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 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.

scholarly journals Genetic diversity of the genus Terfezia (Pezizaceae, Pezizales): New species and new record from North Africa

Phytotaxa ◽  
2018 ◽  
Vol 334 (2) ◽  
pp. 183 ◽  
Author(s):  
Fatima El-Houaria ZITOUNI-HAOUAR ◽  
JUAN RAMÓN CARLAVILLA ◽  
GABRIEL MORENO ◽  
JOSÉ LUIS MANJÓN ◽  
ZOHRA FORTAS
Keyword(s):  
New Species ◽  
North Africa ◽  
Phylogenetic Analyses ◽  
Ribosomal Subunit ◽  
Morphological Characters ◽  
Phylogenetic Position ◽  
Unique Combination ◽  
Large Ribosomal Subunit ◽  
First Time ◽  
A New Species

Morphological and phylogenetic analyses of large ribosomal subunit (28S rDNA) and internal transcribed spacer (ITS rDNA) of Terfezia samples collected from several bioclimatic zones in Algeria and Spain revealed the presence of six distinct Terfezia species: T. arenaria, T. boudieri, T. claveryi; T. eliocrocae (reported here for the first time from North Africa), T. olbiensis, and a new species, T. crassiverrucosa sp. nov., proposed and described here, characterized by its phylogenetic position and unique combination of morphological characters. A discussion on the unresolved problems in the taxonomy of the spiny-spored Terfezia species is conducted after the present results.

scholarly journals A revision of dragon millipedes I: genus Desmoxytes Chamberlin, 1923, with the description of eight new species (Diplopoda, Polydesmida, Paradoxosomatidae)

ZooKeys ◽  
2018 ◽  
Vol 761 ◽  
pp. 1-177 ◽  
Author(s):  
Ruttapon Srisonchai ◽  
Henrik Enghoff ◽  
Natdanai Likhitrakarn ◽  
Somsak Panha
Keyword(s):  
New Species ◽  
Southeast Asia ◽  
Present Article ◽  
Phylogenetic Analyses ◽  
Morphological Characters ◽  
New Genera ◽  
Distribution Maps ◽  
New Synonyms ◽  
Molecular Phylogenetic ◽  
First Time

The dragon millipede genusDesmoxytess.l. is split into five genera, based on morphological characters and preliminary molecular phylogenetic analyses. The present article includes a review ofDesmoxytess.s., while future articles will deal withHylomusCook and Loomis, 1924 and three new genera which preliminarily are referred to as the ‘acantherpestes’, ‘gigas’, and ‘spiny’ groups. Diagnostic morphological characters of each group are discussed.Hylomusis resurrected as a valid genus and the following 33 species are assigned to it:H.asper(Attems, 1937),comb. n.,H.cattienensis(Nguyen, Golovatch & Anichkin, 2005),comb. n.,H.cervarius(Attems, 1953),comb. n.,H.cornutus(Zhang & Li, 1982),comb. n.,H.dracoCook & Loomis, 1924,stat. rev.,H.enghoffi(Nguyen, Golovatch & Anichkin, 2005),comb. n.,H.eupterygotus(Golovatch, Li, Liu & Geoffroy, 2012),comb. n.,H.getuhensis(Liu, Golovatch & Tian, 2014),comb. n.,H.grandis(Golovatch, VandenSpiegel & Semenyuk, 2016),comb. n.,H.hostilis(Golovatch & Enghoff, 1994),comb. n.,H.jeekeli(Golovatch & Enghoff, 1994),comb. n.,H.lingulatus(Liu, Golovatch & Tian, 2014),comb. n.,H.laticollis(Liu, Golovatch & Tian, 2016),comb. n.,H.longispinus(Loksa, 1960),comb. n.,H.lui(Golovatch, Li, Liu & Geoffroy, 2012),comb. n.,H.minutuberculus(Zhang, 1986),comb. n.,H.nodulosus(Liu, Golovatch & Tian, 2014),comb. n.,H.parvulus(Liu, Golovatch & Tian, 2014),comb. n.,H.phasmoides(Liu, Golovatch & Tian, 2016),comb. n.,H.pilosus(Attems, 1937),comb. n.,H.proximus(Nguyen, Golovatch & Anichkin, 2005),comb. n.,H.rhinoceros(Likhitrakarn, Golovatch & Panha, 2015),comb. n.,H.rhinoparvus(Likhitrakarn, Golovatch & Panha, 2015),comb. n.,H.scolopendroides(Golovatch, Geoffroy & Mauriès, 2010),comb. n.,H.scutigeroides(Golovatch, Geoffroy & Mauriès, 2010),comb. n.,H.similis(Liu, Golovatch & Tian, 2016),comb. n.,H.simplex(Golovatch, VandenSpiegel & Semenyuk, 2016),comb. n.,H.simplipodus(Liu, Golovatch & Tian, 2016),comb. n.,H.specialis(Nguyen, Golovatch & Anichkin, 2005),comb. n.,H.spectabilis(Attems, 1937),comb. n.,H.spinitergus(Liu, Golovatch & Tian, 2016),comb. n.,H.spinissimus(Golovatch, Li, Liu & Geoffroy, 2012),comb. n.andH.variabilis(Liu, Golovatch & Tian, 2016),comb. n.Desmoxytess.s. includes the following species:D.breviverpaSrisonchai, Enghoff & Panha, 2016;D.cervina(Pocock,1895);D.delfae(Jeekel, 1964);D.desSrisonchai, Enghoff & Panha, 2016;D.pinnasqualiSrisonchai, Enghoff & Panha, 2016;D.planata(Pocock, 1895);D.purpuroseaEnghoff, Sutcharit & Panha, 2007;D.takensisSrisonchai, Enghoff & Panha, 2016;D.taurina(Pocock, 1895);D.terae(Jeekel, 1964), all of which are re-described based mainly on type material. Two new synonyms are proposed:DesmoxytespterygotaGolovatch & Enghoff, 1994,syn. n.(=Desmoxytescervina(Pocock, 1895)),DesmoxytesrubraGolovatch & Enghoff, 1994,syn. n.(=Desmoxytesdelfae(Jeekel, 1964)). Six new species are described from Thailand:D.aurataSrisonchai, Enghoff & Panha,sp. n.,D.corythosaurusSrisonchai, Enghoff & Panha,sp. n.,D.eurosSrisonchai, Enghoff & Panha,sp. n.,D.flabellaSrisonchai, Enghoff & Panha,sp. n.,D.golovatchiSrisonchai, Enghoff & Panha,sp. n.,D.octoconigeraSrisonchai, Enghoff & Panha,sp. n., as well as one from Malaysia:D.perakensisSrisonchai, Enghoff & Panha,sp. n., and one from Myanmar:D.waepyanensisSrisonchai, Enghoff & Panha,sp. n.The species can mostly be easily distinguished by gonopod structure in combination with other external characters; some cases of particularly similar congeners are discussed. All species ofDesmoxytess.s. seem to be endemic to continental Southeast Asia (except the ‘tramp’ speciesD.planata). Some biological observations (relationship with mites, moulting) are recorded for the first time. Complete illustrations of external morphological characters, an identification key, and distribution maps of all species are provided.

scholarly journals Indopolystoma n. gen. (Monogenea, Polystomatidae) with the description of three new species and reassignment of eight known Polystoma species from Asian frogs (Anura, Rhacophoridae)

Parasite ◽  
2019 ◽  
Vol 26 ◽  
pp. 67
Author(s):  
Amira Chaabane ◽  
Olivier Verneau ◽  
Louis Du Preez
Keyword(s):  
New Species ◽  
New Genus ◽  
Phylogenetic Analyses ◽  
The Body ◽  
Molecular Dating ◽  
Phylogenetic Position ◽  
Morphological Evidence ◽  
Freshwater Turtles ◽  
Three New Species ◽  
Japan And China

The polystomes (Monogenea, Polystomatidae) radiated across semi-aquatic tetrapods including all three amphibian orders, freshwater turtles and the hippopotamus. Prior to this study, phylogenetic analyses revealed that the most diverse and widespread genus, Polystoma, was not monophyletic; a lineage comprising four undescribed species from the bladder of Zhangixalus spp. (Rhacophoridae) in Asia occupied a deep phylogenetic position. Regarding vicariance biogeography and molecular dating, the origin of this lineage is correlated with the breakup of Gondwanaland in the Mesozoic period. Based on a Bayesian analysis of four concatenated genes (18S, 28S, COI and 12S) and morphological evidence, one new genus, Indopolystoma n. gen., and three new species, sampled in Japan and China, are described here: Indopolystoma viridi n. sp. from Z. viridis of Japan, Indopolystoma elongatum n. sp. from Z. arboreus of Japan, and Indopolystoma parvum n. sp. from Z. omeimontis of China. Indopolystoma is unique amongst polystome genera infecting anurans by possessing a small haptor relative to the body size, posteriormost marginal hooklet C1 much bigger than hooklets C2–C8 with conspicuous broad blade and guard and a pair of hamuli lacking a deep notch. Eight species of Asian Polystoma, all from rhacophorids, are transferred as Indopolystoma carvirostris (Fan, Li & He, 2008) n. comb., I. hakgalense (Crusz & Ching, 1975) n. comb., I. indicum (Diengdoh & Tandon, 1991) n. comb., I. leucomystax (Zhang & Long, 1987) n. comb., I. mutus (Meng, Song & Ding, 2010) n. comb., I. pingbianensis (Fan, Wang & Li, 2004) n. comb., I. rhacophori (Yamaguti, 1936) n. comb., and I. zuoi (Shen, Wang & Fan, 2013) n. comb.

scholarly journals Seek and ye shall find: new species and new records of Microporella (Bryozoa, Cheilostomatida) in the Mediterranean

ZooKeys ◽  
2021 ◽  
Vol 1053 ◽  
pp. 1-42
Author(s):  
Emanuela Di Martino ◽  
Antonietta Rosso
Keyword(s):  
New Species ◽  
New Records ◽  
Intraspecific Variability ◽  
Morphological Characters ◽  
Additional Species ◽  
New Material ◽  
The Mediterranean ◽  
Three New Species ◽  
First Time ◽  
Submarine Caves

The Mediterranean specimens of the genus Microporella collected from shallow water habitats during several surveys and cruises undertaken mostly off the Italian coast are revised. As a result of the disentanglement of the M. ciliata complex and the examination of new material, three new species, M. bicollarissp. nov., M. ichnusaesp. nov., and M. pachyspinasp. nov., are described from submarine caves or associated with seagrasses and algae. An additional species Microporella sp. A, distinct by its finely reticulate ascopore, is described but left in open nomenclature owing to the limitations of a single infertile fragment. After examination of all available material, based on their identical zooidal morphology, the genus Diporula is regarded as junior synonym of Microporella and the combination Microporella verrucosa is resurrected as first suggested by Neviani in 1896. Fenestrulina joannae is also reassigned to Microporella. The availability of a large number of colonies of the above-mentioned and other species already well known from the area (i.e., M. appendiculata, M. ciliata, and M. modesta), allowed the assessment of their high intraspecific variability as well as the observation, for the first time, of some morphological characters including ancestrulae, early astogeny, and kenozooids. Finally, M. modesta, in spite of M. ciliata as defined by the neotype selected by Kukliński & Taylor in 2008, appears to be the commonest species in the basin.

scholarly journals Morphological phylogenetic analyses and taxonomic revision of the Panorpa davidi group (Mecoptera: Panorpidae)

2021 ◽  
Vol 79 ◽  
pp. 309-342
Author(s):  
Li Ning ◽  
Ji-Shen Wang ◽  
Bao-Zhen Hua
Keyword(s):  
New Species ◽  
Maximum Likelihood ◽  
Maximum Parsimony ◽  
Phylogenetic Analyses ◽  
Taxonomic Revision ◽  
Morphological Characters ◽  
Monophyletic Group ◽  
Key To Species ◽  
First Time

Abstract The Chinese Panorpa species without anal horn are normally assigned to the Panorpa davidi group. Here, we taxonomically revise the P. davidi group, which currently includes 17 known species and four new species: P. gaokaii sp. nov., P. huayuani sp. nov., P. uncinata sp. nov. and P. yaoluopingensis sp. nov. Panorpa shanyangensis Chou & Wang, 1981 and P. sexspinosa zhongnanensis Chou & Ran, 1981 are treated as junior synonyms of P. sexspinosa Cheng, 1949. We describe for the first time the male of P. stigmosa Zhou, 2006, and the females of P. curva Carpenter, 1938, P. davidi Navás, 1908, P. difficilis Carpenter, 1938, P. fructa Cheng, 1949, and P. jinchuana Hua, Sun & Li, 2001. A key to species of the group is provided. Phylogenetic analyses of maximum parsimony and maximum likelihood based on 79 morphological characters show that the newly defined P. davidi group is a well-supported monophyletic group and is sister to the genus Cerapanorpa Gao, Ma & Hua, 2016.

scholarly journals Three new species and new records of the genus Centromerus (Araneae, Linyphiidae) from Italy

2020 ◽  
Author(s):  
Francesco Ballarin ◽  
Paolo Pantini
Keyword(s):  
New Species ◽  
New Records ◽  
Morphological Characters ◽  
Congeneric Species ◽  
Male And Female ◽  
Three New Species ◽  
First Time

Three new species of the genus Centromerus from Italy, C. tongiorgii sp. nov., C. hanseni sp. nov., and C. gatoi sp. nov., are described for the first time on the basis of both male and female specimens. Their relationships with other congeneric species, as well as their diagnoses, are discussed using morphological characters. New records of poorly known species of Centromerus from Italy are furthermore reported. Among them, C. desmeti Bosmans, 1986 is reported for the first time for the Italian fauna and for continental Europe.

scholarly journals Camerobiid mites (Acariformes: Raphignathina: Camerobiidae) inhabiting epiphytic bromeliads and soil litter of tropical dry forest with analysis of setal homology in the genus Neophyllobius

2016 ◽  
Author(s):  
Ricardo Paredes-León ◽  
Angélica María Corona-López ◽  
Alejandro Flores-Palacios ◽  
Víctor Hugo Toledo-Hernández
Keyword(s):  
New Species ◽  
Forest Floor ◽  
Tropical Dry Forest ◽  
Morphological Characters ◽  
Dry Forest ◽  
The Third ◽  
Adult Females ◽  
Three New Species ◽  
First Time ◽  
Epiphytic Bromeliads

A survey of the camerobiid mites living on epiphytic bromeliads and the forest floor of a Mexican tropical dry forest was carried out. We found three new species of the genus Neophyllobius, which are described in this paper; the first two, namely N. cibyci sp. nov. and N. tepoztlanensis sp. nov., were both found inhabiting bromeliads (Tillandsia spp.) and living on two tree species (Quercus obtusata and Sapium macrocarpum); the third, N. tescalicola sp. nov., was found in soil and litter under Q. obtusata. These three new species can be differentiated from other species in the genus by a combination of morphological characters in adult females, mainly those setae on femora and genua I. The idiosoma and leg setal ontogeny of a camerobiid mite is presented for the first time in this paper, illustrating chaetotaxic notations and their relative positions in N. cibyci sp. nov. larva, protonymph and adults (female and male), and establishing setal homologies among instars. Setal homology with other species in the cohort Raphignathina is briefly discussed. Additionally, a compilation and an identification key to all known species of camerobiid mites in Mexico is provided.

Thelopsis challenges the generic circumscription in the Gyalectaceae and brings new insights to the taxonomy of Ramonia

2021 ◽  
Vol 53 (1) ◽  
pp. 45-61
Author(s):  
Damien Ertz ◽  
Neil Sanderson ◽  
Marc Lebouvier
Keyword(s):  
Phylogenetic Analyses ◽  
Saint Paul ◽  
Morphological Characters ◽  
Systematic Position ◽  
Sister Species ◽  
Phylogenetic Position ◽  
Generic Type ◽  
The Family ◽  
Fungal Dna ◽  
First Time

AbstractThe genus Thelopsis was classified in the family Stictidaceae but its systematic position has never been investigated by molecular methods. In order to determine its family placement and to test its monophyly, fungal DNA of recent collections of Thelopsis specimens was sequenced. Phylogenetic analyses using nuLSU, RPB2 and mtSSU sequences reveal that members of Thelopsis form a monophyletic group within the genus Gyalecta as currently accepted. The placement of Thelopsis, including the generic type T. rubella, within the genus Gyalecta challenges the generic circumscription of this group because Thelopsis is well recognized by the combination of morphological characters: perithecioid ascomata, well-developed periphysoids, polysporous asci and small, few-septate ellipsoid-oblong ascospores. The sterile sorediate Opegrapha corticola is also placed in the Gyalectaceae as sister species to Thelopsis byssoidea + T. rubella. Ascomata of O. corticola are illustrated for the first time and support its placement in the genus Thelopsis. The hypothesis that O. corticola might represent the sorediate fertile morph of T. rubella is not confirmed because the species is phylogenetically and morphologically distinct. Thelopsis is recovered as polyphyletic, with T. melathelia being placed as sister species to Ramonia. The new combinations Thelopsis corticola (Coppins & P. James) Sanderson & Ertz comb. nov. and Ramonia melathelia (Nyl.) Ertz comb. nov. are introduced and a new species of Gyalecta, G. amsterdamensis Ertz, is described from Amsterdam and Saint-Paul Islands, characterized by a sterile thallus with discrete soralia. Petractis luetkemuelleri and P. nodispora are accommodated in the new genus Neopetractis, differing from the generic type (P. clausa) by having a different phylogenetic position and a different photobiont. Francisrosea bicolor Ertz & Sanderson gen. & sp. nov. is described for a sterile sorediate lichen somewhat similar to Opegrapha corticola but having an isolated phylogenetic position as sister to a clade including Gyalidea praetermissa and the genera Neopetractis and Ramonia. Gyalecta farlowii, G. nidarosiensis and G. carneola are placed in a molecular phylogeny for the first time. The taxonomic significance of morphological characters in Gyalectaceae is discussed.

scholarly journals A primitive starfish ancestor from the Early Ordovician of Morocco reveals the origin of crown group Echinodermata

2017 ◽  
Author(s):  
Aaron W. Hunter ◽  
Javier Ortega-Hernández
Keyword(s):  
Phylogenetic Analyses ◽  
Radial Symmetry ◽  
Early Evolution ◽  
Phylogenetic Position ◽  
Crown Group ◽  
Brittle Stars ◽  
Major Clade ◽  
Early Ordovician ◽  
Stem Group ◽  
Successful Group

AbstractThe somasteroids are Ordovician star-shaped animals widely regarded as ancestors of Asterozoa, the group of extant echinoderms that includes brittle stars and starfish. The phylogenetic position of somasteroids makes them critical for understanding the origin and early evolution of crown group Echinodermata. However, the early evolution of asterozoans, the origin of their distinctive body organization and their relationships with other Cambrian and Ordovician echinoderms, such as edrioasteroids, blastozoans, crinoids, and other asterozoans, remain problematic due to the difficulties of comparing the calcitic endoskeleton of these disparate groups. Here we describe the new somasteroidCantabrigiaster fezouataensisfrom the Early Ordovician (Tremadocian) Fezouata Lagerstätte in Morocco.Cantabrigiastershares with other somasteroids the presence of rod-like virgal ossicles that articulate with the ambulacrals, but differs from all other known asterozoans in the absence of adambulacral ossicles defining the arm margins. The unique arm construction evokes parallels with non-asterozoan echinoderms. Developmentally informed Bayesian and parsimony based phylogenetic analyses, which reflect the homology of the biserial ambulacral ossicles in Paleozoic echinoderms according to the Extraxial-Axial Theory, recoverCantabrigiasteras basal within stem group Asterozoa. Our results indicate thatCantabrigiasteris the earliest diverging stem group asterozoan, revealing the ancestral morphology of this major clade and clarifying the affinities of problematic Ordovician taxa. Somasteroids are resolved as a paraphyletic grade within stem and crown group Asterozoa (starfishes), whereas stenuroids are paraphyletic within stem group Ophiuroidea (brittle stars).Cantabrigiasteralso illuminates the relationship between Ordovician crown group Echinodermata and its Cambrian stem lineage, which includes sessile forms with incipient radial symmetry such as edrioasteroids and blastozoans. The contentious Pelmatozoa hypothesis (i.e. monophyly of blastozoans and crinoids) is not supported; instead, blastozoans represent the most likely sister-taxon of crown group Echinodermata.Author summaryStarfish and brittle stars, collectively known as asterozoans, constitute a diverse and ecologically successful group of echinoderms that first appear in the fossil record some 480Ma. However, the early evolution of asterozoans, the origin of their distinctive body organization, and their phylogenetic relationships with Cambrian echinoderms remain largely unresolved. We describeCantabrigiaster fezouataensisgen. et sp. nov., a primitive asterozoan from the Fezouata Lagerstätte, Morocco, with a unique endoskeletal arm organization that reveals the ancestral morphology of this major clade. Bayesian and parsimony based phylogenetic analyses indicate thatCantabrigiasteris the earliest diverging stem group asterozoan, and resolve the phylogenetic position of Ordovician asterozoans such as somasteroids. Our analyses clarify the origin of crown group echinoderms relative to their problematic Cambrian stem group representatives.

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