Plectodiscus discoideus (Rauff): A redescription of a chondrophorine from the early devonian hunsrück Slate, West Germany

PalZ ◽  
1983 ◽  
Vol 57 (1-2) ◽  
pp. 39-68 ◽  
Author(s):  
Ellis L. Yochelson ◽  
Wilhelm Stürmer ◽  
George O. Stanley
PalZ ◽  
1986 ◽  
Vol 60 (1-2) ◽  
pp. 57-64 ◽  
Author(s):  
Kristian Fauchald ◽  
Wilhelm Stürmer ◽  
Ellis L. Yochelson

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3526 ◽  
Author(s):  
Julia Stilkerich ◽  
Trisha A. Smrecak ◽  
Kenneth De Baets

We herein examine the only known non-planispirally coiled early Devonian ammonoid, the holotype specimen of Ivoites opitzi, to investigate if the host was encrusted in vivo and if these sclerobionts were responsible for the trochospiral coiling observed in this unique specimen. To test if the presence of runner-like sclerobionts infested the historically collected specimen of Ivoites opitzi during its life, we used microCT to produce a three-dimensional model of the surface of the specimen. Our results indicate that sclerobionts grew across the outer rim (venter) on both sides of the ammonoid conch at exactly the location where the deviation from the planispiral was recognized, and where subsequent ammonoid growth would likely preclude encrustation. This indicates in vivo encrustation of the I. opitzi specimen, and represents the earliest documentation of the phenomenon. Further, this suggests that non-planispiral coiling in I. opitzi was likely pathologically induced and does not represent natural morphological variation in the species. Despite the observed anomalies in coiling, the specimen reached adulthood and retains important identifying morphological features, suggesting the ammonoid was minimally impacted by encrustation in life. As such, appointing a new type specimen—as suggested by some authors—for the species is not necessary. In addition, we identify the sclerobionts responsible for modifying the coiling of this specimen as hederelloids, a peculiar group of sclerobionts likely related to phoronids. Hederelloids in the Devonian are commonly found encrusting on fossils collected in moderately deep environments within the photic zone and are rarely documented in dysphotic and aphotic samples. This indicates that when the ammonoid was encrusted it lived within the euphotic zone and supports the latest interpretations of the Hunsrück Slate depositional environment in the Bundenbach-Gemünden area.


2016 ◽  
Author(s):  
Julia Stilkerich ◽  
Trisha A Smrecak ◽  
Kenneth De Baets

We herein examine the only known non-planispirally coiled early Devonian ammonoid, the holotype specimen of Ivoites opitzi, to investigate if the host was encrusted in vivo and if these sclerobionts were responsible for the trochospiral coiling observed on this unique specimen. To test if the presence of runner-like sclerobionts infested the historically collected specimen of Ivoites opitzi during its life, we used microCT to produce a three-dimensional model of the surface of the specimen. Our results indicate that sclerobionts grew across the outer rim (venter) on both sides of the ammonoid conch at exactly the location where the deviation from the planispiral was recognized, and where subsequent ammonoid growth would likely preclude encrustation. This indicates in vivo encrustation of the I. opitzi specimen, and represents the earliest documentation of the phenomenon. Further, this suggests that non-planispiral coiling in I. opitzi was pathologically induced and does not represent natural morphological variation in the species. Despite the observed anomalies in coiling, the specimen reached adulthood and retains important identifying morphological features, suggesting the ammonoid was minimally impacted by encrustation in life. As such, appointing a new type specimen – as suggested by some authors – for the species is not necessary. In addition, we identify the sclerobionts responsible for modifying the coiling of this specimen as hederelloids, a peculiar group of sclerobionts likely related to phoronids. Hederelloids in the Devonian are commonly found encrusting on fossils collected in moderately deep environments within the photic zone and are rarely documented in dysphotic and aphotic samples. This indicates that when the ammonoid was encrusted it lived within the euphotic zone and supports the latest interpretations of the Hunsrück Slate depositional environment.


Fossil Record ◽  
2002 ◽  
Vol 5 (1) ◽  
pp. 93-104 ◽  
Author(s):  
J. A. Dunlop ◽  
S. J. Braddy ◽  
E. Tetlie

The holotype and only known specimen of the eurypterid (Chelicerata: Eurypterida) <i>Grossopterus overathi</i> (Gross, 1933) from the Early Devonian (Siegennian) of Overath, north-west Germany is redescribed. Based on comparisons with other eurypterid taxa we interpret <i>G. overathi</i> as having a well-preserved type B genital appendage, which exhibits two apomorphic character states: (1) a furca fused into a single, spatulate plate and (2) marginal serrations near the distal end of the appendage. <i>Grossopterus</i> is assigned to the family Hughmilleriidae, but its carapace resembles that of the larger <i>Slimonia acuminata</i> (Salter, 1856) (Slimoniidae). A provisional phylogenetic analysis resolves <i>Grossopterus</i> as the sister group of (<i>Slimonia</i> + Pterygotoidea). The large pterygotids, in particular, have been suggested as significant predators on early vertebrates and hypotheses about eurypterid-fish co-evolution are reviewed, in particular Romer's proposal that dermal armour in fish evolved in response to eurypterid predation. <br><br> Der Holotyp – das einzig bekannte Exemplar – des Eurypteriden (Chelicerata: Eurypterida) <i>Grossopterus overathi</i> (Gross, 1933) aus dem frühen Devon (Siegennian) von Overath im nordwestlichen Deutschland wird wieder beschrieben. Basierend auf Vergleichen mit anderen Eurypteriden-Taxa interpretieren wir <i>G. overathi</i> als Träger eines Typ B-Anhanges, wobei zwei apomorphe Merkmalszustände vorliegen: (1) die Furca ist zu einer einzigen, spatelförmigen Platte verschmolzen, und (2) der Seitenrand nahe des distalen Endes des Genitalanhanges ist gezähnt. <i>Grossopterus</i> wird zur Familie der Hughmilleriidae gestellt, aber der prosomale Dorsalschild ähnelt der größeren <i>Slimonia acuminata</i> (Salter, 1856) (Slimoniidae). Eine vorläufige phylogenetische Analyse zeigt <i>Grossopterus</i> als Schwesteruppe von (<i>Slimonia</i> + Pterygotoidea) auf. Besonders die großen Pterygotiden wurden als signifikante Prädatoren von frühen Vertebraten gehandelt, und Hypothesen zur Eurypteriden-Fisch Koevolution werden überprüft, speziell Romers Vorschlag, dass die dermale Panzerung von Fischen als Antwort auf die Prädation durch Eurypteriden evolvierte. <br><br> doi:<a href="http://dx.doi.org/10.1002/mmng.20020050107" target="_blank">10.1002/mmng.20020050107</a>


2016 ◽  
Vol 3 (2) ◽  
pp. 151-159 ◽  
Author(s):  
Joachim T. Haug ◽  
Markus Poschmann ◽  
Marie K. Hörnig ◽  
Herbert Lutz

2017 ◽  
Author(s):  
Julia Stilkerich ◽  
Trisha A Smrecak ◽  
Kenneth De Baets

We herein examine the only known non-planispirally coiled early Devonian ammonoid, the holotype specimen of Ivoites opitzi, to investigate if the host was encrusted in vivo and if these sclerobionts were responsible for the trochospiral coiling observed on this unique specimen. To test if the presence of runner-like sclerobionts infested the historically collected specimen of Ivoites opitzi during its life, we used microCT to produce a three-dimensional model of the surface of the specimen. Our results indicate that sclerobionts grew across the outer rim (venter) on both sides of the ammonoid conch at exactly the location where the deviation from the planispiral was recognized, and where subsequent ammonoid growth would likely preclude encrustation. This indicates in vivo encrustation of the I. opitzi specimen, and represents the earliest documentation of the phenomenon. Further, this suggests that non-planispiral coiling in I. opitzi was pathologically induced and does not represent natural morphological variation in the species. Despite the observed anomalies in coiling, the specimen reached adulthood and retains important identifying morphological features, suggesting the ammonoid was minimally impacted by encrustation in life. As such, appointing a new type specimen – as suggested by some authors – for the species is not necessary. In addition, we identify the sclerobionts responsible for modifying the coiling of this specimen as hederelloids, a peculiar group of sclerobionts likely related to phoronids. Hederelloids in the Devonian are commonly found encrusting on fossils collected in moderately deep environments within the photic zone and are rarely documented in dysphotic and aphotic samples. This indicates that when the ammonoid was encrusted it lived within the euphotic zone and supports the latest interpretations of the Hunsrück Slate depositional environment.


2017 ◽  
Author(s):  
Julia Stilkerich ◽  
Trisha A Smrecak ◽  
Kenneth De Baets

We herein examine the only known non-planispirally coiled early Devonian ammonoid, the holotype specimen of Ivoites opitzi, to investigate if the host was encrusted in vivo and if these sclerobionts were responsible for the trochospiral coiling observed on this unique specimen. To test if the presence of runner-like sclerobionts infested the historically collected specimen of Ivoites opitzi during its life, we used microCT to produce a three-dimensional model of the surface of the specimen. Our results indicate that sclerobionts grew across the outer rim (venter) on both sides of the ammonoid conch at exactly the location where the deviation from the planispiral was recognized, and where subsequent ammonoid growth would likely preclude encrustation. This indicates in vivo encrustation of the I. opitzi specimen, and represents the earliest documentation of the phenomenon. Further, this suggests that non-planispiral coiling in I. opitzi was pathologically induced and does not represent natural morphological variation in the species. Despite the observed anomalies in coiling, the specimen reached adulthood and retains important identifying morphological features, suggesting the ammonoid was minimally impacted by encrustation in life. As such, appointing a new type specimen – as suggested by some authors – for the species is not necessary. In addition, we identify the sclerobionts responsible for modifying the coiling of this specimen as hederelloids, a peculiar group of sclerobionts likely related to phoronids. Hederelloids in the Devonian are commonly found encrusting on fossils collected in moderately deep environments within the photic zone and are rarely documented in dysphotic and aphotic samples. This indicates that when the ammonoid was encrusted it lived within the euphotic zone and supports the latest interpretations of the Hunsrück Slate depositional environment.


1998 ◽  
Vol 138 (2) ◽  
pp. 376-376
Author(s):  
Schäfer ◽  
Krämer ◽  
Vieluf ◽  
Behrendt ◽  
Ring

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