Steller's Sea Cow

Amchitka, Alaska

i /

Steller's Sea Cow 

(Hydrodamalis gigas} of 

Late Pleistocene Age from 

Amchitka, Aleutian Islands, 

Alaska

By FRANK C. WHITMORE, JR, and L. M. CARD, JR

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1036

Description of the first specimen of the 

extinct Arctic sea cow, Hydrodamalis gigas, 

to be found in place in Pleistocene deposits 

outside the Commander Islands, U.S.S.R.

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1977
UNITED STATES DEPARTMENT OF THE INTERIOR

Cecil D. Andrus, Secretary

GEOLOGICAL SURVEY

V. E. McKelvey, Director

Library of Congress Cataloging in Publication Data

Whitmore, Frank C.

Steller's sea cow (Hydrodamalis gigas) of late Pleistocene age from Amchitka, Aleutian Island, Alaska.

(Geological Survey Professional Paper 1036)

Bibliography: p.

Supt. of Docs, no.: I 19.16:1036

1. Hydrodamalis gigas, Fossil. 2. Paleontology Pleistocene. 3. Paleontology Alaska Amchitka Island.

I. Card, Leonard Meade, 1923-joint author. II. Title: Steller's sea cow... HI. Series:

United States Geological Survey Professional Paper 1036

QE882.S6W49 569*.5 77-608068

For sale by the Superintendent of Documents, U.S. Government Printing Office

Washington, D.C. 20402 

Stock Number 024-001-03001-2
CONTENTS

Page Page

..................................... i Description of the Amchitka Hydrodamalis Continued

Introduction ............................................ l Mandible ........................................... 9

Acknowledgments ....................................... 3 Vertebrae ........................................... 10

Occurrence and age of the Amchitka specimens ........... 3 Scapula ............................................. 11

Stratigraphic and structural relations ................. 3 Humerus............................................ 12

Other fossils ........................................ 5 Radius and ulna ..................................... 13

Environment ........................................ 6 Ribs .......••••••....••••••••••••••••••••••••••••••• 13

Age of the deposit ................................... 7 Chevron bone ....................................... 15

Composition of the collection ............................. 7 Morphologic conclusions .............................. 16

Description of the Amchitka Hydrodamalis ................ 8 Discussion .............................................. 18

..................................... 9 References cited ......................................... 19

ILLUSTRATIONS

[Plates follow "References Cited"]

COVER ART Steller's sea cow, reproduced by permission from the artist from a painting by Alfred G. Milotte. 

PLATES 1-8. Hydrodamalis gigas. Page

FIGURE 1. Index map of the Aleutian arc ................................................................................. 2

2. Index map of Amchitka Island ................................................................................ 4

3. Photograph of interglacial beach deposit ....................................................................... 5

4. Cross section of South Bight graben ........................................................................... 6

5. Photograph of mandibles of Hydrodamalis ..................................................................... 6

6. Photograph of rib of Hydrodamalis ............................................................................ 8

7-10. Drawings:

7. Key to measurements of mandibles of Hydrodamalis ...................................................... 10

8. Key to measurements of scapula and humerus of Hydrodamalis ............................................ 13

9. Key to measurements of radius and ulna of Hydrodamalis ................................................. 15

10. Rib of Hydrodamalis .................................................................................... 16

TABLES

Page

TABLE 1. Foraminifera and other fossils associated with Hydrodamalis from the South Bight interglacial beach deposit, Amchitka

Island ................................................................................................... 7

2. Measurements of mandibles of Hydrodamalis gigas ............................................................. 11

3. Measurements of vertebrae of Hydrodamalis gigas .............................................................. 12

4. Measurements of forelimb of Hydrodamalis gigas ............................................................... 14

5. Comparison of Amchitka specimen with immature specimen from Bering Island measured by Von Nordmann (1863) 17

in

STELLER'S SEA COW (HYDRODAMALIS GIGAS) OF LATE PLEISTOCENE AGE 

FROM AMCHITKA, ALEUTIAN ISLANDS, ALASKA

By FRANK C. WHITMORE, JR., and L. M. GARD, JR.

ABSTRACT

A partial skeleton of Hydrodamalis has been collected from a 

Pleistocene interglacial beach deposit, 35 meters above present sea 

level, on Amchitka, Aleutian Islands, Alaska. This is the first discovery of the genus in place in Pleistocene deposits outside the Commander Islands (Komandorskiye Ostrova), U.S.S.R. Parts of the 

young but apparently nearly full grown individual were found in a 

position which suggested that the animal, after death, had been 

washed into shallow water or up onto a beach. The Pleistocene 

animal was toothless, as was the modern Steller's sea cow (Hydrodamalis gigas), which was exterminated by Russian hunters 

about 1768. Like the modern form, the Pleistocene sea cow undoubtedly subsisted on kelp. It is indistinguishable from the modern 

species. A uranium-series date of 127,000±8,000 years on bone from 

this beast is consistent with a generally accepted age of the last major interglacial stage.

INTRODUCTION

The giant Arctic sirenian Hydrodamalis gigas (Zimmermann), popularly known as Steller's sea cow, was 

discovered in 1741 along the coast of what is now called 

Bering Island (Beringa Ostrov) in the Commander Islands (Komandorskiye Ostrova), U.S.S.R. (fig. 1). Its 

discoverer, and the only naturalist who observed it 

alive, was G. W. Steller, a German who sailed on the 

second voyage of the Danish explorer Vitus Bering, in 

the service of the Russian government (Golder, 1925). 

Steller's description of the animal was published (1751) 

posthumously and was translated from Latin into 

English in 1899. A female specimen of Hydrodamalis, 

measured and dissected by Steller (1751, p. 294), was 

7.4 m long from the extremity of the upper lip to the extreme right cornu of the caudal fork. The animals are 

estimated to have attained a weight of 10 metric tons 

(Scheffer, 1972, p. 913).

Steller's sea cow was discovered when Bering's crew 

was shipwrecked on Bering Island in the course of their 

return voyage from North America. The starving Russians captured some sea cows with great difficulty, not 

because they were fierce but simply because their bulk 

made them hard to haul ashore, and found them to be 

very good eating. This news was passed by the survivors 

to subsequent Russian voyagers who, in succeeding 

years, made the Commander Islands a victualing stop

on North Pacific fur-hunting expeditions. Stejneger 

(1887, p. 1049) stated that from 1743 until 1763 "hardly 

a winter passed without one or more parties spending 

eight or nine months in hunting fur-animals there, during which time the crews lived almost exclusively on 

the meat of the sea-cow." The result was that, by 1768, 

Hydrodamalis was extinct (Sauer, 1802; von Baer, 

1840; Brandt, 1846; Stejneger, 1887, Lucas, 1891).

Steller, in 10 months on Bering Island, had ample opportunity to observe the daily activities of Hydrodamalis from his hut on the shore. He reported that 

the animals congregated in herds, feeding incessantly 

on kelp in shallow water. They were fond of shallow 

sandy places along the seashore, especially along the 

mouths of rivers and creeks. "As they feed they move 

first one foot and then the other, as cattle and sheep do 

when they graze, and thus with a gentle motion half 

swim and half walk" (Steller, 1899, p. 198). In his 

anatomical description, Steller stated that the neck is 

short but movable: It "has its independent action, a motion observed in the living animal only when it feeds; 

for it bends its head in the same way as cattle on dry 

land" (1899, p. 187).

The need for vast amounts of seaweed in shallow 

water was certainly a limiting factor in the distribution 

of Hydrodamalis, but, even for an animal of such 

specialized requirements, our knowledge of its range is 

slight. Only in the Commander Islands is there convincing evidence of the sea cow's existence in historic time, 

although there has been much speculation on its existence elsewhere in the North Pacific area (Gard and 

others, 1972, p. 867). A single rib was found on the island of Attu in the Aleutians (Brandt, 1868, p. 294).

During the course of the U.S. Atomic Energy Commission operations on Amchitka, Gard had occasion to 

talk with Mr. Paul Higdon, then labor foreman for 

Holmes and Narver, Inc. Higdon had been on Shemya 

Island (56 km east of Attu) during construction of an 

airstrip in World War II and remembered a complete 

skeleton of a large marine mammal being uprooted and 

pushed aside by construction equipment. Shafer (in 

Gates and others, 1971, p. 783) reported that the

1
STELLER'S SEA COW, AMCHITKA, ALEUTIAN ISLANDS, ALASKA

160* 150*

60"

501

/c

0 100 200 300 KILOMETERS 

APPROXIMATE SCALE 

AT LATITUDE 52' N

FIGURE 1. — Index map of the Aleutian arc, showing Amchitka and Bering Islands.

bedrock surface of Shemya is a wave-cut platform 

"most likely of pre-Wisconsinian age" covered by 

marine deposits, and then glaciated. Perhaps an opportunity to recover the entire skeleton of a sea cow was 

lost at that time.

Many sea-cow bones were found along the shore of 

Bering Island (Chelnokov, 1969; Scheffer, 1973). Stejneger (1884) took advantage of this situation to make a 

collection for the U.S. National Museum. Some bones 

were collected by Stejneger himself; others were 

purchased from natives. The composite skeleton now 

exhibited at the U.S. National Museum of Natural 

History consists of bones from the Stejneger collection. 

Among composite skeletons mounted in European 

museums, one of the best is that at the Naturhistoriska 

Riksmuseet in Stockholm, Sweden (pi. 1). Sea-cow 

bones on Bering Island were commonly covered by a 

layer of earth and gravel; Nordenskjbld (1882, p. 280) 

reported it to have been 30 to 50 cm thick: "In order to 

find them, as it would be too troublesome to dig the 

whole of the grassy bank, one must examine the ground 

with a pointed iron rod * * *." All the bones were apparently found on a low terrace just above the beach 

"which may be accounted for by the accumulation of 

storm-wash under the present conditions or very nearly 

so" (Dawson, 1894, p. 125). Some bones were found at a 

considerable distance inland. In the Stejneger papers in 

the Archives of the Smithsonian Institution are notes

by Prof. B. W. Evermann "concerning the Rhytina recently acquired by the Museum," which state that the 

bones, which were purchased from a "creole" on Bering 

Island in 1892, lay under about 1 m of sand, three versts 

(about 3 km) back from the water. Most of the bones in 

the Stejneger collection at the U.S. National Museum of 

Natural History are white and hard but not permineralized or replaced. An exception to this is USNM 

218376, an os occipitis and the first and seventh ribs of 

the right side, which have a red-ocher color. These 

specimens are from the anterior part of a skeleton 

found by Stejneger (1884, p. 61-62) in a sand bank 3.6 

m high, 150 m from the sea, and not less than 3-4 m 

above high tide. The skeleton was on its back. The 

bones were soft and of a soapy consistency, most of 

them too soft to be collected. In both softness and red 

color, these bones resemble some of those discovered on 

Amchitka, which raises the possibility that there may 

be sea-cow bones of Pleistocene age on Bering Island in 

addition to those left by the Russian fur hunters.

Considering the frequency and violence of storms in 

the Commander Islands, it is not surprising that bon >s 

of sea cows butchered in the 18th century should have 

since been buried under a meter or so of storm-tossed 

sand. Those buried by the infrequent storms that 

caused waves to roll far inland could have subsequently 

been covered by vegetation. The mode of occurrence of 

the bones led Woodward (1885, p. 457-458) to conclude
OCCURRENCE AND AGE OF AMCHITKA SPECIMENS

that specimens collected by Robert Damon for the British Museum (Natural History) were of Pleistocene or 

early Holocene age: "The specimen now in the British 

Museum was obtained from compact peat, and all the 

vertebrae and other bones having cavities in them were 

full of peat-growth when they arrived, as was also the 

skull." Without careful field study it is impossible to tell 

whether sea-cow bones from Bering Island are of 

Pleistocene or Holocene age, but the historic evidence 

for extensive killing of sea cows in the 18th century 

leads to the conclusion that most of the bones date from 

that period.

The 18th-century range of Hydrodamalis, restricted 

to the Commander Islands, was certainly that of a relict 

species, perhaps on its way to extinction even without 

the influence of man. It is logical to assume that the 

earlier range of Hydrodamalis extended eastward along 

the Aleutian chain. If this was so during the last 10,000 

years or so, Hydrodamalis would have been ideal prey 

for the sea-hunting Aleuts (Domning, 1972). However, 

there is no known archeological evidence that the 

Aleuts hunted the sea cow. Desautels and others 

(1969-70), in a report on the archeology of Amchitka, 

recorded many sea-mammal bones from old Aleut middens but included no Hydrodamalis. Six sites (Roger 

Desautels, written commun., 1971), which revealed occupation over a 2,500-year span, were investigated. 

Jean S. Aigner (written commun., 1971) reported that 

there are no known examples of Hydrodamalis from 

any Aleut middens and that a large number of middens 

had been sampled, some as much as 4,000 years old. 

Domning (1972) speculated that some middens ancient 

enough to contain Hydrodamalis bones may still exist 

but that most of them have been covered by the rising 

sea.

The only occurrence known to us of Hydrodamalis 

bone in a midden was reported by Hall (1971) from a 

16th-century Eskimo site at the confluence of the 

Noatak River and Kangiguksuk Creek in northwestern 

Alaska (67°58' N., 161°50' W.). A rib, which had the distal end sawed off and which was heavily marked with 

cuts on both sides, was found in floor fill within the 

house. It is unquestionably associated with the rest of 

the cultural material at the site (Hall, written commun., 1976). Hall (1971, p. 23) also reported the presence at the site of 133 fragments of fossil mammoth 

ivory and a bison horn and phalanx, all of Pleistocene 

age. He pointed out (1971, p. 56) that "mammoth ivory 

and the bones of extinct animal species are frequently 

washed out of the permanently frozen banks when the 

Noatak shifts its course."

The Kangiguksuk site is about 100 km from the 

ocean. The rib from this site is described in more detail 

on p. 15.

Hydrodamalis was unknown south of Alaska until 

1967, when Jones (1967) reported that a badly eroded 

cranial fragment had been brought up in a trawl from 

the bottom of Monterey Bay, Calif., and that it had 

yielded a C14 radiometric age of 18,940±1,100 years 

B.P. The Monterey specimen is in the lower part of the 

size range of a series of modern skulls from Bering Island.

Shikama and Domning (1970) reported a rib of Hydrodamalis from the late Pliocene of the island of 

Honshu, Japan. They also mentioned that two specimens of a new species of Hydrodamalis have been discovered in the Pliocene of California and that this 

species is morphologically intermediate between Metaxytherium jordani Kellogg of the late Miocene and Hydrodamalis. (See also Domning, 1970.).

ACKNOWLEDGMENTS

We thank Daryl P. Domning for many helpful discussions and for reviewing this paper before publication. 

The photographs of the bones were taken by Robert H. 

McKinney and Haruo E. Mochizuki, and the drawings 

for figures 7 -10 were made by Richard J. Mjos. Thomas 

D. Washburn prepared the specimens for study. We are 

grateful to Dr. Tor Orvig and Mr. Carl Edelstam of the 

Naturhistoriska Riksmuseet, Stockholm, Sweden, for 

furnishing photographs of their mounted composite 

specimen of Hydrodamalis and for permission to 

reproduce them. The drawing on the cover is from a 

painting by Alfred G. Milotte; permission to use it has 

been granted by the artist. We thank the U.S. Atomic 

Energy Commission for logistical support on Amchitka. 

The Department of Anthropology, Yale Peabody 

Museum, kindly loaned us a rib of Hydrodamalis from 

an archeological site in northwestern Alaska.

OCCURRENCE AND AGE OF THE 

AMCHITKA SPECIMENS

STRATIGRAPHIC AND STRUCTURAL RELATIONS

In 1969 Gard discovered a partial skeleton of Hydrodamalis gigas 35 m above present sea level in unconsolidated sediments exposed in the sea cliff at the head 

of South Bight on Amchitka Island (figs. 2, 3). This exposure, first described by Powers, Coats, and Nelson 

(1960, p. 542) as an emerged Pleistocene interglacial 

beach deposit, was preserved because it was penecontemporaneously downdropped in a small (800-m wide) 

east-northeast-trending graben within the Amchitka 

Formation of early Tertiary age (fig. 4). These beds 

were conformably deposited on an erosion surface that 

truncates earlier Pleistocene lacustrine and marine 

sediments. The earlier semiconsolidated sediments also
610000

STELLER'S SEA COW, AMCHITKA, ALEUTIAN ISLANDS, ALASKA

I79°E ————————I——————————I—1———————————I——————————— 670000 30

5720000

5I°30'--

5690000

Bird Cape

BERING

}Chttka SEA

p*--..

)Chitka Point

PA C I F 1C

Ivakin Paint

OCEAN

180°

AMCHITKA ISLAND

10 MILES

10 15 KILOMETERS 

-H— I__

179° E

FIGURE 2. — Index map of Amchitka Island.

620000

Universal Transverse Mercotor Projection (UTM) 

IOOOO meter grid ticks-, zone 60

670000

were trapped in this graben and were tilted and faulted 

prior to their truncation. The erosion surface, itself 

tilted and faulted, ranges from 34 m above mean sea 

level on the north side of the graben to 15 m above 

mean sea level on the south side of the graben. This surface and the overlying beach deposit are believed to be 

related to a stillstand of the sea during the South Bight 

II marine transgression that cut the most extensive terrace on Amchitka Island (Szabo and Gard, 1975). This 

terrace is as much as 1.5 km wide. The inner edge of the 

terrace is now 37 to 49 m above sea level. 1

The beach deposit ranges in thickness from about 6 

m on the north side of the graben to about 30 m on the 

south side of the graben. The deposit was not found on 

the Bering Sea side of the island and does not appear to 

extend more than 500-600 m back from the sea cliff.

The deposit consists of loosely consolidated, poorly 

bedded sand to coarse boulder gravel, which is richly

1 Altitudes at base of abandoned sea cliffs have been determined from 1968 topographic 

maps by Holmes and Narver, Inc., scale 1:6,000, contour interval 10 feet. This terrace was erroneously reported as 52 m (Gard and others, 1972, p. 868).

fossiliferous. Some beds near the base of the deposit are 

composed almost entirely of cross-stratified shell fragments; in a few places, discontinuous beds in the lower 

part of the deposit are composed entirely of unbroken 

pecten shells, some of which are articulated. Beds in 

which the partial skeleton of Hydrodamalis was found 

(fig. 5) are 9 m above the base of the deposit (near the 

upper middle part) and consist of loose pebbly sand that 

contains random cobbles and boulders and abundant 

shell material, including echinoid plates and spines and 

Foraminifera. Many beds as much as 30 cm thick are 

composed of well-rounded hornblende-bearing white 

pumice pebbles, which average 2.5 cm in diameter but 

which may be as large as 7 cm. The buoyant low-density 

pumice pebbles probably were derived from eruptions of 

one of the nearby active volcanoes. Near the base of the 

deposit, many boulders are coated with calcium carbonate algal secretions, and fragments of these coralline 

algae (probably Lithothamnion sp.), similar to those 

found on modern Aleutian Islands beaches, are interspersed between the boulders. An isolated rib of Hy~
OCCURRENCE AND AGE OF AMCHITKA SPECIMENS

FIGURE 3. — Interglacial beach deposit overlying tilted unconformity (1) in the cliff face at South Bight, Amchitka Island. Hydrodamalis 

(USNM 170761) was found at (2). Hydrodamalis rib (USNM 181752) was found at (3), just above unconformity. White bed above (3) is 

composed of cross-stratified shell fragments. Photograph by R. H. Morris.

drodamalis was found in place near the base of the 

deposit (fig. 6).

The difference in thickness between the north and 

south ends of the deposit is the result of contemporaneous southward tilting of the graben block while 

these beds were being deposited, which caused a discordance of the bedding in the southern part of the deposit 

and tilting of the erosion surface at the base. At the 

southern end, the material that forms the generally 

coarser grained upper part of the section apparently 

was eroded from the scarp of the more active southbounding fault. We assume that these boulders, which 

are as much as 0.6 m in diameter, were deposited in 

deeper water, where they escaped abrasion, as many 

are angular or only slightly subrounded.

Although the deposit has been studied in detail, no 

erosional unconformity is recognized within it.

OTHER FOSSILS

In addition to bones of Hydrodamalis, the gravel 

deposit yielded a partial skull of the Steller sea lion, 

Eumetopias jubata Schreber, the distal half of the 

radius of a large whale, and a fragment of the tusk of a 

small walrus.

The presence of a rich invertebrate fauna in the 

deposit has been known for some time. From 1946 to 

1951, U.S. Geological Survey personnel collected a

molluscan fauna (Powers and others, 1960). A report on 

Foraminifera collected by R. R. Coats in a gravel pit 200 

m north of the Hydrodamalis site was published by 

Cushman and Todd (1947). In 1969, Allison (1973) collected a large invertebrate fauna from this deposit.

The present authors collected samples of sand that 

contains Foraminifera during excavation of the sea-cow 

bones in 1971. These were collected from 0.3 m above 

the base of the deposit, from the sea-cow horizon, and 

from 1 m above the sea-cow horizon. Foraminifera in 

these samples, identified by Ruth Todd (table 1) are all 

living species and provide no evidence of age. In addition, in 1969, a collection of Foraminifera was made by 

Gard from about 1 m below the sea-cow horizon and 

was identified by the late R. L. Pierce, U.S. Geological 

Survey. According to Todd (written commun., 1971), 

the 1969 collection (table 1, col. 3) is quite similar to the 

other three. The 1969 collection and the 1971 collections (taken as a whole) have seven species in common. 

She noted that the 1947 collection (Cushman and Todd, 

1947) is much richer in variety of foraminiferal species 

and that only six species which she identified in these 

more recent collections are the same as those in the 

1947 list. All these collections of Foraminifera are from 

the interglacial beach deposit, and all but one are from 

about the same horizon, although Todd suggested that 

the fauna collected in 1969 and 1971 might be from 

shallower water than those in the 1947 collection.
STELLER'S SEA COW, AMCHITKA, ALEUTIAN ISLANDS, ALASKA

C^

200 400 600 FEET

QUATERNARY

7*-_-_-_-

— — - —

DUNE SAND

INTERGLACIAL BEACH DEPOSIT

Triangle shows Hydrodamalis locality

\

»«*>»'••

S=E==5

^SEr:E=;

100 200 METERS 

EXPLANATION

MARINE DEPOSITS

LACUSTRINE AND FLUVIALl?) DEPOSITS

TERTIARY

AMCHITKA FORMATION

FIGURE 4. — Diagrammatic cross section of South Bight graben, Amchitka Island. Faults mainly generalized. Vertical exaggeration x 2.

FIGURE 5. — Partial mandibles of Hydrodamalis gigas, as found on 

Amchitka Island, upside down in beach sand, anterior end pointing 

toward lower left corner of photograph. Photograph by F. C. Whitmore, Jr.

ENVIRONMENT

Hydrodamalis apparently lived in an environment 

much like that of Amchitkan waters today. According 

to Cushman and Todd (1947, p. 60) "while the 

[foraminiferalj fauna is decidedly one of cold waters, it 

is not by any means arctic, and most of the species 

found today are in waters to the south of this area. * * * 

The great abundance of two species of Globigerina, 

pelagic forms, would indicate that ocean currents from

warmer areas, such as the present Japanese Current, 

also influenced this area." A comprehensive study by 

Allison (1973) on the paleoecology of the invertebrate 

megafossils from the deposit indicates that the water 

temperature at that time was almost the same as it is 

today. Allison reported that when these mollusks were 

living, the mean February water temperature was probably about 3.9°C, and the mean August water temperature was 10.0°—11.7°C; these temperatures compare with present-day water temperatures of 3.9°C for 

February and 10.0°C for August.

Depth of the water in which these fossiliferous beds 

were deposited could not have been more than 25 m and 

probably was much less. At least part of the time, this 

area was within or even slightly above the intertidal 

zone. A maximum water depth may be assigned by the 

presence of coralline algae on and between boulders 

near the base of the deposit. The maximum depth at 

which sublittoral algae will grow is primarily dependent 

on the amount of light that will penetrate the water. 

This, in turn, depends on latitude and water turbidity 

(Smith, 1938, p. 296). Coralline algae (Rhodophyta) in 

the North Atlantic Ocean are rarely found at depths 

below 30 m. At Amchitka Island today, they are found 

from the intertidal zone to a depth of at least 23 m. The 

foraminifers Quinqueloculina and Cibicides are known 

from nearshore deposits and comparatively shallow 

water (Cushman and Todd, 1947, p. 60). Allison (1973, 

p. 42) stated that "the majority of the South Bight 

fauna lived in shallow (0—23 m(?)) water on the open 

coast, * * * [and] the environment must have been 

almost identical to that of South Bight today."

The presence of beds of pumice pebbles indicates that 

the pumice fragments floated to this area, were 

rounded by wave action, and stranded on the interglacial beach.
COMPOSITION OF THE COLLECTION

TABLE 1. — Foraminifera and other fossils associated with Hydrodamalis from the South Bight 

interglacial beach deposit, Amchitka Island

Collections

Fossils

1971

1 m above

Hydrodamalis

horizon 1

1971

Upper part of

Hydrodamalis

horizon 1

1969

1 m below

Hydrodamalis

horizon2

1971

15m above

beach. 0.3 m

above base of

Hydrodamalis

horizon 1

Bolivina decussata Brady .................. X

sp. cf. B. pseudopicata Heron-Alien and 

Earland ............................

Buccella frigida (Cushman) ................

Cassidulina californica Cushman and Hughes X

islandica Norvang ....................

teretis Tappan ........................

tortuosa Cushman and Hughes .........

Cibicides lobatulus (Walker and Jacob) ..... X

Elphidiella arctica (Parker and Jones) ....

Elphidium alaskense Cushman and Todd . .

clavatum Cushman ..................

frigidum Cushman .................... X

Globigerinasp. aff. G. bulloides d'Orbigny ... X

pachyderma (Ehrenberg) .............. X

Karreriella baccata alaskensis Cushman and 

Todd ..................................

Genus rel. Neoconorbina tabernacularis 

(Brady) ................................

Oolina borealis Loeblich and Tappan ........

Planulina alaskensis Cushman and Todd ....

Polymorphina kincaidi Cushman and Todd .. 

Pyrgo sp. cf. P. elongata (d'Orbigny) .........

Quinqueloculina agglutinata Cushman ......

akneriana d'Orbigny ..................

seminulum (Linne) .................... X

Rosalina wrightii (Brady) ................

Rotalia columbiensis (Cushman) ............ X

Trichohyalis ornatissima (Cushman) ......

Triloculine trigonula (Lamarck) ..........

Microscopic gastropods ..................

Echinoid spines (very abundant) .........

1 Identification by Ruth Todd.

2 Identification by R. L. Pierce.

AGE OF THE DEPOSIT

Uranium-series dating of fossil shells and bone from 

the interglacial beach deposit at South Bight has 

yielded an average age of 127,000±8,000 years (Szabo 

and Gard, 1975). A lengthy stillstand of the sea is indicated by the extensive terrace that was cut on the island. Apparently, when the sea reached its maximum 

height, it rapidly bevelled the underlying semiconsolidated sediments in the graben. Continued subsidence of 

the graben allowed the thick beach deposits to accumulate and to be preserved while the sea persisted in cutting the terrace on much harder Tertiary bedrock 

elsewhere on the island.

Although Allison (1973) presented arguments that 

this deposit is of Kotzebuan(?) age (pre-Illinoian, according to Hopkins, 1967, p. 50), the radiometric age 

date of 127,000±8,000 years seems inconsistent with 

recent fission-track dating of 0.6 m.y. (million years) 

for ash beds in late Kansan or early Yarmouth deposits 

in the Western United States (Izett and others, 1970).

The radiometric age of the sea-cow bone from the upper 

middle part of the deposit seems to be reasonably consistent with age dates of the Barbados III sea-level maximum (Mesolella and others, 1969), which has an 

average radiometric age of 125,000±6,000 years, and 

with Terrace C in southern California (Szabo and 

Rosholt, 1969), which has radiometric ages averaging 

131,000±15,000 years. These dates are believed by 

Richmond and Obradovich (1972) to be of late 

Pleistocene age.

COMPOSITION OF THE COLLECTION

Gard's initial discovery was of bone fragments at the 

base of a cliff. He traced the bones to their source and 

collected several vertebral centra and parts of a 

forelimb. These were identified by G. E. Lewis as 

belonging to Hydrodamalis. Lewis' identification was 

corroborated by Whitmore, who compared the bones 

with specimens of Holocene age, which were collected 

on Bering Island by Leonhard Stejneger in 1882 and
STELLER'S SEA COW, AMCHITKA, ALEUTIAN ISLANDS, ALASKA

FIGURE 6. — Rib of Hydrodamalis (USNM 181752) at base of South 

Bight II interglacial beach deposit, Amchitka Island. Photograph 

by F. C. Whitmore, Jr.

1883 and which are now in the collections of the U.S. 

National Museum of Natural History. In May 1971 

Gard and Whitmore uncovered more bones in place in 

the cliff (fig. 5). The bones found on the cliff face and 

those uncovered just beneath the surface were hard 

and well preserved, although not permineralized; they 

apparently had case hardened upon contact with the 

air. As we dug farther into the cliff, the bones found 

were of increasingly poor quality, at first being crumbly, then, about 1 m in from the cliff face, being soft and

of a soapy consistency, easily scratched with the fingernail. Stejneger (1884, p. 61-62) found bones similarly 

preserved on Bering Island.

Altogether, the following bones were collected at the 

Amchitka locality: The horizontal ramus and a small 

part of the ascending ramus of the left mandible; the 

anterior half of the horizontal ramus and the angular 

region of the right mandible; centra of the last three 

cervical vertebrae and of the first thoracic vertebra; 

left scapula; distal half of right humerus and distal end 

and fragments of proximal end of badly preserved left 

humerus; left and right radius and ulna; rib fragments; 

and a chevron bone. About half a meter back in the cliff 

from the mandibles was a large amorphous mass of soft 

red material. Perhaps this was all that remained of the 

skull. All these bones came from a single animal that 

probably had drifted into shallow water after death and 

had been quickly buried by sand. The left forelimb, including the scapula but excluding carpals and metacarpals, was in articulation when found; the position of the 

limbs relative to that of the vertebrae and jaws indicated that the animal was on its back when it was 

buried.

The epiphyseal cartilage of the long bones was still 

unossified, and none of the articular ends of the long 

bones was found. The radius and ulna were not 

coossified as they are in fully adult specimens of the 

modern Steller's sea cow, and the mandibular 

symphysis was only slightly fused. Although the 

Amchitka specimen was as large as some fully grown 

Bering Island Hydrodamalis, it was a young individual.

These bones were assigned by the U.S. National 

Museum of Natural History, Department of 

Paleobiology, the number USNM 170761.

In addition to the bones just described, a single rib of 

Hydrodamalis was found 0.1 m above the base of the interglacial beach deposit, 400 m south of the other specimens (fig. 6). The specimen consists of the distal twothirds of about a twelfth rib of a very large animal. It 

was assigned USNM 181752. A small humerus, doubtless from a very young individual, was collected by Gard 

in August 1972 at the base of the cliff, about 50 m south 

of the locality of USNM 170761. It was assigned USNM 

186807. Also, four fragments of a large sirenian rib 

were collected at South Bight by Richard C. Allison and 

deposited in the National Museum by Daryl P. Domning.

DESCRIPTION OF THE AMCHITKA

HYDRODAMALIS

The bones of the Amchitka specimen will be compared with those of specimens collected on Bering Island by Leonhard Stejneger in 1882 and 1883. Stejneger's specimens, preserved by the U.S. National
DESCRIPTION OF THE AMCHITKA HYDRODAMALIS

Museum of Natural History, are probably the remains 

of animals killed for food by Russian fur hunters in the 

18th century.

MEASUREMENTS

The system of measurements illustrated in figures 

7-9 was designed by Daryl P. Domning for his studies 

of Sirenia and is used here, with only slight modifications, in the interest of uniformity. Because the 

Amchitka bones are incomplete, Domning's system 

could not be used throughout.

MANDIBLE

Plate 2, all figures; plate 3, figures 1-4; table 2

The Amchitka mandible was compared with 15 mandibles from Bering Island. Nine measurements were 

made on each specimen (fig. 7; table 2). All measurements of the Amchitka mandible are within the range 

of measurements of the Bering Island group. In all but 

one measurement ("as," which may be correlated with 

youthful age, or may simply be due to individual variation), the Amchitka specimen is at or near the upper 

end of the range of measurements. This may signify 

that the Pleistocene Hydrodamalis population was of 

larger average size than the Bering Island population of 

historic time, for the Amchitka specimen is immature, 

whereas the condition of the limb bones of the Bering 

Island collection indicates that almost all those specimens come from adults. Domning (1970, p. 219) advanced the idea that the 18th-century Bering Island 

population "was reduced to only about 2,000 animals 

living in marginal environment in the Bering Sea, their 

growth stunted so that they never reached the size of 

their Pliocene ancestors in more favorable habitat to 

the south."

A notable characteristic of Hydrodamalis, in contrast 

to all other Sirenia, is its lack of teeth. The anterior occluding surface of the rostrum and of the mandible (pi. 

2, all figs.; pi. 3, figs. 3, 4) was, as in all modern sirenians, deflected downward and flattened; it served as a 

grasping device (analogous to the toothless rostrum of 

ruminant Artiodactyla) with which the animal tore off 

the kelp on which it grazed. Steller (1899, p. 186) 

stated, on the basis of his dissection of a specimen of H. 

gigas, that mastication was done by "two strong white 

bones, or solid tooth masses, one of which is set in the 

palate and the other is fastened in the inferior maxilla, 

and corresponds to the first." These bones, Steller said 

(p. 186), were not fastened in the maxillae and mandibles, but were "held by many papillae and pores." The 

bones were said to be perforated below and to have 

many little holes (p. 186) "in which the arteries and 

nerves are inserted in the same way as in the teeth of 

other animals."

The "masticatory bones" to which Steller referred 

were undoubtedly horny plates, of cutaneous origin, 

covering the palate and the anterior part of the mandible. Brandt (1846, pi. Ill) illustrated some of these 

palatal coverings. These plates were certainly hard, and 

if they were white when dissected out, Steller may have 

mistaken them for bones.

Owen (1838, p. 41) said of the dugong, "the alveoli in 

the deflected portion of the lower jaw contained ligamentous processes given off from the internal surface 

of the thick callous integument covering that part of 

the jaw: they serve the purpose of fixing more firmly to 

the bone this dense and horny plate, which is beset externally with short coarse bristles, and is doubtless used 

in scraping and tearing off the seaweeds and other alimentary substances which may be fixed to the rocks."

The Amchitka mandibles are, in all major respects, 

identical with the modern ones from Bering Island.

The symphysis of the Amchitka mandible is about 25 

percent fused, evidence of the immaturity of the specimen, despite its large size. In profile, the anterior 

border of the mandible is bluntly rounded (pi. 2, figs. 1, 

2), in contrast to the pointed anterior profile of most 

Bering Island mandibles (pi. 2, figs. 3, 4).

The fossa for the genioglossus muscle (pi. 3, fig. 3; 

text-fig. 7) always large in Hydrodamalis, is especially 

large in the Amchitka mandible. This muscle functions 

in protrusion and retraction of the tongue.

The posterior border of the Amchitka mandible is 

thickened for 80 mm above the mandibular angle; at 

the angle ("d" in fig. 7 and table 2) it is 14 mm thick. It 

is thinner for 70 mm above the angle and thicker again 

(attaining a maximum thickness of 19 mm) for a distance of 80 mm on the uppermost part of the specimen 

as preserved (pi. 3, fig. 2; table 2). The preserved angular region of the right mandible is broken at the base of 

the ascending ramus. The posterior thickening of the 

angular region of the Amchitka specimen is in contrast 

to this region in adult Bering Island specimens. In the 

latter, the posterior border of the mandible thins almost 

to a knife edge ventrally and thickens only slightly at 

the angle. The posterior thickening of the jaw of the 

Amchitka specimen resembles more closely that in a 

young specimen from Bering Island (USNM 218381; table 2) and the Miocene genus Metaxytherium. By contrast another immature mandible from Bering Island 

(USNM 218401; table 2) has only slight thickening (9 

mm) at the angle and thus resembles adult mandibles 

in this respect. Many of the adult Bering Island specimens have a wrinkled surface on the posteromedial 

side of the ascending ramus (pi. 2, fig. 4). This contrast 

in configuration of the posterior edge of the mandible 

probably reflects differences in the areas of insertion of 

the medial pterygoid and masseter muscles. These mus-
10 STELLER'S SEA COW, AMCHITKA, ALEUTIAN ISLANDS, ALASKA

FIGURE 7. — Key to measurements of mandibles of Hydrodamalis. (See table 2.)

cles raise the jaw and have great power in keeping the 

jaws clenched. Despite the immaturity of the Amchitka 

specimen, the maximum thickness of its posterior mandibular border is greater than that of all but one Bering 

Island specimen (table 2).

The mental foramen is a prominent opening 10 mm 

high (pi. 2, fig. 1), situated 235 mm posterior to the anterior end of the mandible and approximately 50 mm 

anterior to the base of the ascending ramus. The base of 

the foramen is 63 mm above the ventral side of the 

mandible; its top is 31 mm below the dorsal side. The 

groove anterior to the mental foramen is about 65 mm 

long, widening gradually in an anterior direction. 

Because of breakage, the posterior extent of the mandibular canal cannot be determined exactly, but enough 

of the lateral wall of the mandibular foramen is present 

to show that its position and shape were approximately 

the same as that of the Bering Island specimens.

VERTEBRAE

Plate 3, figures 5-8; plate 4, figures 1 -8; table 3 

Only the centra of the last three cervical vertebrae 

and the first thoracic vertebra were found. They have 

the dorsoventrally flattened, subrectangular shape 

characteristic of the Sirenia. Daryl P. Domning (written commun., 1971) has suggested, on the basis of his 

studies of North Pacific sirenians, that there is a tendency for the width-to-height ratio of cervical centra to 

decrease in the course of their evolution. This trend is 

corroborated by comparison of the Amchitka specimen 

with Holocene specimens from Bering Island. Perhaps 

this trend can be correlated with increased lateral flexibility of the neck, associated with browsing in shallow 

water, as described by Steller.

Caution must be exercised, however, in drawing conclusions from measurements of cervical centra in Hydrodamalis, for the boundary between the centrum and
DESCRIPTION OF THE AMCHITKA HYDRODAMALIS 

TABLE 2. — Measurements, in millimeters, of mandibles of Hydrodamalis gigas

[See fig. 7 for key to measurements; leaders (...) indicate no measurement was made; entries followed by "e" indicate measurement is estimated]

11

Measurement

rr' ..............

ai .....

ab ..............

ad ..............

ef...............

df ..............

mo .............

on

Thickness

Maximum 

thickness of 

posterior 

border ....

Amchitka 

specimen

USNM

142

71 

167

436e 

361 

166

278 

90 

240

14 

19

Bering Island specimens (L. Stejneger colln., 1882 -83 '

CM

CM

160 

66 

149

418 

340 

157

241 

92 

209

16

16

o

SO 

CM

165 

62 

150

425 

349 

155

243 

76 

219

10 

10.7

CM 

SO 

CM

CM

148 

67 

148

410e 

345

167

250 

86 

223

8.3

17.3

SO 

SO 

CM

CM

144 

57 

122e

404 

340

120

264

82 

197

11 

12

01

SO 

CM

CM

139 

61

125

362 

345 

156

248 

90 

191e

11.4 

11.4

218371

145

72e 

123

428 

355 

163

263 

86

221

11 

14

218377

175 

68 

163

460 

385 

136

280 

91 

235

12 

12.8

00 

00

140 

44e

110

352

314 

127

236 

81 

200

13 

16.5

218399

143 

50

145

382 

312

127

222 

67 

206

218400

124 

55e 

100

380e 

285 

130

215 

82 

185

11 

13

o •*

00 

CM

167 

66 

166

419 

334

151

240 

89

215

9

14

218402

152

58

141

428 

354 

165

280 

95 

223

12 

12

218403

166 

62

155

430e 

380 

141

293 

92

217

10 

13.5

218408

175

60e

167

438 

363 

160

284 

82 

237

10.5

12

269064

191 

72

159

445 

374 

160

260 

103 

222

8 

20

Mounted 

composite 

skeleton, 

USNM

165 

64

173

428 

359 

135e

272 

81 

206

8

17

1 Numbers are from the Division of Mammals, U.S. National Museum of Natural History.

2 Young specimen: symphysis not completely fused MumliLT from U.S National Museum of Natural History. Department of Paleobiology. 

1 Note low symph\ sis.

the transverse process is poorly defined and probably 

varies in position with age.

In the sixth cervical vertebra, the lower half of the 

left transverse foramen is present (pi. 3, fig. 7). It is approximately 14 mm wide. Examination of specimens 

from Bering Island showed the size of the transverse 

foramen to be variable, even on two sides of the same 

individual. On the sixth cervical vertebra of USNM 

218808, an adult specimen from Bering Island (pi. 3, fig. 

8), the left transverse foramen is 11 mm wide, and the 

right is 14 mm wide. The posterior width of the centrum 

in this specimen is 135 mm, compared with 140 for the 

Amchitka specimen (table 3).

The seventh cervical vertebra of the Amchitka specimen has a small facet for rib articulation on its 

posterior face, on the ventral side of the base of the 

transverse process (pi. 4, fig. 3). The entire left 

transverse foramen is present (pi. 4, fig. 2); as in the 

Bering Island specimens, it is much smaller than the 

corresponding foramen in the sixth vertebra, being 5.5 

mm wide and 2.8 mm high. The first thoracic vertebra 

has both anterior and posterior demifacets for articulation of the capitulum of the ribs (pi. 4, fig. 6). The anterior demifacet is much smaller than the posterior one.

SCAPULA

Plate 5, figures 1-3; plate 6, figure 3; plate 7, figure 4; table 4

As in all Sirenia, the scapula of the Amchitka Hydrodamalis is fan-shaped — that is, very wide in its dorsal (vertebral) part and having a narrow neck just 

above the glenoid cavity. The result of these dimensions 

is that the prescapular and postscapular fossae, in 

which originate the muscles used in rotating the limb, 

are smaller than in most mammals. By contrast, the 

vertebral part of the scapula is wide, its posterior part 

being especially well developed.

The anterior border of the scapula in Hydrodamalis is 

almost straight, with a slight angulation about halfway 

up its height, in contrast to that of Metaxytherium and 

the modern Sirenia, which is strongly curved. The 

gently curved edge dorsal to the angulation in Hydrodamalis may be the anterior edge of the insertion of 

the serratus cervicis muscle.

The straight posterodorsal edge of the scapula (fig. 8, 

tmo) is the origin of the teres major muscle, which flexes the shoulder joint and abducts the arm. A branch of 

the serratus muscle was inserted on the costal side of 

the scapula medial to the teres major.

The prescapular fossa is small (fig. 8, ek; table 4), 

much smaller than in Metaxytherium (cf. Kellogg, 1966, 

pi. 43, figs. 1, 2) and somewhat smaller than in the 

modern Dugong dugon and Trichechus manatus. The 

postscapular fossa is of the same width as the prescapular (fig. 8).

The scapular spine in the Amchitka specimen is 

restricted to approximately the ventral half of the 

scapula (pi. 5, fig. 2; pi. 6, fig. 3). Spines in modern specimens from Bering Island occupy, on the average, 60
12 STELLER'S SEA COW, AMCHITKA, ALEUTIAN ISLANDS, ALASKA 

TABLE 3. — Measurements, in millimeters, of vertebrae of Hydrodamalis gigas

[USNM, U.S. National Museum of Natural History; UCMP, University of California, Museum of Paleontology; UCMP measurements by D. P. Domning; leaders (...) indicate that no measurement was made; entries followed by "e" indicate that measurement is estimated; an asterisk * indicates front and back reasurements respectively]

Bone measurement

Amchitka specimen

'USNM 170761

Bering Island specimens

2USNM 22182 2USNM 218807-218810 UCMP 23050 Mounted composite 

skeleton, USNM

Fifth cervical

Anteroposterior

thickness of

centrum ......... 42 31

Width of centrum .. "140/140 102/108 

Height of centrum at

middle .......... 78 71

Width/height of

centrum ........._____1.79__________ 1.43/1.52

Sixth cervical

Anteroposterior

thickness of

centrum ......... 41 36

Width ............. *130/140 *116/110

Height ............ 80 73

Width/height of

centrum .........____1.62/1.75_______ *1.59/1.50

Seventh cervical____

Anteroposterior

thickness of

centrum ......... 45 31

Width ............. *141/152 *109/110

Height ............ 78 75

Width/height of j

centrum ......... ; *1.80/1.94________1.45/1.46

First thoracic ____ ___

Anteroposterior

thickness of

centrum ......... 46

Width ............. *145/157

Height ............ 78/72

Width/height of

centrum .........____* 1.85/2.18

1 Department of Paleobiology, U.S. National Museum of Natural History.

2 Division of Mammals, U.S. National Museum of Natural History.

(USNM218807)

35

*118/118e

82

1.42

32

77e

lUSNM 2188081

43

*127/135 

86

"1.46/1.56

39e

120e

64e

1.89

(USNM 218809)

41e

*136/... 

83

1.63

*127/123 

66

"1.92/1.86

56e 

104e 

63e

1.63

(USNM218810)

59

*147/139 

74/85

"1.98/1.63

*119/123

74

1.60/1.64

58

104e

65e

1.60

percent of the scapular height. The lower half of the 

spine (acromion process) of the Amchitka specimen is 

expanded and heavy, much more so than in the Bering 

Island specimens. The tip of the acromion process has 

been broken off; in Holocene specimens from Bering Island (pi. 7, fig. 4) it is less well developed than in Metaxytherium (cf. Kellogg, 1966, pi. 43, figs. 1, 2).

The glenoid fossa and coracoid process are absent 

from the Amchitka specimen because the epiphyseal 

cartilage was not ossified.

The scapula of the Amchitka specimen is noticeably 

thicker and heavier, especially in the dorsal part of the 

blade (pi. 5, fig. 3), than are those in the Stejneger collection at the U.S. National Museum of Natural History. 

It is slightly narrower relative to its length than is any 

Bering Island specimen, but in length and width it is 

within the size range of that collection. In all Hydrodamalis specimens observed in this study, the 

scapula is heavier than in modern Sirenia.

HUMERUS

Plate 4, figures 9, 10; plate 6, figures 4, 5; plate 7, figure 1; plate 8, 

figure 1; table 4

The distal half of the right humerus of USNM 170761 

(pi. 6, figs. 4, 5) was found in a good state of preservation, although it lacks the distal articular surface 

because the epiphysis had not yet ossified. The left 

humerus was also present but had deteriorated to such 

an extent that no measurements or morphologic observations could be made. In addition, the right humerus of 

a smaller individual (USNM 186807; pi. 4, figs. 9, 10), 

collected at the foot of the cliff, has open eiphyses and 

lacks both proximal and distal articular facets. The anterior part of the proximal end of the bone is present, 

however, allowing measurement of the length of the 

shaft (245 mm). Although much smaller than USNM 

170761, this bone is as heavily constructed.

A prominent feature of the humerus of Hydrodamalis 

is the large shield-shaped deltoid tuberosity (pi. 7, fig.
DESCRIPTION OF THE AMCHITKA HYDRODAMALIS 13

FIGURE 8. — Key to measurements of scapula and humerus of Hydrodamalis.(See table 4.)

1). The part of the bone bearing the tuberosity is not 

present in USNM 170761; in the smaller humerus 

(USNM 186807), it is rounded and smaller relative to 

the size of the bone. This is probably due to the immaturity of the individual and possibly also to erosion of 

the specimen.

RADIUS AND ULNA

Plate 8, figures 2-6; text-figure 9

The forearm bones of both limbs were collected. 

Those of the right side are well preserved, whereas 

those of the left were soft and of soapy consistency. The 

left radius and ulna were collected in a plaster block 

and subsequently hardened with beeswax; however, 

they are so badly cracked that measurement was impractical. In all the bones, the epiphyses were open and 

the articular surfaces were missing.

In adult Holocene specimens from Bering Island (pi. 

8, fig. 6), the radius and ulna are strongly fused 

together at their proximal and distal ends and have 

scattered small areas of fusion in the middle part of 

their shafts. By contrast, the radius and ulna of the 

Amchitka specimen are separate, undoubtedly a function of the youth of the animal (pi. 8, fig. 5).

Near the proximal end of the anterior surface of the 

radius of the Amchitka specimen is a single tuberosity

(pi. 8, figs. 2, 5). In Dugong, such a tuberosity serves for 

insertion of the brachialis muscle (D. P. Domning, written commun., 1973). This tuberosity is double in some 

observed Holocene specimens from Bering Island (von 

Nordmann, 1863).

RIBS

Plate 5, figure 4; plate 6, figures 1, 2; text-figure 10

The rib fragments of USNM 170761 are from the anterior region of the thorax. Four pieces show characteristics worth recording. One is a fragment of the proximal end of an anterior rib (probably the first or second), proximally compressed (thickness about 18 mm) 

and expanding distally to an oval cross section, which 

measures 70 mm high by 40 mm wide at a distance of 

115 mm from the articular surface. The capitulum of 

this rib is preserved and consists of a small articular 

surface, spongy in appearance, as would be expected in 

a young specimen, and measuring 28 mm high by 15 

mm wide. The tuberculum has been broken off.

The second fragment is the capitulum of an anterior 

rib, probably the second or third of the left side. Its articular surface, also spongy (pi. 5, fig. 4), consists of two 

facets, intersecting at an angle of about 120°, that articulated with the demifacets of two of the thoracic vertebrae. The articular surface has a maximum height of
14 STELLER'S SEA COW, AMCHITKA, ALEUTIAN ISLANDS, ALASKA

TABLE 4. — Measurements, in millimeters, offorelimb of Hydrodamalis gigas

[See figs. 8 and 9 for key to measurements. Bering Island specimens having the same number are not necessarily from the same individual. USNM, U.S. National Museum of Natural History; 

Museum numbers of Bering Island specimens are assigned by USNM Division of Mammals; Museum numbers of Amchitka have been assigned by the USNM Department of Paleobiology; 

leaders (. . .) indicate that no measurement was made; entries followed by "e" indicate that measurement was estimated; (right) or (left) indicates side of skeleton]

Bone 

measurement

Scapula

ab .............

cd .............

ef ..............

ek .............

gh .............

bi ..............

bj ..............

kl ..............

tmo ............

jp ..............

Humerus

ef ..............

ij ..............

ab .............

Radius-ulna

ab .............

ag .............

cd .............

per

gh .............

ij ..............

mn ............ 

op .............

rt ..............

qr .............

st ..............

wx .............

Radius-ulna — 

Continued

ab .............

ag .............

cd .............

eg .............

gh .............

ij ..............

mn ............

op .............

rt ..............

qr .............

st ..............

wx .............

Amchitka specimens

USNM 170761 (left)

513 

338 

104 

60

143 3 75 

108e

110 

119 

200e 

250

USNM USNM 

170761 186807 

(right) (right)

183 130 

47 56 

245

USNM 170761 

(right) unfused 4

253

70 

121 

62 

65

72 

73 

103 

63

Bering Island specimens

USNM 269193 

(right) 1

481 

350 

120 

110

153 

77 

102

118

220 

183

USNM 35638 

(right)

225 

81 

534

USNM 21251 

(right) fused

517 

486 

372 

324

87 

158 

86 

76 

369

88e 

79e 

155e 

68

USNM 218394 

(right) ulna2

421 

345e

iS3e 

lOOe 

65e

USNM 218828 

(right)

570e 

412 

126

75

214 

125 

140

117 

146 

196 

240e

USNM 35638 

(left)

211 

131 

521

USNM 2 18380 

(right) ulna2

294 

250

'99 

'66

USNM 218414 

(left) fused 

proximal half4

151 

80 

73

95e 

139

USNM 35638 

(right) 2

574

414 

130 

120

203 

117 

139

133 

152 

221 

230

USNM 21251

(left)

214 

3 122 

545

USNM 218380 

(left) proximal 

half of ulna2

107 

65 

62

USNM 218415 

(left) radius

409

72 

63e 

145

57e

USNM 2 18409 

(left) 2

620 

430 

145

223 

112

177

139 

154 

198 

263

Mounted composite 

skeleton, USNM (right)

597 

424 

118 

117

195 

120e 

138

123 

197 

207 

291

Mounted composite skeleton, USNM

(left)

207 

113 

489

USNM 2 18371 

(right) partial ulna

144 

91

72

USNM 218415 

(right) radius

344

73 

81 

139 

73

(right)

185 

102 

454

USNM 2 18393 

(left) fused

517 

374

62 

159 

99 

93

(?)

92e 

91e 

159 

69e

Mounted composite 

skeleton, USNM 

(left) fused

506 

604 

603 

316

150 

149 

95 

79e 

363

77e 

49 

50 

73

1 Suprascapular cartilage ossified. 

* Immature, but epiphyses attached.

! Eroded.

1 Epiphyses missing; measurement less than original length of bone.

55 mm and width of 39 mm. The surviving proximal 

part of the rib shaft is extremely compressed, being 15 

mm thick by approximately 80 mm wide.

The other two rib fragments lack the proximal and 

distal ends. They do not match the broken ends of the

two fragments just described. One has a slight angulation in the form of a low ridge on its convex side; the 

very gentle curvature of this bone indicates that it is 

the second or third rib, although it is heavier than such 

ribs in the Stejneger collection from Bering Island. It is
DESCRIPTION OF THE AMCHITKA HYDRODAMALIS 15

FIGURE 9. — Key to measurements of radius and ulna of Hydrodamalis. (See table 4.)

from the right side. The fragment is 170 mm long, 76 

mm wide at the angulation, its widest (mesolateral) 

dimension, and 50 mm thick anteroposteriorly at the 

same point. The smaller (ventral) end of the rib fragment presents a spongy appearance, indicating that it 

was near the true end of the bone, where there was a 

cartilaginous connection with the sternum. At this 

point the rib is tapering rapidly, having a diameter of 

50 mm mesolaterally and 39 mm anteroposteriorly.

The other fragment is probably from the dorsal part 

of the third rib of the left side. It is more gently curved 

and heavier than the first fragments and is 150 mm 

long. At its proximal end, its cross section has the shape 

of a triangle with rounded angles; the apex points anteriorly. From base to apex, it measures 60 mm; the 

length of the base is 65 mm. The distal end of the fragment is oval in cross section. It measures 48 mm anteroposteriorly and approximately 60 mm 

mesolaterally.

A more nearly complete rib fragment (USNM 

181752; pi. 6, fig. 1; text-fig. 10) the distal two thirds of 

approximately the twelfth rib of the left side, was found 

in place 0.1 m above the base of the deposit 15 m above 

the beach and about 9 m stratigraphically below the 

level at which the Hydrodamalis skeleton was found. 

The bone is heavily oxidized, reddish brown, and was 

very brittle when collected, in contrast to the white color and hardness of bones found near the surface at the 

top of the cliff (fig. 6). The rib is evenly curved, having 

been broken distal to the angulation (fig. 10). It is ovoid 

in cross section; the greatest thickness is anteroposterior. Cross-section measurements are as 

follows (fig. 10): No. 1, 98x49 mm; No. 2, 84x56 mm; No.

3, 80x57 mm; No. 4, 72x52 mm; No. 5, 62x50 mm. The 

distal end of the rib has a relatively smooth area running anteroposteriorly and a coarsely pitted area on 

either side of it. In cross section, where broken at its 

proximal end, the rib has cancellous tissue in its outer 

posterior quarter; the rest of the cross section shows 

pachyostotic bone. This rib is within the size range of 

modern ribs from Bering Island.

The rib from the Kangiguksuk archeological site 

(Yale Peabody Mus. No. 233862) is an anterior rib from 

the left side. The sawed distal end shows it to be 

pachyostotic except for an area of cancellous bone that 

runs mediolaterally through the middle of the bone. 

Such presence of cancellous tissue is typical of young 

Sirenia; in adult animals the bone is fully pachyostotic, 

and there is no trace of cancellous tissue.

The distal end of the rib has been sawed off; as 

preserved, the specimen measures 582 mm along the 

outside curve. At the sawed distal end it is suboval, 

being slightly narrower at the outer than at the inner 

side. In cross section it measures 52 mm transversely 

and 33 mm anteroposteriorly. At the outer extremity of 

the curve (approximately at the position of cross-section 3 of fig. 10), the rib measures 46.5 mm transversely 

and 37 mm anteroposteriorly. At the proximal end of 

the curve, immediately distal to the tuberculum, it 

measures 43 mm transversely and 36 mm anteroposteriorly, having been reduced slightly in circumference to form the neck of the rib. The proximal end of 

the rib, in the area of the capitulum and tuberculum, is 

anteroposteriorly compressed and gently curved, being 

concave anteriorly and convex posteriorly. The distance 

from capitulum to tuberculum is 101 mm; midway in
16 STELLER'S SEA COW, AMCHITKA, ALEUTIAN ISLANDS, ALASKA

FIGURE 10. — Rib of Hydrodamalis (USNM 181752) from base of 

South Bight II interglacial beach deposit, Amchitka Island. (See 

also fig. 6.)

this distance, the rib is 21 mm thick anteroposteriorly 

and 45 mm dorsoventrally. The capitular articulation is 

very small, 17 mm dorsoventrally by 18 mm anteroposteriorly. This end of the rib has been worked or 

gnawed (it is marked by many dorsoventral scratches); 

probably, the capitulum originally had a somewhat 

larger articular area. The tuberculum is a low anteroposteriorly compressed ridge.

The Kangiguksuk rib appears to come from a more 

lightly built animal (possibly because of its youth) than 

those represented on Bering Island.

CHEVRON BONE

Half a chevron bone, probably from the right side of 

the animal, was recovered (pi. 7, figs. 2, 3). The chevron 

bone, named from its shape in cross section, forms the 

hemal arch below the centra of the caudal vertebrae. 

Through the V of the hemal arch run the major blood 

vessels of the tail. There are no chevron bones of Hydrodamalis in the collections of the U.S. National 

Museum, but hemal arches of Holocene Dugong, a member of the same family as Hydrodamalis (Dugongidae 

Gray, 1821), are for the most part composed of paired, 

separate bones in contrast to the condition in the 

Cetacea, whose hemal arches almost invariably consist 

of a V-shaped bone, resulting from fusion of the bones of 

the two sides.

The chevron bone of Hydrodamalis from Amchitka 

measures 66 mm in greatest vertical dimension, 42.5 

mm anteroposteriorly on its dorsal side, and 36.5 mm 

anteroposteriorly at the level where it starts to taper 

ventrally to a rounded posteriorly slanting edge. The 

size of the bone indicates that it was associated with 

one of the posterior caudal vertebrae.

MORPHOLOGIC CONCLUSIONS

The Amchitka skeleton shows no significant 

morphologic differences from 18th-century specimens 

from Bering Island. Its mandible is larger than would 

be expected in the Bering Island population, especially 

when one considers that it was immature at death; the 

other Amchitka bones, however, are farther down in 

the size range of the Bering Island collection. This disparity in ratio between mandible size and dimensions of 

postcranial bones may be because of the youth of the 

Amchitka specimen, or it may be because the 

Pleistocene Hydrodamalis had a larger head relative to 

the body than did members of the 18th-century Bering 

Island population. D. P. Domning (written commun., 

1973) has pointed out that in the transition from Metaxytherium to Hydrodamalis, body size increased perhaps 

100 percent, and skull length, only about 40 percent. 

Ratios between mandible size and that of postcranial 

bones in the Bering Island population of Hydrodamalis
DESCRIPTION OF THE AMCHITKA HYDRODAMALIS 17

(U.S. National Museum collection) are of questionable 

significance because the collection consists of bones 

picked up at random; it does not include any associations of bones from one individual.

The only description known to us of a skeleton of a 

single individual of H. gigas from Bering Island was 

published by von Nordmann (1863). This skeleton, in 

the zoological museum at Helsinki, Finland, is that of an 

immature animal, which facilitates comparison with 

the Amchitka specimen (table 5). In von Nordmann's 

specimen, the epiphyses of the scapulae, the humerus, 

the ulna, and the radius had been lost, being separate 

from the shafts of the bones. The skeleton is 5 m long, 

as compared with an estimated length of 7.6 m for an 

adult Bering Island specimen. Von Nordmann's specimen and that from Amchitka appear to have been near 

enough to the same ontogenetic age that comparisons 

between them will have some validity; caution is dictated, however, because the size of the adult Pleistocene 

Hydrodamalis is unknown.

As an index of the relation of head size to body size, 

ratios were established between the length of the jaw 

and various measurements of postcranial bones in the 

von Nordmann and Amchitka specimens (table 5). In 

many of these ratios no significant difference exists between the two specimens; where a difference does exist, 

the postcranial measurement is smaller relative to jaw 

length in the Amchitka specimen than in that 

described by von Nordmann. This relationship fits 

Domning's hypothesis that body size increased relative 

to head size in the evolution of the Metaxytherium-Hydrodamalis line.

The jaw described by von Nordmann is much shorter 

than the Amchitka jaw and shorter than the mean of 

jaws from Bering Island. It is also smaller in other 

dimensions than are the Bering Island jaws, the exception being the width of the symphysis, in which it 

measures 65 mm compared with a mean of 61 mm for 

the Bering Island specimens. With three exceptions, 

the postcranial bones of the von Nordmann specimen 

are smaller than the mean for the Bering Island bones. 

The exceptions are the thickness of the humerus at its 

lower end and the diameter of the lower ends of the 

radius and ulna. The small size of these measurements 

of the Bering Island specimens may result from erosion 

of the ends of the limb bones, which is evident upon inspection. However, no such cause can account for the 

fact that, in these measurements, the von Nordmann 

specimen is larger than the Amchitka specimen, in 

which the bones concerned are well preserved.

The specimen described by von Nordmann has a 

larger jaw relative to postcranial bones than do the 

specimens in the mixed collection from Bering Island, 

on the basis of mean measurements of bones. In this

TABLE 5. — Comparison of measurements of the Amchitka specimen of 

Hydrodamalis gigas with measurements of an immature specimen 

from Bering Island, measured by von Nordmann (1863)

[Measurements given in millimeters, "e" following value indicates estimated]

Amchitka 

specimen

von Nordmann 

specimen

First thoracic vertebra:

Length of body at base ............. 46 41

Height of body ..................... 78 71

Greatest width of vertebral foramen . 126e 106

Scapula:

Length from end of collum to middle of

upper border .................... 513 455

Greatest width of upper part........ 338 377

Width of neck at border of epiphysis 143 152 

Thickness of neck in middle ........ 104 85

Greatest height of spine ............ 67 75

Humerus:

Greatest width, lower end .......... 183 177

Greatest width in middle ........... 86 98

Greatest thickness at lower end ..... 61 82

Greatest thickness in the middle .... Ill 102

Ulna:

Length of bone without epiphysis.... 320 320

Greatest width of upper end ........ 121 112

Greatest diameter in middle ........ 60 62

Greatest diameter of lower end ..... 71 78

Radius:

Length of bone without epiphysis .... 265 280

Greatest width of upper end ........ I05e 113

Greatest diameter in middle ........ 57 65

Greatest diameter of lower end ..... 66 81

Jaw:

Length from most posterior border of

angle to point of symphysis ....... 395 374

Greatest height of body of jaw at

posterior border of foramen maxillare [= mental foramen] ......... 92 84

Grestest height of body of jaw in front

of foramen maxillare ............. 144 140

Length of symphysis of both jaw

halves........................... 143 146

Greatest width of symphysis ........ 71 65

Ratios:

Jaw length /length, first thoracic vertebra ........................... 8.58 9.12

Jaw length/height, first thoracic vertebra ........................... 5.06 5.26

Jaw length/scapula length .......... .77 .80

Jaw length/scapula width .......... 1.13 .99

Jaw length/width of humerus, lower 

end ............................. 2.15 2.11

Jaw length/width of humerus in middle .............................. 4.59 3.81

Jaw length/humerus: greatest thickness, lower end .................. 6.47 4.56

Jaw length/humerus: greatest thickness in middle ................... 3.55 3.67

Jaw length/ulna: width of upper end 3.26 3.33 

Jaw length/ulna length ............. 1.23 1.16

Jaw length/ulna: diameter of lower 

end ............................. 5.56 4.79

Jaw length/radius length ........... 1.49 1.33

characteristic, the von Nordmann specimen resembles 

the Amchitka specimen. The allometry shown by these 

two animals is probably due in part to their youth. The 

large size of the Amchitka jaw, however, may indicate,
18 STELLER'S SEA COW, AMCHITKA, ALEUTIAN ISLANDS, ALASKA

in addition, that the population from which it came consisted of larger individuals than those constituting the 

18th-century population on Bering Island.

The larger size of the Amchitka animal indicates 

that size reduction took place during Pleistocene time 

within the species H. gigas.

One vexing problem of the anatomy of Hydrodamalis 

was unfortunately not solved by the Amchitka find. 

This problem is the morphology of the wrist and manus. 

Steller (1899, p. 188) described the anterior extremity 

of Hydrodamalis as terminating "bluntly with tarsus 

and metatarsus [sic]. There are no traces of fingers, nor 

are there any of nails or hoofs; but the tarsus and 

metatarsus are covered with solid fat, many tendons 

and ligaments, cutis and cuticle, as an amputated 

human limb is covered with skin. But both the cutis, 

and especially the cuticle, are much thicker, harder, 

and drier there, and so the ends of the arms are something like claws, or rather like a horse's hoof; but a 

horse's hoof is sharper and more pointed, and so better 

suited to digging." No carpal bones of Hydrodamalis 

have been identified. The skeleton mounted in the 

Naturhistoriska Riksmuseet in Stockholm (pi. 1) has a 

bone mounted in the position of a metacarpal, which 

Domning (in press) has identified as the transverse 

process of a vertebra.

DISCUSSION

Hydrodamalis gigas, approximately 127,000 years 

ago, was established on Amchitka Island and was 

characterized by the same large size and lack of teeth 

that distinguished the population that became extinct 

on Bering Island in the 18th century. Remains of three 

individuals were found within a few hundred meters in 

the cliffs at South Bight on Amchitka. The South Bight 

exposure, preserved in a graben bordered and protected 

by early Tertiary rocks, is a rare occurrence of late 

Pleistocene interglacial deposits in the Aleutians; the 

abundance of Hydrodamalis gigas in this limited exposure suggests that the species may have been widely 

distributed in the Aleutians at that time. A former wide 

distribution of Hydrodamalis is supported by other, 

although scanty, paleontologic evidence — the occurrence of (1) a skull in Monterey Bay, Calif. (Jones, 

1967); (2) representatives of the genus in the Pliocene 

of California (Domning, in press); (3) a rib in the 

Pliocene of Japan (Shikama and Domning, 1970); and 

(4) a rib in an archeological site in northwestern 

Alaska (Hall, 1971). Further evidence pointing to a lowlatitude origin of Hydrodamalis is the distribution of 

fossil as well as modern Sirenia.

The presence of Hydrodamalis in the Pliocene and 

Pleistocene of California emphasizes the question of 

how the genus, unlike any other representatives of its 

order, achieved adaptation to life in cold water. Probably this adaptation began in California latitudes; 

Durham (1950) pointed out that by middle Pliocene 

time the 20°C marine isotherm, as a result of a cooling 

trend, had approached its present position near the 

southern tip of Baja California. Addicott (1969) 

analyzed the distribution patterns of Tertiary shallowwater molluscan faunas and, although detecting a middle Miocene warming trend, corroborated a decline in 

the temperature of California coastal water in later 

Miocene and Pliocene time. Turning to Pleistocene temperatures of the California coast, D. M. Hopkins (written commun., 1972) stated that subarctic mollusk 

faunas have been collected from the floor of Monterey 

Bay, "containing, most notably, Astarte benneti, a 

shallow-water mollusk that now ranges from Puget 

Sound to Point Barrow." As Hopkins pointed out, 

however, we do not know whether the Arctic mollusks 

are of the same age as the dredged Hydrodamalis skull 

from Monterey Bay.

It seems certain that the Commander Islands must 

have had a Quaternary history similar to that of the 

Aleutians and that Hydrodamalis once ranged along 

the Aleutian chain as well. Whether the sea cow lived in 

the Aleutians in Holocene time is, however, unknown. 

If Hydrodamalis lived throughout the Aleutians in 

Holocene time, its presence may have provided incentive for a rapid westward migration of the Aleut, who, 

like the Russians, would have found that these animals 

were easily caught and were excellent food. This 

speculation is supported by Martin's (1973) intriguing 

proposal of a spectacularly rapid advance of hunting 

man throughout the Western Hemisphere 11,500 to 

10,500 years ago. The Aleuts' westward expansion 

could account for the disappearance of these animals 

from the Aleutian Islands (Domning, 1972, p. 188). The 

Aleuts never reached the Commander Islands 

(Laughlin, 1967, p. 444), and Hydrodamalis survived 

there until the 18th century. That bones of Hydrodamalis have not been found in Aleut middens may 

be because not enough middens in the Aleutians have 

been excavated, or perhaps because the bones simply 

have not been recognized; or it may be that the middens 

that have been explored postdate the extinction of Hydrodamalis in the Aleutians. Aleuts were present on 

Umnak as much as 8,000 years ago (Laughlin, 1967), 

and, as Domning speculates, middens where the bones 

might be found are now mainly below sea level.

The presence of Hydrodamalis in the late Pleistocene 

of Amchitka suggests, despite the presence of icecaps 

on some, if not all, of the Aleutian Islands, that the 

water temperature continued to be warm enough during Wisconsinan time to support kelp (which is presently the predominant plant element of Arctic and Antarctic seas, according to Smith, 1938, p. 220) and, in 

turn, to support the sea cow.
STELLER'S SEA COW, AMCHITKA, ALEUTIAN ISLANDS, ALASKA

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19

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PLATES 1-8

[Contact photographs of the plates in this report are available, at cost, from the VS. Geological Survey Photographic Library, 

Box 25046, Denver Federal Center, Denver, Colorado 80225]
PLATE 1

Mounted skeleton of Hydrodamalis gigas, Naturhistoriska Riksmuseet, Stockholm, Sweden. The 

bone mounted as a metacarpal on the right forelimb is actually the transverse process of a vertebra (Domning, in press). Photograph furnished by the Naturhistoriska Riksmuseet, 

Stockholm, Sweden.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1036 PLATE 1

HYDRODAMALIS GIG AS (ZIMMERMANN)
PLATE 2

FIGURES 1—4. Hydrodamalis gigas.

1. Left mandible of Amchitka specimen, USNM 170761. Lateral view, x 0.33.

2. Same. Medial view, x 0.33.

3. Left mandible of Bering Island specimen, USNM 21260. Lateral view, x 0.35.

4. Same. Medial view, x 0.35.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1036 PLATE 2

HYDRODAMALIS GIGAS (ZIMMERMANN)
PLATE 3

FIGURES 1—8. Hydrodamalis gigas.

1. Posterior part of right mandible of Amchitka specimen, USNM 170761. 

Medial view, x 0.33.

2. Same. Posterior view, x 0.35.

3. Mandible of Amchitka specimen, USNM 170761. Occlusal view, x 0.38.

4. Mandible of Bering Island specimen, USNM 21262. Occlusal view, x 0.38.

5. Fifth cervical vertebra of Bering Island specimen, USNM 218807. Posterior 

view, x 0.33.

6. Fifth cervical vertebra of Amchitka specimen, USNM 170761. Anterior view, 

x 0.34.

7. Sixth cervical vertebra of Amchitka specimen, USNM 170761. Anterior view, 

x 0.36.

8. Sixth cervical vertebra of Bering Island specimen, USNM 218808. Anterior 

view, x 0.34.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1036 PLATE 3

HYDRODAMALIS GIG AS (ZIMMERMANN)
PLATE 4

FIGURES 1-10. Hydrodamalis gigas.

1. Sixth cervical vertebra of Amchitka specimen, USNM 170761. Right-lateral 

view, x 0.34.

2. Seventh cervical vertebra of Amchitka specimen, USNM 170761. Anterior 

view, x 0.4.

3. Same. Left-lateral view, x 0.37.

4. Seventh cervical vertebra of Bering Island specimen, USNM 218809. Anterior 

view, x 0.34.

5. First thoracic vertebra of Amchitka specimen, USNM 170761. Anterior view, 

x 0.34.

6. Same. Left-lateral view, x 0.32.

7. First thoracic vertebra of Bering Island specimen, USNM 218810. Anterior 

view, x 0.34.

8. Same. Left-lateral view, x 0.36.

9. Right humerus of Amchitka specimen, USNM 186807. Posterior view, x 0.32. 

10. Same. Anterior view, x 0.32.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1036 PLATE 4

.. * (..

HYDRODAMALIS GIG AS (ZIMMERMANN)
PLATE 5

FIGURES 1—4. Hydrodamalis gigas.

1. Left scapula of Amchitka specimen, USNM 170761. Lateral view, x 0.35.

2. Same. Anterior view, x 0.30.

3. Same. Dorsal view, x 0.39.

4. Proximal end of left anterior rib of Amchitka specimen, USNM 170761. 

Posterior view, x 1.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1036 PLATE 5

HYDRODAMALIS GIGAS (ZIMMERMANN)
PLATE 6

FIGURES 1—5. Hydrodamalis gigas.

1. Distal part, approximately twelfth rib of left side, Amchitka specimen, USNM 

181752. Posterior view, x 0.28.

2. Approximately twelfth rib of left side, Bering Island specimen, USNM 35638. 

Posterior view, x 0.19.

3. Left scapula of Amchitka specimen, USNM 170761. Medial view, x 0.36.

4. Distal half of right humerus, Amchitka specimen, USNM 170761. Anterior 

view, x 0.34.

5. Same. Posterior view, x 0.34.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1036 PLATE 6

HYDRODAMALIS GIG AS (ZIMMERMANN)
PLATE 7

FIGURES 1-4. Hydrodamalis gigas.

1. Right humerus of Bering Island specimen, USNM 35638. Anterior view, 

x 0.30.

2. Chevron bone of Amchitka specimen, USNM 170761. Anterior view, x 1.

3. Same. Medial view, x 1.

4. Right scapula of Bering Island specimen, USNM 35638. Lateral view, x 0.30.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1036 PLATE 7

HYDRODAMALIS GIGAS (ZIMMERMANN)
PLATE 8

FIGURES 1-6. Hydrodamalis gigas.

1. Right humerus of Bering Island specimen, USNM 35638. Posterior view, 

x 0.27.

2. Right radius of Amchitka specimen, USNM 170761. Lateral view X 0.30.

3. Right ulna of Amchitka specimen, USNM 170761. Anterolateral view, x 0.30.

4. Same. Posterior view, x 0.30.

5. Right radius and ulna of Amchitka specimen, USNM 170761. Lateral view, 

x 0.30.

6. Right radius and ulna of Bering Island specimen, USNM 21251. Lateral view, 

x 0.32.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1036 PLATE 8

HYDRODAMALIS GIGAS (ZIMMERMANN)

Government Printing Office: 1977-777-034/5