647 First record of the genus Trichites (Mollusca, Bivalvia) from the Upper Jurassic (Kimmeridgian) of Santiago Coatepec, Puebla, Mexico Gloria Alencáster 1, * , Lourdes Omaña 1 , Celestina González-Arreola 1 , and Delfino Hernández-Láscares 2 1 Instituto de Geología, Universidad Nacional Autónoma de México, Ciudad Universitaria, Del. Coyoacán, 04510, México D. F., Mexico. 2 Departamento de Biología, Universidad Autónoma Metropolitana-Unidad Iztapalapa, Av. San Rafael Atlixco 186, Col. Vicentina, Delegación Iztapalapa, 09340 México, D. F., Mexico. * [email protected]ABSTRACT This article proves the presence of the bivalve of the genus Trichites in the Upper Jurassic of Santiago Coatepec, a small area located at the southeast of the state of Puebla, Mexico, and describes a new species, Trichites pueblaensis. This is also the first Upper Jurassic record of the genus for the American continent. The associated larger foraminifera indicate a Kimmeridgian age for this sedimentary sequence. Other important aspect is that during about two centuries it was supposed that the genus Trichites did not exist in the American continent. However, in this article is shown that this assumption was wrong, because the genus has been reported from some places of the western hemisphere. Key words: Trichites, bivalve, larger foraminifers, Upper Jurassic, Mexico. RESUMEN Este artículo prueba la presencia del bivalvo del genero Trichites, en el Jurásico Superior de Santiago Coatepec, una pequeña área localizada en el sureste del Estado de Puebla, México, y se describe una nueva especie, Trichites pueblaensis. También es el primer registro del Jurásico Superior del género en el continente americano. Los macroforaminíferos asociados indican una edad del Kimmeridgiano para esta secuencia sedimentaria. Otro aspecto importante es que durante dos siglos se supuso que el género Trichites no existió en el continente americano. Sin embargo en este artículo se demuestra que esta suposición estaba equivocada, ya que el género ha sido reportado en varios lugares del hemisferio occidental. Palabras clave: Trichites, bivalvo, macroforaminíferos, Jurásico Superior, México. Revista Mexicana de Ciencias Geológicas, v. 26, núm. 3, 2009, p. 647-657 Alencáster, G., Omaña, L., González-Arreola, C., Hernández-Láscares, D. 2009, First record of the genus Trichites (Mollusca, Bivalvia) from the Upper Jurassic (Kimmeridgian) of Santiago Coatepec, Puebla, Mexico: Revista Mexicana de Ciencias Geológicas, v. 26, núm. 3, p. 647-657.
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First record of the genus Trichites (Mollusca, Bivalvia) from the Upper Jurassic, Puebla, Mexico 647
Gloria Alencáster1, *, Lourdes Omaña1, Celestina González-Arreola1, and Delfino Hernández-Láscares2
1 Instituto de Geología, Universidad Nacional Autónoma de México, Ciudad Universitaria, Del. Coyoacán, 04510, México D. F., Mexico.
2 Departamento de Biología, Universidad Autónoma Metropolitana-Unidad Iztapalapa,Av. San Rafael Atlixco 186, Col. Vicentina, Delegación Iztapalapa, 09340 México, D. F., Mexico.
This article proves the presence of the bivalve of the genus Trichites in the Upper Jurassic of Santiago Coatepec, a small area located at the southeast of the state of Puebla, Mexico, and describes a new species, Trichites pueblaensis. This is also the first Upper Jurassic record of the genus for the American continent. The associated larger foraminifera indicate a Kimmeridgian age for this sedimentary sequence. Other important aspect is that during about two centuries it was supposed that the genus Trichites did not exist in the American continent. However, in this article is shown that this assumption was wrong, because the genus has been reported from some places of the western hemisphere.
Este artículo prueba la presencia del bivalvo del genero Trichites, en el Jurásico Superior de Santiago Coatepec, una pequeña área localizada en el sureste del Estado de Puebla, México, y se describe una nueva especie, Trichites pueblaensis. También es el primer registro del Jurásico Superior del género en el continente americano. Los macroforaminíferos asociados indican una edad del Kimmeridgiano para esta secuencia sedimentaria. Otro aspecto importante es que durante dos siglos se supuso que el género Trichites no existió en el continente americano. Sin embargo en este artículo se demuestra que esta suposición estaba equivocada, ya que el género ha sido reportado en varios lugares del hemisferio occidental.
Thesedimentarysequence(Figure2)containsatthebottomtheMatzitziFormation,whichisacontinentalunitwithanabundantandwell-preservedUpperPaleozoicflora (Silva-Pineda, 1970; Silva-Pineda et al.,1992)withlepidodendrales,calamitales,pteridospermsandferns.OverlyingthecontinentalMatzitziFormation,thereisabedofredconglomerateandabovethisthereisamarineunit,stillnotnamed,ofthickandthinsandstonelayersfromwherethemarinefaunawascollected,includingTrichites,otherbivalvesandlargegastropods.Thismolluskfaunaisassociatedwithlargerforaminifers(OmañaandGonzález-Arreola,2008),ofwhichthefollowingspeciesareofstratigraphicvalue:Alveosepta jaccardi, Everticyclammina virguliana, Rectocyclammina chouberti, Nautiloculina oolitica and Pseudocyclammina lituus.Thesespeciesarethebasetoestablishtheageofthedeposit.TheassemblageisKimmeridgian,onaccountofthestratigraphicdistributionoftheseforaminifers(Omañaet al.,2006;OmañaandGonzález-Arreola,2008).
NOMENCLATURAL NOTES
Thewordtrichites(fromlatin trichos=hair)hassev-eralmeanings,anditappliestothingsshapedlikeneedles,threads,spines,rods,etc.ofmanysizes,differentchemicalcomposition,eitherorganicorinorganic,andnaturalorarti-ficial. The most important for us, is the generic name of the studiedbivalve,whichwasnamedowingtheresemblanceofits fibrous shell wall to inorganic fibrous prismatic crystals, longknownastrichites.Theseinorganiccrystalsmaybeofdifferentnature,andarefoundindiversetypeofrocks,andofdifferentages.Forinstance,trichitesandneedlesofvesuvianitearefoundinLowerCretaceousgranites;inQuaternaryalluviumdeposits(Galuskinet al.,2003);intheCretaceousareanorthoftheColoradoRiver,trichitesarescatteredthroughthewholemass(Cragin,1892)andinUpperCretaceousrocksofWoodsonCountytherearelongulitesandtrichiteswhicharemostlikelypyroxene(Cullerset al.,1985).
Artificial trichites, also called whiskers, are commonly fabricatedasmonocrystalsofsiliconcarbide,andusedintheceramic,vitreous,andpetroleumindustries(Bagnol,1974;Bessaguetet al., 1990). But the artificial trichites are madeofmanydifferentcomponentsandhaveveryvariedapplications(IMPI,2000).
Historical background of Trichites as scientific name
TheearliestpublicationmentioningTrichiteswasbyPlot in 1677 (p. 128, pl.7, fig.7). Lhuyd was the successor ofPlotaskeeperoftheMuseumofNaturalHistoryofOxfordandpublishedTrichitesin1699(p.90),describedT. Plotii andthreespeciesmoreofthisgenus,fromtheCorallianofBurlington,nearOxford.Thesespeciesweredistinguishedbyhimwiththenumbersfrom1748to1753.Thedescriptionswereverybriefandinlatin.In1760Lhuydpublishedanexactreprintofthesamearticle.ThisreprintappearedinthesecondeditionofLhuyd’sLithophylaciiBritanici,twoyearsaftertheTentheditionofLinné´s(1758)SystemaNaturae,andtherefore,itcouldberegardedasavalidname.
However, the InternationalCodeofZoologicalNomenclaturedidnotgivevaliditytoLhuyd,becausethepublicationof1760wasareprintofastudymadein1699.Therewasneedtolookforanotherauthor.
First record of the genus Trichites (Mollusca, Bivalvia) from the Upper Jurassic, Puebla, Mexico 649
Santiago Coatepec
MEXICO CITY
CUAUTLA
TEHUACÁN
PUEBLAORIZABA
IZÚCARDE MATAMOROS
HUAJUAPAN DE LEÓN
OAXACA
VERACRUZPUEBLA
Zapotitlán Salinas
San Juan Raya
Los Reyes Metzontla
PUEBLA
PUEB
LAM
EXIC
O S
TATE
TLAXCALA
MORELOS
PUEBLA
G U L F O FM E X I C O
P A C I F I C O C E A N
M E X I C O
30 km
MEXICOCITY
99º00’
19º00’
PUEBLA
discoveredthegenus.AlsoconsideredasvalidthespeciesTrichites Plotii(Lycett,1850,p.344).Thisspeciesexisted,iswell-knownandexcellentlydescribedbyArkel(1934,p. 225, pl. 30, fig. 1-3). Furthermore, is the oldest species ofTrichites,andshouldbethetruetypespeciesofthisgenus.ArkellconsideredtoQuenstedt(1857)theauthorofTrichitesbecauseheassumedthatthestudyofTrichitesofLycett(1850)correspondedtoPinnigena.ArkelldidnotacceptthatPinnigenawasasynonymofTrichites.
T. saussurei was first discovered by De Luc in 1779 (inDeSaussure,1779-1796)underthenamePinnigene (p.192).AsthisnameisasynonymofTrichites,therealauthorofthespeciesisDeLuc,andhisnameshouldbeinparenthesisbecausethechangeofgenus:Trichites saus-surei(DeLuc,1779).ThisspeciesoccursinmanyplacesofEurope(Bayle,1878;LorioletLambert,1893,andothers).Somepaleontologistsattributedtothemtheauthorshipofthisspecies,forinstanceFavre(1867).
Abouttheprismaticshellwallstructure,PinnaandTrichites are similar in the fibrous calcite outer layer, which inPinnaisthinner,andisprovidedbyanacreouslayer(Cox,1969p.N76;Carter,1990,p.212)whichisnotpresentin
Relatedwiththisconcept,DeSaussuremadeanextensiveworkinfourtomesentitled“VoyagesdanslesAlpes” (1779-1796, of 618 pages). On the first tome, chapter 7,thereisanarticleinwhichDeLuc(1779,p.190-194)studiedapeculiarbivalvewhichhenamedPinnigene.ThisformislikeTrichitesandbecameasynonym.UndoubtedlyDeLucwasnotacquaintedwithLhuyd´swork.ThisideaisacceptedbyCox(1940)andisindisagreementtoArkell(1933),whoregardedthemastwodifferentgenera.
AtthecontrarytoVoltz,Lycett(1850,p.343-347)madeadetailedstudyofThichites,andmanifestedrespectand admiration to the first naturalists Plot and Lhuyd, who
Trichites.However,theyaresodifferentinshapetothatlevelthatisnotpossibletoconfusethem.Nevertheless,Cox(1940)includedT. plotti, T. granulatus(Sowerby,1823,p.65,pl.347)andothersimilarformsinStegoconchaBöhm,asubgenusofPinna.AlsoRollier(1914)confusedbothgen-era,sinceconsideredTrichitesasasubgenusofPinna.
him because he first gave the name Trichites,andthetypespeciesofthegenus,T. plotiiLhuyd1760,wasnamedinhishonor.Hewasbornin1640inKent,England,anddiedin1696.HeobtainedadoctoraldegreeandwroteTheNaturalHistoryofOxfordshire(Plot,1677),whichcontainsanillustratedlistoffossils,mineralsandrocks.He was professor and the first Keeper of the Museum of theSchoolofNaturalHistoryofOxford.Atthattime,thenatureoffossilswasstillmatterofdebateinEngland,andPlot,inspiteofhismanyobservationsandillustrationsoffossils,consideredthemasinorganicsaltcrystalsresemblinglivingorganisms.
First record of the genus Trichites (Mollusca, Bivalvia) from the Upper Jurassic, Puebla, Mexico 651
Diagnosis.Large-sizedspecies(about30×20cm)withvery thick fibrous outer shell wall (from 30 to 60 mm). Outlineoval,elongated,nearlyequivalveandinequilateral;bothvalvesconvex.Anteriorsidewithashortdepressedextension.Surfacesmooth.Umbocentraltoterminalandacute.Description.Theholotype(IGM-9531)isalargespecimen,ofabout30cmheightand20cmlengthwithaverythickouter wall of fibrous calcite. The long and slender prismatic fibers (from 30 mm to 60 mm long and 1 mm wide) are paralleleachother,andperpendiculartoshellsurface.Thefibrous layer shell wall is black in color, and is covered by athinandsmoothlayeroflightcreamcolor.
aconcaveanteriormargin.Theventralhalfiswiderandtheanteriormargin,intheventralhalf,isextendedandcurved; theposteriormargin isstraight,and thepos-tero-ventralandventralmarginsareacontinuouscurve.Medium-sizedspecimen(IGM-9532)hasasmoothsur-facewithprominentgrowthlines,andacentral,acutekeel.Thesespecimensshowthattheornamentationandkeelchangewithage,disappearingintheadult,probablybecauseoferosion.Measurements.Thelargest,almostcompleteleftvalve(IGM-9531)measures32cmheightand20cmlength.Asmallerspecimen(IGM-9535)withthetwovalvesjoined,ontangentialsectionhasadiameterof14cm.Thethickestfibrous layer of a large specimen (IGM-9531) measures 60 mm, and smaller individuals present a fibrous layer about 30mmthick.Materials. Thestudywasmadeonafewalmostcompletevalvesandtenfragmentsofdifferentsize.Types. HolotypeIGM-9531leftvalvealmostcomplete.Paratypes. IGM-9532, IGM-9533, IGM-9534,IGM-9535.Etymology.ThenameofthenewspeciesTrichites pue-blaensis,referstothestateofPuebla,wherethefossilswerefound, plus the latin suffix ensis, whichmeansplace.Occurrence. Thefossilswerecollectedonthethicklayersofsandstone,onthelowerpartofthecolumn,correspondingtoastratigraphicunit,stillnotformallynamed,butprovi-sionallycalledCoatepecsandstone.TheredconglomerateandtheMatzitziFormationarebelowthisunit.
DISCUSSION
Trichites plotii LhuydisthespeciesmostsimilartoT. pueblaensisand,therefore,isthespeciesphylogeneticallymostcloselyrelated.Theyresembleeachotherinthelargesize, the thick fibrous wall, lack of ornamentation, and somewhatintheshape,becausebothspeciesarebiconvexandnearlyequivalves.However,theydifferinthatT. plotiiisfranklytrapezoidal,withthedorsalhalfnarrower,thebeaklongerandmoreacute,andtheventralhalfwiderwiththemarginstraight.ThemostnotabledifferenceisthattheMexicanspeciespresentsashortdepressedextensionoftheanteriormarginofbothvalves.
T. plotii was first described by Plot in 1677 (p. 128, pl. 7, fig.7) from the Corallian (Oxfordian) of Oxfordshire, England. Arkell (1933, p. 224-228, and 1934, pl. 30, fig. 1-3)detaillydescribedthisspeciesfromtheKimmeridgian(OsmingtonOoliteSeries)ofMaltoninYorkshire.Thisspeciesisamongthelargestofthegenusandthemeasure-mentsarecomparabletothoseofthenewspecies,sinceafragmentaryspecimenhasanactualheightof258mm,sothatthecalculatedcompleteheightwasprobablybetween300to350mm.
Figure3.Trichites pueblaensisAlencástern.sp.a)HolotypeIGM-9531(X0.5)leftvalvealmostcomplete,b)ParatypeIGM-9532(X1)crosssectionofa fragment of a specimen with the umbonal area of both valves showing the fibrous layer. c)ParatypeIGM-9532(X1)onevalveofthesamespecimen,showingtheoutersurfacewiththelongitudinalcentralkeel.
a)
b)C
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1 cm
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First record of the genus Trichites (Mollusca, Bivalvia) from the Upper Jurassic, Puebla, Mexico 653
Figure4. Trichites pueblaensisAlencástern.sp.a)ParatypeIGM9535(X0.5)thetangentialsectionpresentstheuppervalvecomplete,showingthethick fibrous shell layer; the other valve presents only a small part. b) Holotype IGM-9531 (X 0.75) profile of the almost complete left valve showing the acute beak and short central gibbousity. The thick fibrous shell of the lower half of the photo belongs to another individual.
First record of the genus Trichites (Mollusca, Bivalvia) from the Upper Jurassic, Puebla, Mexico 655
surfacebutdiffersinoutlineandthemarkedlyinequivalveshell, the right valve shell flat or concave; the shell is also smaller.Trichites granulatus (Sowerby)(1823,p.65,pl.347)fromtheKimmeridgianofDorset,U.K.,issimilartoT. pueblaensisinshape,butsmaller,andintheadulthasornamentationofradialridgesandtubercles.
Switzerland,andT. marcou Choffat(1886,p.34,pl.1)fromPortugal,differfromthenewspeciesbecausetheyare smaller and inequivalves, one valve is flat and the other convex,archedinshape,andwithradialribs.
ACKNOWLEDGMENTS
Weexpressourgratitudeandadmirationtothereview-ers,Dr.SusanaDamboreneaandDr.NikolausMalchus,whomadeanexcellentworkandcontributedtotheimprove-mentofthearticle.Weareverygratefultothefollowingpersonswhoparticipatedintheelaborationofthepaper:AntonioAltamiramadesomephotos;LauraFloresTimoteotranscribedthetext,obtainedsomeinaccessiblepapersthroughinternetandinthelibrary,tooksomephotosandprepared the figures; Blanca Margarita Ramírez Garza draw thestratigraphiccolumn,andIvanErickSanchezdrawthesketch of figure 6.
Carter, J.G., 1990, Evolutionary significance of shell microstructure in the Palaeotaxodonta, Pteriomorphia and Isofilibranchia (Bivalvia:Mollusca), inCarter,J.G.(ed.),SkeletalBiomineralization:Patterns,ProcessesandEvolutionaryTrends:NewYork,VanNostrandReinhold,135-296.
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