Fossil porcupine (Mammalia, Rodentia, Erethizontidae) from El Golfo de Santa Clara, Sonora, Mexico, with a review of the taxonomy of the North American erethizontids

2016·17 MB·English

by  David R Sussman

Contributions in Science, 524:1-29 20 July 2016
Fossil Porcupine (Mammalia, Rodentia, Erethizontidae) erom El
Goleo de Santa Clara, Sonora, Mexico, with a Review oe the
Q Taxonomy oe the North American Erethizontids^
11
L52X
David R. Sussman,'’^ Fred W. Croxen III,^ H. Gregory McDonald,"^
and Christopher A. Shaw^
ABSTRACT. Amongthe South American animalsthatentered North America followingtheestablishmentofthe Panamanian land bridge
were members ofthe family Erethizontidae. The early fossil record ofthis group m North America is sparse and so the discovery offossil
porcupines from the Middle Pleistocene (Irvingtonian) fauna of El Golfo de Santa Clara, Sonora, Mexico, provides significant new
information on the history of these animals in North America. The taxonomic assignment of the new material required a review of the
systematics ofNorth American erethizontids. Based on the most common element preserved, we have restricted our study to features of
the dentary that can be used to distinguish the Neotropical porcupine Coendoit from the North American porcupine Erethizon,
supplemented by an examination ofdifferences in thecaudal vertebrae that also distinguish the two genera. The results ofour study lead
us to recognize the presence of both Coendoti and Erethizon in the fossil record of North America and to assign the El Golfo fossils to
Coendoti cf. C. kleini. We also reassign the taxa E. poyeri and E. klemi, previously reported from Florida, to the genus Coendou.
Further, we reassign specimens previously identified as Erethizon dorsatiim from Irvingtonian faunas in Florida and Aguascalientes,
Mexico, tothegenus Coendou.
Incontrasttopreviousstudiesinwhicha linearevolution fromCoendoutoErethizonwasproposed, wepresentanalternativemodel for
the origin ofthe North American genus Erethizon. Wepropose the existence oftwo different migration pathways through Mexico. In the
west, a branch dispersed north along the north-south mountain ranges into northern North America, resulting in the evolution of
modern Erethizon in the more temperate part of the continent. In the east, a second branch followed the Gulf Coast into Florida,
resultingin the establishmentofan eastern population ofCoendou in thesubtropical part ofNorth America, a population thateventually
becameextinct.
INTRODUCTION
partial dentaries, teeth, and a single humerus that represent six-
individual erethizontids, the subject ofthis paper.
An Early to Middle Pleistocene fauna has been recovered from Asdiscussed by Croxenetal. (2007),establishingtheexactgeo-
badlands near the small fishing village ofEl Golfo de Santa Clara logic age of these fossils is difficult. The fossil assemblage is
(El Golfo), Sonora, Mexico.Thebadlands,whichcoverabout 100 assumed to represent a single paleobiota, but the lack of inter-
square miles, are formed by the erosion of sediments deposited bedded ashes prevents determining its age radiometrically.
in the delta of the Colorado River at the northern end of the Although studies of the magnetostratigraphy have not produced
GulfofCalifornia overthepastfour or fivemillionyears (Dorsey, definitive results, preliminary data suggest that the fossil-bearing
2006). These sand-dominated sediments, with interbeds of silt, sediments are reversely magnetized (F.W. Croxen, personal com-
clay, and gravelly sands, were subjected to a series of tectonic munication, 2015). If this is the case, the Matuyama reversed
uplift events (Colletta and Ortlieb, 1984; Pacheco et ah, 2006) epoch (2.588-0.781 Ma) (Cohen et al., 2013) is the only reversal
followed bywaterand wind erosion and theconsequentexposure of an age appropriate to the vertebrate assemblage at El Golfo.
of large numbers of vertebrate and botanical fossils (Croxen This assemblage correlates with other faunal assemblages asso-
et ah, 2007). ciated with the Irvingtonian North American Land Mammal Age
Over the last20 years, an organized effort to recover these fos- (NALMA) (Bell et ah, 2004), particularly with the fauna from
sils has been undertaken by Professor bred Croxen and Christo- the Irvingtonian portion of the stratigraphic sequence at Anza-
pher Shaw under permit from the government of Mexico and Borrego State Park in California (Cassiliano, 1999;Jefferson and
under the oversight of the Reserva de la Biosfera Alto Golfo de Lindsay, 2006). Fossils of Mammuthus meridionalis, Megalonyx
California y Delta del Rio Colorado. At present, about 11,500 wheatleyi, Nothrotheriops texamis, and Sigmodon curtisi are
individual fossils have been recovered and identified, representing present, but Bison is not and, given the large available sample
more than 130 different vertebrate taxa. Among these fossils are size,the absenceofBison does notseem to bea collection artifact.
Some Blancan taxa {Canis lepophagiis, Felts rexroadensis,
Sigmodon curtisi) are present and may be considered remnant
’URL: www.nhm.org/scholarlypublications
^Department of Biology, Arizona Western College, Yuma, Arizona populations but suggest an earlier rather than later age for the
85367, USA. fauna atEl Golfo. However,the presenceofMammuthussuggests
^Department of Geology, Arizona Western College, Yuma, Arizona an age not older than about 1.35 Ma, the earliest well-dated
85367, USA. appearance of Mammuthus in North America (Bell et ah, 2004).
United States Bureau of Land Management, Salt Lake City, Utah, With this information, an age range of0.781 Ma (youngest possi-
84^10D1e,paUrStAm.ent of Rancho La Brea, La Brea Tar Pits and Museum, ble Matuyama) to 1.35 Ma seems a reasonable estimate for the
Natural History MuseumofLosAngeles County,LosAngeles,California fauna ofEl Golfo.
90036, USA. Fossil porcupines in North America were reviewed by White
^Correspondingauthor: DavidR. Sussman,E-mail:[email protected] (1968, 1970). Based on his examination of a variety of dental
©Natural History Museum ofLos Angeles County, 2016
ISSN 0459-8113 (Print); 2165-1868 (Online) NOV 23 2016
j
2 Contributions in Science, Number 524 Sussman et al.: North American Erethizontidae
and skeletal features and on measurements in modern and fossil thatdistinguishthetwo livinggenera and sopermitacomparative
specimens, White concluded thatthe earliest ofthese fossil porcu- evaluationoftheerethizontidfossilsthathavebeenfound onboth
pines should bereferred to theextantNeotropicalgenus Coendon continents.
and that the modern North American genus Erethizon evolved in The extant North American porcupine, Erethizon dorsatnm, is
North America from an immigrantspecies ofCoendou. The fossil monotypic. Its distribution includes boreal forests as far north as
North American erethizontids were subsequently reevaluated by Canada and Alaska and the forests (and occasionally deserts) of
Frazier (1981), including the specimens studied by White plus the western, north-central, and northeastern United States, and
newly discovered material, and Frazier reached the conclusion extends south into the mountainous regions of northern Mexico.
that, in contrast to White, all the North American fossils belong Although E. dorsatnm may be found in open scrub, it prefers
in the genus Erethizon. forested habitat. It is arboreal and utilizes its muscular tail exten-
Since the work of Frazier, most researchers have accepted the sivelyinitstree-climbingactivities.Thetail,however,isnotprehen-
assignment of fossil North American porcupines to the genus sile, in contrastto the tail ofits Neotropical relative Coendon. The
Erethizon (e.g., Morgan and White, 1995; Flulbert, 1997; Alb- diet ofErethizon consists preferentially ofthe leaves and shoots of
right, 1999). Currently, five species of North American porcu- trees in hardwood forests when available, but it also possesses the
pines are recognized from the fossil record (Frazier, 1981; well-known ability to eat the cambium layer of tree bark, a trait
Hulbert, 1997). These taxa include Erethizon bathygnathnm and thatallowsittosurvivewintersindeciduousandconiferousforests.
E. cascoensis (which could be considered bathygnathnm) from Notably, it is the only erethizontid known to have adapted to sub-
western North America, E. poyeri and E. kleini from. Florida, arctic conditions and it survives the harsh winters of Canada and
and fossils of the living species, E. dorsatnm, from several local- the northern parts of the United States not by hibernating but by
ities in the United States and Mexico. However, there is notcom- continuing to forage for food (Roze, 1989).
pleteagreement regardingthegenericidentification ofthesefossils Subsequent to the arrival ofthe original immigrants, winters in
andthediscoveryoftheporcupine fossilsatEl Golfo promptedus North America became progressively colder, with the onset ulti-
to reevaluate the taxonomy of the fossil North American porcu- mately of severe glacial conditions. The substantial metabolic
pines, in order to assign the El Golfo fossils appropriately. and physical changes evidently necessary to allow a Neotropical
The ancestors ofmodernErethizon firstenteredNorthAmerica porcupine to survive in such an environment form the crux of
from South America after the formation ofthe Panamanian land the argument we propose below that the generic name Erethizon
bridge. The timing of the closure of the isthmus, which defines
mustapplyonlytoporcupinesthathaveevolvedinNorthAmerica.
the earliest possible time for the porcupines’ entry into North Differences of opinion exist regarding the taxonomy of living
America, is important for understanding their subsequent evolu- South and Central American porcupines. Morphologic and
tion in North America. Previously, the closure was thought to
genetic evidence support the conclusion that Neotropical porcu-
have occurred around 3.5 Ma. (Webb, 1985; Flynn et ah, 2005). pines are monophyletic, withthe exception ofChaetomys (a mor-
However, studies utilizing different dating methodologies, one
phologically distinct animal with no close living relatives) (Voss
nbyowMosnutggeesstetaaml.or(e20c15o)mpalnedx tahnedoptrhoetrrabcyteBdahciosntorety aolf. c(l2o0s1u5r)e,, and Angermann, 1997; Voss and da Silva, 2001; Voss, 2011;
possibly beginning in the middle Miocene or earlier, with asso- Vossetah, 2013). AllNeotropicalporcupines (except Chaetomys)
are included in the genus Coendon byVoss. Consequently, Sphig-
ciated faunaldispersaleventsin bothdirections,thelastmajordis-
cpreerastaeleavmeanntyo-cmciulrlriionng-yaebaorutga6pM(a6.MTaheosreeeaarrlliieerrtdoataebso,uitfa2c.c5urMaat.e), gsnyrnnosnyamnsdoEfcChoiennopdroonc.taInatrhei,s pinaptehrisweschfoelmleo,wctohnesindoemreendcljautnuiroer
duringwhichporcupines mayhaveenteredNorthAmerica butfor proposed by Voss.
whichwe have no fossil record. Other studies relatedto the ances- The extant species of Coendon live in tropical and subtropical
try and early history ofNorth American porcupines include those forests and savannahs of South and Central America. All living
ofVilela et al. (2009) and Voss et al. (2013), who have proposed, species of Coendon (13 or more) are substantially smaller in
based on mitochondrial molecular clocks, that the lineages ances- body size than Erethizon, with some being quite diminutive.
tral tomodern Coendon and Erethizon separated from acommon Although knowledge of their natural history is generally sparse,
ancestor at some point during the late Miocene. it appears that the ecology of all species of Coendon is similar.
Two questions need to be answered regarding Plio-Pleistocene They eat the flowers, leaves, stems, and fruit ofthe forests, which
erethizontid fossils in North America. The first, addressed pre- are available year round. They may also eat roots, tubers, and
viously by Sussman (2011), relates to the assignment of a 2.5-Ma insects (Woods, 1984; Emmons and Eeer, 1997; Eisenberg and
dentary from the Uquia Formation in Argentina to the genus Redford, 1999). Anecdotal reports that Coendon, like Erethizon,
ErethizonbyRegueroetal. (2007).Theissueiswhethertheoriginal eatsbarkhavenotbeenwelldocumented (L.H.Emmons,personal
immigrants to North America had enough morphological traits to communication, 2006). They are arboreal and utilize prehensile
assignthemtothegenusErethizon,astheassignmentoftheUquian tails for clinging to branches. As discussed by Voss et al. (2013),
fossil to Erethizon suggests is possible, or whether the distinguish- even the short tail of C. rnfescens displays evidence of being pre-
ing hallmarks of Erethizon evolved after the immigrants entered hensile, although it is at the shortend ofa spectrum ofprehensile
NorthAmericaandwereexposedtothetemperateNorthAmerican tail lengths possessed by the various Coendou species.
environment. Second, if the morphological traits characteristic of Modern Erethizon has been found as far south as southern
Erethizon evolved in North America and are only present in the Sonora and Chihuahua (Jones and Genoways, 1968) and Coen-
North American taxon, do any of the North American fossils don is common in Yucatan and is found as far north as San Luis
show traits that might suggest a closer generic relationship to the Potosi on the east side of the Mexican mainland (Emmons and
Neotropical porcupine Coendou than to Erethizon} The first ques- Feer, 1997) and inthestateofMichoacan onthewest (Monterru-
tion is discussed in the previously mentioned Sussman paper bio-Rico et al., 2010), but a distance of several hundred miles in
(2011), with the conclusion that the Uquian fossil more properly central Mexico separates the modern northern and southern por-
belongs in the genus Coendou. The second will be examined here. cupinegenera (Fig. 1). Thiscontrasts withthegeographicallycon-
The assignment of the porcupines from El Golfo to a genus tiguous populations of porcupines that presumably existed after
requires precise definitions of the skeletal and dental characters the original dispersal event(s) into North America.
Contributions in Science, Number 524 Sussman et al.; North American Erethizontidae 3
METHODS AND MATERIALS OnlytheverysmallestE.rethizonequalsthevery largestCoendou
in size and there is minimal overlap at those extremes. White
In order to find consistent anatomical and proportional differ- (1970:10) found fossil measurements of the cheek-tooth row
ences between the two extant genera {Erethizon and Coendou), that fall in the range of modern E.rethtzon but nevertheless
we studied numerous examples of modern animals, including assigned these fossils to the genus Coendou. Frazier (1981:24-
nine species of Coendou (Appendix 1). We concentrated on den- 25) included these values (approximately the same as White’s)
taries and teeth because these predominate among the El Golfo inaclassificationbydiscriminantanalysisandconcludedthefos-
fossil specimens, are among the most commonly preserved parts sils should be assigned to thegenus E.rethizon.
of porcupine fossils from other localities, and would seem to 2. Ratio of size of p4 to ml: A p4/ml ratio smaller than about
have sufficient anatomical complexity to permit the recognition 1.10 indicates Coendou, while a p4/ml ratio larger than about
of consistent differences between the genera. Dentaries are also 1.36 indicates Erethizon. Although most Coendoutendtoward
thetypespecimens forthreeoftheextinctNorthAmerican species smaller ratios and Erethizon toward larger, those individuals
[E. bathygnatlmm (USNM 13684), E. poyeri (UF 121740), and with a ratio between 1.10 and 1.36 cannot be reliably distin-
zE.onktliedinfios(sUilFs2f1r4o7m3)]Uqamn'da t(oMoAurCNkno5w3l7e6d)geanadreTatrhiejaonl(yMeNreHthMi- gwuiidsthhesdofbyp4thaisndtrmailt,. aWrhriitveed (a1t96a8:s8i)m,ilamreacsounrcliunsgioonn,lywhitlhee
TAR 695, 696; Hoffstetter, 1963) in South America. Frazier (1981) did not address this trait.
Table 1 provides the dentary measurements we made on mod- 3. Ratio of anterior-posterior (A-P) diameter to lateral width of
teironnsp.orWcuhpeirnees,usweiftulh,thweeir aalvseoragpeesr,forarnmgeeds,raantidosstoarndamrudltidpelviiead- linowtehreirnactiisoorosf: IAn-Pmoddieamrenteardutlot pwoirdctuhpibneetsw,etehnerteheistawnoogveenrelraap
length X width oftooth measurements and these are also shown at 1.2, but incisors with a greater ratio are Coendou and those
in Table 1. Values are also shown for the fossils from E! Golfo with a lesser ratio are Erethizon. Porcupine incisors, in contrast
i((nTTeaadbblleeth4e2)),,caaFnulddoarCliudmvaebre(trTealbbralaneed3oC)f,avpeCoa,rlciMfuaoprriynnileaas,ndtIod(aTihadoeb,nlteiAfg5y)u.adsWicfeafleierexennatcmee-ss tbootmhollaerngsthanadndprienmoAi-aPrsa,ndconlattienruael dtioamgertoewrsafftoerrmeurcuphtiiofnnoitn
tbheetDwefteoasesinilletdhreedcneoosrncdprriiepsthmieionnnsisimloaefla,hnotdhweprwdeihefefnpeserierlnefcoeprsomrmecdaupyoiunbreetmraeeilvase.saulArilnetgmh.eonutgsh atblielocnoafuasttehaeimanconiirsmeoarlrs’aospfildiCfeor;aettnheidstohpuarnoadptuphceeeaysrwatioddielfnefnilgcatutlheterynaliilnnyutashsientgAh-etPhainsdiitrmreaacil-t
are found in Appendix 2. ge.r,o1w.s0irnattoioa)dcurlotshsoosedc,tisotnart(iPnSgMoff14in19n7e,wb1o4r2n01s,wi1t4h20a2,squ1a4r2e03()i.
ABBREVIATIONS and then progressively elongating in the A-P direction over the
next 1-2 years (ratio 1.1: AMNH 262274 with m2 and m3
ABDSP Anza-BorregoDesertState Park, California unerupted, FMNH 14182 with partially erupted m3, LACM
FFADA:MMWMANNCNMSHH TAAFDrrmheiieneczrvkoiFeincrCeaoallMndWlueeMMcssuutteisseouerenmn,uummAoCfmoooleNfflraeNiNtgacaeuta,truunerYrauMaallnmuHdasHi,iesSstcuAtoiromreriyny,zco,eofN,nCNeaDhaweitncuYvaroegarrolk,,,HICilNsoltleionoworriysa,Ydoork i7r7ne54t3aghi0ran6votewwhteirihtarthijpoduasvptet4onefiraln0nes.d,9c-ra1ool.lsnsl1t-)yh.sreeBaceentciimoamonualaslalesrsso)qwf.uiattThrhhiesepsaiehpnarpcpmaieasronearensstnatdduipEls4trcs’erste(hp7ia(1izn.oceo.nyf,
New York,NewYork adults) were included in the analysis.
IGM Instituto de Geologia, Universidad Nacional Autonoma de While both White (1970:11) and Frazier (1981:14)
Mexico, Mexico City, Me.xico measured incisors, neither discussed this trait.
rVCM ImperialValley College Museum Collection,Anza-Borrego 4. The orientation of the cheek-tooth row relative to the incisor
DesertStatePark, California (Fig. 3): The results ofour examination ofthis trait differ con-
L1.ACM Natural History MuseumofLosAngeles County, Los siderably from those of both White (1968, 1970) and Frazier
LA(CCITM) ANInnasgtteuilrteuastle,HoCifaslTtieofcroyhrnnMioaluosgeyu,mLoosfALnogselAensg,elCeasliCfoorunnitay, California c(h19e8e1k)-.toTothherroewasaonndstfhoerinthciissormaoyntrheelastaemteositdheelifeacitn dtihfaftertehnet
MACN Museo deHistoria Natural de Buenos Aires,Argentina horizontal and vertical planes and so slightly different measur-
MNA MuseumofNorthernArizona, Flagstaff,Arizona ing techniques or differing rotational positions of the dentary
MNHN Museum National d’Histoire Naturelle, Paris, France may result in significantly different results. Nevertheless, our
PSM University ofPugetSound Slater MuseumofNatural technique resulted in 72 of 73 dentaries of Coendou having
History,Tacoma, Washington cheek-tooth axes directed lateral to the incisor and one-third
UUFMMP UFnliovreirdsaiMtyusofeMuimchoifgNaantuMrualseHuismtoorfy,PaGlaeionnetsovillolgey,,FAlnornida toefc5hn8iqauxee,sadicrheceteekd-tmoeodtihalalxyisinthEartetrhuinzsonm.edTihauls,touttihlieziinngciosuorr
Arbor, Michigan
UO University ofOregon Condon Museum ofGeology,Eugene, in an individual porcupine strongly suggests Erethizon, while
Oregon a large sample ofdentaries from a given population ofporcu-
USNM National MuseumofNatural History,Washington, D.C. pines, all with axes running lateral to the incisor, may suggest
ZMUC Zoological Museum, UniversityofCopenhagen, Denmark Coendou. Ourresultsshowthatmodern dentariesofErethizon
possess a distinct trend toward anterior convergence of the
cheek-tooth rows, a trend not present in the dentaries ofmod-
RESULTS ern Coendou, in which the cheek-tooth rows remain parallel.
5. The amount of anterior extension (procumbency) of the inci-
MODERN DENTARIES sors (Figs. 2B, 2C, 4): As first described by Sussman (2011),
Inthe moderndentaries,we found fivetraits thatare useful in dis- the lower incisors of Coendou extend anteriorly an average of
tinguishing the two genera. Refer to Appendix2 fordefinitions of 7 degrees more than those of Erethizon. This difference
terms and measuring techniques. The five traits are listed below. appears to provide an important means for distinguishing
between the two genera. When viewed in conjunction with
The length of the cheek-tooth row (Fig. 2A): It is immediately thetendency forthecheek-tooth rows in Erethizon toconverge
apparentthatthismeasurementisdefinitiveinlivingporcupines. medially toward the incisor and the stronger, square-shaped
4 Contributions in Science, Number 524 Sussman et al.; North American Erethizontidae
cross section ofthe incisors in Erethizon, this traitsuggests the observed in one or two posteriorly located caudal vertebrae in a
MNA
possibility of an evolutionary process in Erethizon, first noted small number of individuals (e.g., Z9.509; Fig. 5D). It is
by White (1970), which provides a strengthened jaw mechan- probable that these bifurcated transverse processes in the caudal
ism as compared with Coendoti. vertebrae of Erethizon are equivalent to, and vestiges of, those
seen in the more centrally located vertebrae found in the longer
Other measurements in Table i, excepting size, do not provide tails ofprehensile-tailed ancestors ofErethizon priorto the evolu-
distinctive differences betweenthegenera. Inparticular,the length tionary loss of the most posterior caudal vertebrae. That is, the
of the diastema relative to the length ofthe cheek-tooth row (the trait in Neotropical porcupines that produces the foramina and
lengthofthecheek-toothrowshould notchangeonce alltheteeth bifurcated processes may also exist in Erethizon but is only rarely
have erupted) cannot be used to help diagnose a genus or species observed because of the evolutionary loss of the involved
because the length of the diastema is variable, being sometimes vertebrae.
shorter and sometimes longer than the tooth row. This variation In the following discussion of the various fossil erethizontid
appears to be age (and therefore growth)-related: in Erethizon, dentaries, we compare the fossils to the five traits we identified
our measurements show the diastema/tooth-row ratios to be as distinguishing modern Erethizon from modern Coendou as il-
0.50 in juveniles (n=13), 0.57 in young adults (n=37), and 0.62 lustrated in Table 6.
in older adults (n=ll); in Coendou the values are 0.44 (n=8),
p0i.n5e3s(hna=v3e6)l,ongaenrdd0i.a5s8te(mna=s5r2e)l.atiTvheutso,tohne cahveeerka-gteo,otolhdrerowpocrocmu-- SIZE AS A TRAITTO IDENTIEY A GENUS
pared with those ofyounger animals.
salTshuerfaancgeledsueoftoscmraasttcihceastoionntwheereenastmuedlieodfbtyheWchhieteek-(t1o9o6t8h),ocmcelau-- ALagloarageSapnotratiEoosnsiolfs vFerraszuiser’SshelatregruCmaevnetFfoosrsilasssigning all North
sured from the longitudinal axis of the tooth row. Differences American porcupine fossils to the genus Erethizon is based on a
werefound betweenthetwogenera, providinganother diagnostic statistical comparison of cranial and mandibular measurements
trait. However, these differences were not considered by Frazier ofthe fossils withsamples ofextantErethizon and Coendou (Fra-
(1981) sufficient to assist in generic identification. Our attempts zier, 1981:21-26). His data demonstrate that the fossils are the
to examine the scratches suggest thatscratches may have multiple same size as Erethizon. Similarly, Frazier stated (1981:28) that
angles on the same tooth; curved scratcheswere also noted,prob- “(i)ncisor enamel thickness in Erethizon is significantly greater
ably because the porcupines do not always chew in a strictly thanin Coendou.”UsingFrazier’smeasurements ofA-Pdiameters
of incisors and his measurements of enamel thickness, we calcu-
straight back-and-forth or side-to-side motion, butwith a circular
pcloentsrcirbauttcihodniarsecwteiloln.sImfitghihstcbheeweixpnegc—tmeodt.ioInnaisddtihteiocnas,et,htehle—onnmgulatxii-s la5an.td6ed%fto(hue0n.pd2e7rimctemnt/to4a.gb8eemom5f).t7fhoe%rdEifroaermtehtCieozroenno.fdoTthuhues(i,n0c.sii2sno1crmesmtt/hh3ea.tp7eimsrmcee)nnatamaneglde
ofindividual cheek teeth frequently but not consistently varies
from the axisoftheentiretoothrow,producing anotherdifficulty ofenamel thickness isvirtuallyidentical in bothgenera, thesignif-
in using these scratches, particularly in isolated teeth. As a result, icantly different absolute values ofenamel thickness in the genera
we conclude that we are not able to utilize the enamel scratches reflect only differences in the sizes ofthe animals, as in the other
measurements mentioned here.
diagnostically.
In general, we do not accept that size, in and of itself, is suffi-
cient to determine to which oftwo genera an individual specimen
MODERN TAILS should be assigned. Also needed aresignificantdifferencesinmor-
phologyand functionthatmayreflectsignificantecologicaldiffer-
The number ofcaudal vertebrae in modern porcupine tails, while ences. In contrast, a species ofdiffering size isolated from related
variable, appears to depend on whether the tail is prehensile or species geographically (e.g., Mcmimuthus exilis] or in time (Coen-
not. In 19 Coendou, we saw tails with as few as 22 and 24 verte- dou kleim as mentioned below) may be considered a distinct spe-
brae, but in most specimens the number ranged from 26 to 34. cies (but not genus).
Thirteen of these tails are from specimens of C. prehensilis. We To support our contention that the physical differences we
did not see any Coendou for which the number of caudals is as found between modern North American and Neotropical porcu-
small asthenumbersobservedinthenonprehensiletailsofErethi- pines are real and actually distinguish the genera and that they
zon: 13-17 in 19 tails described by Sutton (1972) and 8-16 by us are not related to size, we examined the previously unpublished
(n=14). The series of vertebrae in tails of Coendou decreases in latePleistocene/HolocenefossilsofErethizondorsatumfromShel-
size gradually in more posterior positions, whereas in Erethizon ter Cave, New Mexico, and contemporaneous fossils from Lagoa
the caudals show a rapid progression from larger to smaller for Santa, Brazil (Coendou magmis) (Winge, 1888; Hansen, 2012)
the length ofthe tail. (Table 7). It is importantto notethatthe fossils fromLagoa Santa
Caudals of Coendou have single transverse processes in the are the same size or somewhat larger than modern Erethizon and
most anterior vertebrae, but beginning variably at about the are much larger than any modern species of Coendou (Table 1).
12th to 15th vertebra, foramina (probably neurovascular) appear Looking at the five distinguishing characters described above,
in the transverse processes and the processes then gradually pro- the fossils from Lagoa Santa are about 10% larger than those
gress to complete bifurcation around the 17th to the 20th verte- from Shelter Cave; the single p4/ml ratio from Shelter Cave is
bra. The bifurcations persist for a few vertebrae and then 1.31, high but within the range of modern Coendou. The five
foramina may reappear in the transverse processes ofmore poste- fossils from Lagoa Santa average a p4/ml ratio of 1.08 (Coen-
rior vertebrae and may or may notpersist nearly to the end ofthe dou-only),withthreeofthemfallingwithintherangethatisexclu-
tail (Fig. 5). The exact vertebrae involved in these changes in the sively Coendou and two being in the area of overlap of the two
transverse processes varies in individual animals, but includes genera.
about one-third to one-halfofthe vertebrae. Four out of five adult incisors from Shelter Cave have the
We saw no foramina in the transverse processes ofcaudal ver- cross-sectional shape of Erethizon and the fifth is in the area of
tebrae of modern Erethizon and there were no bifurcations in overlap betweenthetwogenera. Threeincisors in adultdentaries
most animals. However, bifurcated transverse processes were from Lagoa Santa are either in the area of overlap (n=2) or are
7
Contributions in Science, Number 524 Sussman et al.: North American Erethizontidae 5
Coendou in shape (n=l). A fourth incisor is in a dentary that Applying the results from our study of modern porcupines to
retainsa dp4 and,as predicted,hasa squareshape. Weexamined the fossil remains from E4 Ciolfo demonstrates the following: The
six isolated incisors and, although we could not definitively lengths of the cheek-tooth rows of the two measurable FI Golfo
determine the animals’ ages, the two largest incisors (larger fossils (AWC 10858 and 12197) are intermediate in size between
than the others hy 2-3 mm in the A-P direction and 0.6-1. £. dorsatum and C. prehensilis, equaling the smallest Erethizon
mm
in the lateral direction, thus probably adults) have large and the largest Coendou.
ratios (1.4, 1..5) as in Coendouand thesmallerremainingincisors None ofthe fossils had both p4 and an intact ml, so that ratio
have ratiosof 1.1,with theexception ofonethathasa 1.3 [Coen- could not be calculated.
doii) ratio. Four fossil incisors could be measured. Two had an A-P/lateral
The cheek-tooth axes of three fossils from Shelter Cave ratioof 1.1 and two were 1.2. Both dentaries with incisor ratiosof
extend lateral to the incisor; two axes are centered on the inci- 1.1 are missingthe (d)p4’s but have lightly worn m3’s (suggesting
sor. In the dentaries from Lagoa Santa, the axes ofall six extend a young adult), so this measurement provides equivocal results in
laterally. the fossils.
All five dentaries from Shelter Cave with measurable incisor Two dentaries (AWC 10858 and 12197) have cheek-tooth row
angles of procumbency fall into the Erethizon-on\y range. Eight axes that run lateral to the incisor, providing inconclusive generic
measurements from five individuals from Lagoa Santa all are in evidence.
the Coendou-on\y range except for one buccal and one lingual AWC 10858 and 14810 have measurable incisor angles ofpro-
measurement, both of which fall within the areas of overlap cumbency that fall well within the range of Coendou, hut are at
between Coendou and Erethizon (Fig. 2D). the highest values for Erethizon.
An assembled series of disarticulated caudals from the fossils A single p4 and six molars from four different animals all mea-
from Lagoa Santa produced a tail with 31 vertebrae. Some of sure either smaller than the smallest modern Erethizon or smaller
the vertebrae contain foramina in the transverse processes and than the mean for Erethizon. Two are the size of the largest
others show bifurcated transverse processes (Fig. 6). Except for Coendou.
its larger size, the tail appears to us to be identical to thatofmod- Although incomplete, the humerus is from an adult, appears to
ern Coendou. be larger than modern species of Coendou, and may be about the
In summary, the fossils from Lagoa Santa are larger than those size ofa small Erethizon.
from Shelter Cave. In the remaining traits, measurements that do No caudal vertebrae from El Golfo have yet been recovered.
not fall into the range of overlap between the two genera are, in Insummary,thefossilsfromEl Golfo fall inanintermediatesize
the case of Lagoa Santa, exclusively in the range of Coendou range between modern Erethizon and Coendou, have anterior
and, for Shelter Cave, exclusively in the range of Erethizon. In extension of the lower incisors as in modern Coendou, and have
addition, the porcupines from Lagoa Santa possessed a prehensile notraitsexclusivetoErethizon.Theyare thesamesizeas C. kleini
tail, a trait found only in modern Coendou. from Florida (discussed below).
Thus, a comparison of the fossils from Shelter Cave with the Although the porcupines from El Golfo have few distinctive
cfoasnsildsisftirnogmuiLshagtohae tSwaontgaensehroaw,sretghaartdloeusrs odfefsiinzee.dAchlaarragcetesrpiesctiiecss cphoymsbiicnaaltitroanitsofinathCeoefnosdsoilus-twyepehaivnecisfoorunpdr,otchuemybednocyp,osslaetsesratlhley
of Coendou lived in SouthAmerica into late Pleistocene/Holocene directed cheek-tooth axes, and the absence ofany traits definitely
times, demonstrating that size alone is not sufficient to diagnose restricted to Erethizon. Additional evidence regarding their iden-
fossil Erethizon. tity may be derived from the paleoenvironment of the El Golfo
area at the time the porcupines lived. The recovery of remains of
FOSSIL PORCUPINES fan palm (Washmgtonia sp.), giant tortoise (Hesperotestudo sp.),
El Golfo de Santa Clara crocodile (Crocodylus sp.), beaded lizard (Heloderma sp.), boa
Fossils of porcupine from El Golfo de Santa Clara include the constrictor [Constrictor constrictor), crested guan [Penelope sp.),
following: flamingo [Phoenicopterus sp.), and giant anteater [Myrmeco-
AWC 10858: Right dentary fragment with incisor and m2 and phaga tridactyla) atEl Golfo implies thatthe annual regional tem-
m3; m3 less worn than m2, suggesting a young adult; ascending perature supported tropical to subtropical environments (Mead
ramus missing; symphysis and diastema intact (Fig. 7). and Shaw, 2011; Shaw et ah, 2013).
AWC 12197: Left dentary fragment with a worn p4; incisor Steadman (2011) notes that, regarding the avifauna ofEl Golfo,
broken off at top of bony alveolus but its diameters are measur- “[t]he more tropical biogeographic affinity of some of the birds
able; ml broken offat top ofbony alveolus and occlusal surfaces agreeswiththatsuggested forcertainassociatedreptileandmammal
of m2 and m3 are broken off; most of ascending ramus missing fossils.” This subtropical ecosystem, of which the El Golfo porcu-
and symphysis and diastema, while mostly intact, have missing pineswereapart,supportsourinterpretationthattheyare Coendou
portions (Fig. 8). and not Erethizon, based on the known habitat differences of the
AWC 13592: Worn right ml in small fragment of mandibu- two modern genera. There do not appear to be any convincing rea-
lar bone. sonsto think thatthe fossil porcupines atEl Golfo werepreadapted
AWC
14810: Right dentary fragment with partially broken for cold-weather tolerance or that they subsequently acquired it
incisor and ml-3 but missing p4; m3 minimally worn, suggesting while living in a subtropical climate, cold-weather tolerance being
young adult; missing diastema, symphysis, and ascending ramus a defining characteristic ofliving Erethizon.
(Fig. 9). The temporal and physical isolation of the porcupines at
IGM 10199 (collected byH. Garbani ca. 1980): isolatedbroken El Golfo from the other fossil porcupines in North America
right incisor. raises the possibility that they were part of a dispersal event
AWC
12540: Right humerus, about one-third of proximal end to North Americ—a distinct from that of earlier dispersals. As a
missing; epiphyseal suture fully closed, length offragment 67 mm. group, their size somewhat smaller than other early to mid-
Becauseoftheerosionofthecompactsurfacebone,other meaning- Pleistocene fossil porcupines, except for C. kleini in Florida,
ful measurements cannot be made (Fig. 10). and smal—ler than modern Erethizon but larger than extant
Measurements ofthe fossils are provided in Table 2. Coendou perhaps represents an intermediate stage in a
2
6 Contributions in Science, Number 524 Sussman et al.: North American Erethizontidae
diminution in size of Coendoii that apparently occurred at some theanimal.Wehavenotbeengivenaccesstothisfossilandsocan-
point during the Pleistocene but for which we know ofno South not at this point make an independent judgment regarding its
American fossil record. taxonomic assignment.
WeconcludethattheEl Golfoporcupinesshould beassigned to Except for size and the one incisor ratio, none of the studied
the Neotropical genus Coendou and further, due to their overall traits in the fossils from Florida fall into a range exclusive to
similarity to C. kleini, we assign them to Coendou cf. C. kleini, Erethizon. The large p4/ml ratios trend towards Erethizon but
pending the discovery ofmore diagnostic material to help clarify there are modern Coendou with the same ratios. On the other
the species designation. hand,thesmallp4/ml ratioofE. poyerifallswellwithintherange
of Coendou. The sixtooth-rowaxes, all directed laterally, suggest
Florida Coendou, because in a population of Erethizon one or two axes
We examined porcupines from late Blancan and Irvingtonianfau- could be expected to be medial.
nas from five sites in Florida previously identified as Erethizon ThestrongestevidenceintheFloridafossilsisfound,first,inthe
poyeri (found at Haile 7C, ca. 2 Ma) (Hulbert, 1997), E. kleini incisor angles of procumbency, which are uniformly in the range
(Inglis lA, ca. 1.9 Ma) (Frazier, 1981), E. dorsatum (Haile 16A, of Coendou, and, second, as described by Hastings et al. (2006),
ca. 1.6 Ma.) (Morgan and White, 1995), E. dorsatum (Feisey in the presence in the caudal vertebrae of bifurcated transverse
3A, ca. 1.5 Ma.) (Morgan and White, 1995), and E. dorsatum processes acco—mpanied by the suggestion of approximately 30
(Coleman2A, 0.6-0.3 Ma.) (MorganandWhite, 1995). SeeTable total vertebrae in other words, a prehensile tail, a distinguishing
3 for measurements. trait ofmodern Coendou.
The lengths ofthe cheek-tooth rows are long, at or above those The porcupines from Florida we examined show no evi-
of Erethizon, except for two fossils from Inglis lA, which are dence of the mandibular modifications present in modern
somewhat smaller, falling between the sizes of modern Coendou Erethizon, that is, the anterior convergence of the cheek-
and Erethizon. tooth row relative to the incisor and the more acute angle
The E. poyeri fossil (UF 121740) has a p4/ml ratio of 0.96, in of incisor procumbency in Erethizon. These modifications
the range ofmodern Coendou. The four other measurable fossils we interpret as helping to allow Erethizon to survive in
all havelarger ratios,noneofwhichexceedtherangeofCoendou, northern climates by eating the cambium of trees when no
but trending toward Erethizon. other food is available. Except for their larger size, the fossil
Three incisors haveA-P/lateral ratios of 1.1 and one has a ratio porcupines from Florida cannot be distinguished from mod-
of 1.2. Ofthe three with ratios of 1.1, one has worn molars (UF ern Neotropical Coendou. We therefore conclude there is suf-
21473), suggesting an older adult, one has a broken (d)p4 and ficient reason to reassign the Florida porcupines found at
lightly worn ml and m2 but is missing m3, possibly a juvenile Haile 7C, Haile 7G, Inglis lA, Feisey 3A, and Haile 16A to
or young adult (UF 135669), and the third has an unworn p4 the genus Coendou. We assign the nondiagnostic Coleman 2A
and lightly worn ml and m2, a young adult (UF 21490). With dentary fragment to Coendou also, as a relict population,
the exception of the single older adult, these measurements are acknowledging that its young age may represent instead a south-
not diagnostic. ern range extension of Erethizon.
The axes of six cheek-tooth rows relative to the incisor, repre- The fossils from Inglis lA were described as a new species
senting three of the five sites we studied, are measurable (Fig. (£. kleini) by Frazier (1981) based on their size, which is
11). All six axes run lateral to the incisor, a feature thatischarac- somewhat smaller than the other fossil porcupines from
teristic of Coendou. Our findings contrast with those of Morgan Florida. The fossils from El Golfo described above are the
and White (1995) that the axes of the Feisey 3A cheek-tooth same size as C. kleini. However, because several hundred
rows run medial to the incisor. We found that, using our method thousand years and two thousand miles separate the two
ofanalysis (see Appendix 2), UF 124632 has an axis that is direc- populations, the strength of the relationship between the two
ted laterally (Fig. 11); in UF 135669, the incisor alveolus and the groups can be questioned. Still, the existence of two separate
alveolusofp4are both broken, makinga measurementunreliable. populations of smaller fossil porcupines at least suggests that
Six measurements of incisor angle of procumbency (from four C. kleini from Florida and Coendou cf. C. kleini from El
fossils, representing three sites) all fall in the range of Coendou, Golfo may represent distinct South American dispersals into the
aregreaterthanthe rangeofErethizon,and all butonearegreater North America.
than the mean for Coendou (Figs. 2F, 2G, 12).
The sizes ofthe p4’s and molarsintheFlorida fossils, as judged Western North America
by the product of length times width, all fall within or slightly Aside from the fossils from El Golfo, we examined fossils from
above therangeformodernErethizon,withthenotableexception faunas in the western United States: Grand View from Jackass
ofE. kleini. Three dentaries ofE. kleiniand their individual teeth Butte, Idaho (ca. 2.0-2.3 Ma) (Wilson, 1935; Shotwell, 1970;
have measurements close or equal to those of the fossils from El Repenning et al., 1995; Bell et al., 2004), and Vallecito Creek
Golfo (see above) and are intermediate betweenmodern Coendou andEl Casco,California (Table4). Work by F. K. Murray (perso-
andErethizon. Thisintermediatesizewastheprimarydistinguish- nal communication, 2011) restricted all of the Vallecito Creek
ingfeature used by Frazier (1981) todesignatethem as a newspe- erethizontid fossils to the C2r.ln geomagnetic chron (1.9-2.
cies (Fig. 2E). Ma). Thefossils from El Casco havea similarage, withtheexcep-
A previously undescribed specimen ofE. poyeri from Haile 7G tionofa single broken toothfrom an adjacent site (the SanTimo-
was preliminarily reported by Hastings et al. (2006). It includes teo Badlands) that may, along with a tooth from Wolf Ranch in
eleven caudal vertebrae, some ofwhich were noted to have bifur- Arizona (Harrison, 1978; Findsayetal., 1990), beamongtheold-
cated transverse processes (“dual transverse process sets”) and est of the erethizontids in North America at 2.5+ Ma (Albright,
from those vertebrae the investigators estimated the original 1999; Bell et ah, 2004).
length of the tail at “26-32 caudal vertebrae.” In addition, eight Our measurements indicate that the lengths offour cheek-tooth
other skeletal traits “are preserved well enough in this new speci- rows(twofromIdahoandtwofromCalifornia)equalorareslightly
men for study and all plot within the range of Erethizon." While largerthanthelengthsofmodernErethizon. Onlytwop4/ml ratios
not explicitly stated, these traits presumably relate to the size of could be determined, both on the fossils from Idaho. One (USNM
Contributions in Science, Number 524 Sussman et al.: North American Erethizontidae 7
13684) isquitelargebutnotbeyond therangeofmodern Coendow, the east coast of North America from which fossil porcupines
the other falls into the range ofoverlap between the two genera. are reported.
Three incisors from Idaho havecross-sectional ratios of 1.0 and The erethizontids from Cumberland Cave ascribed by White
1.1; one of these is an adult (USNM 13684), one a juvenile (UO (1970) to an evolutionary position intermediate between the
F-16272), and the third (UO F-16271) is a young adult. Three immigrant Coendott and modern Erethizon were assigned un-
fossils from El Casco and Vallecito Creek have ratios of 1.0, a equivocally by Frazier (1981) to Erethizon, as he did with all the
fourth is 1.1, but the ontogenetic ages of the animals cannot be fossils from North America. According to Gidley and Gazin
determined. Although none of these incisors have a ratio in the (1938), the faunal assemblage includes taxa associated with both
range of Coendon, the inability to determine the ontogenetic colder and warmer environments, so not all taxa may have been
age in the majority of them prevents a definitive assignment to contemporaneous. But it is also possible that the assemblage indi-
Erethizon. cates a nonanalog fauna (Semken et al., 2010) rather than a time-
Three cheek-tooth axes are all directed laterally, which is averaged sample resulting from the mixing oftaxa from different
uninformative. times. Our examination of the porcupines from Cumberland
UO F-16271 from Jackass Butte, Idaho, has a lingual angle Cave (Table 5) supports White’s (1970, p. 13) conclusions that
of incisor procumbency of 132 degrees, a trait of Erethizon the population is morphologically intermediate between Coendott
that is well outside the range of modern Coendott (Fig. 12). and Erethizon, which better fits with the interpretation ofa non-
Unfortunately, it is the only fossil in which the angle is analog fauna.
measurable. The cheek-tooth alveolar lengths are all the size of modern
A fossil from Vallecito Creek, ABDSP (LACM) 1563A^6136 Erethizon (n=8), with one exception: USNM V 25689 is the size
(LACM 6136 in Frazier, 1981) has a number ofcaudal vertebrae ofa large modern Coendott.
associated with it.Jefferson and Murray (G.T.Jefferson, personal All five ofthe p4/m1 ratios are in the range ofoverlap.
communication, 2010) determined that there are 16 vertebrae, Of four incisors associated with p4’s, two have a shape as is
rather than the twelve noted by White (1970). Our examination found in modern Erethizon and two are elongated as in Coendott.
ofthese vertebrae showed that, although the transverse processes Five incisorsassociated with dp4’soran unerupted p4 all havethe
are broken on all of the vertebrae, enough of their bases remain expected square shape ofa juvenile porcupine.
to show the presence of foramina in five of them similar to those Eight cheek-tooth axes relative to the incisors are measurable.
found in modern Coendoti but not in modern Erethizon. It is Seven are directed laterally and one (USNM V 7671, a juvenile)
not possible to tell whether any of the transverse p—rocesses—were medially.
fully bifurcated. It isdifficultto estimate how many ifany cau- Eive individual animals are measureable for angles of procum-
dalsaremissing. Basedonwhatis preserved,thenumberofcaudal bency. Ofthree buccal angles, one (USNM V 8130) falls into the
vertebrae indicates a tail length at the upper end of the range of rangeknownonlyfor Coendottandtwoareinthearea ofoverlap.
Erethizon. The presence of the foramina in the transverse pro- Of four lingual angles, one (USNM V 8130) has a value as in
cesses, on the other hand, suggests Coendoti. Coendott, one is in the area of overlap, and two (USNM V 7670
Thus,thefossil porcupinesfromwesternNorthAmericanhave and V 25689) are in the range for Erethizon.
few traits that permit a confident assignment to genus. The ages To summarize, ofthe twelve dentaries from Cumberland Cave,
of the northern (Idaho) and southern (Vallecito Creek and El sixhavesingletraitsthataredistinctive as togenus in modern ani-
Casco) fossils are similar and are somewhat younger than the mals. Two adults (USNM V 7672 and V 8128) have incisors like
fossils from the San Timoteo Badlands and Arizona. It seems Erethizon-, one adult (USNM V 25691) has an incisor as in Coen-
plausible to state that the fossils from Idaho, because of their dow,onejuvenile (USNMV7670) hasanangleofincisorprocum-
northern latitude, suggestthata substantial evolutionaryprocess bency typical ofErethizon and one juvenile (USNM V 8130) has
had already occurred to allow survival during seasonal climate an angle typical of Coendott. USNM V 7671, a juvenile, has a
changes which included significant cooling not experienced by cheek-tooth axis medial to the incisor. One adult dentary
their Neotropical ancestors (Graham, 1999). Physical evidence (USNM V 25689) has three distinctive traits: The length of its
to supportthatinterpretation, however, is limited to a single fos- cheek-tooth row is as in modern Coendott, and its incisor is
sil with an incisor procumbency as in modern Erethizon (noting shaped as in Coendott, but it has an angle ofincisor procumbency
alsothatthe moresoutherlyFlorida fossilsall haveprocumbency as found in modern Erethizon.
measurements in the range of modern Coendott). Square cross- Explainingthe mixoftraits inthese fossilsseems to involvethree
sectional shapes ofseveral incisors, both in Idaho and in Califor- possibilities. Eirst,as Gidleyand Gazin (1938) proposed,thefossils
nia,add someweighttotheevidencein supportofErethizon. On may represent different assemblages of animals from different
the other hand, the foramina in the transverse processes of the times. Second, porcupines from the north and porcupines from
caudal vertebrae look like Coendott. Nevertheless, based on the the south intermingled at Cumberland Cave. Third, the fossils
scenario described below, we retain Frazier’s (1981) assignment represent an intermediate stage of evolution in which Neotrop-
of the genus Erethizon to the Pliocene-Pleistocene fossils of the ical traitsandcold-adaptivetraits hada moreevenlyexpressed pre-
western United States, with the exception ofthe El Golfo fossils sence in porcupine populations than that which is seen in
that we assign to Coendott. modern Erethizon. Based on the absence in the fossils from
Florida oftraits found in Erethizon and on the scenario presented
Cumberland Cave in the Discussion, where we suggest a southward migration
As with most of the North American fossil sites in which porcu- of cold-adapted porcupines along the Appalachian Mountain
pines are found, determination of the age of the Cumberland corridor, the third alternative appearsto moreclosely fittheadmit-
Cave fossils is difficult and based only on biochronologic data. tedlysparse data andsoweretaintheassignment byFrazier (1981)
Agenerally recognized estimatesuggestsanage rangeofthe fauna ofthe fossil porcupines from Cumberland Cave to Erethizon.
to be between 0.5 and 0.9 Ma (Bell et al., 2004). Cumberland
Cave in Maryland and Port Kennedy Cave in Pennsylvania (with Aguascalientes, Mexico
two isolated teeth) are about 250 miles in latitude south of the A single dentary (UMMP V-47106) recovered from the Cedazo
Idaho Grand View fauna but are the northernmost localities on Formation (Hibbard and Mooser, 1963) is intriguingly situated in
8 Contributions in Science, Number 524 Sussman et al.: North American Erethizontidae
central Mexico just north of modern Coendoit populations and LOCALITIES AND MATERIAL EXAMINED. Inglis lA,
southoftherangeofmodernErethizon(Fig. 1). Datingofthemate- Elorida: UE 21473 (holotype), UE 21474, UE 21475.
raigaelibseptrwoebleenma1t.i0c,anwdith1.t8heMlaa.tesTtheestfimaautneabwyaBseltlheotuagl.ht(2b0y04F)roafziaenr Coendon cf. C. kleini
(1981) to be Rancholabrean. Our analysis shows the cheek-tooth LOCALITIES AND MATERIAL EXAMINED. El Golfo de
row is slightly longer than the longest modern Erethizon; the p4/ Santa Clara, Sonora, Mexico: AWC 10858, AWC 12197, AWC
ml ratio is in the area of overlap between modern Erethizon and 12540, AWC 13592, AWC 14810, IGM 10199.
Coendon; the incisor shape more closely fits Coendon but is at
the top of the range of Erethizon; the cheek-tooth axis is directed Coendon spp.
lateral to the incisor; and the angle of incisor procumbency falls ErethizondorsatnmErazier, 1981:44,figs. 5-11, 17;Morganand
well within the range of Coendon, at the very top ofthe range for White, 1995:421, fig. 5.
EbryeWthhiiztoen((1T9a6b8l)ea4)n.dTthoetfhoessgielnwuassEarsestihginzeodntboytFhreagzieenrus(1C9o81e)n.don LOCALITIES AND MATERIAL EXAMINED. Haile 16A,
Although diagnostic features that would permit definitive Elorida: UE 21490, UE 21492. Leisey 3A, Elorida: UE 124632,
assignment of this fossil to either Coendon or Erethizon are UF 13566U9M.MCPoleman 2A, Florida: UF 11776. Aguascalientes,
lacking, wetentativelyassign ittothegenus Coendon onthe basis Mexico: V-47106.
of the shape of its incisor, the direction of the cheek-tooth axis, Erethizon Cuvier 1822
and the angle of incisor procumbency, all of which align more
Erethizon bathygnathnrn (Wilson, 1935)
closely to Coendon. In addition, the location of the fossil
near the northern extent of modern Coendon and at a much E. bathygnathnrn Wilson 1935:220.
greater distance south of the known range of modern Erethizon Coendon stirtoniWhite 1968:2, figs. 1-3.
is a secondary consideration that also supports the assignment E. bathygnathnrn Shotwell 1970:12, 15-16, 71-72, fig. 34.
to Coendon. C. bathygnathnrn White 1970:7 {bathygnathnrn apparently mis-
spelled brachygnathnm by White).
Fauna ofthe Rancholabrean NALMA E. bathygnathnrn Frazier 1981:40, figs 8-11, 14, 16-19.
Erethizontid fossil dentaries associated with the fauna ofthe Ran- LOCALITIES AND MATERIAL EXAMINED. Jackass Butte
cholabrean NALMA include those from Shelter Cave, New Mex- (Grandview fauna), Idaho: USNM 13684 (holotype), UO E-
ico (fossil age as in Thompson et al., 1980) discussed above; a 16271, UO E-16272; Vallecito Creek, California: IVCM 309,
single dentary of a very young animal from San Josecito Cave, IVCM 460, ABDSP (LACM) 1563W6136, LACM 61420,
Nuevo Leon, Mexico (age as in Arroyo-Cabrales et ah, 1995), LACM 6210. Wolf Ranch, Arizona.
which has the Erethizon angle of incisor procumbency (buccal
126 degrees, lingual 129 degrees); and a dentary from Edisto Erethizon cascoensis (Erazier, 1981)
Beach, South Carolina, which we did not examine but which Coendon cascoensis White 1970:3, figs. 1-2.
appears in a published illustration (Sanders, 2002) to have the E. cascoensis Erazier 1981:42, figs. 5-7, 11.
large p4 characteristic of Erethizon. With the possible exception
of the Aguascalientes fossil, we are not aware of any published LOCALITIES AND MATERIALEXAMINED. El Casco, Cali-
mention of porcupines other than Erethizon being present in the fornia: E:AM 17883-1, E:AM 17883-2, F:AM 17883-4, E:AM
fauna of the Rancholabrean NALMA. We therefore accept the 17883-5, E:AM 17883-6.
assignment byNEAraLziMerA(1981) of porcupines in the fauna of the Erethizon dorsatnm (Cuvier, 1822)
Ranchlabrean to the genus Erethizon.
Hystrix dorsata Linnaeus 1758.
SYSTEMATIC PALEONTOLOGY E. dorsatnm Cuvier 1822:413-484.
E. cloacinns Cope 1871:73-102.
Based on the modern and fossil descriptions above and onthe fol- E. godfreyi Allen 1904:383-384.
lowing discussion, we propose this revision for the systematics of Coendon cnmberlandicns White 1970:7.
the erethizontids of North America. The generic names Hystrix, E. dorsatnm Erazier 1981:44, figs. 5-12, 14-19.
Cercolabes, Sphingnrns, Synoetheres, Synetheres, Coendn, Sphig-
LOCALITIES AND MATERIAL EXAMINED. Cumberland
gahneprrpnelsiu,enddatenordvtaEhrecihoguiesnnoNupesrootCcrotoeapnidcwoaenlr.epoarlcl,upaitnessopmeeciepsoianntdianretihneclpuadsetd, C78a61v72e08,,, UUMaSSrNNylMManVVd:7861U7310S,,NUUMSSNNVMM7V6V67886,1732U4,,SUUNSSMNNMVMVV767266957,638,9UU,SSUNNSMMNMVV
Order Rodentia Bowditch, 1821 V 25690, USNM V 25691; SanJosecito Cave, Nuevo Leon, Mex-
Suborder Hystricomorpha Brandt, 1855 ico: LACM 2968; Shelter Cave, New Mexico: LACM 1748,
LACM LACM LACM LACM
Eamily Erethizontidae Bonaparte, 1845 150691, 150692, 150693,
150694, LACM 150695, LACM 150696, LACM 150697,
Genus Coendon Lacepede, 1799 LACM uncatalogued; Port Kennedy Cave, Pennsylvania; Conard
Coendon poyeri (Hulbert, 1997)
Eissure, Arkansas; Trout Cave, West Virginia; Apollo Beach, Elor-
Erethizon poyeri Hulbert, 1997:624, fig.l. ida;PortCharlotte,Elorida;additionally, erethizontidsofall North
LOCALITIES AND MATERIAL EXAMINED. Haile 7C, cAamleirenitceasnfolsosciall,itaireesroeftaRiannecdhionltahberetaanxofnauEnrae,theixzcoenptdionrgsatthenmA.guas-
Elorida: UE 121740 (holotype), UE 121747 (measurements by
Hulbert, 1997); Haile 7G. DISCUSSION
Coendon klemi (Erazier, 1981) new combination
Hibbard and Mooser (1963), examining porcupine dentition,
Erethizon klemi Erazier, 1981:43, figs. 8-11, 14-19. observed that Erethizon dorsatnm “is probably one of the most
Contributions in Science, Number S24 Sussman et al.: North American Erethizontidae 9
variable rodents in North America.” Our studies support that morphological evolution of features of the skeleton that define
observation and extend it to other mandibular characteristics as Erethizon occurred in North America.
well (e.g., length ofdiastema,superior-inferiordepthofmandible, Once the isthmus had formed, erethizontids were able to begin
and the shapes ofthe ascending ramus and angular process). The moving northward into North America. With the large gap in
Neotropical porcupines are similarly variable. As noted by Voss the fossil record, the exact time of the initial and possible subse-
et al. (2013:28) with regard to modern Coendou, “most cranio- quent dispersal episodes cannot be known, butatsome pointdur-
denta! characters known to vary among Recent erethizontids are ing the move north, possibly in central or northern Mexico, a
either autapomorphies ..., or they are so variable within species single migratory pathway from the south split into two pathways,
as to be effectively useless for phylogenetic analysis.” Many of one following the Gulfof Mexico and terminating in Florida, the
the same variable traits appear in both Erethizon and Coendou. othercontinuing north into what is now California and the north-
This parallel variability and the accompanying close anatomical western United States and eventually even farther north into
similarities of Coendou and Erethizon demonstrate the close kin- Canada. At a relatively early time, the western pathway lost con-
ship ofthe two taxa but also create difficulties in identifying ana- tact with the stem and eastern pathways. Evolutionary changes
tomical features that can reliably distinguish them. Some of the occurred in the western animals that allowed them to withstand
traits we identified, such as the differing relative sizes ofp4 versus and even thrive in the increasingly seasonally cold environments.
ml and the differing cross-sectional shapes ofthe incisor, are dis- Asthewesterngroupofporcupinesevolvedthissubstantial ability
tinctive in extant populations but only in their more extreme to survive what became Ice Age conditions, they spread over the
values, with their variant morphologies possibly demonstrating northern latitudesofNorthAmerica, movingeastaswell asnorth.
phenotypic plasticity that has accumulated over evolutionary At the eastern extent oftheir movement, the Appalachian Moun-
time. More complex changes, as in the shape of the mandible to tains provided a pathway to move south. The Cumberland Cave
accommodatethebitingofbark,may reflecttheinfluenceofdirect fossils,withtheirmixoftraits,may providea snapshotoftheevo-
evolutionary change in the immigrant porcupines in response to a lutionary transition between the original immigrants and today’s
more stronglyseasonal environment with the resultant changes in Erethizon.
food supply and so might not be expected to be seen in the Neo- The porcupines in the Gulf of Mexico migratory branch may
tropical porcupines. have thrived for as long as a million years. Based on the age of
Due to the extensive variability present in these animals, we the porcupines from El Golfo assigned to Coendou (ca. 1 Ma)
have found thatusingmorphologic differences in modern animals and the estimated age of the fossils from Cumberland Cave
toidentifygenera offossil animalspresentssignificantpossibilities assigned to Erethizon (0.5-0.9 Ma), we suggest that at about
for error. The variability means that a single trait in a single fossil 1 Ma, for reasons possibly related to the effects of Ice Age con-
often cannot be used to identify a porcupine beyond Erethizonti- ditions, the connection between the southeastern porcupines
dae, and, because the number of fossils are sparse in individual and their souNthoewrn subtropical relatives became attenuated and
localities and the fossil sites are separated by long distances in then severed. isolated, the Florida porcupines did not evolve
space and in time, any attempt to identify genera and species of traits that allowed them to continue and eventually became
extinct.
the fossils and assemble a reasonable narrative of their history
inevitably leadstospeculation. Nevertheless,wecanonlyevaluate SUMMARY
the fossil material that is available to us and base our conclusions
on that information. A morphological study of modern Neotropical {Coendou spp.)
With these caveats and with the acknowledgement that future and North American (Erethizon dorsatum) erethizontid dentaries
fossil finds may alter our conclusions, we posit that there are rea- and caudal vertebrae has found physical differences that distin-
sonable alternatives to the presently accepted scenario for North guish the two genera. Application of these findings to the fossil
AmeWreicdainsagproerecuwpiitnhesF.razier’s statement (1981:47) that“The fossil pLoargcouapiSnaenstafirnomBraSzhielltseurppCoarvtes oinurNcoorntthenAtmieornitchaataandgetnhuossecafnrnoomt
recordshowsno majorstructuralchangesfrom thethreeearlyfos- be identified based solely on size. Consequently, we propose the
sil forms to the living species.” The mandibular differences we following taxonomic revision of North American erethizontids.
describe above are significant and reflect in modern Erethizon an All fossils from Florida that are older than the Rancholabrean
evolutionary response to the new environment the immigrants North American LMA plus a single fossil from Aguascalientes,
had entered. There is no indication of these changes in the early Mexico, are reassigned from Erethizon to Coendou. In addition,
porcupines from Florida, despite a geological record covering erethizontidfossils fromEl GolfodeSanta Clara,Sonora, Mexico,
about 1 Ma. The first fossil record in eastern North America of described in this paper, are assigned to Coendou. The remaining
Erethizon-like mandibularchanges that we found occurs at Cum- North American erethizontid fossils are retained in Erethizon, as
berland Cave in Maryland, whose fossils are ofan uncertain age in Frazier (1981).
but are probably less than 1 Ma. We present a theoretical migratory pathway into North Amer-
We propose that, if the closure of the Isthmus of Panama did ica from tropical America for the erethizontids that dispersed via
take place over a protracted period oftime, beginning in the mid- the Panamanian land bridge (erethizontids that we consider mor-
dle Miocene or earlier (Bacon et al., 2015; Montes et ah, 2015), phologically to have been Coendou). At some point in central to
the tectonic events occurring then may have provided the extant northern Mexico, a single northerly pathway divided into two,
species multiple opportunities for vicariant episodes. During that with the western branch continuing north into northwestern
time, it appears that the Neotropical and North American erethi- North America before then turning east at higher latitudes. This
zontid lineages did begin to diverge, according to the research of branch adapted to the cold-weather conditions it encountered
Vilela et al. (2009) and Voss et al. (2013). Lacking fossils from and evolved into a new genus: Erethizon. The eastern branch of
that extended period of time, we can only state that at present the Mexican population dispersed east and followed the southern
there are no fossils referable to Erethizon in either South or coast of North America into Florida. These Neotropical porcu-
Central America, with the entire fossil record of the genus being pines retained the traits of their immigrant ancestors and ulti-
confined to North America. It appears that at least the mately became extinct.
10 Contributions in Science, Number 524 Sussman et al.: North American Erethizontidae
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ymous, Chris Bell, and the journal in-house reviewer, whose combined catalogues based onsubfossil and recent material collected by
advice hasledto a higher-qualitypaper. Also, aspecialthanks toDolores Professor Peter Wilhelm Lund and Professor Johannes Theodor
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