| 1. |
- Garcia-Martin, E. Elena, et al.
(författare)
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Sources, Composition, and Export of Particulate Organic Matter Across British Estuaries
- 2023
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Ingår i: Journal of Geophysical Research - Biogeosciences. - : American Geophysical Union (AGU). - 2169-8953 .- 2169-8961. ; 128:4
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Tidskriftsartikel (refereegranskat)abstract
- Estuaries receive and process a large amount of particulate organic carbon (POC) prior to its export into coastal waters. Studying the origin of this POC is key to understanding the fate of POC and the role of estuaries in the global carbon cycle. Here, we evaluated the concentrations of POC, as well as particulate organic nitrogen (PON), and used stable carbon and nitrogen isotopes to assess their sources across 13 contrasting British estuaries during five different sampling campaigns over 1 year. We found a high variability in POC and PON concentrations across the salinity gradient, reflecting inputs, and losses of organic material within the estuaries. Catchment land cover appeared to influence the contribution of POC to the total organic carbon flux from the estuary to coastal waters, with POC contributions >36% in estuaries draining catchments with a high percentage of urban/suburban land, and <11% in estuaries draining catchments with a high peatland cover. There was no seasonal pattern in the isotopic composition of POC and PON, suggesting similar sources for each estuary over time. Carbon isotopic ratios were depleted (-26.7 +/- 0.42 parts per thousand, average +/- sd) at the lowest salinity waters, indicating mainly terrigenous POC (TPOC). Applying a two-source mixing model, we observed high variability in the contribution of TPOC at the highest salinity waters between estuaries, with a median value of 57%. Our results indicate a large transport of terrigenous organic carbon into coastal waters, where it may be buried, remineralized, or transported offshore. Plain Language Summary Estuaries transport and process a large amount terrigenous particulate organic matter (i.e., carbon and nitrogen) prior to its export to coastal waters. In order to understand the fate of organic carbon and the role of estuaries in the global carbon cycle it is essential to improve our knowledge on its composition, origin, and amount of carbon transported. We quantified the elemental concentrations and stable isotopes composition of carbon and nitrogen to quantify the amount of terrigenous particulate organic matter transported by 13 British estuaries, which drain catchments of diverse land cover under different hydrological conditions. We found a great variability in particulate organic carbon (POC) and particulate organic nitrogen concentrations across the salinity gradient, implying inputs, and losses of material within the estuaries. Each estuary had similar sources of particulate material throughout the year. In most of the estuaries, the POC had a terrigenous origin at the lowest salinity waters. The terrigenous organic carbon contribution decreased toward coastal waters with an average contribution of 57% at the highest salinity waters, indicating a large transport of terrigenous organic carbon into coastal waters.
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| 2. |
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| 3. |
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| 4. |
- Babcock, L.E., et al.
(författare)
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Anatomy, paleoecology, and taphonomy of the trilobite Buenellus from the Sirius Passet biota (Cambrian), North Greenland
- 2002
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Specimens of the nevadiid trilobite Buenellus higginsi from the Sirius Passet Biota (Buen Formation: Cambrian) of North Greenland show a combination of features reflecting both biomineralized and non-biomineralized anatomy, and providing direct or indirect evidence of paleoecologic associations and taphonomic history. Buenellus illustrates some key aspects of the role that trilobites played in the Early Paleozoic Marine Revolution (apparently serving as both predator and prey); its role in sediment-excavation, however, is unknown. The Sirius Passet Biota has a low diversity and low abundance of mineralizing organisms. Buenellus specimens, which account for most of the biomineralized skeletal parts, are normally preserved as decalcified, articulated exoskeletons, parallel to bedding. Their composition is dominated by clay minerals, although quartz, chlorite, muscovite, and chloritoid, are present, indicating metamorphism of shale to greenschist grade. Specimens of B. higginsi were preferentially oriented ventral-up as collected; this suggests both that minor current reorientation of remains occurred on the sea floor, and that strata at the Sirius Passet locality are overturned. Carnivory on B. higginsi is implied by the remains of anomalocaridids and other potential predators, and by sublethal predation scars. Slight disarticulation in the thoracic region of some fossils may have resulted from either decay or scavenging. Slender traces associated with various arthropod body fossils, including those of B. higginsi, suggests scavenging. Coprolites containing trilobite sclerites are unknown, and isolated, fragmentary sclerites are rare. Preserved non-biomineralized parts of B. higginsi are: 1, slender antennae projecting from under the exoskeleton; and 2, axial structures (inflated cavities lined with silica and limonite). Three types of axial structures are present: 1, a large cavity in the rear-subcentral part of the cephalon (interpreted as the stomach cavity); 2, a narrow, smooth-sided, medial tube that tapers slightly posteriorly (interpreted as the intestinal tract); and 3, metamerically divided pairs of sagitally located structures (interpreted as midgut glands). A carnivorous feeding habit is suggested by the lack of sediment-filled guts in B. higginsi.
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| 5. |
- Babcock, Loren E., et al.
(författare)
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Palaeobiology, taphonomy and stratigraphic significance of the trilobite BUENELLUS from the Sirius Passet Biota, Cambrian of North Greenland
- 2007
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Ingår i: Memoirs of the Association of Australasian Palaeontologists. - 0810-8889. ; 34, s. 401-418
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Tidskriftsartikel (refereegranskat)abstract
- The Sirius Passet Biota, collected from the lower Buen Formation (Cambrian Series 2, Stage 3), North Greenland, contains one species of trilobite, the nevadiid Buenellus higginsi Blaker, 1988. The species shows considerable morphological variation, especially in exoskeletal width. Many specimens of B. higginsi show some form of exceptionally preserved, non-biomineralised tissue. Structures interpreted as alimentary tracts and probable digestive glands are commonly preserved by silica and limonite. Antennae are rarely preserved, apparently through replication in clay minerals. Tendinous bars in the axial region also seem to be preserved by replication in clay minerals. Mineral-filled gut tracts in B. higginsi suggest they were fluid-filled at the time of burial, and that the species was a non-durophagous predator. Healed injuries, some of which are the result of unsuccessful predaceous attacks, are uncommon in B. higginsi. Other exoskeletons show evidence of post-mortem disruption, perhaps scavenging. Buenellus higginsi, one of the earliest known trilobites from Laurentia, seems to have played an important role in the Sirius Passet ecosystem, serving both as predator on, and prey for, contemporary animals.
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| 6. |
- Conway Morris, Simon, et al.
(författare)
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The earliest annelids : Lower Cambrian polychaetes from the Sirius Passet Lagerstätte, Peary Land, North Greenland
- 2008
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Ingår i: Acta Palaeontologica Polonica. - 0567-7920 .- 1732-2421. ; 53:1, s. 137-148
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Tidskriftsartikel (refereegranskat)abstract
- Apart from the Phyllopod Bed of the Burgess Shale (Middle Cambrian) polychaete annelids are practically unknown from any of the Cambrian Lagerstdtten. This is surprising both because their diversity in the Burgess Shale is considerable, while to date the Chengjiang Lagerstatte which is equally impressive in terms of faunal diversity has no reliable records of any annelids. Here we describe, on the basis of about 40 specimens, Phragmochaeta canicularis gen. et sp. nov. from the Lower Cambrian Sirius Passet Lagerstatte of Peary Land, North Greenland. This makes it by far the oldest known polychaete, with a likely age of lower to middle Atdabanian, The body consists of approximately 20 segments, each bearing notochaetae and neurochaetae. The former appeared to have formed a felt-like covering on the dorsum, whilst the neurochaetae projected obliquely to the longitudinal axis. Apart from minor differences in chaetal size at either end there is no other tagmosis. Details of the head are obscure, and presence of palps, tentacles and eyes are conjectural. Jaws appear to have been absent. The gut was straight, and flanked by massive longitudinal musculature. P. canicularis was evidently benthic, propelling itself on the neurochaetae, with the dorsal neurochaetae conferring protection. Its stratigraphic position and generalized appearance are consistent with P. canicularis being primitive, but the phylogenetic relationships within the polychaetes remain problematic, principally because of paucity of relevant morphological information.
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| 7. |
- Ebbestad, Jan Ove R., et al.
(författare)
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Predation on bellerophontiform molluscs in the Palaeozoic
- 2009
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Ingår i: Lethaia. - : Scandinavian University Press / Universitetsforlaget AS. - 0024-1164 .- 1502-3931. ; 42:4, s. 469-485
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Tidskriftsartikel (refereegranskat)abstract
- Shell repair assumed to result from failed predation is documented in 66 specimens of Ordovician-Carboniferous bellerophontiform tergomyan and gastropod molluscs to examine the relationship between the distribution and appearance of injuries, shell morphology and the internal anatomy of the molluscs, as well as the attack strategies of the presumed predators. Furthermore, the distribution of repaired injuries from failed attacks along the apertural margin as a reflection of the nature of the margin and emarginations is investigated. Bellerophontiform molluscs are ideal for this study because of their distinctive isostrophic morphology and the possibility to directly compare broad and narrow conchs with either deep or shallow medial emarginations. The results show that taxa with a deep medial emargination in the form of a slit have significantly more medial injuries than lateral ones. Near-equal frequencies of lateral and medial injuries in specimens with a shallow emargination (slit or sinus) suggest random distribution. Shell form (narrow or broad) does not exert overall control on the distribution of injuries except, perhaps, in some broad explanate shells with an insignificant medial emargination. While this suggests that it is the type of medial emargination that governs distribution of injuries in these forms, it is not clear if this is a result of passive selection due to structural geometry or preferential targeting by predators (i.e. site-specific mode of attack). Predation strategies on bellerophontiform molluscs thus seem to be dependent on the morphological features of the shells rather than their interpretation as tergomyan or gastropod.
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| 8. |
- Ebbestad, Jan Ove R., 1967-, et al.
(författare)
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Shell injuries, repair and malformation in the early Cambrian mollusc Helcionella antiqua from Scania, Sweden
- 2022
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Ingår i: GFF. - : Taylor & Francis. - 1103-5897 .- 2000-0863. ; 144:3-4, s. 203-209
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Tidskriftsartikel (refereegranskat)abstract
- Three cases of repaired injuries and malformation in specimens of the helcionelloid mollusc Helcionella antiqua (Ki & UAELIG;r, 1917) from the lower Cambrian (Cambrian Series 2, Stage 4) Gislov Formation of southern Sweden document some of the oldest known durophagous attacks on Palaeozoic molluscs. Two of the injuries are developed as clefts, of which one had a severe effect on the continued growth of the shell. The third example is a large embayment removing large portions of the supra-apical part of the shell. A similar repaired injury is known in the slightly older mollusc Marocella mira Geyer, 1986. from Antarctica and Australia. The morphology of the injuries and the hydrodynamically quiet depositional setting suggests that the shell damage was caused by failed predatory attacks. The location of the repaired injuries suggests that the attacks may have targeted the head region of the molluscs, thus supporting an endogastrically coiled orientation of the shell in Helcionella. Only three repaired injuries in 252 Helcionella specimens were found, giving a shell repair frequency of 1.2%. All three examples occur in the larger size classes. The size-frequency distribution (N = 182) is strongly right skewed, which could suggest high input of juvenile specimens into the assemblage. The assemblage is interpreted as a time averaged and mixed death assemblage, albeit with good correspondence with the living shelly assemblage, due to a relatively thin, homogenous unit that may suggest within-habitat time averaging.
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| 9. |
- Geyer, Gerd, et al.
(författare)
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A remarkable Amgan (Middle Cambrian, Stage 5) fauna from the Sauk Tanga, Madygen region, Kyrgyzstan
- 2014
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Ingår i: Bulletin of Geosciences. - : Czech Geological Survey. - 1214-1119 .- 1802-8225. ; 89:2, s. 375-400
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Tidskriftsartikel (refereegranskat)abstract
- Early Middle Cambrian bituminous coquinoid limestones from a tectonically isolated outcrop in southwestern Kyrgyzstan yield a remarkably diverse fauna, with stem-group cnidarians, trilobites, rhynchonelliformean brachiopods, and other shelly fossils. The fossil site is in the northern foothills of the Turkestan Range and thus forms part of the westernmost extension of the South Tien Shan. The fauna includes two fairly well known trilobite species, Glabrella ventrosa Lermontova, 1940 and Dorypyge richthofeniformis Lermontova, 1940, that provide confident support for an Amgan age of the rocks. New described taxa include the stem-group cnidarian Cambroctoconus kyrgyzstanicus Peel sp. nov., the trilobite Olenoides sagittatus Geyer sp. nov., and the helcionelloid Manasoconus bifrons Peel gen. et sp. nov. Additional fossils within the samples include the trilobites Olenoides sp. A, Kootenia sp., and Pseudoeteraspis? sp.; the rhynchonelliform brachiopods Narynella cf. ferganensis (Andreeva, 1962), Narynella? sp., Austrohedra? sp. nov., and two species of uncertain generic affinity; the tommotiid Tesella sp.; the hyolithelminth Hyolithellus sp.; and the palaeoscolecid Hadimopanella oezgueli Gedik, 1977. Of particular interest is Cambroctoconus kyrgyzstanicus with an octagonal corallum and a sparsely septate calyx.
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| 10. |
- Geyer, Gerd, et al.
(författare)
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Elrathia hensonensisnomen novum, new replacement name for Elrathia groenlandica Geyer and Peel, 2017 (Trilobita, Ptychopariacea)
- 2020
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Ingår i: Journal of Paleontology. - : Cambridge University Press (CUP). - 0022-3360 .- 1937-2337. ; 94:5, s. 1007-1007
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Tidskriftsartikel (refereegranskat)abstract
- In an article by Geyer and Peel (2017, p. 288), we inadvertently coined a species-group name, Elrathia groenlandica Geyer and Peel, 2017 for a trilobite species of the superfamily Ptychopariacea. This name is a junior homonym of Elrathia? groenlandica Poulsen, 1927 and is thus invalid (ICZN Article 57.2; see International Commission on Zoological Nomenclature, 1999). We therefore propose Elrathia hensonensis new name as the replacement name for E. groenlandica Geyer and Peel, 2017. The new species name is derived from the Henson Gletscher area, North Greenland, the region where the type locality of this species is located.
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| 11. |
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| 12. |
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| 13. |
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| 14. |
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| 15. |
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| 16. |
- Isakar, M., et al.
(författare)
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Lower Cambrian helcionelloid molluscs from Estonia
- 2007
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Ingår i: GFF. - : Informa UK Limited. - 1103-5897 .- 2000-0863. ; 129:3, s. 255-262
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Tidskriftsartikel (refereegranskat)abstract
- Pleurotomaria? kunda pik, 1926 was correctly referred to the genus Aldanella Vostokova, 1962 more than 30 years ago, although its affinities are still debated. It has been described by several authors as a gastropod on account of its helically coiled shell but it is here referred to the Class Helcionelloida, a group of Cambrian-Ordovician untorted molluscs which are usually bilaterally symmetrical. A sub-sutural, spiral muscle scar trace on the internal mould is described, as is a possible attachment area on the umbilical shoulder. Impressions of a prismatic shell structure are present in the apical region. In the lower Cambrian (proposed Cambrian Series 1) Kestla Member of the Lontova Formation, Aldanella kunda occurs together with Anabarella Vostokova, 1962, another helcionelloid that is also characteristic of Cambrian Series 1 in Siberia. Scenella(?) discinoides Schmidt, 1888 from the slightly younger Tiskre Formation (Cambrian Series 2) was originally assigned to a genus widely interpreted as a mollusc, but this species has been re-interpreted recently as a possible stem group brachiopod.
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| 17. |
- Lagebro, Linda, et al.
(författare)
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A new ?lamellipedian arthropod from the Early Cambrian Sirius Passet Fauna of North Greenland
- 2009
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Ingår i: Journal of Paleontology. - : Cambridge University Press (CUP). - 0022-3360 .- 1937-2337. ; 83:5, s. 820-825
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Tidskriftsartikel (refereegranskat)abstract
- The Non-Mineralized arthropod described herein is derived from the Sirius Passet fossil conservation deposit of North Greenland (82°47.6,N, 42°13.7ʹW), the oldest locality with exceptional preservation of soft tissues known from the Cambrian of Laurentia (Cambrian Series 2, Stage 3;NevadellaZone). As such, it is broadly contemporaneous with the Chengjiang fauna of China (Hou et al., 2004) and some 10 million years older than the Burgess Shale fauna of British Columbia. The Sirius Passet fauna was first documented by Conway Morris et al. (1987) and its geological setting is discussed by Babcock and Peel (2007). In addition to the nevadiid trilobiteBuenellus higginsiBlaker, 1988, the fauna is dominated by non-mineralized arthropods (Budd, 1993, 1995, 1997, 1999; Williams et al., 1996; Taylor, 2002). Other finds include sponges (Rigby, 1986), a lobopod (Budd and Peel, 1998), the earliest annelids (Conway Morris and Peel, 2008) and articulated halkieriids (Conway Morris and Peel, 1990, 1995), but most of the assemblage awaits description.
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| 18. |
- Larsson, Cecilia M., et al.
(författare)
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Trachyplax arctica, a new multiplated probelematic fossil from the lower Cambrian of North Greenland
- 2009
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Ingår i: Acta Palaeontologica Polonica. - : Polska Akademia Nauk Instytut Paleobiologii (Institute of Paleobiology, Polish Academy of Sciences). - 0567-7920 .- 1732-2421. ; 54:3, s. 513-523
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Tidskriftsartikel (refereegranskat)abstract
- A new scleritome-bearing organism with eight sclerite types, Trachyplax arctica gen. et sp. nov., is described from the lower Cambrian Paralledal Formation of North Greenland. The originally calcareous sclerites are now silicified; no microstructures are preserved. The dominant sclerite type (A; maximum dimension 19.3 mm) is bilaterally symmetrical, strongly arched, with an oval shield showing co-marginal growth lines and a projecting rostrum with prominent radial ornamentation. A similar sclerite morphology can be identified in Silurian-Carboniferous multiplacophoran molluscs but the remaining sclerite types, which also display a combination of concentric and radial ornamentation, find no clear equivalents. Two models for scleritome reconstruction are presented, based on the relative abundance of the sclerites, but neither promotes a satisfactory assignment to a higher taxon. Despite the morphological dissimilarities, possibly reflecting the age discrepancy, reference to the Multiplacophora is most attractive and entails a substantial extension of the known geological range of that group.
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| 19. |
- Lerosey-Aubril, Rudy, et al.
(författare)
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Gut Evolution In Early Cambrian Trilobites And The Origin Of Predation On Infaunal Macroinvertebrates : Evidence From Muscle Scars In Mesolenellus
- 2018
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Ingår i: Palaeontology. - : Wiley. - 0031-0239 .- 1475-4983. ; 61:5, s. 747-760
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Tidskriftsartikel (refereegranskat)abstract
- Trilobites are particularly common Cambrian fossils, but their trophic impact on the rapidly evolving marine ecosystems of that time is difficult to assess, due to uncertainties on how diverse their feeding habits truly were. Gut anatomy might help to constrain inferences on trilobite feeding ecology, but preservation of digestive organs is exceedingly rare. Muscle scars on the glabella, known as 'frontal auxiliary impressions' (FAIs), have been interpreted as evidence of the evolution of a pouch-like organ with powerful extrinsic muscles (i.e. a crop) in some trilobites. Here we describe FAIs in Mesolenellus hyperboreus from Cambrian Stage 4 strata of North Greenland, which represents the oldest example of such structures and their first report in the Suborder Olenellina. Mesolenellus FAIs suggest that the crop in trilobites was clearly differentiated from the rest of the digestive tract, and essentially located under a hypertrophied glabellar frontal lobe. Reviews of the digestive anatomy of trilobite sister-taxa and the glabellar morphology of the oldest-known trilobites suggest that the gut of the trilobite ancestor was an essentially simple tract (i.e. no well-differentiated crop) flanked laterally by numerous midgut glands. A crop first evolved in the Cambrian in groups like olenelloids and (later) paradoxidoids. Using ichnological evidence, we hypothesize that the emergence of olenelloids yields evidence for the evolution of predatory inclinations in a group of arthropods originally dominated by surfacedeposit-feeders. By allowing the exploitation of a rapidly developing food source, infaunal animals, the diversification of feeding strategies in trilobites might partially explain their unparalleled evolutionary success.
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| 20. |
- Lindström, Anna, et al.
(författare)
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Repaired injuries and shell form in some Palaeozoic pleurotomarioid gastropods
- 2005
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Ingår i: Acta Palaeontologica Polonica. - 0567-7920 .- 1732-2421. ; 50:4, s. 697-704
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Tidskriftsartikel (refereegranskat)abstract
- Pleurotomarioid gastropods typically develop a spiral band called the selenizone in the outer whorl face of the shell that is formed by the closure of an open slit in the apertural margin. The slit and selenizone may be important in controlling the extent to which fractures induced by predatory attacks propagate across the whorl surface. A prominent selenizone can prevent fractures from traversing the entire whorl. Study of six Palaeozoic pleurotomarioid gastropod species with repaired shell injuries shows that repaired injuries are dependent on both the nature of the selenizone and shell form. The species can be divided into three morphological groups (turbiniform, trochiform and planispiral) and show a variety of selenizones with different degrees of prominence. Turbiniform shells show more repaired injuries than planispiral forms, indicating that species in the former group more often survive predatory attacks. The studied material is too sparse for meaningful statistical analysis, but individual case studies suggest that the combined influence of shell form and the nature of the selenizone can make the interpretation complex.
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| 21. |
- MORRIS, SC, et al.
(författare)
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ARTICULATED HALKIERIIDS FROM THE LOWER CAMBRIAN OF NORTH GREENLAND AND THEIR ROLE IN EARLY PROTOSTOME EVOLUTION
- 1995
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Ingår i: PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY OF LONDON SERIES B-BIOLOGICAL SCIENCES. - 0962-8436. ; 347:1321, s. 305-358
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Articulated halkieriids of Halkieria evangelista sp, nov. are described from the Sirius Passet fauna in the Lower Cambrian Buen Formation of Peary Land, North Greenland. Three zones of sclerites are recognizable: obliquely inclined rows of dorsal palmates
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| 22. |
- Morris, Simon Conway, et al.
(författare)
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A New Helcionelloid Mollusk from the Middle Cambrian Burgess Shale, Canada
- 2013
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Ingår i: Journal of Paleontology. - : Cambridge University Press (CUP). - 0022-3360 .- 1937-2337. ; 87:6, s. 1067-1070
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Tidskriftsartikel (refereegranskat)abstract
- Burgess Shale-type faunas provide unique insights into the Cambrian "explosion". Their degree of representativeness of Cambrian marine life in general is, however, less easy to establish. One line of evidence is to consider only the skeletal component of a Burgess Shale-type fauna and compare that with a typical Cambrian assemblage. This paper describes a new species of helcionelloid mollusk (Totoralia reticulata n. sp.) from the middle Cambrian Burgess Shale of British Columbia. Whilst much rarer than the co-occurring smooth shelled helcionelloid Scenella amii, the strongly costate morphology of Totoralia reinforces comparisons with Cambrian shelly faunas. The extension of the range of Totoralia from Argentina to Canada adds support to the proposed derivation of the Precordillera terrane of Mendoza from Laurentia.
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| 23. |
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| 24. |
- Peel, John Stuart, et al.
(författare)
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A new arthropod from the lower Cambrian Sirius Passet Fossil-Lagerstätte of North Greenland
- 2009
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Ingår i: Bulletin of Geosciences. - : Czech Geological Survey. - 1214-1119 .- 1802-8225. ; 84:4, s. 625-630
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Tidskriftsartikel (refereegranskat)abstract
- Aaveqaspis inesoni gen. et sp. nov., is described from the lower Cambrian Sirius Passet Fossil-Lagerstatte of Peary Land, North Greenland. It has a semicircular head shield and a thorax with 5 tergites. The tail shield carries 2 pairs of spines, the most anterior of which is enormous and dominates the trunk. A. inesoni lacks any preserved trace of eyes, as is also the case with several other Sirius Passet arthropods, suggesting that the fossils accumulated in deeper water than the contemporaneous Chengjiang Fossil-Lagerstatte of China or the middle Cambrian Burgess Shale assemblages of British Columbia.
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| 25. |
- Peel, John Stuart
(författare)
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A new look at Pleurotomaria perlata Hall, 1852 (Gastropoda) from the Silurian of Laurentia
- 2018
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Ingår i: GFF. - : TAYLOR & FRANCIS LTD. - 1103-5897 .- 2000-0863. ; 140:3, s. 249-253
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Tidskriftsartikel (refereegranskat)abstract
- New material from Genoa, Ohio, USA, of the distinctive but poorly known Silurian gastropod Pleurotomaria perlata Hall, 1852, originally described from the Guelph Formation of Ontario, Canada, demonstrates that it is not a pleurotomariinid vetigastropod. It is a species of Isfarispira Gubanov, Peel & Pianovskaya, 1995, first described from the Silurian of Kyrgyzstan, central Asia, and now recognised from Laurentia. Isfarispira belongs within a pycnomphaline-omphalotrochid group of euomphaloidean gastropods but this group is too poorly understood to allow firm placement at this time.
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| 26. |
- Peel, John Stuart, et al.
(författare)
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A new middle Cambrian bradoriid arthropod from Greenland and western Canada
- 2015
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Ingår i: Journal of Paleontology. - : Cambridge University Press (CUP). - 0022-3360 .- 1937-2337. ; 89:1, s. 96-102
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Tidskriftsartikel (refereegranskat)abstract
- Circum-Laurentian middle Cambrian (Cambrian Series 3) deposits in Greenland and British Columbia yield a new hipponicharionid bradoriid arthropod, Flumenoglacies n. gen., characterized by a comarginal, ramp-like structure which is crested by a continuous lobe. The narrow lobe is the result of the medial fusion of anterior and posterior lobes, seemingly a recurrent theme in hipponicharionid evolution. The type species, F. groenlandica n. sp., is described from the Ekspedition Brae Formation (Drumian Stage) of Peary Land but the description of two unnamed species from slightly older middle Cambrian strata of the Stephen Formation of British Columbia provides additional evidence for the wide distribution of Small Shelly Faunas during the Cambrian.
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| 27. |
- Peel, John Stuart
(författare)
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A phosphatised fossil Lagerstätte from the middle Cambrian (Wuliuan Stage) of North Greenland (Laurentia)
- 2023
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Ingår i: Bulletin of the Geological Society of Denmark. - : Dansk Geologisk Forening. - 0011-6297 .- 2245-7070. ; 72, s. 101-122
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Tidskriftsartikel (refereegranskat)abstract
- The upper Henson Gletscher Formation (Cambrian, Miaolingian Series, Wuliuan Stage) of southern Lauge Koch Land and Londal, south-western Peary Land, North Greenland (Laurentia) yields diverse assemblages of phosphatised Small Shelly Fossils after treatment with weak acetic acid. The occurrence merits description as a fossil Lagerstatte on account of the exceptional preservation of soft parts in some specimens, although the phosphatisation itself is generally rather coarse. Bradoriid and phosphatocopid arthropods are common and display substantial variation in their preservational history. Some specimens retain traces of internal morphology, although details are generally obscured by indifferent preservation. Rare specimens extend the range of stem-group pentastomid arthropods back by more than 10 million years. A unique hatching larva demonstrates the same early developmental stage of a stem-group priapulan worm to that described in some present-day priapulans. The preservation of an in place operculum has demonstrated that the widespread, sup-posed mollusc Protowenella is actually an unusual, strongly coiled hyolith. Abundant coprolites and cololites provide additional evidence of early phosphatisation. In terms of morphology, Cambrocoryne lagenamorpha gen. et sp. nov. superficially resembles wiwaxiid and some annelid sclerites, thelodont scales and the foraminiferan Lagena, but its true identity is obscure.
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| 28. |
- Peel, John Stuart
(författare)
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A problematic cnidarian (Cambroctoconus; Octocorallia?) from the Cambrian (Series 2-3) of Laurentia
- 2017
-
Ingår i: Journal of Paleontology. - : Cambridge University Press (CUP). - 0022-3360 .- 1937-2337. ; 91:5, s. 871-882
-
Forskningsöversikt (refereegranskat)abstract
- The problematic calcified cnidarian Cambroctoconus is described from the Henson Gletscher Formation (Cambrian Series 2, Stage 4-Series 3, Stage 5) of North Greenland, representing the first record from Laurentia of a genus otherwise recently described from China, Kyrgyzstan, and Korea. Internal molds produced by penetrative phosphatization mirror the pervasive pore system of the calice walls and septa. The pore system is compared to the network of gastrodermal solenia that distributes nutrients between polyps and surrounding stolon tissues in present day octocorals. In conjunction with the octagonal form of the individual coralla and eight-fold symmetry of septa, the pore system promotes assignment of Cambroctoconus to the Octocorallia, a basal clade in cnidarian phylogeny. Octocorals ('soft corals') are diverse in present day seas, but have a poor fossil record despite the general development of distinctive calcareous spicules. New taxa: Order Cambroctoconida new; Cambroctoconus koori new species.
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| 29. |
- Peel, John Stuart
(författare)
-
An epiphytacean-Girvanella (Cyanobacteria) symbiosis from the Cambrian (Series 3; Drumian) of North Greenland (Laurentia)
- 2018
-
Ingår i: Bulletin of Geosciences. - : CZECH GEOLOGICAL SURVEY. - 1214-1119 .- 1802-8225. ; 93:3, s. 327-336
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Tidskriftsartikel (refereegranskat)abstract
- The widespread Cambrian calcareous cyanobacterium Girvanella is described in symbiotic association with a new epiphytacean, Orpikania freucheni gen. et sp. nov. (Microproblematica), from the Ekspedition Bra; Formation (Cambrian Series 3, Drumian Stage) of Freuchen Land, North Greenland. The phosphatized assemblages preserve dendrites of the epiphytacean forming a supporting framework for discrete climbing filaments of Girvanella lianifiomis sp. nov. that are firmly attached to their host with holdfasts. Elevation of the slender Girvanella filaments on the framework of the dendrite potentially enhanced their phototactic movement towards the light. Filaments in the co-occurring Girvanella pituutaq sp. nov. are regularly twisted together into a nape-like form which may have assisted elevation above its substrate.
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| 30. |
- Peel, John Stuart
(författare)
-
Anatase and Hadimopanella selection by Salterella from the Kap Troedsson formation (Cambrian Series 2) of North Greenland
- 2017
-
Ingår i: GFF. - : Informa UK Limited. - 1103-5897 .- 2000-0863. ; 139:1, s. 70-74
-
Tidskriftsartikel (refereegranskat)abstract
- Shells of the agmatan Salterella from the Kap Troedsson Formation (Cambrian Series 2) of North Greenland are filled with cemented grains of authigenic anatase (TiO2) associated with the palaeoscolecidan sclerite Hadimopanella apicata. Selection of the heavy grains, both recognized for the first time in Salterella, added ballast to an organism which was probably motile and lived by selective deposit feeding.
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| 31. |
- Peel, John Stuart
(författare)
-
Biogenic and abiogenic injuries in a Carboniferous Bellerophon (Gastropoda) from the Isle of Man, United Kingdom
- 2020
-
Ingår i: GFF. - : Informa UK Limited. - 1103-5897 .- 2000-0863. ; 142:1, s. 81-86
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Tidskriftsartikel (refereegranskat)abstract
- Two described specimens of the gastropod Bellerophon tenuifascia J. de C. Sowerby, 1824, from the Carboniferous (Asbian) of the Isle of Man, United Kingdom, preserve repaired injuries resulting from environmental breakage and failed, non-lethal, predatory attacks. Deep scars attributed to predatory attacks are assigned to the ichnofossil Caedichnus and were focused on the mid-dorsal area of the aperture. Abundant small-scale scallops and chipping of growth lamellae distributed around the apertural margin are mainly the result of environmental damage. A deeply incised injury in the aperture of one specimen was probably a fatal injury.
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| 32. |
- Peel, John Stuart
(författare)
-
Bobellis oliveri gen. et sp. nov. from the Silurian of North Greenland (Laurentia) and the systematic position of pycnomphaline gastropods
- 2019
-
Ingår i: Bulletin of Geosciences. - : CZECH GEOLOGICAL SURVEY. - 1214-1119 .- 1802-8225. ; 94:2, s. 125-136
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Tidskriftsartikel (refereegranskat)abstract
- The gastropod Bobellis oliveri gen. et sp. nov. is described from carbonate mounds of the Samuelsen Hoj Formation (early Silurian) within the Washington Land Group of North Greenland (Laurentia). It displays a profound adapertural swing of the growth lines across the upper whorl surface in the multi-whorled trochiform shell; the umbilicus is closed by a prominent funicle. Bobellis oliveri is assigned to the Family Pycnomphalidae (Ordovician-Devonian; nom. transl. Subfamily Pycnomphalinae Peel, 1984) which is transferred to the Euomphaloidea, alongside the morphologically similar Omphalotrochidae (Devonian-Permian). In pycnomphalids the umbilicus is usually partially or completely closed by a prominent circumbilical funicle while the umbilicus of omphalotrochids is generally open.
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| 33. |
- Peel, John Stuart
(författare)
-
Bromalites from the Cambrian (Series 2 and 3) of North Greenland
- 2015
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Ingår i: GFF. - Uppsala Univ, Dept Earth Sci Palaeobiol, SE-75236 Uppsala, Sweden. : Informa UK Limited. - 1103-5897 .- 2000-0863. ; 137:3, s. 181-194
-
Tidskriftsartikel (refereegranskat)abstract
- Six assemblages of phosphatized bromalites from the Cambrian (Series 2 and 3) of North Greenland provide added insight into community structure in fossil assemblages otherwise dominated by microscopic skeletonized organisms. The bromalites, picked from acetic acid residues, display a wide range of morphologies, including pellets, segmented rods, wrinkled, smooth and segmented convoluted strings. Most are interpreted as extruded faecal material (coprolites) but moulds from the digestive tract (cololites) are also recognized. Most of the coprolites probably were produced by deposit-feeding invertebrates but rare specimens dominated by carapace fragments of bradoriid? arthropods are coprolites from predators. Zigzag-folded bromalites are interpreted as cololites of orthothecid hyoliths and are also recognized in inequivalent strata in China. Longitudinally wrinkled forms may be cololites of unknown origin. Minute spheres (Arenigiapella) forming one coprolite are interpreted as microcrystalline phosphatic coatings of bacteria. Post-diagenetic boring attributed to endolithic cyanobacteria is widespread.
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| 34. |
- Peel, John Stuart, et al.
(författare)
-
Cavity-dwelling microorganisms from the Ediacaran and Cambrian of North Greenland (Laurentia)
- 2022
-
Ingår i: Journal of Paleontology. - : Cambridge University Press. - 0022-3360 .- 1937-2337. ; 96:2, s. 243-255
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Tidskriftsartikel (refereegranskat)abstract
- Records of diagenetically mineralized, filamentous, cavity-dwelling microorganisms extend back to strata from the early Paleoproterozoic (2400 Ma). In North Greenland (Laurentia), they are first known from the Ediacaran (Neoproterozoic; ca. 600 Ma) Portfjeld Formation of southern Peary Land, in association with a biota similar to that of the Doushantuo Formation of China. The Portfjeld Formation cavity dwellers are compared with more widespread occurrences in Cambrian (Series 2, Stage 4, Miaolingian Series) strata from the same region in which assemblages in postmortal shelter structures within articulated acrotretoid brachiopods and other invertebrates are common. All specimens were recovered by digestion of carbonate samples in weak acids. The described fossils are preserved as mineral encrusted threads but this diagenetic phosphatization unfortunately obscures their biological identity.
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| 35. |
- Peel, John Stuart
(författare)
-
Eldoradia and Acrocephalops (Trilobita: Bolaspididae) from the middle Cambrian (Miaolingian) of northern Greenland (Laurentia)
- 2021
-
Ingår i: GFF. - : Taylor & Francis. - 1103-5897 .- 2000-0863. ; 143:1, s. 8-15
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Tidskriftsartikel (refereegranskat)abstract
- The ptychoparioid trilobites Eldoradia and Acrocephalops (Family Bolaspididae) are described from the middle Cambrian (Miaolingian Series) of northern Greenland (Laurentia). Eldoradia, originally described from the Secret Canyon Shale of Nevada, is recorded from south-western Wulff Land, North Greenland, where it occurs together with Modocia and Olenoides. Eldoradia caerulioris n. sp. is established. The occurrence of Eldoradia in the lower part of the Blue Cliffs Formation indicates a minimum late middle Cambrian age (Miaolingian Series, Guzhangian Stage) for the base of the formation. Type material of Acrocephalops, a relative of Eldoradia originally proposed on the basis of material from the Miaolingian Series (Wuliuan Stage) of Inglefield Land, North-West Greenland, is redescribed.
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| 36. |
- Peel, John Stuart, et al.
(författare)
-
EOBUCANIA (Mollusca) from the Furongian (late Cambrian) of Sweden
- 2007
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Ingår i: GFF. - 1103-5897 .- 2000-0863. ; 129:Part 3, s. 235-237
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Tidskriftsartikel (refereegranskat)abstract
- The isometrically coiled mollusc Eobucania Kobayashi, 1955 is described from the Peltura scarabaeoides Zone (Furongian; late Cambrian) of Kinnekulle, southern Sweden, representing the oldest record of the genus and the first from the Cambrian of Sweden. While originally described from the Lower Ordovician strata within the McKay Group of British Columbia, Canada, additional species of Eobucania have been reported from the Lower Ordovician of Mexico, France and the Czech Republic, and ostensibly from the Lower Devonian of China. Eobucania has been widely interpreted as a bellerophontoidean gastropod, but placement within the monoplacophoran Class Tergomya is possible.
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| 37. |
- Peel, John Stuart
(författare)
-
Failed predation, commensalism and parasitism on lower Cambrian linguliformean brachiopods
- 2015
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Ingår i: Alcheringa. - : Informa UK Limited. - 0311-5518 .- 1752-0754. ; 39:2, s. 149-163
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Forskningsöversikt (refereegranskat)abstract
- Disarticulated valves of the linguliformean brachiopod Botsfordia from the early Cambrian (Cambrian Series 2, Stage 4) Kap Troedsson Formation of North Greenland preserve repaired injuries resulting from failed predatory attacks. Durophagous strategies include peeling and crushing of the shells; rare borings also occur. Premortem commensal epibionts etched circular attachment scars on the shell exterior near the margins. Parasitic epibionts attached inside the commissure produced globose callosities and V-shaped invaginations in the growing margin. Comparison with epibiont-bearing assemblages of the brachiopod Diandongia from the Chengjiang and Guanshan Lagerstatten of China promotes recognition of a widely distributed Botsfordiid Community in soft-bottom environments during the early Cambrian.
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| 38. |
- Peel, John Stuart
(författare)
-
Feeding behaviour of a new worm (Priapulida) from the Sirius Passet Lagerstatte (Cambrian series 2, stage 3) of North Greenland (Laurentia)
- 2017
-
Ingår i: Palaeontology. - : WILEY. - 0031-0239 .- 1475-4983. ; 60:6, s. 795-805
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Tidskriftsartikel (refereegranskat)abstract
- Singuuriqia simoni gen. et sp. nov. represents the first record of a priapulid worm from the Sirius Passet Lagerstatte (Cambrian Series 2, Stage 3) of North Greenland (Laurentia). It is defined by an unusually broad, longitudinally folded, foregut which tapers through the pharynx towards the anterior mouth; posteriorly, the same longitudinal folding is evident in the narrow gut. The slender, smooth, trunk in the unique specimen passes anteriorly into an oval proboscis which culminates in a smooth, extensible, pharynx with pharyngeal teeth. The capacity for substantial expansion of the foregut permitted rapid ingestion of food prior to digestion at leisure. Cololites suggest both carnivorous and deposit feeding behaviour, indicating that Singuuriqia, like the present day Priapulus, was probably omnivorous.
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| 39. |
- Peel, John Stuart
(författare)
-
Holdfasts of Sphenothallus (Cnidaria) from the early Silurian of western North Greenland (Laurentia)
- 2021
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Ingår i: GFF. - : Taylor & Francis. - 1103-5897 .- 2000-0863. ; 143:4, s. 384-389
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Tidskriftsartikel (refereegranskat)abstract
- Well-preserved holdfasts and early growth stages of the tubular cnidarian Sphenothallus are described from the early Silurian (Llandovery Series) of Washington Land, North Greenland. The diameter of the holdfast is determined by the formation of a basal disc attached to the substrate, upon which the initially conical, but subsequently tubular shell is formed. The characteristic opposing longitudinal thickenings are developed at each angular margin as the initially circular tube acquires an elliptical form.
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| 40. |
- Peel, John Stuart, et al.
(författare)
-
Hyoliths from the Bystraya Formation (Cambrian Series 2) of eastern Transbaikalia (Zabaykalsky Krai), Siberia
- 2022
-
Ingår i: Alcheringa. - : Taylor & Francis Group. - 0311-5518 .- 1752-0754. ; 46:2, s. 129-146
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Tidskriftsartikel (refereegranskat)abstract
- The hyolith fauna of the middle Bystraya Formation (Cambrian Series 2) of eastern Transbaikalia (Zabaykalsky Krai), Siberia, includes at least 17 described taxa distributed between the orders Hyolithida and Orthothecida. Species of Microcornus, Parkula, Conotheca, Neogloborilus and Cupitheca are widely reported from Cambrian strata elsewhere. Triplicatella uslonica sp. nov. is known only from Transbaikalia. Dauritheca is proposed as a replacement generic name for the junior homonym Pachytheca, originally described from Xinjiang, China, and its range is extended to Transbaikalia. A conch with prominent comarginal ribs is referred to Salanytheca daurica sp. nov., a genus otherwise known from the early Cambrian of Mongolia and northern Siberia.
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| 41. |
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| 42. |
- Peel, John Stuart, et al.
(författare)
-
Lower Cambrian (Series 2) small shelly fossils from along Nares Strait (Nunavut and Greenland; Laurentia)
- 2021
-
Ingår i: Canadian journal of earth sciences (Print). - : Canadian Science Publishing. - 0008-4077 .- 1480-3313. ; , s. 495-504
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Tidskriftsartikel (refereegranskat)abstract
- Three small assemblages of lower Cambrian (Cambrian Series 2, Stage 4) small shelly fossils are described from Laurentian strata astride Nares Strait. The fauna from the Humboldt Formation of Daugaard-Jensen Land, North Greenland, is derived from inner shelf sediments deposited on the stable craton of the Inglefield Land High. Fossils from Judge Daly Promontory, eastern Ellesmere Island, Nunavut, occur in strata of the Cambrian Ellesmere Group (Kane Basin Formation) that have been structurally juxtaposed against older strata; they were originally assigned to the Kennedy Channel Formation, which is now considered to be of Neoproterozoic age. A similar fauna from offshore environments of the Aftenstjernesø Formation in northern Nyeboe Land, North Greenland, reflects the regional structural and sedimentological continuity with the Canadian Cambrian succession. Pojetaia robsonae sp. nov. is described from Judge Daly Promontory.
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| 43. |
- Peel, John Stuart, et al.
(författare)
-
Middle Cambrian (Miaolingian Series, Wuliuan Stage) molluscs and mollusc-like microfossils from North Greenland (Laurentia)
- 2022
-
Ingår i: Bulletin of the Geological Society of Denmark. - : Geological Society of Denmark. - 0011-6297 .- 2245-7070. ; 70, s. 69-104
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Tidskriftsartikel (refereegranskat)abstract
- Diverse assemblages of helcionelloid molluscs and mollusc-like microfossils are described from the upper Henson Gletscher Formation (Cambrian, Miaolingian Se-ries, Wuliuan Stage) of Lauge Koch Land and western Peary Land, North Greenland (Laurentia). The fauna compares closely to an assemblage of similar age from the Coonigan Formation of Australia, although the latter is preserved as silica replicas while the North Greenland fossils are dominantly preserved as phosphatized internal moulds. These internal moulds often retain a detailed impression of the inner surface of the shell, with a fine pitted texture typically present. Prominent deep grooves on the sub-apical surface in the erect helcionellids Dorispira and Erugoconus, correspond-ing to ridges on the shell interior, seem to be associated with control of water flow through the mantle cavity. Well-developed shell pores, preserved as tubercles on the internal mould, are common in species of the laterally compressed Mellopegma. New taxa: Dorispira avannga sp. nov., Dorispira septentrionalis sp. nov., Dorispira tavsenensis sp. nov., Dorispira tippik sp. nov., Erugoconus acuminatus gen. et sp. nov., Scenella? siku sp. nov., Sermeqiconus gen. nov., Tavseniconus erectus gen. et sp. nov., Vendrascospira troelseni gen. et sp. nov., Vendrascospira frykmani gen. et sp. nov.
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| 44. |
- Peel, John Stuart
(författare)
-
Middle Cambrian trilobites (Miaolingian, Ehmaniella Biozone) from the Telt Bugt Formation of Daugaard-Jensen Land, western North Greenland
- 2020
-
Ingår i: Bulletin of the Geological Society of Denmark. - : GEOLOGICAL SOC DENMARK. - 0011-6297 .- 2245-7070. ; 68, s. 1-14
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Tidskriftsartikel (refereegranskat)abstract
- A small fauna of middle Cambrian trilobites is described from the upper Telt Bugt Formation of Daugaard-Jensen Land, western North Greenland, and the formation is formally defined. Blainiopsis holtedahli and Blainiopsis benthami, originally described from the equivalent Cape Wood Formation of Bache Peninsula, Nunavut, Canada, are documented in an assemblage assigned to the Ehmaniella Biozone (Topazan Stage of North American usage), Miaolingian Series, Wulivan Stage, of the international standard. Two new species are proposed: Ehmaniella sermersuagensis and Clappaspis tupeq.
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| 45. |
- Peel, John Stuart
(författare)
-
Molaria (Euarthropoda) from the Sirius Passet Lagerstatte (Cambrian Series 2, Stage 3) of North Greenland
- 2017
-
Ingår i: Bulletin of Geosciences. - : Czech Geological Survey. - 1214-1119 .- 1802-8225. ; 92:2, s. 133-142
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Tidskriftsartikel (refereegranskat)abstract
- A second species of the characteristic Burgess Shale euarthropod Molaria Walcott, 1912 is described from the Sirius Passet Lagerstatte of North Greenland, thus extending its range from Cambrian Series 3 (Stage 5) back into Series 2 ( Stage 3). Molaria steini sp. nov. differs from the type species, M. spinifera Walcott, 1912, in having 9 trunk tergites and lacking an elongate connecting segment between the trunk and the jointed telson. Exopod setal fringes are similar to those in the artiopod Emeraldella Walcott, 1912 from the Burgess Shale but other details of limbs remain obscure.
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| 46. |
- Peel, John Stuart, et al.
(författare)
-
Morphology and ecology of the bradoriid arthropods Spinospitella and Nikolarites from the Cambrian (Series 2, Stage 4) of North Greenland (Laurentia)
- 2021
-
Ingår i: Palaeontologische Zeitschrift. - : Springer Science and Business Media LLC. - 0031-0220 .- 1867-6812. ; 95, s. 413-427
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Tidskriftsartikel (refereegranskat)abstract
- Tuberculate fragments referred to Nikolarites spasskyi are compared with a complete carapace and other material of Spinospitella from Cambrian Series 2, Stage 4 in North Greenland. The descriptions expand earlier brief records from Laurentia of the two bradoriids, originally described from Siberia and Australia, respectively. The mutually exclusive occurrences of the two taxa indicate ecological control of their distribution in North Greenland. Robust fragments of Nikolarites spasskyi occur in reworked higher energy deposits of the Aftenstjernesø Formation, while thin-walled carapaces of Spinospitella characterise deeper water mudstones within the Buen and Aftenstjernesø formations.
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| 47. |
- Peel, John Stuart, et al.
(författare)
-
Muscle attachment scars in helcionelloids from Denmark cast light on mollusc evolution in the Cambrian
- 2023
-
Ingår i: Acta Palaeontologica Polonica. - : Polska Akademia Nauk Instytut Paleobiologii (Institute of Paleobiology, Polish Academy of Sciences). - 0567-7920 .- 1732-2421. ; 68:4, s. 625-638
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Tidskriftsartikel (refereegranskat)abstract
- Multiple, small (diameter <20 μm) swellings on the apex of internal moulds of the laterally compressed helcionelloids Eotebenna viviannae and the new species Eotebenna danica from the middle Cambrian (Miaolingian) of Bornholm, Denmark, are interpreted as a muscle attachment scars. The scar pattern is unique amongst currently known helcionelloids both in the abundance of attachment sites and in crossing the median plane of symmetry on the supra-apical (dorsal) surface. Sites of typically two pairs of dorsal muscle scars in other helcionelloids are distributed symmetrically on the dorso-lateral areas. The recognition of four groups of muscle scar patterns in helcionelloids suggests a degree of anatomical diversity within the group that is obscured by the morphological simplicity of the enclosing cap-shaped shells, although evolutionary links to mollusc crown groups are unresolved. In addition to the muscle scars, traces of shell micro-structure are described.
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| 48. |
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| 49. |
- Peel, John Stuart
(författare)
-
Muscle scars in euomphaline gastropods from the Ordovician of Baltica
- 2019
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Ingår i: Estonian journal of earth sciences. - : ESTONIAN ACAD PUBLISHERS. - 1736-4728 .- 1736-7557. ; 68:2, s. 88-100
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Tidskriftsartikel (refereegranskat)abstract
- A discrete pair of muscle scars is described for the first time on the umbilical wall of the open-coiled, hyperstrophic ophiletoidean gastropod Asgardispira, a close relative of the widely distributed Lytospira, from the middle Ordovician of the eastern Baltica. In a unique specimen of the euomphaloidean Lesueurilla of similar age and derivation, the muscles have coalesced into a single scar. A pair of pedal retractor muscles is characteristic of several major groups of gastropods both in the Lower Palaeozoic and at the present day, and was likely an ancestral character of the class. The consolidation of muscle attachment to a single site may reflect the tightening of the logarithmic spiral of the shell and is probably related to the increasing development of anisostrophic coiling and shell re-orientation during gastropod evolution.
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| 50. |
- Peel, John Stuart
(författare)
-
Muscle scars, mode of life and systematics of Pollicina (Mollusca) from the Ordovician of Baltica
- 2020
-
Ingår i: Estonian journal of earth sciences. - : ESTONIAN ACAD PUBLISHERS. - 1736-4728 .- 1736-7557. ; 69:1, s. 20-36
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Tidskriftsartikel (refereegranskat)abstract
- Pollicina is a distinctive, but uncommon, univalved mollusc originally described from the Middle Ordovician (Darriwilian Stage) of the Baltic. The slender, bilaterally symmetrical shell expands slowly and is curved through up to about 90 degrees, but straightens in the latest growth stages. Pollicina corniculum, the type species from the St Petersburg region of Russia is redescribed, as is Pollicina crassitesta, the most common representative from the Tallinn area of Estonia. Muscle scars in P. crassitesta form a continuous circum-apertural band on internal moulds about half way between the apex and the apertural margin. The bilaterally symmetrical shell, orthocline aperture, circum-apertural muscle scar and frequent displacement of the apertural margin, as evidenced by dislocations in growth ornamentation, indicate that Pollicina lived as a limpet, clamped against the substrate. Suggestions that it was an open coiled gastropod lying on the sediment surface are rejected. As with most Ordovician limpet-formed shells, assignment of Pollicina to Tergomya or Gastropoda is equivocal, even controversial, not least on account of the tall shell and muscle band. Despite similarities with the tergomyan Cyrtolites, Pollicina is placed tentatively together with the archinacelloidean gastropods.
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