), subduction-related source probably associated with the mid-Cretaceous continental margin; an isotopically primitive (Sr-i, 0.7032 to 0.7035; Nd-T, 4.2 to 1.4), non-subduction-related source identified as the host Cache Creek terrane; and an isotopically slightly more evolved (Sr-i, 0.7094 to 0.7101; Nd-T, 4.5 toa-7.3), subduction-related source identified as the host Stikine terrane. Immediately east of the Teslin Tectonic Zone (TTZ), pericratonic Omineca granites (Sr-i, 0.7032 to 0.7076; Nd-T, 2.0 toa-5.4) do not correlate with their host terranes, but instead show marked similarities with granites immediately to the west of the TTZ suggesting that the same, or similar crustal sources extend further east in the subsurface than previously thought. In the eastern pericratonic Omineca Belt, there is a substantial jump to more evolved isotopic values (Sr-i, 0.7172 to 0.7354; Nd-T,a-16.6 toa-21.7) for granites that extend to the most easterly exposed plutons of the cratonic Omineca Belt. These more isotopically evolved granites correlate with isotopic values for the pericratonic Yukon-Tanana and Cassiar terranes, as well as cratonic North America.
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| 6. |
- Tapanila, Leif, et al.
(author)
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Benthic island community on the back of a snail: Silurian, Anticosti Island, Canada
- 2008
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In: Canadian journal of earth sciences (Print). - 0008-4077 .- 1480-3313. ; 45:2, s. 203-211
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Journal article (peer-reviewed)abstract
- A single specimen of the large Silurian gastropod Phanerotrema sp. from the Goéland Member on Anticosti Island preserves an outstanding microcosm of its surrounding community, including multiple trophic groups, strategies for niche partitioning, and innovative adaptations for survival in a mud-dominated marine ecosystem. At least seven associations are recorded in this fossil specimen, including the gastropod itself, healed breakage from an apparently failed attempt at durophagous predation, domichnial bioerosion, encrustation by a stromatoporoid, nestling behaviour and commensal embedment by a lingulid brachiopod, and epifaunal attachment by two cornulitids. As a benthic island, the gastropod conch provided a favourable isolated habitat for hard substrate colonizers. This unique specimen sheds light on the broader Paleozoic ecosystem, including the potential importance of benthic islands in the evolution of niche-partitioning strategies in space-limited communities.
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