Walliserops
Encyclopedia
Walliserops is a genus of spinose phacopid
(acastid
) trilobite
found in Lower to Middle Devonian
age rocks from Morocco
. All species of Walliserops share, and are famous for, the spectacular three-pronged "trident" that rises from the glabella. 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 un-described 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 present day beetles.
Sexual dimorphism
was an intriguing prospect (longer trident forms as jousting
males) when only two species (or possible dimorphs) were known. With the description of three species from the same location, polymorphism
(e.g. caste system in ants and bees) 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.
Phacopida
Phacopida is an order of trilobite that lived from the Ordovician to the Devonian. It is made up of a morphologically diverse group of related suborders....
(acastid
Acastidae
Acastidae is a family of trilobites in the order Phacopidae, suborder Phacopina, superfamily Acastoidea, containing the following genera:*Acastava*Acaste*Acastella*Acastellina*Acastocephala*Acastoides*Acastopyge...
) trilobite
Trilobite
Trilobites are a well-known fossil group of extinct marine arthropods that form the class Trilobita. The first appearance of trilobites in the fossil record defines the base of the Atdabanian stage of the Early Cambrian period , and they flourished throughout the lower Paleozoic era before...
found in Lower to Middle Devonian
Devonian
The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...
age rocks from Morocco
Morocco
Morocco , officially the Kingdom of Morocco , is a country located in North Africa. It has a population of more than 32 million and an area of 710,850 km², and also primarily administers the disputed region of the Western Sahara...
. All species of Walliserops share, and are famous for, the spectacular three-pronged "trident" that rises from the glabella. 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 un-described 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 present day beetles.
Sexual dimorphism
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
was an intriguing prospect (longer trident forms as jousting
Jousting
Jousting is a martial game or hastilude between two knights mounted on horses and using lances, often as part of a tournament.Jousting emerged in the High Middle Ages based on the military use of the lance by heavy cavalry. The first camels tournament was staged in 1066, but jousting itself did not...
males) when only two species (or possible dimorphs) were known. With the description of three species from the same location, polymorphism
Polymorphism (biology)
Polymorphism in biology occurs when two or more clearly different phenotypes exist in the same population of a species — in other words, the occurrence of more than one form or morph...
(e.g. caste system in ants and bees) 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.
External links
- Virtual tour of W. hammii, Natural History MuseumNatural History MuseumThe Natural History Museum is one of three large museums on Exhibition Road, South Kensington, London, England . Its main frontage is on Cromwell Road...
- Example of W. trifurcatus, University of AlbertaUniversity of AlbertaThe University of Alberta is a public research university located in Edmonton, Alberta, Canada. Founded in 1908 by Alexander Cameron Rutherford, the first premier of Alberta and Henry Marshall Tory, its first president, it is widely recognized as one of the best universities in Canada...
- Earliest combatants in sexual contests revealed, New ScientistNew ScientistNew Scientist is a weekly non-peer-reviewed English-language international science magazine, which since 1996 has also run a website, covering recent developments in science and technology for a general audience. Founded in 1956, it is published by Reed Business Information Ltd, a subsidiary of...
- W. trifurcatus, Fossil Mall