The taxonomic challenge posed by the Antarctic echinoids Abatus bidens and Abatus cavernosus (Schizasteridae, Echinoidea)

First Record of Sexual Dimorphism in Toxasterid Echinoid Heteraster from the Early Cretaceous Deposits of the Kopet‐Dagh Basin, NE Iran

“…This is because females produce large eggs (Smith, 1984). These differences in size of the genital pores have been reported in the echinocyamid clypeastroids (Kier, 1967(Kier, , 1968(Kier, , 1969, cassiduloids (Philip, 1963;Saucè de and Né raudeau, 2006;Arab and Vaziri, 2010), schizasterid spatangoids (David et al, 2015;Gil et al, 2019), hemiasterid spatangoids (Cottreau, 1922;Né raudeau, 1993), echinocardiid spatangoids (David et al, 1988), micrasterid spatangoids, Cyclaster (Henderson, 1975;Jagt and Michels, 1990) and a Cretaceous cidarid, Stereocidaris (Müller, 1970).…”

“…In cassiduloid echinoids (Philip, 1963;Saucè de and Né raudeau, 2006;Arab and Vaziri, 2010), clypeastroids (Kier, 1967(Kier, , 1968(Kier, , 1969 and cidarids (Müller, 1970), this feature is very common. In spatangoids, sexual dimorphism has been reported extensively in the families Hemiasteridae (Cottreau, 1922;Né raudeau, 1993), Schizasteridae (David et al, 2015;Gil et al, 2019), Micrasteridae (Henderson, 1975;Jagt and Michels, 1990) and Echinocardiidae (David et al, 1988). However, this feature has not been reported in the toxasterid spatangoid family, until now.…”

First Record of Sexual Dimorphism in Toxasterid Echinoid Heteraster from the Early Cretaceous Deposits of the Kopet‐Dagh Basin, NE Iran

“…This is because females produce large eggs (Smith, 1984). These differences in size of the genital pores have been reported in the echinocyamid clypeastroids (Kier, 1967(Kier, , 1968(Kier, , 1969, cassiduloids (Philip, 1963;Saucè de and Né raudeau, 2006;Arab and Vaziri, 2010), schizasterid spatangoids (David et al, 2015;Gil et al, 2019), hemiasterid spatangoids (Cottreau, 1922;Né raudeau, 1993), echinocardiid spatangoids (David et al, 1988), micrasterid spatangoids, Cyclaster (Henderson, 1975;Jagt and Michels, 1990) and a Cretaceous cidarid, Stereocidaris (Müller, 1970).…”

“…In cassiduloid echinoids (Philip, 1963;Saucè de and Né raudeau, 2006;Arab and Vaziri, 2010), clypeastroids (Kier, 1967(Kier, , 1968(Kier, , 1969 and cidarids (Müller, 1970), this feature is very common. In spatangoids, sexual dimorphism has been reported extensively in the families Hemiasteridae (Cottreau, 1922;Né raudeau, 1993), Schizasteridae (David et al, 2015;Gil et al, 2019), Micrasteridae (Henderson, 1975;Jagt and Michels, 1990) and Echinocardiidae (David et al, 1988). However, this feature has not been reported in the toxasterid spatangoid family, until now.…”

Deciphering the Hearts: Geometric Morphometrics Reveals Shape Variation in Abatus Sea Urchins across Subantarctic and Antarctic Seas

“…The Falklands/Malvinas group is represented along PC1 by specimens with more elongated and narrower tests, which contrasts with the more rounded shape of the group. This clear difference in shape between A. cavernosus from the Falklands/Malvinas and the one from Patagonia can be explained by several factors [ 6 , 12 ]. The difference in shape could be attributed to phenotypic plasticity and peculiar local environmental conditions prevailing in the sampling areas.…”

Schizasterid Heart Urchins Host Microorganisms in a Digestive Symbiosis of Mesozoic Origin

“…Though the latter scenario does not seem particularly parsimonious given the strong similarity in overall shape and location of the IC, it is worth noting that barriers to the evolution of digestive appendices may be low ( Smith et al, 2017 ). Distinguishing among the different evolutionary hypotheses will require both an improved understanding of schizasterid phylogeny ( David et al, 2005 , 2016 ; Saucède et al, 2013 ), as well as further study of the distribution and characteristics of the IC within the clade.…”

First Record of Sexual Dimorphism in Toxasterid Echinoid Heteraster from the Early Cretaceous Deposits of the Kopet‐Dagh Basin, NE Iran

“…This is because females produce large eggs (Smith, 1984). These differences in size of the genital pores have been reported in the echinocyamid clypeastroids (Kier, 1967(Kier, , 1968(Kier, , 1969, cassiduloids (Philip, 1963;Saucè de and Né raudeau, 2006;Arab and Vaziri, 2010), schizasterid spatangoids (David et al, 2015;Gil et al, 2019), hemiasterid spatangoids (Cottreau, 1922;Né raudeau, 1993), echinocardiid spatangoids (David et al, 1988), micrasterid spatangoids, Cyclaster (Henderson, 1975;Jagt and Michels, 1990) and a Cretaceous cidarid, Stereocidaris (Müller, 1970).…”

“…In cassiduloid echinoids (Philip, 1963;Saucè de and Né raudeau, 2006;Arab and Vaziri, 2010), clypeastroids (Kier, 1967(Kier, , 1968(Kier, , 1969 and cidarids (Müller, 1970), this feature is very common. In spatangoids, sexual dimorphism has been reported extensively in the families Hemiasteridae (Cottreau, 1922;Né raudeau, 1993), Schizasteridae (David et al, 2015;Gil et al, 2019), Micrasteridae (Henderson, 1975;Jagt and Michels, 1990) and Echinocardiidae (David et al, 1988). However, this feature has not been reported in the toxasterid spatangoid family, until now.…”

Deciphering the Hearts: Geometric Morphometrics Reveals Shape Variation in Abatus Sea Urchins across Subantarctic and Antarctic Seas

“…The Falklands/Malvinas group is represented along PC1 by specimens with more elongated and narrower tests, which contrasts with the more rounded shape of the group. This clear difference in shape between A. cavernosus from the Falklands/Malvinas and the one from Patagonia can be explained by several factors [ 6 , 12 ]. The difference in shape could be attributed to phenotypic plasticity and peculiar local environmental conditions prevailing in the sampling areas.…”

Schizasterid Heart Urchins Host Microorganisms in a Digestive Symbiosis of Mesozoic Origin

“…Though the latter scenario does not seem particularly parsimonious given the strong similarity in overall shape and location of the IC, it is worth noting that barriers to the evolution of digestive appendices may be low ( Smith et al, 2017 ). Distinguishing among the different evolutionary hypotheses will require both an improved understanding of schizasterid phylogeny ( David et al, 2005 , 2016 ; Saucède et al, 2013 ), as well as further study of the distribution and characteristics of the IC within the clade.…”

First Record of Sexual Dimorphism in Toxasterid Echinoid Heteraster from the Early Cretaceous Deposits of the Kopet‐Dagh Basin, NE Iran

“…This is because females produce large eggs (Smith, 1984). These differences in size of the genital pores have been reported in the echinocyamid clypeastroids (Kier, 1967(Kier, , 1968(Kier, , 1969, cassiduloids (Philip, 1963;Saucè de and Né raudeau, 2006;Arab and Vaziri, 2010), schizasterid spatangoids (David et al, 2015;Gil et al, 2019), hemiasterid spatangoids (Cottreau, 1922;Né raudeau, 1993), echinocardiid spatangoids (David et al, 1988), micrasterid spatangoids, Cyclaster (Henderson, 1975;Jagt and Michels, 1990) and a Cretaceous cidarid, Stereocidaris (Müller, 1970).…”

“…In cassiduloid echinoids (Philip, 1963;Saucè de and Né raudeau, 2006;Arab and Vaziri, 2010), clypeastroids (Kier, 1967(Kier, , 1968(Kier, , 1969 and cidarids (Müller, 1970), this feature is very common. In spatangoids, sexual dimorphism has been reported extensively in the families Hemiasteridae (Cottreau, 1922;Né raudeau, 1993), Schizasteridae (David et al, 2015;Gil et al, 2019), Micrasteridae (Henderson, 1975;Jagt and Michels, 1990) and Echinocardiidae (David et al, 1988). However, this feature has not been reported in the toxasterid spatangoid family, until now.…”

Deciphering the Hearts: Geometric Morphometrics Reveals Shape Variation in Abatus Sea Urchins across Subantarctic and Antarctic Seas

“…The Falklands/Malvinas group is represented along PC1 by specimens with more elongated and narrower tests, which contrasts with the more rounded shape of the group. This clear difference in shape between A. cavernosus from the Falklands/Malvinas and the one from Patagonia can be explained by several factors [ 6 , 12 ]. The difference in shape could be attributed to phenotypic plasticity and peculiar local environmental conditions prevailing in the sampling areas.…”

Schizasterid Heart Urchins Host Microorganisms in a Digestive Symbiosis of Mesozoic Origin

“…Though the latter scenario does not seem particularly parsimonious given the strong similarity in overall shape and location of the IC, it is worth noting that barriers to the evolution of digestive appendices may be low ( Smith et al, 2017 ). Distinguishing among the different evolutionary hypotheses will require both an improved understanding of schizasterid phylogeny ( David et al, 2005 , 2016 ; Saucède et al, 2013 ), as well as further study of the distribution and characteristics of the IC within the clade.…”