{{Short description|Genus of Devonian trilobites}} {{Automatic taxobox | fossil_range = {{fossilrange|400|390|Upper Emsian and Lower Eifelian}} | image = Walliserops trifurcatus, Early Devonian, Timrhanrhart Formation, Jbel Gara el Zguilma, Draa Valley, Morocco - Houston Museum of Natural Science - DSC01584.JPG | image_caption = ''Walliserops trifurcatus'' | taxon = Walliserops | type_species = '''''Walliserops trifurcatus''''' | type_species_authority = Morzadec, 2001 | subdivision_ranks = Species | subdivision = {{Specieslist |W. trifurcatus|Morzadec, 2001 |W. hammii|Chatterton et al., 2006 |W. lindoei|Chatterton & Gibb, 2010 |W. tridens|Chatterton et al., 2006 }} }} alt=A finely prepared Walliserops trifurcatus trilobite fossil|thumb|''Walliserops trifurcatus''
'''''Walliserops''''' (named after Prof. O. Walliser of the University of Göttingen) is a genus of spinose phacopid trilobite, of the family Acastidae, found in Lower to Middle Devonian age rocks from the Anti-Atlas Mountains of Morocco. All species of ''Walliserops'' possess a three-pronged "trident" that protrudes from the glabella. ''Walliserops'' is most closely related to the genus ''Comura''.<ref name="Brett">{{cite conference |author1=K. Brett |author2=N. Chatterton |name-list-style=amp |year=2001 |title=''Parabolops'', a new asteropygine trilobite from southern Morocco with an unusual trident-like anterior cephalic frontal process |conference=3rd International Conference on Trilobites and their Relatives |location=University of Oxford}}</ref><ref name="Chatterton">{{cite book |author=B. Chatterton |author2=R. Fortey |author3=K. Brett |author4= S. Gibb |author5=R. McKellar |name-list-style=amp |year=2006 |title=Trilobites from the Lower to Middle Devonian Timrhanrhart Formation, Jbel Gara el Zquilma, southern Morocco |series=Palaeontographica Canadiana 25 |isbn=1-897095-15-5}}</ref>
== Taxonomy == ''Walliserops'' was originally erected for a single species, '''''W. trifurcatus'''''.<ref name="Morzadec">{{cite journal |author=Pierre Morzadec |year=2001 |title=Les Trilobites Asteropyginae du Dévonien de l'Anti Atlas (Maroc) |journal=Palaeontographica |series=Abteilung A |volume=244 |issue=1–3 |pages=53–85 |doi=10.1127/pala/262/2001/53 |bibcode=2001PalAA.262...53M |s2cid=246354103 |language=French |url=http://www.schweizerbart.de/papers/pala/detail/262/74241 |url-access=subscription |archive-date=2012-03-12 |access-date=2010-10-01 |archive-url=https://web.archive.org/web/20120312145707/http://www.schweizerbart.de/papers/pala/detail/262/74241 |url-status=dead }}</ref> Later, two other species were assigned: '''''W. hammii''''' and '''''W. tridens'''''.<ref name="Chatterton"/> All three currently described species come from the same strata near Foum Zguid in southern Morocco. Three as yet undescribed species are recorded from other locations.<ref name="Chatterton"/>
Early reports of "trident" trilobites<ref name="Brett"/> and placement within the proposed new genus "''Parabolops''" ("parabola face")—long tridents being placed within "''P.''' '''neptunis''", short tridents placed within "''P.''' '''hammi''"—were pre-empted by the publication of the detailed analysis of ''Walliserops''.<ref name="Morzadec"/>
== Description ==
=== Asymmetry === Departures from bilateral symmetry are an unusual feature within ''Walliserops'' species, most clearly shown by the curved occipital spine of ''W.''' '''hammii'' taking a noticeable curl to one side. The regular development of these features in multiple specimens suggest a genetically controlled feature of the genus and not mutations or pathology. Most of the exceptions to bilateral symmetry noted (and also the absence of spines on the first two thoracic segments) can be explained by adaptations allowing the trident to be held off the sea floor while walking. Between the species there are variations in the extent of departure from bilateral symmetry: ''W.''' '''trifurcatus'', with a long trident that is curved away from the seabed, has less obvious departures from bilateral symmetry than ''W.''' '''hammii'', with a short trident close to the seabed.<ref name="Chatterton"/>
=== Trident function === The function of the trident itself is poorly understood. With the amount of energy and nutrients expended in growing such a large adornment (probably multiple times as the trilobite shed its skin) its function was clearly important.<ref name="Chatterton"/> Although a number of suggestions have been made (e.g. sensory apparatus, disguise or protection), the most satisfactory current explanation is that the trident served as "horns" similar to those of present-day beetles such as the rhinoceros beetles.<ref name="Knell">{{cite journal |author1=Robert J. Knell |author2=Richard A. Fortey |name-list-style=amp |year=2005 |pmid=17148165 |title=Trilobite spines and beetle horns: sexual selection in the Palaeozoic? |journal=Biology Letters |volume=1 |issue=2 |pages=196–199 |doi=10.1098/rsbl.2005.0304 |pmc=1626209}}</ref>
Sexual dimorphism was an intriguing prospect (longer trident forms as jousting males) when only two species (or possible dimorphs) were known.<ref name="Brett"/> With the description of three species from the same location, polymorphism was another prospect but seemed unlikely.<ref name="Chatterton"/> Although the presence of horns strongly suggests sexual dimorphism,<ref name="Knell"/> lack of data on numerous fronts currently prevents firm conclusions from being drawn.<ref name="Chatterton"/> {{Quote|Sexual dimorphism in any trilobite exoskeleton has not yet been satisfactorily demonstrated and any decision to regard evidence as sexual dimorphism or as subspecific/specific difference(s) will be arbitrary.|Whittington, 1997<ref>{{cite book |author=H. B. Whittington |year=1997 |chapter=Mode of Life, Habits and Occurrence |editor=R. L. Kaesler |title=Treatise on Invertebrate Paleontology, Part O, Arthropoda 1, Trilobita, revised. Volume 1: Introduction, Order Agnostida, Order Redlichiida |publisher=The Geological Society of America, Inc. & The University of Kansas |location=Boulder, Colorado & Lawrence, Kansas |isbn=0-8137-3115-1 |pages=[https://archive.org/details/treatiseoninvert0002unse/page/161 161–162] |chapter-url=https://archive.org/details/treatiseoninvert0002unse/page/161 }}</ref>}}
{{Multiple image | direction = horizontal | align = center | width1 = 121 | image1 = Walliserops trifurcatus.JPG | caption1 = ''Walliserops trifurcatus'' | width2 = 213 | image2 = | caption2 = ''Walliserops hammii'' | width3 = 163 | image3 = Walliserops tridens.JPG | caption3 = ''Walliserops tridens'' | width4 = 217 | image4 = | caption4 = ''Walliserops n. sp.'' undescribed species | total_width = 600 }} {{Clear}}
==References== {{Reflist}}
==External links== {{Commons category}} *[https://www.newscientist.com/channel/life/mg18625015.100/ Earliest combatants in sexual contests revealed], ''New Scientist'' *[http://www.fossilmall.com/EDCOPE_Enterprises/trilobites/MTrilo5/MTrilo5.htm ''W. trifurcatus''], Fossil Mall
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Category:Fossils of Morocco Category:Acastidae Category:Devonian trilobites of Africa Category:Early Devonian first appearances Category:Eifelian extinctions Category:Fossil taxa described in 2001 Category:Phacopida genera