Morphological matrices, including the conceptualization of characters and character states and sc... more Morphological matrices, including the conceptualization of characters and character states and scoring thereof, still are a valuable and necessary tool for phylogenetic analyses. Although they are often seen only as numerically simplified summaries of observations for the purpose of cladistic analyses, they also hold value as collections of ideas, concepts and the current state of knowledge, conveying various hypotheses on character state identity, homology and evolutionary transformations. A common and persistent issue in scoring and analysing morphological matrices is the phenomenon of inapplicable characters (“inapplicables”). Inapplicables result from the ontological dependency (based on hierarchical relationships) between characters. Traditionally handled the same as “missing data”, inapplicables were shown to be problematic in holding the potential to result in unreasonable algorithmic preference for certain cladograms over others. Recently, though, this problem has been solved by approaching parsimony as a maximization of homology rather than a minimization of transformational steps. We herein aim to further improve our theoretical understanding of the underlying hierarchical nature of morphological characters, which causes the phenomenon of ontological dependencies and, thereby, inapplicables. As a result, we present a discussion of various character-dependency scenarios and a new concept of hierarchical character relationships as being composed of four complementary sub-aspects. Building on this, a new syntax for the designation of character dependencies as part of the character statement is proposed, to help identify and apply scoring constraints for manual and automated scoring of morphological character matrices and their cladistic analysis.
Within Malacostraca, legs are diversified variously throughout the groups. Most conspicuous is th... more Within Malacostraca, legs are diversified variously throughout the groups. Most conspicuous is the transformation of anterior thoracopods, especially the first, into maxillipeds involved in feeding. However, the concept of a maxilliped is not precise, because it relates to a vague combination of morphological and functional deviation from a locomotory limb. Although general homology of the first thoracopod (maxilliped or not) is beyond doubt, special homology (synapomorphy) of the anteriormost maxillipeds remains uncertain. For better insights, we studied the musculature and exoskeletal structures of the first thoracopods in Anaspidacea, Euphausiacea, Lophogastrida, Mysida and Stygiomysida, using three-dimensional reconstruction of laser scanning microscopy and micro-computed tomography data. Our analysis shows high muscular and skeletal complexity of the first thoracopods. We herein reject the term ‘maxilliped’ for Anaspidacea and Euphausiacea, because their first thoracopods differ little from the posterior limbs, although specific correspondences between these taxa might represent synapomorphies. The ‘mysidacean maxilliped’ is morphologically well derived from the posterior thoracopods and appears synapomorphic for the mysidacean subtaxa. A comparison with other Peracarida additionally shows correspondences indicating a homologous ‘peracaridan maxilliped’. In contrast, we consider the peracaridan maxilliped not to be homologous to the decapodan maxilliped. As a distinction, we propose the term ‘unguiped’ for the peracaridan first thoracopod.
Here, we provide the first complete mitochondrial genomes for two higher taxa of Peracarida, Loph... more Here, we provide the first complete mitochondrial genomes for two higher taxa of Peracarida, Lophogastrida and Stygiomysida. We examined Lophogaster typicus as a representative of Lophogastrida and Spelaeomysis bottazzii as a representative of Stygiomysida. Both mitogenomes have all typical metazoan genes (13 protein-coding genes, two ribosomal RNA genes and 22 transfer RNAs). The mitogenomes have a length of 15,076 bp in L. typicus and 14,806 bp in S. bottazzii. Gene order differs markedly from the hypothetical pancrustacean/malacostracan ground pattern in both species, and in L. typicus, all genes were encoded on the heavy strand. This is the first time this is described for a crustacean. We also reconstruct eumalacostracan phylogenies using a data set consisting of 98 species based on alignments comprising all protein-encoding genes as well as the protein-encoding genes and the two ribosomal RNAs. We find support for the monophyly of Mysidacea based on species from all three higher taxa (Mysida, Lophogastrida, Stygiomysida). Moreover, our analyses also support a monophyletic Peracarida with Amphipoda or Amphipoda + Mysidacea as the sister group to the remaining Peracarida.
Anaspidacea is probably the most enigmatic higher taxon within the Malacostraca. Representatives ... more Anaspidacea is probably the most enigmatic higher taxon within the Malacostraca. Representatives of the genus Anaspides are often considered “living fossils” due to their strong resemblance to their Triassic relatives. In comparison to other extant Malacostraca, they possess a high number of plesiomorphic characters. Anaspidacea are often combined with another freshwater taxon, Bathynellacea, into the Syncarida, but actual evidence for monophyletic Syncarida is weak. Other potential sister groups are Eucarida, Euphausiacea, or Euphausiacea + Peracarida. Like Euphausiacea, Mysidacea and “natant” decapods, Anaspidacea show what has been called a “caridoid facies”. In malacostracan crustaceans, a prominent mode of locomotion is swimming, as it almost certainly was for the malacostracans’ common ancestor. However, when considered in detail, swimming is found to take quite different forms in the various taxa. To obtain a better understanding of the evolution of swimming, we analyzed locomotion in several species of Anaspides endemic to Tasmania. The morphology of the protopodal and exopodal musculature as well as the exo- and endoskeletal structures of the thoracopods were examined using 3D reconstruction of CLSM- and μCT data. Various aspects of locomotion were documented and described using recording techniques including in-habitat underwater filming and macro high-speed recording. Our analysis shows the high level of complexity of the muscular arrangement and skeletal construction in the thoracopods of these - in many regards plesiomorphic - malacostracans, and demonstrates the presence of epipodal musculature. Our recordings provide insight into various aspects of locomotion of Anaspides, including the congruence of locomotive kinematics in swimming and walking. Our morphological findings and observations on locomotion in Anaspides are compared to findings in other malacostracan shrimps and discussed in a phylogenetic context, with our analysis providing further support for Xenommacarida (sensu Richter, 1999: Anaspidacea + Euphausiacea + Peracarida). Further, a new hypothesis for the origin of the ventral brood pouch, the marsupium, of Peracarida is discussed. On the basis of a comparison of their morphology and biology, the oostegites which form the marsupium are suggested to be derived thoracopodal endites as present in female Anaspides. Finally, an evolutionary scenario is presented and mapped on a cladogram in which the evolution of malacostracan swimming from a common caridoid ancestor up to the different taxa present today is discussed.
Zoologischer Anzeiger - A Journal of Comparative Zoology, 2018
Thelyphonidae are one of a small number of taxa within the Arachnida that do not walk on four pai... more Thelyphonidae are one of a small number of taxa within the Arachnida that do not walk on four pairs of post-pedipalpal legs. The second, third and fourth pair are used for locomotion, while the first pair has evolved into a pair of elongated and antenniform sensory appendages extensively covered with sensilla. The podomeres of this first pair of legs display about six additional tarsomeres, and the terminal claw-like apotele is reduced. A patella as found in the posterior three pairs of legs, and in all four pairs of legs of the closely related Amblypygi and Araneae, appears to be absent. This has caused some authors to assume that the patella has fused with the tibia to form a so-called "patellotibia". However, this hypothesis is controversial, and various authors have used a labelling of the podomeres of the antenniform pair of legs including a "patella". To shed more light on the matter, we analyse here the morphology of the four pairs of post-pedipalpal legs in Mastigoproctus giganteus. Our study uses micro-computed tomography (μCT)-based 3D reconstructions of the intrinsic muscles and cuticle components of the podomeres to describe and compare these morphological structures. The evolutionary changes undergone by the podomeres and the muscular system in the antenniform legs of Thelyphonidae are discussed and the homologous identity between podomeres is discussed on the basis of the hypothesis of serial homology. Our findings imply a refutal of the patellotibia hypothesis.
Morphological matrices, including the conceptualization of characters and character states and sc... more Morphological matrices, including the conceptualization of characters and character states and scoring thereof, still are a valuable and necessary tool for phylogenetic analyses. Although they are often seen only as numerically simplified summaries of observations for the purpose of cladistic analyses, they also hold value as collections of ideas, concepts and the current state of knowledge, conveying various hypotheses on character state identity, homology and evolutionary transformations. A common and persistent issue in scoring and analysing morphological matrices is the phenomenon of inapplicable characters (“inapplicables”). Inapplicables result from the ontological dependency (based on hierarchical relationships) between characters. Traditionally handled the same as “missing data”, inapplicables were shown to be problematic in holding the potential to result in unreasonable algorithmic preference for certain cladograms over others. Recently, though, this problem has been solved by approaching parsimony as a maximization of homology rather than a minimization of transformational steps. We herein aim to further improve our theoretical understanding of the underlying hierarchical nature of morphological characters, which causes the phenomenon of ontological dependencies and, thereby, inapplicables. As a result, we present a discussion of various character-dependency scenarios and a new concept of hierarchical character relationships as being composed of four complementary sub-aspects. Building on this, a new syntax for the designation of character dependencies as part of the character statement is proposed, to help identify and apply scoring constraints for manual and automated scoring of morphological character matrices and their cladistic analysis.
Within Malacostraca, legs are diversified variously throughout the groups. Most conspicuous is th... more Within Malacostraca, legs are diversified variously throughout the groups. Most conspicuous is the transformation of anterior thoracopods, especially the first, into maxillipeds involved in feeding. However, the concept of a maxilliped is not precise, because it relates to a vague combination of morphological and functional deviation from a locomotory limb. Although general homology of the first thoracopod (maxilliped or not) is beyond doubt, special homology (synapomorphy) of the anteriormost maxillipeds remains uncertain. For better insights, we studied the musculature and exoskeletal structures of the first thoracopods in Anaspidacea, Euphausiacea, Lophogastrida, Mysida and Stygiomysida, using three-dimensional reconstruction of laser scanning microscopy and micro-computed tomography data. Our analysis shows high muscular and skeletal complexity of the first thoracopods. We herein reject the term ‘maxilliped’ for Anaspidacea and Euphausiacea, because their first thoracopods differ little from the posterior limbs, although specific correspondences between these taxa might represent synapomorphies. The ‘mysidacean maxilliped’ is morphologically well derived from the posterior thoracopods and appears synapomorphic for the mysidacean subtaxa. A comparison with other Peracarida additionally shows correspondences indicating a homologous ‘peracaridan maxilliped’. In contrast, we consider the peracaridan maxilliped not to be homologous to the decapodan maxilliped. As a distinction, we propose the term ‘unguiped’ for the peracaridan first thoracopod.
Here, we provide the first complete mitochondrial genomes for two higher taxa of Peracarida, Loph... more Here, we provide the first complete mitochondrial genomes for two higher taxa of Peracarida, Lophogastrida and Stygiomysida. We examined Lophogaster typicus as a representative of Lophogastrida and Spelaeomysis bottazzii as a representative of Stygiomysida. Both mitogenomes have all typical metazoan genes (13 protein-coding genes, two ribosomal RNA genes and 22 transfer RNAs). The mitogenomes have a length of 15,076 bp in L. typicus and 14,806 bp in S. bottazzii. Gene order differs markedly from the hypothetical pancrustacean/malacostracan ground pattern in both species, and in L. typicus, all genes were encoded on the heavy strand. This is the first time this is described for a crustacean. We also reconstruct eumalacostracan phylogenies using a data set consisting of 98 species based on alignments comprising all protein-encoding genes as well as the protein-encoding genes and the two ribosomal RNAs. We find support for the monophyly of Mysidacea based on species from all three higher taxa (Mysida, Lophogastrida, Stygiomysida). Moreover, our analyses also support a monophyletic Peracarida with Amphipoda or Amphipoda + Mysidacea as the sister group to the remaining Peracarida.
Anaspidacea is probably the most enigmatic higher taxon within the Malacostraca. Representatives ... more Anaspidacea is probably the most enigmatic higher taxon within the Malacostraca. Representatives of the genus Anaspides are often considered “living fossils” due to their strong resemblance to their Triassic relatives. In comparison to other extant Malacostraca, they possess a high number of plesiomorphic characters. Anaspidacea are often combined with another freshwater taxon, Bathynellacea, into the Syncarida, but actual evidence for monophyletic Syncarida is weak. Other potential sister groups are Eucarida, Euphausiacea, or Euphausiacea + Peracarida. Like Euphausiacea, Mysidacea and “natant” decapods, Anaspidacea show what has been called a “caridoid facies”. In malacostracan crustaceans, a prominent mode of locomotion is swimming, as it almost certainly was for the malacostracans’ common ancestor. However, when considered in detail, swimming is found to take quite different forms in the various taxa. To obtain a better understanding of the evolution of swimming, we analyzed locomotion in several species of Anaspides endemic to Tasmania. The morphology of the protopodal and exopodal musculature as well as the exo- and endoskeletal structures of the thoracopods were examined using 3D reconstruction of CLSM- and μCT data. Various aspects of locomotion were documented and described using recording techniques including in-habitat underwater filming and macro high-speed recording. Our analysis shows the high level of complexity of the muscular arrangement and skeletal construction in the thoracopods of these - in many regards plesiomorphic - malacostracans, and demonstrates the presence of epipodal musculature. Our recordings provide insight into various aspects of locomotion of Anaspides, including the congruence of locomotive kinematics in swimming and walking. Our morphological findings and observations on locomotion in Anaspides are compared to findings in other malacostracan shrimps and discussed in a phylogenetic context, with our analysis providing further support for Xenommacarida (sensu Richter, 1999: Anaspidacea + Euphausiacea + Peracarida). Further, a new hypothesis for the origin of the ventral brood pouch, the marsupium, of Peracarida is discussed. On the basis of a comparison of their morphology and biology, the oostegites which form the marsupium are suggested to be derived thoracopodal endites as present in female Anaspides. Finally, an evolutionary scenario is presented and mapped on a cladogram in which the evolution of malacostracan swimming from a common caridoid ancestor up to the different taxa present today is discussed.
Zoologischer Anzeiger - A Journal of Comparative Zoology, 2018
Thelyphonidae are one of a small number of taxa within the Arachnida that do not walk on four pai... more Thelyphonidae are one of a small number of taxa within the Arachnida that do not walk on four pairs of post-pedipalpal legs. The second, third and fourth pair are used for locomotion, while the first pair has evolved into a pair of elongated and antenniform sensory appendages extensively covered with sensilla. The podomeres of this first pair of legs display about six additional tarsomeres, and the terminal claw-like apotele is reduced. A patella as found in the posterior three pairs of legs, and in all four pairs of legs of the closely related Amblypygi and Araneae, appears to be absent. This has caused some authors to assume that the patella has fused with the tibia to form a so-called "patellotibia". However, this hypothesis is controversial, and various authors have used a labelling of the podomeres of the antenniform pair of legs including a "patella". To shed more light on the matter, we analyse here the morphology of the four pairs of post-pedipalpal legs in Mastigoproctus giganteus. Our study uses micro-computed tomography (μCT)-based 3D reconstructions of the intrinsic muscles and cuticle components of the podomeres to describe and compare these morphological structures. The evolutionary changes undergone by the podomeres and the muscular system in the antenniform legs of Thelyphonidae are discussed and the homologous identity between podomeres is discussed on the basis of the hypothesis of serial homology. Our findings imply a refutal of the patellotibia hypothesis.
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Papers by Markus Grams