:en:Pseudoangustidontus
{{Short description|Hurdiid radiodont from the Early Ordovician}}
{{Automatic taxobox
| fossil_range = Lower Ordovician, {{Fossil Range|485|475|refs=}}
| image = Fossil appendage of the engimatic arthropod Pseudoangustidontus.webp
| image_caption = Fossil endites of P. duplospineus
| image2 = Pseudoangustidontus izdigua MGL 103606.jpg
| image2_caption = Fossil appendage of P. izdigua with 3D rendering (F-G)
| taxon = Pseudoangustidontus
| authority = Van Roy & Tetlie, 2006
| subdivision_ranks = Species
| subdivision =
- {{extinct}}Pseudoangustidontus duplospineus Van Roy & Tetlie, 2006
- {{extinct}}Pseudoangustidontus izdigua Potin, Gueriau & Daley, 2023
}}
Pseudoangustidontus (meaning "false Angustidontus") is a genus of hurdiid (peytoiid) radiodont from the Lower Ordovician of Morocco.{{cite journal|last1=Van Roy|first1=Peter|last2=Tetlie|first2=O. Erik|year=2006|title=A spinose appendage fragment of a problematic arthropod from the Early Ordovician of Morocco|journal=Acta Palaeontologica Polonica|volume=51|issue=2|pages=239–246|url=https://www.app.pan.pl/article/item/app51-239.html|hdl=1854/LU-347096|hdl-access=free}}{{cite journal |last1=Martin |first1=Emmanuel L.O. |last2=Pittet |first2=Bernard |last3=Gutiérrez-Marco |first3=Juan-Carlos |last4=Vannier |first4=Jean |last5=El Hariri |first5=Khadija |last6=Lerosey-Aubril |first6=Rudy |last7=Masrour |first7=Moussa |last8=Nowak |first8=Hendrik |last9=Servais |first9=Thomas |last10=Vandenbroucke |first10=Thijs R.A. |last11=Van Roy |first11=Peter |last12=Vaucher |first12=Romain |last13=Lefebvre |first13=Bertrand |year=2016 |title=The Lower Ordovician Fezouata Konservat-Lagerstätte from Morocco: Age, environment and evolutionary perspectives |journal=Gondwana Research |volume=34 |pages=274–283 |bibcode=2016GondR..34..274M |doi=10.1016/j.gr.2015.03.009 |issn=1342-937X |doi-access=free}} This genus is known from two described species, P. duplospineus and P. izidigua, with some specimens that are hard to determine which species to belong to. This animal is only known from the Fezouata Formation, a fossil site in Morocco that is of Lagerstätte status, meaning that the fossils from this site are exceptionally preserved.{{Cite journal |last1=Van Roy |first1=P. |last2=Orr |first2=P. J. |last3=Botting |first3=J. P. |last4=Muir |first4=L. A. |last5=Vinther |first5=J. |last6=Lefebvre |first6=B. |last7=Hariri |first7=K. E. |last8=Briggs |first8=D. E. G. |author-link8=Derek Briggs |year=2010 |title=Ordovician faunas of Burgess Shale type |journal=Nature |volume=465 |issue=7295 |pages=215–8 |bibcode=2010Natur.465..215V |doi=10.1038/nature09038 |pmid=20463737 |s2cid=4313285}} Because of its partial remains, its classification was debated, but with more complete fossils it is identified as radiodont frontal appendage.
Description
File:20230828 Radiodonta frontal appendage Pseudoangustidontus duplospineus.png|Reconstruction of the frontal appendage of P. duplospineus
File:20230828 Radiodonta frontal appendage Pseudoangustidontus izdigua.png|Reconstruction of the frontal appendage of P. izdigua
File:20191229 Radiodonta frontal appendage Aegirocassis benmoulai Aegirocassis benmoulae.png|Reconstruction of the frontal appendage of Aegirocassis for comparison
Pseudoangustidontus is only described from frontal appendage remains, with an exception of MGL 108047_1, holotype of P. izidigua which preserved part of carapace. P. duplospineus had paired setae alternating in length short/long while frontal appendage of P. izdigua bears endites with setae that are all the same length.
Classification
{{Multiple images
| image1 = Pseudoangustidontus.jpg
| image2 = Angustidontus.jpg
| align = left
| caption2 =
| caption1 =
| direction = horizontal
| image3 = 20191205 Aegirocassis benmoulai Aegirocassis benmoulae.png
| image4 = Angustidontus seriatus.png
| caption4 =
| perrow = 2 / 2
| header =
| footer = Originally morphology of a fossil of P. duplospineus (top left) was compared to the appendages of Angustidontus (top right).
However, Pseudoangustidontus was later found to be a hurdiid radiodont like Aegirocassis (bottom left), while Angustidontus (bottom right) is a crustacean.
}}
When described in 2006, the only known fossils of this genus were isolated appendages that bore copious amounts of spines. Because of this, the taxonomy of this arthropod was debated, with possible suggestions of this creatures affinity being with the eurypterids, radiodonts, or crustaceans. In a review article in 2023, it was questionably placed in the Hurdiidae.{{Cite journal |last1=Potin |first1=Gaëtan J.-M. |last2=Daley |first2=Allison C. |date=2023 |title=The significance of Anomalocaris and other Radiodonta for understanding paleoecology and evolution during the Cambrian explosion |journal=Frontiers in Earth Science |volume=11 |doi=10.3389/feart.2023.1160285 |issn=2296-6463 |doi-access=free }} And in another paper that was released in the same year, describing newly found fossils, it was found to be closely related to Aegirocassis, a coexisting radiodont, and classified to the subfamily Aegirocassisinae.{{cite journal |last1=Potin |first1=G. J.-M. |last2=Gueriau |first2=P. |last3=Daley |first3=A. C. |year=2023 |title=Radiodont frontal appendages from the Fezouata Biota (Morocco) reveal high diversity and ecological adaptations to suspension-feeding during the Early Ordovician |journal=Frontiers in Ecology and Evolution |volume=11 |at=1214109 |doi=10.3389/fevo.2023.1214109 |doi-access=free}}
Paleoecology
Pseudoangustidontus is speculated to be a filter feeder similar to Aegirocassis, that used numerous setae on its frontal appendages as mesh to catch microorganisms. The setae and mesh size of the frontal appendages of Pseudoangustidontus is around 0.5 mm, slightly smaller than that of Aegirocassis (0.56 mm), both genera probably fed on mesoplankton. However, a specimen of P. izdigua had an unidentified shell or carapace with a diameter about 3 mm trapped in its setae, suggesting it could have fed on even larger prey.
References
{{Reflist}}
{{taxonbar|from=Q21368832|from2=Q3924863}}
Category:Fossil taxa described in 2006