Arnaud Bignon | Universidad Nacional de Córdoba (original) (raw)
Papers by Arnaud Bignon
The Givetian platform of the Ardennes Massif records several alternations between a siliciclastic... more The Givetian platform of the Ardennes Massif records several alternations between a siliciclastic-carbonate ramp and a carbonate shelf. Usually these depositional contexts are considered as a major disruption implying a perturbation of many ecological parameters. We established the impact of these variations on the biodiversity structure through the study of the trophic organisation. Thanks to a previous microfacies analysis, 550 levels of the Mont d'Haurs section in Givet and ten associated environments were precisely defined. Seven palaeotrophic levels are recognized from micropalaeontological data, including benthic, planktonic, heterotroph and autotroph organisms. The spatial and temporal distributions of these levels have been analysed through means of multivariate analyses. The statistic results show that the distribution of the palaeotrophic levels during periods characterized by a mixed ramp is not significantly different than during carbonate shelf influences. These environmental modifications do not affect the community-type. These results support recent studies performed on different benthic communities occurring in the Givetian of the Ardennes Massif. Indeed, trilobite and ostracod faunas of this period appear more affected by global environmental changes as the Kačák (uppermost Eifelian) and Taghanic (late middle Givetian) events. Moreover, along the proximal-distal transect on the platform, the reef constitutes the most singular environment. However, contrary with the Frasnian reefs of the Ardennes Massif, which consist of carbonate mud mounds laying on a deep mixed ramp, there is no trilobite community that appears restricted to Givetian reefs. Thus global bioevents during the Middle Devonian have a more important control on the biodiversity than the platform morphology. These results support the view that at wide scales (spatial and temporal), the biodiversity responds more positively to ecological disturbances.
The palaeontological species concept – a rather subjective concept – is based on morphological cr... more The palaeontological species concept – a rather subjective concept – is based on morphological
criteria and carries a notion of time. The delimitation of a species among trilobites
does not break this rule and is based on morphological and ontogenetic features. Thus,
among phacopid trilobites, characters such as the visual complex and the vincular furrow
are diagnostic. Furthermore, quantitative studies of the morphological disparity and ontogenetic
trajectories allow us better to define the species and its variability, and to identify
the evolutionary patterns established in Phacopidae during 100Ma of existence.
Numerous exuviae of three Dechenella species (D. givetensis, D. ziegleri and D. calxensis) from t... more Numerous exuviae of three Dechenella species (D. givetensis, D. ziegleri and D. calxensis) from the
Middle Devonian (Givetian) of NE France (Ardenne Massif) provide the opportunity to identify the evolutionary
modifications of ontogeny of the three Dechenella species and to elaborate a conceptual framework of
developmental shape changes. First we used biometric and morphometric approaches to characterize shape
modifications. Then we computed ontogenetic trajectories by multivariate regression of geometric shape variables
on centroid size in order to compare them. Finally, we compared parallelism between trajectories and rates of
development relative to size. These analyses demonstrate a significant difference in the cranidial developmental
trajectories of D. givetensis and D. ziegleri indicating an allometric repatterning. However, pygidia of these species
share the same allometric pattern with a distinct developmental rate suggesting that heterochrony could be a partial
explanation for the body shape evolution. Pygidial ontogeny of D. calxensis corresponds to an allometric
repatterning with respect to both other species. This work illustrates the complexity of evolutionary modifications of
ontogeny constituting an important process in morphological novelties.
Recent investigation of the historical Mont d’Haurs section near Givet yielded numerous trilobite... more Recent investigation of the historical Mont d’Haurs section near Givet yielded
numerous trilobites from Middle Devonian carbonate deposits. The trilobite fauna described in the
present paper comprises a number of taxa from the basal Givetian, including two new ones:
Dechenella givetensis sp. n.; Dechenella calxensis sp. n.; Dechenella ziegleri Struve, 1992; Goldius cf.
capitellum (Archinal, 1994); and Nyterops cf. hollandi van Viersen, 2007a. This fauna confirms the
previously recognised taxonomic diversity pattern and the Dechenella and Nyterops Association
from the middle Middle Devonian in the Ardenne area.
Traditionally, the evolutionary scenarios of Asteropyginae have been organized in two major clade... more Traditionally, the evolutionary scenarios of Asteropyginae have been organized in two major clades involving four pygidial
patterns. The first cladistic analysis performed on the subfamily maintained the organization in two clades, though the
phylogenetic relationships between genera were unexpected compared to the traditional scenarios. Moreover, the previous
systematic scheme based on pygidial segmentation was rendered obsolete. In this study, we performed a new phylogenetic
analysis from well-known taxa and recent discoveries. Sixty species assigned to 36 genera have been analysed from a
dataset of 72 characters. Three more species are used as the outgroup. The 79 most parsimonious trees have a length of
492 steps and a retention index of 0.735. Our analysis confirms the monophyly of Asteropyginae excluding the genus
Protacanthina. The phylogenetic pattern is unconventional in that a largely pectinate topology is resolved, rather than two
clades corresponding to formerly delimited pygidial morphs. Nevertheless, most relationships between genera suggested in
the traditional evolutionary scenarios of the subfamily have been recovered, the main differences being the origin of the
group. Whereas Treveropyge was usually considered as the origin of the remaining Asteropyginae, the present results instead
identify Destombesina as the sister group to all remaining members of the subfamily. From the new phylogenetic pattern,
the diagnoses of genera are rewritten in a standard way and to delimit clades more accurately. This work implies modified
generic assignments for some species and the erection of four new genera: Minicryphaeus gen. nov., Gandlops gen. nov.,
Morzadecops gen. nov. and Pennarbedops gen. nov. The systematic position of Erbenochile is also discussed, the genus no
longer being assigned to Asteropyginae.
Acta Palaeontologica Polonica, 60 (4), 949-962
During the Devonian the sedimentation on the continental shelves of Ardenne Massif and Boulonnais... more During the Devonian the sedimentation on the continental shelves of Ardenne Massif and Boulonnais has changed from a mixed siliciclastic-carbonate ramp (Eifelian), through a carbonate barrier reef (Givetian) and then to a detritic influx with local mud-mounds (Frasnian). Here we analysed the faunistic dynamics of the trilobite associations through the changing environment. We used multivariate analyses (clustering and ordering) to discriminate the trilobite associations within 67 different samples. Three previously known communities and one new were recognised: the Eifelian Mixed association, the Givetian Dechenella association and the two Frasnian Bradocryphaeus and Scutellum-Goldius associations. These trilobite faunas present a progressive ecological specialisation. The Mixed association occurs both in the ramp or carbonated (local reef developed on the ramp) facies without any significant difference in its composition. The Dechenella fauna occurs preferentially close to barrier reefs, but can also survive during short periods of detrital input. The two Frasnian communities show a strong relationship with their environment. The Scutellum-Goldius association is only found in reef systems, whereas the Bradocryphaeus flourishes exclusively in lateral facies.
Geobios, Nov 2014
A recent cladistic analysis of the Asteropyginae led to the recognition of the genus Minicryphaeu... more A recent cladistic analysis of the Asteropyginae led to the recognition of the genus Minicryphaeus as one of the most ancestral of this subfamily. A new species, M. giganteus, is described here from the Ihandar Formation (Pragian, Lower Devonian) of Jbel El Mrakib, southern part of the Mader Basin (Morocco). Among other characteristic features, it is almost three times larger than the other species of the genus. The description of this new species provides information on the ancestral character states of the subfamily and necessitated a revision of the oldest known representatives. Moreover, this recent analysis identified Treveropyge as a derived form of asteropygines, whereas it was traditionally considered as ancestral due to one of its oldest species, now Ganetops ebbae nov. comb., which was formerly included in this genus. In order to offer a better view of the ancestral Asteropyginae, the features of M. giganteus nov. sp. and G. ebbae nov. comb. have been coded following the scheme of the previous cladistic analysis. The updated phylogeny reveals that M. giganteus nov. sp. is the sister-group of the other Minicryphaeus species; a paedomorphic event explains their decreasing size. The new phylogeny confirms the basal position of G. ebbae nov. comb. and distinguishes it clearly from the genus Treveropyge, which necessitates the erection of the new genus Ganetops. It appears that the association of G. ebbae nov. comb. with more derived species within the genus Treveropyge disturbed the previous cladistics analysis of the Asteropyginae. Indeed, considering a derived species as root of the subfamily leads necessarily to the formation of two major clades, as it was usually suggested for the Asteropyginae.
Journal of Systematic Palaeontology, Aug 2014
Traditionally, the evolutionary scenarios of Asteropyginae have been organized in two major clade... more Traditionally, the evolutionary scenarios of Asteropyginae have been organized in two major clades involving four pygidial patterns. The first cladistic analysis performed on the subfamily maintained the organization in two clades, though the phylogenetic relationships between genera were unexpected compared to the traditional scenarios. Moreover, the previous systematic scheme based on pygidial segmentation was rendered obsolete. In this study, we performed a new phylogenetic analysis from well-known taxa and recent discoveries. Sixty species assigned to 36 genera have been analysed from a dataset of 72 characters. Three more species are used as the outgroup. The 79 most parsimonious trees have a length of 492 steps and a retention index of 0.735. Our analysis confirms the monophyly of Asteropyginae excluding the genus Protacanthina. The phylogenetic pattern is unconventional in that a largely pectinate topology is resolved, rather than two clades corresponding to formerly delimited pygidial morphs. Nevertheless, most relationships between genera suggested in the traditional evolutionary scenarios of the subfamily have been recovered, the main differences being the origin of the group. Whereas Treveropyge was usually considered as the origin of the remaining Asteropyginae, the present results instead identify Destombesina as the sister group to all remaining members of the subfamily. From the new phylogenetic pattern, the diagnoses of genera are rewritten in a standard way and to delimit clades more accurately. This work implies modified generic assignments for some species and the erection of four new genera: Minicryphaeus gen. nov., Gandlops gen. nov., Morzadecops gen. nov. and Pennarbedops gen. nov. The systematic position of Erbenochile is also discussed, the genus no longer being assigned to Asteropyginae.
PALAEONTOLOGISCHE ZEITSCHRIFT, Jun 2013
Complete early ontogenetic stages of phacopid trilobites are very rare in the fossil record world... more Complete early ontogenetic stages of phacopid trilobites are very rare in the fossil record worldwide. Although phacopid trilobites were a common component of the Devonian communities inhabiting the Prague Basin, only two articulated juvenile individuals have been described so far. However, rich and diverse fauna, including common remains of meraspid and young holaspid specimens of the phacopid Pedinopariops superstes superstes, has been found in the late Emsian Daleje Shale (Daleje-TA (TM) ebotov Formation) at the eA (TM) inka Quarry near Bubovice. The rather unusual association of skeletal fauna in the Daleje Shale collected from the eA (TM) inka Quarry probably reflects the specific position of the locality, which corresponds to the transition from shale facies to carbonate facies. This newly described association contains common molted young holaspids, one entire meraspid specimen, and one poorly preserved but entire late meraspid-early holaspid specimen. The young individuals of P. superstes superstes strongly resemble the ancestral Pedinopariops degener; with the exception of their smaller eyes, they are somewhat reminiscent of the coarsely tuberculated descendent Pedinopariops superstes superior. The principal differences between the early stages of P. superstes superstes and the adult specimens include the relatively coarse tuberculation of the dorsal exoskeleton, which is more strongly vaulted and shows a less advanced level of eye development in young specimens. However, co-occurring adult specimens appear to be typical P. superstes. Here, the newly collected material is supplemented with a description of two as yet unreported remains of juvenile Pedinopariops superstes from other localities, and one well preserved specimen of an entire meraspid of Reedops cf. bronni, as well as a detailed discussion of the two previously described specimens of Pedinopariops insequens and Prokops hoeninghausi. Possible causes of an obvious paucity of articulated meraspid and young holaspid specimens when compared with adult and subadult ontogenetic stages in phacopid trilobites are discussed.
Journal of Paleontology, Jan 1, 2012
Numerous exuviae of three Dechenella species (D. givetensis, D. ziegleri and D. calxensis) from t... more Numerous exuviae of three Dechenella species (D. givetensis, D. ziegleri and D. calxensis) from the Middle Devonian (Givetian) of NE France (Ardenne Massif) provide the opportunity to identify the evolution- ary modifications of ontogeny of the three Dechenella species and to elaborate a conceptual framework of developmental shape changes. First we used biometric and morphometric approaches to characterize shape modifications. Then we computed ontogenetic trajectories by multivariate regression of geometric shape variables on centroid size in order to compare them. Finally, we compared parallelism between trajectories and rates of development relative to size. These analyses demonstrate a significant difference in the cranidial developmental trajectories of D. givetensis and D. ziegleri indicating an allometric repatterning. However, pygidia of these species share the same allometric pattern with a distinct developmental rate suggesting that heterochrony could be a partial explanation for the body shape evolution. Pygidial ontogeny of D. calxensis corresponds to an allometric repatterning with respect to both other species. This work illustrates the complexity of evolutionary modifications of ontogeny constituting an important process in morphological novelties.
… Transactions of the Royal Society of …, Jan 1, 2011
Recent investigation of the historical Mont d’Haurs section near Givet yielded numerous trilobite... more Recent investigation of the historical Mont d’Haurs section near Givet yielded numerous trilobites from Middle Devonian carbonate deposits. The trilobite fauna described in the present paper comprises a number of taxa from the basal Givetian, including two new ones: Dechenella givetensis sp. n.; Dechenella calxensis sp. n.; Dechenella ziegleri Struve, 1992; Goldius cf. capitellum (Archinal, 1994); and Nyterops cf. hollandi van Viersen, 2007a. This fauna confirms the previously recognised taxonomic diversity pattern and the Dechenella and Nyterops Association from the middle Middle Devonian in the Ardenne area.
Geologica Belgica, Jan 1, 2004
The Frasnian representatives of Asteropyginae in the Frasnes area (south Belgium) have long been ... more The Frasnian representatives of Asteropyginae in the Frasnes area (south Belgium) have long been relatively well-documented when compared to other trilobites in the Devonian of the Ardennes (Belgium, northern France). However, examination of the type material and new collecting by the authors indicate that a taxonomic review has become necessary. Two new species of Bradocryphaeus are recorded, B. vanherlei sp. nov. and B. neptuni sp. nov.; one additional species, B. sp. 20, is known from the pygidium alone. New material is recorded of Bradocryphaeus maillieuxi (Richter & Richter), which has hitherto been scantily illustrated in the literature. The cephalon of Heliopyge helios (Richter & Richter) is redescribed on the basis of new specimens and its holotype pygidium refigured.
Comptes Rendus Palevol, Jan 1, 2011
The palaeontological species concept – a rather subjective concept – is based on morpho- logical ... more The palaeontological species concept – a rather subjective concept – is based on morpho- logical criteria and carries a notion of time. The delimitation of a species among trilobites does not break this rule and is based on morphological and ontogenetic features. Thus, among phacopid trilobites, characters such as the visual complex and the vincular furrow are diagnostic. Furthermore, quantitative studies of the morphological disparity and onto- genetic trajectories allow us better to define the species and its variability, and to identify the evolutionary patterns established in Phacopidae during 100 Ma of existence.
Advances in trilobite …, Jan 1, 2008
The Givetian platform of the Ardennes Massif records several alternations between a siliciclastic... more The Givetian platform of the Ardennes Massif records several alternations between a siliciclastic-carbonate ramp and a carbonate shelf. Usually these depositional contexts are considered as a major disruption implying a perturbation of many ecological parameters. We established the impact of these variations on the biodiversity structure through the study of the trophic organisation. Thanks to a previous microfacies analysis, 550 levels of the Mont d'Haurs section in Givet and ten associated environments were precisely defined. Seven palaeotrophic levels are recognized from micropalaeontological data, including benthic, planktonic, heterotroph and autotroph organisms. The spatial and temporal distributions of these levels have been analysed through means of multivariate analyses. The statistic results show that the distribution of the palaeotrophic levels during periods characterized by a mixed ramp is not significantly different than during carbonate shelf influences. These environmental modifications do not affect the community-type. These results support recent studies performed on different benthic communities occurring in the Givetian of the Ardennes Massif. Indeed, trilobite and ostracod faunas of this period appear more affected by global environmental changes as the Kačák (uppermost Eifelian) and Taghanic (late middle Givetian) events. Moreover, along the proximal-distal transect on the platform, the reef constitutes the most singular environment. However, contrary with the Frasnian reefs of the Ardennes Massif, which consist of carbonate mud mounds laying on a deep mixed ramp, there is no trilobite community that appears restricted to Givetian reefs. Thus global bioevents during the Middle Devonian have a more important control on the biodiversity than the platform morphology. These results support the view that at wide scales (spatial and temporal), the biodiversity responds more positively to ecological disturbances.
The palaeontological species concept – a rather subjective concept – is based on morphological cr... more The palaeontological species concept – a rather subjective concept – is based on morphological
criteria and carries a notion of time. The delimitation of a species among trilobites
does not break this rule and is based on morphological and ontogenetic features. Thus,
among phacopid trilobites, characters such as the visual complex and the vincular furrow
are diagnostic. Furthermore, quantitative studies of the morphological disparity and ontogenetic
trajectories allow us better to define the species and its variability, and to identify
the evolutionary patterns established in Phacopidae during 100Ma of existence.
Numerous exuviae of three Dechenella species (D. givetensis, D. ziegleri and D. calxensis) from t... more Numerous exuviae of three Dechenella species (D. givetensis, D. ziegleri and D. calxensis) from the
Middle Devonian (Givetian) of NE France (Ardenne Massif) provide the opportunity to identify the evolutionary
modifications of ontogeny of the three Dechenella species and to elaborate a conceptual framework of
developmental shape changes. First we used biometric and morphometric approaches to characterize shape
modifications. Then we computed ontogenetic trajectories by multivariate regression of geometric shape variables
on centroid size in order to compare them. Finally, we compared parallelism between trajectories and rates of
development relative to size. These analyses demonstrate a significant difference in the cranidial developmental
trajectories of D. givetensis and D. ziegleri indicating an allometric repatterning. However, pygidia of these species
share the same allometric pattern with a distinct developmental rate suggesting that heterochrony could be a partial
explanation for the body shape evolution. Pygidial ontogeny of D. calxensis corresponds to an allometric
repatterning with respect to both other species. This work illustrates the complexity of evolutionary modifications of
ontogeny constituting an important process in morphological novelties.
Recent investigation of the historical Mont d’Haurs section near Givet yielded numerous trilobite... more Recent investigation of the historical Mont d’Haurs section near Givet yielded
numerous trilobites from Middle Devonian carbonate deposits. The trilobite fauna described in the
present paper comprises a number of taxa from the basal Givetian, including two new ones:
Dechenella givetensis sp. n.; Dechenella calxensis sp. n.; Dechenella ziegleri Struve, 1992; Goldius cf.
capitellum (Archinal, 1994); and Nyterops cf. hollandi van Viersen, 2007a. This fauna confirms the
previously recognised taxonomic diversity pattern and the Dechenella and Nyterops Association
from the middle Middle Devonian in the Ardenne area.
Traditionally, the evolutionary scenarios of Asteropyginae have been organized in two major clade... more Traditionally, the evolutionary scenarios of Asteropyginae have been organized in two major clades involving four pygidial
patterns. The first cladistic analysis performed on the subfamily maintained the organization in two clades, though the
phylogenetic relationships between genera were unexpected compared to the traditional scenarios. Moreover, the previous
systematic scheme based on pygidial segmentation was rendered obsolete. In this study, we performed a new phylogenetic
analysis from well-known taxa and recent discoveries. Sixty species assigned to 36 genera have been analysed from a
dataset of 72 characters. Three more species are used as the outgroup. The 79 most parsimonious trees have a length of
492 steps and a retention index of 0.735. Our analysis confirms the monophyly of Asteropyginae excluding the genus
Protacanthina. The phylogenetic pattern is unconventional in that a largely pectinate topology is resolved, rather than two
clades corresponding to formerly delimited pygidial morphs. Nevertheless, most relationships between genera suggested in
the traditional evolutionary scenarios of the subfamily have been recovered, the main differences being the origin of the
group. Whereas Treveropyge was usually considered as the origin of the remaining Asteropyginae, the present results instead
identify Destombesina as the sister group to all remaining members of the subfamily. From the new phylogenetic pattern,
the diagnoses of genera are rewritten in a standard way and to delimit clades more accurately. This work implies modified
generic assignments for some species and the erection of four new genera: Minicryphaeus gen. nov., Gandlops gen. nov.,
Morzadecops gen. nov. and Pennarbedops gen. nov. The systematic position of Erbenochile is also discussed, the genus no
longer being assigned to Asteropyginae.
Acta Palaeontologica Polonica, 60 (4), 949-962
During the Devonian the sedimentation on the continental shelves of Ardenne Massif and Boulonnais... more During the Devonian the sedimentation on the continental shelves of Ardenne Massif and Boulonnais has changed from a mixed siliciclastic-carbonate ramp (Eifelian), through a carbonate barrier reef (Givetian) and then to a detritic influx with local mud-mounds (Frasnian). Here we analysed the faunistic dynamics of the trilobite associations through the changing environment. We used multivariate analyses (clustering and ordering) to discriminate the trilobite associations within 67 different samples. Three previously known communities and one new were recognised: the Eifelian Mixed association, the Givetian Dechenella association and the two Frasnian Bradocryphaeus and Scutellum-Goldius associations. These trilobite faunas present a progressive ecological specialisation. The Mixed association occurs both in the ramp or carbonated (local reef developed on the ramp) facies without any significant difference in its composition. The Dechenella fauna occurs preferentially close to barrier reefs, but can also survive during short periods of detrital input. The two Frasnian communities show a strong relationship with their environment. The Scutellum-Goldius association is only found in reef systems, whereas the Bradocryphaeus flourishes exclusively in lateral facies.
Geobios, Nov 2014
A recent cladistic analysis of the Asteropyginae led to the recognition of the genus Minicryphaeu... more A recent cladistic analysis of the Asteropyginae led to the recognition of the genus Minicryphaeus as one of the most ancestral of this subfamily. A new species, M. giganteus, is described here from the Ihandar Formation (Pragian, Lower Devonian) of Jbel El Mrakib, southern part of the Mader Basin (Morocco). Among other characteristic features, it is almost three times larger than the other species of the genus. The description of this new species provides information on the ancestral character states of the subfamily and necessitated a revision of the oldest known representatives. Moreover, this recent analysis identified Treveropyge as a derived form of asteropygines, whereas it was traditionally considered as ancestral due to one of its oldest species, now Ganetops ebbae nov. comb., which was formerly included in this genus. In order to offer a better view of the ancestral Asteropyginae, the features of M. giganteus nov. sp. and G. ebbae nov. comb. have been coded following the scheme of the previous cladistic analysis. The updated phylogeny reveals that M. giganteus nov. sp. is the sister-group of the other Minicryphaeus species; a paedomorphic event explains their decreasing size. The new phylogeny confirms the basal position of G. ebbae nov. comb. and distinguishes it clearly from the genus Treveropyge, which necessitates the erection of the new genus Ganetops. It appears that the association of G. ebbae nov. comb. with more derived species within the genus Treveropyge disturbed the previous cladistics analysis of the Asteropyginae. Indeed, considering a derived species as root of the subfamily leads necessarily to the formation of two major clades, as it was usually suggested for the Asteropyginae.
Journal of Systematic Palaeontology, Aug 2014
Traditionally, the evolutionary scenarios of Asteropyginae have been organized in two major clade... more Traditionally, the evolutionary scenarios of Asteropyginae have been organized in two major clades involving four pygidial patterns. The first cladistic analysis performed on the subfamily maintained the organization in two clades, though the phylogenetic relationships between genera were unexpected compared to the traditional scenarios. Moreover, the previous systematic scheme based on pygidial segmentation was rendered obsolete. In this study, we performed a new phylogenetic analysis from well-known taxa and recent discoveries. Sixty species assigned to 36 genera have been analysed from a dataset of 72 characters. Three more species are used as the outgroup. The 79 most parsimonious trees have a length of 492 steps and a retention index of 0.735. Our analysis confirms the monophyly of Asteropyginae excluding the genus Protacanthina. The phylogenetic pattern is unconventional in that a largely pectinate topology is resolved, rather than two clades corresponding to formerly delimited pygidial morphs. Nevertheless, most relationships between genera suggested in the traditional evolutionary scenarios of the subfamily have been recovered, the main differences being the origin of the group. Whereas Treveropyge was usually considered as the origin of the remaining Asteropyginae, the present results instead identify Destombesina as the sister group to all remaining members of the subfamily. From the new phylogenetic pattern, the diagnoses of genera are rewritten in a standard way and to delimit clades more accurately. This work implies modified generic assignments for some species and the erection of four new genera: Minicryphaeus gen. nov., Gandlops gen. nov., Morzadecops gen. nov. and Pennarbedops gen. nov. The systematic position of Erbenochile is also discussed, the genus no longer being assigned to Asteropyginae.
PALAEONTOLOGISCHE ZEITSCHRIFT, Jun 2013
Complete early ontogenetic stages of phacopid trilobites are very rare in the fossil record world... more Complete early ontogenetic stages of phacopid trilobites are very rare in the fossil record worldwide. Although phacopid trilobites were a common component of the Devonian communities inhabiting the Prague Basin, only two articulated juvenile individuals have been described so far. However, rich and diverse fauna, including common remains of meraspid and young holaspid specimens of the phacopid Pedinopariops superstes superstes, has been found in the late Emsian Daleje Shale (Daleje-TA (TM) ebotov Formation) at the eA (TM) inka Quarry near Bubovice. The rather unusual association of skeletal fauna in the Daleje Shale collected from the eA (TM) inka Quarry probably reflects the specific position of the locality, which corresponds to the transition from shale facies to carbonate facies. This newly described association contains common molted young holaspids, one entire meraspid specimen, and one poorly preserved but entire late meraspid-early holaspid specimen. The young individuals of P. superstes superstes strongly resemble the ancestral Pedinopariops degener; with the exception of their smaller eyes, they are somewhat reminiscent of the coarsely tuberculated descendent Pedinopariops superstes superior. The principal differences between the early stages of P. superstes superstes and the adult specimens include the relatively coarse tuberculation of the dorsal exoskeleton, which is more strongly vaulted and shows a less advanced level of eye development in young specimens. However, co-occurring adult specimens appear to be typical P. superstes. Here, the newly collected material is supplemented with a description of two as yet unreported remains of juvenile Pedinopariops superstes from other localities, and one well preserved specimen of an entire meraspid of Reedops cf. bronni, as well as a detailed discussion of the two previously described specimens of Pedinopariops insequens and Prokops hoeninghausi. Possible causes of an obvious paucity of articulated meraspid and young holaspid specimens when compared with adult and subadult ontogenetic stages in phacopid trilobites are discussed.
Journal of Paleontology, Jan 1, 2012
Numerous exuviae of three Dechenella species (D. givetensis, D. ziegleri and D. calxensis) from t... more Numerous exuviae of three Dechenella species (D. givetensis, D. ziegleri and D. calxensis) from the Middle Devonian (Givetian) of NE France (Ardenne Massif) provide the opportunity to identify the evolution- ary modifications of ontogeny of the three Dechenella species and to elaborate a conceptual framework of developmental shape changes. First we used biometric and morphometric approaches to characterize shape modifications. Then we computed ontogenetic trajectories by multivariate regression of geometric shape variables on centroid size in order to compare them. Finally, we compared parallelism between trajectories and rates of development relative to size. These analyses demonstrate a significant difference in the cranidial developmental trajectories of D. givetensis and D. ziegleri indicating an allometric repatterning. However, pygidia of these species share the same allometric pattern with a distinct developmental rate suggesting that heterochrony could be a partial explanation for the body shape evolution. Pygidial ontogeny of D. calxensis corresponds to an allometric repatterning with respect to both other species. This work illustrates the complexity of evolutionary modifications of ontogeny constituting an important process in morphological novelties.
… Transactions of the Royal Society of …, Jan 1, 2011
Recent investigation of the historical Mont d’Haurs section near Givet yielded numerous trilobite... more Recent investigation of the historical Mont d’Haurs section near Givet yielded numerous trilobites from Middle Devonian carbonate deposits. The trilobite fauna described in the present paper comprises a number of taxa from the basal Givetian, including two new ones: Dechenella givetensis sp. n.; Dechenella calxensis sp. n.; Dechenella ziegleri Struve, 1992; Goldius cf. capitellum (Archinal, 1994); and Nyterops cf. hollandi van Viersen, 2007a. This fauna confirms the previously recognised taxonomic diversity pattern and the Dechenella and Nyterops Association from the middle Middle Devonian in the Ardenne area.
Geologica Belgica, Jan 1, 2004
The Frasnian representatives of Asteropyginae in the Frasnes area (south Belgium) have long been ... more The Frasnian representatives of Asteropyginae in the Frasnes area (south Belgium) have long been relatively well-documented when compared to other trilobites in the Devonian of the Ardennes (Belgium, northern France). However, examination of the type material and new collecting by the authors indicate that a taxonomic review has become necessary. Two new species of Bradocryphaeus are recorded, B. vanherlei sp. nov. and B. neptuni sp. nov.; one additional species, B. sp. 20, is known from the pygidium alone. New material is recorded of Bradocryphaeus maillieuxi (Richter & Richter), which has hitherto been scantily illustrated in the literature. The cephalon of Heliopyge helios (Richter & Richter) is redescribed on the basis of new specimens and its holotype pygidium refigured.
Comptes Rendus Palevol, Jan 1, 2011
The palaeontological species concept – a rather subjective concept – is based on morpho- logical ... more The palaeontological species concept – a rather subjective concept – is based on morpho- logical criteria and carries a notion of time. The delimitation of a species among trilobites does not break this rule and is based on morphological and ontogenetic features. Thus, among phacopid trilobites, characters such as the visual complex and the vincular furrow are diagnostic. Furthermore, quantitative studies of the morphological disparity and onto- genetic trajectories allow us better to define the species and its variability, and to identify the evolutionary patterns established in Phacopidae during 100 Ma of existence.
Advances in trilobite …, Jan 1, 2008