A ten-legged sea spider (Arthropoda: Pycnogonida) from the Lower Devonian Hunsrück Slate (Germany)

2013 ◽  
Vol 150 (3) ◽  
pp. 556-564 ◽  
Author(s):  
GABRIELE KÜHL ◽  
MARKUS POSCHMANN ◽  
JES RUST
Keyword(s):  
New Species ◽  
Fossil Record ◽  
Lower Devonian ◽  
Phylogenetic Position ◽  
Crown Group ◽  
Hunsrück Slate ◽  
Sea Spiders ◽  
Sea Spider

AbstractA new sea spider (Arthropoda: Pycnogonida) from the Lower Devonian Hunsrück Slate (Germany) is described asPentapantopus vogteligen. et sp. nov. This is the fifth pycnogonid species known from this exceptional fossil Lagerstätte. The most conspicuous character of the new species is the presence of five pairs of walking legs. This character, in concert with a reduced abdomen, indicates a phylogenetic position ofP. vogteliamong the crown group pycnogonids.P. vogteliextends the knowledge of fossil pycnogonid body plans and underlines the significance of the Hunsrück Slate, as this locality shows the highest diversity of sea spiders for the entire fossil record so far.

scholarly journals Evolution and palaeoecology of early turtles: a review based on recent discoveries in the Middle Jurassic

2011 ◽  
Vol 182 (3) ◽  
pp. 231-240 ◽  
Author(s):  
Jérémy Anquetin
Keyword(s):  
New Species ◽  
Middle Jurassic ◽  
Morphological Characters ◽  
Early Evolution ◽  
Bone Histology ◽  
Phylogenetic Position ◽  
Crown Group ◽  
Three New Species ◽  
First Time ◽  
Lines Of Evidence

AbstractIn recent years, no less than five new species of early turtles have been described worldwide. Among them are three new turtles from Middle Jurassic deposits that partially fill a previous temporal and morphological gap in our knowledge of the early evolution of these shelled amniotes: Heckerochelys romani, Condorchelys antiqua and Eileanchelys waldmani. For the first time, the phylogenetic position of these three new species is tested in the context of the two presently competing cladistic models of turtle evolution. The addition of these taxa to each matrix does not favour or alter any of the two opposed hypotheses. However, it is demonstrated here that, by documenting yet unknown stages in the evolution of several morphological structures, these three species give stronger support to the model of an extended phylogenetic stem for turtles. These new lines of evidence include the structure of the vomer, the position of the aditus canalis stapedio-temporalis and of the posterior opening of the canalis cavernosus, and the morphology of the processus interfenestralis of the opisthotic.Recent discoveries also reinvigorate the debate about the palaeoecology of early turtles. Whereas simple morphological characters (e.g., shell fontanelle, ligamentous bridge, flattened carapace) can be misleading, forelimb proportions and shell bone histology have led to the conclusion that most stem turtles (i.e., Proganochelys quenstedti, Palaeochersis talampayensis, Proterochersis robusta, Kayentachelys aprix and meiolaniids) were terrestrial forms. At least two out of the five recently described early turtles have been convincingly interpreted as having aquatic habits: Odontochelys semitestacea and Eileanchelys waldmani. More investigation is needed, but this will undoubtedly trigger further debate on the primitive ecology of turtles and on the origin of aquatic habits in testudines (i.e., the crown-group), respectively.

An Ordovician Pycnogonid (Sea Spider) with Serially Subdivided ‘Head’ Region

2013 ◽  
Vol 87 (3) ◽  
pp. 395-405 ◽  
Author(s):  
David M. Rudkin ◽  
Michael B. Cuggy ◽  
Graham A. Young ◽  
Deborah P. Thompson
Keyword(s):  
Disjunct Distribution ◽  
Phylogenetic Position ◽  
Complete Fusion ◽  
New Taxon ◽  
Upper Ordovician ◽  
Crown Group ◽  
Head Region ◽  
Group Position ◽  
Late Cambrian ◽  
Sea Spider

The bizarre morphology of living Pycnogonida, known colloquially as sea spiders, has long fueled dissent over their status within the arthropods. Pycnogonids figure prominently in recent analyses of anterior limb homologies and ancestral crown-group euarthropod relationships, with support for the concept of Pycnogonida as sister taxon to Euchelicerata now contested by proponents of a more basal position between Radiodonta and all other arthropods. A challenge to further elucidation of their phylogenetic position is the exceptional rarity and disjunct distribution of pycnogonids in the fossil record, due largely to their fragile unmineralized exoskeletons. New fossil discoveries therefore have the potential to add significantly to knowledge of their evolution, paleoecology, and paleobiogeography. Here we report the first known occurrence of fossil pycnogonids from rocks of Ordovician age, bridging a 65 Myr gap between controversial late Cambrian larval forms and a single documented Silurian specimen. The new taxon,Palaeomarachne granulatan. gen. n. sp., from the Upper Ordovician (ca. 450 Ma) William Lake Konservat-Lagerstätte deposit in Manitoba, Canada, is also the first reported from Laurentia. It is the only record thus far of a fossil sea spider in rocks of demonstrably shallow marine origin. Four incomplete, partially disarticulated molts represent a relatively large, robust animal with a series of five segment-like elements in a ‘head’ region that does not incorporate the first of four preserved limb-bearing trunk segments. This unique pattern may reflect the plesiomorphic condition prior to complete fusion of anterior ‘head’ elements and first trunk segment to form a cephalosoma, as seen in all eupycnogonids.Palaeomarachne granulatais interpreted as occupying a basal stem-group position in the Pycnogonida.

scholarly journals Phylogenomic Resolution of Sea Spider Diversification through Integration of Multiple Data Classes

2020 ◽  
Author(s):  
Jesús A Ballesteros ◽  
Emily V W Setton ◽  
Carlos E Santibáñez-López ◽  
Claudia P Arango ◽  
Georg Brenneis ◽  
...  
Keyword(s):  
Marine Invertebrate ◽  
Time Estimation ◽  
Sister Group ◽  
Morphological Data ◽  
Crown Group ◽  
Fossil Species ◽  
Divergence Time Estimation ◽  
Sea Spiders ◽  
Sea Spider ◽  
Molecular Divergence

Abstract Despite significant advances in invertebrate phylogenomics over the past decade, the higher-level phylogeny of Pycnogonida (sea spiders) remains elusive. Due to the inaccessibility of some small-bodied lineages, few phylogenetic studies have sampled all sea spider families. Previous efforts based on a handful of genes have yielded unstable tree topologies. Here, we inferred the relationships of 89 sea spider species using targeted capture of the mitochondrial genome, 56 conserved exons, 101 ultraconserved elements, and 3 nuclear ribosomal genes. We inferred molecular divergence times by integrating morphological data for fossil species to calibrate 15 nodes in the arthropod tree of life. This integration of data classes resolved the basal topology of sea spiders with high support. The enigmatic family Austrodecidae was resolved as the sister group to the remaining Pycnogonida and the small-bodied family Rhynchothoracidae as the sister group of the robust-bodied family Pycnogonidae. Molecular divergence time estimation recovered a basal divergence of crown group sea spiders in the Ordovician. Comparison of diversification dynamics with other marine invertebrate taxa that originated in the Paleozoic suggests that sea spiders and some crustacean groups exhibit resilience to mass extinction episodes, relative to mollusk and echinoderm lineages.

scholarly journals A Silurian short-great-appendage arthropod

2014 ◽  
Vol 281 (1778) ◽  
pp. 20132986 ◽  
Author(s):  
Derek J. Siveter ◽  
Derek E. G. Briggs ◽  
David J. Siveter ◽  
Mark D. Sutton ◽  
David Legg ◽  
...  
Keyword(s):  
Early Evolution ◽  
Phylogenetic Position ◽  
Crown Group ◽  
Hunsrück Slate ◽  
Stem Group ◽  
Sister Clade ◽  
The Uk ◽  
First Time

A new arthropod, Enalikter aphson gen. et sp. nov., is described from the Silurian (Wenlock Series) Herefordshire Lagerstätte of the UK. It belongs to the Megacheira (=short-great-appendage group), which is recognized here, for the first time, in strata younger than mid-Cambrian age. Discovery of this new Silurian taxon allows us to identify a Devonian megacheiran representative, Bundenbachiellus giganteus from the Hunsrück Slate of Germany. The phylogenetic position of megacheirans is controversial: they have been interpreted as stem chelicerates, or stem euarthropods, but when Enalikter and Bundenbachiellus are added to the most comprehensive morphological database available, a stem euarthropod position is supported. Enalikter represents the only fully three-dimensionally preserved stem-group euarthropod, it falls in the sister clade to the crown-group euarthropods, and it provides new insights surrounding the origin and early evolution of the euarthropods. Recognition of Enalikter and Bundenbachiellus as megacheirans indicates that this major arthropod group survived for nearly 100 Myr beyond the mid-Cambrian.

scholarly journals The fossil record of turtles and tortoises (Testudines) of Mexico, Central America and the Caribbean Islands, with comments on its taxonomy and paleobiogeography: a bibliographic review

2020 ◽  
Vol 37 (3) ◽  
pp. 269-283
Author(s):  
Gerardo Carbot-Chanona ◽  
Gustavo Rivera-Velázquez ◽  
Eduardo Jiménez-Hidalgo ◽  
Víctor Hugo Reynoso
Keyword(s):  
New Species ◽  
Costa Rica ◽  
Central America ◽  
Mexico City ◽  
Fossil Record ◽  
Quintana Roo ◽  
Late Triassic ◽  
Crown Group ◽  
Caribbean Islands ◽  
The Caribbean

Testudines is the crown-group that includes all living forms of turtles and their closest relatives. This group is known from the late Triassic and persists to this day. The fossil record of Testudines in Mexico is scarce and has been previously compiled in several papers. Here we present an update including all osteological and ichnological records from México and Central America. In Mexico, the Testudines fossil record extends from the Late Triassic to the Pleistocene, being widely abundant during the Pleistocene. Kinosternon and Gopherus are the best represented taxa, known from the late Miocene (Hemphillian) to the late Pleistocene (Rancholabrean). Fossil turtles are well represented in Mexico, excluding the states of Campeche, Mexico City, Colima, Guerrero, Queretaro, Quintana Roo and Sinaloa. On the contrary, the ichnological records are only known in Coahuila, Puebla and Zacatecas. In Central America there are records of fossil turtles in El Salvador, Honduras, Costa Rica and Panama, the latter being the country holding most records. Finally, nine new species have been described in the region, six for Mexico (Notoemys tlaxiacoensis, Yelmochelys rosarioae, Mexichelys coahuilaensis, Gopherus donlaloi, G. auffenbergi and G. pargensis, of which G. auffenbergi is synonymous with G. berlandieri and G. pargensis is considered a nomen vanum) and three in Central America (Rhinoclemmys nicoyama from Costa Rica, and Rhinoclemmys panamaensis and Staurotypus moschus from Panama).

scholarly journals Phylogenomic resolution of sea spider diversification through integration of multiple data classes

2020 ◽  
Author(s):  
Jesús A. Ballesteros ◽  
Emily V.W. Setton ◽  
Carlos E. Santibáñez López ◽  
Claudia P. Arango ◽  
Georg Brenneis ◽  
...  
Keyword(s):  
Marine Invertebrate ◽  
Time Estimation ◽  
Sister Group ◽  
Morphological Data ◽  
Crown Group ◽  
Fossil Species ◽  
Divergence Time Estimation ◽  
Sea Spiders ◽  
Sea Spider ◽  
Molecular Divergence

AbstractDespite significant advances in invertebrate phylogenomics over the past decade, the higher-level phylogeny of Pycnogonida (sea spiders) remains elusive. Due to the inaccessibility of some small-bodied lineages, few phylogenetic studies have sampled all sea spider families. Previous efforts based on a handful of genes have yielded unstable tree topologies. Here, we inferred the relationships of 89 sea spider species using targeted capture of the mitochondrial genome, 56 conserved exons, 101 ultraconserved elements, and three nuclear ribosomal genes. We inferred molecular divergence times by integrating morphological data for fossil species to calibrate 15 nodes in the arthropod tree of life. This integration of data classes resolved the basal topology of sea spiders with high support. The enigmatic family Austrodecidae was resolved as the sister group to the remaining Pycnogonida and the small-bodied family Rhynchothoracidae as the sister group of the robust-bodied family Pycnogonidae. Molecular divergence time estimation recovered a basal divergence of crown group sea spiders in the Ordovician. Comparison of diversification dynamics with other marine invertebrate taxa that originated in the Paleozoic suggests that sea spiders and some crustacean groups exhibit resilience to mass extinction episodes, relative to mollusk and echinoderm lineages.

scholarly journals Phylogeny and Biogeography of the Enigmatic Ghost Lineage Cylindrotomidae (Diptera: Nematocera)

2021 ◽  
Author(s):  
Iwona Kania-Kłosok ◽  
André Nel ◽  
Jacek Szwedo ◽  
Wiktoria Jordan-Stasiło ◽  
Wiesław Krzemiński
Keyword(s):  
Phylogenetic Analysis ◽  
New Species ◽  
Comparative Analysis ◽  
Sister Group ◽  
Phylogenetic Position ◽  
Crown Group ◽  
Extant Genus ◽  
Stem Group ◽  
Two New Species ◽  
Fossil Genus

Abstract Ghost lineages have always challenged the understanding of organism evolution. They participate in misinterpretations in phylogenetic, clade dating, biogeographic, and paleoecologic studies. They directly result from fossilization biases and organism biology. The Cylindrotomidae are a perfect example of an unexplained ghost lineage during the Mesozoic, as its sister family Tipulidae is already well diversified during the Cretaceous, while the oldest Cylindrotomidae are Paleogene representatives of the extant genus Cylindrotoma and of the enigmatic fossil genus Cyttaromyia. Here We clarify the phylogenetic position of Cyttaromyia in the stem group of the whole family, suggesting that the crown group of the Cylindrotomidae began to diversify during the Cenozoic, unlike their sister group Tipulidae. We make a comparative analysis of all species in Cyttaromyia, together with the descriptions of the two new species, C. gelhausi sp. nov. and C. freiwaldi sp. nov., and the revision of C. obdurescens. The cylindrotomid biogeography seems to be incongruent with the phylogenetic analysis, the apparently most derived subfamily Stibadocerinae having apparently a ‘Gondwanan’ distribution, with some genera only known from Australia or Chile, while the most inclusive Cylindrotominae are Holarctic.

scholarly journals Evolution and palaeoecology of early turtles: a review based on recent discoveries in the Middle Jurassic

2017 ◽  
Author(s):  
Jérémy Anquetin
Keyword(s):  
New Species ◽  
Middle Jurassic ◽  
Phylogenetic Analyses ◽  
Morphological Characters ◽  
Phylogenetic Position ◽  
Crown Group ◽  
Stem Group ◽  
Three New Species ◽  
First Time ◽  
Lines Of Evidence

In recent years, no less than five new species of stem-group turtles have been described worldwide. Among them are three new turtles from Middle Jurassic deposits that partially fill a previous temporal and morphological gap in our knowledge of the early evolution of these shelled amniotes: Heckerochelys romani, Condorchelys antiqua and Eileanchelys waldmani. For the first time, the phylogenetic position of these three new species is tested in the context of the two presently competing cladistic models of turtle evolution. The addition of these taxa to each matrix does not favour or alter any of the two opposed hypotheses. However, it is demonstrated here that, by documenting yet unknown stages in the evolution of several morphological structures, these three species give stronger support to the model of an extended phylogenetic stem for turtles. These new lines of evidence include the structure of the vomer, the position of the aditus canalis stapedio-temporalis and of the posterior opening of the canalis cavernosus, and the morphology of the processus interfenestralis of the opisthotic. These characters should be considered for future phylogenetic analyses of turtle interrelationships.Recent discoveries also reinvigorate the debate about the palaeoecology of early turtles. Whereas simple morphological characters (e.g., shell fontanelle, ligamentous bridge, flattened carapace) can be misleading, forelimb proportions and shell bone histology have led to the conclusion that most stem turtles (i.e., Proganochelys quenstedti, Palaeochersis talampayensis, Proterochersis robusta, Kayentachelys aprix and meiolaniids) were terrestrial forms. On the contrary, it is generally accepted that crown-group turtles are ancestrally aquatic. Among the five recently described stem-group turtles, Odontochelys semitestacea and Eileanchelys waldmani have been convincingly interpreted as having aquatic habits, which suggests that basal turtles were ecologically diverse. More investigation is needed, but this will undoubtedly trigger further debate on the primitive ecology of turtles and on the origin of aquatic habits in Testudines (i.e., the crown-group), respectively.

scholarly journals A Small Representative of the Phalacrocoracoidea (Cormorants and Anhingas) from the Late Oligocene of Germany

The Condor ◽  
2007 ◽  
Vol 109 (4) ◽  
pp. 929-942
Author(s):  
Gerald Mayr
Keyword(s):  
New Species ◽  
Fossil Record ◽  
Sister Group ◽  
Sister Group Relationship ◽  
Late Oligocene ◽  
Crown Group ◽  
Stem Lineage ◽  
Early Neogene ◽  
Fossil Site ◽  
A New Species

AbstractI describe a skeleton of a cormorant-like bird from Enspel, a late Oligocene (24.7 mya) fossil site in Germany, which is assigned to a new species, ?Borvocarbo stoeffelensis, sp. nov. The specimen constitutes the earliest described and most completely preserved fossil record of the Phalacrocoracoidea, the clade including Anhingidae (anhingas) and Phalacrocoracidae (cormorants). ?B. stoeffelensis shares derived features with cormorants that are absent in anhingas. Despite its cormorant-like overall morphology, an assignment to the stem lineage of Phalacrocoracidae is not straightforward, because the new species is also distinguished from crown group representatives of the clade (Anhingidae + Phalacrocoracidae) by presumably plesiomorphic features. The morphology displayed by ?B. stoeffelensis places a caveat on the assignment to the Phalacrocoracidae of other less completely known Paleogene and early Neogene taxa. Plesiomorphic features shared by ?B. stoeffelensis and extant “microcormorants” (sensu Siegel-Causey 1988) support a sister group relationship between “Microcarbo” spp. and all other extant Phalacrocoracidae.

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