| Trimerus | |
|---|---|
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| Fossil ofTrimerus (Trimerus) delphinocephalus from the Rochester Shale of North America, housed at the Oxford University Natural History Museum. | |
 | |
| Reconstruction ofTrimerus (Trimerus) delphinocephalus from the Rochester Shale of North America. | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | †Trilobita |
| Order: | †Phacopida |
| Family: | †Homalonotidae |
| Genus: | †Trimerus Green, 1832 |
| Species: | †T. delphinocephalus |
| Binomial name | |
| †Trimerus delphinocephalus Green, 1832 | |
| Other species | |
See text | |
Trimerus is an extinct genus of trilobite in the familyHomalonotidae.Trimerus is one of North America's largest trilobites, reaching over 20 cm (7.9 in) in length. It had a thorax composed of 13 segments with weak trilobation, a large subtriangular head terminating in an expanded rostral plate, a two-prongedhypostome, and a triangularpygidium. It is known from all continents except forAntarctica. Its tinycompound eyes and the shovel-like anterior of the head suggests a burrowing lifestyle, and an exoskeleton marked with many small pores which, in life, probably housed hair-likesensory setae in life, allowed the trilobite to feel which portions of its body were covered with sediment.[1]
In his description of new Homalonotid species fromAustralia andNew Zealand, Andrew Sandford dividedTrimerus species into multiplesubgenera to better categorize distinct populations.[2] A number of species previously assigned to other genera were included, and a number of species previously assigned toTrimerus were excluded, variously reassigned to the trilobite generaDipleura (Dipleura dekayi has been frequently included withinTrimerus),Digonus,Burmeisteria, andWenndorfia. The following list is therefore provisional, and other sources may differ.[3][4] A handful of species also remain undescribed.
Trimerus (Trimerus)
This group is known only from theSilurian (Wenlock toLudlow).
Trimerus (Edgillia)
This group is known from the Late Silurian to the EarlyDevonian. Named after E. D. Gill, for his contributions to Australian paleontology, including naming a number of Homalonotid trilobites.
Trimerus (Ramiotis)
This group is known only from the Silurian. Named for Otis Rami, the son of the author.[2]
The following species have not been assigned to a subgenus.
