Desmostylian Remains from Unalaska Island, Aleutian Chain, Alaska

BULLETIN

of CARNEGIE MUSEUM OF NATURAL HISTORY

MAMMALIAN PALEONTOLOGY ON A GLOBAL STAGE:

PAPERS IN HONOR OF MARY R. DAWSON

Edited by

K. CHRISTOPHER BEARD and ZHE-XI LUO

NUMBER 39 PITTSBURGH, PENNSYLVANIA, USA 2007

BULLETIN OF CARNEGIE MUSEUM OF NATURAL HISTORY

Number 39, pages 1–234, 94 figures, 20 tables, 3 appendices

Issued 18 December 2007

Zhe-Xi Luo and David A. Smith, Interim Co-Directors

Editorial Board: David S Berman, Zhe-Xi Luo, Sandra L. Olsen, John E. Rawlins, and John R. Wible

Managing Editor: Tamara Moore

Cover illustration: Artist’s depiction of the living Laotian rodent Laonastes aenigmamus standing upon lacustrine strata containing awell-preserved skeleton of the early Miocene rodent Diatomys shantungensis. Mary Dawson and her colleagues were the first to recognizethat Laonastes is a surviving member of the otherwise extinct rodent clade Diatomyidae (see contribution by Flynn in this volume).Original art of Mark A. Klingler.

Frontispiece: Portrait of Mary R. Dawson painted by Gina Scanlon.

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© 2007 by Carnegie Institute, all rights reserved.

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CARNEGIE MUSEUM OF NATURAL HISTORY4400 Forbes AvenuePittsburgh PA 15213-4080USA

DESMOSTYLIAN REMAINS FROM UNALASKA ISLAND, ALEUTIAN CHAIN, ALASKA

LOUIS L. JACOBSDepartment of Geological Sciences, Southern Methodist University, Dallas, TX 75275 ([email protected])

ANTHONY R. FIORILLOMuseum of Nature and Science, P.O. Box 151469, Dallas, TX 75315 ([email protected])

ROLAND GANGLOFFMuseum of Paleontology, University of California, Berkeley, CA 94720 ([email protected])

ANNE PASCHDepartment of Geology, University of Alaska, Anchorage, AK 99508 ([email protected])

ABSTRACT

At least four individuals of desmostylian are described from a single locality on Unalaska Island, Alaska. Desmostylians are known only from theNorth Pacific region from Japan to Mexico, but this form is currently unique to Unalaska. It retains certain primitive features, such as relativelylow-crowned columnar (desmostylodont) cusps with remnants of cingula, that are shared with Cornwallius. However, it is derived in havingadditional cusps on lower molars. It also has well-developed upper and lower tusks and a narrow mental symphysis, so far as can be determined.The age of the desmostylian sample is either late Oligocene or (more likely) earliest Miocene. Although the representation of skeletal elements ofindividuals is low, the presence of a neonate dentary implies that a breeding population of this taxon inhabited, rather than simply dispersed through,the Aleutian Chain during the mid-Cenozoic.

INTRODUCTION

The first published report of desmostylian fossils from Un-alaska in the Aleutian Islands is that of Byers (1959), whostated that teeth from Unalaska “were identified by G.E.Lewis (written communication, 1954) as those of Cornwal-lius sp., a marine mammal of early Miocene age.” Since thattime, no definitive study of the Unalaska material has beenpublished, although Beatty (2006) describes a cast of theoriginal desmostylian tooth from Unalaska, which he refersto Cornwallius sookensis. Moreover, although quite goodmaterial referred to Cornwallius sookensis is known fromthe upper Oligocene Yaquina Formation of Oregon (Rein-hart 1982), it remains unclear how the morphology of theUnalaska material corresponds with that of the type and re-ferred specimens.

Our objective in this study is to describe additional des-mostylian material from Unalaska. First we trace the prov-enance of desmostylian material from Unalaska as fully aspossible to clarify the geologic occurrence of all the speci-mens. After describing the Unalaska fossils, we presentcomments on the genus Cornwallius as a basis for the com-parisons that follow. We conclude with a consideration ofthe age of the fossiliferous deposits and a discussion of theoccurrence of the fossils and its meaning.

LOCALITIES AND SPECIMENS

History of the Collection

In 1953 and 1954, bones and teeth were found by geologistsmapping for the United States Geological Survey (USGS)on Unalaska (Fig. 1A), an island in the eastern AleutianChain (53° 54� North, 166° 32� West), approximately 1500km southwest of Anchorage. All the bones and teeth wereconsidered to be referable, probably, to a single individual.

One cheek tooth was identified by G.E. Lewis as desmo-stylian, more specifically Cornwallius or possibly Desmo-stylus, according to published literature, and used byDrewes et al. (1961) to assign a lower Miocene age to thesedimentary unit within the Unalaska Formation that pro-duced the bones. The Unalaska desmostylian has been men-tioned several times in passing (e.g., Byers 1959; MacNeilet al. 1961; Mitchell and Repenning 1963; Lankford andHill 1979).

Reinhart (1976, p. 284) reported that, “together with theCornwallius tooth reported by Drewes, other very fragmen-tary teeth and skeletal material from the same location atUnalaska are housed at the National Museum of NaturalHistory” (USNM). He further stated that, even if prepared,it was unlikely that the material in the USNM would add tothe knowledge of Cornwallius. No specimens from Un-alaska, including the tooth purported by Reinhart to be inthe USNM, have been adequately described or illustratedpreviously, although Beatty (2006) describes and illustratesa cast of the original cheek tooth (as we have done below).However, more specimens from Unalaska are known, col-lected after the USGS mapping effort was completed.Therefore, it is worthwhile to establish the provenance of allthe specimens that were examined for this study in order toinfer how they might relate to each other.

USGS documents in Denver show that fossils were col-lected from Unalaska Island by G.D. Fraser and G.L.Snyder in 1953 and 1954, corresponding to the dates inwhich USGS field parties mapped the island (Drewes et al.1961). Fraser was the leader of the USGS field mappingparties during those years and the notebooks for those datesare given as reference on a USGS specimen card for speci-men No. D848. Fraser is third author and Snyder is secondauthor on USGS Bulletin 1028-S, Geology of Unalaska Is-

189

Fig. 1.—Location map of Unalaska Island: (A) elementary school (below people) in the Arriaga Quarry site and USGS desmostylian locality withUnalaska Lake in the background (fossil locality according to James Dickson, on the right, longtime Unalaska resident who worked in the ArriagaQuarry); (B) USNM topographic map record of the USGS desmostylian locality; (C) location of Unalaska Island in the Aleutian Chain.

190 BULLETIN CARNEGIE MUSEUM OF NATURAL HISTORY NO. 39

land and Adjacent Insular Shelf, Aleutian Islands, Alaska(Drewes et al. 1961).

The material from Unalaska was received by G.E.Lewis, paleontologist for the USGS, in shipment GG-54-13D (a designation which is also listed as the “E&R No.”)on October 5, 1954, and identified by him on October 24,1954. USGS locality data read: Unalaska Fm., road andbuilding cuts immediately E. of Unalaska Lake, 1 mi. S.E.of Unalaska village, Dutch Harbor, Unalaska Island. Ac-cording to Lewis’ report, the most significant specimen wasa cheek tooth fragment with the designation 54-Sn-2. A castof that tooth is catalogued as D848 in the USGS collection,Denver. A note on the specimen card states that the originalis in the USNM. Lewis identified the tooth as Cornwalliusin his internal report, but in Drewes et al. (1961) the iden-tification is more equivocal with the addition of “identifi-cation as Desmostylus is possible” (Drewes et al. 1961, p.606). Two letters at the USGS in Denver, one from Rem-ington Kellogg to G.E. Lewis (and annotated by Lewis),dated July 18, 1957, and the other from Charles A. Repen-ning to G.E. Lewis, leave no doubt that both Lewis and Re-penning considered the tooth to be that of Cornwallius andthat it was at the USNM.

An accession memorandum at the USNM signed by C.L.Gazin on September 4, 1958, indicates transmittal of “29fossil sirenian bones (desmostylid) collected by G.L.Snyder and G.D. Fraser from Unalaska Island, Aleutian Is-lands, Alaska” from the USGS to the USNM. The USNMaccession number is 214716. The transmission of the speci-mens is recorded in a letter dated May 13, 1957, from C.W.Merriam of the USGS to Remington Kellogg of the USNM,which confirms that the collection was part of a shipmentassigned the USGS number GG-54-13D. The transmittalwas formalized in a letter dated November 6, 1957, fromR.H. Lyddan, Acting Director of the USGS, to LeonardCarmichael, Secretary of the Smithsonian Institution,which indicates that the transfer of specimens to the USNMhad occurred on April 24, 1957.

Included in the USNM records is a specimen list and atopographic map (Corps of Engineers, U.S. Army TacticalMap, Unalga Island Sheet [Unalaska Island] Alaska N 53°45�, W 166° 00�, 15 × 40; fide Beatty 2006; Fig. 1B) show-ing the location on Unalaska Island where the collectionwas made. The cheek tooth identified by G.E. Lewis andreported to be in the USNM has not been located. However,in addition to the cast of the specimen at the USGS (D848),a cast is also in the USNM collections along with a letterdated November 15, 1962, from George L. Snyder to RoyReinhart, in which Snyder encourages Reinhart to study thetooth.

A memorandum on file with the USGS in Reston, Vir-ginia (located by Robert Blodgett), from USGS paleontolo-gist Charles A. Repenning to George Plafker of the USGSAlaska Geology Branch, dated November 29, 1965, identi-fied two specimens as “probably Desmostylus.” The text ofthe memorandum indicates that USGS geologist DonMiller sent the collection to Remington Kellogg and that the

general area of the collection was Yakataga District; how-ever, the locality designations of the desmostylian speci-mens are given as 54-Sn-65A and 54-Sn-217. Those num-bers correspond to field numbers assigned to Unalaska Is-land fossils by Snyder and Fraser as demonstrated by labelspacked with the specimens. The last digits of the field num-ber provide the numerical sequence in the specimen list ac-companying the transfer of specimens from the USGS tothe USNM.

Most specimens in the shipment are fragmentary, in-complete, unidentifiable, and encased in dense matrix. Asstated above, the field number of the tooth originally iden-tified by Lewis is 54-Sn-2 according to USGS records. TheUSNM specimen list accompanying accession 214716 in-dicates that specimen 2 is a “cheek tooth in ss.” This seemsto represent clearly the tooth identified as Cornwallius orpossibly Desmostylus in Drewes et al. (1961). Specimen65A in the list, corresponding to 54-Sn-65A mentioned byRepenning, is the “largest chunk of rock with main portionof tusk” in a set of chunks and fragments under number 65.Repenning’s listing of locality 54-Sn-217 corresponds to217 in the list, “two large chunks containing casts of twotusks in place in a fragment of jawbone.” That specimen isnow cataloged into the USNM collections as 529235. Theonly other specimen that has been catalogued is a fragmen-tary tooth, USNM 529234 (= 54-Sn-59B), part of which isslated for isotopic analysis.

The locality data reported by Drewes et al. (1961, p. 606)for the site is “road and building cuts immediately east ofUnalaska Lake, 1 mile from the dock area in the village.” Anotation on the topographic map on file at the USNM states,“shore of Unalaska Lake 1/2 mile from Unalaska Village.”

No more desmostylians came to light, apparently, until1992, when Betty and Frank Arriaga, owners of a rockquarry in the village of Unalaska, retrieved a number ofbone fragments exposed during quarry operations. Theirquarry is the same or a continuation of the earlier quarriesthat yielded bones collected by the USGS, so far as can bedetermined (James Dickson, Unalaska resident, personalcommunication). Quarrying has long since halted and anelementary school now stands in the remnants of the oldquarry (Fig. 1A).

The Arriagas contacted Anne Pasch of the University ofAlaska, Anchorage, who enlisted Roland Gangloff of theUniversity of Alaska, Fairbanks, to help investigate the thennewly discovered specimens. The two of them flew toDutch Harbor, the population center of the island, wherethey evaluated the fossil material for two days. Some of thatmaterial was taken to the University of Alaska collection. In2004, Fiorillo, Jacobs, and David Norton visited Unalaskaand found material from the Arriaga Quarry on display atthe headquarters of the Ounalaska Corporation in DutchHarbor. These specimens were made available to usthrough the cooperation of the Ounalaska Corporation andthe Museum of the Aleutians. Jacobs made a short returnvisit to Unalaska Island in 2005.

Although we are aware that some specimens may yet be

2007 JACOBS ET AL.—UNALASKA DESMOSTYLIAN 191

in private hands, we have examined all specimens fromUnalaska Island of which we know that are accessiblethrough the USNM, the University of Alaska, and the Mu-seum of the Aleutians. The specimens from the Universityof Alaska and from the Museum of the Aleutians were takento the Museum of Nature and Science (formerly the DallasMuseum of Natural History) and Southern MethodistUniversity for preparation and study. All the specimensfrom Unalaska Island are fragmentary. The rock matrixis hard and the bone is soft and brittle. The fossils werefound in the course of commercial quarrying. Conse-quently, there are many fragmentary and uninformativespecimens. We have not described them here. Some goodspecimens are preserved as the matrix mold of bones. Peelsand casts of the natural molds were made to facilitate theirinterpretation.

Geological Setting

Unalaska Island is approximately 62 km by 137 km, thesecond largest island in the Aleutian Archipelago. Its rug-ged terrain is dominated by Makushin volcano, an andesiticand basaltic stratocone that rises to an elevation of 2037 m(Miller 1994). The oldest and most widely exposed rockunit on the island is a thick and complex sequence of sedi-mentary, pyroclastic, extrusive, and intrusive rocks termedthe Unalaska Formation (Drewes et al. 1961). The fossillocality falls within this formation.

The fossiliferous sedimentary sequence of the UnalaskaFormation was mapped in greater detail by Lankford andHill (1979). They named the Dutch Harbor Member andmeasured a section with a maximum thickness of 126 mlying between upper and lower igneous complexes. To-gether these three units (i.e., lower igneous complex, DutchHarbor Member, upper igneous complex) comprise theUnalaska Formation, which is exposed over 70% of the is-land and is 900 to 16,700 m in total thickness as estimatedfrom topographic relief and regional dip (Drewes et al.1961). The Dutch Harbor Member is truncated by the Cap-tains Pluton to the southeast, which is most likely the sourceof numerous dikes and sills cutting across the fossil bearingunit. A potassium-argon date of 13 Ma (middle Miocene)was obtained from this pluton (Lankford and Hill 1979).The upper contact of the Unalaska Formation is a deeplyincised surface buried by late Pleistocene Makushin volca-nics (Drewes et al. 1961).

The Dutch Harbor Member is exposed on the north sideof the island near the village of Unalaska, which is southeastand adjacent to Dutch Harbor. It is composed mainly ofsandstones and conglomerates that have been thermally al-tered to greenschist facies (Lankford and Hill 1979). Todate, fossils have only been reported from the northern sec-tion in the vicinity of Unalaska village (Drewes et al. 1961;Lankford and Hill 1979). The lower portion of the DutchHarbor Member is dominated by fine-grained sandstonescontaining worm tubes, bivalve burrows, and the bivalvesChlamys and Pododesmus (Lankford and Hill 1979).Drewes et al. (1961) report the bivalve Mya found with the

desmostylian material. The upper portion of the Dutch Har-bor Member is characterized by coarser sandstones andconglomerates. It contained a single vertebra and one bar-nacle as shown in the measured section of Lankford andHill (1979).

Commercial excavation in the Arriaga Quarry providedexcellent exposures of the Dutch Harbor Member. The sedi-ments there are light green, poorly bedded and poorlysorted, highly indurated, fine to coarse sandstones and con-glomerates. They contain angular clasts and bone fragments2–37 cm or more in longest dimension. These features aresimilar to those published for the upper 25 m of the mea-sured Dutch Harbor Member section, but beds were nottraced to the type section (which is less than one km away).The quarry face is cut by an igneous dike that most likelyoriginated from the Captains Pluton and by numerous faultsand joints.

The presence of bivalves of the genus Mya (see below)indicate a shallow coldwater environment (Drewes et al.1961), which is consistent with the presence of barnacles.The skeletal fragments seen in the Arriaga Quarry wereseparated by several meters and encased in the highly indu-rated matrix. The scattered and fragmentary nature of thebones suggests that the skeletal remains were disarticulatedand transported, or that more than one animal was presentbefore burial. The bones exhibit fresh breaks, and the speci-mens are not abraded or rounded. The nature of the channeldeposits (graded bedding, load structures, cross-stratifica-tion, and diamictic texture) suggested to Lankford and Hill(1979) that these represent rapid deposition by currents inproximal turbidite flows and debris flows. These occurredalong the edge of a rapidly filling submarine basin on thesummit of the Aleutian Ridge, adjacent to the submarineflanks of a Tertiary volcano (Lankford and Hill 1979). Themodel for summit basins on the Aleutian crest was origi-nally derived to explain extensional basins related to theyoungest phase of Aleutian evolution beginning at around 5Ma (Scholl et al. 1975; Vallier et al. 1994), although summitbasins may have been formed earlier as well.

Bones from Unalaska are usually surrounded by an ir-regular halo of iron oxides representing early precipitationrelated to pH or eH changes, probably associated with rot-ting organic matter. There is also evidence of later dissolu-tion of teeth as indicated by oxidation halos around toothstructures that are no longer present (Fig. 2). This is clearevidence that upper and lower teeth belonging to the indi-vidual represented in Figure 2 were in occlusion when bur-ied, and the upper teeth were subsequently dissolved away.

Oxygen isotope evidence indicates that low-grade meta-morphism was caused not by ridge subduction, but by nearsurface interaction of the Captains Pluton with meteoricwater (Perfit and Lawrence 1979), suggesting that uplift re-sulted from pluton implacement, bringing the Dutch HarborMember above sea level. Dissolution of teeth may havebeen a function of varying oxidation potential in meteoricground water accompanying low-grade regional metamor-phism associated with intrusion of the Captains Pluton.


Description of Fossil Specimens

Upper molar fragment (USNM 22066 = USGS D848;Fig. 3).—This is a cast of the original desmostylian speci-men identified from Unalaska Island. Because of its histori-cal significance, it is described first. Unfortunately theoriginal is missing, but it is represented by plaster casts atthe USGS (Fig. 3) and at the USNM, the latter of which wasthe subject of Beatty (2006). The posterior portion of thistooth is missing. Roots are not discernible. This tooth, likeother teeth from Unalaska, are desmostylodont in that allcusps on posterior cheek teeth are swollen, columnar, andappressed (fide Ray et al. 1994). Wear on the tooth columnsis primarily but not exclusively apical, producing thick cir-cular enamel rings with rounded rather than sharp edgessurrounding a dentine core. The walls of the columns areslightly rounded and swollen at the base, and the tooth isless hypsodont than Desmostylus. Those are primitive char-acters and probably the basis for the specimen originally

being referred to Cornwallius. It is considered an upper mo-lar by comparison with teeth of Desmostylus and Cornwal-lius sookensis, both of which have an anterior row of threecusps (a mesial talon with an accessory cusp flanking it oneach side), which is not present in lower molars.

Because of its relatively small size compared to the por-tion of a left upper molar described below, we do not con-sider USNM 22066 to be an M3. Beatty (2006) noted thatupper molars of Cornwallius have a straight lingual marginand a labial bulge formed by the paracone and accessorycusp. Those characters indicate that USNM 22066 is fromthe right side. The mesial talon contacts and separates theparacone anterolingually and the protocone anterobuccally.The metacone is smaller than either the paracone or the pro-tocone and sits at the posterolingual margin of the paracone.The hypocone and any additional posterior columns, if anywere originally present, are broken away in this specimen.

Other Unalaska upper cheek tooth fragments [Museumof the Aleutians (MOTA) 2004.009.07 and MOTA2004.009.01].—MOTA 2004.009, a multicusped and un-worn tooth (Fig. 4A) appears to be a deciduous premolarbecause its crown pattern is so distinct and unlike otherteeth. Ten cusps with two additional minor cuspules arepresent. The tooth has suffered some saw damage. It is con-sidered an upper tooth, possibly a fourth deciduous milkmolar (see Inuzuka et al. 1994), because of its round occlu-sal outline.

MOTA 2004.009.01 (Fig. 4B) is identified tentatively asthe posterior portion of a left M3, preserving a large lingualcolumn (protocone, fide Inuzuka et al. 1994) that is missing

Fig. 2.—Oxidation halo representing column of dissolved upper tooth im-posed in sediment on occlusal surface of lower tooth (MOTA2004.009.04) as seen during preparation. Compare with Figure 8, afterpreparation. The presence of the halo indicates that upper and lower jawswere in occlusion at burial but were subsequently subjected to significantdiagenetic alteration resulting in the dissolution of the upper teeth. Scalebar = 1 cm.

Fig. 3.—Cast (USGS D848 = USNM 22066) of original desmostylianright upper cheek tooth from Unalaska identified by G.E. Lewis as Corn-wallius. Anterior is to the top in this photograph of the occlusal surface.The anterior row of three cusps is comprised (from left to right) of thelabial accessory cusp, the mesial talon, and the lingual accessory cusp.These are followed by the paracone and protocone, in turn followed by themetacone. The hypocone or other columns that may have been present aremissing due to breakage. The anterior row of three cusps clearly indicatesthat this is an upper cheek tooth, probably M1 or M2. Scale bar = 1 cm.


its anterolabial rim, a slightly smaller posterior column (hy-pocone) with an oblique posterior wear facet, and a smallerposterobuccal metacone, anterior to which is the posteriorenamel arc of a buccal column (paracone). The anterior por-tion of the tooth is missing. This specimen is identified as anM3 because there is no appression facet for an adjoiningtooth on the hypocone or metacone. It is too large for themolariform tooth originally reported from Unalaska.

Apical wear is relatively minor, especially on the meta-cone, but dentine is exposed, demonstrating that the toothwas in wear but recently erupted. There is a slight wear faceton the lingual surface of the protocone. The striated, ob-lique, planar posterior wear surface on the hypocone tracksthe movement of the lower tooth dorsally and medially dur-ing jaw closure and chewing. Columns on the lingual side ofthe tooth do not extend to the base of the enamel, whereasbuccal columns are not so tall as lingual columns but extendto the base of the crown. A faint remnant of lingual cingu-lum is present. A minor enamel swelling occurs between thebases of the hypocone and metacone.

Unalaska right maxilla (MOTA 2004.009.02; Fig. 5).—One fairly complete right maxilla is preserved as a mold inmatrix that originally enclosed the bone. Fragments of thetusk remain in place. As preserved, the dorsal margin of themaxilla is gently convex upward. The lateral wall bulgesfrom the base of the tusk, as preserved, toward the dorso-medial margin, where the bulge flattens. The posteroventralportion of the mold indicates a rounded and curved bulgeanterior to the orbit. This may be either an anterior orbitalgroove between the superciliary ridge and the anterior rootof the zygomatic arch, or it may lie more ventrally, anteriorto the orbit and the lacrimal foramen. There is no evidenceof cheek teeth and it is considered that the ventral margin ofthe maxilla represents a diastema. The tusk is round in crosssection and has a diameter of 32 mm where it can be mea-sured. The long axis of the tusk is straight and divergesslightly from the midline.

Unalaska snout (USNM 529235; Fig. 6).—The anteriorportion of the snout housing the tusks is preserved as a natu-ral mold. Remnants of bone remain between and around theroots of the tusks and minor amounts of enamel adhere tothe tusk molds. The minimum distance between the roots of

Fig. 4.—Upper tooth fragments from the Arriaga Quarry: (A) MOTA2004.009.07, probably a deciduous upper premolar (orientation uncer-tain), including a section that was sawed off the tooth; (B) MOTA2004.009.01, posterior portion of left M3 (columns on left side of photo-graph are protocone followed by hypocone; the broken column on the rightis the remnant of the paracone, which is followed by the metacone). Scalebars = 1 cm.

Fig. 5.—Mold of right maxilla (MOTA 2004.009.02) with fragments of tusk. Scale bar = 5 cm.


the tusks is 62 mm. The maximum distance near the tips ofthe tusks is 147 mm. The maximum diameter of the left tuskis 22 mm. Taking our preferred interpretation that the bonerepresents premaxillae, the tusks curve laterally and into therock indicating that the view is from a dorsal angle to theinterior face of the ventral surface of the premaxillae. Be-tween the tusks the sediment mold shows a ridge, indicatinga groove or trough in the bones. This groove may representthe suture of the premaxillae along the midline. If this iscorrect, the specimen is the anterior portion of a skull withlarge upper canines.

Unalaska left dentary with M1–2 (MOTA 2004.009.03;Fig. 7).—This specimen comprises two blocks, the smaller(not illustrated) being a natural mold of the coronoid withsome bone skin and parts of two teeth. The anterior portionis missing. Two roots on the anterior tooth are clearly dis-cernible. The anterior portion of the crown of the anteriortooth, comprising three desmostylodont cusps in sagittalsection, remains in the rock. A natural mold of the labialportion of the crown of the posterior tooth is present.

The smaller block of MOTA 2004.009.03 fits to thelarger block that contains a major portion of the jaw fromthe base of the condyle to the symphyseal region, which isdamaged. The condyle itself is missing but it was placed ata level slightly below that of the occlusal surface of thecheek teeth. The angle of the jaw is broken away but most ofthe lateral surface of the posterior region is preserved andthere is no indication of an expanded angular area. Thecoronoid process is narrow (67 mm at its base) and its tip is

missing. The mandibular fossa is shallow. Anterior to theascending process the jaw is split sagittally. The horizontalramus is straight but the ventral margin tapers anterodor-sally at the symphysis as preserved in this specimen. Twocheek teeth are present, M1–2, seen in sagittal section, theposterior tooth placed 35 mm anterior to the base of theascending ramus. No indications of M3 have been discernedat this stage of preparation. The depth of the jaw below thecheek tooth is 122 mm. The tooth row is oriented somewhatanterobuccally to posterolingually across the dentary. Thelength of the horizontal ramus as preserved is 444 mm andthe total length as preserved is approximately 600 mm. Adiastema of 300 mm or more is present. A row of mentalforamina extends along the jaw. The root of an enlargedprocumbent tusk, which by analogy with other desmostyl-ians is a canine, extends at least 150 mm back from thebroken anterior edge of the jaw. The maximum diameter ofthe tusk is 50 mm. Although the symphyseal region of thejaw is damaged, there is no evidence of incisors. If present,incisors were probably small, and if more than one,crowded. More likely, the incisors were absent or lost byadulthood.

M1 (length, 48 mm) is damaged but is composed of threeranks of two columns, with the posterior rank broken away.An anterior cingulum is present but no medial accessorycusp can be discerned. M2 (length, 55 mm; height, 28 mm)also has three ranks of two columns. The columns decreasein diameter posteriorly. A small accessory cusp is present atthe posterior margin of the tooth. An unworn buccal acces-

Fig. 6.—Mold of snout (USNM 529235) with impressions of upper canine tusks. Scale bar = 5 cm.


sory cusp is present between the second and third ranks andthe mold shows a smaller buccal accessory cusp betweenthe first and second ranks. There is no anterior median cusp.

Unalaska left dentary fragment with M2–3 (MOTA2004.009.04; Fig. 8).—Little is left of the dentary but rem-nants of the coronoid process can be discerned. M2 is dam-aged buccally, anteriorly, and posteriorly, but it shows threeranks of two columns with columns decreasing in size pos-teriorly. There is strong lingual wear and stronger labialwear, such that the occlusal surface presents a longitudinalridge sloping buccally and lingually.

The M3 (length, 60 mm; width, 42 mm) has three ranksof two plus a large posterior median accessory cusp, and onthe buccal side, an anterior accessory cusp between the firstand second ranks and a smaller accessory cusp, which isonly in light wear, between the second and third ranks.There is no medial accessory cusp between the columns ofthe first rank.

Unalaska left M1–2 (MOTA 2004.009.05; Fig. 9).—Twopartial lower teeth are joined together in this specimen. Notrace of the bone housing the teeth remains. The teeth lackthe characteristic mesial talon and accessory cusps presentat the anterior end of upper teeth of Cornwallius or Desmo-stylus. Therefore, MOTA 2004.009.05 is identified as M1–2by comparison with teeth in MOTA 2004.009.03 andMOTA 2004.009.04 described above.

The lingual side of the teeth is broken away and only theposterolabial third of the M1 is preserved. Sediment adher-ing to the specimen demonstrates that the teeth were pre-served as an articulated unit, although the occlusal surface

of the anterior tooth lies at a higher level due to wear thanthe anterior portion of the posterior tooth. Both teeth areworn with dentine well exposed on the interior of the mainenamel rings. An appression facet on the posterior marginof the posterior tooth demonstrates that it was followed byan additional tooth, the M3.

M1, as preserved, appears similar in morphology to M2.Only the third rank of columns, a small posteromedial ac-cessory cusp, and a larger buccal accessory cusp anterior tothe posterobuccal column are preserved. The enamel of theposteromedial accessory cusp has not worn through to thedentine. The enamel of the buccal column between the sec-ond and third ranks is worn through to the dentine, but onlyslightly and along a concave wear surface that is inclinedbuccoventrally. There is a minor wear facet oriented verti-cally on the buccal surface of the cusp.

M2 is the more complete of the two teeth. It comprisessix major columns arranged in three ranks of two. The twocolumns of the anterior rank have worn through to the ex-tent that the dentine is broadly confluent transversely. Thereis a distinct posterior cingulum with a smaller but distinctposteromedial column closely placed between the main col-umns of the posterior rank. An additional smaller column,about equal in diameter to the posteromedial column, is pre-sent buccally between the second and third ranks, bringingthe total number of columns to eight. The two columns ofthe second rank are distinctly separated, as is the pair ofcolumns in the posterior rank. The valley between the sec-ond and third ranks is broadly open compared to that be-tween the first and second ranks. This open valley has twominor swellings on its floor, and in depth does not extend to

Fig. 7.—(A) left dentary (MOTA 2004.009.03) in lateral view and remaining in matrix; (B) occlusal view of M1–2. Scale bar = 5 cm for (A) and 1 cmfor (B).


the base of the crown. Two broad troughs are worn from theposterobuccal margin of the posterobuccal column from theocclusal surface toward the gum line. The small posterome-dial column is worn to the dentine but not so worn as theprimary columns. It is larger than the corresponding cusp onM2. The small buccal cusp is rounded buccally by wear, butthe enamel is not worn through to the dentine. There is nodistinct buccal cingulum, but the columns lose clear defini-tion toward the base of the crown.

Unalaska immature dentary (MOTA 2004.009.06; Fig.10).—This specimen is a right mandibular ramus, split sag-ittally and preserved in two sediment blocks. One blockcontains the left side of the jaw with its internal portionexposed because the lateral wall of the jaw remains in thecounterpart block. The left block contains the more nearly

complete fragment of the jaw, although it is missing most ofthe anterior portion and the ventral margin bordering themandibular canal posteriorly back to the angle of the jaw.The medial margin of the base of the condyle is present andthe coronoid outline is nearly complete except for the pos-terior edge approaching the apex. The condyle is at a levelhigher than the dorsal margin of the horizontal ramus. Acoronoid foramen is not apparent in either block.

Two tooth germs are preserved in the left block. Thecrown of the anterior tooth is well formed and visible inlateral view (length, 32 mm). The enamel is rugose andcrenulated, especially near the base of the cusps. Threewell-defined cusps are clearly present in lateral view, al-though the posterolateral portion of the anterior cusp and itsassociated root are broken off. The broken root and part ofthe enamel are preserved in the counterpart block. The bro-ken cusp shows that the enamel is thicker toward the apexand thinner toward the root. Root structure below the centercusp of the tooth is obscure. The strong root below the pos-terior cusp is visible. The apex of the posterior cusp is lo-cated at the junction of the horizontal and ascending rami.The apices of the anterior and possibly the central cuspsprotrude beyond the level of bone along the dorsal margin

Fig. 8.—Occlusal view of left M2–3 (MOTA 2004.009.04). Scale bar =1 cm.

Fig. 9.—Left M1–2 (MOTA 2004.009.05), occlusal view. Scale bar = 1 cm.


of the horizontal ramus. The posterior tooth germ is belowthe coronoid process and situated posterior to and separatedfrom the more anterior tooth. No clear pattern for the toothcan be discerned in its current state of preparation. A pieceof enamel is broken away from it and preserved on thecounterpart block.

As described above, the right block retains impressions

and remnants of the teeth in the left block. The major por-tions of the condylar and coronoid processes are preservedin this block, and the more mesial portion of the jaw is pre-served, approaching the region of the symphysis. The singleroot of a small tooth is present near the mesial extent of thefossils.

No teeth or primordia other than the anterior root and

Fig. 10.—Immature right dentary (MOTA 2004.009.06) in two blocks: (A) left side; (B) right side. Scale bars = 5 cm.


two crowns are discernible in this specimen. Specific iden-tification of position for each tooth is difficult to determineand exacerbated by the ontogenetically young age of theindividual.

Ray et al. (1994) documented and discussed the extremeontogenetic change seen in specimens of the basal desmo-stylian Behemotops proteus, and their study provides a ba-sis for considering tooth positions in the immature Un-alaska specimen. Originally, Domning et al. (1986) inter-preted a caniniform tooth in B. proteus to be P1 (or dP1)followed by an alveolus to accommodate a P2. Later, Ray etal. (1994) argued that the caniniform P1 of Domning et al.(1986) was in fact a true canine, implying restructuring ofthe jaw during ontogeny to accommodate an enlarging ca-nine. MOTA 2004.009.06 shows no indication of a crypt fora large canine. Assuming the specimen is well enough pre-served to determine, and recognizing that adults of the Alas-kan desmostylian have enlarged lower canines, this speci-men may have been too immature to see evidence of a largeor enlarging canine.

At any rate, the small root at the anterior end of the fossil,as it does not lie anterior to a canine, is considered to be thatof a P1 (or dP1). It is separated from the erupting posteriortooth by a large gap. The anterior and central (in lateralview) cusps of the erupting tooth have barely broken thesurface of the bone dorsally, and it is unclear whether thosecusps would have protruded through the gum line in life.The fact that three cusps (only) are visible in lateral viewmight suggest that this tooth is the fourth milk molar (dP4)because, as emphasized by Domning et al. (1986), dP4 inmany herbivorous mammals, and more especially in Behe-motops, is trilobed, caused by wear of the major cusps,which are aligned in three transverse sets. That pattern isconsistent with the three major cusps seen laterally in thetooth of the Unalaska specimen. However, as documentedby Uno (2000; see also Inuzuka et al. 1994), dP4 of Desmo-stylus has more cusps than can be accommodated in threetransverse rows. Given the view presented of the tooth, andthe morphology of the deciduous dentition in Desmostylus(Uno 2000), it is possible that it could be dP3. The develop-ing tooth following the erupting tooth would then be eitherdP4 or M1. In length, compared to Desmostylus (Uno 2000),the tooth falls at the small end of the range of dP4. Given thestate of tooth eruption, MOTA 2004.009.06 was from aneonate, or possibly a fetus.

Comments on the Genus Cornwallius

Hay (1923) named the genus Cornwallius on the basis pri-marily of two teeth, ascribed by him to be first molars, andoriginally named Desmostylus sookensis by Cornwall(1922). The features that distinguish the genus are “its low-crowned teeth furnished with a strong tuberculated cingu-lum” (Hay 1923, p. 107). In 1924, Hay entertained the no-tion that the teeth of Cornwallius were actually milk teeth ofDesmostylus because of their size and low crown height.The larger of the two teeth, he mused, could be the “hinder-most milk tooth of Desmostylus” (Hay 1924, p. 4). Consid-

ering that the issue must await additional material to be re-solved, he ended up regarding the larger tooth as an uppermolar and the smaller tooth as a lower molar, mostly basedon the patterns of the roots, which were not preserved butwhich he inferred from their broken bases. His doubt wasexpressed in his figure captions, in which he referred to theteeth as “supposed” upper and lower molars. He also refersto the larger tooth, the supposed upper molar, as the type inthe caption to his plate 1, figure 4, which it clearly is not ifcompared to the statements and figure in Cornwallis (1922),which designates the smaller tooth as the type. Hay wasfollowed by Vanderhoof (1937, p. 212–213, figs. 2–3), whoquestionably considered the type a lower molar and thelarger tooth an upper molar. However, by comparison withDesmostylus and the cast of the original tooth fragmentfrom Unalaska Island identified by G.E. Lewis, neither ofthe Sooke Formation teeth is an upper molar because ananterior rank of three cusps (Fig. 11), which is characteristicof upper molars of Desmostylus and is present in the Un-alaska tooth, is lacking in the teeth studied by Hay. A simi-lar conclusion was apparently reached by Reinhart (1959, p.66, fig. 9), who illustrated both teeth as lowers.

The type of Cornwallius sookensis can be compared di-rectly to a right dentary with two teeth (USNM 181741)from the Yaquina Formation of Oregon. The holotype isdirectly comparable to the posterior tooth in the Yaquinajaw in size [holotype measurements from Hay (1924):length, 33 mm; width, 24 mm; height, 16 mm; USNM181741: length, 34 mm; width, 27 mm; height, 19 mm] andin morphology. Both have five major cusps, two anterior,followed by a second row of two, and an unpaired posteriormedial cusp flanked on each side by a smaller accessorycusp. The posterior buccal accessory cusp is less developedin the holotype, interpreted as simple individual variation.

Fig. 11.—Illustrations of Cornwallius sookensis from Hay (1924) withoriginal captions: (A) “Supposed upper molar of Cornwallius sookensis.Showing grinding surface. Type. Front end upward.” (B) “Supposed leftlower molar. Showing grinding surface. Front end upward.” By compari-son with Desmostylus and the referred skull of Cornwallius (USNM181740), neither of these teeth is an upper molar (compare Figure 3).


Wear is greater on the lingual cusps as compared to the buc-cal cusps, indicating that the holotype is from the left side ofthe jaw. Wear has resulted in fusion of most cusps in theanterior tooth of USNM 181741. However, because of thesimilarity of the holotype and the posterior tooth of USNM181741, it is reasonable to relegate both specimens to thesame species, Cornwallius sookensis. The posterior tooth inUSNM 181741 seems most likely to be M2, and it thereforeseems reasonable that the larger topotypic tooth of Corn-wallius (length, 48 mm; width, 34 mm; height, 23 mm) is anM3, although it may simply be a larger M2.

Because a lower jaw from the Yaquina Formation of Or-egon can be referred to Cornwallius sookensis, it is reason-able that other corresponding material, including skulls andpostcranial elements, which have not proven to be taxo-nomically distinct, should also pertain to that species (Rein-hart 1982), and therefore can be used in comparisons withthe Unalaska material.

Identity of the Unalaska Desmostylian

At least four desmostylian individuals are known fromUnalaska Island, three adults (or near adults) based on leftlower molars and a neonate. All are considered to belong tothe same species because that, the null hypothesis, is themost parsimonious interpretation given that there are no ob-vious systematic differences among the sample. However,the sample is small and further discoveries may falsify ourhypothesis. For the moment, we make comparisons as if allspecimens were drawn from the same species population.

Compared to the holotype and referred specimens ofCornwallius sookensis, the M2 of MOTA 2004.009.05 islarger (length, 59 mm), but comparable in crown height, ifslightly higher (height, 25 mm), and in being less hypsodontthan Desmostylus. Teeth of the Unalaska desmostylian aresimilar to Cornwallius sookensis in development of cin-gula. If the type of Cornwallius sookensis is an M3, it differsfrom the M3 of the Unalaska material to a greater extentthan it does the M2 in lacking an additional posterior col-umn. The Unalaska desmostylian is derived with respect toC. sookensis in this character and possibly its slightly highercrown.

The Unalaska desmostylian is similar to C. sookensis inhaving a narrow, convergent symphysis and in the reduc-tion of incisors. The mold of the tusks of the Unalaska des-mostylian (USNM 529235) is interpreted as pertaining tothe upper jaw, meaning that a narrow lower jaw symphysiswith tusks, as exemplified by MOTA 2004.009.03, wouldnestle between the upper tusks when the jaws were ad-ducted. If USNM 529235 is not from the upper jaw, and ifour interpretation of MOTA 2004.009.03 is misguided dueto damage in the symphyseal region, then USNM 529235must be a lower symphysis and much broader than that seenin the Yaquina C. sookensis, an option that seems less rea-sonable to us. In a specimen from the Yaquina Formation(USNM 214740), the symphysis is narrow and converging(distance between tusks, 25 mm). The base of the left tusk isin place and has a slight downturn. There is little space for

incisors. In no specimen with tusks from Unalaska is therean indication of incisors, and given the narrow convergenceof the dentaries, if incisors were present they were minute,and if multiple, crowded.

The molar teeth from Unalaska differ from Behemotopsand Palaeoparadoxia because those genera lack the derivedcharacter of having the six main columns of the lower mo-lars arranged in three ranks of two. The Unalaska teeth arealso larger. The cingula are less developed and they arehigher-crowned than Behemotops and Palaeoparadoxia. Insize, the length versus (estimated) width of M2 falls with therange of Desmostylus M2 presented by Inuzuka et al. (1994,fig. 5). Two species of Desmostylus, D. hesperus and D.japonicus, are recognized by Inuzuka et al. (1994), but theyare indistinguishable based on dental evidence. The Un-alaska teeth differ from Desmostylus in being lower-crowned. Although the Unalaska desmostylian has lower-crowned molars, it has at least six major columns, similar toDesmostylus but more derived than Cornwallius. However,the narrow symphysis is more similar to Cornwallius thanto the broad symphysis of Desmostylus. The narrow sym-physis of Cornwallius is derived relative to Behemotops,Palaeoparadoxia, and Desmostylus. The teeth of Cornwal-lius are primitive relative to Desmostylus, so it seems plau-sible that the addition of more columns to molars in theAlaska desmostylian is a derived character convergent withthat seen in Desmostylus.

Age of the Dutch Harbor Member, Unalaska Formation

Desmostylians range in age from the early Oligocene tomiddle Miocene (Barnes and Goedert 2001). The type lo-cality of Cornwallius is in the Sooke Formation on Vancou-ver Island, British Columbia. At the time the Aleutians werebeing mapped, the Sooke Formation was generally consid-ered to be early Miocene in age, although there was somequestion as to whether it might be late Oligocene. Later,when Drewes et al. (1961) published their study of the ge-ology of Unalaska Island, the desmostylian identified asCornwallius, on the strength of the Lewis report, was usedto correlate with the Sooke and San Gregorio formations,and to suggest a late Oligocene or early Miocene age forstrata in the Unalaska Formation in which it was found. Inthe same publication (Drewes et al. 1961), the pelycopodMya sp. cf. M. truncata identified by F.S. MacNeil, andfound associated with the desmostylian, was reported. Ad-dicott (1971) repeated the early Miocene age based on Myacf. M. truncata. Marincovich (1990) shows the range ofMya truncata as beginning with the start of the middleMiocene, within the Newportian Stage, at 16.2 Ma. Lank-ford and Hill (1979) reported the pelecypods Chlamys andPododesmus, identified and interpreted by W.O. Addicott,and suggested by him to be Miocene in age.

In the same year that Drewes et al. (1961) published theirstudy, MacNeil et al. (1961) published a correlation chartthat showed the Cornwallius-bearing beds on Unalaska asearly Miocene, citing Byers (1959) as the authority. Dreweset al. (1961) and MacNeil et al. (1961) were followed by


Snyder and Fraser (1963), who simply state that the Un-alaska Formation contains lower Miocene fossils. Snyderand Fraser were the collectors of the Unalaska desmostylianmaterial now in the National Museum of Natural History onwhich much of the dating was based.

Mitchell and Repenning (1963), in their review of thechronologic and geographic distribution of desmostylians,citing Weaver et al. (1944), also accepted an early Mioceneage for the Sooke Formation, stating, “this is the only recordof Cornwallius which is datable on independent evidencewith any degree of accuracy.” Mitchell and Repenning(1963, p. 11) also note the association of Mya sp. with Corn-wallius in Unalaska, but the identification is given as Myasp. cf. M. grewingki, which as they state is “indicative of theBlakely Stage according to F.S. MacNeil.” The identifica-tion of the species of Mya was clarified in a study by Mac-Neil (1965, p. G28) in which he states, “In 1954, I identifiedsome poorly preserved specimens, found in associationwith teeth of Cornwallius sp. in a green volcanic greywackeon Unalaska Island in the Aleutians, USGS M-1679, as Myacf. M. truncata (Drewes and others, 1961, p.606). Furtherpreparation of these specimens, and a better knowledge ofthe species than I had then, indicates (sic) that this form isnot M. truncata. These specimens are distorted internalmolds and no spoons are visible. At the present time I aminclined to believe they are more likely to be either M. gre-wingki or M. kusiroensis.” In the same publication, Mac-Neil reported that the age of M. kusiroensis was late middleOligocene in Japan and on Popof Island, Alaska, andmiddle Oligocene in the Poul Creek Formation in YakatagaDistrict, Alaska. M. grewingki, which also had a doubtfuloccurrence in the Poul Creek Formation in Yakataga Dis-trict, was reported to be late Oligocene to early Miocene inJapan and Sakhalin Island.

The Blakely Stage as a time-stratigraphic unit has notbeen in widespread use by students of marine mammals,although it is listed, for instance, in quotation marks andparentheses in the chart given by Ray (1976, p. 423). Recentpaleomagnetic studies by Prothero and Nesbitt (in press)and Prothero et al. (in press) demonstrate that the BlakelyFormation (which is the type for the Blakely Stage) ismostly early Miocene in age but straddles the Oligocene-Miocene boundary, and the Sooke Formation is late Oli-gocene, falling within Chron C6Cr, or 24.1–24.8 Ma. Thefossiliferous Dutch Harbor Member of the Unalaska For-mation strikes into the Captains Pluton, a granodiorite in-trusion reported to be 13 Ma old by Lankford and Hill(1979). Given the available evidence, we judge the age ofthe desmostylians from Unalaska to fall within the intervalbetween 24.1–13 Ma, probably not in the lowest portion,but more likely at or just after the Oligocene-Mioceneboundary (23.03 Ma).

DISCUSSION

Specimens from Unalaska are difficult to prepare becauseof the dense matrix in which they are enclosed. Therefore,this report must be considered preliminary and contingent

upon the recognition of characters visible when the speci-mens are more fully prepared and a phylogenetic analysiscan be performed on them. Such an analysis also must awaitthe publication of relevant studies on Cornwallius. In theinterim, it is clear that the specimens from Unalaska havemore to offer toward understanding desmostylians than pre-viously recognized. Moreover, their geographic and tapho-nomic occurrence is informative.

In general, little postmortem transport occurs in marineinvertebrates (Kidwell and Flessa 1995). Little work hasbeen done on postmortem transport of marine mammals,aside from the work by Schafer (1972) and the referencestherein. A notable exception is the study by Liebig et al.(2003) who conducted a survey of beaches around the Colo-rado River Delta, Baja California, Mexico. Their surveyyielded remains of eight of the 18 species of mammalsknown to occur in the Gulf. Gross patterns showed thatcoastal species were more common than oceanic ones. Fur-ther, migrant and rare species were not as commonly foundas resident marine mammals.

Given the rarity of oceanic mammals in the Liebig et al.study, combined with the proximity of the landmass (i.e.,the Aleutian Islands) to the Unalaska site, it would seemsafe to say that the desmostylians of Unalaska were nearshore, coastal animals. Furthermore, it would seem safe tosay that they lived near where they died.

The Unalaska sample presents at least four individuals,one of which is a neonate, that appear to represent a singlespecies, which at this point seems distinct from other des-mostylian taxa. The presence of a neonate suggests that theUnalaska population was breeding, if not healthy, and in-habited the region at least during the birthing season, if notyear round. The fact that four individuals are represented,but that each individual is represented by a small proportionof its skeleton, mainly teeth and jaws, probably reflects acollecting bias stemming from these specimens being ob-tained from an active industrial rock quarry site. Neverthe-less, it is clear that there was also a geochemical tapho-nomic factor at work as shown by residual indications ofteeth in occlusion at burial with subsequent diagenetic lossof one or more teeth.

ACKNOWLEDGMENTS

It is our great honor to present this paper to a festschrift for Mary Dawson,for whom we have the highest respect and affection. The northernmostoccurrence of desmostylians seems an appropriate topic given her mani-festly important contributions to understanding fossil mammals at thenorthern extreme of our globe. LLJ and AF express a special debt to thelate C.A. Repenning, who piqued their interest in desmostylians. We thankthe National Park Service Alaska Regional Office, particularly RussellKucinski, for logistical and financial support for this project. Wendy A.Svarny-Hawthorne of the Ounalashka Corporation and Zoya Johnson ofthe Museum of the Aleutians facilitated and allowed this study. We thankBetty and Frank Arriaga, formerly owners of Marine Construction andEngineering (Marenco), for their efforts in preserving the desmostylianmaterial. AP and RG are greatly indebted to the Ounalashka Corporationand Marenco for support of their work on Unalaska. Jerah Chadwick, co-ordinator of the University of Alaska’s Aleutian Region program, was veryhelpful and made his facilities available. Outfitting by Whole Earth Pro-vision Company.


The authors thank Ron Tykoski, Deborah Nixon, Shelley Hartsfield,Mark Turner, and Kent Newman for preparing the specimens for study.Marge Noel and Fred Grady made a peel of USNM 529235 for us. DavidNorton helped us in the field. Many others have helped us in our pursuit ofAlaskan desmostylians by providing information, specimens, access, andreviews, including Evgenia Anichtchenko, James Baichtal, LawrenceBarnes, Brian Beatty, Annalisa Berta, Robert Blodgett, David Bohaska,Sean Charette, Karen Clautice, Tom Cockburn, Shaun and James Dickson,Daryl Domning, Ewan Fordyce, Jon Geisler, James L. Goedert, PatriciaHolroyd, Bonnie Jacobs, Louie Marincovich, Walter McFarland, K.C.McKinney, Yosuke Nishida, Norihisa Inuzuma, Aaron Pan, Michael J.Polcyn, Donald R. Prothero, Robert Purdy, Hans Tserchich, Mark Uhen,Diana Vineyard, and Dale A. Winkler.

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Desmostylian Remains from Unalaska Island, Aleutian Chain, Alaska

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