Evolution of the Rails

of the South Atlantic Islands

(Aves: Rallidae)

STORRS L. OLSO

i

t

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY • NUMBER 152
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SMITHSONIA N CONTRIBUTION S T O ZOOLOG Y • NUMBE R 15 2

Evolution of the Rails

of the South Atlantic Islands

(Aves: Rallidae)

Storrs L. Olson

SMITHSONIAN INSTITUTION PRESS

City of Washington

1973
ABSTRACT

Olson, Storrs L. Evolution of the Rails of the South Atlantic Islands (Aves:

Rallidae). Smithsonian Contributions to Zoology, number 152, 53 pages, 8 figures, 11 plates, 1973.—Abundant remains of a medium-sized, flightless rail collected on Ascension Island are described as a new species, Atlantisia elpenor.

The very large, extinct, flightless rail, previously described as Aphanocrex podarces, is also shown to be a member of the genus Atlantisia, the only other

member of which is the diminutive, flightless, living species A. rogersi of Inaccessible Island in the Tristan da Cunha group. These three species are believed

to be descended from a common mainland ancestor of a pro-Rallus stock that

arrived as wind-blown vagrants to all three islands where each population independently evolved Sightlessness and divergent body sizes in response to different

environmental conditions. Bones of a flightless rail much smaller than A. podarces were also discovered on St. Helena and represent a new species, Porzana

astrictocarpus, which, along with the flightless species "Porzanula" palmeri of

Laysan Island in the Pacific, is thought to be descended from the widespread

Old World species Porzana pusilla. The two nearly identical flightless gallinules

of Tristan da Cunha (nesintis) and Gough (comeri) Islands are considered as

each having been independently derived from volant Gallinula chloropus and

are, therefore, best treated as separate species or as subspecies of G. chloropus

rather than one being a subspecies of the other. Two species of purple gallinules (Porphyrula) are regular vagrants to the South Atlantic islands yet have

never established breeding populations on any of them. This genus is thought

to be too specialized morphologically to adapt to insular environments. Flightlessness in rails is shown to be a neotenic condition that involves only the control of relative growth of body parts, is evolved at a rapid rate, .arid therefore

has limited taxonomic significance. The evolutionary advantage of Sightlessness

is thought to be in the conservation of energy resulting from the decrease in

mass of the flight muscles.

OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is

recorded in the Institution's annual report, Smithsonian Year. SI PRESS NUMBER 4818. SERIES

COVER DESIGN: The coral Montastrea cavernosa (Linnaeus).

Library of Congress Cataloging in Publication Data

Olson. Storrs L.. 1944-

Evolution of the rails of the South Atlantic islands (Aves: Rallidae).

(Smithsonian contributions to zoology, no. 1~>2) Bibliography: p.

1. Rails (Birds) 2. Birds—Evolution. 3. Birds—South Atlantic Ocean. 4. Birds—Islands of

the Atlantic. I. Title. II. Series: Smithsonian Institution. Smithsonian contributions to

zoology, no. 152.

QL1.S54 no. 152 [QL696.G8] 591'.u8s [598.3'1] 73-2859

For sale by the Superintendent of Documents, U.S. Govennent Printing Office, Washington, D.C. 20402

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Contents

Page

Introduction 1

Acknowledgments 2

Rails of Ascension Island 3

History of the Endemic Ascension Rail . 3

Atlantisia elpenor, new species 7

Environment and Extinction of the Ascension Rail 10

Vagrant Rallids . 12

Rails of St. Helena 13

Redescription and Relationships of "Aphanocrex" podarces 13

A Second Species of Extinct Rail 16

Porzana astrictocarpus, new species 17

Extant Rails 20

The Resident Gallinula 20

Errant Species of Porphyrula 21

Environment and Lives of the Rails 21

Rails of the Tristan da Cunha Group and Gough Island 23

Origin and Evolution of the South Atlantic Rails 25

Genus Porphyrula 25

Genus Gallinula 27

Genus Atlantisia 28

Genus Porzana . 29

Evolution of Flightlessness in Rails . 31

Concluding Remarks 36

Literature Cited 37

Appendix 1: Comparative Material Examined 41

Appendix 2: Characterization of the Genus Atlantisia 41

Plates 1-11 43

Evolution of the Rails

of the South Atlantic Islands

(Aves: Rallidae)

Storrs L. Olson

INTRODUCTION

Among the families of terrestrial vertebrates, the

rails (Rallidae) have one of the most comprehensive geographical distributions. Not only are

they widespread in continental areas, except in regions of extreme cold or aridity, but practically no

island or group of islands is too remote or inhospitable to have been discovered and inhabited by

some species of rallid.

The islands of the mid-South Atlantic are among

the smallest and most isolated in the world; yet as

it has turned out, each harbored one or more species of rail. Ascension, St. Helena, and the Tristan

da Cunha group, remote from each other as they

are, have been occupied by one group of these

rails which has radiated almost as if it were in an

archipelago. In these solitary microcosms has unfolded an evolutionary story in its own way as fascinating as that of the Galapagos or Hawaii.

The islands with which we will be concerned

are entirely volcanic and are part of the MidAtlantic Ridge. Ascension and Tristan lie directly on the ridge and both are geologically very

young. St. Helena lies to the east of the center of

the ridge and is considerably older (Baker, 1970).

The map (Figure 1) demonstrates how far reStorrs L. Olson, Department of Vertebrate Zoology, National

Museum of Natural History, Smithsonian Institution, Washington, D.C. 20560.

moved these islands are from each other and from

the continents.

Ascension was discovered in 1501, St. Helena in

1502, and Tristan da Cunha in 1506. St. Helena,

being of good climate and rich in resources, was

AFRICA;

FIGURE 1.—Map of the South Atlantic Ocean showing the

principal islands. Numbers represent distances in kilometers

and were computed by F. C. W. Olson from coordinates

obtained from the World Port Index (Publication 150, U.S.

Navy Oceanographic Office, 1963). Arrows indicate direction

of prevailing surface winds.
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

settled not long after its discovery. Because of its

barren nature, Ascension was not permanently inhabited until 1815. The Tristan group, composed

of the main island of Tristan da Cunha, the two

smaller adjacent islands of Inaccessible and Nightingale, and Gough Island considerably to the

south, was not settled permanently until 1810, and

then only the main island of Tristan was occupied; the rest to this day remain uninhabited. As

a consequence of man's interference, a number of

species of birds from these islands have become extinct and, of these, most are known only from

bones. In search of fossil bird remains, I made

collections on Ascension Island (12 June-15 July

1970, 1 June-4 June, and 19 July-31 July 1971)

and on St. Helena (5 June-17 July 1971). These

collections include, in addition to thousands of

specimens of seabirds and a few other landbirds,

three species of rails, two of which are described

here as new. The bulk of this paper will concern

itself with the origins, relationships, descriptions,

ecology, and adaptations of the living and fossil

rails of the South Atlantic Islands. The most striking modification of most of these species is their

flightlessness. This is a condition that appears

often in insular rails, yet one that has received

little analysis. The origins, advantages, and significance of flightlessness in the Rallidae are also

treated here.

ACKNOWLEDGMENTS.—I need first single out the

constant assistance and advice of George E. Watson, who has helped me from the inception of this

project in ways too many to enumerate; my debt

to him is great indeed.

Funding for travel was provided by the Smithsonian Institution, Departments of Vertebrate

Zoology (G. E. Watson), Invertebrate Zoology (R.

B. Manning), and Office of Systematics (R. S.

Cowan). Helena Weiss, Hazel Fermino, and Francine Berkowitz took care of difficult travel arrangements. J. P. Angle, T. S. Bober, E. N. Gramblin,

F. M. Greenwell, W. P. Haynes, and G. R. Shaver

provided for the assembling and shipping of supplies and equipment.

Travel and accomodations to Ascension in both

years, were effected through the fine cooperation of

the United States Air Force, especially Philip F.

Hilbert, Deputy Under Secretary (International

Affairs) and Major General David Jones, Commander, USAF Eastern Test Range, who responded

to inquiries by Sidney R. Galler of the Smithsonian. Major Jesse M. Couch, Base Commander

Ascension AAF, repeatedly gave more than generously of his time and effort to contribute to the

success of my undertakings.

To H. E. Sir Dermod Murphy, Governor of St.

Helena; H. E. Ian Rose, Government Secretary

and Acting Governor of St. Helena; Brigadier H.

W. McDonald, Administrator of Ascension Island;

and Mr. Jeff Appleby, Chief of Police and Acting

Administrator of Ascension Island, I am indebted

for permission to conduct scientific studies on their

islands and for many other courtesies as well. Douglas S. Rogers, then Curator of the Ascension Historical Society Museum, contributed his invaluable

island lore and enthusiastically aided in the collection of specimens. Dave Gallop, Peter Critchley,

John Taylor, Kay, John, and Michael Hutchfield,

Danny Nickerson, Ray Futrell, George Taylor,

Gil Hermans, and Carl Coggins were among those

on Ascension who helped in so many ways. On St.

Helena, Mr. and Mrs. A. H. Mawson, William

Stopforth, Joyce Wade, and Milly Thomas provided superb accomodations and encouragement.

My first two years of research were undertaken

while holding scholarships as a graduate student

in the Department of Pathobiology, Johns Hopkins

University, School of Hygiene and Public Health.

I am most grateful to Frederik B. Bang for providing this opportunity and for his considerable personal and administrative support. Barreda Howell

continually and patiently helped me through administrative crises, large and small, during my

tenure at Hopkins. My last year of graduate study

was financed by a visiting research fellowship from

the Office of Academic Studies of the Smithsonian

Institution, during which period Gretchen Gayle

and Hazel Fermino helped with a multitude of

details.

Dean Amadon, American Museum of Natural

History (AMNH); D. W. Snow, British Museum

(Natural History) (BMNH); R. W. Storer, University

of Michigan Museum of Zoology (UMMZ); R. A.

Paynter, Jr., Museum of Comparative Zoology

(MCZ); A. R. McEvey, National Museum of Victoria (NMV); and Pierce Brodkorb, University of

Florida, loaned comparative material in their care.

The collections of the National Museum of Natural History, Smithsonian Institution (USNM) were

a major source for my research, in which connec-
NUMBER 152

tion R. L. Zusi has often rendered his aid.

Genevieve Tvrdik and Ned K. Johnson supplied

information on specimens of Tribonyx in the Museum of Vertebrate Zoology.

Sheila Ford generously executed Plates lc, Id,

and Si. The patience, care, and dispatch exercised

by Victor E. Krantz in taking and printing the

photographs is very much appreciated. N. Drahos

and I. Ikehara kindly supplied me with specimens

of the Guam rail. The late James A. Peters assisted in making calculations on time-share computer. In the course of my work I have benefited

from discussions with R. L. Zusi, A. Wetmore, G.

E. Watson, P. Slud, K. C. Parkes, R. B. Manning,

P. Brodkorb, and N. P. Ashmole. This paper

was submitted in partial fulfilment of the degree

of Doctor of Science at the Johns Hopkins University and the members of my committee, F. B. Bang,

J. T. Fales, E. Gould, W. J. L. Sladen, and G. E.

Watson, read and commented on the manuscript.

Finally, Hazel Fermino spent many long, late hours

typing the final draft.

RAILS OF ASCENSION ISLAND

History of the Endemic Ascension Rail

The 7th June anno 1656. Att evening wee arrived att

Ascention and anchored on the NW. side of the iland. On

our rightt hand was a faire sandy bay and on our leftt

were multi[tu]de of rarreg [ragged], craggy, sharpe pointed

hard rocks for many miles along the shoare, and up toward

the land, appearing white with the dung of sea foule, of

which were innumerable of severall kinds. The most desolate, barren [land] (and like a land thatt God had cursed)

thatt ever my eies beeheld (worse then Kerne Ky, etts. in

Cornewall). I co[n]ceave the whole world affoards nott

such another peece of ground: most part of the collour of

burnt bricke, reddish, the substance stones, somwhatt like

pumice stones; the rest like cinders and burnt earth. The

hills, of which there are many, were meere heapes of the

same. It may bee supposed thatt the fire in former ages hath

consumed the substance therof, hath made it incapable of

producing any vegetalls. Only the topps of the high mountaines in the middle appeared somwhatt greene, there beeing

a kind of rushes and spicy [Pspiky] grasse. Some of our

company went up and broughtt downe six or seven goates,

doubtlesse att first left there by the Portugalls: allsoe halfe

a dozen of a strange kind of fowle, much bigger then our

sterlings ore stares: collour gray or dappled, white and

blacke feathers intermixed, eies red like rubies, wings very

imperfitt, such as wherewith they cannot raise themselves

from the ground. They were taken running, in which they

are exceeding swift, helping themselves a little with their

wings (as it is said of the estridge), shortt billed, cloven

footed, thatt can neither fly nor swymme. It was more then

ordinary dainety meatt, relishing like a roasting pigge

(Peter Mundy, in Temple and Anstey, ed., 1936:82-83).

Peter Mundy was a traveler of exceptional perception who several times in the 17th century

sailed from England to India and made stops at

Ascension and St. Helena while keeping a detailed

journal of his observations. With his entry (above)

on Ascension Island he included a small sketch of

his "strange kind of fowle" (Figure 2) which, although historically interesting, is hardly diagnostic.

It shows a bird with a medium-sized bill and reduced wings, but whether the flecks on the body

represent dappled plumage, as Ashmole (1963a)

conjectured, or whether they are simply indications of feathers, is speculative. Kinnear (1935),

in commenting on the fauna mentioned in Mundy's journal, came to the conclusion that the Ascension bird was an extinct flightless rail; a decision

that was concurred in by other ornithologists

FIGURE 2.—Peter Mundy's sketch of the Ascension rail,

with a sample of his script for scale. (From Temple and

Anstey, ed., 1936:83.)
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
NUMBER 152

(Murphy, 1936:151; Hagen, 1952:230). However,

as no such bird exists on Ascension today, Stonehouse (1962) felt that Mundy's description might

apply to juvenile Sooty Terns (Sterna fuscata) despite the fact that their eyes are brown, their feet

webbed, and their locomotion hardly "exceeding

swift." It is certain now that this was not the case.

No further information relating to this bird on

Ascension Island was forthcoming until the British

Ornithologists' Union (BOU) sent an expedition

to Ascension in 1957-1959 to study its seabird colonies. In order to gain some knowledge of the past

seabird fauna, the expedition searched for avian remains in several sites on the island. Included among

the bones they discovered was the skull of a small rail

taken from a deep fumarole north of Sisters Peak,

and a ralline tarsometatarsus from phosphate deposits south of South Gannet Hill. These were

reported on by Ashmole (1963a), who thought

them to be unlike any living rail, but he refrained

from naming the bird in the hope of being able to

obtain more material at a later date. He provisionally considered the species a member of the genus

Rallus while pointing out that the skull was proportionately very similar to Atlantisia rogersi of

Inaccesible Island in the Tristan da Cunha group.

The late James Fisher (Fisher and Peterson, 1964:

241, 273) referred to the Ascension rail as "Crecopsis sp.," and it is listed as such in the Red Data

Book (Vincent, 1966). Fisher informed me (letter

of 22 January 1970) that he had done this solely

on the basis of Mundy's description, but on examining the skull he had later decided to refer

it to Rallus. Crecopsis egregia is an African rail

which is dappled and has a red eye but which is

probably not directly related to the Ascension rail.

Armed with these tantalizing scraps of information, it was my purpose in visiting Ascension to

attempt to obtain additional remains of the rail.

On arriving at the island in 1970, I went directly

FIGURE 3.—The collecting locality for the Ascension rail:

a, The barren volcanic landscape around the fumaroles

where the rail remains were found. Arrow indicates the large

fumarole, the smaller one is almost hidden to the right.

The large cinder cone is Sisters Peak. Note the white

patches of old guano on the leeward side of the rocks, b,

The precipitous descent into chamber B of the large fumarole. The floor of the chamber is about 7-8 meters below

the opening visible here. It should be self-evident why

flightless rails became entrapped within. (Photographs taken

14 July 1970 by Douglas S. Rogers.)

Fa.IRK 4.—Diagram of a cross-section through the interior

of the fumaroles shown in Figure 3. The blackened areas

show where most of the rail bones were found. Scale=approx.

•3 m. Arrow points north.

to the locality where Ashmole collected the rail

skull, this site being the larger of two fumaroles

situated on an elevated plain a few hundred meters

north of the base of Sisters Peak. A more inhospitable place is hardly to be imagined (Figure 3a).

The plain, which lies at about the 550 foot contour, consists of volcanic ash and cinders interspersed with mounds of lava. Looming some 300

meters above is the summit of Sisters Peak, a

large cone entirely composed of cinders. Aside

from a few lichens and wisps of dry grass, the area

is barren of life. In the midst of this "lunar"

landscape project two fumaroles, or driblet cones,

made up of blobs of red lava, remnants of the

most recent volcanic activity on the island. The

largest is about 8 meters high and is penetrated

by two chimney-like openings that descend for a

depth of about 10-12 meters (Figure 36). These

open into three large interconnecting chambers (Figure 4). For historical geology and further descriptions of this area see Daly (1925) and Stonehouse

(1960).

From both fumaroles the BOU party collected bird

remains, among which Ashmole (1963a) identified

bones of Masked Booby (Sula dactylatra), Fairy

Tern (Gygis alba), and Sooty Tern (Sterna fuscata). In chamber B of the large fumarole, I found

remains of Sterna fuscata, Sula dactylatra, and Redfooted Booby (Sula sula), and, in addition, a single

femur of a rail lying by itself on top of a pile of

recently dislodged debris. No other rallid remains

were found in this chamber and it is possible that
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

this one bone was accidentally dropped there by

one of the BOU party or other subsequent visitors

to the fumarole. A narrow crevice near the ceiling

of the south wall of chamber B led into a third

chamber (c). Access into (and egress out of) this

room was made difficult by a sheer drop of about

3 meters at the end of the crevice. In the east corner of this totally dark chamber, in a depression

about 1.5 X 2 meters, lay a myriad of small bones,

all of rails. Amongst them were shell fragments of

a single land crab (Gecarcinus lagostoma), a species which is now common on the southeastern

vegetated part of the island and on Green Mountain, but is seldom met with elsewhere on Ascension. In five descents into the large fumarole,

accompanied by D. S. Rogers or J. M. Couch, I

picked up with forceps all the large bones I could

reach, and with the aid of a camel's hair brush

and a spoon, removed a quantity of the smaller

bones and associated debris. From chamber c ran

several tunnels too narrow to permit passage but

into which a rail might easily have slipped. From

the largest of these, which Rogers with much difficulty was able to enter a short way, were extracted

bones of two rails and a single Gygis alba, the latter the only seabird found in chamber c. Rogers

saw other skeletons in this tunnel which he could

not reach but which he thought were rallid.

On analyzing the bones collected in this fumarole, I can account for the presence of about 35

individual rails—doubtless more remain secreted in

inaccessible crannies. Some of the bones are friable

and chalky and variously eroded, but others are in

an excellent state of preservation with very delicate processes still intact. None is mineralized. A

few appear somewhat yellowish as if they might retain some grease, while the proximal end of one

tibiotarsus still has a few shreds of tendon adherent. Most of the bones are of adult birds but

a few show the spongy articulations characteristic

of immaturity.

A few meters south of the large fumarole is the

rather wide opening of a smaller fumarole that

rises 2-3 meters above the plain. I did not explore

it until 1971, but previously Ashmole (1963a) had

reported no rail remains from this fumarole and

Stonehouse (1960:181) had said that he had taken

from it "all the skulls and fragments of long

bones." In three trips, however, I removed from

this site hundreds of additional bones of Sterna

fuscata from not less than 146 individuals, remains

of several Gygis and Sula and more importantly,

nearly 200 bones or fragments from at least 17 individual rails, and surprisingly, a few 'bones of a

single small heron (Olson, in prep. (a)).

Conditions in the small fumarole were somewhat

different than in the large one. The main part of

the floor lay about 6 meters below the rim and off

to one side was a pocket about 1.5 meters deeper

which contained nearly all the bones discovered at

this site except for those of a few Sula. The bottom of this pocket, about 1x 3 meters in area, was

filled with a loose, dry deposit of dust, cinders,

and the organic debris resulting from the decomposition of hundreds of bird carcasses, to a depth

of 60 cm, or more, in places. Bones lay jumbled

on the surface and throughout the powdery matrix,

those from the deeper layers being stained dark

brown while those on the surface were white. This

was in contrast to the large fumarole where the

bones were lying on bare rock.

The deposits of bones in both fumaroles bear

evidence of having accumulated over some period

of time but the latest specimens, to judge from

their appearance, can hardly be older than a few

hundred years. Unfortunately, in spite of the dry

conditions, no mummification appears to have

taken place and no feathers or other soft parts remain. However, all the elements of the skeleton

are represented, including such rarely preserved

items as the lacrimals, pterygoids, and even the

ossified portions of cricoid cartilages. None of the

rail specimens from either fumarole shows any

pathological condition although in my experience

in such a large series (at least 52 individuals) it

would not be unexpected to find a few bones that

had been broken and subsequently mended.

The remarkably reduced wing elements and carina of the sternum disclosed at first glance that

these remains were from an absolutely flightless

bird. As there were no other landbirds on the

island, there can be little doubt that these bones

are from the species described by Mundy. Being

unable to fly, the birds that ventured up the sides

of the fumaroles and tumbled into the steep vents

would not have been able to effect their escape.

Thus trapped, they must have wandered about the

interior until they dropped into the farthest recesses where they succumbed to lack of water and

food.
NUMBER 152

On comparing the exceptionally fine series of

bones of the Ascension rail with skeletons of other

Rallidae (see Appendix 1 for species compared),

one species emerged as being inescapably similar

in proportions and most details of structure, this

being the diminutive, flightless, Atlantisia rogersi

Lowe from Inaccessible Island, until now considered a monotypic genus. More surprisingly, the

very large, extinct rail, Aphanocrex podarces Wetmore, of St. Helena, also agrees closely in morphology with the Ascension bird and with A. rogersi.

For these and other reasons discussed further on,

I consider these three forms as congeners. The

characters of the expanded genus Atlantisia are

discussed in Appendix 2.

Atlantisia elpenor, new species

HOLOTYPE.—Complete left tarsometatarsus, fully

ossified (Plate 5e,f,g). Vertebrate paleontological

collections of the National Museum of Natural History (USNM 170129). Collected in depression on

the east side of the southernmost chamber of the

largest fumarole located about 260 meters true

north of the summit of Sisters Peak, Ascension

Island, South Atlantic Ocean (approximately

7°55'25"S; 14°22'15"W), on 17 June 1970, by Storrs

L. Olson and Jesse M. Couch. Directly associated

with the type were right and left humeri, ulnae,

radii, carpometacarpi, coracoids, scapulae, fibulae,

left femur, sternum, furcula, mandible, left quadrate, 13 ribs, 18 vertebrae, and 15 pedal phalanges

which have been cataloged under the same number,

as I am confident that they are all from the same

individual. As this specimen was well exposed and

in an excellent state of preservation and had the

mandible present but the rest of the skull lacking,

it is possible that the skull (Ashmole No. F21)

picked up by Ashmole and now in the British Museum (Natural History) may be from the same

individual. However, lest there possibly be any

confusion, and since there were so many other rail

remains in the area, I designate only the tarsometatarsus as the holotype. The associated elements

may be considered as especially significant paratypes in the large series of paratypical material

from the two fumaroles.

The type tarsus is 38.0 mm in total length; transverse breadth across head 5.5 mm; transverse

breadth across center of shaft 2.5 mm; transverse

breadth across trochleae 5.7 mm. It is near the

maximum length and stoutness for the species and

is yellowish white in color. There being so much

more material of tarsi and other skeletal elements,

I will not further belabor the description of the

actual type.

PARATYPES.—All of the various elements of rallid

material from the two fumaroles included in the

series USNM 169773-170128, 170130-170272, and

175803-175853 may be considered paratypes.

RANGE.—Ascension Island, South Atlantic Ocean.

STATUS.—Extinct; exterminated sometime after

1656.

ETYMOLOGY.—Elpenor was one of Odysseus' crew

members, who, while stranded on Circe's island, fell

from the roof of her palace, was killed, and descended straight to Hades. Odysseus later encountered Elpenor's shade during his journey through

the Underworld. The Ascension rail was also

stranded on an island and upon falling off the lip

of the fumarole, descended straight to the bowels

of the earth and was not known again until its

shades were stirred up by inquiring mortals invading its underworld tomb. The specific name

stands in apposition to that of the genus and is

in the nominative case.

DIAGNOSIS.—A medium-sized flightless rail, roughly the size of a Virginia Rail (Rallus limicola)

but with much reduced pectoral girdle and wings,

and stouter hind limbs. It is very similar in most

respects to Atlantisia rogersi but much larger, the

major bones averaging 25 to 35 percent longer. On

the other hand, A. elpenor is but half the size of A.

podarces (Table 2).

DESCRIPTION.—The skull of A. elpenor (Plate

16) is represented by several nearly complete crania

and cranial fragments, fragments of bill, and one

specimen that is nearly complete, with bill, palatal

bones, and cranium intact. In this specimen

(USNM 170131) the interorbital bridge had been

corroded away and when first collected the bill and

palate were connected to the cranium by only a

thread of the parasphenoid rostrum which with

subsequent handling parted. The specimen is superior to the skull collected by Ashmole (1963a,

pi. 10), which I have not examined, in that the

anterior portions including the palatines, vomer,

maxillopalatines, portions of the jugal bar, etc.,

remain attached. By approximating the two portions of the specimen, I got an overall measure-
8 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

ment of 51.6 mm length, which is essentially

identical to the 51 mm Ashmole estimated for the

British Museum specimen. The interorbital bridge

is quite narrow; 7 specimens range from 2.70 mm

to 3.25 mm (average 2.97) in width at the narrowest point. The bill is like that of A. rogersi

(Plate la). The nasal bar is narrow and twisted

dorsally in A. elpenor and is broader and flat in

A. rogersi. The palate is essentially like that of

A. rogersi save that the posterior portions of the

palatines are slightly more expanded and squared.

The scars for the attachment of M. pseudotemporalis superficialis and M. adductor mandibulae are

larger and deeper in A. elpenor, indicating a

greater development of the jaw muscles than in

A. rogersi.

The lacrimal in rails is a small delicate bone

and is not fused to the skull. Lowe (1928:123)

drew attention to the very distinctive nature of

the lacrimal of A. rogersi and I therefore felt myself most fortunate to obtain three lacrimals of

A. elpenor for comparison. These in no way resemble A. rogersi but are more like the typical

rallid form (Plate 2e). In A. rogersi the descending process is long, slender, and twisted, the head

of the bone is reduced to a pointed, anteriorly

projecting spur, and the horizontal process is a

short hook. In contrast, in A. elpenor there is a

broad square head with a deep depression on the

medial surface and a well-developed area for the

attachment to the nasal; the descending process is

fairly short and the horizontal process is long,

strong, and tapering. Lowe (1928:124) considered

the peculiar lacrimal of A. rogersi to represent a

remarkable degree of "generalization"; however, I

cannot agree with this determination. The condition of the lacrimal of A. rogersi is much more

likely some sort of specialization. It is not a retention of a generalized embryonic condition in the

Rallidae, as none of the embryos or chicks of rails

I have seen possess such a lacrimal. The lacrimal

does not provide attachment for muscles, but numerous ligaments do attach to it and in rails it

may provide a brace for the jugal bar and protection for the anterior orbital region (Cracraft,

1968). This bone in rails is quite variable in shape

as I have previously noted (Olson, 1970), but the

adaptative significance of such variations is unknown.

The mandible of A. elpenor (Plate 2c,d) is very

like that of A. rogersi, although in the latter the

symphysis seems slightly wider and more troughlike.

The furcula (Plate Sh) is slender and in the

shape of a narrow U, with the epicleideum represented by only a slight swelling.

The coracoid (Plate 3/,g) like all of the pectoral

elements, is reduced in size. The shaft is proportionately wider than in A. rogersi, not thickened

and bent as in A. podarces. As in A. rogersi, the

brachial tuberosity is in line with the shaft. The

sterno-coracoidal impression is considerably shallower than in A. rogersi and the scapular facet is

also shallow.

In the scapula of A. elpenor (Plate 3i) the tubercle for the attachment of the dorsal branch of

the tendon of M. expansor secondariorum is completely lacking, whereas in A. rogersi a reduced but

distinct tubercle is still present.

The sternum of A. elpenor differs greatly from

that of A. rogersi (Plate 4). In A. elpenor it is

broad and Hat, the carina being reduced to a thickened ridge about 1.5 mm at its greatest depth.

Thus, literally speaking, the species barely qualifies as a "carinate" bird and was without question

flightless. The carina of A. rogersi, in contrast, is

elevated posteriorly. In A. rogersi there is a deep,

rounded notch widely separating the coracoidal

sulci and completely obliterating the spina externa.

This notch is much shallower in A. elpenor although there is still no trace of the spina externa.

The sterno-coracoidal processes of A. elpenor are

fairly broad and short as in typical rails, not tenuous and elongate as seen in A. rogersi and also in

the large, flightless Weka (Gallirallus) of New Zealand. In A. elpenor, the posterior lateral processes

are short, scarcely extending beyond the xiphium,

and the sternal notches are correspondingly reduced, being confined to the posterior fourth or

less of the sternum. The xiphium of A. elpenor

is notched, unlike A. rogersi but like Gallirallus.

From the anterior end of the carina of A. elpenor,

two well-defined ridges extend forward to the internal margin of the ventral lip of the coracoidal

sulci, but in A. rogersi the anterior half of the

sternum is much more conspicuously flattened.

Overall, the sternum of A. elpenor is quite similar

to that of Gallirallus, except that the latter has

slender, elongate sterno-coracoidal processes like A.

rogersi. This similarity is purely convergent as the
NUMBER 152

sterna of flightless rails assume a number of shapes

that are not necessarily correlated with phylogenetic affinity (see below).

The humerus (Plate 3a,b) is not as robust as

that of A. podarces. The bicipital crest is better

developed and shaft slightly more curved than in

A. rogersi. The ectepicondylar prominence and

external tuberosity are further reduced than in

either A. rogersi or A. podarces.

In the ulna (Plate 3c) the external condyle is

slightly better developed than in A. rogersi. A

distinct depression just proximal to the internal

face of the external condyle of A. elpenor is not

apparent in the other two species of Atlantisia.

Compared to A. rogersi, the carpometacarpus of

A. elpenor (Plate Sd,e) has the proximal metacarpal symphysis somewhat longer and narrower,

the distal portion of metacarpal m not as thin, and

the external side of metacarpal n slightly narrower

and flatter.

In dorsal view of the pelvis (Plate 2a,b) the

portion of the posterior iliac crest above the antitrochanter flares rather abruptly outward, giving

the area between the crests a squared appearance

in A. elpenor. These crests in A. rogersi are less

prominent and spread apart gradually and farther

behind the antitrochanters, which gives the area

between the crests a triangular shape. The anteriormost part of the ilium of A. elpenor forms a

sharp, laterally directed point which is less developed and rounder in A. rogersi.

Except for size, the hind limb elements of the

three species of Atlantisia are quite similar (Plate

10). The shaft of the femur (Plate bc,d) of A.

elpenor, in lateral view, is more curved than in

A. rogersi. Proportionately, the shaft of the tibia

(Plate 5a,b) is narrower and the fibular crest is

shorter in A. elpenor than in A. podarces. The

fibula (Plate ba,b) of A. elpenor is a long slender

splint with the head less stout than A. podarces.

None of the 50 appropriate specimens of tarsometatarsus (Plate 5e,f,g) of A. elpenor has the ossified tendinal loop for the tendon of M. extensor

digitorum longus on the proximal anterior face.

In A. rogersi this loop is mostly cartilaginous and

the same may be assumed for A. elpenor; however,

this loop is fully ossified in A. podarces. The scar

for the hallux is deep in A. elpenor and is longer

than that of A. podarces. The internal trochlea of

A. elpenor is noticeably less flared medially than

in A. podarces.

The toes of A. elpenor, as far as can be determined from assembling the disarticulated phalanges, are of about the same proportions as A.

rogersi. The claws are not nearly as long and well

developed as those of A. podarces.

In plotting the lengths of the humerus, femur,

tibia, and tarsus on a graph, no bimodality is apparent except possibly in the tarsal measurements,

so it cannot be conclusively demonstrated that A.

elpenor was sexually dimorphic in size. The

amount of variation in size (Table 1), may nevertheless be attributable in part to sexual differences,

as in most rails the males are larger than the females.

Of the external characteristics of A. elpenor

there is only Mundy's description to go on. From

this we may assume the bird had a more variegated

plumage than the drab-colored A. rogersi, although

A. rogersi does retain some variegation. The red

eye noted by Mundy corresponds well with the red

eye of adult A. rogersi, although this is a character

TABLE 1.—Selected skeletal measurements of Atlantisia elpenor (shaft widths taken at the narrowest point; pelvic width taken across the

a n ti trochanters)

Characters

Cranial width

Length furcula

Length coracoid

Length scapula

Length humerus

Width head humerus ....

Width shaft humerus ....

Width distal humerus ....

Length ulna

Length radius

Length carpometacarpus

Length ilium

Width pelvis

Length femur

Width shaft femur

Width distal femur

Length tibia

Width shaft tibia

Width distal tibia

Length fibula

Length tarsus

Width head tarsus

Width shaft tarsus

Width distal tarsus

mm. max. mean

3

2

34

6

36

35

35

29

13

10

13

9

8

35

34

33

28

28

24

7

32

25

29

27

16.0

17.8

15.2

21.4

24.0

5.3

1.3

3.6

17.8

18.5

12.8

27.5

135

31.1

2.1

5.3

51.2

2.0

4.7

285

33.0

5.0

2.2

4.9

16.4

18.4

16.3

26.2

28.0

6.2

1.7

4.9

22.0

20.6

14.8

31.9

14.7

36.5

2.5

6.2

58.5

2.3

5.2

32.0

38.0

5.7

2.5

5.8

16J23

18.1

15.58

24.53

26.34

5.84

151

3.95

20.13

19.5

13.84

30.0

14.16

3451

2.28

5.80

55.29

2.19

5.02

30.9

35.48

5.31

2.32

5.40
10 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

that appears at random throughout the Rallidae

and is without taxonomic importance.

Environment and Extinction of the Ascension Rail

Ascension is a relatively small island (97 km2;

38 mi2), entirely volcanic in origin. Geological reports emphasize its extreme youth (e.g., Daly,

1925) and the oldest rocks have now been dated

at only 1.5 ± .2 million years of age (Chace and

Manning, 1972:5). Since the discovery of the island

in 1501, there has been no volcanic activity reported there, which is considered odd in view of

the very fresh appearance of some of the lava formations. The highest point on the island is the

peak of Green Mountain (860 m; 2817 ft). The

coastline consists mainly of steep rocky cliffs with

a few scattered patches of beach composed of shell

sand or pebbles. The climate is mild, temperatures ranging from about 26° to 29°C in the lowlands and 6° to 6.5°C lower on Green Mountain.

Rainfall on Green Mountain, which is often enshrouded in mist and clouds, averages about 708.6

mm (27.9 in) annually, but in the lowlands, where

near-desert conditions prevail, there is only about

127 mm (5 in) per year. Strong trade winds blow

with great consistency from the southeast. There

is very little seasonal variation in weather but at

rare intervals heavy rainstorms occur which may

destroy the nests and eggs of Sooty Terns (Huckle,

1924) and may have affected rails. These storms

are usually followed by a marked burst in growth

of vegetation. Unusually heavy rainfall preceded

my second visit to Ascension by several weeks.

When I arrived, most of the low areas of the island

were covered with rippling waves of grass where

before there had been only cinders. Within six

weeks this grass had dessicated and turned yellow

after having produced a prodigious amount of

seeds to await the next rains.

Duffey (1964) summarized the history of the

terrestrial fauna and flora of the island (although

he failed to cite Mundy's journal (Temple and

Anstey, ed., 1936), which contains several valuable

points of information aside from the reference to

the rail). Man has drastically altered the environment, probably from his first encounter with the

island. In Mundy's account, which is earlier than

any cited by Duffey, the only vegetation described

as present in 1656 was "rushes" and "grass" on the

higher mountains. Goats were already present and

Mundy is probably correct in assuming that they

were released years earlier by the Portuguese discoverers of the island. The impressions of the earliest botanists to visit the island largely confirm

Mundy's report. Only two shrubs are known to be

native to Ascension, both of which are endemic

(Euphorbia origanoides and Hedyotis adscensionis,

the latter apparently extinct). A few other flowering plants and grasses, as well as a number of

cryptogams, including several endemic ferns, are

native to the island, most of these being confined

to the Green Mountain area. The disproportion of

cryptogams to phanerogams indicates an early stage

of floral colonization of Ascension somewhat similar to that reported for the Pliocene of St. Helena

(Muir and Baker, 1968). Osbeck (1771, 11:98) described "several petrifactions of branches of trees

and pieces of wood" and was under the impression

that the island had formerly been forested. Murphy

(1936:154, 865) assumed that Ascension was forested at one time, mostly on the basis of Osbeck's

testimony. There is no other evidence, however,

that this was the case. Palynological studies by

Duffey (1964) showed no evidence of pollen from

indigenous trees and he discounts the idea that the

island ever possessed forest cover. Very likely Osbeck mistook some of the deceptively woodlike

lava formations about the island for actual remains

of trees. There is very little area of suitable soil

for forest growth on the island and much of what

is now present resulted from the mulch of introduced plants and from direct importation of soil.

The impoverished flora of the island has been

greatly augmented by man's introductions, most of

which, after the establishment of a permanent British garrison in 1815, were intentional. The invertebrate fauna is likewise depauperate and the

presence of many species may well be the result of

having been unintentionally introduced along with

plants. There are now no native terrestrial vertebrates (the only one known was Atlantisia elpenor). Of the several species of birds that were

released on the island, only four have persisted,

and these are dependent on the man-made vegetation landscape. They are a francolin (Pternistes

afer), a myna (Acridotheres tristis), and two finches

(Estrilda astrild, Serinus flaviventris).

Pelagic seabirds that used the island for nesting

and roosting were once present in tremendous
NUMBER 152 11

numbers on the main island of Ascension as all

the early accounts testify (Temple and Anstey, ed.,

1936; La Caille, 1763). Huge colonies of boobies

(Sula spp.), Sooty Terns (Sterna fuscata) and

frigatebirds (Fregata aquila) were reported, mostly

from the northwestern and southern portions of the

island (for an account of the history of the seabird colonies of Ascension, see Stonehouse, 1962).

Because of introduced predators, all but the Sooty

Terns and a few Gygis abandoned the main island

and retreated to Boatswainbird Islet, a 96-meter

(315 ft) high trachytic monolith, roughly 4000

m- in area, lying about 250 meters off the eastern

side of the main island. Most of the island's remaining populations of tropicbirds (Phaethon

aethereus, P. lepturus), noddy terns (Anous stolidus, A. tenuirostris), Fairy Terns (Gygis alba), and

petrels (Oceanodroma castro) are also found on

this crowded refuge and adjacent cliffs. Only large

deposits of guano and dung-whitewashed rocks,

especially in the area between Sisters Peak and English Bay, remain as mute testimony of the former

great abundance of the seafowl of Ascension. In

the vicinity of the fumaroles may be found guano

and numerous rocks whitened on their leeward

side (Figure 3a), and in crevices in the rough lava,

skeletons and even feather shafts of boobies (Sula

dactylatra) are occasionally encountered.

How did Atlantisia elpenor survive in its seemingly hostile environment? What role did it play

in the island's relatively simple ecosystem? Upon

what did it feed? The island's poor flora could

hardly have provided enough, if any, suitable seeds

or fruit; nor, presumably, was there ever much of

an invertebrate fauna associated with this flora to

provide it with sustenance. It is possible that some

birds may have been able to glean a little food

from the few beaches available for foraging, but

these very small areas could hardly sustain a viable

population of any bird. Furthermore, the only indications of the bird have come from the interior

of the island. Mundy's (Temple and Anstey, ed.,

1936) account implies that their birds were taken

up on the mountain. The fumaroles are about 3

km from the nearest beach, over rough country—a

long trip for a flightless bird. The locality south

of South Gannet Hill, where Ashmole (1963a) collected a tarsus of A. elpenor, is about 1 km from

the very small beach at Mars Bay and well over

2 km from the nearest suitable beach at Southwest

Bay. The species must have been fairly numerous,

as evidenced by the abundant remains in the fumaroles and the fact that Mundy's men could catch

a half-dozen individuals in one afternoon's foray.

It is obvious that there must have been a good

many rails in the neighborhood of the fumarole

and that they were finding food in the vicinity.

The most probable explanation is that A. elpenor

was a scavenger in the large colonies of seabirds.

During the process of feeding, the young and adults

of boobies and terns often drop food. Thus, the

rails would have had an ample supply of pelagic

fish, squid, and crustacea available to be picked

up, or perhaps even stolen directly, not to mention

an abundance of seabird eggs, which were no doubt

taken as well. In the carcasses of birds on

Boatswainbird Islet, I found numerous dermestid

beetles which are probably an original element in

the fauna and these could well have provided an

additional food source for the rails. With the bird

remains in both fumaroles were numbers of dipterous pupae cases which would indicate that flies

and maggots were abundant. The Laysan Island

Rail (Porzanula palmeri), which lived in a situation somewhat similar to that of A. elpenor, was

observed to eat the eggs of seabirds and maggots

from carcasses (Rothschild, 1893). The Spotless

Crake (Porzana tabuensis) has been seen to eat

petrel eggs in the Kermadec Islands (Soper, 1969),

so there is ample precedent among rails for using

seabird colonies as food sources. In a different

order, adults and young of sheathbills (Chionis)

during the breeding season subsist almost entirely

on krill regurgitated by penguins (Jones, 1963) and

seem particularly well adapted to this semiparasitic existence. As there is seabird nesting

activity the year around on Ascension (Stonehouse,

1960:213), the rail would have been able to reap

an abundant harvest throughout the year in its

commensal role.

Judging from the old reports and the guano

that still remains, the seabird population of Ascension was very large, and one might assume a correspondingly large population of rails. Predation

would certainly not have been a limiting factor

under natural circumstances. The only possible

predator of A. elpenor would have been the frigatebird Fregata aquila, a species that does prey

to a certain extent on the chicks of Sooty Terns.

The agility and speed of rail chicks and adults,
12 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

plus their relative scarcity in comparison to more

easily obtained food would certainly have precluded their capture by frigatebirds on any but

the most exceptional of conditions.

Unfortunately, we know nothing of the nesting

of A. elpenor. The only typically suitable nesting

cover would have been on Green Mountain and

adjacent vegetated areas. The birds perhaps could

also have nested in small sheltered crannies in the

lava flows of the lowlands, using the sparse grass

and possibly feathers to construct a nest. Again,

Chionis provides a fine example, as it nests in

rocky holes and lines its nest with feathers, eggshells, and bones of penguins (Jones, 1963).

One factor that is more difficult of explanation

is the seeming ability of the rails to cope with the

almost complete lack of fresh water on the island.

The only more or less permanent sources of water

are on Green Mountain. The nearest of these to

the fumaroles is a small seepage area (Dampier's

Drip), the result of an accumulation of water above

an impermeable, compact layer of iron oxide (Darwin, 1844), which is 3.2 km away. South Gannet

Hill is even farther from a source of fresh water.

Rain does not collect in any appreciable amounts

in the porous rocks and soil, and rainfall in the

area of the fumaroles, for instance, is very slight

anyway. Atlantisia elpenor probably ingested regurgitated invertebrates such as squid, which are

isotonic to seawater, making some mechanism of

salt excretion a necessity. In the salt-marsh dwelling rail Rallus longirostris, the interorbital bridge

is narrowed to accommodate hypertrophied supraorbital glands which function in the excretion of

salt. The much narrowed interorbital bridge of

A. elpenor is a good indication that its supraorbital

glands were equally well developed. The birds,

therefore, probably derived their water solely from

their food.

With the coming of man, Atlantisia elpenor was

a doomed species. As mentioned, goats were an

early introduction to the island, although they

probably had little effect on the avifauna. At some

unknown time, rats and mice made their appearance. They were present by 1754 (La Caille, 1763)

and Osbeck (1771, 11:84) felt that they came to

the island with the wreck of William Dampier's

ship Roebuck in 1701, although they may well

have reached shore previously with vessels stopping

for sea turtles or other supplies. The rats at least

must soon have made inroads on the population

of ground-nesting rails and probably some of the

seabirds as well. Kepler (1968) has documented

the grisly effects of direct predation by Rattus exulans on seabirds in the Pacific.

Just how long after 1656 the Ascension rail survived is not known. If present, its numbers must

have been considerably reduced by the 1700s as the

species was never reported again. If any persisted

into the 19th century they could never have survived the coup de grace administered by the British

who introduced cats for rodent control soon after

1815. By 1823, feral cats were in abundance and

by the 1860s this vicious scourge had eliminated

all but the Sooty Terns from breeding in significant numbers on the main island (Stonehouse,

1962:111-113). Thus, the rail and its source of

food were both destroyed.

Vagrant Rallids

In recent times, three species of rallids have

found their way across hundreds of miles of open

ocean to Ascension. The first of these to be reported was a gallinule "killed with a stick near

the summit of the island" in July 1836 (Darwin,

1841:134) and which was made the type of a new

species "Porphyrio simplex" (Gould, in Darwin,

1841). Sharpe (1894) synonymized this with Porphyrula parva (=P. flavirostris), an uncommon

South American species, which has not otherwise

been recorded as an ocean-crossing vagrant. Gould's

description is of an immature bird and does not

tally with the appearance of P. flavirostris while

the measurements given are too small for P. martinica. Therefore, I think that it is highly likely

that this specimen represents the African species

P. alleni. An immature specimen of Porphyrula

alieni was taken on Ascension on 27 May 1920 and

reported by Lowe (1924). I have examined this

specimen and confirmed its identity.

I have reported and discussed two unexpected

instances of the occurrence of the American Purple

Gallinule (Porphyrula martinica), both immatures,

on Ascension in June in 1970 and 1971 (Olson,

1972).

Stonehouse (1960, 1962) records the capture of

a juvenile Common Gallinule (Gallinula chloropus) at Mars Bay during the BOU expedition. Unfortunately, the bird was not made into a specimen
NUMBER 152 13

and later escaped, eliminating the possibility of a

subspecific determination. In view of the fact that

both American and African species of Porphyrula

have occurred on Ascension, it would seem that

Gallinida chloropus, which is native to both continents, could come from either direction. Stonehouse (1960:153) mentions a farmhand on Ascension who had seen other gallinules in previous

years, and my own discussions with islanders imply

that gallinules (probably of all three species) are

of fairly regular occurrence there. The significance

of these records is discussed later.

RAILS OF ST. HELENA

Beneath the upper and central green circle, the wild valleys

are quite desolate and untenanted.

Darwin, 1846

Darwin's impression of St. Helena is as true

today as it was in 1836, but at one time the

desolate valleys were well tenanted with multitudes of birds. The island of St. Helena has undergone a drastic alteration of its fauna and flora since

its discovery by man in 1502. At present there are

only two species of landbirds (an endemic plover,

Charadrius sanctaehelenae, and a gallinule) not introduced by man, and only a handful of seabird

species remain. Such was not always the case.

The BOU Ascension expedition also visited St.

Helena and while there collected a small series of

bird fossils from several sites on the island. These

and other collections, which were reported on by

Ashmole (1963b), indicated that there were many

other species of birds on the island in the past.

The deposits from which these fossils came range

in age from Pleistocene to recent. In 1971 I visited

these same localities, discovered a few other sites,

and collected thousands of fossil specimens, mostly

of seabirds. All of these specimens are now in the

National Museum of Natural History, Smithsonian

Institution. These sites and most of the specimens will be described in detail in a later paper

covering the entire former avifauna of the island.

Here I will concern myself only with the rails. An

assortment of fossils from Prosperous Bay and Dry

Gut collected by Arthur Loveridge and forwarded

to the Museum of Comparative Zoology also contains a few bones of rails and these are included

in the following discussions.

Redescription and Relationships of

"Aphanocrex" podarces

From the extensive sediment deposits at Prosperous Bay, the BOU expedition collected several

elements of a very large rail. These were subsequently examined by Wetmore (1963) and described as a new genus and species, Aphanocrex

podarces. The material available to Wetmore consisted of a left tarsometatarsus (the type), one

right and one left femur, a left tibiotarsus, a proximal right ulna, a distal left humerus, and a partial

pelvis.

My own collections contain a number of specimens of this species from four localities in all parts

of the island. From the same deposits on the east

bank of the gorge at Prosperous Bay came a right

and left tarsus, proximal and distal left tibiae, a

right femur, a cervical vertebra, and a pedal phalanx. In addition, on the west bank I unearthed

much of a skeleton of a single individual associated

with the bones of a frigatebird (Fregata sp.). This

specimen (USNM 175878) is represented by a right

femur, right and left tibiae, the head of a fibula,

right and left tarsi, seven pedal phalanges (including two claws), right and left humeri (both lacking

distal ends), right ulna (lacking proximal end),

right and left carpometacarpi, digit n phalanx 1

of the wing, right and left coracoids (both lacking

the sternal ends), 3 cervical vertebrae, 2 fragments

of pelvis, and a fragment that appears to be part

of the posterolateral process of the sternum. In

the MCZ collections are a right and a left femur,

right ulna, proximal right tibia, and a fragmentary

right tarsus. The Prosperous Bay specimens do not

appear to be mineralized and are probably of no

great age. Including the material examined by

Wetmore, there are at least four, and very likely

more, individuals represented from this site.

From the eroded washes of Dry Gut, near Bencoolen, I collected the following material of the

large rail: two left femora and a proximal right

lemur, a proximal right tibia, three proximal right

tarsi, a fragment of a distal left tarsus, a distal left

humerus and a proximal left coracoid. There is a
14

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

distal right tibia in the MCZ collections. Some of

these specimens are quite well mineralized and are

ot obviously greater age than those from Prosperous

Bay. Not less than three individuals are represented from this site.

Near Sugarloaf Hill are aeolian deposits of calcarious sand that are much dissected by erosion.

These are thought to be Pleistocene in age (Baker,

1970) and contain fairly abundant bird remains.

Here I collected a single, well-mineralized and

nearly complete right tarsus of A. podarces.

Ashmole (1963b) has described all of the above

localities but listed remains of A. podarces only

from Prosperous Bay. However, a worn proximal

end of a right tibia (BMNH S/1963.25.24) from

the Sugarloaf site which Ashmole (1963b:405)

thought "may represent another species of columbid," on examination proves to be from A. podarces, and in a lot of unidentified specimens

collected from this site by the BOU, I found a distal

left ulna of this species.

I found more bones of this species at one additional site that was discovered quite by accident.

While walking along the well-used trail next to a

small embankment immediately south of the old

battery ruins in Sandy Bay Valley, I saw an avian

tarsus which because of its size, location near

houses, and new appearance, I assumed to be of a

barnyard fowl or a pheasant. Picking it up out of

force of habit, I was more than pleasantly surprised

to find that it was a complete left tarsus of A.

podarces. Further searching on this low hillside

TABLE 2.—Size comparison of the three species of Atlantisia*

Characters A. podarces A. elpenor A. rogersi

Cranial width

Length mandible

Width interorbital bridge

Length furcula

Length coracoid

Length scapula

Length humerus

Width head humerus

Width shaft humerus

Width distal humerus

Length ulna

Length car pome tacarpus .

Length digit u phalanx 1

Length ilium

Width pelvis

Length femur

Width shaft femur

Width distal femur

Length tibia

Width shaft tibia

Width distal tibia

Width head fibula

Length tarsus

Width head tarsus

Width shaft tarsus

Width distal tarsus

26.4(1.96. 1.63)

10.7 (3.96, 3.60)

27##(2.45, 1.73)

58* • (2.93, 2.21)

13.0(3.25, 2.24)

4.0» * (4.00, 2.66)

9.1 (3.25, 2.33)

48.4 (3.56, 2.41)

35.5 (3.86, 2.57)

10.4(2.81, 2.00)

66.3 (2.60), 1.92)

4.9 (3.06, 2.13)

12.6(3.07, 2.17)

108.5(2.63, 1.96)

5.3(3.31, 2.41)

10.6(2.94, 2.12)

6.9(3.14, 1.97)

72.2 (2.97, 2.03)

11.1(3.00, 2.09)

4.8 (3.00, 2.09)

11.6(2.90, 2.14)

16.2(1.20)

40.5(1.25)

2.97(1.10)

18.1 (1.20)

15.6(1.42)

24.5 (1.22)

26.3(1.33)

5.8 (1.45)

1.5(1.50)

3.9(1.39)

20.1 (1.48)

13.8(1.50)

5.2(1.40)

30.0(1.40)

14.2(1.22)

34.5(1.35)

2.3 (1.44)

5.8(1.41)

55.3(1.34)

2.2(1.38)

5.0(1.39)

3.5(1.59)

35.5 (1.46)

5.3(1.43)

2.3(1.44)

5.4(1.35)

13.5

32.3

2.7

15.0

11.0

20.0

19.8

4.0

1.0

2.8

13.6

9.2

3.7

21.5

11.6

25.5

1.6

4.1

41.3

1.6

3.6

2.2

24.3

3.7

1.6

4.0

•The numbers outside parentheses are the means for each measurement (except where there

was only a single element available). The numbers in parentheses after A. podarces are the

means of that species divided by the mean of A. rogersi and A. elpenor respectively; the number in parentheses after A.elpenor is the mean of that species divided by the mean of A.rogersi.

Thus, for instance, we read that the cranial width of A. podarces is 26.4 mm, which is 1.96

times as large as A. rogersi and 1.63 times as large as A. elpenor, while the same measurement

of A. elpenor is 16.2 mm, which is 1.20 times as large as A. rogersi. Shaft widths taken at the

narrowest point. Pelvic widths measured across antitrochanters.

••Estimated.
NUMBER 152 15

disclosed the bones of other bird species and a left

carpometacarpus, the shaft of a tibia, a right fibula,

a cervical vertebra, a pedal phalanx, and a right

quadrate of the large rail. By far the best find,

however, was a complete cranium of this species.

It unfortunately is fractured off at the naso-frontal

hinge so that none of the bill or palate is present,

but the remainder is nearly perfect, the parasphenoid rostrum, interorbital septum and ectethmoids

being retained (Plate Ic). All of the specimens

from this site appear very recent and are possibly

from one individual.

With so much better material now available, it

is possible to make more extensive comparisons.

Wetmore (1963) in his analysis of the species compared it with Aramides and certain other large

rails, for the purposes of description only. He did

not suggest any relationships of the St. Helena bird

other than to subfamily (Rallinae). A relative exists, however, but in all fairness one would hardly

expect to look for the closest living relative of one

of the largest species of the family in one of the

smallest of the family that is also flightless and on

an even more remote island over 1500 miles to the

south. But with the perspective offered by the

nearly intermediate-sized A. elpenor, the similarity

of A. podarces to A. rogersi becomes apparent.

These three species are so alike in most proportions

(Table 3; Plate 10) and in most details of the

skeletal structure and so recognizably different from

related mainland genera, that in my opinion they

must be regarded as congeners. Aphanocrex Wetmore then falls into synonomy with Atlantisia

Lowe and its single species will hereafter be referred to as Atlantisia podarces.

The generic characters of Atlantisia I have set

forth in Appendix 2. Here I will attempt to redescribe the species A. podarces, especially in relation to the other two members of the genus.

Atlantisia podarces is a large rail, among the

largest of the family, but considerably more slender and less robust than is usual in the large

flightless forms such as Gallirallus or Nesotrochis.

In linear measurements it is double the size of A.

elpenor and nearly thrice that of A. rogersi (Table

2) but is similar in proportions except that it appears to be slightly though consistently stouter,

with somewhat longer wing elements (Table 3).

The head, however, does not increase by the same

proportion as body size, and, as in other birds, the

larger species has a proportionately smaller head.

Inasmuch as volume increases as the cube of linear

dimensions, the bulk of A. podarces must have

been in the neighborhood of 8 times that of A.

elpenor and 15-20 times that of A. rogersi.

The cranium (Plate \c) of A. podarces is massive,

about the size of Aramides cajanea and heavier

than, though not as elongate as, Gallirallus australis. The interorbital bridge is wide (10.7 mm)

and exceedingly thickened and inflated, being approached only by the ponderous Tribonyx mortierii in this respect. In comparison with A.

elpenor, this wide bridge certainly indicates a much

lesser development of the salt glands which reflects the abundant supply of fresh water on St.

Helena. Apart from the interorbital bridge and

the great disparity in size, the cranium of A. podarces is otherwise nearly duplicated on a smaller

scale in that of A. elpenor. The great similarity

in the shape of the scar for M. pseudotemporalis

superficialis is especially striking. In A. podarces

the cranium is more domed postorbitally than A.

elpenor. The fossa for M. adductor mandibulae is

deeper and the zygomatic area is enlarged, both,

along with the reinforced interorbital bridge,

TABLE 3.—Comparative proportions of the three

species of Atlantisia*

Characters

Cranial width

Length coracoid

Length humerus

Width head humerus

Width shaft humerus

Width distal humerus

Length ulna

Length carpometacarpus

Length digit n phalanx 1...

Length femur

Width shaft femur

Width distal femur

Length tibia

Width shaft tibia

Width distal tibia

Length tarsus

Width head tarsus

Width shaft tarsus

Width distal tarsus

A. podarces

.398

.4O7##

.875* •

.196

.060

.137

.730

.535

.157

1.000

.074

.190

1.637

.080

.160

1.089

.167

.072

.175

A. elpenor

.470

.452

.762

.168

.043

.113

.583

.400

.150

1.000

.066

.168

1.603

.064

.145

1.029

.154

.066

.157

A. rogersi

529

.431

.776

.157

.039

.110

533

.361

.145

1.000

.063

.161

1.620

.063

.141

.953

.145

.063

.157

•Mean of each measurement from Table 2 for each species has been divided by the mean femur length of that

species to obtain a proportion allowing the comparison of

the relative size of each element.

••Estimated.
16

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

probably correlated with a heavier bill and more

massive jaw musculature.

The quadrate of A. podarces is similar to that of

A. elpenor save that the shaft of the otic process is

wider.

The coracoid (Plate 6d,e) is quite large and

heavy. Its head is much more massive than in A.

elpenor or A. rogersi and the brachial tuberosity is

turned internally and is not in a line with the

shaft. The scapular facet is deep and cuplike in

contrast to A. elpenor and A. rogersi. The stout

shaft is bent and swollen at the midpoint, appearing almost pathological; but since both the right

and the left coracoids of the same individual appear identical, this is probably the normal condition. From what remains, the sternocoracoidal

impression seems to have been quite deep, more

so than A. rogersi and unlike A. elpenor in which

this impression is shallow.

The sternum of A. podarces is unknown except

for most of a right posterior lateral process with

an attached piece of sternal plate. This is wide

and thickened and would seem to indicate a large,

heavy sternum.

The head of the humerus (Plate 6f,g) is more

bulbous, with the capital groove less transverse and

closer to being parallel with the shaft than in

A. rogersi and A. elpenor. The ligamental furrow

is much deeper than in the latter two species. (See

Wetmore [1963, pi. 9] for an illustration of the

distal humerus). The ulna (Plates 6h,i; 10) of A.

podarces is heavier than in A. elpenor or A. rogersi,

with a larger internal condyle and deeper tendinal

pit on the external condyle; the distal radial depression is not as deep as in A. elpenor. The carpometacarpus (Plates 6j,k; 10) is like that of A.

elpenor but proportionately longer, with a longer,

more tapered distal symphysis.

The femur (Plate 10; Wetmore, 1963, pi. 9) of

A. podarces differs from A. elpenor and A. rogersi

mainly in having the ligamental attachment above

the fibular condyle rounder and deeper, with a

prominent ridge around it. The fibula (Plate 6c)

is essentially like that of A. elpenor but heavier

and thicker, In A. podarces, the tibia (Plates

6b,r; 10) is very similar to A. rogersi and A. elpenor

except that in dorsal view, the outer cnemial crest

is thicker and curved more posteriorly, and the

shaft is somewhat stouter. The tarsus (Plate 10;

Wetmore, 1963, pi. 9) is of nearly identical proportions to A. elpenor. It differs from that species

and from A. rogersi in that the loop for the tendon

of M. extensor digitorum longus is completely ossified, the posteriormost ridge of the hypotarsus is

broad, flat, and more prominent, the scar for the

attachment of the hallux is deeper but shorter and

more rounded, and the internal trochlea is flared

out farther medially.

The toes (Plate 6a) are long and strong (not as

heavy as Gallirallus) with exceedingly long and

sharp claws (longer than Tribonyx mortierii, Gallirallus australis, or any other rail I have seen).

One claw core, which I assume by its size to be

from the middle toe, is fairly straight and measures

18.5 mm in length. With its sheath it must have

been well over 22 mm long. It composes 25.6 percent of the total length of the middle toe (with

claw) whereas the claw of A. rogersi constitutes

only 15.6 percent of the total length of the middle

toe.

Of only the tarsus is there enough material to

give some indication of individual size variation.

These measurements are as follows: length 70.1,

72.4, 74.0; width of head 10.7, 10.7, 11.0, 11.4, 11.5,

11.6; width distal end 10.6, 11.4, 11.8, 12.2. Here,

and in Tables 2 and 3, I have incorporated the

measurements given by Wetmore (1963). Though

there is little in these measurements to indicate the

extent of variability in size, visual comparison of

some of the elements (for instance the proximal

tarsi from Dry Gut) shows a discernible difference

in individual dimensions and this was likely correlated with sex.

A Second Species of Extinct Rail

From three of the four major collecting localities on St. Helena I uncovered numerous remains

of a second species of flightless rail, much smaller

than A. podarces. Considering the relative abundance of this species in these deposits, it is somewhat surprising that it had not been discovered

before, but Ashmole (1963b) mentions no such

bird.

Prosperous Bay (deposits on the east side of

gorge): In addition to the nearly complete skeleton which I have designated as the type, the following elements were found: 3 right (one is a

shaft only) and 1 left femora, 2 complete and 1

distal right tibiae, 1 distal left tibia, 3 right and 1
NUMBER 152 17

left tarsi, 1 left humerus, 1 distal mandible, 1 rostrum and the tip of another. Another individual,

from the west bank of the gorge, is represented by

a right humerus, distal mandible, and the left posterior lateral process of the sternum. In the MCZ

collections are the proximal and distal ends of a

left tibia and a distal right tibia. At least five

individuals are included in the Prosperous Bay

collections.

Dry Gut: One complete and 1 proximal right

femur, 1 complete and 2 distal left femora, 2 distal

and 2 proximal left tibiae, 2 distal and 2 proximal

right tibiae, 1 complete and 2 distal left tarsi, 1

proximal right tarsus, 1 radius, 1 right carpometacarpus, and 1 left lower jaw articulation. In the

MCZ collections is a complete right femur. A minimum of four individuals from this site.

Sandy Bay Valley: An articulated right tibia and

tarsus, the latter with ossified tendons associated

(later lost); 1 right and 1 left femur, 2 complete

and 1 distal left tibiae, 1 proximal right tibia, 2

right and 1 left humeri (the latter from a juvenile). These remains represent not less than three

and probably at least four individuals.

This small rail is a short-billed crake-like form.

As the other landbirds of St. Helena of known

derivation are African, and the prevailing winds on

St. Helena are from the southeast, it is logical to

expect the small rail also to be of African origin.

However, the American species Porphyrula martinica has now been taken at least twice on St.

Helena (see below). The small St. Helena rail

does not agree with any of the species examined

of the American genus Laterallus, as these all have

markedly longer and more slender hindlimbs and

pelves. It in no way agrees with Sarothrura, being

heavier throughout, longer billed, and having a

different palatal structure among other things. It

is much smaller than Aenigmatolimnas, Crecopsis,

Crex, and Lirnnocorax and does not have the peculiar bill shape or long legs of Aenigmatolimnas,

nor the narrow, twisted nasal bar of Crecopsis and

Crex, nor any of the hindlimb modifications of

Limnocorax. Of African "crakes," this leaves only

the genus Porzana, with which it quite agrees in

bill shape, palate, pelvis, and hindlimb structure.

It represents an undescribed species.

Porzana astrictocarpus, new species

HOLOTYPE.—Nearly complete skeleton (Plates

7, 8, 9). Vertebrate paleontological collections of

the National Museum of Natural History, Smithsonian Institution (USNM 175893). Collected from

the bank of a dry wash on the east side of the

lower portion of Prosperous Bay Valley, St. Helena

Island, South Atlantic Ocean (approximately

15°56'18"S; 5°38'5"W), on 12 June 1971 by Storrs

L. Olson. The specimen consists of a complete

skull (braincase crushed) that includes the palate,

sclerotic plates, hyoids, lacrimals, pterygoids, and

right quadrate; complete mandible; pelvis (lacking

pubic bones); both wings (lacking only digits i

and in, radiales, and one ulnare); both scapulae;

left coracoid; proximal two-thirds of left clavicle;

complete right hind limb including all phalanges

and ossified tendons; left femur lacking only the

head. The bones are dark tan in color and are

only slightly, if at all, mineralized. Unlike most

of the specimens that were picked up from the

surface or partially embedded in the fine silt in

the upper layers of the Prosperous Bay deposits,

the type was firmly embedded in an eroded embankment under nearly 2 meters of cindery sediment. In the skull and some of the other bones

are minute holes or scars, the edges of which are

reddish brown in color and appear almost as if

burnt. Other specimens from Prosperous Bay bear

these same sort of marks which may have been

made by rootlets formerly growing around the

bones. The type-specimen is remarkable in retaining almost all the important bones but totally lacking the ribs, vertebrae, and sternum. Since most

of the toe bones were found in direct association

with the skull, the specimen was probably buried

doubled backwards on itself and the ribs, vertebrae

and sternum later washed away. The left femur,

the only element of that leg found, was discovered

in two pieces washed out onto the bottom of the

gully, a few inches directly below the rest of the

skeleton.

PARATVPFS.—The paratypical series consists of

USNM 175894-175935, 175945-175949, and 175960.

RANGE.—St. Helena Island, South Atlantic

Ocean.

STATUS.—Extinct, probably exterminated after

the island's discovery in 1502.

ETYMOLOGY.—Latin, astrictus, drawn together,
18

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

plus carpus, referring to the peculiar approximation of the metacarpals in this species. The specific name is considered a noun in apposition.

DIAGNOSIS.—A small, flightless Porzana; pelvis,

and hindlimb intermediate in size and proportions

between Porzana pusilla and "Porzanula" palmeri

(I do not consider Porzanula separable from Porzana, see below); wings and pectoral girdle reduced

to the same extent as P. palmeri (for comparisons

see Table 4 and Plate 11); interorbital bridge with

longitudinal furrow; proximal intermetacarpal

space constricted; distal femur much expanded.

DESCRIPTION.—The only available skull, that of

the type (Plate 7a,b) is slightly larger than Porzana

pusilla and some specimens of P. palmeri and has

the typical short bill of a Porzana. The nasal bar

is wide and flat. In P. palmeri the bill is longer

than P. pusilla, with a longer premaxilla and more

elongate nostril. The St. Helena bird falls exactly between these two species in these respects and

is slightly more robust than either. A longitudinal

furrow creases the interorbital bridge of P. astrictocarpus; only a hint of this may be seen in P. palmeri and it is not found elsewhere in Porzana. The

postorbital process is blunt, ventrally directed and

with a distinct depression above it. The palate is

very similar to P. palmeri. Fortunately, the right

iacrimal of the type is complete (Plate Id). This is

nearly identical to that of P. palmeri save that the

descending process is longer. It is similar also to

P. pusilla except that in that species the horizontal

process is straighter and does not curve outward

and downward posteriorly. These three species

differ from Porzana albicollis, P. porzana, P. Carolina, and P. fusca, in which the Iacrimal is wider

with a short, anteriorly curved descending process.

The mandible (Plate la,c) is a little heavier and

more expanded in the articular regions, and in

medial view is higher than in either P. palmeri or

P. pusilla. The symphysis, which is rather long

TABLE 4.—Selected skeletal measurements of three related species of Porzana

(shaft widths taken at narrowest point; pelvic widths across antitrochanters)

Characters P. astrictocarpus

P.

pusilla

(n=2)

mean

P.

palmeri

(n=8)

mean

Cranial width

Length skull

Width interorbital bridge

Length mandible

Length coracoid

Length scapula

Length humerus

Width head humerus

Width shaft humerus

Width distal humerus

Length ulna

Length radius

Length carpometacarpus

Length ilium

Width pelvis

Length femur

Width shaft femur

Width distal femur

Length tibia

Width shaft tibia

Width distal tibia

Length fibula

Length tarsus

Width head tarsus

Width shaft tarsus

Width distal tarsus

19.8

4.0

1.2

3.0

10.8

25.3

1.8

4.3

42.4

1.7

3.6

26.2

3.9

1.9

4.1

20.9

4.3

1.3

3.2

11.3

29.0

2.2

5.1

44.5

2.0

4.2

27.9

4.1

2.1

4.4

14.9

39.8

3.4

29.7

12.4

20.0

20.2

4.2

1.3

3.1

14.8

13.3

11.0

25.0

12.2

27.0

1.9

4.6

43.3

1.9

3.9

22.8

27.0

4.0

2.0

4.2

12.8

38.3

3.7

29.4

15.6

27.8

28.0

5.5

1.8

3.8

23.0

21.4

16.4

25.3

11.1

30.1

1.9

4.3

46.8

1.8

3.7

29.5

3.6

1.9

4.0

13.3

39.1

3.0

29.9

10.8

19.4

20.0

4.2

1.2

3.0

14.9

13.7

10.4

22.8

12.0

25.7

1.9

4.1

38.5

1.7

3.5

22.7

23.5

3.6

1.8

3.9
NUMBER 152 19

in P. palmeri and short in P. pusilla and other species of Porzana, is intermediate in P. astrictocarpus.

The coracoid (Plate Sb,c) is, of course, greatly

reduced compared to flying forms such as P. pusilla, and is longer and more slender than in P.

palmeri. In P. palmeri the procoracoid process is

not as broad, and the fenestra is placed higher than

in P. astrictocarpus. The head is narrow, in line

with the shaft and not deflected internally in P.

astrictocarpus. The sterno-coracoidal process is

relatively high and blunt; sternal facet with a welldeveloped flange on internal side. Sterno-coracoidal

impression not particularly deep but with a prominent thickened ridge on its antero-dorsal margin

for the attachment of the sterno-coracoid ligament.

Of the furcula there is only part of the left

clavicle (Plate 8b). This is a slender rod with a

knob at the coracoidal extremity.

The scapula (Plate 8a) is smaller even than in

P. palmeri, which it resembles in having the acromion rounded and blunt whereas this process is

longer and pointed in other species of Porzana.

Porzana palmeri differs from P. astrictocarpus in

having the glenoid facet larger and more expanded.

In P. astrictocarpus no vestige remains of the tubercle for the attachment of the M. expansor secondariorum tendon, although this tubercle is

well-developed in volant species of Porzana and a

small bump is still to be found in P. palmeri.

Of the sternum there is known only a left posterior lateral process with a small piece of the

sternal plate attached. The anteriormost part of

the sternal notch is indicated. The lateral process

is very short and the notch shallow (Figure 5),

much more so even than in P. palmeri. This abbreviated condition obtains in most flightless rails.

I would estimate from this scrap, that the whole

sternum of P. astrictocarpus was smaller than that

of P. palmeri.

The humerus (Plate Sd,e) is identical to that of

P. palmeri in size and proportions, although the

distal end is slightly wider. In P. astrictocarpus

there is a distinct longitudinal scar immediately

below the median crest of the internal tuberosity;

this is absent in P. palmeri. The olecranal fossa

is wider and shallower and the distal condyles reduced in contrast to P. palmeri and P. pusilla. The

brachial depression is much deeper than in the lastnamed species.

The ulna (Plate 8/) is nearly identical in size

and details to P. palmeri but the shaft is not as

stout, external condyle slightly larger and rounder,

and brachialis impression deeper. The radius (Plate

8/) is very near in size to P. palmeri from which it

does not otherwise differ.

The carpometacarpus (Plate 8g,/i,i) is extremely

similar to that of P. palmeri except in one singular

detail. The proximal half of metacarpal m is expanded dorsally and from the opposite side, on

metacarpal u, an excrescent ridge extends toward

the expansion of metacarpal HI, thus narrowing the

proximal half of the intermetacarpal space to a

small slit. In the more robust carpometacarpus

from Dry Gut (Plate Si), one of the projections of

metacarpal n has succeeded in fusing with metacarpal in,, leaving a small foramen proximally.

This condition cannot be a pathological one, as it

occurs identically on both sides of the type and

in an entirely different specimen from a different

locality. I have not seen a like condition in any

other rail. On the dorso-medial surface of the left

carpometacarpus of the type was a short portion of

ossified tendon, doubtless of M. flexor digitorum

profundus which is ossified in this area in other

rails.

••._ •

FIGURE 5.—Reconstructed sternum of Porzana astrictocarpus. Portion outlined in black is drawn from the specimen

of posterior lateral process USNNf 175907, Prosperous Bay,

St. Helena. Dotted lines indicate the hypothetical shape of

the rest of the sternum as extrapolated from the fragment.

Scale=10 mm.
20 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

The pelvis (Plate 9a,b) is of interest for its intermediacy. It is neither as long and narrow as in

P. pusilla, nor as short and broad as in P. palmeri.

Other than in these general proportions, the pelves

of these three species do not differ appreciably.

The femur, also intermediate in proportions

(Plate 9c,d), is not as long and slender as P. pusilla

or as short and stocky as P. palmeri. However, it

differs conspicuously from these and any other

crakes in the much expanded distal articulation.

This appearance is for the most part due to the

greatly enlarged fibular condyle which projects

farther laterally and posteriorly than in any related species. The trochanter is better developed

also. The posterior intermuscular line is more

prominent and displaced medially which may be

correlated with the apparent lateral rotation of

the entire distal end of the femur.

The fibula (Plate 9e) is the size of that of P. palmeri but the head is somewhat heavier, probably

in accordance with the larger fibular area of the

femur. Distally it is more attenuated than in P.

palmeri.

The tibia (Plate 9e,f) presents intermediate proportions. It is shorter and stockier than P. pusilla

but not as short and heavy as P. palmeri. The

proximal end is broader than either. Associated

with the tibia of the type were six ossified tendons.

Three of these were ascertained to be the tendons

of M. peroneus brevis, M. tibialis anticus, and M.

extensor digitorum longus. On the tibial shank

the following tendons may also be ossified in the

Rallidae: M. flexor perforans et perforatus digiti

in, M. flexor perforatus digiti n, M. flexor hallucis

longus, and M. flexor digitorum longus. Any of

these may have been ossified in P. astrictocarpus.

The tarsus (Plate 9g,h,i) is stout but not as short

as in P. palmeri or as long and slender as in P.

pusilla. The internal trochlea extends out farther

medially and posteriorly in P. astrictocarpus and

in P. palmeri than in P. pusilla, making the distal

end wider. The medial side of the hypotarsus is

strongly excavated in P. astrictocarpus, even more

so in P. palmeri, and less so in P. pusilla. Of the

seven ossified tendons associated with the type tarsus, five, from their location before removal, are

known to represent the tendons of M. extensor

digitorum longus (strongly ossified and triradiate

distally), M. flexor hallucis longus, M. flexor digitorum longus, M. flexor perforatus digiti 11, and

M. flexor perforatus digiti in. The other two are

probably of M. flexor perforans et perforatus digiti

in, and M. flexor perforatus digiti iv.

Extant Rails

THE RESIDENT Gallinula.—The presence of the

Common Gallinule (Gallinula chloropus) on St.

Helena was recorded as early as 1715 by Beeckman

(in Gosse, 1938:140). Melliss (1870) describes a

bird, undoubtedly of this species, that was captured in Lemon Valley. Kinnear (1943) reported

a specimen from Fisher's Valley and referred it to

the African subspecies G. c. meridionalis. Benson

(1950) mentions Kinnear's record but did not see

the species himself. A single bird and a pair with

young were seen by Haydock (1954:69) in Fisher's

Valley and he mentions others seen in James Valley. The Fisher's Valley stock he says, "have, according to reports, only been there some eight

years," but I am inclined to doubt this seriously.

Under the name Gallinula angulata (a lapsus for

G. chloropus) Loveridge (1964:430) relates that this

species "is now known to nest in Sandy Bay and

elsewhere," and informed me (in litt.) that the

birds have been a constant feature of Fisher's Valley since his arrival on the island in 1957 and that

he has seen a nest. Basilewsky (1970) noted the

species at Bradley's Ruins (lower Fisher's Valley)

and less frequently in James Valley.

I found this species abundant throughout the

length of Fisher's Valley, the marshes and sodden

yam patches of which I never traversed without

seeing and hearing at least a dozen. I also heard

them calling from the bottom of Lemon Valley.

As a nesting bird it is well known to the islanders

who call it "waterduck" or "waterhen" and I was

told of its being common in Sandy Bay Valley and

of an individual seen at Lemon Tree Gut. The

species surely occurs throughout the island wherever there is suitable habitat. During my stay on

the island I heard persistent and repeated rumors

from a number of sources that another, similar

species of bird with fully webbed feet also occurs

on the island. Although skeptical I offered a substantial reward for a specimen, but I had no takers.

I am quite satisfied that such a bird is imaginary.

The legend may have arisen as a result of seeing

the Gallinula swimming.

Four gallinules from Fisher's Valley that I col-
NUMBER 152 21

lected, in their small size and dark coloration, agree

well with the African race G. c. meridionalis. There

has been no decrease in flying ability, as the birds

often took to flight readily and flew strongly. Considering the present populations of humans, dogs,

and cats on the island, any trend towards flightlessness would no doubt be of great disadvantage.

Gallinula chloropus on St. Helena is definitely a

well-established, self-introduced, breeding bird.

ERRANT SPECIES OF Porphyrula.—Two species of

purple gallinule have occurred on St. Helena as

vagrants. The first record of the genus from the

island is an immature specimen of the African

species Porphyrula alleni, collected July 1938 and

reported by Kinnear (1943). I have seen this specimen and can confirm that it was correctly identified. Loveridge (1964) mentions six occurrences of

immature Porphyrula on St. Helena between 1959

and 1964. Two of these were identified from photographs by R. E. Moreau as P. alleni. Another

individual (taken June 1964 in Jamestown), also

identified as P. alleni, was preserved as a skeleton

and is now in the collections of the Museum of

Comparative Zoology (MCZ 5046). On measuring

this specimen, however, I find it is too large for

P. alleni (e.g., tarsus 60.2 mm) and it must therefore be referred to P. martinica. This is further

corroborated by my collection of an immature individual of P. martinica on 10 June 1971 in Fisher's

Valley (Olson, 1972).

As at Ascension, it is now certain that both species of Porphyrula occur at St. Helena. The records from both islands have nearly all been of

subadult birds that appeared between May and

September. Loveridge was under the impression

that P. alleni might be breeding on St. Helena,

but there is no evidence for this and I feel quite

certain that no Porphyrula breed on any of the

South Atlantic islands (see below).

Haydock (1954) discusses a bird that he saw on

St. Helena that he thought to be Porzana porzana.

Although possible, in the absence of a specimen

the record is best considered questionable.

Environment and Lives of the Rails

St. Helena provided a much more equable environment for terrestrial birds than Ascension. It

is larger (122 km2; 47 mi2) and displaced farther

eastward and thus closer to West Africa than is

Ascension. The oldest rocks from the island have

been dated at 14.3±1.0 million years (Baker, 1970)

so it is also considerably older than Ascension.

A rugged island, entirely volcanic in origin, St.

Helena juts up abruptly out of the sea and is characterized by steep cliff faces and deeply dissected

valleys. Access to the sea is limited to a few valley

mouths. Melliss (1875:221) quotes the noted

botanist Hooker as saying that the island "when

discovered . . . was entirely covered with forests,

the trees drooping over the tremendous precipices

that overhang the sea." This must be to a certain

extent an exaggeration of the facts. Today, much

of St. Helena is barren and arid. The areas below

500 meters (1500 ft) receive little rainfall (Jamestown, near sea level, averages a little over 200 mm

per year) and there is no reason to assume that

they were much wetter in the immediate past.

That there are a number of endemic invertebrates

and one endemic species of bird that are adapted

to these open, arid areas argues convincingly

against the entire island having been covered with

forest in the past. However, the areas above 500

meters, the "green belt," receive nearly four times

as much precipitation and were once well vegetated with many endemic plants (Decelle, 1970).

There are abundant clear streams of fresh water

originating in this higher portion of the island.

After the discovery of St. Helena in 1502, man

systematically set about his usual destruction. The

forests were decimated by goats and by cutting for

timber and fuel for lime burning. Hogs, rats, cats,

and mice set upon the native avifauna, extirpating

about 15 species. Today only two native landbirds

(counting Gallitiula) and six seabirds breed on the

island and offlying rocks and the native vegetation

is reduced to a small area on the central ridge,

which is fast being encroached upon by introduced

species of plants. With the destruction of the native vegetation, a number of species of endemic

land snails also became extinct.

Unlike Atlantisia elpenor, there is no written

record of either A. podarces or Porzana astrictocarpus. We can only guess at what their niches might

have been. In contrast to the Ascension rail, the

St. Helena rails shared their environment with

other landbirds, for on the island there were at

least a plover, a dove, and a large species of hoopoe

present in addition to the rails (Olson, in prep,

(b))-
22 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

St. Helena supports a much larger and richer

fauna of terrestrial invertebrates than Ascension.

This fauna was extensively collected by members

of the Musee Royal de L'Afrique Central, Tervuren, Belgium, the first of several volumes of their

results having already appeared (e.g., Basilewsky,

1970). In addition, the island once was a major

breeding station for thousands of seabirds—almost

all of which have now been extirpated. There were

probably at least six species of shearwaters and

petrels, two frigatebirds, boobies, and Sooty Terns

breeding in large colonies on the mainland (Ashmole, 1963b; Olson, in prep. (b)). As on Ascension,

these immense seabird colonies would have provided

a veritable cornucopia for rails, and at least Atlantisia podarces, by virtue of its large size, would

have been well equipped to turn this source to its

advantage. The Porzana, like its counterpart on

Laysan, also may well have taken sustenance from

the seabird colonies. Another prime source of food

would have been the diverse fauna of pulmonate

snails formerly found on the island. Wollaston

(1878) lists about 20 species of land snails in 5

genera, most of which are known only from subfossil remains. Snails are a favored food item of

many continental rails and seem to be especially

preferred by members of Porzana. They very likely

were taken by P. astrictocarpus. Some of the St.

Helena snails were far too large to be utilized by

P. astrictocarpus but may well have been preyed

upon by A. podarces. The great disparity in size

of the two rails would have precluded much overlap in their respective food items.

Two morphological adaptations of A. podarces

seem to be directly correlated with the nature of

the island's terrain. St. Helena is possessed of many

valleys that are exceptionally deep and precipitous.

A. podarces, being a large and heavy flightless bird,

would likely have had difficulty getting out of such

steep-sided, rocky ravines. But as we have seen,

compared to other large flightless rails from islands

with more even terrain, A. podarces has proportionately better developed wings (Table 3) and

much longer claws on the toes (Plate 6a). These I

believe may have been adaptations for climbing

and fluttering up the valley walls. In the National

Zoological Park in Washington, I have seen the

African rail, Limnocorax flavirostra (ordinarily a

\ery aquatic species), scale a nearly vertical rock

lace, accomplishing this feat with much fluttering

of its wings, although never actually flying. Hagen

(1952:197) observed that Atluntisia rogersi used

its wings "as brakes when jumping down small

declivities," and one in captivity climbed tussock

stems "fluttering with the wings to aid the climbing." Atlantisia podarces probably used much the

same technique. Porzana astrictocarpus, weighing

approximately yi6 as much as A. podarces, would

not have been in as much need of pronounced

climbing adaptations.

The extinct rails of St. Helena would have had

but very few natural enemies. Frigatebirds may

have presented a possible, but not too likely, hazard

to chicks of either species or even adults of the

Porzana. On the other hand, A. podarces, being of

such large size, very conceivably may have consumed both the young and eggs of P. astrictocarpus

on occasion. Although there is no direct proof of

the cause of the extinction of the two endemic rails

of St. Helena, there can be little doubt that they

survived up until man's arrival whereupon they

succumbed to predation by man and his domestic

animals and to their respective destruction of the

habitat.

The establishment of Gallinula chloropus is an

obviously recent event which probably did not occur until after man's coming. First of all, the nature of the marshy vegetation in the valleys it now

occupies is the result of changes brought about by

man and livestock. For instance, E. L. Jackson

(1905:26) informs us that "shortly after the establishment of the colony [ca 1660] a species of yam

had been introduced from Madagascar. Planted in

the valleys it throve wonderfully well, as it requires

a constant soak of water . . ." Today this yam is

one of the dominant plants of the marshy valley

bottoms and its growths are the constant resort of

gallinules. Secondly, had the gallinules attempted

to colonize the island prior to the extinction of A.

podarces, they most likely could not have competed successfully against such a well-established

and adapted species. The recency of the arrival of

Gallinula chloropus is testified to by the fact that

it does not sensibly differ from the African mainland form and by its total absence from the fossil

record.
NUMBER 152 23

RAILS OF THE TRISTAN DA CUNHA GROUP AND GOUGH ISLAND

In the remote Tristan group, consisting of the

three associated islands of Tristan da Cunha, Inaccessible, and Nightingale, and on Gough Island,

removed some 400 km SSE of Tristan, two vagrant

and three endemic forms of rails are known. Although I have no new information concerning

these birds, a short synopsis of them is included for

the purposes of later discussion.

Easily the most interesting of the Tristan rails

is the minute, flightless, Atlantisia rogersi, confined entirely to Inaccessible Island. A rail said to

inhabit Inaccessible was described to members of

the Challenger expedition in 1873 but they did not

encounter it (Moseley, 1879). Nor was the

Shackleton-Rowett expedition able to secure specimens of it in 1922 (Lowe, 1928:101). Not until

1923 did specimens collected by Rev. H. M. C.

Rogers, then resident chaplain on Tristan, arrive

at the British Museum where they were examined

by Percy Lowe and briefly described as a new genus

and species, Atlantisia rogersi, in honor of Rev.

Rogers (Lowe, 1923). Lowe later (1928) gave a

rather comprehensive treatise of the species, including anatomical notes and a color plate. The dark

brown and black plumage of A. rogersi is fluffy

and decomposed, appearing almost hairlike. The

adults are variably barred with white or buffy on

the flanks, thighs, wing coverts, scapulars, secondaries and even in the distal parts of the primaries,

while the juveniles are entirely dark (Hagen,

1952). The iris is red in adults and dark brown

in juveniles.

A fairly complete account of the life and habitat

of this species has been given by Hagen (1952),

and additional comments rendered by Elliott

(1957). Uninhabited Inaccessible Island is small

(12 km2) and is about 40 km removed from the

main island of Tristan and 22 km from Nightingale. It is well vegetated, especially with dense

fern and tussock-grass (Spartina arundinacea). In

the past it has suffered somewhat at the hand of

man and at one time was said to have been overrun with wild pigs and goats as well as being fired

by sealers. By 1937, however, there were only seven

sheep and one pig on the island, rats and mice apparently not having reached it (Hagen, 1952:210).

The rails appear not to have been detrimentally

affected. Hagen (1952:197) estimated the population of A. rogersi at around 1200, but Elliott

(1957:578) felt that this was much too low and that

the figure would lie somewhere between 5000 and

10,000. The rails are found in small groups

throughout the island in the dense fern and tussock growth, and communicate by various twittering trills. Three stomachs examined by Hagen

contained seeds, berries, and insects. Atlantisia

rogersi is not known to feed on the eggs or regurgita of seabirds even though Inaccessible is the

breeding station for thousands of petrels and penguins. The rails are preyed upon, one being recovered by Hagen from the stomach of a Skua

(Catharacta), but such predation is probably not

significant.

The first rallid described from the Tristan group

was a gallinule "closely allied in general aspect to

our Common Water-hen (G. chloropus), though

readily distinguishable on accurate comparison"

(P. L. Sclater, 1861:260). P. L. Sclater received

specimens of this bird in 1861 "brought from the

island of Tristan d'Acunha to Cape Town by a

person formerly in the service of Sir George Grey"

the then governor of Cape Colony who forwarded

the birds (skins, specimens in spirits, and a living

example) to London. The species was described as

being slightly larger than Gallinula chloropus, with

darker plumage, heavier legs and pelvis, reduced

wings and sternum, and stouter bill, and was given

the name Gallinula nesiotis by Sclater.

A similar bird was later collected on Gough

Island, over 400 km from Tristan, by George Comer. This was described as a new species, comeri,

by Allen (1892) who erected for it and nesiotis the

genus Porphyriornis, based solely on the shape of

the bill and the heaviness of the feet. Ripley (1954)

quite justifiably sank Porphyriornis into Gallinula

and considered comeri merely as a subspecies of

nesiotis. Rand (1955), who saw no specimens, followed suit in the latter decision but was ambiguous

about whether the species may have been derived

from Gallinula, Porphyrula, or Porphyrio (let me

emphatically interject here that the latter two

genera have no close relationship to the TristanGough birds) and he maintained the genus Porphyriornis. Voous (1961) and especially Eber

(1961) have given comprehensive accounts of the

Gough bird, comeri, both concluding that the spe-
24 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

cies was clearly derived from Gallinula stock and

should be included in that genus. With this there

can now be little dispute.

Eber (1961:254), however, felt that it was wholly

improbable that two such similar flightless species

as G. nesiolis and G. comeri could develop on

islands so distant from one another. Because no

specimens were taken on Tristan after 1861 and

because of the "round about way" (Umweg) that

the original specimens reached Sclater, Eber concluded that the original specimens of G. nesiotis

actually came from Gough Island and that the species never existed on Tristan (thereby making

comeri a junior synonym of nesiotis). But, what

Eber overlooked or disregarded were the several

early accounts of the island of Tristan that mention a flightless gallinule.

Beintema (1972) has presented a thorough summary of the old accounts of gallinules on Tristan,

and a review of the history of extant specimens

attributed to G. nesiotis. A report of a gallinule

on Tristan earlier than any cited by Beintema may

be found in Pike (1873:34) who mentions the visit

of a Captain Patten from the sealer Industry who

stayed on Tristan from August 1790 to April 1791

and described there "a bird something like a partridge, only it is black, and cannot fly" as being

"abundant." The accounts of Lambert (cf. Holdgate, 1958:19), Carmichael (1818), Earle (1832),

Stirling (in Stoddart, 1971), and Gurney (1853)

establish beyond doubt that a gallinule was resident on the island of Tristan da Cunha and was

common enough to have played a fairly important

role in the diet of the islanders.

In his study of the gallinule specimens allegedly

from Tristan, Beintema (1972:112) concluded that

only the skin of the type of G. nesiotis and two

incomplete skeletons could be considered as definitely having been taken on Tristan rather than

on Gough. He could find no external differences

between G. nesiotis and G. comeri but reported

that the smaller sterna and pelves of the two skeletons of G. nesiotis indicated a bird of "much less

heavy build" than G. comeri. He felt that the two

forms "obviously belong to the same species, Gallinula nesiotis Sclater (1861)" (Beintema, 1972:107).

What is known of the disappearance of G. nesiotis, late in the 19th century, is documented by Beintema (1972) and is presumed to have resulted

from the combined depredations of cats, rats, man,

and dogs. On the other hand, G. comeri on uninhabited Gough Island, still exists and in good

numbers, despite a large population of introduced

mice. Holdgate (1958) has given an account of this

species in its native haunts. It is an inhabitant of

the forest and tree-fern zones of the island but not

the open mountain areas. Elliott (1957:579) also

found the birds "very common in the boggy areas

bordering the Glen" and observed them feeding

on grass heads. Like Atlantisia rogersi, the Gough

Island gallinule probably finds its only natural

enemy in the skua.

The peregrine Porphyrula martinica once again

is known as a regular vagrant to Tristan da Cunha.

Rand (1955) has summarized numerous records of

this bird, all apparently from the main island of

Tristan. Voous (1962:110) adds another record, describing the species as a "regular visitor." As at

Ascension and St. Helena, the birds are mainly

immatures and occur during the northern spring

and summer. The species is of such regular occurrence on Tristan that the natives even have a

vernacular name ("guttersnake") for it (Hagen,

1952:201). There is no evidence of its breeding on

the island, however.

W. L. Sclater (1911:94) discusses a specimen of

what he describes as a quite young coot "very

closely allied to Fulica armillata and F. ardesiaca

from South America, though it presented some differences from those species," as having been obtained by a "Mr. Keytil" [sic] and forwarded to him

by the director of the South African Museum. It is

this same specimen that is referred to by Winterbottom (1958) as Fulica armillata and said to have

been collected on Tristan and received from Keytel

by the South African Museum in 1910. Winterbottom (in litt., to G. E. Watson, 21 Feb. 1972) reports

that this specimen is currently under study by

Beintema and "that it is an immature of one of

the South American coots (definitely not F. americana . . . , though armillata is one of the possibilities)."
NUMBER 152 25

ORIGIN AND EVOLUTION OF THE SOUTH ATLANTIC RAILS

. . . imprison'd in the viewless winds,

And blown with restless violence round about

The pendent world.

Shakespeare

Measure for Measure

Act HI, Sc. 1

The various facts previously outlined may be

coordinated to arrive at a coherent explanation of

the origins and relationships of the different groups

of South Atlantic Rallidae. Each group contributes

something different to this explanation and a fairly

logical progression of ideas obtains. The distribution and status of the South Atlantic rails may be

summarized as follows:

Ascension Island

Allantisia elpenor (extinct endemic)

(iallinula chloropus (vagrant)

Porphyrula martinica (vagrant)

Porphyrula alleni (vagrant)

St. Helena Island

Atlantisia podarces (extinct endemic)

Porzana astrictocarpus (extinct endemic)

Gallinula chloropus (abundant breeding resident, recent

colonizer)

Porphyrula martinica (vagrant)

Porphyrula alleni (vagrant)

Tristan da Cunha group

Atlantisia rogersi (resident endemic, Inaccessible Island)

Gallinula nesiotis (recently extinct endemic, Tristan)

Porphyrula martinica (regular vagrant, Tristan)

Fulica sp. (rare vagrant, Tristan)

Gough Island

Gallinula comeri (resident endemic)

Genus Porphyrula

The genus Porphyrula consists of three species.

One of these, P. flavirostris, is a small form confined to South America. It does not assume the

dark purple adult plumage of the other two species

and does not seem to be given to oceanic wandering. Porphyrula martinica breeds from southern

United States to northern Argentina and migrates

out of the northern parts of its range in the winter. The species is a great wanderer. As we have

seen, it is known as a more or less regular vagrant

to Ascension, St. Helena, and Tristan da Cunha. It

has also been recorded as a vagrant to Bermuda

(Bradlee and Mowbray, 1931), the island of South

Georgia (Pereyra, 1944), the Falkland Islands

(Bennett, 1935), the Azores (Bannerman and Bannerman, 1966), the Scilly Islands (Anonymous,

1960), the Galapagos (LeVeque, Bowman, and Billeb, 1966), the Pacific Ocean between the South

American continent and the Galapagos (Castro

and de Vries, 1970), and Clipperton Island in the

Pacific (Ehrhardt, 1971:478). There have been no

less than 12 records of this species from South

Africa, all but two of which were immatures (for

the most recent record and summary of references,

see Broekhuysen, 1971). The similar but slightly

smaller P. alleni, which might be considered as

forming a superspecies with P. martinica, breeds in

Africa south of the Sahara, and Madagascar, and

is known to wander to southern Europe, islands in

the western Indian Ocean and Gulf of Guinea

(Peters, 1934), Denmark (Knudsen, 1930), the

Azores and probably Madeira (Bannerman and

Bannerman, 1965), as well as Ascension and St.

Helena.

Porphyrula martinica and P. alleni illustrate excellently the propensity of rallids successfully to

cross large stretches of open sea and arrive safely

at remote oceanic islands and even different continents. Why rails should be so particularly predisposed to such peregrinations I cannot say. As a

number of species are migratory and fly quite well,

it seems improper to cite a weak flying ability being responsible as is usually done; yet it is probably

true that most rails would be unable to overcome

much of a headwind and would be carried along

with little choice of direction once "imprison'd"

in the wind until reaching land. The ability to

land, rest on the water, and take off again would

increase their chances of success over those of most

purely terrestrial birds.

Now we have seen that two species of Porphyrula

have arrived at a good many islands, often in sufficient numbers, one would think, to establish

themselves as breeding residents. Yet nowhere on

a remote oceanic island has Porphyrula established

breeding populations nor given rise to endemic

flightless forms. Quite in contrast, Gallinula

chloropus has successfully colonized many oceanic

islands; e.g., St. Helena, the Azores, Seychelles,

Mariannas, and Hawaii to name some of the more
26 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

striking examples, and given rise to flightless forms

on Tristan and Gough. What is responsible tor

this pronounced difference in adaptability?

Porphynda normally inhabits bodies of water

covered with floating vegetation. It is on this insecure substrate that the birds spend most of their

lives, rarely swimming or traversing solid ground.

To this specialized existence they are accordingly

modified in morphology and behavior. Compared

to Gallinula, Porphynda has much longer toes and

the elements of the hind limb are proportionately

longer and more slender; the ctiemial crests of the

tibiae are reduced; the distal part of the fibula, to

accommodate the enlarged M. peroneus brevis, is

troughlike rather than a mere splint; the shaft and

medial hypotarsus of the tarsus are greatly excavated to accommodate the better developed intrinsic muscles and the highly ossified flexor and

extensor tendons; and the inner trochlea is markedly lower and in nearly the same plane as the

outer. These modifications are all associated with

support and locomotion on floating vegetation. In

Porphyrula the ribs are pneumatic, whereas in

Gallinula they are not; the significance of this is

not clear. The skull of Porphyrula is strong, the

bill short and heavy, the nostril small and the jaw

muscles much better developed; all probably in

accordance with such feeding habits as pecking

open lotus pods (Olson, 1963) and birds' eggs

(Beadel, 1946). In summary, Porphyrula (and the

closely related but much larger Porphyrio, which

has similar modifications) is much more specialized

than Gallinula, which latter does not differ in any

notable aspect from the basic rallid structure.

None of the species of Porphyrula appears to

vary geographically either in size or coloration. On

the other hand, Gallinula chloropus, throughout

its nearly cosmopolitan range, varies considerably

in size and to a lesser extent in coloration. In

addition, G. chloropus appears to be more variable

individually than Porphynda martinica. To test

this I measured the following elements of 13 Gallinula chloropus (5 males, 8 females) and 10 Porphyrula martinica (5 males, 5 females): cranial

width; pelvic width; lengths of coracoid, scapula,

humerus, ulna, carpometacarpus, femur, tibia, and

tarsus. All of the specimens were from Florida and

;ill but two of the former species and one of the

latter were collected in the same locality on the

same date. For each of these ten measurements,

the coefficient of variation was higher in Gallinula

(average 4.99) than in Porphyrula (average 3.31).

Although an inadequate sample size, the data seem

to indicate less individual variability in size in

Pmphyrula.

My contention is, therefore, that Porphyrula, because of its lessened variability and specialized

structure and habits, is not genetically plastic

enough to adapt itself to the drastically different

environments encountered on small oceanic islands,

whereas the generalized and variable Gallinula is.

The possibility remains that Porphyrula has not

been able to establish itself because of competition

with existing or incoming populations of Gallinula.

This again, however, would be a reflection of the

more specialized nature of the former. Of all the

purple gallinule group, only the Takahe of New

Zealand (usually placed in the genus Notornis but

more realistically considered only a large flightless Porphyrio) has become flightless and cursorially adapted, but this occurred on a very large

island with a much more diverse environment.

It is appropriate to suggest here that the generalized nature of the family Rallidae as a whole

is quite likely one of the main factors for their

adapting so well to so many different island situations. Only a few genera possess well-marked morphological specializations for feeding or locomotion

and the family is basically a homogeneous one. In

food habits, great variability is shown within most

species. Unlike other groups which reach remote

islands (e.g., herons or shorebirds), rails are better

equipped to respond to new habitats and food

sources. Porphyrula is a notable exception.

Another perplexing circumstance presented by

Porphyrula in the South Atlantic is the matter of

P. martinica turning up at St. Helena and Ascension. On both of these islands the tradewinds blow

strongly from the southeast (Figure 1), so only the

African P. alleni would be expected to occur.

Other vagrants to Ascension and St. Helena have

been of African or at least Old World origin and

at least two of the endemic landbirds of St.

Helena, the plover and the hoopoe, are definitely

of African derivation, and the Gallinula is of the

African race. On Ascension a number of observers,

beginning with some of the island's commandants

and including Lesson and Darwin (cf. Daly, 1925),

have commented on the lack of symmetry of many

of the island's volcanic cones. In every instance
NUMBER 152 27

the windward (southeast) slope of these cones is

the steeper, indicating that the southeast trades,

which caused the more rapid buildup of cinder

and ash on the leeward side of the cones, have

been in effect probably since the island's emergence. The same holds true for St. Helena where

similar phenomena have been observed (Baker,

1970). If then, the trades are now and always have

been blowing from the direction of Africa, how

do we explain the occurrence of an American rail

on these islands? I have already proposed two

possible hypotheses (Olson, 1972): either P. martinica are wafted along on the westerly winds in

the southern part of the South Atlantic until they

approach the coast of Africa, where some are

picked up on the southeast trades and blown

back out to Ascension and St. Helena; or, the

birds are arriving at these two islands on westerly

winds above the shallow tradewind layer. Whatever the explanation, the case of Porphyrula

demonstrates that the islands of the mid-South

Atlantic could be colonized by rails arriving from

either Africa or South America.

Genus Gallinula

Like Porphyrula, members of the genus Gallinula have also reached all the mid-South Atlantic

islands. Gallinula chloropus is known only as a

vagrant to Ascension and I imagine that this island

is simply too austere and lacking in resources ever

to have sustained a population of a rail species

of this size. On St. Helena we find the African

subspecies G. c. meridionalis an abundant breeding resident of the lush, moist, valley bottoms

throughout the island. Its settlement of this island

is probably quite recent, as it has not differentiated

from the mainland stock. Lack of competition from

the now extripated Atlantisia podarces, and man's

modification of habitat are probably the factors

allowing it to colonize successfully where it could

not have done so before.

On Tristan da Cunha, and 400 km away on

Gough Island, are two forms of flightless gallinule.

If, as by most current taxonomic practices, these

are considered as subspecies of the one species,

Gallinula nesiotis, then this implies that one form

was derived from the other. Yet clearly both now

are incapable of flying between islands. The difficulty of reconciling this situation is what tempted

Eber (1961) into trying to explain away the Tristan

gallinule. On the other hand, Eber correctly contends that the differences between the flightless

Gough Island gallinule and Gallinula chloropus

are not much greater than exist between the

various races of G. chloropus. The main structural

differences are the heavy legs and pelvis, reduced

wings and pectoral girdle, and stouter bill. Both

adults and immatures of the flightless gallinules

are darker than the corresponding plumage of

typical G. chloropus. This, Eber attributes to

higher humidity on the islands where the flightless

forms are found, which may well be the case. Also,

it may be observed that there is a tendency towards

increased melanism of several of the races of G.

chloropus and that G. tenebrosa of the Australian

region—an obvious derivative of G. chloropus

stock—is almost totally black.

It is, of course, possible that the population of

one island became modified along the lines of

present day G. nesiotis and colonized the other

island before having become flightless, although

the direction of the prevailing winds does not

favor this hypothesis and there is no evidence

among the other land birds of communication

between Tristan and Gough. I suggest that the

ancestors of both the Tristan and the Gough

gallinules were volant Gallinula chloropus that

probably arrived at their respective islands from

South America. The prevailing winds in the

Tristan-Gough area are from the west and all the

vagrants there, and all the resident birds whose

ancestry is apparent, are South American or New

World in origin. I do not think it is necessary to

invoke a "Gallinula chloropus-like ancestor" for

either G. nesiotis or G. comeri. Both of these

flightless populations could easily have been derived from the existing species G. chloropus. Flightlessness, and its correlated adaptations, is easily

and quickly evolved and is in itself not a useful

taxonomic criterion. I believe that G. nesiotis and

G. comeri have evolved in parallel from separate

colonizations of flying G. chloropus and are phylogenetically more closely related to that species than

to each other. Plumage darkening and Sightlessness

probably involve a minimal amount of genetic

change. The islands of Gough and Tristan present

very similar ecological conditions, so it is not difficult to imagine that selection on a single stock

would proceed much differently on one island
28 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

than on the other. Therefore, what we see is two

forms on separate islands that have evolved features

different from the parent stock but that are essentially identical to each other. This is similar

to the rail Dryolimnas cuvierii which has a volant

population on Madagascar with nearly identical

subspecies on Assumption Island, Aldabra Island,

and Astove Atoll at least one of which (Aldabra)

is flightless.

Eber (1961) has shown that in captivity the

Gough gallinules (G. comeri) are markedly aggressive towards G. chloropus and speculates that

this would probably act as an isolating mechanism

between the two forms. This being the case, the

Gough bird would be a species separate from G.

chloropus and should be known as Gallinula

comeri, while the Tristan bird, having evolved independently of G. comeri, should be known as

Gallinula nesiotis. Apart from the behavioral

differences (if valid), it might be more realistic

to consider G. nesiotis and G. comeri as welldefined flightless subspecies of G. chloropus.

Why other insular populations of G. chloropus

have not become flightless is difficult to say; perhaps conditions of predation and habitat would

not allow it. That there are no gallinule populations on either Nightingale or Inaccessible may

possibly be correlated with the small size of these

two islands.

Genus Atlantisia

With Atlantisia we come to the most interesting

group of rails in the South Atlantic. The genus

is confined to the islands of the southern midAtlantic ridge and is distinct from any genus found

on either mainland. Up until now, A. rogersi was

the only recognized member of the genus. Lowe

(1928) theorized that rails were either primarily

or secondarily flightless and considered A. rogersi

as belonging to the first category (i.e., evolved

from non-flying ancestors) and postulated that its

ancestors arrived at Inaccessible Island on foot

over extensions of continental land masses—an

unnecessarily elaborate explanation and one that

has nothing to support it. Stressmann (1932) has

effectively shown that the emphasis Lowe placed

on the degenerate plumage structure of A. rogersi

is of little phylogenetic importance. Other major

structural adaptations of A. rogersi are correlated

with flightlessness, do not differ greatly from other

flightless rails, and are of no bearing on phylogeny

(see below). There is no reason to believe that

the ancestors of A. rogersi and the other species of

Atlantisia did not arrive at their islands as windblown strays from continental areas, just as other

species of rails still do.

Lowe suggested several possible relatives of

Atlantisia rogersi, his choices being based entirely

on their having dark plumage like A. rogersi.

Hagen (1952:231, fig. 52) reiterated Lowe's suggestions, showing these species on a map encaptioned with unjustifiable certainty "geographical

position of rails related to Atlantisia." The species

shown are Laterallus spilonotus, L. jamaicensis,

Porzana spiloptera, P. tabuensis, Limnocorax

flavirostra, and fortuitously enough, "Ascension

rail" based on Kinnear's 1935 paper. My comparisons of the species of Atlantisia with other rails

have shown that this group has no affinities with the

crake-like genera Porzana, Laterallus, and Limnocorax. Lowe himself did not think that Limnocorax

was a very likely progenitor of Atlantisia and in a

flash of perspicacity wrote (1928:105) that the former "may represent an early phase of the Porphyrio

group." While Limnocorax does not represent an

"early phase," it has ^acquired some similar structural adaptations in the hindlimb to the PorphyrioPorphyrula group, probably through convergence

as a result of its inhabiting floating vegetation.

Examination of the osteology of Atlantisia reveals

that this genus is related to the "Rallus assemblage"

which includes Rallus, Hypotaenidia, and a few

other forms derived mostly from Hypotaenidia.

The relationships of this assemblage will be dealt

with in more detail elsewhere (Olson, in prep. (c)).

Hypotaenidia consists of generalized species with

rather stout heavy bills, pelves, and hindlimbs,

and is confined to Australo-Malaya and southern

Asia. Rallus, in the strict sense, is a group highly

specialized to a habitat of reedy marshes and its

species have much more slender and delicate bills,

hindlimbs, pelves, and sterna. Atlantisia falls between these two extremes and belongs with what

I have designated as a pro-Rallus group that has

as its only other known members Dryolimnas

cuvieri and "Rallus" pectoralis. The present distribution of this pro-Rallus group is quite evidently

relictual, with its species found only on the South

Atlantic islands, Madagascar and its offlying islands,
NUMBER 152 29

and on islands in the Australian region.

The ancestors of Atlantisia undoubtedly were

Hying species that came as wind-blown vagrants

from a mainland area. With pro-Rallus representatives on islands on both sides of Africa, it seems

certain that this stock must also have occupied the

continent at one time. From the African continent

probably came the ancestors of at least A. elpenor

and A. podarces. Pro-Rallus may also have been

in the New World where it possibly was replaced

by true Rallus. The specialized true Rallus then

invaded the Old World, replacing pro-Rallus on

the mainland and leaving pro-Rallus derivatives

isolated as insular relicts. Atlantisia rogersi may

have been derived from the New World pro-Rallus

or possibly from the same African stock that gave

rise to A. elpenor and A. podarces and that somehow got to Tristan "against the wind" as Porphyrula martinica is still seen to do on Ascension and

St. Helena.

It is conceivable that Atlantisia was derived

from a single species as given to wandering as the

gallinules are today. If I am correct in assuming

that Gallinula chloropus twice independently

gave rise to flightless populations that are virtually

indistinguishable, then why may not the ancestral

Atlantisia have done so thrice, the population of

each island responding to different ecological conditions by changes in body size? It is also possible

that Atlantisia may have been derived from two

closely related species from different continents that

arrived from different directions as Porphyrula

martinica and P. alleni do today; or from a single

species that inhabited both continents as we see

in Gallinula chloropus, which has also reached all

three of the islands inhabited by Atlantisia.

The size range in Atlantisia is extreme (Plate 10;

Table 2). No other genus of rails varies as much

in this respect. I would guess that A. elpenor is

closest in size to the original stock. Ascension probably could not have sustained a larger species and

a smaller species might have had difficulty utilizing

the available food. The geographical distribution

of size classes in Atlantisia does not follow Bergman's ecogeographic rule. If it did, one would expect to find the largest species in the coldest clime

(i.e., the nearly subantarctic Inaccessible Island)

where instead we find the smallest. The small size of

A. rogersi may be a factor of the very small size of

the island which it inhabits and possibly may have

been affected by the dense vegetation there which

might impede the progress of a larger bird. On

nearby Nightingale Island, which is still smaller

(4 km-'), we find no species of rail, which suggests

that island area may at times be a limiting factor in

establishing rail populations. The great size of A.

podarces on St. Helena may possibly be explained

by several factors. Of the islands inhabited by

Atlantisia, St. Helena is the largest, was ecologically the most diverse, and had the most abundant

sources of food and water, all of which would have

allowed an increase in size. There may also have

been selection for increased size in A. podarces as

a result of competition with another rail (Porzana

astrictocarpus), as A. podarces is the only member

of its genus definitely known to have shared its

island with another resident member of the same

family.

An object of speculation is the absence of an

Atlantisia from other South Atlantic islands. None

is known from the main island of Tristan. This

may be because of competition from the Gallinula

or there may have been a species of Atlantisia there

that became extinct before it could be discovered.

This, however, would not explain the absence of

an Atlantisia on Gough, which presumably has

not been exploited to the same extent as Tristan.

Likewise, the islands of Trindade and Fernando

de Noronha each may have harbored an Atlantisia

or at least some species of rail that was exterminated by introduced mammals before specimens

could be obtained. Search for subfossil remains on

these islands should prove of considerable interest.

Genus Porzana

The species Porzana astrictocarpus is the lone

member of its genus known from the South Atlantic islands, and, as mentioned, probably had its

origins in Africa. It is smaller than P. porzana, P.

Carolina, P. fluminea, P. fusca, P. bicolor, P. albicollis, P. olivieri, and P. paykulli and is larger

than P. spiloptera or P. flaviventer. The only

species near in size to P. astrictocarpus are P. tabuensis, P. parva, and P. pusilla. Porzana tabuensis

is slightly smaller than P. astrictocarpus and is

found in the Australo-Pacific region and thus is

not likely to be related to P. astrictocarpus. Porzana

parva is a rather uncommon migratory Palearctic

species that is known in sub-Saharan Africa only
30 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

from Ethiopia, Somalia, and Uganda. The closely

related and more abundant P. pusilla, on the other

hand, has a much wider distribution (Figure 6),

being found in Eurasia, Japan, Australia, and New

Zealand, and is known both as a migrant and

resident in much of sub-Saharan Africa and Madagascar. Because of its wide African distribution,

migratory nature, similar size and structure, P.

pusilla seems very likely to be the ancestor of P.

astrictocarpus.

On nearly the opposite side of the world from

St. Helena, on the island of Laysan in the Hawaiian chain, lived another small flightless crake,

"Porzanula" palmeri, that became extinct in the

late 1940s. Fortunately there are numerous specimens of both skins and skeletons of P. palmeri

available. This species has always been maintained

in the monotypic genus Porzanula and no one has

conjectured on its origins or relationships. Once

again, however, Porzana pusilla is a very probable

ancestor. P. palmeri differs externally from P.

pusilla in being slightly smaller, with shorter

heavier legs, much reduced wings, and in having

only eight primaries—all characters which are

correlated with its Sightlessness. The bill is longer

in P. palmeri, this probably being an adaptation to

different food.

The plumage patterns and color of P. pusilla

and P. palmeri are extremely similar. P. palmeri

always appears faded, probably as a result of nearly

continual exposure to the sun, but it is gray below

and brownish olive above with the centers of the

dorsal feathers black, just as in P. pusilla. The

plumage pattern on the heads of these two species

is practically identical. The flanks and thighs of

P. pusilla are barred with white and this barring,

although reduced, is present in P. palmeri as well.

The dorsal feathers of P. pusilla are streaked with

white and although this does not at first appear

to be the case in P. palmeri, there is yet a fair

FIGURE 6.—Breeding distribution of Porzana pusilla (shaded areas) and its two apparent

derivatives. (After Voous, 1960.)
NUMBER 152 31

amount of white streaking to be found concealed

amid the dorsal plumage of this species as well.

There is less white streaking in immatures of P.

pusiila than in the adults (Bauer, 1960) and the

reduction of white in P. palmeri could possibly be

a result of retention of this immature condition.

The juvenal plumage of P. palmeri is a pale buff

below, as is also found in P. pusiila.

The range of P. pusiila, extends along almost all

the western Pacific, from Japan to New Zealand

(Figure 6) and it is migratory in parts of this range.

With such evident ability for dispersal it would

be a prominent candidate for settling Laysan.

Vagrant birds of a number of species from both

Asia and America have reached the Hawaiian

Leewards (Clapp and Woodward, 1968) but the

New World holds no rail as similar in size or

appearance to P. palmeri as P. pusiila.

Thus we see that it is possible that one species,

Porzana pusiila, gave rise to two flightless insular

forms on opposite sides of the globe. I do not feel

that any of the characteristics of the Laysan rail

are of generic value and, therefore, the species

palmeri should be placed in Porzana. It is most

interesting that except for the wing elements, P.

astrictocarpus of St. Helena is almost exactly intermediate between P. pusiila and P. palmeri (Plate

11). This indicates that the direction of evolution

of the two insular species from a common ancestor

has been similar. That the Laysan rail has diverged

more from the original stock probably reflects the

increased selection pressure of its smaller and more

rigorous environment rather than a longer period

of adaptation.

I do not feel it is necessary to assume the caution normally used in speaking of ancestral forms

by referring to a "pro-Porzana pusiila" or a "Porzana pusilla-like ancestor" for the progenitor of

P. astrictocarpus or P. palmeri, because it is very

possible that the existing species of P. pusiila gave

rise to both. The time involved in achieving flightlessness and its correlated adaptations is probably

short (see following section) and selection on small

oceanic islands is doubtless rapid. We have seen

how rapidly man can alter the morphology of domestic animals by selective breeding, and the

selective pressures on small insular populations of

rails must be nearly as severe. Thus we could have

populations of Porzana pusiila on Laysan and St.

Helena, and of Gallinula chloropus on Tristan

and Gough, evolving into new flightless forms and

diverging to the point that some taxonomists would

erect separate "genera" for them, while the ancestral mainland populations are not appreciably

changing at all.

EVOLUTION OF FLIGHTLESSNESS IN RAILS

I have heretofore asked the question concerning Mauritius

henns and dodos, thatt seeing those could neither fly nor

swymme, beeing cloven footed and withoutt wings on an

iland far from any other land, and none to bee seence[sic]

elce where, how they shold come thither? Soe now againe

concerning the Ascention birds allsoe, thatt can neither fly

nor swymme. The iland being aboutt 300 leagues from the

coast of Guinnea . . ., the question is, how they shold bee

generated, whither created there from the beginning, or

thatt the earth produceth them of is owne accord, as mice,

serpentts, flies, wormes, etts. insects, or whither the nature

of the earth and climate have alltred the spape [shape] and

nature of some other foule into this, I leave it to the learned

to dispute of.

from the journal of Peter Mundy

(Temple and Anstey, ed., 1936:83)

In the above passage, italics are mine, to remind

the reader that Mundy's journal antedates Darwin

by some 200 years.

The story of evolution in the class Aves as a

whole has, from its beginning, been one of

adaptation for flight. Yet in a number of groups

this capacity has secondarily been lost. Prominent

among these is the Rallidae, roughly a quarter

of which living or recently extinct members have

lost the ability to fly. Why, and how, so many

species of rails and other birds have on so many

occasions so speedily renounced their heritage of

millions of years of aerodynamic refinements is a

subject of great interest. (Penguins and the nonvolant alcids should not be included in discussions of flightlessness. Their outstanding adaptations are for flying through a medium many times

denser than air and are much different from other

flightless birds; in a sense, these birds are the

best fliers of all.)

It need first be observed that all flightless rails

occur on islands, although these may vary greatly
32 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

from tiny, austere islets like Laysan, to large, rich

islands such as New Guinea and New Zealand. One

often reads that flightlessness comes about as a

result of the absence of predators, and while a

number of islands where flightless rails occur do

have avian predators, it is probably true that where

one finds flightless rails one does not encounter

native mammalian predators that are so destructive to ground-dwelling and nesting birds. Another factor of insular environments, as Holdgate (1965:370) has mentioned, is the reduced need

for dispersal ability. Continental rails usually live

in habitats that are discontinuous and widely

spaced, necessitating some capacity to get from one

area to another by flying, whereas most islands are

relatively small in area with mort homogeneous

habitat. But it should be emphasized that these

factors only allow flightlessness to occur and do

not explain why flight should be done away with.

Darwin (1866), in discussing the flightless beetles

of Madeira, suggested that selection for flightlessness occurred because flying beetles would be

wafted out to sea by strong tradewinds and thus

removed from the breeding population. This theory

has been invoked by other writers to explain the

flightlessness of birds as well, but as Darlington

(1943:39) indicates, this is a gross oversimplification, and I will go a step further and say that it

probably has had very little part in the evolution

of flightlessness in birds. Two arguments may be

made to dismiss the importance of the wind effect.

First, flightless birds are found on islands that are

large enough that winds could not be expected to

affect adversely any but the most coastal of airborne birds—a prime example being New Zealand.

Secondly, small land birds of various sorts which

are not flightless have evolved and thrived on many

small, remote, and wind-blown oceanic islands.

Witness the example of a thrush and three finches

in the Tristan and Gough group, and three small

passerines on tiny Laysan. On both of these islands

there are (or were) flightless rails. Some other explanation than wind effect must be put forth.

Holdgate (1965:371), in attempting to explain

flightlessness in organisms from the Tristan group,

stated that "flightlessness perhaps arises more for

negative than 'positive' reasons: if strong selection

pressure does not promote its retention, there is

a tendency for it to disappear." Brace (1963:45),

discussing structural reduction in evolution, concluded that "if the structure controlled by the locus

in question has no adaptive significance then it will

be reduced in the course of time." This, he believed, was independent of selection and was a

result of the generally deleterious effects of most

mutations. These suggestions carry vague overtones

of Lamarckian "disuse" and to me are not satisfying explanations.

Darlington (1943:44) probably comes as close

as anyone to solving the enigma of flightlessness in

remarking on carabids that "if flight becomes useless but not actually harmful, the advantage probably shifts directly to —winged [i.e. with reduced or

vestigial wings] individuals, not because they are

flightless, but because they are inherently better,

more viable insects, with simpler structure, simpler

metamorphosis, and lower energy requirements

than +winged [flying] forms," the seminal consideration, I believe, being the latter, i.e., reduced energy requirements. Increased viability

of flightless forms has been shown in weevils (D. J.

Jackson, 1928) but would probably be difficult to

demonstrate experimentally in birds. In their experimental studies of recolonization of defaunated

islands by invertebrates, Simberloff and Wilson

(1969) found that both weak and strong flying

forms were early colonizers but that weak flyers

were usually the first to produce large populations.

These observations, coupled with the fact that

flightlessness in rails has arisen time after time

and at a rapid rate, suggest that there are very

distinct advantages conferred by flightlessness and

that it is not merely a gradual fortuitous phthisis

of unused organs.

The most dramatic manifestation of flightlessness, of course, is the reduction of the whole pectoral apparatus, especially the large pectoralis

muscles. In adults of flying rails, the flight musculature ranges from 12 to 17 percent of total

body weight (Hartman, 1961:46). These figures are

low compared to many other birds, but this is still

a considerable proportion of the anatomy that is

involved only in flight. In terms of energy consumption, active muscle utilizes more energy than

any other tissue and the specialized and powerful

avian pectoralis is in turn probably one of the

most expensive of muscles to maintain. Any reduction in the flight muscles then, represents a potential energy savings relatively greater than a comparable reduction in almost any other organ.
NUMBER 152

Flight in birds has been attained through great

changes in metabolism and at great energy cost.

In an environment where a bird can get away

with being flightless, and when its feeding methods

will permit it, it is to the bird's advantage to become flightless. This is especially true where dispersal is not a problem, but where food resources

are generally limited. Obviously, of two competing

rails, the one with genetically reduced pectoral

muscles would require less food and could spend

more time engaged in reproductive activity, resulting in the perpetuation of its physiological

advantage. The whole direction of organic evolution and adaptation has as its underlying force

the more effective accumulation and budgeting of

energy. What more direct way to get ahead evolutionarily can there be than the elimination of a

costly energy drain when it is no longer needed

for the preservation of the individual? Another

factor that may be of importance is simply the loss

of weight incurred with the reduction of the

pectoral muscles. This would mean less mass to

be propelled and sustained by the hindlimbs and

would result in an advantageous shift of the center of gravity. In my opinion, the energy factor

is the overriding consideration in the evolution of

flightlessness and other factors are of secondary

importance. This may well be true of many structural reductions in other organisms. (It would be

of the greatest interest to compare the metabolic

rates and energy requirements of a flying and a

flightless rail, preferably congeners.)

It now remains to be seen how flightlessness

arises. Let us first examine some of the characteristics of flightless rails. The elements of the wing

and shoulder girdle and the sternum are reduced

relative to the size of the body and hindlimbs.

The depth of the carina sterni is reduced, often

drastically. The angle formed by the coracoid and

scapula is greater than 90 degrees. Correlated with

the reduction of the pectoral girdle is the reduction of the flight musculature. These, at least, are

the obvious distinctions. A more discrete manifestation of flightlessness in rails, is the reduction or

loss of the scapular tubercle for the attachment of

M. expansor secondariorum.

Now all this seems at first to be a rather complex set of characters that might involve a great

deal of genetic modification to accomplish. But I

think it can be fairly easily demonstrated that instead, there is a relatively simple basic phenomenon

responsible for these changes.

All rails are flightless during the beginning stages

of their ontogeny, and as chicks, all exhibit the

skeletal features that characterize adult flightless

rails. In Figure 7 are shown two young individuals

of the volant King Rail, Rallus elegans. The bird

on the left is 17 days of age (posthatching), the one

on the right is 47 days of age. The latter was

nearly adult size but for the purposes of comparison the figure has been reduced so that the femur

lengths of the two are equal. The differences in

proportions are immediately apparent. In the

younger bird, the bones of the wings and shoulder

girdle are much smaller, the sternum is reduced

and nearly keelless, and the coraco-scapular angle

is obtuse (also, the head is larger, and the ischium

has not fused posteriorly to the ilium; these differences will be discussed later).

It is obvious then, that if the proportions of

the skeleton of the younger rail were maintained

on into adulthood, the result would be a flightless

rail. Thus, flightlessness would not be a result of

numerous structural modifications, but a simple

retention of a state already present in the young

stages of every rail.

Lowe (1928:111) noted the "feeble development"

of the wing of young rails relative to the body and

legs, but did not exploit this observation to its

more obvious conclusion and instead, in trying to

justify his theory of "primary" versus "secondary"

flightlessness, suggested that "rails, as a group, may

in the past have been slow to acquire the power of

full flight, . . . while some . . . may never have

acquired it at all," and thus missed the point that

flightless species were merely recently evolved neotenic forms. The condition of the feathers of the

ostrich and of the palate of ratites in general, are

discussed by de Beer (1958) as examples of neoteny in flightless birds, but that the characters involved in flightlessness itself are a result of neoteny

seems to have escaped discussion. I shall confine

my remarks to the Rallidae.

In the proportions of young versus adult, or

flightless versus flying rails, we are dealing with

differential growth rates of various structures (allometry). Because of the large size of the hindlimbs at hatching, these structures probably

undergo positive allometry during the embryonic

development of rails, while the pectoral apparatus,
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

FIGURE 7. Cleared and stained skeletons of Rallus elegans: a, 17 days of age (posthatching);

b, 47 days of age (b is reduced so that the femur lengths of the two are equal) . Stippled areas

represent cartilage.

on the other hand, is negatively allometric or at

least grows much slower than the hindlimb during

this period, as has been shown to be the case in

the domestic fowl (Romanoff, 1960, appendix tables II and in). In flying rails, at some point in

their later development, these relative growth rates

must reverse, so that the wings and pectoral girdle

increase relative to body size (positive allometry)

while the hindlimbs remain the same or possibly

decrease. If this reversal in growth rates is arrested and not allowed to take place, yet all the

other normal processes of maturation proceed, the

result would be an adult rail that is as flightless

as the young. Eber (1961) has attributed the

skeletal differences between the flightless Gallinula

of Gough Island and the flying G. chloropus to differences in allometry of the various parts.

Flightlessness, then, does not involve the development of new structures, and the control of the

relative growth of the limbs is likely determined by

comparatively few genetic loci. It is easy to see

how very little genetic modification could rapidly

produce the seemingly drastic changes that mark

flightless rails. For this reason, flightlessness can

have only limited phylogenetic or taxonomic significance and cannot, for instance, in itself be used

as a generic character. Among other things, this

helps explain how we can have flying and flightless

races of a single species (as in Dryolimnas cuvieri),

how a flightless bird can be present on an oceanic

island less than a million and a half years old,

how the three isolated species of Atlantisia can all

be flightless and still retain so much similarity in

the rest of their structure, and how two "identical"

forms of flightless gallinules can evolve independently on islands over 400 km apart. The span of

time needed to evolve flightlessness in rails can

probably be measured in generations rather than

in millennia.

The development of the sternum is of considerable interest in the evolution of flightlessness. In

the ontogeny of the domestic fowl (Gallus), the

major bones begin ossification between about the

8th and 12th day of incubation. The sternum, however, does not begin to ossify until the 17th day

of incubation but is fairly well ossified at hatching.
NUMBER 152 35

Ossification of the sternum in the domestic pigeon

Columba livia, and the grebe Podiceps cristata,

does not take place until after hatching (Schinz

and Zangerl, 1937). In rails, ossification of the

sternum is also delayed. In Rallus elegans at hatching, ossification of all the major bones is "well underway with the exception of the sternum. At 17

days posthatching, the sternum is still only a

cartilaginous outline (Figure 7a), and at 47 days

it is only beginning to ossify (Figure 7b). This

postponement of sternal development may be one

of the factors that predisposes certain birds to

flightlessness. It is interesting to note that pigeons,

grebes, and rails have each given rise to flightless

forms, whereas the Galliformes, in nature, have

not.

At least in rails, even after ossification of the

sternum has begun, the cartilaginous outline of

the carina has still not reached its fullest development. In its early stages, the developing sternum

of flying rails goes through stages resembling the

ossified sternum of various flightless forms (Figure

8). Flightlessness as I have stated, is a case of

FIGURE 8.—Development of the sternum of a flying rail

to show how the carina in its early stages corresponds to the

shape of the carina in different species of flightless rails:

a, Porphyrula martinica, downy chick about a week old;

sternum entirely cartilaginous but has nearly the same

conformation as b and as Atlantisia elpenor. b, Gallirallus

auslralis, flightless rail, adult, c, P. martinica, immature

fully feathered but not quite volant; sternum is still partly

cartilaginous and now resembles d. d, Hypotaenidia owstoni,

flightless rail, adult, e, P. martinica, adult. Scales=5 mm.

Dotted lines indicate cartilage.

arrested development. Obviously, development

could be arrested at any point between hatching

and the flight-attaining stage, and the individual

would still be flightless. Evidently this is what has

happened throughout the Rallidae—different

flightless species have had their development arrested at different points—for in some flightless

forms the carina is greatly reduced and the remainder of the sternum markedly different from

flying forms (e.g., Atlantisia elpenor, Gallirallus),

and in others (e.g., Hypotaenidia owstoni, H.

wakensis) the carina is moderately developed and

the whole sternum, except for diminution in relative size, resembles flying species. This, in part,

is what deluded Lowe into thinking that rails could

be divided into primarily and secondarily flightless

groups. This is also why the sterna of such closely

related species as Atlantisia rogersi and A. elpenor

can differ so greatly while the remainder of the

skeleton does not. Therefore, the conformation of

the sternum of flightless rails is not a useful taxonomic criterion above the species or subspecies

level.

The obtuse angle formed by the coracoid and

scapula was early recognized as a characteristic of

flightless birds (Huxley, 1867; Parker, 1882). This

too appears to be a neotenic condition as an examination of Figure la should disclose. Although

I know of no published explanation for this condition, it appears that the decrease of this angle in

flying birds is a function of increased size of the

sternum and pectoral muscles and is a result of

this mass being brought under the bird's center

of gravity (Figure 76) to aid balance and probably

to confer mechanical advantage in flight.

As in most vertebrates, the skull is proportionately larger in the younger stages of rails (Figure

7) and is negatively allometric thereafter. There

is no evidence that neoteny has affected this relationship in flightless rails; i.e., flightless rails do

not appear to have larger heads than flying species.

In fact, the postembryonic negative allometry of

the skull is well illustrated by the comparative

proportions of the skulls of the three species of

Atlantisia (Table 3), where we see that while body

size increases, the skull does not increase at the

same rate.

Another condition of the skeleton of young rails

deserves mention. This is the lack of a posterior

fusion of the ischium and ilium (Figure 7fl). This
36 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

juvenile condition does not persist into the adult

stage of any known rail, even the neotenic flightless species. This condition of the pelvis, however,

is very similar to that found in some of the ratites,

especially the pelves of kiwis and moas. The implications of this go beyond the scope of this paper.

One last skeletal feature that is correlated with

flightlessness in rails is the reduction or loss of the

scapular tubercle for the attachment of the dorsal

ramification of the tendon of M. expansor secondariorum. The scapular tubercle appears to be

unique to the Rallidae and I have been unable to

find it in any other family. This tubercle is present in all volant rails but is variously developed.

In flightless species such as Hypotaenidia wakensis,

H. owstoni, Atlantisia rogersi, Gallirallus australis,

and Porzana palmeri, it is present but greatly reduced. In other flightless species, Atlantisia elpenor, Porzana astrictocarpus, and some specimens

of Tribonyx mortierii, for example, it is lacking

altogether. M. expansor secondariorum is most

peculiar in that it is composed of smooth muscle

fibers (Berger, 1956). Its function has never been

determined. The reduction or loss of the scapular

tubercle for its attachment in flightless rails implies

that it is in some way used in the process of flight.

CONCLUDING REMARKS

We have seen in the case of Atlantisia that it is

quite within reason to hypothesize that a single

species could have given rise to three entirely new

species, all flightless, and all on islands separated

from each other and the nearest mainland by vast

expanses of ocean. This is not without its implications to the origins of other species in other parts

of the world. For instance, the three Mascarene

islands of Mauritius, Rodrigues, and Reunion, in

the Indian Ocean, were all apparently inhabited

by very large flightless birds of columbiform ancestry (the Reunion bird is known only from

old descriptions). Despite the fact that suggestions

have been made to derive some or all of these birds

from rails (Storer, 1970), there is no good evidence

that the Dodo and Solitaire are anything but columbiform (Olson, 1971). It seems that what has

happened here is that a single stock of pigeon

colonized the three islands and that these populations then independently became flightless and

achieved large size. If a single stock of rails can

colonize islands as isolated as those of the midSouth Atlantic and give rise there to three flightless species, it seems only reasonable that the

Mascarenes, which are much closer to each other

and to the nearest mainland, could easily have

been settled by a single stock of pigeon that also

gave rise to three flightless species, at least two of

which subsequently evolved to the point of being

generically distinct.

The adaptability of rails is nowhere as well exemplified as in Atlantisia, for this single stock successfully established itself on a barren, tropical

desert island; a temperate, subtropical island of

varied vegetation; and a cool, densely vegetated,

temperate subantarctic island, all, of course, presenting very different environmental conditions.

The possibility that a single species (Porzana

pusilla) may have given rise to two flightless species

on islands on opposite sides of the globe is an example perhaps unparalleled in vertebrate zoogeography. With this group, as well as in Gallinula, I

hope that the idea that existing flightless insular

species may have been derived from other existing

volant species will not be too difficult for some

to digest, and I further hope that I have convincingly argued the ease and rapidity with which

flightlessness may be attained.

The known rails of the South Atlantic islands

illustrate more than their fair share of evolutionary and zoogeographical principles. It will be of

no small interest to find out what the future holds

in terms of paleornithological investigations of

other islands in that ocean.
NUMBER 152 37

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Wollaston, T. Vernon

1878. Testacea Atlantica or the Land and Freshwater

Shells of the Azores, Madeiras, Salvages, Canaries,

Cape Verdes, and Saint Helena, xi + 588 pages.

London: L. Reeve and Company.
Appendix 1

COMPARATIVE MATERIAL EXAMINED

In identifying and describing the fossil rails of

Ascension and St. Helena, I used the skeletal material of the following species of living and recently

extinct rails for comparison (all specimens except

those indicated are in my collections or those of

USNM): Rallus elegans, R. longirostris, R. limicola, R. aquaticus, R. pectoralis (NMV), Hypotaenidia striata, H. philippensis (AMNH), H.

torquata, H. owstoni, H. wakensis, Atlantisia

rogersi, Tricholimnas silvestris (MCZ), Dryolimnas c. cuvieri (UMMZ), Gallirallus australis,

Pardirallus maculatus (UMMZ), P. sanguinolentus,

P. nigricans, Cyanolimnas cerverai (AMNH), Rallina

eurizonoides, Canirallus oculeus (AMNH), Himantornis haematopus, Aramides cajanea, A. ypecaha,

A. saracura, Limnocorax flavirostra, Porzana pusilla, P. Carolina, P. albicollis, P. fusca, P. tabuensis, P. palmeri, Poliolimnas cinereus, P. ftaviventer,

Laterallus albigularis, L. viridis, L. leucopyrrhus,

Coturnicops noveboracensis, Sarothrura pulchra,

Porphyriops melanops, Tribonyx ventralis, T. mortierii, Amaurornis phoenicimis, Gallicrex cinerea,

Gallinula chloropus, Porphyrula martinica, Porphyrio porphyrio, Fulica atra, F. americana, Nesotrochis debooyi.

In the descriptions, the terminology of Howard

(1929) is followed.

Appendix 2

CHARACTERIZATION OF THE GENUS Atlantisia

As the genus Atlantisia has taken on an entirely

new scope, it is appropriate to discuss in what

manner its three species are similar to one another

and different from other related genera. The specific differences between the three have been indicated in the descriptions of Atlantisia elpenor

and A. podarces. The generalizations to follow

will, of course, pertain only to A. rogersi and A.

elpenor when a certain element of A. podarces is

unknown.

The bill of Atlantisia is of medium length, not

short and stout as in "crakes" nor very elongate

and slender as in "true" Rallus. It is not as wide

and heavy as the species of Hypotaenidia but is

quite similar to Dryolimnas and "Rallus" pectoralis. The nasal bar is twisted and narrow in A.

elpenor, which is characteristic of the "Rallus assemblage," but in the one specimen of A. rogersi

examined, it is broad and flat, a condition perhaps

correlated with the reduced lacrimal of that species. The cranium of Atlantisia is broader than

Rallus and somewhat narrower than Hypotaenidia.

QUADRATE.—The orbital process is narrower than

Rallus or Hypotaenidia and shorter than Gallirallus. On the internal side of the otic process is a

foramen which is an open oval in Atlantisia and

Dryolimnas, whereas in other genera it is partly

closed over with bone and the opening is on a

slant.

CORACOID.—Procoracoid process much broader

than in related genera. Fenestra large, oval, set

away from the shaft and well exposed, whereas in

related genera it is more slitlike and may lie partially under the shaft. In ventral view the head

joins the shaft to form a distinct narrow ridge,

markedly different from other genera.

SCAPULA.—Furcular articulation not squared as

in Hypotaenidia and Gallirallus nor as pointed as

in Rallus.

HUMERUS.—Shaft very slender, straight; articulations enlarged. Distal end with internal side an41
42 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

gled much farther away from line of shaft than in

other genera.

ULNA.—Shaft not greatly curved as in Gallirallus.

Internal condyle larger and more prominent than

in related genera. Impression of brachialis anticus

short but steep. External cotyla reduced.

RADIUS.—Rather stocky; distal end not as widely

expanded as in Gallirallus.

CARPOMETACARPUS.—Shorter and stouter than related forms except Gallirallus which is even stockier and more bowed. Proximal metacarpal

symphysis long and wide; intermetacarpal space

short. Pisiform process a blunt knob rather than

a more bladelike process as in other rails. Metacarpal m thin and twisted distally (especially in

A. rogersi).

PELVIS.—In dorsal view the synsacral area between the posterior ilia is convex and humplike in

Atlantisia, unlike related genera in which this area

is flat or concave. The portion of the posterior

iliac crest above the antitrochanter is reduced. In

ventral view, the preacetabular portion of the pelvis appears shorter and slightly wider in Atlantisia

and the ischia are set farther apart and flare outwards more than in related genera.

FEMUR.—The markedly straight shaft of Atlantisia is distinctive; the antero-posterior and lateralmedial curvatures seen in other genera are almost

completely straightened out. The shaft is narrow

and the distal end greatly expanded. In medial

view, the proximal end is narrower and less expanded posterior to the head than related genera.

The trochanter does not extend as far anteriorly.

Fibular groove of external condyle very deep with

higher fibular condyle.

TIBIOTARSUS.—A bone with relatively slender

shaft and expanded articulations; shaft narrower

than Gallirallus, Hypotaenidia, and Dryolimnas,

but stockier than Rallus. Distally, the internal side

of shaft flares out into a very conspicuous internal

ligamental prominence that is not as well developed in other genera. External condyle large and

bulbous. Anterior intercondylar fossa relatively

wider than related genera.

TARSOMETATARSUS.—The slender shaft with much

expanded articulations distinguishes all three species of Atlantisia from other rails on proportions

alone. Similar to Dryolimnas but shaft narrower

and articulations slightly more expanded; much

heavier than Rallus throughout; proportionately

longer and more slender than Hypotaenidia and

Gallirallus. Proximal and distal ends wider relative to shaft. Scar for hallux deep. Inner trochlea

expanded farther medially than in most other genera. Intercotylar knob low, flat and turned laterally, with cotylar surfaces more nearly in the same

plane, unlike Gallirallus, Hypotaenidia and Rallus

which have a more prominent intercotylar knob

and a depressed external cotyla. Dryolimnas, however, is similar to Atlantisia in these respects. Distal foramen wide and rounded, not partially

concealed and slitlike in anterior view as in related genera. Internal cotyla expanded well beyond

line of shaft in Atlantisia, not as expanded in other

genera. In internal view the ridge on the anterior

proximal portion of the shaft is narrower and better defined in Atlantisia.

The ratios of the hindlimb elements of Atlantisia also differ from related forms. For example,

in "Rallus" pectoralis, a species of about the same

size as A. elpenor, the tibia is shorter than that

of A. elpenor while the femur is longer.

In short, Atlantisia is intermediate in most respects between the generalized, heavy Hypotaenidia

group and the slender, delicate, specialized Rallus.

With Dryolimnas and "Rallus" pectoralis it forms

a "pio-Rallus" group. Atlantisia differs from the

rest of "pro-Rallus" (aside from flightless features,

which are not considered of generic value) mainly

in qualitative details of the coracoid and pelvis,

in the straight shaft of the femur, and in the proportions of the hindlimb elements all of which

have narrower shafts but wider articulations in

Atlantisia.
NUMBER 152 43

a

\- 1 c

PLATE 1 Skulls of the three species of Atlantisia: a, A. rogersi, female, USNM 319151,

Inaccessible Island, Tristan da Cunha group, b, A. elpenor, Ascension Island. A composite

drawing from USNM 170131, 170087, and 170088. Quadrate, pterygoid, lacrimal, and posterior

portion of jugal bar lacking, c, A. podarces, USNM 17:5890, St. Helena. Cranium only, dotted

lines indicate hypothetical bill shape. The drawing is actually of the right side of the

specimen but the negative has been reversed to facilitate comparison. Scale=10 mm.
44 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

a

PLATE 2.—Pelvis and skull elements of Atlantisia elpenor: a, pelvis, USNM 170131, dorsal

view; b, same, right lateral view; c, mandible, USNM 170131, dorsal view; d, same, left lateral

view; e, lateral (upper) and medial (lower) views of the lacrimals of A. elpenor, USNM 170107

(left), and A. rogersi USNM 319151 (right). a-d, Twice natural size; e, scale=5 mm.
NUMBER 152 45

a

PLATE 3.—Wing and pectoral girdle elements of Atlantisia elpenor, USNM 170129: a, left

humerus, anconal view; b, same, palmar view; c, left radius (anconal) and left ulna (palmar) ;

d, left carpometacarpus, internal view; e, same, external view; /, left coracoid, external view;

g, same, internal view; h, furcula; i, left scapula, ventral view. All twice natural size.
46

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

d

PLATE 4 Sterna of Atlantisia. A. elpenor, composite drawing from USNM 170059 and 170129:

a, ventral view; b, left lateral view. A rogersi, USNM 319151: c, ventral view; d, left lateral

view. Scale=5 mm.
NUMBER 152 47

PLATE 5.—Hindlimb elements of Atlantisia elpenor: a, left tibia, USNM 169929, anterior view,

and right fibula, USNM 170129, medial view; b,

same, fibula in lateral view, tibia in medial view;

c, left femur, USNM 170129, anterior view; d,

same, posterior view; e, left tarsus, holotype,

USNM 170129, anterior view; /, same, posterior

view; g, same, medial view. All twice natural size.
48 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

PLATE 6.—Skeletal elements of Atlantisia podarces: a, middle toe with

claw; b, right tibia, medial view; c, head of fibula (internal view) and

right tibia (anterior view) ; d, right coracoid (lacking sternal end),

external view; e, same, internal view; /, right humerus (lacking distal

end), anconal view; g, same, palmar view; h, right ulna, anconal view

(MCZ 7197); i, same, palmar view; ;', left carpometacarpus and digit n

phalanx 1, external view; k, same, internal view. All figures natural size

from Prosperous Bay, St. Helena and all but h and i from USNM 175878.

a

1

i

p 1I

J
NUMBER 152 49

a

PLATE 7 Skull elements of Porzana astrictocarpus, holotype, USNM 175893, Prosperous Bay,

St. Helena: a, lateral view of skull and mandible (braincase crushed dorsoventrally); b, ventral

view of skull; c, dorsal view of mandible; d, right laciimal; external view above, internal

view below. Scale=5 mm. All figures except d twice natural size.
50 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

PLATE 8.—Pectoral girdle and wing elements of

Porzana astrictocarpus: a, right scapula, ventral view;

b, left coracoid, external view, with a portion of the

left clavicle; c, same, internal view; d, left humerus,

anconal view; e, same, palmar view; /, left radius

(anconal view) and left ulna (palmar view); g, left

carpometacarpus, external view; h, same, internal

view, with ulnare and phalanges 1 and 2 of digit u;

i, right carpometacarpus, internal view, USNM 175293,

Dry Gut, St. Helena. Scale=approx. 5 mm. All but i

are from the holotype, USNM 175893, and are twice

natural size.
NUMBER 152 51

PLATE 9.—Pelvis and hindlimb elements of Porzana aslrictocarpus, holotype, USNM 175893:

a, pelvis, dorsal view; b, same, right lateral view; c, right femur, anterior view; d, same, posterior

view; e, right fibula (external view) and right tibia (anterior view); /, right tibia, medial

view; g, right tarsus, anterior view; h, same, posterior view; i, same, medial view. All are twice

natural size.
52 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

PLATE 10.—Leg and wing elements of the three species of Atlantisia compared: The elements

shown (left to right) are humans, ulna, carpometacarpus, femur, tibia, and tarsus. In each

group, A. podarces is on the left, A. elpenor in the middle and A. rogersi on the right.
NUMBER 152 53

PLATE 11 Skeletal elements of three species of Porzana compared: The elements shown (left

to right, top to bottom) are mandible, skull, humerus, ulna, carpometacarpus, femur, pelvis,

tibia, tarsus. In each group, P. palmeri is on the left, P. astrictocarpus is in the middle, and

P. pusilla is on the right.

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