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.

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.

Saetaspongia sponges from the Cambrian (Stage 4) Balang Formation of Guizhou, China

2021 ◽  
pp. 1-13
Author(s):  
Chenchen Ling ◽  
Jin Peng ◽  
Hui Zhang ◽  
Yifan Wang ◽  
Yunbin Shao ◽  
...  
Keyword(s):  
Phylogenetic Position ◽  
New Taxon ◽  
Crown Group ◽  
Critical Feature ◽  
Additional Specimen ◽  
Fossil Evidence ◽  
New Information ◽  
Class Level ◽  
Stage 4 ◽  
New Material

Abstract Saetaspongia so far cannot be confidently assigned to any class-level crown group. Clarifying its phylogenetic position requires new information provided by more detailed studies of previously described and/or new material. Some sponge fossils with the typical skeletal architecture of Saetaspongia have recently been recognized in the Cambrian (Stage 4) Balang Biota of Guizhou, China, including S. jianhensis new species and S. cf. S. densa. The new taxon is characterized by the following features: spicules are fine monaxons and are inclined to be loosely to densely arranged into plumose arrays; skeleton is composed primarily of one major plumose bundle, with an uncertain number (perhaps two) of small plumose arrays; and primary skeleton is occasionally interspersed with some irregularly oriented individual spicules. An additional specimen consisting of large monaxons, with plumose structures and overlying irregular coarse monaxons, closely fits the description and illustrations of previously described S. cf. S. densa. By combining information from previous studies and the present research, fossil evidence indicates that the plumose architecture is a critical feature diagnostic of Saetaspongia and that there are no hexactine-based spicules in this genus. The new material from the Balang Biota further supports the notion that Saetaspongia has a protomonaxonid rather than a hexactinellid affinity. Fossil evidence suggests that Saetaspongia had a wide biogeographic distribution during the early Cambrian and the stratigraphic distribution of this genus extends up to Stage 4. UUID: http://zoobank.org/e9ca5e4a-134c-4daa-9266-19085e32614f.

A giant within Carpocorini (Hemiptera: Heteroptera: Pentatomidae): Description of Adustonotus graziae sp. nov.

Zootaxa ◽  
2021 ◽  
Vol 4958 (1) ◽  
pp. 489-502
Author(s):  
FILIPE MICHELS BIANCHI
Keyword(s):  
Morphological Characters ◽  
The Other ◽  
Total Evidence ◽  
Valid Species ◽  
Phylogenetic Position ◽  
New Taxon ◽  
Large Size ◽  
Internal Genitalia ◽  
Evidence Analysis ◽  
Heteroptera Pentatomidae

The Carpocorini are distributed worldwide, and it is one of the most speciose tribes within the Pentatomidae with 127 genera and more than 500 valid species. Recently, Adustonotus Bianchi was described to contain eight species formerly placed within Euschistus Dallas. Among them, Adustonotus grandis (Rolston) and Adustonotus latus (Dallas) are remarkable for their large size. Herein, the phylogenetic position of a new taxon is inferred by a total evidence analysis based on 85 morphological characters and four molecular markers. Adustonotus graziae sp. nov. is described, and is recovered in a polytomic lineage, including A. grandis and A. latus. These species share a solid combination of features that enable them to be separated from the other Adustonotus species (e.g., large size, the humeral angles spatulate and exceptionally produced, and the capsula seminalis shortened). Illustrations of external and internal genitalia, and a distributional map are provided. 

Ichthyosaurs from the Upper Triassic (Carnian–Norian) of the New Siberian Islands, Russian Arctic, and their implications for the evolution of the ichthyosaurian basicranium and vertebral column

2021 ◽  
pp. 1-24
Author(s):  
Nikolay G. ZVERKOV ◽  
Dmitry V. GRIGORIEV ◽  
Andrzej S. WOLNIEWICZ ◽  
Alexey G. KONSTANTINOV ◽  
Evgeny S. SOBOLEV
Keyword(s):  
Vertebral Column ◽  
Cervical Vertebrae ◽  
Upper Triassic ◽  
Late Triassic ◽  
Phylogenetic Position ◽  
New Taxon ◽  
Russian Arctic ◽  
Micro Computed Tomography ◽  
New Siberian Islands ◽  
Group Relationships

ABSTRACT The first ichthyosaurian specimens discovered from the Upper Triassic of the Russian Arctic (Kotelny Island, New Siberian Islands) are described herein. They include the remains of large- to small-bodied ichthyosaurians originating from six stratigraphic levels spanning the lower Carnian to middle Norian. The material is mostly represented by isolated vertebrae and ribs, which are not possible to accurately diagnose, but also includes specimens comprising associated vertebrae and a fragmentary skeleton that preserves cranial remains (parabasisphenoid, fragmentary quadrate, partial mandible and hyoids). Based on vertebral and rib morphology, we identify the specimens as representatives of the following taxonomic groups: large-bodied shastasaurids, medium-sized indeterminate ichthyosaurians with a single rib facet in the presacral centra, and small euichthyosaurians with double rib facets present throughout the presacral vertebrae that likely represent toretocnemids and/or basal parvipelvians. In addition, the cranial and mandibular remains preserved in one of the specimens, ZIN PH 5/250, were studied using micro-computed tomography. Its mandible is highly similar to that of toretocnemids, whereas the parabasisphenoid demonstrates a peculiar combination of both plesiomorphic and derived character states, providing the first detailed data on this cranial element in a Late Triassic ichthyosaurian. Furthermore, the specimen also demonstrates a distinctive condition of rib articulation in the anteriormost presacral (cervical) vertebrae, which together with other features allows for the erection of a new taxon – Auroroborealia incognita gen. et sp. nov. Although the phylogenetic position of this taxon is uncertain due to its fragmentary nature, its anatomy, indicating toretocnemid or parvipelvian affinities, further supports the previously hypothesised sister-group relationships between these two clades. The morphology of the parabasisphenoid and vertebral column of the new taxon is discussed in broader contexts of the patterns of evolution of these skeletal regions in ichthyosaurs.

New insights into the evolution of lateral compound eyes in Palaeozoic horseshoe crabs

2019 ◽  
Vol 187 (4) ◽  
pp. 1061-1077 ◽  
Author(s):  
Russell D C Bicknell ◽  
Lisa Amati ◽  
Javier Ortega-Hernández
Keyword(s):  
Convincing Evidence ◽  
Limulus Polyphemus ◽  
Phylogenetic Position ◽  
Compound Eyes ◽  
Crown Group ◽  
Widespread Occurrence ◽  
Eye Evolution ◽  
Stem Group ◽  
Lateral Eye ◽  
Horseshoe Crabs

Abstract Vision allows animals to interact with their environment. Aquatic chelicerates dominate the early record of lateral compound eyes among non-biomineralizing crown-group euarthropods. Although the conservative morphology of lateral eyes in Xiphosura is potentially plesiomorphic for Euarthropoda, synziphosurine eye organization has received little attention despite their early diverging phylogenetic position. Here, we re-evaluate the fossil evidence for lateral compound eyes in the synziphosurines Bunodes sp., Cyamocephalus loganensis, Legrandella lombardii, Limuloides limuloides, Pseudoniscus clarkei, Pseudoniscus falcatus and Pseudoniscus roosevelti. We compare these data with lateral eyes in the euchelicerates Houia yueya, Kasibelinurus amicorum and Lunataspis aurora. We find no convincing evidence for lateral eyes in most studied taxa, and Pseudoniscus roosevelti and Legrandella lombardii are the only synziphosurines with this feature. Our findings support two scenarios for euchelicerate lateral eye evolution. The elongate-crescentic lateral eyes of Legrandella lombardii might represent the ancestral organization, as suggested by the phylogenetic position of this taxon in stem-group Euchelicerata. Alternatively, the widespread occurrence of kidney-shaped lateral eyes in stem-group Xiphosura and stem-group Arachnida could represent the plesiomorphic condition; Legrandella lombardii eyes would therefore be derived. Both evolutionary scenarios support the interpretation that kidney-shaped lateral eyes are ancestral for crown-group Euchelicerata and morphologically conserved in extant Limulus polyphemus.

First plesiosaur remains from the lower Cretaceous of the Neuquén Basin, Argentina

2003 ◽  
Vol 77 (4) ◽  
pp. 784-789 ◽  
Author(s):  
Dario G. Lazo ◽  
Marcela Cichowolski
Keyword(s):  
Lower Cretaceous ◽  
Sister Group ◽  
Monophyletic Group ◽  
Phylogenetic Position ◽  
Crown Group ◽  
Marine Reptiles ◽  
Stem Group ◽  
Neuquen Basin ◽  
Neuquén Basin

Plesiosaurs constitute a monophyletic group whose stratigraphical range is uppermost Triassic to uppermost Cretaceous (Brown, 1981). They were large predatory marine reptiles, highly adapted for submarine locomotion, with powerful paddle-like limbs and heavily reinforced limb girdles (Saint-Seine, 1955; Romer, 1966; Carroll, 1988; Benton, 1990). The Plesiosauria clade belongs to the Sauropterygia, which has recently been hypothesized as the sister-group of the Ichthyosauria. Together with that clade they form the Euryapsida (Caldwell, 1997). The Sauropterygia can be subdivided into relatively plesiomorphic stem-group taxa from the Triassic (Placodonts, Nothosauroids, and Pistosauroids), and the obligatorily marine crown-group Plesiosauria (Rieppel, 1999). Plesiosaurs are traditionally divided into two superfamilies: Plesiosauroidea, with usually small heads and long necks; and Pliosauroidea, with larger heads and shorter necks (Welles, 1943; Persson, 1963; Brown, 1981). Plesiosauroidea contains three families: Plesiosauridae, Cryptoclididae, and Elasmosauridae (Brown, 1981; Brown and Cruickshank, 1994). The validity of the Polycotylidae Cope, 1869, has long been questioned and its phylogenetic position among Plesiosauria debated, as many consider it to be related to the Pliosauridae or to be a sister-group of the Elasmosauridae (Sato and Storrs, 2000; O'Keefe, 2001).

The sorediate variety of Sclerophytomyces circumscriptus

2005 ◽  
Vol 37 (4) ◽  
pp. 285-289 ◽  
Author(s):  
Laurens B. SPARRIUS ◽  
Peter W. JAMES ◽  
M. Ann ALLEN
Keyword(s):  
Canary Islands ◽  
Phylogenetic Position ◽  
New Taxon ◽  
British Isles ◽  
Acid Rock ◽  
Distribution And Ecology

The sorediate variety of Sclerophytomyces circumscriptus (Taylor) Sparrius & P. James (Roccellaceae, Arthoniales) is described from sheltered, acid rock along Europe's western coasts and the Atlantic islands. This sorediate taxon is reported from the British Isles, Ireland, France, Spain, Portugal, the Azores and the Canary Islands. A description of the morphology, distribution and ecology is provided. The phylogenetic position of the new taxon is discussed, as well as nomenclatural and orthographic issues. The name Sclerophytomyces is proposed as an orthographic correction of the published name Sclerophytonomyces.

A new Crocus L. (Iridaceae) species from SE Turkey, based on morphological and molecular data

Phytotaxa ◽  
2015 ◽  
Vol 239 (3) ◽  
pp. 223 ◽  
Author(s):  
Osman Erol ◽  
Doerte Harpke ◽  
Hasan Yıldırım
Keyword(s):  
Phylogenetic Analyses ◽  
Type Specimen ◽  
Morphological Characters ◽  
Molecular Data ◽  
Nuclear Ribosomal Dna ◽  
Phylogenetic Position ◽  
Full Description ◽  
New Taxon ◽  
Internal Transcribed Spacer Region ◽  
Se Turkey

Crocus musagecitii is described as a new species. Diagnostic morphological characters, a full description and detailed illustrations are provided on the basis of the type specimen and wild specimens. Morphologically, C. musagecitii is close to Crocus biflorus subsp. pseudonubigena. Crocus musagecitii differs from C. biflorus subsp. pseudonubigena by the lack of stripes or narrow purplish tongue on outside of outer tepals, wider tepals, and homogenously yellow anthers. In order to clarify the phylogenetic position of this species within the Crocus adamii species complex, we sequenced the internal transcribed spacer region (ITS: ITS1 + 5.8SrDNA + ITS2) and 5’ external transcribed spacer (ETS) of the nuclear ribosomal DNA (rDNA). A phylogenetic tree obtained by Bayesian phylogenetic inference is given. Phylogenetic analyses revealed that the new taxon is close to C. munzurensis. Crocus musagecitii differs from its phylogenetically closest relative C. munzurensis by the corm tunics (C. musagecitii: coriaceus; C. munzurensis: membranous), the number of leaves (C. musagecitii: up to 8; C. munzurensis: up to 4) and non-hairy leaf margins.

scholarly journals New turtle remains from the Late Cretaceous of Monte Alto-SP, Brazil, including cranial osteology, neuroanatomy and phylogenetic position of a new taxon

PalZ ◽  
2018 ◽  
Vol 92 (3) ◽  
pp. 481-498 ◽  
Author(s):  
Gabriel S. Ferreira ◽  
Fabiano V. Iori ◽  
Guilherme Hermanson ◽  
Max C. Langer
Keyword(s):  
Late Cretaceous ◽  
Phylogenetic Position ◽  
New Taxon ◽  
Cranial Osteology

scholarly journals Phylogenetic relationships among extinct and extant turtles: the position of Pleurodira and the effects of the fossils on rooting crown-group turtles

2010 ◽  
Vol 79 (3) ◽  
pp. 93-106 ◽  
Author(s):  
Juliana Sterli
Keyword(s):  
Phylogenetic Relationships ◽  
Sister Group ◽  
Molecular Data ◽  
Morphological Data ◽  
Phylogenetic Position ◽  
Separate Analysis ◽  
Crown Group ◽  
Rapid Radiation ◽  
Present Contribution ◽  
Origin And Evolution

The origin and evolution of the crown-group of turtles (Cryptodira + Pleurodira) is one of the most interesting topics in turtle evolution, second perhaps only to the phylogenetic position of turtles among amniotes. The present contribution focuses on the former problem, exploring the phylogenetic relationships of extant and extinct turtles based on the most comprehensive phylogenetic dataset of morphological and molecular data analyzed to date. Parsimony analyses were conducted for different partitions of data (molecular and morphological) and for the combined dataset. In the present analysis, separate analyses of the molecular data always retrieve Pleurodira allied to Trionychia. Separate analysis of the morphological dataset, by contrast, depicts a more traditional arrangement of taxa, with Pleurodira as the sister group of Cryptodira, being Chelonioidea the most basal cryptodiran clade. The simultaneous analysis of all available data retrieves all major extant clades as monophyletic, except for Cryptodira given that Pleurodira is retrieved as the sister group of Trionychia. The paraphyly of Cryptodira is an unorthodox result, and is mainly caused by the combination of two factors. First, the molecular signal allies Pleurodira and Trionychia. Second, the morphological data with extinct taxa locates the position of the root of crown-group Testudines in the branch leading to Chelonioidea. This study highlights major but poorly explored topics of turtle evolution: the alternate position of Pleurodira and the root of crown turtles. The diversification of crown turtles is characterized by the presence of long external branches and short internal branches (with low support for the internal nodes separating the major clades of crown turtles), suggesting a rapid radiation of this clade. This rapid radiation is also supported by the fossil record, because soon after the appearance of the oldest crown-group turtles (Middle-Late Jurassic of Asia) the number and diversity of turtles increases remarkably. This evolutionary scenario of a rapid diversification of modern turtles into the major modern lineages is likely the reason for the difficulty in determining the interrelationships and the position of the root of crown-group turtles.

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