Carolinites

{{Short description|Extinct genus of trilobites}} {{Automatic taxobox | image = Carolinites diagram.png | image_caption = Diagram (legs and antennae excluded) | fossil_range = {{fossil_range|488|456|Lower and Middle Ordovician}} | taxon = Carolinites | authority = Kobayashi, 1940 | type_species = '''''Carolinites bulbosa''''' | type_species_authority = Kobayashi, 1940 | subdivision_ranks = Species | subdivision = See text | synonyms = *''Dimastocephalus'' Stubblefield, 1950 *''Keidelia'' Harrington & Leanza, 1957 }}

'''''Carolinites''''' is a genus of telephinid trilobite from the Lower and Middle Ordovician. ''Carolinites'' had a pantropical distribution, and there is evidence that it lived in upper parts of the water column.<ref name=":2">{{Cite journal |last=McCormick |first=Tim |last2=Fortey |first2=Richard A. |date=1998 |title=Independent testing of a paleobiological hypothesis: the optical design of two Ordovician pelagic trilobites reveals their relative paleobathymetry |url=https://www.cambridge.org/core/journals/paleobiology/article/abs/independent-testing-of-a-paleobiological-hypothesis-the-optical-design-of-two-ordovician-pelagic-trilobites-reveals-their-relative-paleobathymetry/9FB445C663A6DF413A4257E730EF1FD6 |journal=Paleobiology |language=en |volume=24 |issue=2 |pages=235–253 |doi=10.1666/0094-8373(1998)024[0235:ITOAPH]2.3.CO;2 |issn=0094-8373|url-access=subscription }}</ref> Thanks to its free-swimming lifestyle, ''Carolinites'' was one of the most widely-distributed trilobites, similar in habits to modern hyperiid amphipods. Due to its large eyes, ''Carolinites'' was not very streamlined, so it was probably a relatively slow head-first swimmer which relied on enrollment (curling up) for defense.<ref name=":3">{{Cite journal |last=Fortey |first=R. A. |date=1985 |title=Pelagic trilobites as an example of deducing the life habits of extinct arthropods |url=https://www.cambridge.org/core/journals/earth-and-environmental-science-transactions-of-royal-society-of-edinburgh/article/abs/pelagic-trilobites-as-an-example-of-deducing-the-life-habits-of-extinct-arthropods/64C993D1AC8891D1FC5F4D28A7170C4E |journal=Earth and Environmental Science Transactions of The Royal Society of Edinburgh |language=en |volume=76 |issue=2-3 |pages=219–230 |doi=10.1017/S0263593300010452 |issn=1755-6929|url-access=subscription }}</ref><ref name=":0">{{Cite journal |last=McCormick |first=Tim |last2=Fortey |first2=Richard A. |date=1999 |title=The Most Widely Distributed Trilobite Species: Ordovician Carolinites genacinaca |url= |journal=Journal of Paleontology |volume=73 |issue=2 |pages=202–218 |issn=0022-3360 |jstor=1306780}}</ref>

== Description == The librigena of ''Carolinites'' (its "free cheeks", or the outer edges of the head) are mostly encased by its huge eyes, which cover a wide field of view in most directions. Despite the size of these compound eyes, their numerous individual lenses are relatively narrow and closely-spaced, similar to modern crustaceans which are active in sunlit waters during the day.<ref name=":2" /><ref>{{Cite journal |last=Fortey |first=Richard |date=2004 |title=The Lifestyles of the Trilobites |url=https://www.americanscientist.org/article/the-lifestyles-of-the-trilobites |journal=American Scientist |volume=92 |issue=5 |pages=446 |doi= |issn=0003-0996}}</ref> ''Carolinites''<nowiki/>'s preference for the epipelagic zone (sunlit waters) is also supported by its preservation in both shallow and deep marine sediments. A deep sea trilobite would only sink and fossilize in deep sediments, a bottom-dwelling shallow-water trilobite would only fossilize in shallow sediments, but a free-swimming trilobite which lives in the epipelagic zone throughout the tropics could die, sink, and fossilize in both areas.<ref name=":3" />

The eyes of ''Carolinites'' are widely-spaced, but some other pelagic trilobites (such as the deeper-water cyclopygids) have eyes which extend so far forwards that they merge into a visor-like structure.<ref name=":3" /> Apart from the eyes, the edge of the cephalon (head) provides the base for a pair of large genal spines, which extend downward, backward, and laterally (outward), gradually curving further backward. The glabella (central dome-like structure on the head) is boxy and slightly bulbous, extending to the front rim of the head. The occipital ring (a segment on the head immediately behind the glabella) is well-defined. Further transglabellar furrows (grooves embedded into the glabella) are lacking.<ref name=":1" />

The rest of the body is relatively narrow and muscular. The thorax (body region) has 10 segments. The axis (central portion) of the pygidium (tail region) is highly vaulted and its rear end is steeply sloped. The pygidium has four segments, each bearing a large node at its center. In some ''Carolinites'' fossils, the node of the last segment develops into a long curved spine which emerges straight up, almost perpendicular to the midline, before curving back to end parallel to the midline.<ref name=":1">{{cite book|editor= R.C. Moore|year= 1959|title=Treatise on Invertebrate Paleontology Part O – Arthropoda 1 – Arthropoda general features, Proarthropoda, Euarthropoda general features, Trilobitomorpha|publisher= Geological Society of America and University of Kansas Press|pages=295|chapter-url=|url=https://journals.ku.edu/InvertebratePaleo/issue/view/515|work=}}</ref><ref name="Treatise 1997">Whittington, H. B. et al. (1997) [https://journals.ku.edu/InvertebratePaleo/issue/view/516 Treatise on Invertebrate Paleontology. Part O, Revised, Volume 1 – Trilobita – Introduction, Order Agnostida, Order Redlichiida].</ref>

== List of species == * ''C. ekphymosus'' Fortey, 1975 * ''C. genacinaca'' Ross, 1951 (synonyms: ''C. ichangensis, C. vizcainoi'')<ref name=":0" /> * ''C. indentus'' Ross and Barnes, 1967 * ''C. killaryensis'' (Stubblefield, 1950) (synonym: ''Dimastocephalus killaryensis'')<ref>{{Cite journal |last=Stubblefield |first=C.J. |date=1950 |title=XXXVIII.—Dimastocephalus Stubblefield , 1950, a synonym of Carolinites Kobayashi , 1940 |url=https://www.tandfonline.com/doi/full/10.1080/00222935008654069 |journal=Annals and Magazine of Natural History |language=en |volume=3 |issue=29 |pages=451–452 |doi=10.1080/00222935008654069 |issn=0374-5481|url-access=subscription }}</ref> * ''C. macrophthalma'' (Harrington and Leanza, 1957) (synonym: ''Keidelia macrophthalma'') * ''C. pardensis'' Legg, 1976 * ''C. rugosus'' Fortey, 1975 * ''C. sibiricus'' Chugaeva, 1964 (synonym: ''C. angustagena'') * ''C. tasmaniensis'' (Etheridge, 1919) (synonyms: ''C. bulbosa'', ''C. bulbosus, C. genacinaca nevadensis'')<ref name=":0" /> Both ''C. tasmaniensis'' and ''C. genacinaca'' are globally widespread, and some studies argue that the latter species evolved from the former. The change in morphology between the two species follows a pattern which appears to be either random or complex enough to seem random. The sample size is not high enough to test a random walk model of gradualistic evolution.<ref>{{cite journal|last1= McCormick|first1= T.|last2= Fortey|first2= R.A.|author-link2 = Richard Fortey|year= 2002|title= The Ordovician trilobite ''Carolinites'', a test case for microevolution in a macrofossil lineage|journal= Palaeontology|volume= 45|issue= 2|pages= 229–257|doi=10.1111/1475-4983.00235|bibcode= 2002Palgy..45..229M|s2cid= 129305548|doi-access= free}}</ref> ''Carolinites'' was named after Caroline Creek in Tasmania, the type locality of ''C. bulbosa''.<ref>{{Cite journal |last=Kobayashi |first=Teiichi |date=1939 |title=Lower Ordovician fossils from Caroline Creek, near Latrobe, Mersey River District, Tasmania |url=https://eprints.utas.edu.au/13260/ |journal=Papers and Proceedings of the Royal Society of Tasmania |language=en |pages=67–76 |issn=0080-4703}}</ref>

== Distribution == * ''C. ekphymosus:'' Svalbard, Australia, Western United States * ''C. genacinaca'': Western United States, East Greenland, East Siberia, Novaya Zemlya, Arctic Canada, Svalbard, China, France, Australia<ref name=":0" /> * ''C. killaryensis:'' Western Ireland, Svalbard, Western United States (Basin Ranges). * ''C. macrophthalma'': Argentina * ''C. pardensis'': Argentina, Australia * ''C. rugosus'': Svalbard * ''C. sibiricus:'' Western Ireland, Siberia, Svalbard, Western United States.<ref>{{cite book|last= Fortey|first= R.A.|author-link = Richard Fortey|year= 1975|title= The Ordovician Trilobites of Spitsbergen|trans-title=II. Asaphidae, Nileidae, Raphiophoridae and Telephinidae of the Valhallfonna Formation|series= Norsk Polarinstitutt Skrifter|volume= 162|publisher= Norsk Polarinstitutt|location= Oslo}}</ref> * ''C. tasmaniensis'': Australia (Tasmania), Canada (Alberta), Svalbard, Western United States

== References == {{Reflist}}

Category:Proetida genera Category:Fossils of Canada Category:Fossils of China Category:Fossils of France Category:Fossils of Svalbard Category:Fossils of the United States Category:Ordovician trilobites of Asia Category:Ordovician trilobites of Europe Category:Ordovician trilobites of Australia Category:Ordovician trilobites of North America Category:Early Ordovician first appearances Category:Middle Ordovician extinctions Category:Paleozoic life of Alberta Category:Paleozoic life of Newfoundland and Labrador Category:Paleozoic life of the Northwest Territories Category:Fauna of the Pantropical realm Category:Telephinidae Category:Nektonic trilobites