Because of the present distribution of alcids and alcid fossils, it is
generally suggested that alcids originated in the Pacific Basin north of the
equator. However, specimens from fossil-bearing strata along North American
coasts presently under study by paleontologists, along with a recent but
doubtful description from Austria, may modify our views of the former
distribution of this family of seabirds.397, 404a Although thousands
of specimens are now in museum files, we must be aware that any interpretation
based upon fragmentary fossil evidence is bound to be at least partially
speculative.
Since the bones of most birds are lightly constructed, it is
often implied in the literature that they are rarely fossilized, but fossil
birds are more abundant than is commonly portrayed. Some interesting remains of
alcids have been identified and a number of extinct species have been described.
It should be kept in mind, however, that the species of the paleontologist is
not defined in the same way as are living species. Living species, or biological
species, are defined by comparing reproductively-isolated populations, while
genetic relationships of fossil species by necessity must be implied by
comparing structural variations of skeletal elements.
Although the
skeletal structure of modern species is fairly uniform,and that the range of
variation for qualitative characters is reasonably consistent for recent and
fossil birds, it is still possible that variations seen in fossils may represent
polymorphic conditions within what was once a single reproductively-isolated
species. However, there is no way to determine the reproductive and behavioral
patterns of long-extinct species: from the structure of the bones of the feet
and wings, we can only make intelligent guesses about their ability to swim,
walk and fly. Similarly, bill and skull structure gives some idea of feeding
habits, while fossil plant remains found in the same formations give us clues as
to the climate that prevailed at the time.
In the deposits of Sunset Bay, Oregon, and White River,
Utah, two different genera have been described: Hydrotherikornis oregonus (now
considered to be a petrel) and Presbyornis avus and Presbyornis proavitus
(formerly Nautilornis, auk-like species between the Ancient Murrelet and the
Pigeon Guillemot in size). These three species have been placed in the subfamily
Nautilornithinae and have been considered to be ancestors of the
alcids.349b Because their wings were longer than modern alcids, they
were probably excellent fliers as well as good swimmers, but less efficient at
using their wings in diving than the modern auks. It is also possible that these
birds lived in a subtropical climate similar to that now found in southern
Japan, southern California, Florida, or the Mediterranean, for fossil vegetation
from the same deposits includes willow, birches, and firs along with palms and
figs. It is also interesting to note that skeletal remains of the recently
extinct Great Auk are found as far south as Florida. Today, although a few
species range into this type of warm climate, most alcids prefer cooler
waters.
In 1987, Austrian upper Oligocene strata produced the
oldest known European fossil assigned as an alcid. This find was classified as a
new genus and species Petralaca austriaca , and listed as a new subfamily
Petralcinae. 397 This discription, if valid, may indicate that alcids
were present in the Atlantic and Pacific at about the same time in geological
history which is contrary to the general opinion that alcids originated in the
Pacific. 616 However, some authorities consider the assignment of the specimen
to alcidae to be erroneous.131
Miocepphus mcclungi was a heavy-boned guillemot
identified from deposits in Maryland. Miocepphus was almost the size of modern
guillemots but with some features similar to the modern genus Brachyramphus to
which the Marbled and Kittlitz's Murrelets belong. 460c Miocene
deposits in California reveal a species similar to the Rhinoceros Auklet,
Cerorhinca dubia. 339 Hildegarde Howard, described a fossil species
of flightless auk of the subfamily Mancallinae, a group also represented by
several fossil species in Pliocene deposits. 278 The evidence for the
existence of this new species, Praemancalla wetmorei, is based upon an almost
complete humerus bone and a few other parts of wing bones. Dr. Howard has also
described a Miocene species resembling a heavily built Common Murre. This
species, Uria brodkorbi, is represented by a skull and partial skeleton
impressions in Miocene Sisquoc Formation from Lompoc, California. 279
Another, probably a small auklet, Aethia rossmoori, is described from the late
Miocene of the Monterey Formation, in California. 280
Early Pliocene deposits in California have also
yielded two species, a murre,Uria paleohesperis ; and a guillemot, Cepphus
olsoni the oldest known fossil of the genus. The genus Praemancalla is also
known from Pliocene fossil beds of Orange County, California. The species,
Praemancalla lagunensis, is represented by wing bone fragments including a
complete humerus thus providing comparative material for the Miocene species.
Apparently, both were flightless auks.
Constituting a side-branch or ŗsister
group˛to alcids are several species of Mancallinae found in Pliocene deposits:
(1) Mancalla californiensis, a large flightless species from the Los Angeles
area; (2) Mancalla diegensis a slightly smaller bird from the San Diego area,
and also recorded in Pleistocene deposits in northern California; (3)
Overlapping in size with M. diegensis is Mancalla milleri from southern
California; (4) Mancalla emlongi was described by S. Olson in 1981 from the San
Diego Formation.460c (5) Mancalla cedrosensis is from Cedros Island,
Mexico; Brachyramphus pliocenum, a murrelet, is described from the San Diego
deposits.394 In 1990, paleontologist Robert Chandler, described
several new species from the San Diego Formation.131 (1)
Brachyramphus dunkeli is named after its collector and is a larger bird than are
B. pliocenum and the two living species of the genus. (Marbled and Kittlitzšs
Murrelets). (2) Synthliboramphus rineyi is a small murrelet. (3) Reašs Puffin, a
new species also described by Chandler, Cerorhinca reai, is related to the
Rhinoceros Auklet. (4) Two other unnamed species of Cerorhinca are listed but
are not complete enough to positively assign species names although one was
indefinitely designated C. minor. Ptychoramphus tenuis described by Miller and
Bowman in 1958, is also found in the San Diego Pliocene deposits and is a
smaller bird than the living Cassinšs Auklet. By comparison, the San Diego
Formation has more species of alcids than are presently ranging in southern
California.131
Pliocene deposits of North Carolina and
Florida include two fossil species of Great Auk, Pinguinis alfrednewtoni, named
after a British ornithologist who had special interest in Great Auks and who
visited a number of breeding places, plus a questionable species called
Australca grandis.460 c A species of Uria is also described from the
early Pliocene of North Carolina, Uria antiqua. 280
Pliocene
deposits in Italy have revealed alcid fossils. Here, two species, probably of
the genera Australca or Alca are described from limited skeletal parts. Both of
these resemble the Common Murre (Uria ). 280
These include: (1) Mancalla diegensis, from Humbolt
County California; (2) Uria affinis, found near Bangor, Maine, represented by a
complete humerus larger than that of living murres; and (3) two Common Murre
fossils from California, one from the Los Angeles area, the other from Mussel
Rock in San Mateo County. (4) Pinguinus (Alca) impennis is identified in
Atlantic Pleistocene deposits.
Additional alcid fossil material has been
collected but has yet to be studied and described. Undoubtedly, any new
information will be helpful in determining more precisely the distribution of
alcids in the past. It is imperative, however, that all fossil remains be
studied in the context of entire fossil communities and carefully compared with
whole series of modern skeletal elements before accurate designations can be
made. There may be considerable morphological variations from one geographical
location to another.
Miklos Udvardy, who has studied the zoogeography of
auk species, suggests that major climatic changes in the past have greatly
influenced their present distribution. 616 For example, species such
as the Japanese Murrelet in the western Pacific and the Xantus' and Craveris'
Murrelets of Baja California, may have once had ranges that connected across the
Aleutians. Because of severe climate during episodes of glaciation, present
populations are now limited to the southern extremities of the former possible
range. Further evidence which supports this suggestion is the fact that some
species of seals and vegetation match the disjunct population of these
auks.
Summarizing Table of Fossil Auks
(A) = Atlantic, (P) =
Pacific
Pleistocene: Uria aalge (P)
Uria affinis ( A)
Pinguinus (Alca
) impennis (A)
Mancalla diegensis (P)
Late Pliocene: Alca ( or Austalca) ?
ausonia (A)
Mancalla diegensis (P)
Mancalla milleri (P)
Mancalla
emlongi (P)
Brachyramphus pliocenum (P)
Brachyramphus dunkeli
(P)
Synthliboramphus rineyi (P)
Ptychoramphus tenuis (P)
Cerorhinca
reai (P)
Cerorhinca minor ? (P)
Cerorhinca sp. ?
Early Pliocene:
Australca antiquus (A) ?= Australca grandis (A) Uria paleohesperis (P)
Uria
antiqua (A)
Cepphus olsoni (P)
Mancalla californiensis (P)
Mancalla
cedrosensis (P)
Cerorhinca minor (P)
Praemancalla lagunensis
(P)
Praemancalla wetmorei (P)
Pinguinus (Alca ) alfrednewtoni
(A)
Miocene:
Aethia rossmoori (P) ?
Alcodes ulnulus
(P)
Cepphus olsoni (P)
Uria brodkorbi (P)
Cerorhinca dubia (P)
Miocepphus mcclungi (A)
Oligocene: Petralcinae Petralca austriaca (A)
(doubtful genus and species 131)
Eocene: Nautilornithinae
Hydrotherikornis oregonus (P)
( Now classified as a petrel
131)
Presbyornis avus (P)
Presbyornis proavitus (P)
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References