[PaleoMammalogy • 2015]
Albicetus oxymycterus • A New Generic Name and Redescription of a Basal Physeteroid (Mammalia, Cetacea) from the Miocene of California, and the Evolution of Body Size in Sperm Whales
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A pod of Albicetus oxymycterus taking it easy out on the ocean.
Image: A. Boersma || DOI: 10.1371/journal.pone.0135551
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Abstract
Living sperm whales are represented by only three species (Physeter macrocephalus, Kogia breviceps and Kogia sima),
but their fossil record provides evidence of an ecologically diverse
array of different forms, including morphologies and body sizes without
analog among living physeteroids. Here we provide a redescription of Ontocetus oxymycterus,
a large but incomplete fossil sperm whale specimen from the middle
Miocene Monterey Formation of California, described by Remington Kellogg
in 1925. The type specimen consists of a partial rostrum, both
mandibles, an isolated upper rostrum fragment, and incomplete tooth
fragments. Although incomplete, these remains exhibit characteristics
that, when combined, set it apart morphologically from all other known
physeteroids (e.g., a closed mesorostral groove, and the retention of
enameled tooth crowns). Kellogg originally placed this species in the
genus Ontocetus, a enigmatic tooth taxon reported from the 19th century, based on similarities between the type specimen Ontocetus emmonsi and the conspicuously large lower dentition of Ontocetus oxymycterus.
However, the type of the genus Ontocetus is
now known to represent a walrus tusk (belonging to fossil Odobenidae)
instead of a cetacean tooth. Thus, we assign this species to the new
genus Albicetus, creating the new combination of Albicetus oxymycterus, gen. nov.
We provide new morphological observations of the type specimen,
including a 3D model. We also calculate a total length of approximately 6
m in life, using cranial proxies of body size for physeteroids. Lastly,
a phylogenetic analysis of Albicetus oxymycterus with other
fossil and living Physeteroidea resolves its position as a stem
physeteroid, implying that large body size and robust dentition in
physeteroids evolved multiple times and in distantly related lineages.
Systematic paleontology
CETACEA, Brisson
ODONTOCETI, Flower, sensu Fordyce and Muizon
PAN-PHYSETEROIDEA, Velez-Juarbe et al.
PHYSETEROIDEA, Gray, sensu Velez-Juarbe et al.
Albicetus oxymycterus, new combination,
urn:lsid:zoobank.org:act:0A979799-2E74-4C2E-9E23-8940A036AE18,
Type and only known species: Albicetus, nov. gen., oxymycterus
Etymology: Combining the Latin words albus (white) and cetus (whale). The name pays tribute to H. Melville’s classic American novel Moby-Dick;
or, The Whale. In the novel, Melville refers to Moby-Dick as “the White
Whale”, a creature of “unwonted magnitude” with a “remarkable hue” and
“deformed lower jaw”. These traits are coincidentally similar to the
type specimen of Albicetus, a white fossil sperm whale whose jaws have
been displaced due to diagenetic processes, providing apt inspiration
for the connection to the famous literary whale.
Albicetus oxymycterus, new combination (Figs 2 and 5–10, Tables 1 and 2)
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| Lead author A. Boersma with the partial whale skull fossil.
Image: Jame di Loreto, Smithsonian || smithsonianmag
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Holotype: USNM 10923, the incomplete extremity of the rostrum and mandibles, with 10 or 11 roots or portions of teeth in situ
in each mandible, several incomplete teeth fragments found loose in the
matrix, and a separate piece of the upper rostrum. Archival typewritten
notes at USNM state that the specimen was first observed by Charles O.
Roe (1867–1923) when he was a boy, and was collected by him some thirty
years later in 1909, implying an initial discovery as early as 1879.
These notes are consistent with Kellogg [28]’s report about the type
specimen’s discovery around 1884, and it being subsequently moved to
Roe’s home in 1909. The specimen was received by USNM on 16 February
1924 from Roe’s wife, after his death in 1923 [51].
Etymology: According to Kellogg, oxymycterus derives from the Greek words oxy (sharp) and mycter (nose).
Type locality: The type specimen was collected approximately 3.5
meters above the high tide line of a sea cliff approximately 20 m in
height, north or near the original Santa Barbara Lighthouse, Santa
Barbara, Santa Barbara County, California, U.S.A. (N 34° 20'12", W 119°
43'20" according to Kellogg) [28]. Archival typewritten notes at USNM
indicate that the “exact locality is between the [original Santa
Barbara] lighthouse and Hope Ranch,” and that “[other] parts of the
skeleton are still in the bank.” Hope Ranch today is a residential
community of approximately 1,600 acres, but in the late 19th century it
was a large private property until the Southern Pacific Railroad
purchased it for development in January 1876. Actual development on the
terrain did not begin until 1923. It was likely during this period of
time between purchase and development that C. A. Roe collected the type
specimen (1879–1909), since the property lines of Hope Ranch abutted the
original Santa Barbara Lighthouse.
The original Santa Barbara Lighthouse, however, was destroyed in an
earthquake on 29 June 1929, and Kellogg’s published coordinates
correspond to a location about 5 km directly south of the original
lighthouse, offshore in Santa Barbara Bay. The published locality
account by Kellogg corresponds today to sea cliffs located near the
property of the current lighthouse, which is 100 m northeast of the
original lighthouse, at the following coordinates (N 34° 23' 44", W 119°
43' 23"). We argue that this general vicinity, within less than a 100 m
radius, likely represents the type locality of Albicetus oxymycterus (Fig 1).
Formation: Kellogg [28] described the stratigraphic provenance of
the type specimen of Albicetus as a unit of bituminous dolomite in the
sea cliffs of Santa Barbara County, likely belonging the Monterey
Formation. This description is consistent with Minor et al.’s geologic
mapping of the Santa Barbara Coastal Plain, which at the reported
locality shows the underlying lowest three subunits of the marine
siliceous and calcareous mudstone and shale belonging to the Monterey
Formation. These marine rocks are mapped as the lower calcareous unit of
the Monterey Formation. Overlying marine terrace deposits of
Pleistocene age in this area do not match the lithology of the matrix
with USNM 10923.
Age: Minor et al. summarized biostratigraphic findings for
lower calcareous unit outcrops of the Monterey Formation in the Santa
Barbara Coastal Plain. Benthic foraminiferal assemblages point to
Relizian to Saucesian stages, and calcareous nannofossil zones CN1-CN5,
with ages generally tending to be younger in the northwestern
localities, and older heading to the southeast. For Santa Barbara Point,
a locality less than 1 km due east of original Santa Barbara
Lighthouse, Minor et al. reported benthic foraminiferal
assemblages consistent with Relizian and Luisian Stages of Kleinpell and
calcareous nannofossils of lower middle Miocene zone CN4. These data
constrain the age of the type specimen of Albicetus to the early middle Miocene (~16–14 Ma), or Langhian.
Conclusions
We provided new information about an enigmatic fossil sperm whale from the Miocene of California, Albicetus oxymycterus,
for which we provided a new genus name because of taxonomic priority of
its original name with a fossil walrus. Our redescription of the type
specimen of Albicetus provides new morphological details, along
with revisions to the stratigraphy and locality data, as can best be
ascertained given the available historical information. We provided a
phylogenetic analysis to determine the relationship of Albicetus to other fossil sperm whales, along with body size estimates. Our results indicate that Albicetus was
a large, stem physeteroid with a seemingly unique combination of
diagnostic features observed in no other living or fossil physeteroid.
Alexandra T. Boersma and Nicholas D. Pyenson. 2015. Albicetus oxymycterus,
A New Generic Name and Redescription of a Basal Physeteroid (Mammalia,
Cetacea) from the Miocene of California, and the Evolution of Body Size
in Sperm Whales.
PLoS ONE. DOI: 10.1371/journal.pone.0135551
PLoS ONE. DOI: 10.1371/journal.pone.0135551
A Moby-Dick emerges from the Smithsonian collections and digitized
http://po.st/yw6eCu via @SmithsonianMag @NMNH
http://po.st/yw6eCu via @SmithsonianMag @NMNH
‘White whale’ is a ghost of sperm whales’ past
