1998/12/22 by Sunil Bajpai, Philip D. Gingerich · 5 citations
Environmental Science · Earth and Planetary Sciences · Social Sciences · #Marine animal studies overview #Geology and Paleoclimatology Research #Pleistocene-Era Hominins and Archaeology #Cetacea #Extant taxon #Cenozoic #Paleontology #Fauna #Range (aeronautics) #Biology #Geology #Zoology #Ecology #Evolutionary biology #Structural basin
paper · doi:10.1073/pnas.95.26.15464
openalex publication_date 1998/12/22 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/14
Himalayacetus subathuensis is a new pakicetid archaeocete from the Subathu Formation of northern India. The type dentary has a small mandibular canal indicating a lack of auditory specializations seen in more advanced cetaceans, and it has Pakicetus-like molar teeth suggesting that it fed on fish. Himalayacetus is significant because it is the oldest archaeocete known and because it was found in marine strata associated with a marine fauna. Himalayacetus extends the fossil record of whales about 3.5 million years back in geological time, to the middle part of the early Eocene [ approximately 53.5 million years ago (Ma)]. Oxygen in the tooth-enamel phosphate has an isotopic composition intermediate between values reported for freshwater and marine archaeocetes, indicating that Himalayacetus probably spent some time in both environments. When the temporal range of Archaeoceti is calibrated radiometrically, comparison of likelihoods constrains the time of origin of Archaeoceti and hence Cetacea to about 54-55 Ma (beginning of the Eocene), whereas their divergence from extant Artiodactyla may have been as early as 64-65 Ma (beginning of the Cenozoic).