Editing Trilobite (section)

==Fossil distribution==
[[File:Cruziana2.jpg|thumb|left|''[[Cruziana]]'', fossil trilobite-burrowing trace]]
[[File:BioclastsBiosparite.jpg|thumb|A trilobite fragment (T) in a thin-section of an Ordovician [[limestone]]; E=[[echinoderm]]; scale bar is 2&nbsp;mm.]]
[[File:RusophycusOrdovician.jpg|thumb|''[[Rusophycus]]'', a "resting trace" of a trilobite; Ordovician of southern Ohio. Scale bar is 10&nbsp;mm.]]
[[File:Joachim Barrande01.jpg|thumb|{{center|Plate from Barrande's work ''Système silurien du centre de la Bohême''}}]]
Trilobites appear to have been primarily marine organisms, since the fossilized remains of trilobites are always found in rocks containing fossils of other salt-water animals such as brachiopods, crinoids, and corals. Some trackways suggest trilobites made at least temporary excursions onto land.<ref name=Nature505264e/> Within the marine paleoenvironment, trilobites were found in a broad range from extremely shallow water to very deep water. Trilobites, like brachiopods, crinoids, and corals, are found on all modern continents, and occupied every ancient ocean from which Paleozoic fossils have been collected.<ref>{{cite news | author=Burns, Jasper | title=Fossil Collecting in the Mid-Atlantic States | work=The Johns Hopkins University Press | page=5 | date=1991}}</ref> The remnants of trilobites can range from the preserved body to pieces of the exoskeleton, which it shed in the process known as ecdysis. In addition, the tracks left behind by trilobites living on the sea floor are often preserved as [[trace fossil]]s.

There are three main forms of trace fossils associated with trilobites: ''Rusophycus'', ''Cruziana'' and ''Diplichnites''—such trace fossils represent the preserved life activity of trilobites active upon the sea floor. ''[[Rusophycus]]'', the resting trace, are trilobite excavations involving little or no forward movement and ethological interpretations suggest resting, protection and hunting.<ref name=baldwin77>{{citation | last=Baldwin | first=C. T. | year=1977 | title=''Rusophycus morgati'': an asaphid produced trace fossil from the Cambro-Ordovician of Brittany and Northwest Spain |journal=[[Journal of Paleontology]] |volume=51 | issue=2 |pages=411–425 | jstor=1303619}}</ref> ''[[Cruziana]]'', the feeding trace, are furrows through the sediment, which are believed to represent the movement of trilobites while deposit feeding.<ref name=garlock&isaacson77>{{Citation | last1=Garlock | first1=T. L. | last2=Isaacson | first2=P. E. | title=An Occurrence of a ''Cruziana'' Population in the Moyer Ridge Member of the Bloomsberg Formation (Late Silurian)-Snyder County, Pennsylvania |journal=[[Journal of Paleontology]] | volume=51 | issue=2 | pages=282–287 | year=1977 | jstor=1303607}}</ref> Many of the ''[[Diplichnites]]'' fossils are believed to be traces made by trilobites walking on the sediment surface.<ref name="garlock&isaacson77" /> Care must be taken as similar trace fossils are recorded in freshwater<ref name=woolfe90>{{citation | last=Woolfe | first=K. J. | year=1990 | title=Trace fossils as paleoenvironmental indicators in the Taylor Group (Devonian) of Antarctica | journal=[[Palaeogeography, Palaeoclimatology, Palaeoecology]] | volume=80 | pages=301–310 | doi=10.1016/0031-0182(90)90139-X | issue=3–4| bibcode=1990PPP....80..301W }}</ref> and post-Paleozoic deposits,<ref name=wzonneveld02>{{cite journal |last1=Zonneveld |first1=John-Paul |last2=Pemberton |first2=S. George |last3=Saunders |first3=Thomas D. A. |last4=Pickerill |first4=Ronald K. |title=Large, Robust Cruziana from the Middle Triassic of Northeastern British Columbia: Ethologic, Biostratigraphic, and Paleobiologic Significance |journal=PALAIOS |date=1 October 2002 |volume=17 |issue=5 |pages=435–448 |doi=10.1669/0883-1351(2002)017<0435:LRCFTM>2.0.CO;2 |bibcode=2002Palai..17..435Z |s2cid=131613992 }}</ref> representing non-trilobite origins.

Trilobite fossils are found worldwide, with thousands of known species. Because they appeared quickly in geological time, and moulted like other arthropods, trilobites serve as excellent [[List of index fossils|index fossils]], enabling geologists to date the age of the rocks in which they are found. They were among the first fossils to attract widespread attention, and new species are being discovered every year.

[[File:Penn Dixie.jpg|thumb|Fossil hunters look for trilobites and other fossils in Penn Dixie Fossil Park and Nature Preserve.]]

In the United States, the best open-to-the-public collection of trilobites is located in [[Hamburg, New York]].  The shale quarry, informally known as Penn Dixie, stopped mining in the 1960s. The large amounts of trilobites were discovered in the 1970s by Dan Cooper.<ref name="Raeke">{{cite news|author=Caroyln Raeke|author2=Tom Earnst|author3=Mike Vogel|author4=Harold Mcneil|title=Town Board, Natural History Society on Quest to Save Hamburg Fossil Trove |url=http://buffalonews.com/1995/08/18/town-board-natural-history-society-on-quest-to-save-hamburg-fossil-trove/ |newspaper=The Buffalo News |date=August 18, 1995}}</ref> As a well-known rock collector, he incited scientific and public interest in the location.<ref name="Brien">{{cite news|author=Barbara O'Brien |title=They'll never run out of fossils at Penn Dixie |url= http://buffalonews.com/2013/10/13/theyll-never-run-out-of-fossils-at-penn-dixie/|newspaper=The Buffalo News|access-date=October 13, 2013|date=2013-10-13 }}</ref> The fossils are dated to the [[Givetian]] (387.2–382.7{{nbsp}}million years ago) when the [[Western New York|Western New York Region]] was 30 degrees south of the equator and completely covered in water.<ref name="Gryta">{{cite news|author=Matt Gryta|author2=Tom Ernst|title=Drive Seeks to Preserve Fossil Site Hamburg Quarry Considered Valuable |url= http://buffalonews.com/1990/03/04/drive-seeks-to-preserve-fossil-site-hamburg-quarry-considered-valuable/ |newspaper=The Buffalo News |date=March 4, 1990}}</ref> The site was purchased from Vincent C. Bonerb by the Town of Hamburg with the cooperation of the Hamburg Natural History Society to protect the land from development.<ref name="Raeke"/> In 1994, the quarry became Penn Dixie Fossil Park & Nature Reserve when they received 501(c)3 status and was opened for visitation and collection of trilobite samples. The two most common found samples are ''Eldredgeops rana'' and ''Greenops''.<ref name="Penn">{{cite web|title=Trilobites |url=https://penndixie.org/trilobites/ |work=Penn Dixie Fossil Park & Nature Preserve|access-date=July 16, 2017|date=2016-03-15 }}</ref>

A famous location for trilobite fossils in the [[United Kingdom]] is [[Wren's Nest]], [[Dudley]], in the [[West Midlands (county)|West Midlands]], where ''[[Calymene blumenbachii]]'' is found in the [[Silurian]] [[Wenlock Group]]. This trilobite is featured on the town's [[coat of arms]] and was named the ''Dudley Bug'' or ''Dudley Locust'' by quarrymen who once worked the now abandoned [[limestone]] quarries. [[Llandrindod Wells]], [[Powys]], [[Wales]], is another famous trilobite location. The well-known ''[[Elrathia|Elrathia kingi]]'' trilobite is found in abundance in the [[Cambrian]] [[Wheeler Shale]] of [[Utah]].<ref name="Gaines&Droser03">{{Citation |journal=[[Geology (journal)|Geology]] |title=Paleoecology of the familiar trilobite ''Elrathia kingii'': an early exaerobic zone inhabitant |author1=[[Robert R. Gaines]] |author2=Mary L. Droser |year=2003 |url=http://earthsciences.ucr.edu/docs/Gaines&Droser_2003.pdf | volume=31 |pages=941–4 |doi=10.1130/G19926.1 |issue=11|bibcode = 2003Geo....31..941G }}</ref>

Spectacularly preserved trilobite fossils, often showing soft body parts (legs, gills, antennae, etc.) have been found in [[British Columbia]], Canada (the Cambrian [[Burgess Shale]] and similar localities); [[New York (state)|New York]], US (Ordovician [[Walcott–Rust quarry]], near [[Russia, New York]], and [[Beecher's Trilobite Bed]], near [[Rome, New York]]); China (Lower Cambrian [[Maotianshan Shales]] near [[Chengjiang County|Chengjiang]]); [[Germany]] (the Devonian [[Hunsrück Slates]] near [[Bundenbach]]) and, much more rarely, in trilobite-bearing strata in Utah (Wheeler Shale and other formations), [[Ontario]], and Manuels River, [[Newfoundland and Labrador]].

Sites in [[Morocco]] also yield very well-preserved trilobites, many buried in mudslides alive and so perfectly preserved.  An industry has developed around their recovery, leading to controversies about practices in restoral.<ref>{{Cite web|url=https://www.trilobiti.com/post/a-quick-guide-to-identifying-fake-trilobites|title=A quick guide to identifying fake trilobites!|date=29 October 2019}}</ref> The variety of eye and upper body forms and fragile protuberances is best known from these samples preserved similarly to bodies in Pompeii.

The French palaeontologist [[Joachim Barrande]] (1799–1883) carried out his landmark study of trilobites in the Cambrian, Ordovician and Silurian of [[Bohemia]], publishing the first volume of ''Système silurien du centre de la Bohême'' in 1852.