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

University of Göttingen The University of Göttingen, officially the Georg August University of Göttingen (, commonly referred to as Georgia Augusta), is a Public university, public research university in the city of Göttingen, Lower Saxony, Germany. Founded in 1734 ...

) is a genus of spinose phacopid

trilobite Trilobites (; meaning "three-lobed entities") are extinction, extinct marine arthropods that form the class (biology), class Trilobita. One of the earliest groups of arthropods to appear in the fossil record, trilobites were among the most succ ...

, of the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Acastidae, found in Lower to Middle

Devonian The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...

age rocks from the Anti-Atlas Mountains of

Morocco Morocco, officially the Kingdom of Morocco, is a country in the Maghreb region of North Africa. It has coastlines on the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria to Algeria–Morocc ...

. 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 ...

. ''Walliserops'' is most closely related to the genus '' Comura''.

Taxonomy

''Walliserops'' was originally erected for a single species, ''W. trifurcatus''. Later, two other species were assigned: ''W. hammii'' and ''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''.

Description

Asymmetry

Departures from

bilateral symmetry Symmetry in biology refers to the symmetry observed in organisms, including plants, animals, fungi, and bacteria. External symmetry can be easily seen by just looking at an organism. For example, the face of a human being has a plane of symme ...

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.

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. 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.

Sexual dimorphism Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...

was an intriguing prospect (longer trident forms as

jousting Jousting is a medieval and renaissance martial game or hastilude between two combatants either on horse or on foot. The joust became an iconic characteristic of the knight in Romantic medievalism. The term is derived from Old French , ultim ...

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 popular science 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 organ ...

''
''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 Phacopida genera