Bumastusis anextinctgenusofcorynexochidtrilobiteswhich existed from the EarlyOrdovicianperiodto the LateSilurianperiod.[1]They were relatively large trilobites, reaching a length of 6 in (15 cm). They were distinctive for their highly globular, smooth-surfacedexoskeleton.They possessed well-developed, large compound eyes and were believed to have dwelled in shallow-water sediments in life.
| Bumastus Temporal range:
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|---|---|
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| Anartist's reconstructionofBumastus | |
Scientific classification
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | †Trilobita |
| Order: | †Corynexochida |
| Family: | †Styginidae |
| Subfamily: | †Bumastinae |
| Genus: | †Bumastus Murchison,1839 |
| Type species | |
| Bumastus barriensis Murchison,1839
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| Species | |
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Seetext | |
Bumastusfossils have been found inNorthandSouth America,Europe,Asia,andAustralia.They are classified under thefamilyStyginidaein theorderCorynexochida.[2]
Description
editBumastusis a large trilobite, reaching a length of 6 in (15 cm).[3][4]The body is oblong-oval, about twice as long as it is wide,[5]It had a strongly convex profile, giving it its distinctive globular appearance.[6]
Like all trilobites, the body is divided into three functional segments known astagmata(singular: tagma), which in turn are divided into three lobes - the central lobe (axial) and two lateral lobes (pleural). Aside from faint depressions in thethorax,Bumastusis unusual in that the three lobes are barely discernible from each other.[7][8]The axial lobe ofBumastusis also very broad in comparison to the pleural lobes.[6]
Thecephalon(head segment) is very large and strongly convex. Thefacial sutures(the divisions by which the cephalon splits when the trilobitemolts) isopisthoparian,[9]with the suture ending along the hind cephalic margin.[10]Thegenalanglesof the cephalon - the edges where the lateral and rear margins of the cephalon meet - are rounded.[11]The cephalon iseffaced(smooth and mostly featureless), anevolutionary trendalso seen inIllaenusandTrimerus,though not as pronounced as that ofBumastus.Theglabella(the central lobe of the head) is almost fused to thefixigena.[9]
The thorax has ten narrow segments[5]while thepygidium(the tail) is smooth and very rounded.[5]It isisopygous- that is, the pygidium is about the same size as the cephalon.[12]The pygidium completely lacks any visible trilobation. It is usually semicircular in shape but can be pointed in some species likeB. niagarensis.
The smoothcompound eyesare large and peculiarly well-developed. This, along with the rounded contours of their body, suggests thatBumastusmay have spent most of its time buried in sediment with its eyes protruding.[9]
The surface of the exoskeleton of most species is studded with minute punctures.[13]
Paleoecology
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The rounded smooth shape ofBumastus,as well as the almost completeeffacementof its cephalon, is believed to have been an adaptation for burrowing.[8]The presence of well-developed eyes also suggest that it may have kept them above the substrate by burrowing intosedimentsbackward. They are situated in such a way that they provide the trilobite with a semicircularfield of visionon each side, keeping them aware of movements near them.[9]
Bumastuscould also curl up (known as enrollment) into a ball-like shape. This is believed to indicate that its habitat might have been the shallow waters of theLittoral zone.Whenwaveswash them out from the sediments it could simply roll up and be carried along. Enrollment protects the softer body parts below the exoskeleton, while the spherical shape offers the least resistance to wave action.[9]
Bumastusis abottom-dwelling(nektobenthic) trilobite.[11]It was probably eitherdetritivorous,feeding on decomposing organic material drifting down in the currents,[6]orcarnivorous.[15]
Occurrence
editBumastusexisted during thePaleozoic era,from theArenigianepochof the Early Ordovician period to theLudlow epochof the Late Silurian period (approximately 478.6 ± 1.7 to 418.7 ± 2.8million years ago).[2][16][17]Theirfossilscan be found worldwide.[18]
Specimens have been recorded from the Silurian ofArgentina,Canada,theCzech Republic,Estonia,Greenland,Kazakhstan,Norway,theRussian Federation,Sweden,Ukraine,theUnited Kingdom,and theUnited States.[5][15]
They can also be found in the Ordovician formations ofAustralia,Canada,China,[19]the Czech Republic, the Russian Federation,Spain,theUnited States;with specific occurrences from theDobrotivianage/stage(Llandeiloage) of China andFrance,and theWhiterockianstage of the United States.[15]
They are typically found inreef limestone,though they are sometimes found incrinoidallimestone.[9][17]
Discovery
editBumastuswas first described by theScottishgeologist,Sir Roderick Impey Murchisonin 1839. Thetype species,Bumastus barriensiswas recovered from theCoalbrookdaleFormationof theWenlock GroupinEngland.[20]
Murchison first believed that the specimens he discovered (including a large 5 in (13 cm) by 3.5 in (8.9 cm) specimen) belonged to the genusIsotelusbecause of the size, shape, and almost featureless cephalon. But he noted the almost absent trilobation of body and the difference in the number of segments in the thorax (10 inB. barriensisand 8 inIsotelus). He also recognized its close relationship with the genusIllaenus,but ultimately classified it as a new genus based on the extremely advanced state ofeffacementin the cephalon ofBumastus.[7]
The genus is so named because of its curious resemblance to a large roundgrape.[21]It comes fromLatinbūmastus(large grapes that resemble theuddersof a cow), which in turn came fromGreekβοῦς(bous- cow) andμαστός(mastós- breasts). The word was familiar in theEnglish languageduring Murchison's time, being a word encountered in book two ofVirgil'sGeorgics.[22][23]
Thespecific nameof the type species,barriensis,roughly meaning "of Barr", comes from its common name among collectors. It was then known as the "Barr trilobite" referring to the plentiful occurrence ofB. barriensisin the limestone formations ofGreat Barr,Staffordshire.[13]
Taxonomy
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Bumastusis classified under thefamilyStyginidaeby P.A. Jell and J.M. Adrain in 2003,[20]and under theorderCorynexochidaof trilobites byJack Sepkoskiin 2002.[2]
Species
editListed below are thespeciesclassified underBumastusand the countries of their recordedtype localities.[25][26]The list is incomplete and may be inaccurate.
- Bumastus armatus- United States
- Bumastus barriensis- Estonia, Kazakhstan, Ukraine, United Kingdom, United States
- Bumastus beckeri- United States
- Bumastus bellmanni- Argentina
- Bumastus bouchardi- Czech Republic, Ukraine
- Bumastus chicagoensis- United States
- Bumastus cuniculus- United States
- Bumastus cuniculus|Bumastus cuniculus vieillensis- Canada
- Bumastus dayi- United States
- Bumastus erastusi- Canada
- Bumastus globosus- Canada, United States (Synonym (biology)|synonym?:Illaenus globosus)
- Bumastus graftonensis- United States
- Bumastus hornyi- Czech Republic
- Bumastus indeterminatus- Canada
- Bumastus insignis- United Kingdom, United States
- Bumastus ioxus- United States
- Bumastus lenzi- Canada
- Bumastus limbatus- United States
- Bumastus milleri- United States
- Bumastus niagarensis- United States
- Bumastus orbicaudatus- Canada, United States
- Bumastus phrix- Estonia, Ukraine, United Kingdom
- Bumastus springfieldensis- United States
- Bumastus sulcatus- Sweden
- Bumastus tenuirugosus- Canada
- Bumastus tenuis- United States
- Bumastus transversalis- United States
- Bumastus trentonensis- United States
See also
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References
edit- ^"Bumastus".Encyclopædia Britannica.RetrievedApril 11,2011.
- ^abcJ. J. Sepkoski (2002)."A compendium of fossil marine animal genera (Trilobita entry)".Bulletins of American Paleontology.364.Paleontological Research Institution: 560.ISBN978-0-87710-450-6.Archived fromthe originalon September 5, 2006.RetrievedApril 13,2011.
- ^Christopher G. Morris (1992).Academic Press dictionary of science and technology.Gulf Professional Publishing. p. 325.ISBN978-0-12-200400-1.
- ^Douglas L. Shrake (2005)."Ohio Trilobites"(PDF).Geofacts.5.Ohio Department of Natural Resources, Division of Geological Survey. Archived fromthe original(PDF)on 2011-06-28.RetrievedApril 12,2011.
- ^abcdPaul D. Taylor; David N. Lewis (2007).Fossil Invertebrates.Harvard University Press. p. 143.ISBN978-0-674-02574-5.
- ^abcIrving H. Tesmer; Jerold C. Bastedo (1981).Colossal cataract: the geologic history of Niagara Falls.SUNY Press.ISBN978-0-87395-522-5.
- ^abRoderick Impey Murchison (1839).The Silurian System.Vol. Part II. J. Murray.RetrievedApril 12,2011.
- ^abPat Vickers Rich;Mildred Adams Fenton;Carroll Lane Fenton;Thomas Hewitt Rich (1989).The fossil book: a record of prehistoric life.Dover books on animals. Courier Dover Publications. pp. 198, 201, 210.ISBN978-0-486-29371-4.
- ^abcdefgRhona M. Black (1988).The elements of palaeontology(2 ed.). Cambridge University Press. pp. 151–152.ISBN978-0-521-34836-2.
- ^Samuel M. Gon III (November 12, 2009)."Trilobite Facial Sutures".A Guide to the Orders of Trilobites.RetrievedApril 12,2011.
- ^abBritannica Educational Publishing (2010).The Paleozoic Era: Diversification of Plant and Animal Life.The Rosen Publishing Group. p. 119.ISBN978-1-61530-196-6.
- ^Samuel M. Gon III (November 12, 2009)."The Pygidium".A Guide to the Orders of Trilobites.RetrievedApril 12,2011.
- ^abDavid Page(1865).Handbook of geological terms, geology and physical geography.W. Blackwood and sons. p. 121.
- ^Otto Theodore Walter (1924)."Trilobites of Iowa and some Related Paleozoic Forms".Iowa Geological Survey Annual Report.31.Iowa Geiological Survey. Archived fromthe originalon October 6, 2011.RetrievedApril 12,2011.
- ^abc"†Bumastus Murchison1839 (trilobite) ".Paleobiology Database.RetrievedApril 12,2011.[permanent dead link]
- ^Samuel M. Gon III & Enrico Bonino."Systematic Relationships and Chronological Extent of the nine Trilobite Orders"(PDF).A Guide to the Orders of Trilobites. Archived fromthe original(PDF)on August 23, 2011.RetrievedApril 12,2011.
- ^abA. A. Manten (1971).Silurian reefs of Gotland.Elsevier.ISBN978-0-444-40706-1.
- ^Arthur Clive Bishop; Alan Robert Woolley; William Roger Hamilton (1999).Guide to minerals, rocks and fossils.Cambridge University Press. p.276.ISBN978-0-521-77881-7.
- ^Wen-tang Zhang; Pei-ji Chen; A. R. Palmer (2003).Biostratigraphy of China.Elsevier. pp. 198, 221.ISBN978-7-03-011314-6.
- ^abP.A. Jell & J.M. Adrain (2002)."Available generic names for trilobites"(PDF).Memoirs of the Queensland Museum.48(2). Queensland Museum.ISSN0079-8835.RetrievedApril 12,2011.
- ^Gideon A. Mantell (1854).The Medals of Creation: Or, First Lessons in Geology and the Study of Organic Remains.H. G. Bohn. p. 537.ISBN978-0-405-12718-2.
- ^Charles Rollin (1829).The history of the arts and sciences of the ancients.Blackie, Fullarton.
- ^Joab Goldsmith Cooper (1866).Opera, or, The works of Virgil: with copious notes, mythological.Sheldon & co.
- ^"Bumastus niagarensisTrilobite ".Louisville Fossils. 2 June 2010.RetrievedApril 12,2011.
- ^"Classification of Genus:Bumastus".Global Biodiversity Information Facility.RetrievedApril 12,2011.[permanent dead link]
- ^Robert Maurice Owens (1995).Catalogue of type, figured and cited fossils in the National Museum of Wales: Supplement 1971-1994.National Museum Wales. pp. 44–45.ISBN978-0-7200-0422-9.
External links
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Media related toBumastusat Wikimedia Commons- Order CorynexochidafromA Guide to the Orders of Trilobites
