Rudy Lerosey-Aubril
My research interests:
I. PALEOBIOLOGY & PALEOECOLOGY OF PRIMITIVE ARTHROPODS
The Cambrian radiation of arthropods permitted the emergence of the stem-groups of extant clades but for the most part, it consisted in the diversification of primitive forms experiencing a variety of body plans with no modern equivalents. Trilobites, the most successful of these primitive groups, achieved the colonization of most marine habitats and survived for more than 270 million years. Investigating their anatomy and that of their closest relatives permits to describe the primitive states of various aspects of arthropod body organization (e.g. digestive system, sensory apparatuses) and therefore to document the early steps of their evolution within the phylum. Combined to data from community analyses and sedimentological studies, morpho-anatomical data also allowed a better assessment of the roles of trilobites within marine ecosystems and their evolution during the Palaeozoic.
*** Current Projects ***
- autecology of scutelluid trilobites: quantitative analysis of their postures (with E. Schindler, Senckenberg RI), volvatory capacities and life habits as revealed by morpho-functional studies (with R. Feist, University Montpellier II)
- sensory organs of aquatic arthropods: the Cephalic Median Organ of trilobites and the Sensory Dorsal Organ of malacostracans (with K.J. McNamara, Cambridge University), the ventral eyes of trilobites (with R. Feist, University Montpellier II).
- the digestive system of trilobites (with T. Hegna, Yale University)
II. THE EVOLUTIONARY HISTORY OF LATE MIDDLE TO LATE PALEOZOIC TRILOBITES
While they were major elements of benthic marine ecosystems from the Cambrian to the Early Devonian, only rare trilobites occurred in the terminal Permian just prior to the complete eradication of the group during the Permo-Triassic mass extinction. The evolutionary history of Middle Devonian to Permian trilobites documents how global changes affecting the planet and its biosphere might have lead to the complete annihilation of organisms which, however, had demonstrated exceptional capacities to diversify and to adapt to new biotopes.
*** Current Projects ***
- Descriptions of new Late Palaeozoic trilobite taxa from various countries (Australia, Iran, Oman, Russia), and especially Turkey. Collaborations: L. Angiolini (Milan University), S. Crasquin-Soleau (University Paris 6), T. Hegna (Yale University), K.J. McNamara (Cambridge University)...
- Analysis of the evolution of trilobite disparity during their Early Carboniferous radiation using morphometric geometrics (SYNTHESYS program BE-TAF 560)
- Exploring the influence of the evolution of palaeogeography on the erosion of trilobite diversity during Carboniferous and Permian times.
III. THE ONTOGENY OF TRILOBITES
The early calcification of trilobite exoskeleton has permitted the preservation of their ontogenetical sequence from larvae to adults. Accordingly, trilobites offer a rare opportunity to investigate developmental processes in primitive arthropods. They also represent a particularly good model to explore the relationships between evolution and development. In addition, ontogenetical data are crucial in assessing phylogenetical relationships within the Trilobita.
*** Current Projects ***
- investigating the ontogeny of Late Devonian to Early Carboniferous trilobites from Thuringia
- evaluating the impact of developmental strategies on the survivorships of Proetida during the Late Devonian biocrises.
Phone: + 61 (0)2 6773 3296
Address: Dr. Rudy Lerosey-Aubril
Division of Earth Sciences
School of Environmental and Rural Science
University of New England
Armidale NSW 2351
Australia
I. PALEOBIOLOGY & PALEOECOLOGY OF PRIMITIVE ARTHROPODS
The Cambrian radiation of arthropods permitted the emergence of the stem-groups of extant clades but for the most part, it consisted in the diversification of primitive forms experiencing a variety of body plans with no modern equivalents. Trilobites, the most successful of these primitive groups, achieved the colonization of most marine habitats and survived for more than 270 million years. Investigating their anatomy and that of their closest relatives permits to describe the primitive states of various aspects of arthropod body organization (e.g. digestive system, sensory apparatuses) and therefore to document the early steps of their evolution within the phylum. Combined to data from community analyses and sedimentological studies, morpho-anatomical data also allowed a better assessment of the roles of trilobites within marine ecosystems and their evolution during the Palaeozoic.
*** Current Projects ***
- autecology of scutelluid trilobites: quantitative analysis of their postures (with E. Schindler, Senckenberg RI), volvatory capacities and life habits as revealed by morpho-functional studies (with R. Feist, University Montpellier II)
- sensory organs of aquatic arthropods: the Cephalic Median Organ of trilobites and the Sensory Dorsal Organ of malacostracans (with K.J. McNamara, Cambridge University), the ventral eyes of trilobites (with R. Feist, University Montpellier II).
- the digestive system of trilobites (with T. Hegna, Yale University)
II. THE EVOLUTIONARY HISTORY OF LATE MIDDLE TO LATE PALEOZOIC TRILOBITES
While they were major elements of benthic marine ecosystems from the Cambrian to the Early Devonian, only rare trilobites occurred in the terminal Permian just prior to the complete eradication of the group during the Permo-Triassic mass extinction. The evolutionary history of Middle Devonian to Permian trilobites documents how global changes affecting the planet and its biosphere might have lead to the complete annihilation of organisms which, however, had demonstrated exceptional capacities to diversify and to adapt to new biotopes.
*** Current Projects ***
- Descriptions of new Late Palaeozoic trilobite taxa from various countries (Australia, Iran, Oman, Russia), and especially Turkey. Collaborations: L. Angiolini (Milan University), S. Crasquin-Soleau (University Paris 6), T. Hegna (Yale University), K.J. McNamara (Cambridge University)...
- Analysis of the evolution of trilobite disparity during their Early Carboniferous radiation using morphometric geometrics (SYNTHESYS program BE-TAF 560)
- Exploring the influence of the evolution of palaeogeography on the erosion of trilobite diversity during Carboniferous and Permian times.
III. THE ONTOGENY OF TRILOBITES
The early calcification of trilobite exoskeleton has permitted the preservation of their ontogenetical sequence from larvae to adults. Accordingly, trilobites offer a rare opportunity to investigate developmental processes in primitive arthropods. They also represent a particularly good model to explore the relationships between evolution and development. In addition, ontogenetical data are crucial in assessing phylogenetical relationships within the Trilobita.
*** Current Projects ***
- investigating the ontogeny of Late Devonian to Early Carboniferous trilobites from Thuringia
- evaluating the impact of developmental strategies on the survivorships of Proetida during the Late Devonian biocrises.
Phone: + 61 (0)2 6773 3296
Address: Dr. Rudy Lerosey-Aubril
Division of Earth Sciences
School of Environmental and Rural Science
University of New England
Armidale NSW 2351
Australia
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Papers by Rudy Lerosey-Aubril
Sidneyia is straight, tubular and relatively narrow in the trunk region. It is enlarged into a pear-shaped area in the cephalic region and stretches notably to form a large pocket in the
abdomen. The mouth is ventral, posteriorly directed and leads to the midgut via a short tubular structure interpreted as the oesophagus. Anteriorly, three pairs of glands with internal, branching tubular structures openinto the digestive tract. These glands have equivalents in various Cambrian arthropod taxa (e.g. naraoiids) and modern arthropods. Their primary function was most likely to digest and assimilate food. The abdominal pocket of Sidneyia concentrates undigested skeletal elements and various residues. It is interpreted here as the functional analogue of the stercoral pocket of some extant terrestrial arachnids (e.g. Araneae, Solifugae), whose primary function is to store food residuals and excretory material until defecation. Analysis of the gut contents indicates that Sidneyia fed largely on small ptychopariid trilobites, brachiopods, possibly agnostids, worms and other undetermined animals. Sidneyia was primarily a durophagous carnivore with predatory
and/or scavenging habits, feeding on small invertebrates that lived at the water-sediment interface. There is no evidence for selective feeding. Its food items (e.g. living prey or dead material) were grasped and manipulated ventrally by its anterior appendages, then macerated into ingestible fragments and conveyed to the mouth via the converging action of
strong molar-like gnathobases. Digestion probably took place within the anterior midgut via enzymes secreted in the glands. Residues were transported through the digestive tract into
the abdominal pocket. The storage of faeces suggests infrequent feeding. The early diagenetic three-dimensional preservation of the digestive glands and abdominal pocket may
be due to the capacity of Sidneyia to store Phosphorus and Calcium (e.g. spherites) in its digestive tissues during life as do, for example, modern horseshoe crabs.
Sidneyia is straight, tubular and relatively narrow in the trunk region. It is enlarged into a pear-shaped area in the cephalic region and stretches notably to form a large pocket in the
abdomen. The mouth is ventral, posteriorly directed and leads to the midgut via a short tubular structure interpreted as the oesophagus. Anteriorly, three pairs of glands with internal, branching tubular structures openinto the digestive tract. These glands have equivalents in various Cambrian arthropod taxa (e.g. naraoiids) and modern arthropods. Their primary function was most likely to digest and assimilate food. The abdominal pocket of Sidneyia concentrates undigested skeletal elements and various residues. It is interpreted here as the functional analogue of the stercoral pocket of some extant terrestrial arachnids (e.g. Araneae, Solifugae), whose primary function is to store food residuals and excretory material until defecation. Analysis of the gut contents indicates that Sidneyia fed largely on small ptychopariid trilobites, brachiopods, possibly agnostids, worms and other undetermined animals. Sidneyia was primarily a durophagous carnivore with predatory
and/or scavenging habits, feeding on small invertebrates that lived at the water-sediment interface. There is no evidence for selective feeding. Its food items (e.g. living prey or dead material) were grasped and manipulated ventrally by its anterior appendages, then macerated into ingestible fragments and conveyed to the mouth via the converging action of
strong molar-like gnathobases. Digestion probably took place within the anterior midgut via enzymes secreted in the glands. Residues were transported through the digestive tract into
the abdominal pocket. The storage of faeces suggests infrequent feeding. The early diagenetic three-dimensional preservation of the digestive glands and abdominal pocket may
be due to the capacity of Sidneyia to store Phosphorus and Calcium (e.g. spherites) in its digestive tissues during life as do, for example, modern horseshoe crabs.
The Weeks Formation comprises a 300-m-thick sequence of thin-bedded lime mudstones, wackestones, and grainstones with variable amounts of shale. It represents an open-shelf marine environment. Two types of exceptional preservation are recognized: 1, pyritization of major morphological details with subsequent oxidization to iron oxides and coating of chlorite; and 2, phosphatization of arthropod guts.
The shelly fauna is dominated by trilobites and brachiopods, while non- or weakly biomineralized organisms are predominantly arthropods and priapulids. The arthropod fauna is rich in aglaspidids, a group best known from Guzhangian-Furongian deposits. However, animals characteristic of Cambrian Series 2-3 (Anomalocaris, leanchoiliids) and Ordovician (Tremaglaspis) biotas are also present, along with several species of uncertain affinities. Accordingly, the Weeks Formation fauna may be regarded as transitional, which supports the hypothesis of more gradual evolution of metazoans during the early Paleozoic.