Records of the Fossil Mammal Sinclairella, Family Apatemyidae, From the Chadronian and Orellan

William Alvin Clemens

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• Publié le: 08 décembre 2010
• Nombre de lectures: 58
• Langue: English

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Title: Records of the Fossil Mammal Sinclairella, Family Apatemyidae, From the Chadronian and Orellan

Author: William A. Clemens

Release Date: October 20, 2009 [EBook #30297]

Language: English

Character set encoding: ISO-8859-1

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Produced by Chris Curnow, Joseph Cooper, Diane Monico, and the Online Distributed Proofreading Team at http://www.pgdp.net

U NIVERSITYOF K ANSAS P UBLICATIONS M USEUMOF N ATURAL H ISTORY

Volume 14, No. 17, pp. 483-491, 2 figs. March 2, 1964

Records of the Fossil Mammal

Sinclairella, Family Apatemyidae,

From the Chadronian and Orellan

BY

WILLIAM A. CLEMENS, JR.

U NIVERSITYOF K ANSAS L AWRENCE 1964

U NIVERSITYOF K ANSAS P UBLICATIONS , M USEUMOF N ATURAL H ISTORY

Editors: E. Raymond Hall, Chairman, Henry S. Fitch, Theodore H. Eaton, Jr.

Volume 14, No. 17, pp. 483-491, 2 figs. Published March 2, 1964

U NIVERSITYOF K ANSAS Lawrence, Kansas

PRINTED BY HARRY (BUD) TIMBERLAKE, STATE PRINTER TOPEKA, KANSAS 1964

29-8587

Records of the Fossil Mammal Sinclairella, Family Apatemyidae, From the Chadronian and Orellan

BY WILLIAM A. CLEMENS, JR.

Introduction

T HEFAMILY A PATEMYIDAEHASALONGGEOCHRONOLOGICALRANGEIN N ORTH A MERICA , BEGINNINGINTHE  T ORREJONIANLAND - MAMMALAGE , BUTISREPRESENTEDBYA RELATIVELYSMALLNUMBEROFFOSSILSFOUNDATAFEWLOCALITIES . T WOFOSSILSOF O RELLANAGE , FOUNDINNORTHEASTERN C OLORADOANDDESCRIBEDHERE , DEMONSTRATE THATTHEGEOCHRONOLOGICALRANGEOFTHE A PATEMYIDAEEXTENDSINTOTHE  M IDDLE O LIGOCENE . I SOLATEDTEETHOF Sinclairella dakotensisJ EPSEN , PARTOFASAMPLEOF A  C HADRONIANLOCALFAUNACOLLECTEDBYFIELDPARTIESFROMTHE  W EBB  S CHOOLOF California, are also described.

I THANK M R . R AYMOND M. A LF , W EBB S CHOOLOF C ALIFORNIA , C LAREMONT , C ALIFORNIA , AND  D R . P ETER  R OBINSON , U NIVERSITYOF  C OLORADO M USEUM , B OULDER , C OLORADO , FORPERMITTINGMETODESCRIBETHE FOSSILSTHEYDISCOVERED . A LSO D R . R OBINSONMADEAVAILABLETHEDRAFT OFASHORTPAPERHEHADPREPAREDONTHETOOTHFOUNDIN  W ELD C OUNTY , C OLORADO ; HISWORKWASFACILITATEDBYAGRANTFROMTHE U NIVERSITYOF  C OLORADO  C OUNCILON  R ESEARCHAND  C REATIVE  W ORK . I ALSOGRATEFULLYACKNOWLEDGERECEIPTOFCRITICALDATAANDVALUABLE COMMENTSFROM  D RS . E DWIN G C. ALBREATH , G LENN J L. EPSEN , AND M ALCOLM  C. M C K ENNAWHOISCURRENTLYREVISINGTHE  P ALEOCENE APATEMYIDSANDSTUDYINGTHEPHYLOGENETICRELATIONSHIPSOFTHE FAMILY . T HEPREFIXESOFCATALOGUENUMBERSUSEDINTHETEXTIDENTIFY fossils in the collections of the following institutions: KU, Museum of N ATURAL  H ISTORY , T HE  U NIVERSITYOF  K ANSAS , L AWRENCE ; P RINCETON , P RINCETON  M USEUM , P RINCETON , N EW  J ERSEY ; RAM-UCR, R AYMOND A LF M USEUM , W EBB S CHOOLOF C ALIFORNIA , C LAREMONT , C ALIFORNIA ( THE PERMANENTREPOSITORYFORTHESESPECIMENSWILLBETHE U NIVERSITYOF C ALIFORNIA , R IVERSIDE ); AND  UCM, U NIVERSITYOF  C OLORADO  M USEUM , B OULDER , C OLORADO . T HESYSTEMOFNOTATIONSFORTEETHPRESCRIBEDFOR USEHEREISASFOLLOWS : TEETHINTHEUPPERHALFOFTHEDENTITIONARE DESIGNATEDBYACAPITALLETTERANDANUMBER ; THUS M2 ISTHENOTATION FORTHEUPPERSECONDMOLAR ; TEETHINTHELOWERHALFOFTHEDENTITION AREDESIGNATEDBYALOWER - CASELETTERANDANUMBER ; THUSP 2 ISTHE notation for the lower second premolar.

Family Apatemyidae Matthew, 1909

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Genus Sinclairella Jepsen, 1934 Sinclairella dakotensis Jepsen, 1934

T HETYPEOFTHESPECIES , P RINCETONNO . 13585, WASDISCOVEREDIN  C HADRONIAN STRATAOFTHEUPPERPARTOFTHE  C HADRON  F ORMATIONCROPPINGOUTIN  B IG  C ORRAL D RAW , APPROXIMATELY  13 MILESSOUTH - SOUTHWESTOF  S CENIC , INSOUTHWESTERN S OUTH  D AKOTA  (J EPSEN , 1934, P . 291). D ETAILEDDESCRIPTIONSOFTHETYPE SPECIMENAREGIVENINPAPERSBY J EPSEN (1934) AND S COTTAND J EPSEN (1936). Isolated teeth of Chadronian age referable toSinclairella dakotensis HAVEBEEN DISCOVEREDSUBSEQUENTLYATALOCALITYIN  N EBRASKAANDFOSSILSOF  O RELLANAGE , ALSOREFERABLETO S. dakotensis, HAVEBEENCOLLECTEDATTWOLOCALITIESIN Colorado. The sample from each locality is described separately.

Sioux County, northwestern Nebraska

Material.—RAM-UCR NOS . 381, LEFT 598, M1; LEFTM 2; 1000, RIGHT M 1; 1001, RIGHTM 2; 1079, RIGHTM 2; 1674, RIGHT  M2; AND  3013, LEFT m2.

Locality and stratigraphy.—T HESE  C HADRONIANFOSSILSWERE DISCOVEREDBY  R AYMOND  A LFANDMEMBERSOFHISFIELDPARTIESIN SEVERALHARVESTERANTMOUNDSBUILTINEXPOSURESOFTHE  C HADRON F ORMATIONIN  S EC . 26, T 33 N, R 53 W, S IOUX  C OUNTY , N EBRASKA (A LF , 1962, AND H OUGHAND A LF , 1958). T HISIS UCR LOCALITY V5403. T HECOLLECTORSCAREFULLYCONSIDEREDTHEPOSSIBILITYTHATSOMEOFTHE FOSSILSFOUNDINTHEANTMOUNDSWERECOLLECTEDFROMYOUNGERSTRATA BYTHEHARVESTERANTSANDCONCLUDEDTHISWASUNLIKELY (A LF , PERSONAL communication).

Description and comments.—T HECUSPSOF  RAM-UCR NO . 381, A LEFT M1, ARESHARPANDTHEWEAR - FACETSRESULTINGFROMOCCLUSIONWITH THELOWERDENTITIONARESMALL . T HEPARACONULEISALOW , ILL - DEFINED CUSPONTHEANTERIORMARGINOFTHECROWN ; AMETACONULEISNOT PRESENT . A SMOOTHSTYLARSHELFISPRESENTLABIALTOTHEMETACONE . T HECROWNWASSUPPORTEDBYTHREEROOTS . T HEREARENO interradicular crests.

T HECROWNOF  RAM-UCR NO . 1674, ARIGHT  M2, ISHEAVILYABRADED ANDMANYMORPHOLOGICALDETAILSOFTHECUSPSHAVEBEENDESTROYED . L OWINTERRADICULARCRESTSLINKEDTHETHREEROOTSOFTHETOOTHWITHA LOW , CENTRALPROMINENCE . A SWASTHECASEWITH RAM-UCR NO . 381, NOSIGNIFICANTDIFFERENCESCOULDBEFOUNDINCOMPARISONSWITH illustrations of the teeth preserved in Princeton no. 13585.

RAM-UCR NOS . 598, 1001, 1079, AND 3013 ALLAPPEARTOBEM 2' S . T HETALONIDSOFTHESETEETHARENOTELONGATED , THEIRTRIGONIDSHAVE QUADRILATERALOUTLINES , ANDTHEPARACONIDSARESMALLBUTPROMINENT , BLADELIKECUSPS . T HETRIGONIDOF RAM-UCR 1000 ISELONGATEDAND THEPARACONIDISAMINUTECUSP ; THETOOTHCLOSELYRESEMBLESTHEM 1 of the type ofSinclairella dakotensis.

Logan County, northeastern Colorado

Material.—KU NO . 11210 ( FIG . 1), AFRAGMENTOFALEFTMAXILLARY containing P4 and M1-2.

Locality and stratigraphy.—T HEFOSSILWASFOUNDINTHECENTEROFTHE W-1/2, Sec. 21, T 11 N, R 53 W, Logan County, Colorado, " ... in the BEDBELOW Agnotocastor BED , C EDAR C REEK M EMBER ...." (R ONALD H. P INE , 1958, FIELDNOTESONFILEATTHE U NIVERSITYOF K ANSAS ). T HEBED SODEFINEDISPARTOFUNIT 3 INTHELOWERDIVISIONOFTHE C EDAR C REEK M EMBER , ASSUBDIVIDEDBY  G ALBREATH  (1953:25) INSTRATIGRAPHIC section XII. The fauna obtained from unit 3 is of Orellan age.

[Pg 487]

Fig. 1. Sinclairella dakotensis Jepsen, KU no. 11210, fragment of left maxillary with P4 and M1-2; Orellan, Logan County, Colorado; drawings by Mrs. Judith Hood: a, labial view; b, occlusal view; both approximately × 9.

Description and comments.—P4 OF  KU NO . 11210 HASALARGE POSTEROLINGUALCUSPSEPARATEDFROMTHEMAINCUSPBYADISTINCT GROOVE , WHICHDEEPENSPOSTERIORLY . T HEPOSTEROLINGUALCUSPIS SUPPORTEDBYTHEBROADPOSTERIORROOT . P4 OFTHETYPESPECIMENOF Sinclairella dakotensis ISDESCRIBED  (J EPSEN , 1934, P . 392) AS HAVINGANOVALOUTLINEATTHEBASEOFTHECROWN , ANDASMALL , POSTEROLINGUALCUSP . A CHIPOFENAMELISMISSINGFROMTHEPOSTERIOR SLOPEOFTHEMAINCUSPOFTHE  P4 OF  KU NO . 11210. T HEANTERIOR SLOPEOFTHEMAINCUSPISFLATTENED , POSSIBLYTHERESULTOFWEAR , AND THEREISNOEVIDENCEOFAGROOVELIKETHATPRESENTONTHE P4 OFTHE type specimen.

O NLYAFEWDIFFERENCESWEREFOUNDBETWEENTHEMOLARSPRESERVEDIN KU NO . 11210 ANDTHEIRCOUNTERPARTSINTHETYPESPECIMEN . A STYLAR SHELFISPRESENTLABIALTOTHEMETACONEOF M1 OF KU NO . 11210, BUT , UNLIKETHETYPE , ITSSURFACEISSMOOTHANDTHEREISNOEVIDENCEOF CUSPS . O FTHETHREESMALLSTYLARCUSPSONTHESTYLARSHELFOF M2 THE SMALLESTISINTHEPOSITIONOFAMESOSTYLE . T HE  M2 LACKSACHIPOF ENAMELFROMTHELINGUALSURFACEOFTHEHYPOCONE . U NLIKETHE M2 OF P RINCETONNO . 13585, INOCCLUSALVIEWTHEPOSTERIORMARGINOFTHE M2 OF  KU NO . 11210 ISCONVEXPOSTERIORTOTHEMETACONE . T HE ANTERIOREDGEOFTHEBASEOFTHEZYGOMATICARCHOF  KU NO . 11210 WASDORSALTO  M2. T HESHALLOWOVALDEPRESSIONINTHEMAXILLARY dorsal to M1 might be the result of post-mortem distortion.

T HEMOLARSPRESERVEDIN KU NO . 11210 ANDTHEIRCOUNTERPARTSINTHE TYPESPECIMENDONOTAPPEARTOBESIGNIFICANTLYDIFFERENTINSIZE ( TABLE 1) ORMORPHOLOGYOFTHECUSPS . T HEONLYDIFFERENCEBETWEEN THETWOSPECIMENSTHATMIGHTBEOFCLASSIFICATORYSIGNIFICANCEISTHE DIFFERENCEINSIZEOFTHEPOSTEROLINGUALCUSPOF A P4. TPRESENTTHE RANGEOFINTRASPECIFICVARIATIONINTHEMORPHOLOGYOF  P4 HASNOT BEENDOCUMENTEDFORANYSPECIESOFAPATEMYID . T HEEVOLUTIONARY TRENDORTRENDSOFTHEAPATEMYIDS  M C K ENNA , 1960, P . 48 FOR

[Pg 488]

PROGRESSIVEREDUCTIONOFFUNCTIONOFP 4 PROBABLYWEREPARALLELEDBY SIMILARTRENDSINTHEEVOLUTIONOFTHE I P4. FSO , THEINTRASPECIFIC VARIATIONINTHEMORPHOLOGYOF  P4 COULDBEEXPECTEDTOBE SOMEWHATGREATERTHANTHATOFTHEUPPERMOLARS , FOREXAMPLE . T HE MORPHOLOGICALDIFFERENCEBETWEENTHE  P4' SOFTHETYPEOF Sinclairella dakotensis AND KU NO . 11210 ISNOTEXTREMEANDDOES NOTEXCEEDTHERANGEOFINTRASPECIFICVARIATIONTHATCOULDBE EXPECTEDFORTHISELEMENTOFTHEDENTITION . T HECLOSERESEMBLANCES INSIZEANDMORPHOLOGYBETWEENTHE M1-2 OF P RINCETONNO . 13585 AND KU NO . 11210 ALSOFAVORIDENTIFICATIONOFTHELATTERASPARTOFA member of an Orellan population ofSinclairella dakotensis.

Weld County, northeastern Colorado

Material.—UCM NO . 20173 ( FIG . 2), ISA right M2.

Locality and stratigraphy.—The TOOTHWAS DISCOVEREDATTHE M ELLINGERLOCALITY , S EC . 17, T 11 N, R 65 W, W ELD C OUNTY , C OLORADO . T HE M ELLINGERLOCALITYIS INTHE  C EDAR  C REEK M EMBER , W HITE R IVER  F ORMATION , ANDITSFAUNAIS CONSIDEREDTOBEOF O RELLANAGE (P ATTERSONAND M C G REW , 1937, AND Galbreath, 1953). Fig. 2. Sinclairella dakotensis Jepsen, UCM Description and no. 21073, right M2; Orellan, Weld County, comments.—UCM Colorado; drawing by Mrs. Judith Hood: NO . 21073, WHICHIS occlusal view, approximately × 9. MOREHEAVILY ABRADEDTHAN  KU no. 11210, shows no evidence of a stylar cusp either anterolabial TO THEMETACONEORINTHEPOSITIONOFAMESOSTYLE . A SMALLSTYLARCUSP ISPRESENTANTEROLABIALTOTHEPARACONE . A NOTCHTHATAPPEARSTO HAVEBEENCUTTHROUGHTHEENAMELOFTHEPOSTEROLABIALCORNEROFTHE CROWNCOULDHAVERECEIVEDTHEPARASTYLARAPEXOF  M3. A SIMILAR NOTCHISNOTPRESENTONTHE M2 OF KU NO . 11210 NORINDICATEDINTHE ILLUSTRATIONSOFTHE  M2 OF  P RINCETONNO . 13585. T HECORONAL DIMENSIONSOF  UCM NO . 21073 ( TABLE  1) DONOTAPPEARTODIFFER SIGNIFICANTLYFROMTHOSEOFTHE  M2' SOF  KU NO . 11210 ANDTHETYPE specimen ofSinclairella dakotensis.

Comments

W ITHTHEDISCOVERYOF  O RELLANAPATEMYIDSTHEGEOCHRONOLOGICALRANGEOFTHE FAMILYIN  N ORTH A MERICAISSHOWNTOEXTENDFROMTHE  T ORREJONIANTHROUGHTHE O RELLANLAND - MAMMALAGES . T HEDISCOVERIESREPORTEDHEREENLARGETHE O LIGOCENERECORDOFAPATEMYIDSTOINCLUDENOTONLYTHETYPESPECIMENOF Sinclairella dakotensis, ASKULLANDASSOCIATEDMANDIBLEFROM  S OUTH  D AKOTA , BUTALSOSEVENISOLATEDTEETH , REPRESENTINGATLEASTTWOINDIVIDUALS , FROMA C HADRONIANFOSSILLOCALITYIN  N EBRASKAANDONESPECIMENFROMEACHOFTWO O RELLANFOSSILLOCALITIESINNORTHEASTERN  C OLORADO . S IMPSON  (1944:73, AND 1953:127) PRESENTEDTABULATIONSOFTHEPUBLISHEDRECORDSOF  A MERICAN APATEMYIDSANDSUGGESTEDTHEDATAINDICATEDTHEPOPULATIONSOFTHESE MAMMALSWEREOFSMALLSIZETHROUGHOUTTHEHISTORYOFTHEFAMILY . T HEFEWPRE - O LIGOCENEOCCURRENCESOFAPATEMYIDSDESCRIBEDSUBSEQUENTLY ( NOTE M C K ENNA , 1960, FIGS . 3-10, ANDP . 48) ANDOCCURRENCESDESCRIBEDHERETENDTOREINFORCE S IMPSON ' SINTERPRETATION . T HISINTERPRETATIONMAYHAVETOBEMODIFIEDTOSOME DEGREE , HOWEVER , WHENCURRENTSTUDIESOFCOLLECTIONSOFPRE -O LIGOCENE apatemyids are completed (McKenna, personal communication).

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