First fossil record of a finfoot (Aves: Heliornithidae) and its biogeographical significance

5 Pages·2003·2.8 MB·

by  Storrs L Olson

PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
116(3):732-736. 2003.
First fossil record of a finfoot (Aves: Heliornithidae) and its
biogeographical significance
Storrs L. Olson
Division of Birds, National Museum of Natural History, Smithsonian Institution,
Washington, D.C. 20560, U.S.A., e-mail: [email protected]
—
Abstract. The distal end of a humerus from the Lee Creek Mine in North
Carolina is identified with the modern Neotropical species as Heliornis aff.
fulica and provides the first fossil record for the family Heliornithidae. The
fossil was determined to come from the Middle Miocene (14 Ma) Pungo River
Formation based on sedimentary, preservational, and other lines of evidence.
This in turn implies that Heliornis did not spread into South America until
Ma
after the isthmian land connection about 3 and that the interchange of
Heliornithidae between the Old and New World probably took place through
the Northern Hemisphere in the Paleogene.
The finfoots or sungrebes (Heliornithi- the "higher" orders of arboreal land birds
dae) comprise 3 species, each in a mono- (Olson 1985). It differs from all of these in
typic genus, that are placed in the tradition- the very rounded, hemispherical condylus
al avian order Gruiformes. On the basis of ventralis (ulnar condyle), which contrasts
both morphology and molecular data, the markedly with the narrow, transversely
family is probably most closely related to ovoid, and often proximally flattened con-
rails, Rallidae (Houde 1994, Livezey 1998). dyle in the traditional orders Coliiformes,
The species are sedentary, swimming and Trogoniformes, Coraciiformes, Piciformes,
diving birds of forested streams in the trop- and Passeriformes. Another highly distinc-
ics of the New World, Africa, and southeast tive character is the extension of the epi-
Asia. Hitherto, there has been no fossil re- condylus ventralis distally well past the
cord of the family (Brodkorb 1967, Houde margins of the distal condyles. These two
1994, Tommy Tyrberg, Kimstadt, Sweden, features (Fig. 1) in combination with the
pers. comm.). This has changed with the overall size and shape are diagnostic of the
discovery of the distal end of a humerus in
Heliornithidae.
spoil piles of the Lee Creek phosphate mine
near Aurora, North Carolina, from which
tens of thousands of fossil bird bones had Genus Heliornis Bonnaterre, 1791
been recovered previously (Olson and Ras-
mussen 2001).
There is little in the way of qualitative
Systematics differences in the distal half of the humerus
to distinguish the three genera of Heliorni-
Class Aves
thidae. Podica and Heliopais differ from
Order Gruiformes
Heliornis and the fossil in their much larger
Family Heliornithidae
size, so that on size and geographical
The fossil humerus is characterized by its grounds it is more reasonable to assign the
short, curved overall shape, which at first fossil to the type-genus of the family, He-
suggests a medium-sized species of one of liornis.
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Fig. 1. Left humeri of Heliornis (top row anconal view; bottom row palmar view): A, fossil Helioniis aff.
fulica from Lee Creek Mine, North Carolina; B, C, modern Heliornisfulica (UF 38828 = PB 35036; USNM
321493; UF 33412 = PB 29333). The distally projecting epicondylus ventralis (long arrow) and the very
rounded, hemispherical condylus ventralis (short arrow) are diagnostic features of the Heliornithidae.
734 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
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Table 1. Measurements (mm) of the humerus of erably in the modern series. Qualitatively,
modern Heliornis fulica (HeHornithidae) compared the only apparent differences are the some-
with fossil humerus of Heliornis aff. fulica (USNM what more curved shaft, the relatively larg-
5 8297) from the Miocene of North Carolina.
1
er condylus ventralis, and the wider sulcus
Heliornisfulica musculo humerotricipitalis in the fossil.
Rang(eN(=meai3n)) SD Heliornifsossaiflf. fulica These differences may indicate slight dif-
ferences in flight capability, but given the
Distal width 6.2-7.0 (6.8) 0.24 6.9
Shaft width 2.4-3.2(2.8)0.19 3.2 time disparity they are very minor. There is
Shaft depth 2.4-2.8(2.6)0.12 2.9 nothing in this single fossil to suggest that
it represents a divergence from the lineage
leading to the modern species Heliornisfu-
lica. This perception might be altered if
Heliornis aff fulica (Boddaert, 1783)
. more of the skeleton were available.
—
Referred specimen. Distal half of left
humerus. National Museum of Natural His-
Discussion
USNM
tory, Smithsonian Institution,
518297, collected 13 June 2001 by Geoff The Heliornithidae are among the classic
Keel. examples pantropical families of birds (Fig.
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Locality. Lee Creek Mine, south side of 2), such as barbels (Capitonidae) and tro-
Pamlico River, near Aurora, Beaufort gons (Trogonidae), which likewise occur in
County, North Carolina (35°23'22"N, the Old and New World tropics, but not in
76°47'06"W). Australasia. This pattern invites the ques-
—
Horizon. Pungo River Formation, Mid- tion of whether their distribution is the re-
Ma
dle Miocene; Langhian stage, ca. 14 sult of vicariant events or dispersal.
(Gibson 1983). Fossil birds at the Lee Modern Heliornis fulica extends practi-
Creek Mine come from deposits of two cally throughout the Neotropics from Mex-
—
ages separated by an unconformity the ico to northern Argentina. The fossil record
Middle Miocene Pungo River Fm and the from North Carolina is more than 2600 air
Lower Pliocene Yorktown Fm (Olson and line km NE of the nearest occurrence of
Rasmussen 2001). Assignment of the pre- Heliornis in Veracruz, Mexico. The speci-
sent fossil is based on several lines of evi- men comes from deposits about 14 Ma,
dence. It was recovered from a spoil pile whereas a land connection was established
that was topped by sediments of the Pungo between North and South America only
River Fm; the preservation is excellent, the about 3 Ma, with mammalian overland dis-
bone having a hard, shiny surface, unlike persal having taken place in both directions
the etched appearance of many of the bones before about 2.5-2.8 Ma (Marshall 1985).
from the Yorktown Fm; blackish phosphatic Finfoots, being weak fliers and with very
sand characteristic of the Pungo River Fm specific aquatic habitat requirements, are al-
was adherent to the fossil; and no strictly most certainly incapable of dispersing over
tropical elements occur in the Yorktown Fm an oceanic barrier. Thus, the evidence now
but are known from the Pungo River and at hand suggests that Heliornis fulica must
equivalent formations. have spread into South America from North
—
Comparisons. In size, the fossil falls America after the isthmian land connection
within the range of modern Heliornisfulica formed, and perhaps considerably after that,
in two measurements, though near the high given that it has no recognized subspecies
end, and is very slightly larger in shaft (Hellmayr and Conover 1942).
depth (Table 1). Although the shaft of Heliornis differs from other finfoots in
USNM
518297 is thus generally somewhat having altricial young that are carried in ax-
more robust, this character varies consid- illary marsupia (Houde 1994), so that it is
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Fig. 2. Modern distribution of the three species of Heliornithidae (soHd) and the only fossil record (arrow).
Map modified from Fisher and Peterson (1964).
presumably the most derived of the three and Swisher 1995). Thus, fossils of Helior-
species. Houde (1994) found Heliornis to nithidae might be anticipated in Paleogene
be closer genetically to the Asian genus He- deposits of the northern continents.
liopais, than to the African genus Podica,
DNA
although the quality of the of Helio- Acknowledgments
pais may have been equivocal. He also
found that the degree of genetic divergence I am most grateful to Geoff Keel for col-
between Heliornis and the African genus lecting and donating the specimen, and to
Podica was too small to be compatible with Mark Florence and David Bohaska, Dept.
a trans-Atlantic origin of the former and of Paleobiology, National Museum of Nat-
subsequent separation via sea-floor spread- ural History, Smithsonian Institution
ing, which would have necessitated a com- (USNM), for processing the specimen and
mon distribution across what is now Africa associated information. Photographs are by
and South America well back into the Cre- John Steiner, Smithsonian Photographic
taceous (Smith et al. 1994). Services. Production of the figures was by
Assuming finfoots to require tropical en- Brian Schmidt, Division of Birds, Smith-
vironments and to be incapable of crossing sonian Institution. I thank Helen James for
marine water barriers, interchange of fin- processing statistics and Scott Wing for cer-
foots between the Old and New World must tain bibliographical references. For lending
have taken place early in the Tertiary across specimens of comparative material I am
the Northern Hemisphere, because Helior- grateful to Mark Robbins, University of
nis was already in North America by the Kansas Museum of Natural History, Lawr-
W
Middle Miocene. There is abundant floral ence (KU); J. V. Remsen and S. Cardiff,
and faunal evidence for interchange be- Museum of Natural Science, Louisiana
tween North America and both Europe and State University, Baton Rouge (LSU); Carla
Asia in the Eocene (Manchester 1999) and Cicero, Museum of Vertebrate Zoology,
in particular for invasions of mammals University of California, Berkeley (MVZ);
from Asia in the late Eocene (Woodburne David W. Steadman, Florida Museum of
736 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
Natural History, University of Florida, charact—ers, with an emphasis on the rails (Ral-
Gainesville (UF); and Kristof Zyskowski, lidae). Philosophical Transactions of the Roy-
Peabody Museum of Natural History, Yale al Society B 353:2077-2151.
Manchester, S. R. 1999. Biogeographical relationships
University, New Haven (YPM). I thank Da- of North American Tertiary floras.—Annals of
vid W. Steadman and Gareth Dyke for com- the Missouri Botanical Garden 86:472-522.
ments on the manuscript. Marshall, L. G. 1985. Geochronology and land-mam-
mal biochronology of the transamerican faunal
interchange. Pp. 49-85 in F G. Stehli and S. D.
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