Early Miocene whales from Awamoa Beach, North Otago
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Early Miocene (~23-16 Ma) rock units—the Mount Harris Formation (Otaian – Altonian) and Gee Greensand (basal Otaian)—at Awamoa Beach, North Otago, preserve fossils of extinct Cetacea. The Early Miocene is a significant time in cetacean history as the interval where some archaic whales declined and the bulk of modern cetaceans began to dominate the oceans. Awamoa Beach—historically important as the locality from which the first New Zealand fossil cetacean was described—became accessible as a fossil site in 1999. Thus far, it has produced a diverse assemblage of Early Miocene whale fossils which expands the patchy global record of Early Miocene cetacean localities.
This project records four fossil cetacean skulls and some post-cranial material recovered from Awamoa Beach within the last decade. Fieldwork as part of this thesis was precluded by a thick layer of shingle that has overlain Awamoa Beach units since mid 2008, so that research concentrated on fossils already collected from Awamoa Beach (curated in the Geology Museum, University of Otago); some are documented here. I used physical and chemical preparation methods to remove matrix from some of the fossils. Subsequently, I have identified four odontocetes and discussed their phylogenetic relationships with previously documented odontocetes.
Among the recovered cetacean fossils of Awamoa Beach, one partial skull and its associated post-cranial material, OU22466, most likely represents the short-jawed shark-toothed dolphin, Prosqualodon cf. davidis, hitherto known only from Australia. This is the first firm report of a Prosqualodon skull from New Zealand.
Specimen OU22672 likely represents an early member of Delphinoidea. The interconnected sinus fossae of the basicranium and pronounced asymmetry of the skull suggest that it is a specialized odontocete that is phylogenetically related closely to delphinids. Poor preservation precludes firm taxonomic placement. The skull was found as float on Awamoa Beach so an experiment—one of the first of its kind from New Zealand—was designed and conducted to liberate foraminifera from the matrix of the skull to date the specimen. Although the experiment did not produce diagnostic foraminifera that could date the skull, it identified procedures for liberating foraminifera that could prove useful to future studies.
Another important skull is OU22670, a new genus and species of the Pomatodelphininae which is the sister taxon of extant Platanista, the river dolphin of the Indian subcontinent. The results of a cladistic analysis suggest that OU22670 is the sister taxon of Prepomatodelphis from the late Early Miocene. Thus, OU22670 extends the global fossil record of Platanistidae to earlier in the Miocene and suggests that Platanistidae did not originate in the northern Atlantic Ocean as previously believed. Additionally, the highly derived characters of OU22670 indicate that it is more specialized than Prepomatodelphis.
OU22465 is an enigmatic specimen that has a ‚rostral bulge‛, a feature not documented from any other odontocete taxon. This feature is somewhat similar to the large maxillary crests of Squalodelphinidae and Platanistidae. This incomplete skull is documented as Odontoceti: Platanistoidea incertae sedis.
The findings of this project suggest that Awamoa Beach could be regarded as one of the globally few significant Early Miocene cetacean fossil localities.
This project records four fossil cetacean skulls and some post-cranial material recovered from Awamoa Beach within the last decade. Fieldwork as part of this thesis was precluded by a thick layer of shingle that has overlain Awamoa Beach units since mid 2008, so that research concentrated on fossils already collected from Awamoa Beach (curated in the Geology Museum, University of Otago); some are documented here. I used physical and chemical preparation methods to remove matrix from some of the fossils. Subsequently, I have identified four odontocetes and discussed their phylogenetic relationships with previously documented odontocetes.
Among the recovered cetacean fossils of Awamoa Beach, one partial skull and its associated post-cranial material, OU22466, most likely represents the short-jawed shark-toothed dolphin, Prosqualodon cf. davidis, hitherto known only from Australia. This is the first firm report of a Prosqualodon skull from New Zealand.
Specimen OU22672 likely represents an early member of Delphinoidea. The interconnected sinus fossae of the basicranium and pronounced asymmetry of the skull suggest that it is a specialized odontocete that is phylogenetically related closely to delphinids. Poor preservation precludes firm taxonomic placement. The skull was found as float on Awamoa Beach so an experiment—one of the first of its kind from New Zealand—was designed and conducted to liberate foraminifera from the matrix of the skull to date the specimen. Although the experiment did not produce diagnostic foraminifera that could date the skull, it identified procedures for liberating foraminifera that could prove useful to future studies.
Another important skull is OU22670, a new genus and species of the Pomatodelphininae which is the sister taxon of extant Platanista, the river dolphin of the Indian subcontinent. The results of a cladistic analysis suggest that OU22670 is the sister taxon of Prepomatodelphis from the late Early Miocene. Thus, OU22670 extends the global fossil record of Platanistidae to earlier in the Miocene and suggests that Platanistidae did not originate in the northern Atlantic Ocean as previously believed. Additionally, the highly derived characters of OU22670 indicate that it is more specialized than Prepomatodelphis.
OU22465 is an enigmatic specimen that has a ‚rostral bulge‛, a feature not documented from any other odontocete taxon. This feature is somewhat similar to the large maxillary crests of Squalodelphinidae and Platanistidae. This incomplete skull is documented as Odontoceti: Platanistoidea incertae sedis.
The findings of this project suggest that Awamoa Beach could be regarded as one of the globally few significant Early Miocene cetacean fossil localities.
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xxvi, 211 leaves : col. ill ; 30 cm. + 1 CD-ROM (4 3/4 in.)
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2010Ortega
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Ortega, Megan Emily., “Early Miocene whales from Awamoa Beach, North Otago,” Otago Geology Theses, accessed December 7, 2024, https://theses.otagogeology.org.nz/items/show/524.