''Walliserops'' (named after Prof. O. Walliser of the

University of Göttingen The University of Göttingen, officially the Georg August University of Göttingen, (german: Georg-August-Universität Göttingen, known informally as Georgia Augusta) is a public research university in the city of Göttingen, Germany. Founded ...

) is a genus of spinose phacopid

trilobite Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the ...

, of the

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Acastidae, found in Lower to Middle Devonian age rocks from the

Anti-Atlas Mountains The Anti-Atlas ( ar, الأطلس الصغير, shi, Aṭlas Mẓẓiyn), also known as Lesser Atlas or Little Atlas is a mountain range in Morocco, a part of the Atlas Mountains in the northwest of Africa. The Anti-Atlas extends from the Atlant ...

Morocco Morocco (),, ) officially the Kingdom of Morocco, is the westernmost country in the Maghreb region of North Africa. It overlooks the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria t ...

. All species of ''Walliserops'' possess a three-pronged "trident" that protrudes from the

glabella The glabella, in humans, is the area of skin between the eyebrows and above the nose. The term also refers to the underlying bone that is slightly depressed, and joins the two brow ridges. It is a cephalometric landmark that is just superior to ...

. ''Walliserops'' is most closely related to the genus '' Comura''. ''Walliserops'' was originally erected for a single species, ''W. trifurcatus''. Later, two other species were assigned: ''W. hammii'' & ''W. tridens''. 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. Early reports of "trident" trilobites 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''. 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. 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. 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 Dynastinae or rhinoceros beetles are a subfamily of the scarab beetle family (Scarabaeidae). Other common names – some for particular groups of rhinoceros beetles – include Hercules beetles, unicorn beetles or horn beetles. Over ...

Sexual dimorphism Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most an ...

was an intriguing prospect (longer trident forms as

jousting Jousting is a martial game or hastilude between two horse riders wielding lances with blunted tips, often as part of a tournament. The primary aim was to replicate a clash of heavy cavalry, with each participant trying to strike the opponen ...

males) when only two species (or possible dimorphs) were known. With the description of three species from the same location, polymorphism was another prospect but seemed unlikely. Although the presence of horns strongly suggests sexual dimorphism, lack of data on numerous fronts currently prevents firm conclusions from being drawn.

References

External links

Earliest combatants in sexual contests revealed
''

New Scientist ''New Scientist'' is a magazine covering all aspects of science and technology. Based in London, it publishes weekly English-language editions in the United Kingdom, the United States and Australia. An editorially separate organisation publish ...

''
''W. trifurcatus''
Fossil Mall {{Taxonbar, from=Q7963152 Fossils of Morocco Acastidae Devonian trilobites of Africa Early Devonian first appearances Eifelian extinctions Fossil taxa described in 2001